JPH0936091A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Abstract] [Purpose] A dry etching method using plasma has the same etching characteristics as the case of using a mixed gas of fluorocarbon gas and CO, which has been developed in the past. Eliminate the danger of
To realize an etching method that can easily ensure safety. A fluorocarbon gas containing CO in a composition formula is used as an etching gas in dry etching. For example, a silicon oxide film 22 formed on a wafer 21 and provided with a mask such as a resist 23 has a predetermined pattern of openings. 24 is formed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a method for manufacturing a semiconductor device,
In particular, it relates to kinds of reactive gas in dry etching using plasma when manufacturing a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of semiconductor devices,
An etching technique for processing various films into a desired shape is used, and the technique is becoming more and more important with the recent miniaturization of semiconductor devices. There are various etching techniques, and among them, the dry etching technique using plasma is known as one of the typical methods.

Next, a general dry etching technique which has been conventionally used will be described. In the etching process, first, a reaction gas described later is introduced into the etching apparatus from a gas introduction pipe. The inside of the reaction chamber is kept under reduced pressure. Several hundred kHz from the high frequency power source to the cathode electrode on which the wafer to be etched is placed.
When a voltage of about several tens Mhz is applied, the reaction gas introduced into the reaction chamber is dissociated and a plasma atmosphere is generated in the reaction chamber. Therefore, a part of the dissociated reaction gas reacts with the exposed silicon oxide film which is not covered with a mask such as a resist, and decomposes the silicon oxide film to advance etching. After the reaction is completed, the reaction gas whose composition has changed is discharged from the gas discharge pipe. The discharged gas is safely treated by adsorption treatment, combustion treatment, water dissolution, etc. without flowing out of the device.

It is desirable that the reactive gas in the dry etching has a high etching rate for the etching target and a large ratio (etching rate) of the etching rate of the etching target to the etching rate of the etching mask such as resist. Therefore, conventionally, as a reaction gas satisfying these properties, a fluorocarbon gas in which a halide such as Cl or F and carbon are chemically bonded has been used. Among them, particularly CF ₄ and CHF ₃ are used for etching a silicon oxide film. , C ₂ F ₆ , C ₃ F ₈ , C ₄
F ₈ etc. are typical.

When these fluorocarbon gases are used as the reaction gas, carbon-based radical species are dissociated from the reaction gas in the plasma atmosphere and deposited as a polymer film on the wafer to be etched, resulting in the etching rate of the mask. It is believed that it has a function of lowering the etching rate and increasing the etching rate. In addition, other volatile gas such as F dissociated from the fluorocarbon gas reacts with the silicon oxide film, and etching proceeds.

[0006]

By the way, in recent years, the carbon-based radical species generated by dissociation by the fluorocarbon gas as described above generate particles,
It has been pointed out that it will cause device defects. This phenomenon is particularly remarkable when a fluorocarbon gas having a relatively large C element ratio is used.
In order to avoid this phenomenon, a fluorocarbon gas having a relatively small element ratio of C should be used, but on the contrary, the deposition rate of the above polymer film becomes slow, so that the effect of increasing the etching rate decreases. Also, there are problems such as lowering the etching rate for the etching target.

In order to solve such a problem, for example, Japanese Patent Laid-Open No. 6163475/1994 and Nikkei Microdevice 1995 2
On pages 54 to 61 of the monthly issue, a technique of adding CO to the fluorocarbon gas as described above is disclosed.

These techniques introduce the above-mentioned fluorocarbon gas and CO into the reaction chamber, and carbon-containing radical species are generated in the plasma by C contained in the mixed gas of the fluorocarbon gas and CO. Then, a polymer film is deposited on the wafer to be etched. Along with this, oxygen radical species are generated in the plasma by O in the mixed gas to oxidize and vaporize the polymerized film, which reduces the deposition rate of the polymerized film, and CO is an element of C rather than O or CO _2. It is understood that, since the ratio is high, the effect of depositing the carbon-based radical species appears strongly, the generation of particles is suppressed, and the etching rate of the silicon oxide film is improved.

However, there are difficulties in putting the techniques described in the above publications into practical use. This is because it is necessary to further introduce CO into the reaction chamber in addition to the fluorocarbon gas that has been conventionally used, so that the number of additional equipment of the apparatus related thereto is increased, and CO is a combustible gas, and Since it is also a toxic gas, the management standards are strict,
This is because such handling requires great care. In particular, since CO has a relatively low ignition point of 651 degrees Celsius, CO always has a risk of ignition or ignition. Therefore, handling before introduction into the reaction chamber,
It is necessary to restrict the flow rate when introducing into the reaction chamber and to restrict the conditions during etching, which is a major obstacle to ensuring safety in the etching process.

[0010]

As described above, a technique of using CO and a mixed gas of fluorocarbon gas as an etching gas has been developed so far, but it is not safe to use this method in an actual process. In securing CO
The flammability problem of is a major obstacle. In the present invention, the following means are used to solve the above problems. That is, a step of placing a semiconductor substrate having a predetermined film formed on an electrode in a reaction chamber, and a step of introducing a fluorocarbon gas containing CO in a composition formula into the reaction chamber,
It is to provide a method of manufacturing a semiconductor device having a dry etching step of applying a high frequency voltage to the electrode to generate plasma in the reaction chamber and etching the predetermined film, and in particular, the reaction gas is CF ₃ FCOCF ₂ ( hexatluo
ropropen oxide) or CF ₃ COCF ₃ (hexatluoroac
etone) makes the present invention more effective.

[0011]

According to the present invention, a fluorocarbon gas containing CO in its composition formula is used as an etching gas in dry etching. As a result, compared with the case where fluorocarbon gas and CO, which have been developed from the past, are used as etching gas, the etching rate and etching rate are comparable to each other, and while maintaining good etching characteristics, CO The fluorocarbon gas included in the formula has no danger of catching fire or ignition under normal dry etching conditions, and its toxicity is not so high as CO. Therefore, handling before introduction into the reaction chamber or in the reaction chamber It is not necessary to consider the restriction of the flow rate at the time of introduction, the restriction of the conditions at the time of etching, etc., and it is assumed that the same level of control as in the case of using the fluorocarbon gas alone as the etching gas is sufficient, as usual.

[0012]

Embodiments of the present invention will be described below. The etching apparatus used in the present invention is the same as the etching apparatus conventionally used, and the apparatus shown in the schematic view of FIG. 1 is used. In FIG. 1, a reaction chamber 1
A wafer 13 to be etched is placed on the side of the cathode electrode 12 in the apparatus 1. The reaction chamber 11 is provided with a gas introduction pipe 14 for introducing a reaction gas and a gas exhaust pipe 15 for exhausting exhaust gas after the reaction. A high frequency power supply 16 for generating plasma is connected to the cathode electrode 12, and an anode electrode 18 connected to a ground voltage 17 is arranged at a position facing the cathode electrode 12. This connection method is called cathode coupling, but a method called anode coupling in which the connection relationship is opposite to the above may be used in some cases.

Next, an example of the etching process in the present invention will be described. In the following description, an etching process for forming a hole of a predetermined width in a silicon oxide film formed on a wafer will be described.

As shown in FIG. 2A, a silicon oxide film 22 is formed on the surface of the cathode electrode 12 in the above-described etching apparatus, and the silicon oxide film 22 is further formed.
A wafer 21 having a resist 23 having a predetermined pattern formed on its surface is placed.

A fluorocarbon gas containing CO, which will be described in detail later, in its composition formula is introduced into the reaction chamber 11 whose atmospheric pressure is maintained at about 1 to 500 mtorr from the gas introduction pipe 14 at about 1 to 500 sccm. After that, a high frequency power source 16 is applied to the cathode electrode 12.
When a voltage of about several hundred kHz to several tens Mhz is applied, the reaction gas is dissociated and a plasma atmosphere is generated. Therefore, a part of the dissociated reaction gas reacts with the silicon oxide film 22 in the portion of the resist 23 not covered by the mask,
Anisotropic etching proceeds by decomposing the silicon oxide film 22, and finally an opening 24 as shown in FIG. 2B is formed in the silicon oxide film 22. The reaction gas whose composition is changed after the reaction is completed is discharged from the gas discharge pipe 15.

The feature of the present invention is that fluorocarbon gas, which is an etching gas that has been developed in the past, and CO.
The point is to use a fluorocarbon gas containing CO itself in its composition formula, instead of the mixed gas of. It should be noted that, as described above, the fluorocarbon gas itself has been conventionally present, but the gas containing CO in its composition formula has not been used as an etching gas.

A specific example of the fluorocarbon gas containing CO in the composition formula is CF ₃ FCOCF ₂ (hexatluoro).
propen oxide) and CF ₃ COCF ₃ (hexatluoroacetone)
) Is typical. The boiling point of the former gas is -42 degrees Celsius.
The latter gas has a boiling point of -26 degrees Celsius and is gasified at room temperature and atmospheric pressure, so that it can be easily introduced into the etching apparatus in a gaseous state. 2 listed above
In addition to the kinds of gases, CF ₃ COF, CF ₃ COCOF, and other gases such as at least F or Cl and C, and CO having a chemical bond can be used in the present invention.

Even when the fluorocarbon gas containing CO in its composition formula is used as the etching gas in the dry etching, compared with the case where the fluorocarbon gas and CO which have been developed in the past are used as the etching gas, It was first discovered by the present inventor that the etching rate and the etching rate were comparable.

Further, the fluorocarbon gas containing CO itself in its compositional formula does not have a risk of catching fire or ignition in a normal dry etching use state, and its toxicity is not so high as that of CO.
Safety management is easier than in the case of using a mixed gas of O, and it is necessary to consider handling before introduction into the reaction chamber, restriction of the flow rate when introducing into the reaction chamber, restriction of etching conditions, etc. However, the same level of control as in the case of using the fluorocarbon gas alone as the etching gas is sufficient as usual.

The fact that the fluorocarbon gas containing CO in its composition formula as described above has the same effect on the etching rate and etching rate as the mixed gas of the fluorocarbon gas and CO in the etching step.
Since CO itself is decomposed from the fluorocarbon gas containing it by the generation of plasma in the reaction chamber, it reacts with CO as a mixed gas with fluorocarbon gas such as CF ₄ or C ₂ F ₆ which does not contain CO in its composition formula. It is understood that it is because it is in the same state as when it was introduced into the room.

Therefore, as in the conventional case, carbon-containing radical species are generated in plasma by C contained in the mixed gas of fluorocarbon gas and CO, and a polymer film is deposited on the wafer to be etched. On the other hand, oxygen in the mixed gas produces oxygen radical species in plasma, which oxidizes and vaporizes the polymerized film, which has the function of lowering the deposition rate of the polymerized film, and CO is more C than O or CO _2.
Since the element ratio of is high, the effect of depositing carbon-based radical species appears strongly, the generation of particles is suppressed, and the etching rate of the silicon oxide film is improved.

Although the embodiments of the present invention have been described above, the dry etching method of the present invention is not limited to etching when forming openings in a silicon oxide film, but also etching of a silicon nitride film or etching of a silicon film. Can also be applied to. Further, the opening formed by the above-described etching process can be used as a contact hole or a via hole with an underlying wiring or a diffusion layer, and also as an etching method of an interlayer film when a buried wiring layer is formed. It goes without saying that you can do it. Further, in order to improve the etching rate, it can be used by mixing with other reaction gas such as Ar. Further, it is of course possible to appropriately select the atmospheric pressure in the reaction chamber, the flow rate of gas, etc. depending on the etching target.

[0023]

According to the present invention, in a dry etching method using plasma, a mixed gas of fluorocarbon gas and CO, which has been developed from before, is used by using a fluorocarbon gas containing CO in the composition formula as an etching gas. As well as having the same etching performance as when using a gas that does not pose a risk of ignition or ignition, the points related to ensuring safety are the same as when using a fluorocarbon gas alone as in the past. Realized the way.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an etching apparatus used in an embodiment of the present invention.

FIG. 2 is a sectional view showing an example of a semiconductor manufacturing process according to the embodiment of the present invention.

[Explanation of symbols]

 11 Reaction Chamber 12 Cathode Electrode 13 Wafer 14 Gas Inlet Pipe 15 Gas Exhaust Pipe 16 High Frequency Power Supply 17 Ground Voltage 18 Anode Electrode 21 Wafer 22 Silicon Oxide Film 23 Resist 24 Opening

Claims (5)

[Claims] 1. A step of placing a semiconductor substrate having a predetermined film formed on an electrode in a reaction chamber, a step of introducing a fluorocarbon gas containing CO in a composition formula into the reaction chamber, and applying a high frequency voltage to the electrode. A method of manufacturing a semiconductor device, comprising a dry etching step of applying a plasma to generate a plasma in the reaction chamber to etch the predetermined film. 2. The reaction gas is CF ₃ FCOCF ₂ (he
xatluoropropen oxide) or CF ₃ COCF ₃ (hexatl
uoroacetone), a method of manufacturing a semiconductor device. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the predetermined film is a silicon oxide film, a silicon nitride film, or a silicon film. 4. A method of manufacturing a semiconductor device having a dry etching step of etching a predetermined film on which an etching mask is formed by the action of a reaction gas introduced into a reaction chamber, wherein the reaction gas contains halide and C. A method of manufacturing a semiconductor device, which comprises using a fluorocarbon gas in which CO is chemically bonded. 5. The predetermined film is placed on an electrode provided in the reaction chamber, plasma is generated in the reaction chamber by applying a voltage to the electrode, and the plasma forms the fluorocarbon gas. 5. CO dissociates from the fluorocarbon gas.
The manufacturing method of the semiconductor device described in the above.