JPH0677177A - Dry etching method and dry etching apparatus - Google Patents

Abstract

(57) [Summary] [Object] To provide a dry etching method for a semiconductor substrate capable of controlling the formation of an adhered film by plasma polymerization while utilizing plasma etching. [Structure] A pair of electrodes 12 connected to a high frequency power supply 13.
A and 12b are installed in the chamber 11. The silicon substrate X1 is installed on the lower electrode 12b. CHF3
After supplying CHF3 gas which is a fluorocarbon gas from the gas supply device 16 and Cl F3 gas which is an interhalogen compound gas from the Cl F3 gas supply device 17, the high frequency power supply 13 is turned on. As a result, the inner wall of the chamber 11 becomes C
l Covered with halogen radicals generated from F3 gas, CH
It suppresses the generation of polymer due to the plasma polymerization of F3 gas, and controls the generation of the adhered film appropriately. That is, the size shift is reduced by controlling the shape of the opening to an appropriate shape. Further, dust due to the polymer adhering to the inner wall of the chamber 11 is also reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method and a dry etching apparatus for removing a part of a semiconductor substrate by using a gas.

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method and a dry etching apparatus for removing a part of a semiconductor substrate by using a reactive gas.

In recent years, the degree of integration of various semiconductor devices has been steadily increasing in accordance with demands for higher performance and compactness of electronic devices. Here, in manufacturing a semiconductor device, it is necessary to have a technique of forming an element such as a transistor on a semiconductor substrate and further forming an insulating layer and an electric wiring layer three-dimensionally thereon. That is, it is important not only to deposit the insulating film and the conductive film, but also to selectively or entirely remove the insulating film and the conductive film. As a technique for removing such an insulating film, a wet etching method using a liquid as an etching agent,
There is a dry etching method using gas, which is properly used in each step of the manufacturing process according to the material, shape, etc. of the object to be etched. Today, the dry etching method can be said to be an essential technique for manufacturing semiconductor devices.

For example, as an element isolation technique for isolating each element when manufacturing a semiconductor device, LOC is used.
OS (Local Oxidation of Sil)
The abbreviation "icon" is most commonly used. In this method, after a silicon oxide film is formed on a semiconductor substrate, the silicon oxide film is partially grown thick and the thickly grown region is used as an element isolation region. This LO
In the COS technique, a silicon nitride film for masking the silicon oxide film other than the element isolation region is formed on the silicon oxide film. Below, the above-mentioned LOCO
A dry etching method for etching the silicon nitride film in the S forming step will be described.

FIG. 10 is a diagram schematically showing a conventional silicon nitride film etching apparatus. In the chamber 10 of the RIE etching apparatus A, a pair of electrodes 12 a, 1
2b are arranged to face each other in the vertical direction, and the lower electrode 12b
A silicon substrate X1 is electrically connected to and installed on the above. From the CH2 F2 gas supply device 18 and the CF4 gas supply device 19, CH2 F2 gas and CF4 gas as etching reactive gases in the chamber 10 are each 30 cm.
Introduce at a flow rate of about 3 / min and 15 cm3 / min. And
By applying a high frequency voltage of 13.56 MHz with a power of 250 W from a high frequency power source 13 while maintaining the pressure of 8 Pa by a vacuum pump through the exhaust port 15, plasma is generated in the reactive gas, and the silicon nitride film 1
To etch.

FIGS. 11A to 11E show cross sections of the silicon substrate X1 in respective steps for forming the element isolation region.

First, as shown in FIG. 11A, a silicon oxide film 2 having a thickness of about 10 nm to 20 nm and a silicon nitride film 1 having a thickness of about 160 nm to 200 nm are deposited on a silicon substrate body 3, and After coating the photoresist film 5 on the top, patterning is performed to form a mask of the photoresist film 5.

Next, as shown in FIG. 11B, dry etching is performed using the photoresist film 5 as a mask to selectively remove only the silicon nitride film 1. At this time, the opening 7 is formed in the region where the element isolation region is to be formed.

After that, as shown in FIG. 11C, the photoresist film 5 is removed by ashing.

After the silicon nitride film 1 serving as a mask in the oxidation process of the silicon oxide film 2 is patterned by the above process, the process proceeds to the selective oxidation process of the silicon oxide film 2.

That is, as shown in FIG. 11D, the patterned silicon nitride film 1 is used as a mask to selectively oxidize the silicon oxide film 2 in the opening 7 of the mask to grow the oxide film thick. LOCOS4 that is an element isolation region
To get

Thereafter, as shown in FIG. 11E, only the silicon nitride film 1 is removed by a wet etching method using hot phosphoric acid as a main component.

Through the above steps, the silicon oxide film 2 is formed on the silicon substrate body 3 and a part thereof is thickened,
This is the element isolation region.

In another example, when a multilayer wiring layer is provided on a semiconductor substrate, the interlayer insulating film is selectively etched to form a contact hole for contacting an electric wiring with an active region of the substrate. There is a way to do it. Regarding the opening of the contact hole for wiring, after the interlayer insulating film is etched and the base substrate or the like is exposed, the base is also subjected to the etching action to some extent and a damaged layer is formed. Since the damaged layer adversely affects the function of the semiconductor device, a step of removing the damaged layer after etching is essential and very important. The conventional dry etching method for forming contact holes will be described below.

FIG. 12 is a diagram schematically showing a conventional silicon oxide film contact etching apparatus. here,
An example of using the three-electrode type etching apparatus A will be described. In the chamber 10 of the etching apparatus A, on the lower electrode 12b of the counter electrodes 12a to 12c, a silicon oxide film is deposited after the switching transistor is formed and a photoresist film is patterned to form a silicon substrate X2 (detailed view). Is omitted). CHF3 gas and CHF are used as etching gas in the chamber 10.
The pressure of 26.8 Pa is maintained by the vacuum pump through the exhaust port 15 while introducing 4 gas. In addition, the high-frequency power source 13a to the lower electrode 12b 10
While applying a high frequency voltage of 0 kHz with a power of 100 W, the high frequency power source 13b applies 13.56 M to the lateral electrodes 12c.
A voltage of Hz is applied with a power of 200W.

FIG. 13 shows the flow of a conventional contact etching process. First, in step SR11, CHF3 gas and CHF are used as etching gas in the chamber 10.
4 gases are introduced at a flow rate of 27 cm3 / min and 9 cm3 / min, respectively, and a high frequency voltage is applied in step SR12. Thereby, in step SR13, plasma is generated, and in step SR14, contact etching is performed to remove the silicon oxide film on the silicon substrate X2 to form a contact hole, and then in step SR15,
The high frequency power supply 13 is turned off in order to finish the contact etching on the silicon substrate X2.

Then, in step SR16, CF4 gas and CHF4 gas are introduced into the chamber at a flow rate of 20 cm3 / min and 40 cm3 / min, respectively, in order to remove the damaged layer of etching, and in step SR17, the high frequency power supply 13 is turned on. Turn on and apply high frequency voltage. As a result, plasma is generated in the gas in step SR18, the damaged layer is etched in step SR19, and step SR2 is performed.
At 0, the etching ends.

[0018]

By the way, the above LOC
In the OS formation process, as the degree of integration of semiconductor devices increases, the dimension between element isolation regions also becomes finer. Therefore, it is important to improve the processing accuracy of dry etching of the silicon nitride film. The same applies to contact etching.

Here, among dry etching, plasma etching means CF 4 gas, CHF 3 gas,
By introducing a mixed gas of CH2 F2 gas, etc. and H2 gas, O2 gas, etc., F radicals are generated in plasma, and by the reaction of these F radicals with silicon, vaporizable substances such as SiF and WF6 are generated. It is also a method. Then, starting with a film of a substance containing silicon such as a silicon substrate, a silicon oxide film, a silicon nitride film, Al, Mo
, W film and the like are patterned.

At this time, in the plasma etching, ions and neutral radicals are generated, the ions are accelerated toward the silicon substrate, and the collision energy removes the silicon nitride film 1 and the like, so that anisotropic etching is performed. Becomes On the other hand, since radicals are neutral, they are not accelerated by an electric field or the like and are isotropic etching. However, at the same time as the etching using the carbon-containing gas, the plasma polymerized film adheres to the portion to be etched, especially the side wall of the opening, so that isotropic etching due to radicals is suppressed. That is,
Undercuts are prevented from being generated just below the mask due to etching of the sidewalls. This is the advantage of plasma etching.

However, in the dry etching method of the silicon nitride film 1 and the like performed when forming the above-mentioned conventional LOCOS 4, as shown in FIGS. 11B and 11C,
The shape of the opening 7 of the silicon nitride film 1 after etching is 60
There is a phenomenon that it becomes a forward taper of a degree. Therefore, the dimensional shift of the patterning of the silicon nitride film 1 is about 0.1 μm.

Therefore, as the degree of integration of semiconductor devices increases, it becomes necessary to narrow the width of the silicon oxide film for element isolation, but this dimensional shift further narrows the width of LOCOS, which is necessary. There is a possibility that the element isolation function may not be obtained. Further, in the gas system of CH2F2 and CHF4, when plasma is generated, a polymer is generated as described above and adheres to the substrate or the inner wall of the chamber as an adhered film, and this polymer becomes dust, which adversely affects the manufacturing of semiconductor devices. There was a risk of it.

On the other hand, even in the dry etching for forming the contact hole, there is a problem that dust is often generated due to the above-mentioned dimensional shift and generation of polymer. In addition, as shown in FIG. 13 described above, steps SR11 to
When SR15 is dry-etched, not only the silicon oxide film 2 but also the underlying silicon substrate body 3 is simultaneously etched, and a damaged layer is generated. For this reason, in order to remove the damaged layer, it is necessary to provide a process (steps SR16 to SR19 in FIG. 11) in which a reactive gas is introduced under different conditions and a high frequency voltage is applied again to etch the damaged layer. It was

The present invention has been made in view of the above problems, and its main purpose is to generate a dust and a dimensional shift due to the generation of a polymer by plasma polymerization of CHF3 molecules or the like due to the decomposition of carbon fluoride gas. Therefore, it is intended to suppress dimensional shift and reduce dust by taking measures to suppress such plasma polymerization.

A second object is to simplify the manufacturing process by providing a means for removing the damaged layer in the dry etching process, thereby eliminating the need for a special process for removing the damaged layer later. It is in.

[0026]

In order to achieve the above object, the means of the invention of claim 1 is an etching apparatus in which at least one pair of electrodes connected to a high frequency power source is provided in a chamber. Then, as a dry etching method in which a part of the semiconductor substrate is removed by reaction with a reactive gas, the semiconductor substrate is placed in a chamber, and at least an interhalogen compound gas and a carbon fluoride gas are placed in the chamber. Then, a high frequency voltage is applied to the electrodes from the high frequency power source.

The means taken by the invention of claim 2 is the method according to the invention of claim 1, wherein the portion to be etched of the semiconductor substrate is made of a substance containing silicon.

The means taken by the invention of claim 3 is the method according to the invention of claim 1, wherein the etched portion of the semiconductor substrate is an insulating film.

According to a fourth aspect of the present invention, in the above-mentioned first, second or third aspect of the invention, the surface of the conductive portion below the insulating film is formed by removing a part of the insulating film from the etched portion of the semiconductor substrate. This is a method of forming a contact hole that exposes.

According to a fifth aspect of the invention, in the invention of the third aspect, the portion to be etched of the semiconductor substrate is
This is a method of using a silicon nitride film as a mask for forming LOCOS.

According to a sixth aspect of the invention, in the invention of the first or fifth aspect, the supply of the interhalogen compound gas is stopped immediately before the removal of the etched portion is completed,
Then, the method is such that a treatment with a carbon fluoride gas to which a high frequency voltage is applied is performed.

According to a seventh aspect of the present invention, in the first or fifth aspect of the invention, the amount of the interhalogen compound supplied is reduced when the removal of the portion to be etched approaches the end. Is.

According to the means of the invention of claim 8, in the invention of claim 1 or 4, the application of the high frequency voltage is stopped after the removal of the portion to be etched is completed, and at least the interhalogen compound gas is introduced into the chamber. It is a method to be left.

The means taken by the invention of claim 9 is the same as that of the invention of claim 1, wherein Cl is used as the interhalogen compound gas.
This is a method using F3 gas.

According to the invention of claim 10, in the invention of claim 1 or 9, the carbon fluoride gas is C
This is a method using at least one of HF3 gas and CH2 F2 gas.

The means taken by the invention of claim 11 is the method according to the invention of claim 1, 9 or 10, wherein an inert gas is mixed in addition to the carbon fluoride gas and the interhalogen compound gas.

According to a twelfth aspect of the present invention, a semiconductor substrate is installed as a dry etching apparatus for removing a part of the semiconductor substrate by a reaction with a reactive gas.
A chamber for etching with a gas, a gas supply device for supplying a reactive gas to the chamber, at least one pair of electrodes arranged in the chamber, and a high-frequency voltage applied between the electrodes. A high-frequency power source, a first gas outlet connected to the gas supply device via a gas pipe and having a large number of pores for blowing gas from the upper part of the chamber, and connected to the gas supply device via a gas pipe. In addition, a second gas outlet having a large number of pores for ejecting gas from the side of the chamber and an outlet for ejecting gas from the chamber are provided.

According to a thirteenth aspect of the present invention, in the invention of the twelfth aspect, the inner surface of the chamber is formed in a cylindrical shape, and the second gas outlet is arranged in a side portion of the chamber in a cylindrical shape. The pores are arranged over the entire cylindrical surface.

According to a fourteenth aspect of the present invention, a dry etching apparatus for removing a part of a semiconductor substrate by a reaction with a gas is used. A chamber for etching with a gas, a gas supply device for supplying a reactive gas to the chamber, at least one pair of electrodes arranged in the chamber, and a high-frequency voltage applied between the electrodes. A high frequency power source and a spherical gas outlet connected to the gas supply device through a gas pipe and having a large number of pores for blowing gas from the upper part of the chamber are provided.

In the invention of claim 15, in the invention of claim 12, 13 or 14, the fine holes are arranged at equal intervals along the inner wall of the chamber.

[0041]

According to the above method, in the invention of claim 1, the interhalogen compound gas and the carbon fluoride gas are brought into a plasma state by the application of a high frequency voltage in the chamber of the etching apparatus, and the gas is decomposed into plasma. Ions of the constituent molecules and atoms collide with a part of the semiconductor substrate. Then, a part of the semiconductor substrate is removed by the reaction between the ions and the substance forming the etched portion of the semiconductor substrate.

At this time, a part of the carbon fluoride gas forms a polymer by plasma polymerization to form an adhered film, which tends to be deposited on the inner wall of the chamber or the object to be etched on the semiconductor substrate. However, since the gas of the interhalogen compound is decomposed to generate a large amount of halogen radicals, the bond between the halogen radicals and the carbon atoms is preferentially generated rather than the plasma polymerization of the carbon fluoride gas, so that the vaporizable carbon halide and Become.
Therefore, the amount of the polymer deposited on the side wall of the opening due to the plasma polymerization, that is, the amount of the attached film that interferes with the isotropic etching action is suppressed and becomes an appropriate amount. In other words, the occurrence of undercuts on the sidewalls of the opening just below the mask is prevented, the occurrence of taper on the sidewall of the etching opening is suppressed, and the dimensional shift from the etching start portion to the etching end portion is reduced. .

Further, since the gas of the interhalogen compound is decomposed to generate a large amount of halogen radicals even when the high frequency voltage is not applied, the inner wall of the chamber has halogen radicals before the carbon fluoride gas is plasma-polymerized to form a polymer. Covered with. Therefore, vaporizable carbon halide is preferentially produced over polymer production by plasma polymerization.
That is, the generation of an adhered film on the inner wall of the chamber due to the plasma polymerization is suppressed, and the dust is reduced.

According to the second aspect of the invention, volatile silicon fluoride is produced by the bonding reaction between silicon and the fluorine radical decomposed from the carbon fluoride gas, and the etching action becomes remarkable.
The etching efficiency will be improved.

In the third aspect of the present invention, the insulating film of the semiconductor substrate is generally patterned by dry etching in many cases, but in that case as well, anisotropy due to plasma etching is ensured, and The dimensional shift and the generation of dust are suppressed.

According to a fourth aspect of the present invention, in the dry etching for forming the contact hole, the above-mentioned first and second aspects are adopted.
Due to the action of the invention of 2 or 3, a highly accurate contact hole with a small dimensional shift is formed.

In the invention of claim 5, the silicon nitride film for forming the LOCOS is formed by plasma etching.
In particular, a tapered opening is likely to occur, but since the formation of an adhered film by the interhalogen compound gas is suppressed, the dimensional shift is reduced and the dimensional accuracy of the formed semiconductor device is significantly improved.

In the invention of claim 6, in the operation of the invention of claim 1, when the supply of the interhalogen compound gas is stopped immediately before the removal of the portion to be etched, the plasma polymerization of the fluorocarbon gas is performed. As a result, the amount of the adhered film generated is increased, and the surface of the underlayer is covered with the adhered film at the end of etching. Therefore, the underlayer is protected by the adhesion film,
Less damage due to etching of the underlayer.

According to the seventh aspect of the invention, when the removal of the portion to be etched approaches the end, the supply amount of the interhalogen compound is reduced, so that the same effect as the invention of the sixth aspect occurs.

In the invention of claim 8, when the high frequency power supply is stopped after the etching is completed, the plasma etching action is also stopped. Then, by supplying the interhalogen compound gas as it is, the damaged layer generated in the underlayer by the plasma etching is removed in a self-aligned manner by the chemical polishing action of the halogen radicals in the non-plasma.

In the ninth aspect of the invention, when the Cl F3 gas is introduced into the chamber, the chamber is filled with radical fluorine atoms or chlorine atoms before the high frequency is applied. Therefore, the production of a vaporizable substance due to the bond with a fluorine atom or a chlorine atom is prioritized over the polymerization of carbons in a fluorocarbon gas. Therefore, the production of the polymer, that is, the production of the adhered film is appropriately adjusted, and the above-mentioned dimensional shift and dust reduction action becomes remarkable.

According to the tenth aspect of the invention, the anisotropic etching action by the plasma etching of the CHF3 gas or the CH2F2 gas and the action of forming the adhering film by the plasma polymerization are appropriately adjusted, and the action of reducing the dimension shift and dust is achieved. It becomes remarkable.

In the eleventh aspect of the present invention, by mixing an inert gas such as argon gas, the polymerization of the polymer is suppressed, so that the dust reducing effect is great.

According to the twelfth aspect of the present invention, when the reactive gas is blown out from a large number of pores into the chamber at a high speed, the amount of polymer produced by plasma polymerization, that is, the amount of adhering film, is reduced near the pores. Here, since the air outlet is provided not only in the upper portion of the chamber but also in the side portion, the amount of dust adhering to the inner wall of the chamber is reduced, and the adverse effect of dust on the semiconductor device is suppressed.

According to the thirteenth aspect of the present invention, the reactive gas is supplied at a high speed from the entire side portion through each of the pores of the second outlet provided in the cylindrical shape, so that the amount of dust on the side wall is significantly reduced. Will be done.

According to the fourteenth aspect of the present invention, since the high-speed reactive gas is supplied to the entire inner wall of the chamber through the spherical outlet, the dust reducing effect is particularly remarkable.

According to the fifteenth aspect of the invention, since the pores are arranged at equal intervals in the outlet for supplying the reactive gas, the gas having a substantially uniform wind speed is locally supplied to the dust. The reduction effect of is assured.

[0058]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows an etching apparatus A.
The outline of is shown. As shown in FIG. 1, the RIE etching apparatus A includes a casing including a cylindrical chamber body 11b having a bottomed cylindrical shape with an open top and a chamber lid member 11a covering the top of the chamber body 11b. Have And, in the casing, the opposite 1
A pair of vertical electrodes 12a and 12b is installed, and a silicon substrate X1 which is a workpiece is installed on the lower electrode 12b. The lower electrode 12b is connected to the high frequency power supply 13. A gas supply pipe is provided so as to penetrate the upper electrode 12a of the chamber lid member 11a.
A first gas outlet 14a having a large number of gas supply holes is provided below 2a, and a chamber body 11b is provided.
The second side gas outlet 14b having a large number of gas supply holes connected to the gas supply pipe is also provided on the cylindrical side wall of the. Further, an exhaust port 15 is provided at the bottom of the chamber body 11b. In addition, each of the gas outlets 14a and 14b described above.
The gas supply holes are arranged along the inner wall of the chamber so as to be equidistant from each other.

Further, each of the gas supply pipes is connected to a CHF3 gas supply device 16 and a ClF3 gas supply device 17, and the CHF3 gas and C gas are introduced into the chamber of the etching apparatus A.
It is designed so that a mixed gas with F3 gas can be supplied. Also, through the exhaust port 15, 100
While maintaining a pressure of mTorr, by applying a high frequency voltage of 13.56 MHz between the electrodes 12a and 12b with a power of 250 W, plasma is generated in the gas,
It is configured to etch the silicon nitride film.

2A to 2E show cross sections of the silicon substrate X1 in the LOCOS forming step.

First of all. As shown in FIG. 2A, a silicon oxide film 2 having a thickness of 10 nm and a thickness of 160 are formed on the silicon substrate 3.
After depositing a silicon nitride film 1 having a thickness of 1 nm and applying a photoresist film 5, a pattern of the photoresist film 5 is formed.

Next, as shown in FIG. 2B, dry etching is performed using the photoresist film 5 as a mask,
Silicon nitride film 1 in the opening region of photoresist film 5
Are selectively removed to form an opening 7 for LOCOS. At that time, Cl F3 gas and CHF3 gas are introduced at a flow rate of 4 cm3 / min and 40 cm3 / min, respectively.

Then, as shown in FIG. 2C, ashing is performed to remove the photoresist film 5. In this state, the pattern of the silicon nitride film 1 having the opening 7 in the region where the LOCOS is formed is formed.

Next, as shown in FIG. 2 (d), selective oxidation is performed using the silicon nitride film 1 as a mask to obtain LOCO.
S4 is formed.

Thereafter, as shown in FIG. 2E, only the silicon nitride film 1 is removed by a wet etching method using hot phosphoric acid as a main component.

In the dry etching process of the above embodiment, as shown in FIG. 2B, the shape of the opening 7 in the silicon nitride film 1 after etching has a taper angle of about 5 degrees. That is, the taper angle is extremely small compared to the taper angle of 60 degrees in the above-described conventional dry etching method, and the photoresist film 5 is almost opened at an angle close to the vertical from the opening. Therefore, the dimension shift from the mask pattern at the lower end of the opening of the silicon nitride film 1 is slight. This is based on the following actions.

That is, as shown in FIG. 3A, a gas obtained by mixing a normal fluorocarbon gas such as CHF3 gas, CH2 F2 gas or CF4 gas with O2 gas, H2 gas or the like is used as an etching gas. When used as a radical, the separated C atoms are radically polymerized by generating Si F4,
Produces an adherent film or polymer. However, the same figure (b)
As shown in, when using Cl F3 gas, Cl F3 gas
Since gas molecules generate a large amount of fluorine radicals and chlorine radicals even in the absence of plasma, when Cl F3 gas is introduced into the apparatus before plasma generation, a large amount of fluorine and chlorine is generated on the inner wall of the apparatus, electrodes and substrate surface. Covered with radicals. In this state, a high-frequency voltage is applied thereafter to generate plasma, so that the carbon atoms dissociated from the CHF3 molecules are not only on the inner walls of the device and the electrodes but also on the silicon substrate X.
On the above, a large amount of fluorine radicals generated from Cl F3 gas and a carbon-fluorine bond are generated, and CF4 molecules are vaporized. Therefore, the number of bonds between carbon atoms (C) is reduced,
The amount of the deposited film made of the polymer is small.

That is, in conventional plasma etching, undercutting unlike in isotropic etching does not occur because it is anisotropic etching and the side wall is protected by the formation of the above-mentioned adhesion film, but on the other hand, ,
It is considered that the excessive adhesion film is deposited, the lateral etching action becomes poor, and the shape of the opening 7 of the silicon nitride film 1 becomes tapered. On the other hand, as in the above embodiment, by admixing a gas such as Cl F3 gas that does not require the presence of plasma, the deposition of the adhesion film is adjusted appropriately, and the opening 7 such as the silicon nitride film is almost tapered. It seems that there will be no shape and the dimensional shift will be slight.

In addition, since the formation of the polymer adhesion film is suppressed, the generation of dust is greatly suppressed.

That is, by mixing a gas of an interhalogen compound in the carbon fluoride gas instead of oxygen or the like, the above-mentioned dimensional shift is eliminated and dust is prevented from occurring, so that the semiconductor device is highly integrated. That is, it is possible to proceed with the process corresponding to the miniaturization of device dimensions.

FIG. 4 is data showing the experimental results of the selection ratio and the deposition rate by the conventional method and the method of the present invention. As a conventional method, data using a mixed gas of CHF4 gas and CF4 gas, which is generally used for forming a contact hole, is shown. Further, as for the selection ratio, the etching rate of the BPSG film with respect to the polysilicon film is measured, and it is shown that the higher the selection ratio, the less the damage to the base. For the convenience of the experiment, the base is polysilicon, but the selection ratio is improved when the base is single crystal silicon. In addition, the deposition speed measures the thickness of the adhered film adhered to the inner wall of the chamber.

As shown in the figure, CHF3 gas and C
In the mixed gas with F4 gas, if the proportion of CF4 gas is made small, the deposition rate becomes high and the selection ratio becomes high. Further, in the mixed gas of CHF3 gas and ClF3 gas, if the proportion of ClF3 gas is decreased, the deposition rate becomes higher and the selection ratio becomes higher. This result is CF
It is supported by the fact that 4 gas does not generate radicals unless plasma is generated, but Cl F3 gas generates radicals even if plasma is not generated, and the amount thereof is large. Therefore, the Cl F3 gas is more effective in preventing the formation of the polymer film. In order to reduce the damage to the base, it is necessary to increase the selection ratio. However, when a mixed gas of CHF3 gas and ClF3 gas is used, compared with the conventional one which does not use interhalogen compound gas. It is possible to suppress the generation of the adhered film while increasing the selection ratio to reduce the damage of the base. That is, as described above, it is possible to reduce the dimensional shift and suppress the generation of dust.

Although the embodiment is omitted, the flow rate of Cl F3 gas may be reduced when the formation of the contact hole progresses and approaches the end.

(Second Embodiment) Next, a second embodiment relating to dry etching for forming a contact hole will be described with reference to FIGS. In this embodiment, a three-electrode type etching apparatus having a configuration similar to that shown in FIG. 12 is used as the etching apparatus. However, a Cl F3 gas supply device is used instead of the CF4 gas supply device.

FIGS. 5A to 5C show an etching process for forming a contact hole, and FIG. 5 shows a procedure of the etching process.

First, as shown in FIG. 5A, a BPSG film 6 which is a silicon oxide film containing boron and phosphorus is deposited on a silicon substrate 3, and a photoresist film 5 is formed thereon.
And patterning.

Next, the semiconductor substrate X2 which has undergone this step is
The same etching apparatus as that shown in FIG. 1 is mounted and dry etching is performed by the following procedure. At that time, Cl F3 gas and CHF3 gas are 2 cm3 / min and 120 cm3 / min, respectively.
It is introduced at a flow rate of min. First, step ST1 in FIG.
In step 1, an etching gas is introduced into the etching apparatus, in step ST12, the high frequency power supply is operated, and in step ST13, plasma is generated. By this plasma generation, etching for forming a contact hole is performed. That is, as shown in FIG. 5B, dry etching is performed using the photoresist film 5 as a mask, the BPSG film 6 is selectively removed, and the contact hole 8 is opened. At this time, the silicon substrate 3
Also undergoes the etching action, so the contact hole 8
An etching damage layer is formed on the surface portion of the silicon substrate body 3 exposed at the bottom portion 8a.

In step ST15 of FIG. 6, the high frequency power source 13 is stopped and the Cl F3 gas is left in the etching apparatus as it is. Then, as described above, C
Since the F 3 gas produces a large amount of fluorine radicals and chlorine radicals without generating plasma, in step ST16 of FIG. 6, the damaged layer formed on the bottom portion 8a of the contact hole 8 has an etching action without plasma effect. received,
As shown in FIG. 5C, it is removed in a self-aligned manner by the chemical polishing effect.

In the etching method of this embodiment, the dimensional shift is small, and due to the effect of Cl F3, almost no polymer is produced even if CHF3 is used, and the dust can be greatly reduced. Moreover, unlike the conventional contact etching step, it is not necessary to newly provide a step for removing the damaged layer, so that the process can be simplified.

7 and 8 are characteristic diagrams for comparing the etching rate (black circles) and the etching uniformity (white circles) in the etching for forming the contact holes. FIG. 7 shows an embodiment of the present invention, in which Cl F3 gas and CH
The characteristics when a mixed gas with F3 gas is used are shown below. FIG. 8 shows a case where a conventional mixed gas of CF4 gas and CFHF3 gas is used. However, the etching uniformity Eun
i is based on the following equation Euni = (Tmax-Tmin) / (Tmax + Tmin) (Tmax is the maximum thickness of the unremoved film when the contact hole is formed, and Tmin is the minimum thickness).

Comparing the two, it can be seen that the etching rate of the method of the present invention is not so different from the conventional method, but the etching uniformity Euni is improved. This indicates that radicals are uniformly generated in the plane of the wafer during etching, and the adhesion film is also uniformly generated. It can be seen that the uniformity is improved even if the ratio of Cl F3 gas is increased and the etching rate is increased. Further, since the uniformity is improved, the disorder of the underlying silicon after the formation of the contact holes is reduced, so that the damage of the underlying layer can be suppressed.

(Third Embodiment) Next, a third embodiment will be described.

In this embodiment, the etching apparatus and silicon substrate X1 used are the same as in the first embodiment (see FIGS. 1 and 2).

FIG. 9 shows a flow of steps for forming an opening of a silicon nitride film for a LOCOS mask in the third embodiment. In step ST21, CHF3 gas and ClF3 gas are introduced as etching gas, and step ST
At step 22, a high frequency voltage is applied, and at step ST23, plasma is generated. By the generation of this plasma, the opening of the silicon nitride film 1 is formed in step ST24. Then, in step ST25, the supply of the Cl F3 gas is stopped immediately before the formation of the opening of the silicon nitride film 1 is completed, that is, when the thickness of the unetched layer between the underlying silicon oxide film 2 is very thin. , CHF3 gas is flowed, and the voltage of the high frequency power supply is lowered in step ST26, and when a certain time has elapsed, step ST27
Then, turn off the power. Then, after that, step ST2
At 8, the supply of CHF3 gas is stopped.

In the third embodiment described above, only the supply of Cl F3 gas is stopped immediately before the formation of the opening for LOCOS is completed, and then the remaining film is removed only by the plasma etching of CHF3 gas. That is, if both gases are flowed until the formation of the opening of the silicon nitride film 1 is completed, the etching is performed under the condition that the adhesion film is not formed so that the silicon oxide film 2 is removed after the removal of the silicon nitride film 1. However, there is a risk of etching a considerable amount.
On the other hand, as in the third embodiment, by stopping the supply of only the Cl F3 gas immediately before the formation of the opening is completed, the adhesion film on the surface to be etched gradually increases,
Since the formation of the opening is completed in this state, damage to the surface of the underlying silicon oxide film 2 due to dry etching is prevented.

In the third embodiment, the supply of Cl F3 gas is stopped immediately before the formation of the opening is ended. However, when the formation of the opening progresses and approaches the end, the supply amount of Cl F3 gas is changed. The same effect can be obtained even if it is gradually reduced.

Here, the ratio of the flow rate of the interhalogen compound gas to the flow rate of the entire reactive gas is preferably about 50% or less for the silicon nitride film and 10% or less for the silicon oxide film.

Although the RIE type etching apparatus is used in each of the above-mentioned embodiments, the present invention is not limited to such an embodiment, and various electrodes such as a three-electrode type, a magnetron RIE type and an ECR type are used. Similar results are obtained using an etching system.

Further, although CHF3 gas is used as the carbon fluoride gas in the above-mentioned respective embodiments, the same result can be obtained by using CH2F2 gas. A gas other than the carbon fluoride gas and the interhalogen compound gas, such as oxygen gas, may be contained. In particular, in order to prevent the generation of dust due to the adhered film formed during etching, the use of an inert gas such as argon gas as the additive gas provides a better effect.

[0091]

As described above, according to the invention of claim 1, as a dry etching method for etching a semiconductor substrate with a reactive gas, the semiconductor substrate is placed in a chamber and at least a halogen-containing space is provided in the chamber. Since the high frequency voltage was applied to the electrode after introducing the compound gas and the carbon fluoride gas, the carbon atom generated by the decomposition of the carbon fluoride gas, and the carbon-carbon bond between the molecules containing carbon, It can be suppressed by the radical atom of halogen, and therefore, the dimensional shift and the generation of dust can be suppressed, and the manufacturing process corresponding to the high integration of the semiconductor device can be realized.

According to the invention of claim 2, since the invention of claim 1 is applied to the case where the portion to be etched of the semiconductor substrate is composed of a substance containing silicon, volatile silicon fluoride is produced. Thus, it is possible to suppress the formation of the adhered film while significantly exhibiting the etching effect.

According to the invention of claim 3, since the invention of claim 1 is applied to the case where the portion to be etched of the semiconductor substrate is composed of an insulating film, the insulating film is patterned by dry etching. At this time, dimensional shift and generation of dust can be reduced while ensuring anisotropy due to plasma etching.

According to the invention of claim 4, the above-mentioned claim 1
Since the invention of 2 or 3 is applied to the dry etching for forming the contact hole, it is possible to form a highly accurate contact hole with a small dimensional shift.

According to the invention of claim 5, in the invention of claim 3, the portion to be etched is a silicon nitride film for forming LOCOS. Therefore, a silicon nitride film which is particularly likely to cause a tapered opening by plasma etching is formed. On the other hand, since the formation of the adhered film due to the interhalogen compound gas is suppressed, the dimensional shift is reduced and the dimensional accuracy of the formed semiconductor device is significantly improved.

According to the invention of claim 6, in the invention of claim 1 or 5, the supply of the interhalogen compound gas is stopped and the high frequency voltage is applied immediately before the removal of the etched portion is completed. Since the treatment with the carbon fluoride gas is performed, the surface of the underlayer can be protected by the adhesion film at the end of etching, and thus the etching damage of the underlayer can be reduced.

According to the invention of claim 7, in the invention of claim 1 or 5, the supply amount of the interhalogen compound is reduced when the removal of the portion to be etched approaches the end. The same effect as that of the invention of Item 6 can be obtained.

According to the invention of claim 8, in the invention of claim 1 or 4, the application of the high frequency voltage is stopped after the etching is completed and the interhalogen compound gas is left in the chamber. The action can be stopped and the underlayer can be chemically polished with an interhalogen compound gas, and thus the damaged layer generated in the underlayer by plasma etching can be removed in a self-aligned manner.

According to the ninth aspect of the present invention, since ClF3 gas is used as the interhalogen compound gas in the first aspect of the invention, fluorine radicals or chlorine radicals can be easily generated, and therefore, the adhesion film can be formed. It is possible to remarkably exert the effects of dimensional shift and dust reduction by appropriately adjusting the generation of

According to the invention of claim 10, the above-mentioned claim 1
In the invention of 9 or 9, since at least one of CHF3 gas and CH2 F2 gas is used as the fluorocarbon gas, CHF3 gas or CH2 gas having a large effect of plasma etching and formation of an adhered film by plasma polymerization is used.
With respect to the F2 gas, it is possible to appropriately control the formation of the adhered film, and to significantly exhibit the effect of reducing the size shift and dust.

According to the invention of claim 11, in the invention of claim 1, 9 or 10, the inert gas is mixed in addition to the carbon fluoride gas and the interhalogen compound gas.
The dust reduction effect can be remarkably exhibited.

According to the twelfth aspect of the present invention, the dry etching apparatus has a structure in which not only the upper portion of the chamber but also the side portions are provided with air outlets made of a large number of pores. By utilizing the reduction effect, the amount of dust adhering to the inner wall of the chamber can be significantly reduced.

According to the invention of claim 13, the above-mentioned claim 1
In the second aspect of the invention, since the side outlet is formed in a cylindrical shape, the amount of dust on the side wall can be significantly reduced by supplying the reactive gas at a high speed from the entire side portion.

According to the fourteenth aspect of the present invention, the dry etching apparatus is configured such that the reactive gas outlet has a large number of spherically arranged pores, so that the entire inner wall of the chamber is covered. By supplying the reactive gas at a high speed, the dust reduction effect can be remarkably exhibited.

According to the invention of claim 15, the above-mentioned claim 1
In the invention of 2, 13, or 14, since the respective pores are arranged at equal intervals along the inner wall of the chamber at the blowout port for supplying the reactive gas, the gas having a substantially uniform wind speed is locally generated. As a result, the dust reduction effect can be reliably exhibited.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a configuration of an etching apparatus in an example.

FIG. 2 is a cross-sectional view showing a state of a silicon substrate in a LOCOS forming step by the method of the first embodiment.

FIG. 3 is a diagram illustrating the formation of an adhered film by plasma polymerization and the mechanism of vaporizable substance generation by halogen atoms.

FIG. 4 is a characteristic diagram showing characteristics of a deposition rate and a selection ratio of a conventional mixed gas of CHF3 gas and CF4 gas and a mixed gas of CHF3 gas and Cl F3 gas according to the embodiment.

FIG. 5 is a cross-sectional view showing a state of a silicon substrate in a contact etching step by the method of the second embodiment.

FIG. 6 is a flow chart showing the procedure of an etching process in the second embodiment.

FIG. 7 is data showing the experimental results on the dependence of the etching rate and uniformity of the BPSG film on the Cl F3 gas concentration when using Cl F3 gas.

FIG. 8: B when no interhalogen compound gas is used
3 is data showing experimental results on the dependence of etching rate and uniformity of PSG film on CF4 gas concentration.

FIG. 9 is a flowchart showing a contact etching process in the third embodiment.

FIG. 10 is a diagram schematically showing a configuration of a conventional etching device for a silicon nitride film.

FIG. 11 is a cross-sectional view showing a state of a silicon substrate in a LOCOS forming step by a conventional method.

FIG. 12 is a diagram schematically showing a configuration of a conventional contact hole etching apparatus.

FIG. 13 is a flow chart showing a conventional contact hole etching process.

[Explanation of symbols]

 1 Silicon Nitride Film 2 Silicon Oxide Film 3 Silicon Substrate Body 4 LOCOS 5 Photoresist Film 6 BPSG Film 7 Opening (for LOCOS) 8 Contact Hole 11a Chamber Body 11b Chamber Lid Member 12a Upper Electrode 12b Lower Electrode 13 High Frequency Power Supply 14a First Gas Air outlet 14b Second gas outlet 15 Exhaust outlet A Etching device X Silicon substrate

Claims (15)

[Claims] 1. A dry etching in which a part of a semiconductor substrate is removed by reaction with a reactive gas in an etching apparatus in which at least one pair of electrodes connected to a high frequency power source is provided in a chamber. A semiconductor substrate is placed in a chamber, at least an interhalogen compound gas and a carbon fluoride gas are introduced into the chamber, and then a high frequency voltage is applied from the high frequency power source to the electrode. A dry etching method characterized by. 2. The dry etching method according to claim 1, wherein the portion to be etched of the semiconductor substrate is made of a substance containing silicon. 3. The dry etching method according to claim 1, wherein the etched portion of the semiconductor substrate is an insulating film. 4. The dry etching method according to claim 1, 2 or 3, wherein the etched portion of the semiconductor substrate is a contact hole for removing a part of the insulating film to expose a surface of the conductive portion below the insulating film. A dry etching method characterized by the above. 5. The dry etching method according to claim 3, wherein the portion to be etched of the semiconductor substrate is a silicon nitride film serving as a mask for forming LOCOS. 6. The dry etching method according to claim 1, wherein supply of the interhalogen compound gas is stopped immediately before the removal of the portion to be etched is finished, and then a high-frequency voltage is applied to the carbon fluoride gas. The dry etching method is characterized in that the treatment by 7. The dry etching method according to claim 1, wherein the amount of the interhalogen compound supplied is reduced when the removal of the portion to be etched approaches the end. 8. The dry etching method according to claim 1, wherein after the removal of the portion to be etched, the application of the high frequency voltage is stopped and at least the interhalogen compound gas is left in the chamber. Dry etching method. 9. The dry etching method according to claim 1, wherein ClF3 gas is used as the interhalogen compound gas. 10. The dry etching method according to claim 1, wherein at least one of CHF3 gas and CH2F2 gas is used as the carbon fluoride gas. 11. The dry etching method according to claim 1, 9 or 10, wherein an inert gas is mixed in addition to the carbon fluoride gas and the interhalogen compound gas. 12. A dry etching apparatus for removing a part of a semiconductor substrate by a reaction with a reactive gas, wherein a chamber for setting a semiconductor substrate and performing etching with a gas is used. Gas supply device for supplying a reactive gas, at least one pair of electrodes arranged in the chamber, a high-frequency power source for applying a high-frequency voltage between the electrodes, and a gas pipe to the gas supply device. A first gas outlet that is connected and has a large number of pores for blowing gas from the upper part of the chamber; A dry etching etching apparatus comprising: a second gas outlet having fine holes; and a discharge port for discharging gas from the chamber. 13. The dry etching apparatus according to claim 12, wherein the chamber has an inner surface formed in a cylindrical shape, and the second gas outlet is arranged in a cylindrical shape on a side portion of the chamber. The dry etching apparatus is characterized in that the holes are provided over the entire cylindrical surface. 14. A dry etching apparatus for removing a part of a semiconductor substrate by a reaction with a gas, wherein at least an inner surface is formed into a spherical shape, and a semiconductor substrate is installed to perform etching with a reactive gas. A chamber, a gas supply device for supplying a reactive gas to the chamber, at least one pair of electrodes arranged in the chamber, a high frequency power supply for applying a high frequency voltage between the electrodes, and the gas supply. A dry etching apparatus, which is connected to the apparatus via a gas pipe, and is provided with a spherical gas outlet having a large number of pores for blowing gas from an upper portion of the chamber. 15. The dry etching apparatus according to claim 12, 13 or 14, wherein the pores are arranged at equal intervals along the inner wall of the chamber.