JPH06244152A - Manufacture of semiconductor device and semiconductor device - Google Patents

Abstract

(57) [Summary] [Structure] A fluorocarbon-based gas composed of carbon (C) and fluorine (F), in which the ratio of F to C is 3
The following C ₄ F ₈ , C ₃ F ₈ , C ₂ F ₆ gas, etc.
A method for manufacturing a semiconductor device in which plasma is formed by CR and etching is performed. [Effect] A large amount of free C can be generated from C ₄ F ₈ , C ₃ F ₈ , C ₂ F ₆ gas, etc., and the SiO ₂ film 33 can be decomposed by the free C, so that the SiO ₂ film 33 is separated. The SiN film 31 can be highly selectively etched, and a semiconductor device having an extremely high degree of integration can be easily manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device and a semiconductor device, and more particularly to a method of manufacturing a semiconductor device by selective dry etching of a silicon oxide film with respect to a silicon nitride film, and the method. The present invention relates to a semiconductor device manufactured using the same.

In the following description, carbon is C, fluorine is F, silicon is Si, and oxygen is O.

[0003]

2. Description of the Related Art Etching is an important technique in the manufacturing process of semiconductor devices, and with the miniaturization of semiconductor devices, more precise etching techniques are required. It is difficult to deal with high-precision etching by the conventionally used wet method, and in recent years, a dry etching method using a gas represented by a fluorine compound has been widely adopted.

FIG. 8 shows a conventional LDD (Lightly Doped Drai).
n) In a manufacturing process of a semiconductor device for forming a MOS (Metal Oxide Semiconductor) transistor having a structure,
FIG. 5 is a partial cross-sectional view schematically showing a state of a pre-process for forming a contact hole 60, and 50 in the drawing shows a Si substrate. An isolation insulating film 51 is formed on the Si substrate 50 by a method such as LOCOS, a gate insulating film 52 is formed on the Si substrate 50, and a gate electrode 53 is formed on the gate insulating film 52 using polysilicon or the like. Has been formed. A first insulating film 54 is formed on the gate electrode 53, sidewall insulating films 55 are formed on both side surfaces of the gate electrode 53, and further, an isolation insulating film 51 and a gate insulating film 5 are formed.
2. The second insulating film 56 is laminated on the sidewall insulating film 55 and the first insulating film 54 by using TEOS or the like. Further, a low concentration source region 57 is formed on the Si substrate 50.
a, the high concentration source region 57b and the low concentration drain region 5
8a and the high-concentration drain region 58b are formed by an ion implantation method to form an LDD structure.

In the next step, when the contact hole 60 is formed between the gate electrode 53 and the isolation insulating film 51, first, the end of the isolation insulating film 51 which is in contact with the gate insulating film 52 on the second insulating film 56. A photoresist 59 is formed in a portion except between the portion 51a and the lower end portion 55a of the sidewall insulating film 55. Then, the contact hole 60 is formed by performing a dry etching process on the second insulating film 56 and the gate insulating film 52 using the photoresist 59 as a mask.

FIG. 9 is a cross-sectional view schematically showing a conventional parallel plate type etching apparatus used for the dry etching process, and 71 in the figure shows a reaction chamber. In the reaction chamber 71, two high-frequency electrodes 72 formed in a flat plate shape,
73 are arranged in parallel, and the sample 77 is placed on the high-frequency electrode 73.
Is placed. A high frequency power source 74 is connected to the high frequency electrodes 72 and 73, and the high frequency electrode 72 side is grounded. Further, the gas introduction pipe 7 is provided on the side wall 71a of the reaction chamber 71.
5 is connected to the bottom wall 71b of the reaction chamber 71 and the exhaust pipe 7
A vacuum pump 76 is connected via 6a.

When the contact hole 60 (FIG. 8) is formed using the parallel plate type etching apparatus having such a structure, first, the vacuum pump 76 is driven to exhaust the air in the reaction chamber 71, and then, for example, a fluorocarbon-based material is used. CF ₄ , C
₂ F ₆ , CF ₄ + O ₂ , CF ₄ + H ₂ , or NF
An etching gas such as ₃ , SF ₆ , CHF ₃ or CH ₂ F ₂ is introduced through the gas introduction pipe 75, and the gas pressure in the reaction chamber 71 is adjusted to about 0.1 Torr. Next, high frequency power is applied to the high frequency electrodes 72 and 73 by using the high frequency power source 74, the etching gas is turned into plasma, and the second insulating film 56 in the contact hole 60 portion of the sample 77 is selectively removed by etching. .

Gases used for highly selective etching of silicon nitride (hereinafter referred to as SiN) with respect to SiO ₂ include CHF ₃ , CF ₄ + H ₂ , C.
H ₂ F ₂ , NF ₃ , SF ₆ , CF ₄ + O ₂ etc. are known,
CHF ₃ , CF ₄ + H ₂ and C are used as gases used for etching SiO ₂ highly selectively with respect to Si.
H ₂ F _{2 and the} like are known. CF ₄ and C ₂ F ₆ are known as gases used when SiO ₂ is selectively etched with respect to SiN.

[0009]

In the above-described method for manufacturing a semiconductor device, it is difficult to accurately form the photoresist 59 at a predetermined location due to mask misalignment. Therefore, the photoresist 59 is used as a mask. When performing the etching process, the end portion 51a of the isolation insulating film 51
However, there is a problem that it is difficult to accurately form the contact hole 60 at a position in contact with the lower end portion 55a of the sidewall insulating film 55.

When a conventional parallel plate type etching apparatus is used and CF ₄ , C ₂ F ₆ or the like is used as an etching gas, the etching rate ratio between SiO ₂ and SiN (hereinafter referred to as the selection ratio) is Only about 2. Further, even when C ₃ F ₈ , C ₄ F ₈ or the like having a small F / C ratio is mixed with an oxygen-containing gas, Si of SiO ₂ is used.
The selectivity for N only increases to about 3. Thus, when the selection ratio is about 3, there is a problem that the margin as an etching stopper is small and the SiN film cannot be adopted as an etching stopper.

The present invention has been made in view of the above problems, and the dry etching of the SiO ₂ film with respect to the SiN film can be performed with high selectivity, and the contact can be made even if the mask alignment is slightly loose. It is an object of the present invention to provide a method for manufacturing a semiconductor device and a semiconductor device that can surely obtain a contact by a hole and increase the degree of integration.

[0012]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention is directed to a semiconductor device in which a SiO ₂ film is selectively etched with respect to a SiN film by using gas plasma. In the manufacturing method, a gas containing one or more of a fluorocarbon-based gas composed of C and F, or an oxygen-containing gas or a C containing a gas containing one or more of the fluorocarbon-based gas.
A gas to which at least one of the contained gases is added, wherein the gas is C
(1) is characterized in that a gas having a ratio of F with respect to (F / C) of 3 or less is turned into plasma by electron cyclotron resonance (ECR) for etching (1).

In the method (1) for manufacturing a semiconductor device described above, an exciting coil provided to adjust the magnetic field distribution in the reaction chamber is used to relax the magnetic field divergence and perform plasma transportation (2). ).

A semiconductor device according to the present invention includes a substrate,
A gate insulating film and an isolation insulating film formed on the substrate,
A gate electrode formed on the gate insulating film, a first insulating film formed on the gate electrode and a sidewall insulating film formed in contact with a sidewall of the gate electrode, and the first insulating film And a SiN film formed on most of the isolation insulating film, source / drain regions formed on the substrate with the gate electrode sandwiched therebetween, the first insulating film, the sidewall insulating film, An isolation insulating film and a contact hole formed above the source / drain region are provided, and a step is formed on the first insulating film and the isolation insulating film in the contact hole. (3).

In the method of manufacturing a semiconductor device according to the present invention, a step of forming a SiN film on the gate insulating film, the first insulating film, the sidewall insulating film and the isolation insulating film,
Forming a second insulating film on the N film, and etching the second insulating film, the SiN film, and the gate insulating film in this order to obtain the first insulating film, the sidewall insulating film, and It is characterized by including a step of forming a contact hole above the isolation insulating film and the source / drain regions (4).

In order to solve the problem that it is difficult to manufacture a highly integrated semiconductor device with reliable contact, the inventors of the present invention have formed a conventional isolation insulating film 51 of SiO ₂ and a gate insulating film 52. Sidewall insulating film 5
5, and a semiconductor device having a structure in which a SiN film was formed as an etching stopper between the first insulating film 54 and the second insulating film 56 was studied. In the case of manufacturing this semiconductor device, even if a photoresist is formed with a large mask alignment margin, if the selection ratio of SiO ₂ to SiN is increased, the first insulating film 54 of SiO ₂ becomes the S-type.
It is protected by the iN film. Next, using the photoresist as a mask, the SiN film is removed by etching with a high selection ratio of SiN to SiO ₂ . Further, using the photoresist as a mask, the gate insulating film 52 is removed by etching with a high selection ratio of SiO ₂ to Si. At this time, the first insulating film 54 and the isolation insulating film 51 are also etched at the same time, and the step is formed above them, but the gate electrode is formed by the first insulating film 54 and the sidewall insulating film 55. 53 is surely insulated, and a contact hole is surely formed including both ends of the high concentration source / drain region.

Therefore, the present inventors have conducted research on etching having a high selection ratio of SiO ₂ to SiN, and have completed the method of manufacturing a semiconductor device and the semiconductor device according to the present invention.

[0018]

According to the investigation by the present inventors, when the fluorocarbon-based gas is decomposed by high-density plasma using the ECR plasma device, generation of free F and C is observed by the emission spectrum, and the gas species etc. are changed. When the F / C ratio is changed,
The emission intensity of free C in plasma increases as the F / C ratio decreases. When the F / C ratio is 2, the strength is F /
The strength is approximately four times as strong as when the C ratio is 4. The film formed by these is deposited on the sample. When the deposited film is analyzed by IR (infrared spectroscopic analysis), C is about 30% when the gas has an F / C ratio of more than 3, and C when the gas has an F / C ratio of 3 or less. It becomes about 45%, and the C content rate increases. When these free F and C are deposited as a deposition film on the SiO ₂ film, the free C breaks the bond between Si and O ₂ to combine with O _2, and the free F combines with Si to form Si.
Etch the O ₂ film. On the other hand, even if the free F and C are deposited as a deposition film on the SiN film, the free C rarely breaks the bond between Si and N, so that the etching of the SiN film does not proceed so much. Therefore, when an ECR plasma etching apparatus is used and a fluorocarbon-based gas having an F / C ratio of 3 or less is used as an etching gas, the SiO ₂ film can be highly selectively etched with respect to the SiN film.

When a gas containing oxygen is mixed with the fluorocarbon-based gas, the liberation of C and F is promoted, and the SiO ₂ film can be further highly selectively etched with respect to the SiN film.

When an exciting coil is provided in the reaction chamber of the ECR plasma etching apparatus to form a magnetic field like a mirror, the divergence of the magnetic field is relaxed, and free C is more efficiently transported to the vicinity of the sample.

Method of manufacturing semiconductor device according to the present invention (1)
According to the above, a gas composed of one or more kinds of fluorocarbon-based gas composed of C and F, or at least one of an O ₂ -containing gas and a C-containing gas in a gas composed of one or more kinds of the fluorocarbon-based gas. Since a gas having a ratio of F to C of 3 or less, which is a gas to which C is added, is converted into plasma by electron cyclotron resonance (ECR) for etching, a large amount of free C is generated from the fluorocarbon-based gas. , SiO ₂
The film is decomposed by the free C, and the SiO ₂ film is highly selectively etched with respect to the SiN film.

In the method (1) for manufacturing a semiconductor device described above, in the case where plasma is transported by relaxing the magnetic field divergence by an exciting coil provided for adjusting the magnetic field distribution in the reaction chamber, the fluorocarbon-based gas is used. free C becomes to be transported more efficiently samples from more proceeds more degradation of the SiO ₂ film by the free C, SiO ₂ film is to be more highly selectively etched with respect to the SiN film.

According to the semiconductor device (3) of the present invention, when removing the second insulating film, SiN of SiO ₂ is removed.
When the etching with a high selection ratio to Si is performed, the first insulating film, the sidewall insulating film, and the isolation insulating film become Si.
Since it is protected by the N film, the gate electrode is reliably insulated by the first insulating film and the sidewall insulating film. Next, the SiN film is subjected to etching with a high selection ratio of SiN to SiO ₂ ,
By removing the gate insulating film, the contact hole is formed including both ends of the high-concentration source / drain region. Therefore, even if the photoresist for forming the contact hole is formed relatively loosely, the contact can be surely made, and the semiconductor device having a high degree of integration can be easily obtained.

Method of manufacturing semiconductor device according to the present invention (4)
According to the above, when the second insulating film is removed, the first insulating film, the sidewall insulating film and the isolation insulating film are protected by the SiN film if etching with a high selection ratio of SiO ₂ to SiN is performed. Therefore, the first
The gate electrode is reliably insulated by the insulating film and the sidewall insulating film. Next, SiN SiO
_The above-mentioned SiN is formed by etching with a high selection ratio to ₂
If the film and gate insulating film are removed, the high concentration of the source
The contact hole is formed so as to surely include both ends of the drain region. Therefore, even if the photoresist for forming the contact hole is formed relatively loosely, the contact can be surely made, and the semiconductor device having a high degree of integration can be easily manufactured.

[0025]

EXAMPLES AND COMPARATIVE EXAMPLES Examples of a semiconductor device manufacturing method according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an ECR plasma etching apparatus used in an embodiment of a method for manufacturing a semiconductor device according to the present invention, and 11 in the drawing shows a plasma generation chamber. The quartz glass plate 1 is provided at the center of the upper wall 11a of the plasma generation chamber 11.
A microwave introduction window 12 sealed by 2a is formed. One end of a waveguide 13 is connected to an upper portion of the microwave introduction window 12 and a microwave oscillator 14 is connected to the other end of the waveguide 13. Has been done. Exciting coils 24 are arranged concentrically with the plasma generating chamber 11 and the waveguide 13 connected to the plasma generating chamber 11 so as to surround the plasma generating chamber 11 and the waveguide 13 connected to the plasma generating chamber 11. It is connected.

A reaction chamber 15 is provided below the plasma generation chamber 11.
The plasma generation chamber 11 and the reaction chamber 15 are partitioned by a partition plate 16, and a plasma extraction window 16a is formed in the central portion of the partition plate 16 at a position facing the microwave introduction window 12. . A sample stage 17 is disposed in the reaction chamber 15 at a position facing the plasma extraction window 16a, and a semiconductor substrate 25, which is a sample, is detachably attached to the upper surface of the sample stage 17 by means of electrostatic adsorption or the like. An electrode 18 is embedded in the sample stage 17, the electrode 18 is connected to a high frequency power source 20, a direct current power source 21 is connected to the high frequency power source 20, and one end of the direct current power source 21 is grounded. A vacuum pump 23 is connected to the lower side wall 15b of the reaction chamber 15 via an exhaust pipe 23a, and a gas introduction pipe 22 is connected to the upper side wall 15a of the reaction chamber 15, and an etching gas 26 is fed into the reaction chamber 15. It is being introduced.

Sample 2 was prepared by using the apparatus thus constructed.
When etching 5, the sample 25 is first placed on the sample table, the DC power supply 21 is turned on, and the electrode 18 is electrostatically adsorbed. Next, the vacuum pump 23 is driven to drive the plasma generation chamber 1
After setting 1 and the reaction chamber 15 to a predetermined vacuum degree, the etching gas 26 is introduced into the reaction chamber 15 and set to a predetermined pressure. In addition, the microwave generated by the microwave oscillator 14 is applied to the waveguide 1 while forming a magnetic field by the exciting coil 24.
3. Plasma generation chamber 11 through microwave introduction window 12
Introduce to. In the plasma generation chamber 11 that acts as a cavity resonator for microwaves, the electrons generated by the microwave discharge perform a spiral motion due to the magnetic field formed by the exciting coil 24. For example, for microwaves with a frequency of 2.45 GHz, When a magnetic field of 875 Gauss is formed, electrons undergo cyclotron resonance, and many gas molecules are ionized to generate plasma. A divergent magnetic field whose magnetic flux density decreases as it goes downward is formed in the reaction chamber 15 by the exciting coil 24, and the generated plasma is projected to the periphery of the sample 25 by this divergent magnetic field and the sample 2
5 The surface is etched. Further, during etching, a bias electric field induced in the electrode 18 by the high frequency power source 20 is applied to the surface of the sample 25, so that the kinetic energy of ions,
Control the direction of movement.

Next, as Example (1), using the apparatus shown in FIG. 1, the etching gas 26 is a fluorocarbon-based gas (C ₂ F ₆ , C ₃ F ₈ , C ₄₎ having an F / C ratio of 3 or less. F
_The results of measuring the etching rates of the SiO ₂ film and the SiN film in Sample 25 using ₈ ) will be described. Figure 2
As shown in, the sample is a SiO ₂ film 3 on the Si substrate 30.
3 is formed, and a sample 25a (FIG. 2A) in which a photoresist 32 is formed on a part of the upper surface of the SiO ₂ film 33, and S
The SiN film 31 is formed on the i substrate 30 and the SiN film 3 is formed.
1. Sample 25 having photoresist 32 formed on a part of the upper surface
b (FIG. 2B) was used. As a comparative example, CF ₄ having an F / C ratio of ₄ was used as the etching gas 26. The etching gases 26 were used one by one, and were supplied to the reaction chamber 15 at a flow rate of 40 sccm, and the pressure was set to 1 mTorr. The microwave power supplied was 1 kW. Further, the bias electric field on the samples 25a and 25b is adjusted by adjusting the SiO _{2 with} respect to the photoresist 32.
The etching was performed for each type of etching gas 26 by adjusting the high frequency power of the high frequency power source 20 so that the etching rate ratio of the film 33 was about 6.

FIG. 3 is a graph showing the results of measuring the etching rate in Example (1) and Comparative Example. In FIG. 3, (a) shows the etching rate of the SiO ₂ film 33 and (b) shows the SiN film 31. The etching rate is shown.

As is clear from FIG. 3, in the case of the comparative example using the apparatus shown in FIG. 1 and using the gas having the F / C ratio of more than 3 as the etching gas 26, the SiN film 31 with respect to Si
The etching rate ratio of the O ₂ film 33 was low. On the other hand, in the case of the embodiment (1) using the gas having the F / C ratio of 3 or less, the etching rate of the SiO ₂ film 33 is 300 to 450.
nm / min, and the SiN film 31
It was possible to suppress the etching rate to 70 to 30 nm / min. Thus, according to Example (1), SiN
The etching rate ratio of the SiO ₂ film 33 to the film 31, that is, the selection ratio can be set to 4 to 15, and a large etching rate of SiO ₂ and high selectivity can be realized. In addition, in the pressure range of 0.2 to 5.0 mTorr,
Almost similar results were obtained.

As is clear from this result, in the method of manufacturing the semiconductor device according to the embodiment (1), the fluorocarbon-based gas has a ratio of F to C of 3 or less.
_{Since 4} F ₈ , C ₃ F ₈ and C ₂ F ₆ gases are converted into plasma by ECR for etching, C ₄ F ₈ , C ₃ F
₈ , a large amount of free C can be generated from the C ₂ F ₆ gas, the SiO ₂ film 33 can be efficiently decomposed by the free C, and the SiO ₂ film 33 is highly selective with respect to the SiN film 31. Can be etched.

As Example (2), the apparatus shown in FIG. 1 was used, and CF ₄ + CO (carbon monoxide) with an F / C ratio of 3 or less was used as the etching gas 26, and the SiO ₂ film in Sample 25 was used. The result of measuring the etching rate of the SiN film will be described. The samples are the two types of sample 2 shown in FIG.
5a and 25b, and the etching gas 26 has a flow rate of 40
The flow rate is 20, 30, and 40 in sccm of CF ₄ , respectively.
A mixture of sccm of CO and an F / C ratio adjusted to 3 or less was used. As a comparative example, 40 sccm CF
₄ was mixed with CO at flow rates of 10 and 0 sccm and adjusted so that the F / C ratio exceeded 3. Moreover, the pressure is set to 1 mTorr in any case,
Microwave power supplied was 1 kW. Sample 25
The adjustment of the bias electric field on a and 25b is performed by adjusting the etching rate ratio of the SiO ₂ film 33 to the photoresist 32 to about 6
The high frequency power of the high frequency power source 20 was adjusted so as to be as follows.

FIG. 4 is a graph showing the results of measuring the etching rate in Example (2) and Comparative Example. In FIG. 4, (a) shows the etching rate of the SiO ₂ film 33 and (b) shows the SiN film 31. The etching rate is shown.

As is apparent from FIG. 4, in the case of the comparative example using the apparatus shown in FIG. 1 and using the mixed gas having the F / C ratio of more than 3 as the etching gas 26, the SiO ₂ film 33 with respect to the SiN film 31 is used. The etching rate ratio was low. On the other hand, in the case of the embodiment (2) using the mixed gas having the F / C ratio of 3 or less, the etching rate of the SiO ₂ film 33 is set to 23.
It can be accelerated to 0 to 280 nm / min.
The etching rate of the iN film 31 is 70 to 20 nm / min.
I was able to suppress it. As described above, according to the embodiment (2), the etching rate ratio of the SiO ₂ film 33 to the SiN film 31 can be set to 3 to 14, and a large etching rate of SiO ₂ and high selectivity can be realized. did it.
Note that substantially the same result was obtained in the pressure range of 0.2 to 5.0 mTorr.

As is clear from this result, in the semiconductor device manufacturing method according to the embodiment (2), the fluorocarbon gas CF ₄ is a gas in which CO is added, and the ratio of F to C is 3 or less. Since a certain gas is converted into plasma by ECR for etching, a large amount of free C can be generated from a mixed gas of CF ₄ and CO.
_{The 2} film 33 can be efficiently decomposed by this free C, and the SiO ₂ film 33 can be highly selectively etched with respect to the SiN film 31.

As Example (3), the semiconductor device shown in FIG. 5 is manufactured by using the apparatus shown in FIG. 1 and using a fluorocarbon-based gas having an F / C ratio of 3 or less as the etching gas 26. The method will be described. FIG. 5 is a partial cross-sectional view schematically showing states of steps before and after forming a contact hole in a manufacturing process of a semiconductor device for forming a MOS transistor having an LDD structure according to the embodiment (3). ) Indicates a state before forming the contact hole, (b) indicates a state in the middle of forming, and (c) indicates a state after forming. In the figure, reference numeral 50 denotes a Si substrate, and a low concentration source / drain region 57 is provided on the silicon substrate 50.
a, 58a, high-concentration source / drain regions 57b, 58
b, the isolation insulating film 51 made of SiO ₂ , the gate insulating film 52, the gate electrode 53, the sidewall insulating film 55, and the first insulating film 54 are formed on the Si substrate 50. The insulating film 54 is formed to have a thickness obtained by adding a thickness capable of maintaining electrical characteristics to the thickness of the gate insulating film 52. On the isolation insulating film 51 made of SiO ₂ , the gate insulating film 52, the first insulating film 54 and the sidewall insulating film 55, SiN having a thickness of about 1000Å is formed.
A film 61 is formed, and SiO ₂ is formed on the SiN film 61.
A second insulating film 56 made of is formed. further,
A photoresist 62 having a large mask alignment margin on the second insulating film 56 is formed (FIG. 5A).

Next, using the apparatus shown in FIG. 1, a fluorocarbon-based gas having an F / C ratio of 3 or less is used as the etching gas 26, and the second insulating film 56 made of SiO ₂ is formed using the photoresist 62 as a mask. The SiN film 61 is removed by etching with high selectivity (FIG. 5B). Further, well-known CHF ₃ , CF ₄ + H ₂ , and CH ₂ are used as the etching gas 26.
Using a gas such as F _{2 having} a SiN / SiO ₂ selectivity of about 2,
The SiN film 61 is selectively removed by etching using the photoresist 62 as a mask. When etching the SiN film 61, CHF ₃ , CHF ₃ + CF ₄ or the like may be used for etching by reactive etching (RIE), or CF ₄ + O ₂ , S by isotropic etching.
F ₆ + O _2, etc. may be etched using. afterwards,
The gate insulating film 52 was removed by etching to form a contact hole 63 (FIG. 5C).

As shown in FIG. 5C, the embodiment (3) is used.
In such a semiconductor device, the SiN film 61 formed on most of the first insulating film 54 and the isolation insulating film 51, the first insulating film 54, the sidewall insulating film 55, and the isolation insulating film 51.
And the contact hole 63 formed above the high-concentration source / drain regions 57b and 58b. Therefore, when removing the second insulating film 56, SiN of SiO ₂ is used.
The first insulating film 54, the sidewall insulating film 55, and the isolation insulating film 51 can be protected by the SiN film 61 by performing etching having a high selection ratio with respect to. Therefore, the first
The gate electrode 53 can be surely insulated by the insulating film 54 and the side wall insulating film 55, and the contact hole 63 can be formed so as to surely include both ends of the high-concentration source / drain regions 57b and 58b. You can After removing the second insulating film 56, S
When the SiN film 61 and the gate insulating film 52 are removed by performing etching with a high selection ratio of iN to SiO ₂ , the first
The insulating film 54, the sidewall insulating film 55, and the isolation insulating film 51 are simultaneously etched. At this time, the steps 64a and 64b are formed on the first insulating film 54 and the isolation insulating film 51, but the first insulating film 54 is formed sufficiently thick including the gate insulating film 52 and the etching margin. Therefore, the characteristics of the gate electrode 53 are retained. As described above, even if the mask alignment of the photoresist 62 is performed relatively loosely, the contact can be surely made, and a semiconductor device having a high degree of integration can be easily obtained without impairing the characteristics of the gate electrode 53.

In the method of manufacturing a semiconductor device according to the embodiment (3), the step of forming the SiN film 61 on the gate insulating film 52, the first insulating film 54, the sidewall insulating film 55 and the isolation insulating film 51, The second insulating film 5 is formed on the SiN film 61.
6, the second insulating film 56, the SiN film 6
1. The gate insulating film 52 is etched in this order to form a first insulating film 54, a sidewall insulating film 55, and an isolation insulating film 5.
1 and the step of forming the contact hole 63 above the high-concentration source / drain regions 57b and 58b are included. Therefore, when the second insulating film 56 made of SiO ₂ is removed, the selection ratio of SiO ₂ to SiN is set. By performing high etching, the first insulating film 54, the sidewall insulating film 55, and the isolation insulating film 51 can be protected by the SiN film 61. Therefore, the required insulating film thickness can be secured even when the gate insulating film 52 is removed,
The gate electrode 53 can be surely insulated by the first insulating film 54 and the sidewall insulating film 55, and the contact hole 63 is formed so as to surely include both ends of the high concentration source / drain regions 57b and 58b. be able to. Therefore, even if the mask alignment of the photoresist 62 is performed relatively loosely, the contact can be surely made, and the semiconductor device having a high degree of integration can be easily manufactured.

FIG. 6 is a schematic sectional view showing an ECR plasma etching apparatus used in an embodiment (4) of the method for manufacturing a semiconductor device according to the present invention, and 15 in the drawing shows a reaction chamber. An excitation coil 27 is provided around the outer periphery of the reaction chamber 15, and an excitation coil 28 is provided below the sample table 17 arranged in the reaction chamber 15.
Is connected to a DC power supply (not shown). Since other configurations are similar to those of the apparatus shown in FIG. 1, detailed description thereof will be omitted here.

When etching the sample 25 placed on the sample table 17 using the apparatus configured as described above, first, the vacuum pump 23 is driven to move the plasma generation chamber 11 and the reaction chamber 15 to a predetermined vacuum degree. Then, the etching gas 26 is introduced into the reaction chamber 15 and set to a predetermined pressure.
Further, the microwave generated by the microwave oscillator 14 is introduced into the plasma generation chamber 11 through the waveguide 13 and the microwave introduction window 12 while forming a magnetic field by the exciting coil 24. In the plasma generation chamber 11 that acts as a cavity resonator for microwaves, the electrons generated by the microwave discharge perform a spiral motion due to the magnetic field formed by the exciting coil 24. For example, for microwaves with a frequency of 2.45 GHz, When a magnetic field of 875 Gauss is formed,
The electrons undergo cyclotron resonance, and many gas molecules are ionized to generate plasma. Further, by energizing the exciting coils 27 and 28 from a DC power source (not shown) to form a mirror-like magnetic field in the reaction chamber 15 and relaxing the divergence of the magnetic field generated in the exciting coil 24, the generated plasma is in a high density state. Then, the sample 25 is projected and subjected to etching treatment. Further, a bias electric field induced in the electrode 18 by the high frequency power source 20 is applied to the surface of the sample 25 to control the kinetic energy and the moving direction of the ions.

Next, as Example (4), the apparatus shown in FIG. 6 was used, C ₄ F ₈ + O ₂ was used as the etching gas 26, and a direct current (24 to 32 A) was passed through the exciting coil 27. The results of measuring the etching rate of the SiO ₂ film in Sample 25 and the selection ratio to Si when a magnetic field is formed in a mirror manner will be described. Two kinds of samples 25a and 25b shown in FIG. 2 are used as the samples, and the etching gas 26 is C ₄ F ₈ (40 sccm) having an F / C ratio of 2 and O ₂ (12
sccm) mixed with a pressure of 1 mTorr
Set to. The microwave power supplied was 1 kW. Further, the bias electric field on the samples 25a and 25b is adjusted by adjusting the high frequency power of the high frequency power supply 20 so that the etching rate ratio of the SiO ₂ film 33 to the photoresist 32 is approximately 6, and the magnetic field strength is mirrored. I went every time I changed.

In FIG. 7, a direct current is passed through the exciting coil 27,
The strength of the magnetic field at approximately the center of the sample table 17, SiO ₂
5 is a graph showing the results of measuring the etching rate and the SiN selectivity ratio of FIG. As is clear from FIG. 7, the sample table 1
7, the magnetic field strength in the approximate center is about 320 to 380.
With Gauss, the etching rate of the SiO ₂ film 33 was high, and the etching rate ratio of the SiO ₂ film 33 to the SiN film 31 could be 10 to 25.

As is clear from this result, in the method of manufacturing a semiconductor device according to the embodiment (4), a gas obtained by mixing O ₂ with C ₄ F ₈ having an F / C ratio of 3 or less is turned into plasma by ECR, In addition, since the excitation coil 27 provided to adjust the magnetic field distribution in the reaction chamber 15 relaxes the divergence of the magnetic field to perform plasma transportation, free C can be transported more efficiently, and SiO ₂ The film can be decomposed more efficiently by this free C, and the SiO ₂ film 3
3 can be etched more highly selectively with respect to the SiN film 31.

In the embodiment (2), CF ₄ gas and CO
Although the gases were mixed, in another embodiment, C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ or the like may be used as the fluorocarbon gas, and CO ₂ , O ₂ or the like may be used as the carbon-containing gas and the oxygen-containing gas. It is possible to obtain substantially the same effect as in the case of the embodiment (2).

Further, in the embodiment (3), the apparatus shown in FIG. 1 is used, but in another embodiment, even if the apparatus shown in FIG. 6 is used, the same effect as in the case of the embodiment (3) is obtained. Can be obtained.

Further, in the embodiment (4), the exciting coil 27
Although (FIG. 6) is used, substantially the same effect as in the case of the embodiment (4) can be obtained by using the exciting coil 28 (FIG. 6).

Although the case where the contact hole is formed has been described in the embodiment (1), the embodiment (2), the embodiment (3) and the embodiment (4), it is not limited to the formation of the contact hole. rather, a multilayer structure of the SiO ₂ film and the SiN film may be applied to a structure in which high selectivity etching of the SiO ₂ film / SiN film is required. As described above, and because the selection ratio of SiO ₂ to SiN is increased, it is possible to adopt another process effective for achieving high integration, and it is possible to manufacture a semiconductor device with higher integration. Become.

[0049]

As described in detail above, in the method (1) for manufacturing a semiconductor device according to the present invention, one or two or more kinds of fluorocarbon type gas composed of carbon and fluorine, or the above A gas obtained by adding at least one of an oxygen-containing gas or a carbon-containing gas to a gas composed of one or more fluorocarbon-based gases and having a ratio of fluorine to carbon of 3 or less is converted into plasma by ECR and etched. since the, the fluorocarbon can be generated many free C from a gas, a SiO ₂ film can be decomposed by the liberated C, further highly selectively etched more of the SiO ₂ film relative to the SiN film be able to.

In the method of manufacturing the semiconductor device (1), when the plasma is transported by relaxing the divergence of the magnetic field by the exciting coil provided for adjusting the distribution of the magnetic field in the reaction chamber, the generated liberation is generated. It can be transported more efficiently and C, can be further decomposed more of the SiO ₂ film by the free C, SiO ₂ relative to SiN film
The film can be etched even more selectively.

In the semiconductor device (3) according to the present invention, when removing the second insulating film, Si of SiO ₂ is used.
If etching with a high selection ratio to N is performed, the first
The insulating film and the isolation insulating film can be protected by the SiN film, so that the gate electrode can be reliably insulated by the first insulating film and the sidewall insulating film. Then, the SiN film and the gate insulating film are removed by performing etching having a high selection ratio of SiN to SiO ₂ to form the contact hole including both end portions of the high-concentration source / drain region. be able to. Therefore, even if the photoresist for forming the contact hole is formed relatively loosely, the contact can be surely made, and the semiconductor having a high degree of integration can be easily obtained.

A method of manufacturing a semiconductor according to the present invention (4)
In this case, when removing the second insulating film, SiO ₂
If the film is etched with a high selectivity to SiN,
The first insulating film, the sidewall insulating film, and the isolation insulating film can be protected by the SiN film, so that the gate electrode can be insulated by the first insulating film and the sidewall insulating film. Then SiN SiO ₂
The SiN having a high selection ratio to
If the film and gate insulating film are removed, the high concentration of the source
The contact hole can be formed so as to surely include both ends of the source / drain region having a high concentration in the drain region. Therefore, even if the photoresist for forming the contact hole is formed relatively loosely, the contact can be surely made, and the semiconductor device having a high degree of integration can be easily manufactured. Also, Si
By increasing the selection ratio of O ₂ to SiN, it becomes possible to adopt other steps effective in achieving high integration, and it becomes possible to manufacture a semiconductor device having a higher degree of integration.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an ECR plasma etching apparatus used in an example of a method for manufacturing a semiconductor device according to the present invention.

FIG. 2 is a schematic cross-sectional view showing two kinds of samples used in Examples, (a) shows a SiO ₂ film formed on a Si substrate, and a photoresist is formed on a part of the upper surface of the SiO ₂ film. (B) has a SiN film formed on a Si substrate,
This shows a photoresist formed on a part of the upper surface of the SiN film.

FIG. 3 is a graph showing the results of measuring the etching rate in Example (1) and Comparative Example, in which (a) shows the etching rate of the SiO ₂ film and (b) shows the etching rate of the SiN film. ing.

FIG. 4 is a graph showing the results of measuring the etching rate in Example (2) and Comparative Example, in which (a) shows the etching rate of the SiO ₂ film and (b) shows the etching rate of the SiN film. ing.

FIG. 5 is a partial cross-sectional view schematically showing states before and after forming a contact hole in a manufacturing process of a semiconductor device for forming a MOS transistor having an LDD structure according to an embodiment (3). Shows a state before forming a contact hole, (b) shows a state in the middle of formation, and (c) shows a state after formation.

FIG. 6 is a schematic cross-sectional view showing another ECR plasma etching apparatus used in the method for manufacturing a semiconductor device according to the present invention.

FIG. 7 is a graph showing the results of measuring the magnetic field strength, the SiO ₂ etching rate, and the Si-to-Si selection ratio at approximately the center of the sample table in Example (4).

FIG. 8 is a partial cross-sectional view schematically showing a state of a pre-process of forming a contact hole in a manufacturing process of a semiconductor device in which a conventional MOS transistor having an LDD structure is formed.

FIG. 9 is a cross-sectional view schematically showing a parallel plate type etching apparatus used for a conventional dry etching process.

[Explanation of sign]

10 ECR plasma etching device 25 sample 26 etching gas 31 SiN film 33 SiO ₂ film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Yoneda 4-1-1 Mizuhara, Itami-shi, Hyogo Prefecture LS Electric Co., Ltd. LSE Research Institute (72) Inventor Hiroshi Matsuo 4-1-1 Mizuhara, Itami-shi, Hyogo Mitsubishi Electric Co., Ltd. Kita Itami Plant (72) Inventor Nobuhiko Omori 8-1-1 Tsukaguchi Honcho, Amagasaki City, Hyogo Sanryo Electric Co., Ltd.

Claims (4)

[Claims] 1. A method for manufacturing a semiconductor device in which a silicon oxide film is selectively etched with respect to a silicon nitride film by using gas plasma, wherein one or more fluorocarbon-based gases composed of carbon and fluorine are used. Or a gas containing at least one of an oxygen-containing gas and a carbon-containing gas to a gas consisting of one or more of the fluorocarbon-based gases, wherein the ratio of fluorine to carbon is 3 or less. A method for manufacturing a semiconductor device, which comprises performing plasma etching by cyclotron resonance (ECR) for etching. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the excitation coil provided to adjust the magnetic field distribution in the reaction chamber relaxes the divergence of the magnetic field to carry out plasma transportation. 3. A substrate, a gate insulating film and an isolation insulating film formed on the substrate, a gate electrode formed on the gate insulating film, and a first insulating film formed on the gate electrode. And a sidewall insulating film formed in contact with a sidewall of the gate electrode, a silicon nitride film formed on most of the first insulating film and the isolation insulating film, and the substrate sandwiching the gate electrode. A source / drain region formed on an upper portion, a contact hole formed above the first insulating film, the sidewall insulating film, the isolation insulating film, and the source / drain region. 2. A semiconductor device having a step on the first insulating film and the isolation insulating film. 4. A step of forming a silicon nitride film on the gate insulating film, the first insulating film, the sidewall insulating film and the isolation insulating film, a step of forming a second insulating film on the silicon nitride film, and The second insulating film, the silicon nitride film,
The method further includes performing a step of etching the gate insulating film in order to form a contact hole above the first insulating film, the sidewall insulating film, the isolation insulating film, and the source / drain regions. Manufacturing method of semiconductor device.