JP3450253B2 - 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 dry etching process performed during a semiconductor device manufacturing process, and more particularly to a semiconductor device including a process of etching an inorganic antireflection film and a film to be processed by using a resist film as a mask. The present invention relates to a manufacturing method.

[0002]

2. Description of the Related Art As the speed of high integration of semiconductor devices is increasing, the minimum processing size thereof is rapidly decreasing. This reduction is dependent on photolithography technology. In this photolithography technique, in the sub-quarter micron (0.25 μm or less) region, the KrF excimer laser light (248 nm) or the ArF excimer laser light (193 nm) that is deep ultraviolet light is used as the exposure source.
However, since these excimer laser beams have high temporal and spatial coherence, a standing wave effect is likely to occur in the resist film and halation occurs under the resist film. Cheap.

Therefore, in the exposure technique using deep ultraviolet light, it is essential to use an antireflection film together with the resist film. As the antireflection film, there are a top type provided on the resist film and a bottom type inserted below the resist film, but at present, the bottom type is widely used. A silicon oxynitride film (Si) is used as a film for preventing the reflection of deep ultraviolet light.
ON) or a laminate of this and a silicon oxide film (SiO
₂ / SiON) is known to be effective.

FIG. 6 shows an inorganic antireflection film [ARL (an
is a sectional view in the order of steps showing a conventional etching method using a so-called "ti-reflective layer"]. First, the processed film 33 is formed on the semiconductor substrate 31 with the underlying layer 32 interposed therebetween, and the inorganic antireflection film 34 made of a silicon oxynitride film or the like is formed thereon. Then, a photoresist is applied thereon, and exposure and development are performed to form a resist film 35 having a predetermined width (dimension) Z [FIG. 6].
(A)]. Next, the inorganic antireflection film 34 is selectively etched by the dry etching method using the resist film 35 as a mask [FIG. 6 (b)]. Then, the film 33 to be processed is selectively etched by using the resist film 35 and the patterned inorganic antireflection film 34 as a mask to obtain the film 33 to be processed having a predetermined pattern [FIG. 6 (c)].

As an etching gas for the inorganic antireflection film, a gas generally used as an etching gas for a silicon oxide film or a silicon nitride film has been used. That is, in the case of etching a silicon oxide film, CF ₄ , CF ₄ / Ar, CF ₄ / He, CHF
₃ / SF ₆ , CF ₄ / CHF ₃ , CF ₄ / CHF ₃ / A
If r is an etching of the silicon nitride film, S
F ₆ / HBr, CF ₄ / CHF ₃ , CF ₄ / CHF ₃ /
Ar, CHF ₃ / O ₂ , CF ₄ , CF ₄ / Ar, CF ₄
Although / He and the like have been used, these etching gases have also been used for etching the inorganic antireflection film. The technique of interposing an inorganic antireflection film in the lower layer of the photoresist is known from JP-A-7-86244 and JP-A-7-94467.

[0006]

As described above, when the inorganic antireflection film is used under the resist, the step of etching the inorganic antireflection film 34 is required before the etching of the film to be processed. Then, the resist film is exposed to the etching gas for the inorganic antireflection film and etched, so that the resist film 35 undergoes a dimensional change (shortening) from Z to Z ′. In the patterning process of the film to be processed following the etching process of the inorganic antireflection film, the width of the film to be processed deviates from the initial size defined by the reticle, because the resist film that has been shortened is used as a mask. It will be. An object of the present invention is to solve the above-mentioned problems of the prior art, and an object thereof is to suppress the dimensional change of the resist pattern by increasing the resist selectivity with respect to the etching of the inorganic antireflection film. This is to improve the processing accuracy of the film to be processed.

[0007]

To achieve the above object, according to the present invention, (1) a step of forming a film to be processed on a semiconductor substrate and forming an inorganic antireflection film on the film to be processed; 2) a step of forming a resist film having a predetermined pattern by applying a photoresist on the antireflection film and performing exposure / development; (3) using the resist film as a mask , CF ₄ (tetrafluoride)
A mixture containing carbon), HBr (hydrogen bromide) and an inert gas
A step of selectively etching the inorganic antireflection film by using a gas as an etching gas; and (4) selecting the film to be processed by using the resist film and the inorganic antireflection film patterned in the previous step as a mask. A step of selectively etching the semiconductor device, the method comprising:
Mixing ratio of gases {Inert gas / (CF ₄ + HBr + Inert gas
)} Is 50% or more .

In order to achieve the above object, according to the present invention, (1) a process of forming a film to be processed on a semiconductor substrate and forming an inorganic antireflection film thereon (2) the reflection A step of forming a resist film having a predetermined pattern by applying a photoresist on the prevention film and performing exposure and development; (3) using the resist film as a mask , CF ₄ (tetrafluoride)
Etch mixed gas containing carbon) and HBr (hydrogen bromide)
Selectively etching the inorganic antireflection film by using the inorganic antireflection film as a masking gas , and (4) selectively etching the film to be processed by using the resist film and the inorganic antireflection film patterned in the previous step as a mask. the method of manufacturing a semiconductor device comprising the steps, a to, CF ₄ Contact in the mixed gas
And the mixing ratio of HBr to HBr {HBr / (CF ₄
+ HBr)} is 25 to 75%, and a method for manufacturing a semiconductor device is provided.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. 1A to 1D are cross-sectional views in order of the processes, showing an embodiment of the present invention. First, the semiconductor substrate 11
A film 13 to be processed is formed on the underlying layer 12, and an inorganic antireflection film 14 is formed thereon. Here, the underlayer 12
Is assumed to be a gate insulating film, an interlayer insulating film, an interlayer insulating film and a wiring layer formed thereon, and the film to be processed is a conductive thin film such as a polysilicon layer, a polycide layer, or an Al alloy film. Alternatively, an insulating film such as a silicon oxide film is assumed. A silicon oxynitride film, a silicon oxide film, or a laminated film thereof is used as the inorganic antireflection film. A positive chemically amplified photoresist is applied thereon, and exposure and development are performed to form a resist film 15 having a line pattern or a hole pattern [FIG. 1 (a),
(D)].

Next, the inorganic antireflection film 14 is subjected to RIE (reactive ion) using the resist film 15 as a mask.
Etching) is used to selectively etch.
CF ₄ (carbon tetrafluoride) and HBr are used as etching gas.
A mixed gas of (hydrogen bromide) and an inert gas (for example, He) is used [FIG. 1 (b), (e)]. At the time of etching this inorganic antireflection film, the line pattern has X → X ′,
The hole pattern undergoes a dimensional change of Y → Y ′.

FIGS. 2 and 3 are graphs showing the experimental results obtained by using He as the inert gas and changing the mixing ratio (the same as the flow rate ratio) of the mixed gas of CF ₄ / HBr / He. The experiment shows that ICP (i
Etching was performed under the following conditions by using an n-duplicate-coupled plasma) etching apparatus. Pressure: 1.333 Pa (10 mTorr
r) Source power: 400W Bias power: 100W

FIG. 2 shows that in the etching process of the inorganic antireflection film 14, the He mixture ratio {He /
(CF ₄ + HBr + He)} is controlled to 50%, and CF ₄
And HBr mixing ratio {HBr / (CF ₄ + HBr)} is changed, the dimensional change rate of the resist pattern [CD
(Critical dimension) shif
and the resist selectivity with respect to the resist (the etching rate of the inorganic antireflection film with respect to the resist pattern) is shown. The dimensional change rate in FIG. 2 is X in FIGS. 1 (a) and 1 (b).
(X-X ') / X for X and X'is shown in FIG.
Similar results are obtained for (Y'-Y) / Y for Y and Y'in (d) and (e).

According to FIG. 2, from the portion surrounded by the ellipses A and B, the mixing ratio of CF ₄ and HBr {HBr /
It can be seen that when (CF ₄ + HBr)} is about 25 to 75%, a favorable effect on the dimensional change rate of the resist pattern and the resist selectivity ratio is obtained. Although not shown in this figure, when the mixing ratio exceeds 80%, the etching rate of the inorganic antireflection film is remarkably reduced, and the selectivity ratio to resist is lowered.

Further, FIG. 3 shows that in the etching process of the inorganic antireflection film, the mixing ratio of CF ₄ and HBr {HBr /
(CF ₄ + HBr)} is 50% (that is, CF ₄ : HB)
The experimental result of the dimensional change rate of the resist pattern is shown when the mixing ratio {He / (CF ₄ + HBr + He)} of He at all flow rates is changed by controlling r = 1: 1).
According to this FIG. 3, the He mixture ratio {He
It is understood that when / (CF ₄ + HBr + He)} exceeds 50%, a preferable effect on the dimensional change rate of the resist pattern is obtained.

From the above experimental results, the mixing ratio of the mixed gas in the etching process of the inorganic antireflection film is CF ₄ and H.
The Br mixing ratio {HBr / (CF ₄ + HBr)} is 25 to
Mixing ratio of He at 75% and total gas flow rate {He
It is understood that when the ratio / (CF ₄ + HBr + He)} is controlled to be 50% or more, preferable effects of the resist selectivity and resist dimensional change rate can be obtained.

With respect to He mixed with the etching gas, the same result was obtained even if another inert gas such as Ar was used instead of He. Further, the etching apparatus used in the step of etching the inorganic antireflection film of the present invention is not limited to the IPC type, but may be an ECR (electron type).
An etching apparatus using another low-pressure high-density plasma source such as a cyclotron resonance type may be used, and further, a parallel plate type or a magnetron type RIE (r) may be used.
An etching apparatus that is not a low-pressure high-density plasma type such as an active ion etching apparatus may be used.

After the inorganic antireflection film 14 is etched, as shown in FIGS. 1C and 1F, a resist film 15 is formed.
The processed film 13 is etched using the patterned inorganic antireflection film 14 as a mask. When this etching is performed by the dry method, it is desirable to continue the etching in the same chamber as the etching of the inorganic antireflection film. Then, the resist film is removed using a stripping solution or oxygen plasma to complete the patterning process for the film to be processed.

[0018]

Embodiments of the present invention will now be described with reference to the drawings. [First Embodiment] FIGS. 4A to 4D are sectional views showing the first embodiment of the present invention in the order of steps. A gate oxide film 22 having a film thickness of 10 nm was formed on the silicon substrate 21 by a thermal oxidation method. Next, the film thickness is 300 nm by the low pressure CVD (LPCVD) method.
Of polysilicon film 23 is deposited, and a silicon oxynitride film 24a having a film thickness of 10 nm and a film thickness of 40 n are formed on the polysilicon film 23 by a CVD method.
m silicon oxide film 24b is deposited to form the inorganic antireflection film 2
4 was formed. Then, a positive chemically amplified photoresist was spin-coated to a film thickness of 0.8 μm, exposed by a stepper using an ArF excimer laser as an exposure light source, and developed to obtain a resist film 25 having a line width of 0.13 μm. [Fig. 4
(A)].

Next, the inorganic antireflection film 24 is dry-etched using the resist film 25 as a mask. The etching was performed under the following conditions using an IPC etching device [FIG. 4 (b)]. Mixed gas: CF ₄ 25 sccm HBr 25 sccm He 50 sccm Pressure: 1.333 Pa (10 mTorr)
r) Source power: 400W Bias power: 100W

Then, the polysilicon film 23 is etched under the following conditions in the same chamber to form the gate electrode 2.
3'is formed [FIG. 4 (c)]. Mixed gas: Cl ₂ 20 sccm HBr 100 sccm Pressure: 1.333 Pa (10 mTorr)
r) Source power: 400W Bias power: 100W

[Second Embodiment] FIGS. 5A to 5C are sectional views in order of the processes, showing a second embodiment of the present invention. Silicon substrate 21
A gate oxide film 22 having a film thickness of 10 nm was formed on the top by a thermal oxidation method. Then, a 200 nm-thickness polysilicon film 23a is deposited by low pressure CVD (LPCVD), and a tungsten silicide (WSi) film 23b is subsequently deposited by sputtering to form a gate electrode material layer, and then a CVD method is formed thereon. 15 nm thick silicon oxynitride film 2
4a and a silicon oxide film 24b having a film thickness of 35 nm were deposited to form an inorganic antireflection film 24. Then, a positive chemically amplified photoresist is spin-coated to a film thickness of 0.8 μm,
It was exposed by a stepper using an ArF excimer laser as an exposure light source and developed to obtain a resist film 25 having a line width of 0.13 μm [FIG. 5 (a)].

Next, the inorganic antireflection film 24 is dry-etched using the resist film 25 as a mask. The etching was performed using an IPC etching apparatus under the following conditions [FIG. 5 (b)]. Mixed gas: CF ₄ 40 sccm HBr 20 sccm He 70 sccm Pressure: 1.333 Pa (10 mTorr)
r) Source power: 400W Bias power: 100W

Subsequently, the tungsten silicide film 23b and the polysilicon film 23a were etched under the same conditions in the same chamber to form a gate electrode 23 '[FIG. 5 (c)]. Mixed gas: Cl ₂ 50 sccm O ₂ 5 sccm Pressure: 0.667 Pa (5 mTorr
r) Source power: 400W Bias power: 100W

Although the preferred embodiments and examples have been described above, the present invention is not limited to these embodiments and examples, and appropriate modifications can be made without departing from the gist of the invention. It is something.

[0025]

As described above, the present invention uses a mixed gas containing CF ₄ and HBr at a mixing ratio close to 1: 1 as the etching gas for the inorganic antireflection film. A high selection ratio with respect to the resist can be obtained as compared with the above, and therefore, the dimensional change of the resist film can be reduced during the etching of the inorganic antireflection film. Therefore, according to the present invention, it becomes possible to perform lithography using deep ultraviolet light with high accuracy.

[Brief description of drawings]

1A to 1C are cross-sectional views in order of steps for explaining an embodiment of the present invention.

FIG. 2 is a graph showing experimental results regarding the resist dimensional change rate and the resist selectivity with respect to the mixture ratio of HBr in the etching gas used in the method for manufacturing a semiconductor device of the present invention.

FIG. 3 is a graph showing an experimental result regarding a resist dimensional change rate with respect to a mixing ratio of He in an etching gas used in the method for manufacturing a semiconductor device of the present invention.

4A to 4C are cross-sectional views in the order of steps for explaining the first embodiment of the present invention.

5A to 5C are cross-sectional views in the order of processes for explaining the second embodiment of the present invention.

6A to 6C are cross-sectional views in the order of processes for explaining the conventional technique.

[Explanation of symbols]

11, 31 Semiconductor substrate 12, 32 Underlayer 13, 33 Processed film 14, 24, 34 Inorganic antireflection film 15, 25, 35 resist film 21 Silicon substrate 22 Gate oxide film 23, 23a Polysilicon film 23b Tungsten silicide film 23 'gate electrode 24a Silicon oxynitride film 24b Silicon oxide film

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/3213 H01L 21/28 H01L 21/3065

Claims (7)

(57) [Claims] 1. A process of forming a film to be processed on a semiconductor substrate and forming an inorganic antireflection film on the film, and (2) applying a photoresist on the antireflection film and exposing and developing. And (3) using the resist film as a mask to form CF ₄ (tetrafluoride).
A mixture containing carbon), HBr (hydrogen bromide) and an inert gas
A step of selectively etching the inorganic antireflection film by using a gas as an etching gas; and (4) selecting the film to be processed by using the resist film and the inorganic antireflection film patterned in the previous step as a mask. A step of selectively etching the semiconductor device, the method comprising:
Mixing ratio of gases {Inert gas / (CF ₄ + HBr + Inert gas
)) Is 50% or more . 2. The method of manufacturing a semiconductor device according to claim 1, wherein the inert gas is He (helium). 3. CF ₄ and HB in the mixed gas
Mixing ratio of HBr to r {HBr / (CF ₄ + HB
r)} is 25-75%.
A method of manufacturing a semiconductor device according to item 1. 4. A step of (1) forming a film to be processed on a semiconductor substrate and forming an inorganic antireflection film on the film, and (2) applying a photoresist on the antireflection film and performing exposure and development. And (3) using the resist film as a mask to form CF ₄ (tetrafluoride).
Etch mixed gas containing carbon) and HBr (hydrogen bromide)
Selectively etching the inorganic antireflection film by using the inorganic antireflection film as a masking gas , and (4) selectively etching the film to be processed by using the resist film and the inorganic antireflection film patterned in the previous step as a mask. the method of manufacturing a semiconductor device comprising the steps, a to, CF ₄ Contact in the mixed gas
And the mixing ratio of HBr to HBr {HBr / (CF ₄
The method of manufacturing a semiconductor device + HBr)} is characterized in that 25 to 75%. 5. The inorganic antireflection film is configured to include a silicon oxynitride film.
A method for manufacturing a semiconductor device according to any one of 1. 6. The method of manufacturing a semiconductor device according to claim 1, wherein the inorganic antireflection film is a laminated film of a silicon oxide film and a silicon oxynitride film. 7. The semiconductor device according to claim 1, wherein the step (3) and the step (4) are continuously performed in the same chamber. Production method.