JP3272442B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002] 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 technology is required. It is difficult to respond to high-precision etching by a wet method that has been used conventionally, 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 of forming a contact hole 60, in which 50 denotes an 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 by using polysilicon or the like. Is formed. A first insulating film 54 is formed on the gate electrode 53, a sidewall insulating film 55 is 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. A 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, high concentration source region 57b and 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.

As a next step, when a contact hole 60 is formed between the gate electrode 53 and the isolation insulating film 51, first, an end of the isolation insulating film 51 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, a contact hole 60 is formed by performing dry etching 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. In the drawing, reference numeral 71 denotes 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 a sample 77
Is placed. A high-frequency power supply 74 is connected to the high-frequency electrodes 72 and 73, and the high-frequency electrode 72 is grounded. A gas introduction pipe 7 is provided on a side wall 71a of the reaction chamber 71.
5 is connected to the bottom wall 71b of the reaction chamber 71 and an exhaust pipe 7
A vacuum pump 76 is connected via 6a.

When the contact hole 60 (FIG. 8) is formed by using the parallel plate type etching apparatus having the above structure, first, the vacuum pump 76 is driven to exhaust the air in the reaction chamber 71. CF ₄ , C
₂ F ₆ , CF ₄ + O ₂ , CF ₄ + H ₂ , or NF
_3. An etching gas such as SF ₆ , CHF ₃ or CH ₂ F ₂ is introduced from a 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 using a high-frequency power source 74 to convert the etching gas into plasma, thereby selectively etching away the second insulating film 56 at the contact hole 60 in the sample 77. .

Gases used for etching silicon nitride (hereinafter referred to as SiN) with high selectivity to SiO ₂ include CHF ₃ , CF ₄ + H ₂ , C
H ₂ F ₂ , NF ₃ , SF ₆ , CF ₄ + O _{2 and the} like are known,
CHF ₃ , CF ₄ + H ₂ , and C2 are gases used for etching SiO ₂ with high selectivity to Si.
H ₂ F _{2 and the} like are known. In addition, CF ₄ , C ₂ F _{6, and the} like are known as gases used for selectively etching SiO ₂ with respect to SiN.

[0009]

In the above-described method of manufacturing a semiconductor device, it is difficult to accurately form a photoresist 59 at a predetermined location due to misalignment of a mask. Therefore, the photoresist 59 is used as a mask. When performing the etching process, the end 51a of the isolation insulating film 51 is used.
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.

Further, 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 a selectivity) is as follows. Only about two. Further, even when an oxygen-containing gas is mixed with C ₃ F ₈ , C ₄ F _8, or the like having a small F / C ratio, the Si / SiO ₂
The selectivity for N increases only up to about three. As described above, when the selectivity is about 3, the margin as the etching stopper is small, and there is a problem that the SiN film cannot be used as the etching stopper.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to dry-etch a SiO ₂ film with respect to a SiN film with high selectivity. An object of the present invention is to provide a method of manufacturing a semiconductor device and a semiconductor device which can surely obtain a contact by a hole and can 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 method of manufacturing a semiconductor device which selectively etches a SiO ₂ film with respect to a SiN film by using gas plasma. In the production method, the gas containing one or more of the fluorocarbon-based gases composed of C and F, or the gas containing one or more of the fluorocarbon-based gases is added to an oxygen-containing gas or C
A gas to which at least one of the contained gases is added,
A gas having a ratio of F to F (C / C) of 3 or less is converted into plasma by electron cyclotron resonance (ECR) to perform etching and to adjust the magnetic field distribution in the reaction chamber.
Exciting coil provided to reduce magnetic field divergence
It is characterized by performing the plasma transport to the vicinity of the sample Te (1).

[0013]

[0014]

Further, in the method of manufacturing a semiconductor device according to the present invention, there is provided a method of forming a SiN film on a gate insulating film, a first insulating film, a sidewall insulating film, and an isolation insulating film;
Forming a second insulating film made of a silicon oxide film on the N film, and etching the second insulating film, the SiN film, and the gate insulating film in this order to form the first insulating film and the side surface; The method includes a step of forming a contact hole above the wall insulating film, the isolation insulating film, and the source / drain region, and the etching of the second insulating film is performed by using the method (1) ( 2). ).

In order to solve the problem that it is difficult to manufacture a highly integrated semiconductor device with reliable contacts, the present inventors have proposed a conventionally formed isolation insulating film 51 of SiO ₂ , 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 margin for mask alignment, if the selectivity of SiO ₂ to SiN is increased, the first SiO ₂ insulating film 54 is formed of the S
Protected by iN film. Next, using the photoresist as a mask, the SiN film is removed by etching with a high selectivity of SiN to SiO ₂ . Further, using the photoresist as a mask, the gate insulating film 52 is removed by etching with a high selectivity 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 on the first insulating film 54 and the isolation insulating film 51. 53 is reliably insulated, and a contact hole is surely formed including both ends of the high-concentration source / drain region.

The present inventors have conducted research on etching with a high selectivity 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 a fluorocarbon-based gas is decomposed by high-density plasma using an ECR plasma apparatus, generation of free F and C is observed by an emission spectrum, and the gas type is changed. By changing the F / C ratio,
As the value of the F / C ratio decreases, the emission intensity of free C in the plasma increases. When the F / C ratio is 2, the strength is F /
This is approximately four times the intensity when the C ratio is 4. The films formed by these are deposited on the sample. When this deposited film is analyzed by IR (infrared spectroscopy), C is approximately 30% when the gas has an F / C ratio of more than 3, and C is approximately 30% when the gas has an F / C ratio of 3 or less. It becomes approximately 45%, and the C content increases. When these free F and C are deposited on the SiO ₂ film as a deposit film, the free C breaks the bond between Si and O ₂ and combines with O _2, and 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 on the SiN film as a deposition film, the free C hardly cuts the bond between Si and N, and therefore the etching of the SiN film does not proceed very 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 etched with high selectivity with respect to the SiN film.

Further, 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 etched with high selectivity with respect to the SiN film.

Further, 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 reduced, and free C is more efficiently transported to the vicinity of the sample.

A method for manufacturing a semiconductor device according to the present invention (1)
According to the present invention, at least one of an O ₂ -containing gas or a C-containing gas is added to a gas composed of one or more of a fluorocarbon-based gas composed of C and F, or a gas composed of one or more of the fluorocarbon-based gases. Is added to the gas, and a gas having a ratio of F to C of 3 or less is converted into plasma by ECR and etching is performed, so that a large amount of free C is generated from the fluorocarbon-based gas, and the SiO ₂ film is formed. The SiO ₂ film is decomposed by the free C, and is etched selectively with respect to the SiN film. In addition, the excitation coil generates a magnetic field.
Since plasma transport is performed near the sample with reduced dispersion,
Free C samples more efficiently from fluorocarbon gas
And the decomposition of the SiO ₂ film
C further advances the SiO ₂ film with respect to the SiN film.
Thus, the etching is more selectively performed.

[0022]

[0023]

[0024] According to the method of manufacturing a semiconductor device according to the present invention (2), when removing the second insulating film of silicon oxide film, if Hodokose high selection ratio etching of SiO ₂ to SiN said The first insulating film, the sidewall insulating film, and the isolation insulating film are protected by the SiN film, so that the gate electrode is reliably insulated by the first insulating film and the sidewall insulating film. . Next, if the SiN film and the gate insulating film are removed by performing etching with a high selection ratio of SiN to SiO ₂ , the contact hole is formed including both ends of the high-concentration source / drain regions. The Rukoto. Therefore, even if the photoresist for forming the contact hole is formed relatively loosely, the contact can be reliably obtained, and a semiconductor device with a high degree of integration can be easily manufactured.

[0025]

Embodiments and Comparative Examples Hereinafter, embodiments of a method of manufacturing a semiconductor device according to the present invention will be described 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 of manufacturing a semiconductor device according to the present invention. In the figure, reference numeral 11 denotes a plasma generation chamber. A 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 the upper portion of the microwave introduction window 12, and a microwave oscillator 14 is connected to the other end of the waveguide 13. Have been. An excitation coil 24 is disposed concentrically with the plasma generation chamber 11 and one end of the waveguide 13 connected to the plasma generation chamber 11 so as to surround them. The excitation coil 24 is connected to a DC power supply (not shown). It is connected.

A reaction chamber 15 is located 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 16 a is formed at the center 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 as a sample is detachably mounted on the upper surface of the sample stage 17 by means such as electrostatic attraction. An electrode 18 is embedded in the sample table 17, the electrode 18 is connected to a high-frequency power supply 20, a DC power supply 21 is connected to the high-frequency power supply 20, and one end of the DC power supply 21 is grounded. A vacuum pump 23 is connected to a lower side wall 15b of the reaction chamber 15 via an exhaust pipe 23a, and a gas introduction pipe 22 is connected to an upper side wall 15a of the reaction chamber 15, so that an etching gas 26 is supplied to the reaction chamber 15. It is being introduced.

A sample 2 was prepared by using the apparatus thus constructed.
When etching 5, first, the sample 25 is placed on the sample stage, and the DC power supply 21 is turned on so that the electrode 18 is electrostatically attracted. Next, the vacuum pump 23 is driven, and the plasma generation chamber 1 is turned on.
After the first and reaction chambers 15 are set to a predetermined degree of vacuum, an etching gas 26 is introduced into the reaction chamber 15 and set to a predetermined pressure. Further, while generating a magnetic field by the excitation coil 24, the microwave generated by the microwave oscillator 14 is applied to the waveguide 1.
3. Plasma generation chamber 11 through microwave introduction window 12
Introduce to. In the plasma generation chamber 11 acting as a cavity resonator for microwaves, electrons generated by microwave discharge perform spiral motion by a magnetic field formed by the exciting coil 24. For example, for a microwave having 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. In the reaction chamber 15, a divergent magnetic field whose magnetic flux density decreases as it goes downward is formed by the exciting coil 24, and the generated plasma is projected around the sample 25 by this divergent magnetic field, and
5 Surface is etched. Further, at the time of etching, a bias electric field induced on the electrode 18 by the high-frequency power supply 20 is applied to the surface of the sample 25, and the kinetic energy of ions,
Control the direction of movement.

Next, as an embodiment (1), using the apparatus shown in FIG. 1, a fluorocarbon-based gas (C ₂ F ₆ , C ₃ F ₈ , C ₄₎ having an F / C ratio of 3 or less was used as the etching gas 26. F
_The result of measuring the etching rates of the SiO ₂ film and the SiN film in the sample 25 using ₈ ) will be described. FIG.
As shown in the figure, the sample is a SiO ₂ film 3 on a Si substrate 30.
3 and a sample 25a (FIG. 2A) in which a photoresist 32 was formed on a part of the upper surface of the SiO ₂ film 33;
An SiN film 31 is formed on an i-substrate 30 and the SiN film 3
1. Sample 25 having a photoresist 32 formed on a part of the upper surface
b (FIG. 2 (b)). As a comparative example, CF ₄ having an F / C ratio of ₄ was used as the etching gas 26. The etching gas 26 was used one by one and 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. Adjustment of the bias electric field on the samples 25a and 25b is performed by using SiO ₂ for the photoresist 32.
The etching was performed for each type of the etching gas 26 by adjusting the high frequency power of the high frequency power supply 20 so that the etching rate ratio of the film 33 became approximately 6.

FIGS. 3A and 3B are graphs showing the results of the measurement of the etching rate in Example (1) and Comparative Example. FIG. 3A shows the etching rate of the SiO ₂ film 33, and FIG. The etching rate is shown.

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

As is apparent from the results, in the method of manufacturing the semiconductor device according to the embodiment (1), the method of manufacturing the semiconductor device is a fluorocarbon-based gas having a ratio of F to C of 3 or less.
_Since 4F 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.

[0032] As Example 2, using the apparatus shown in FIG. 1, F / C ratio using the 3 following CF ₄ + CO (carbon monoxide) in the etching gas 26, SiO ₂ film in the sample 25 The result of measuring the etching rate of the SiN film will be described. The samples are the two types of samples 2 shown in FIG.
5a and 25b, and the etching gas 26 has a flow rate of 40.
Flow rates of 20, 30, and 40 were respectively applied to sccm CF _4.
A mixture in which sccm of CO was mixed and the F / C ratio was adjusted to 3 or less was used. As a comparative example, 40 sccm CF
₄ , a mixture was used in which CO was mixed at a flow rate of 10.0 sccm and the F / C ratio was adjusted to exceed 3. In each case, the pressure was set to 1 mTorr,
Microwave power provided 1 kW. Sample 25
The adjustment of the bias electric field on the a and 25b is performed when the etching rate ratio of the SiO ₂ film 33 to the photoresist 32 is about 6
The etching was performed for each mixing ratio of the etching gas 26 by adjusting the high frequency power of the high frequency power supply 20 such that

FIGS. 4A and 4B are graphs showing the results of measuring the etching rate in Example (2) and Comparative Example. FIG. 4A shows the etching rate of the SiO ₂ film 33, and FIG. 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 a mixed gas having an F / C ratio exceeding 3 as the etching gas 26, the SiO ₂ film 33 with respect to the SiN film 31 was used. Had a low etching rate ratio. 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.
0 to 280 nm / min.
The etching rate of the iN film 31 is set to 70 to 20 nm / min.
Was able to be suppressed. 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 and high selectivity of SiO ₂ can be realized. did it.
Note that substantially the same results were obtained in the pressure range of 0.2 to 5.0 mTorr.

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

Next, as an embodiment (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 a state 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). () Shows the state before the contact hole is formed, (b) shows the state during the formation, and (c) shows the state after the formation. In the figure, reference numeral 50 denotes a Si substrate, and a low-concentration source / drain region 57 is provided above the silicon substrate 50.
a, 58a, high concentration source / drain regions 57b, 58
b, an isolation insulating film 51 made of SiO ₂ , a gate insulating film 52, a gate electrode 53, a sidewall insulating film 55, and a first insulating film 54 are formed on a 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. Further, on the isolation insulating film 51, the gate insulating film 52, the first insulating film 54, and the sidewall insulating film 55 made of SiO ₂ , SiN having a thickness of about 1000 ° is formed.
A film 61 is formed, and SiO ₂ is formed on the SiN film 61.
A second insulating film 56 is formed. further,
A photoresist 62 is formed on the second insulating film 56 with a large margin for mask alignment (FIG. 5A).

Next, using the apparatus shown in FIG. 1, a second insulating film 56 made of SiO ₂ is formed by using a fluorocarbon-based gas having an F / C ratio of 3 or less as an etching gas 26 and using a photoresist 62 as a mask. The SiN film 61 is selectively removed by etching (FIG. 5B). Further, the well-known CHF ₃ , CF ₄ + H ₂ , CH ₂
Using a gas having a SiN / SiO ₂ selectivity of about ₂ such as F ₂ ,
The SiN film 61 is selectively etched away using the photoresist 62 as a mask. When the SiN film 61 is etched, reactive etching (RIE) may be performed using CHF ₃ , CHF ₃ + CF ₄ or the like, or CF ₄ + O ₂ , S may be etched by isotropic etching.
Etching may be performed using F ₆ + O ₂ or the like. 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)
In such a semiconductor device, the SiN film 61 formed over 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 high concentration source and drain regions 57 b, is provided with the contact hole 63 formed above the 58b, when removing the second insulating film 56, the SiO ₂ SiN
By performing etching with a high selectivity with respect to the first insulating film 54, the side wall insulating film 55, and the isolation insulating film 51, the SiN film 61 can be protected. Therefore, the first
The gate electrode 53 can be reliably insulated by the insulating film 54 and the sidewall insulating film 55, and the contact hole 63 is formed so as to include both ends of the high-concentration source / drain regions 57b and 58b. Can be. After removing the second insulating film 56, S
When removing the SiN film 61 and the gate insulating film 52 by performing etching with a high selectivity of iN to SiO ₂ , the first
Of the insulating film 54, the side wall insulating film 55, and the isolation insulating film 51 are simultaneously etched. At this time, steps 64a and 64b are formed on the first insulating film 54 and the isolation insulating film 51, and 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 maintained. Thus, even if the photoresist 62 is masked relatively loosely, the contact can be reliably established, and a highly integrated semiconductor device 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), a step of forming a SiN film 61 on a gate insulating film 52, a first insulating film 54, a side wall insulating film 55, and an isolation insulating film 51, Second insulating film 5 on SiN film 61
Forming the second insulating film 56 and the SiN film 6
1, the gate insulating film 52 is etched in this order, the first insulating film 54, the side wall insulating film 55, and the isolation insulating film 5
1 and the step of forming the contact hole 63 above the high-concentration source / drain regions 57b and 58b. Therefore, when the second insulating film 56 made of SiO ₂ is removed, the selectivity of SiO ₂ to SiN is reduced. 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, even when removing the gate insulating film 52, a required insulating film thickness can be secured,
The gate electrode 53 can be reliably insulated by the first insulating film 54 and the sidewall insulating film 55, and the contact hole 63 is formed so as to securely include both ends of the high-concentration source / drain regions 57b and 58b. be able to. Therefore, even if the photoresist 62 is relatively loosely aligned, the contact can be reliably established, and a highly integrated semiconductor device can be easily manufactured.

FIG. 6 is a schematic sectional view showing an ECR plasma etching apparatus used in the embodiment (4) of the method of manufacturing a semiconductor device according to the present invention. In FIG. 6, reference numeral 15 denotes 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 provided in the reaction chamber 15.
Are connected to a DC power supply (not shown). The other configuration is the same as that of the apparatus shown in FIG. 1, and the detailed description is omitted here.

When the sample 25 placed on the sample stage 17 is etched by using the apparatus configured as described above, first, the vacuum pump 23 is driven, and the plasma generation chamber 11 and the reaction chamber 15 are evacuated to a predetermined vacuum level. After that, the etching gas 26 is introduced into the reaction chamber 15 and set to a predetermined pressure.
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 a magnetic field is formed by the excitation coil 24. In the plasma generation chamber 11 acting as a cavity resonator for microwaves, electrons generated by microwave discharge perform spiral motion by a magnetic field formed by the exciting coil 24. For example, for a microwave having 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 excitation coils 27 and 28 from a DC power supply (not shown), a magnetic field is formed in the reaction chamber 15 as a mirror, and the degree of divergence of the magnetic field generated in the excitation coil 24 is reduced. Is projected on the sample 25 to perform an etching process. In addition, a bias electric field induced on the electrode 18 by the high frequency power supply 20 is applied to the surface of the sample 25 to control the kinetic energy and direction of the ions.

Next, as an embodiment (4), the apparatus shown in FIG. 6 is used, C ₄ F ₈ + O ₂ is used as the etching gas 26, and a DC current (24 to 32 A) is applied to the exciting coil 27. The results of measuring the etching rate of the SiO ₂ film in the sample 25 and the selectivity to Si when the magnetic field is formed as a mirror 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 obtained by adding O ₂ (12 sc) to C ₄ F ₈ (40 sccm) having an F / C ratio of 2.
sccm) and a pressure of 1 mTorr
Set to. The microwave power supplied was 1 kW. 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 with respect to the photoresist 32 becomes approximately 6, so that the magnetic field intensity is mirrored. I went every time I changed.

FIG. 7 shows that a DC current is applied to the exciting coil 27,
The intensity of the magnetic field at a substantially central portion on the sample stage 17, SiO ₂
3 is a graph showing the results of measuring the etching rate and the selectivity ratio to SiN of FIG. As is clear from FIG.
7 is approximately 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 set to 10 to 25.

As is apparent from the results, 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 plasma is transported by reducing the divergence of the magnetic field by the excitation coil 27 provided for adjusting the magnetic field distribution in the reaction chamber 15, free C can be transported more efficiently, and SiO ₂ can be transported. The film can be more efficiently decomposed by this free C, and the SiO ₂ film 3
3 can be more selectively etched with respect to the SiN film 31.

In the embodiment (2), CF ₄ gas and CO
Although the gas was mixed, in another embodiment, C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ or the like is used as a fluorocarbon gas, and CO ₂ or O ₂ is used as a carbon-containing gas and an oxygen-containing gas. Thus, substantially the same effects as in the case of the embodiment (2) can be obtained.

In the embodiment (3), the apparatus shown in FIG. 1 is used. However, in another embodiment, even when the apparatus shown in FIG. 6 is used, substantially the same effects as in the case of the embodiment (3) are obtained. Can be obtained.

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

In the embodiments (1), (2), (3), and (4), the case where the contact hole is formed has been described, but it is not necessarily 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, since the selectivity of SiO ₂ to SiN is increased, it is possible to employ other processes that are effective in achieving high integration, and it is possible to manufacture a semiconductor device with higher integration. Become.

[0049]

As described above in detail, in the method (1) for manufacturing a semiconductor device according to the present invention, a gas comprising one or more of a fluorocarbon-based gas composed of carbon and fluorine; A gas obtained by adding at least one of an oxygen-containing gas or a carbon-containing gas to a gas comprising one or more of a fluorocarbon-based gas and having a ratio of fluorine to carbon of 3 or less is converted into a plasma by ECR and etched. Is performed, a large amount of free C can be generated from the fluorocarbon-based gas, the SiO ₂ film can be decomposed by the free C, and the SiO ₂ film is more selectively etched with respect to the SiN film. be able to. The magnetic field distribution in the reaction chamber
Excitation coil provided to adjust
Plasma transport is performed near the sample with a reduced degree of
The above-mentioned free C can be transported more efficiently.
The SiO ₂ film is further decomposed by the free C
And a SiO ₂ film can be further applied to the SiN film.
Highly selective etching can be performed.

[0050]

[0051]

In the method ( 2 ) for manufacturing a semiconductor device according to the present invention, when the second insulating film made of a silicon oxide film is removed, etching is performed with a high selectivity of the SiO ₂ film to SiN. For example, 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. . Next, if the SiN film and the gate insulating film are removed by performing etching with a high selection ratio of SiN to SiO ₂ , the contact holes are formed including both ends of the high-concentration source / drain regions. be able to. Therefore, even if the photoresist for forming the contact hole is formed relatively loosely, the contact can be reliably established, and a highly integrated semiconductor device can be easily manufactured. Further, by increasing the selectivity of SiO ₂ to SiN, it is possible to employ other steps effective for achieving high integration, and it is possible to manufacture a semiconductor device with a higher degree of integration.

[Brief description of the drawings]

FIG. 1 is a schematic 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.

FIG. 2 is a schematic cross-sectional view showing two types of samples used in an embodiment. FIG. 2A is a diagram in which a SiO ₂ film is formed on a Si substrate, and a photoresist is formed on a part of the upper surface of the SiO ₂ film. (B), a SiN film is formed on a Si substrate,
The figure shows that a photoresist is 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, where (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, where (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 a state before and after a step of 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 during formation, and (c) shows a state after formation.

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

FIG. 7 is a graph showing the results of measuring the intensity of a magnetic field, the etching rate of SiO ₂ , and the selectivity to Si at a substantially central portion on a sample stage in Example (4).

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

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

[Description of sign]

Reference Signs List 10 ECR plasma etching apparatus 25 sample 26 etching gas 31 SiN film 33 SiO ₂ film

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Yoneda 4-1-1 Mizuhara, Itami-shi, Hyogo Mitsubishi Electric Corporation LSI Research Institute (72) Inventor Hiroshi Matsuo 4-1-1 Mizuhara, Itami-shi, Hyogo Address: Mitsubishi Electric Corporation, Kita Itami Works (72) Inventor: Nobuhiko Omori 8-1-1, Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture Mitsubishi Electric Corporation Production Technology Research Institute (56) References JP-A-4-110469 (JP) JP-A-4-106929 (JP, A) JP-A-4-239723 (JP, A) JP-A-5-13376 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H01L 21/3065 H01L 21/336

Claims (2)

(57) [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 a gas plasma, wherein one or more of a fluorocarbon-based gas composed of carbon and fluorine is used. A gas obtained by adding at least one of an oxygen-containing gas or a carbon-containing gas to one or more of the above fluorocarbon-based gases, and having a fluorine to carbon ratio of 3 or less. It is installed to perform plasma etching by cyclotron resonance (ECR) and to adjust the magnetic field distribution in the reaction chamber.
Near the sample by reducing the divergence of the magnetic field
A method for manufacturing a semiconductor device, comprising: performing plasma transport on a substrate. 2. A step of forming a silicon nitride film on a gate insulating film, a first insulating film, a sidewall insulating film and an isolation insulating film, and forming a second insulating film made of a silicon oxide film on the silicon nitride film. Forming and etching the second insulating film, the silicon nitride film, and the gate insulating film in this order to form the first insulating film, the sidewall insulating film, the isolation insulating film, and the source / drain regions. Forming a contact hole above,
A method for manufacturing a semiconductor device, comprising: etching the insulating film according to the method according to claim 1.