JP2001127039A - Manufacturing method of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dissolve the problems in conventional manufacturing method such as not only the flaking of a silicon film but also the drop in selectivity with resist, the peeling of the deposition at one sidewall of an etching chamber, etc., for the selectivity between the silicon film and the nitride film drops when the flow rate of oxygen is increased to raise the drillability in etching of a nitride film, using CHF3/O2/Ar mixed gas for removal of the nitride film for opening of a contact, in the element structure which has a nitride film on the silicon film including a silicon substrate. SOLUTION: When C4F8/CH2F2/Ar/O2 mixed gas is used for etching of a nitride film 4, the etching of the nitride film 4 is accelerated, and also since CHxFY gas is one which is high in deposition effect, the selectivity to a silicon substrate 1 rises, and further the etching can be made continuously in roughly the same etching gas as that for the interlayer oxide film covering the nitride film 4, so stable etching excellent in productivity becomes possible.

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 more particularly to a method of forming a contact for connecting a device having a structure in which a nitride film and an oxide film are formed on a silicon film.

[0002]

2. Description of the Related Art In recent years, in the field of semiconductor devices, progress has been made more and more, for example, ultra-fine LSIs have been miniaturized, and it has become difficult to secure an alignment margin for photolithography technology in a contact forming process. Therefore,
In a contact formation process, a self-aligned contact (SAC) technique of a contact etching technique in which a gate electrode is covered with a nitride film and a nitride film is used as a stopper film has been widely used.

[0003]

However, in the self-aligned contact process, the gate electrode is covered with a nitride film, which is an insulating film, and an interlayer insulating film such as an oxide film is covered thereon. Therefore, it is necessary to form a contact on the interlayer insulating film by contact etching and remove the nitride film. To remove the nitride film after this contact etching, a conventional CHF3 / O ₂
However, as the aspect ratio of the contact becomes higher, it is necessary to increase the oxygen flow rate in order to increase the removability in the nitride film etching step. Therefore, the selectivity between the capacitance polysilicon plate or silicon substrate and the nitride film exposed during the etching of the nitride film is reduced, and not only the penetration of the capacitance polysilicon and the removal of the silicon substrate but also the contact due to the reduced selectivity with the resist. There were problems such as an increase in diameter, generation of dust due to the deposition of deposition deposited on the side walls of the etching chamber, and instability of the process due to a change in a chamber atmosphere due to a difference in an etching gas system between a contact etching step and a nitride film etching step.

It is an object of the present invention to improve the selectivity between resist and silicon in dry etching of an interlayer film having a laminated structure of a nitride film and an oxide film, and to suppress generation of dust and reduce the amount of dust. It is an object of the present invention to provide a method for manufacturing a semiconductor device which enables high productivity without changing the atmosphere.

[0005]

According to a method of manufacturing a semiconductor device of the present invention, a laminated film including a nitride film as a lower layer and an oxide film as an upper layer is formed above a substrate, and the oxidized film is formed using a first etching gas. A method for manufacturing a semiconductor device, comprising: selectively removing a film to form an opening in the oxide film; and etching and removing the nitride film through the opening using a second etching gas. The gas is Cx
It is characterized by comprising a mixed gas containing Fy as a main reaction gas, wherein CxFy of the second etching gas is C ₃ F ₆ , C ₃
Any one of ₄ F ₆ , C ₄ F ₈ , C ₅ F ₈ ,
The second etching gas may be CH ₂ F ₂ , CH ₃ F, CH ₃
Any one of Br, NH ₃ , C ₂ H ₅ OH, and CH ₃ OH may be included as an additive gas, or the second etching gas may include any one of CO and CO _2. Is included.

In the above method for manufacturing a semiconductor device,
The first etching gas is a mixed gas containing CxFy as a main reaction gas, which is the same as the main reaction gas of the second etching gas, and the first etching gas is a mixed gas containing CxFy as an additional gas.
O, wherein one of the gas of the CO _2, the first etching gas and the second etching gas includes both Ar and O _2, is that.

Finally, in the above-described method for manufacturing a semiconductor device, the etching step using the second etching gas includes:
Following the etching process using the first etching gas, the first etching is performed continuously in the same chamber as the first etching.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a first embodiment of the present invention will be described with reference to FIGS. The present embodiment shows an example of contact etching in the case of a DRAM having a tantalum oxide film or the like and a large contact aspect ratio, and FIG. 1 shows a method of manufacturing a semiconductor device before and after a contact etching chip. It is sectional drawing shown in order.

As shown in FIG. 1A, a silicon substrate 1
A polysilicon gate 2 constituting a gate electrode thereon, tungsten silicide (WSi) 3 and a nitride film 4 covering the same, an interlayer oxide film 5 covering the silicon substrate 1 and the nitride film 4, and a capacitor provided in the interlayer oxide film 5 Are formed, and a pattern having the contacts 11 is transferred to the photoresist by photolithography to form a photoresist 8.

Next, as shown in FIG.
Using an IE (Reactive Ion Etching) dry etching apparatus, using the photoresist 8 as a mask, etching (just etching) up to the thickest film thickness of the interlayer oxide film 5 is performed using C ₄ F ₈ / CO / Ar / O _2.
Dry etching is performed with the mixed gas 9. The condition at this time is
Under a pressure of 5.33 Pa, 20 sccm of C ₄ F ₈
40 sccm, Ar 500 sccm, O ₂ 9 sc
cm, a high frequency power of 27 MHz and 2200 W is applied to the upper electrode, a high frequency power of 800 kHz and 1400 W is applied to the substrate, and the distance between the upper electrode and the lower electrode is set to 20 mm.
mm and the substrate temperature was -20 ° C. as a result,
The etching rate of the interlayer oxide film 5 is 730 nm / mi
n, the etching rate of the photoresist is 79 nm / m
In, the etching rate ratio (selection ratio) between the interlayer oxide film 5 and the photoresist 8 is about 9 times.

In the etching of the interlayer oxide film,
It is effective to add CO to the mixed gas in order to make the etching gas permeate into the contact having a high aspect ratio.

Subsequently, as shown in FIG. 1C, the nitride film 4 is dry-etched with a mixed gas 10 of C ₄ F ₈ / CH ₂ F ₂ / Ar / O ₂ . The condition at this time is 5.33P pressure.
a, 10 sccm of C ₄ F ₈ and ₂₀ sc of CH ₂ F ₂
cm, Ar flow of 500 sccm, O ₂ flow of 15 sccm, high frequency power of 27 MHz, 2200 W is applied to the upper electrode, high frequency power of 800 kHz, 1400 W is applied to the substrate, and the distance between the upper electrode and the lower electrode is set to 20 mm. Then, the substrate temperature was set to −20 ° C. As a result, the etching rate of the nitride film 4 is 610 nm / min, the etching rate of the interlayer oxide film 5 is 570 nm / min, the etching rate of the photoresist is 34 nm / min, and the etching rates of the silicon substrate 1 and the capacitance polysilicon plate 7 are 3 nm / min. min, the etching rate ratio (selection ratio) between the nitride film 4 and the interlayer oxide film 5 is about 1.1 times, and the etching rate ratio (selection ratio) between the nitride film 4 and the silicon substrate 1 and the capacitance polysilicon plate 7 is about 200 times. The etching rate ratio (selection ratio) between the interlayer oxide film 5 and the silicon substrate 1 and the capacitance polysilicon plate 7 was about 190 times. Further, the etched shape became anisotropic.

Here, although the etching rate ratio (selectivity) of the nitride film to the interlayer oxide film is as low as about 1.1 times, the etching of the nitride film is not limited to the removal of the nitride film but also to the etching process of the interlayer oxide film. Additional etching (overetching) to just etching of interlayer oxide film
Also plays the role of.

According to the first embodiment of the present invention, in the etching step of the nitride film, C and H of CHxFy are changed to N of the nitride film by adding a gas containing a hydrogen atom such as CHxFy gas to the fluorocarbon gas. Combined with C-N
And the generation of N—H promote the etching of the nitride film.

Further, since the CHxFy gas is a gas having a high deposition effect, the selectivity to silicon is improved, and the etching gas system for the interlayer oxide film used in the contact etching step is substantially the same as the etching gas system for the nitride film etching step. Since the same etching gas system is used, stable etching can be performed without changing the atmosphere of the etching chamber.

Next, a second embodiment of the present invention will be described.
This will be described with reference to FIGS. In this embodiment,
SRAM with not so large contact aspect ratio
FIG. 2 is a cross-sectional view showing a method of manufacturing a semiconductor device before and after a contact etching chip in the order of steps.

As shown in FIG. 2A, a silicon substrate 3
A polysilicon gate 32 constituting a gate electrode on 1;
A tungsten silicide (WSi) 33 and side walls 36 for protecting the side surfaces thereof, a nitride film 34 covering the silicon substrate 31 and the gate electrode, and an interlayer oxide film 35 covering the nitride film 34 are formed. The pattern having 41 is transferred to a photoresist to form a photoresist 38.

Next, as shown in FIG.
Using an IE (Reactive Ion Etching) dry etching apparatus, etching (just etching) up to the thickness of the interlayer oxide film 35 is performed with a C ₄ F ₈ / Ar / O ₂ mixed gas plasma 39 using the photoresist 38 as a mask. Etch. The conditions at this time are as follows: under a pressure of 6.67 Pa, 7 sccm of C ₄ F ₈ and A
r is flowed at 600 sccm, O ₂ is flowed at ₂ sccm, a high frequency power of 27 MHz and 2000 W is applied to the upper electrode, a high frequency power of 800 kHz and 800 W is applied to the substrate, and a distance between the upper electrode and the lower electrode is set to 24 mm. The substrate temperature was set to + 20 ° C. As a result, the etching rate of the interlayer oxide film 35 is 420 nm / min, the etching rate of the photoresist is 28 nm / min,
Etching rate ratio between photoresist and photoresist 38 (selection ratio)
Is about 15 times, and the etching rate ratio (selectivity) between the interlayer oxide film 35 and the nitride film 34 is about 20 times.

Here, in the etching of the interlayer oxide film, the aspect ratio of the contact is not as high as in the first embodiment, and it is not necessary to add CO to the mixed gas.

Subsequently, as shown in FIG. 2C, the nitride film 34 is dry-etched with a mixed gas 40 of C ₄ F ₈ / CH ₂ F ₂ / Ar / O ₂ . The condition at this time is a pressure of 5.33.
Under Pa, 10 sccm of C ₄ F ₈ and 20 s of CH ₂ F ₂
ccm, Ar flow 500 sccm, O ₂ flow 15 sccm, 27 MHz, 2200 W high frequency power is applied to the upper electrode, 800 kHz, 1400 W high frequency power is applied to the substrate, and the distance between the upper electrode and the lower electrode is set to 20 mm. Then, the substrate temperature was set to + 20 ° C. As a result, the etching rate of the nitride film 34 is 610 nm / min, the etching rate of the interlayer oxide film 35 is 570 nm / min, the etching rate of the photoresist is 34 nm / min, the etching rate of the silicon substrate 31 is 3 nm / min. Etching rate ratio (selectivity) of interlayer oxide film 35
Is about 1.1 times, the etching rate ratio (selectivity) between the nitride film 34 and the silicon substrate 31 is about 200 times, and the interlayer oxide film 35
And the etching rate ratio (selection ratio) of the silicon substrate 31 was about 190 times. Further, the etched shape became anisotropic.

In the present embodiment, similarly to the first embodiment, it is possible to promote the nitride film etching in the nitride film etching step, improve the etching selectivity to silicon, and perform etching with good productivity. Become.

In the first and second embodiments of the present invention, C ₄ F ₈ gas is used as the main reaction gas for etching the nitride film. However, C ₃ F ₆ , C ₄ F ₆ and C ₅ F _{8 are used.} The same effect can be obtained even if at least one selected from the group consisting of fluorocarbon gas such as gas is used as the reaction gas.

In the first and second embodiments of the present invention, CH ₂ F ₂ gas is used as an additive gas for etching a nitride film. However, monofluoromethane (CH ₃ F) and methyl bromide (CH ₃ Br) are used. ), CxHyOH (C ₂ H ₅ OH, CH ₃ O
The same applies if at least one selected from the group consisting of gas containing hydrogen atoms such as H) is used as an additive gas, or carbon monoxide (CO) or carbon dioxide (CO ₂ ) is used as an additive gas. The effect is obtained.

Further, in the first and second embodiments of the present invention, C ₄ F ₈ is used as the main reaction gas for etching the interlayer oxide film.
_{3 F 6, C 4 F 6} , C 5 F 8 similar effect at least one type selected from herd consisting of fluorocarbon gases, such as gases used in the reaction gas is obtained, a first embodiment of the present invention In the above, the same effect can be obtained by using carbon dioxide (CO ₂ ) in addition to carbon monoxide (CO) as an additive gas.

Finally, in the first and second embodiments of the present invention, the configuration of each of the above embodiments is merely an example in the step of etching the nitride film, and the method of manufacturing a semiconductor device of the present invention comprises the above configuration. Naturally, the present invention includes a method of manufacturing a semiconductor device with various modifications and changes.

[0026]

[Effect of the Invention] As described above, in the etching of the interlayer insulating film having a layered structure of nitride film and oxide film, using a _{C 4 F 8 / CO / Ar} / O 2 mixed gas for etching the oxide film, followed nitride C ₄ F ₈ / CH ₂ F ₂ /
By using an Ar / O ₂ mixed gas, the etching of the nitride film is promoted, and the CHxFy gas is a gas having a high deposition effect, so that the selectivity to the silicon film is improved. Since an etching gas system that is substantially the same as the etching gas system for the interlayer oxide film used in the contact etching step is used in the etching step, stable etching with high productivity can be performed without changing the atmosphere of the etching chamber.

[Brief description of the drawings]

FIG. 1 is a sectional view illustrating a method of manufacturing a semiconductor device according to a first embodiment of the present invention in the order of steps.

FIG. 2 is a sectional view illustrating a method of manufacturing a semiconductor device according to a second embodiment of the present invention in the order of steps.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 31 Silicon semiconductor substrate 2, 32 Polysilicon gate 3, 33 WSi 4, 34 Nitride film 5, 35 Interlayer oxide film 6 Tantalum oxide 7 Capacitance polysilicon plate 8, 38 Photoresist 9, 10, 39, 40 Mixed gas 11 , 41 contacts 36 sidewalls

Claims (8)

[Claims] 1. A laminated film comprising a nitride film as a lower layer and an oxide film as an upper layer is formed above a substrate, and the oxide film is selectively etched away using a first etching gas to form an opening in the oxide film. Forming a portion and etching the nitride film through the opening using a second etching gas, wherein the second etching gas comprises:
A method for manufacturing a semiconductor device, comprising a mixed gas containing CxFy as a main reaction gas. 2. The CxFy of the second etching gas,
2. The method for manufacturing a semiconductor device according to claim 1, wherein the gas is any one of C ₃ F ₆ , C ₄ F ₆ , C ₄ F ₈ , and C ₅ F ₈ . 3. The method of claim 2, wherein the second etching gas is CH ₂ F ₂ ,
_{3. The} method for manufacturing a semiconductor device according to claim 2, wherein any one of CH ₃ F, CH ₃ Br, NH ₃ , C ₂ H ₅ OH, and CH ₃ OH is included as an additional gas. 4. The method according to claim 1, wherein the second etching gas is CO, CO
_3. The method for manufacturing a semiconductor device according to claim 2, wherein any one of the two gases is included as an additional gas. 5. The method for manufacturing a semiconductor device according to claim 2, wherein the first etching gas is a mixed gas using CxFy as a main reaction gas as a main reaction gas of the second etching gas. 6. The method for manufacturing a semiconductor device according to claim 5, wherein the first etching gas contains any of CO and CO ₂ as an additional gas. 7. The method of claim 1, wherein the first etching gas and the second etching gas both include Ar and O ₂ .
7. The method for manufacturing a semiconductor device according to 3, 4, 5, or 6. 8. The method according to claim 1, wherein the etching process using the second etching gas is performed continuously in the same chamber as the first etching after the etching process using the first etching gas. 8. The method for manufacturing a semiconductor device according to 5, 6, or 7.