JP3289480B2 - 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 more particularly to a method for favorably etching and removing a SiON-based material film suitable as an antireflection film for excimer laser lithography.

[0002]

2. Description of the Related Art As high integration of semiconductor devices progresses at an accelerated pace, their minimum processing dimensions are rapidly reduced. For example, the current generation 1
The minimum processing size of 6MDRAM is about 0.5 μm,
It is expected that the size will be reduced to 0.35 μm or less in the next-generation 64 MDRAM, and to 0.25 μm or less in the next-generation 256 MDRAM.

The degree of miniaturization largely depends on the resolution of a photolithography process for forming a mask pattern. Processing in the 0.35 μm to 0.25 μm (deep submicron) class requires a deep ultraviolet light source such as a KrF excimer laser beam (wavelength 248 nm). However, in such a process using monochromatic light, since the contrast and resolution are significantly reduced due to halation and standing wave effects, it is indispensable to use an antireflection film for the purpose of weakening the reflected light from the underlying material film. It is considered.

In recent years, as a constituent material of this antireflection film, S
iON (silicon oxynitride) based materials have been proposed. This is because this material has good optical constants n and k (where n and k represent the real part and imaginary part coefficients of the complex refractive index, respectively) in the far ultraviolet region where excimer laser lithography is performed. It is. Moreover, this SiO
The optical constant of the N antireflection film can be changed over a wide range by controlling the gas composition during film formation. Therefore, by optimizing the optical constant and the film thickness of the SiON antireflection film according to the optical constant of the underlying material film, a resist pattern can be formed with extremely good resolution.

[0005]

After the underlying material film is etched by using the resist mask formed as described above, the resist mask is removed, but the SiON antireflection exposed at this time is removed. It is also desirable to remove the film in the next step or to reduce the film thickness. This is because if the SiON antireflection film is used as a part of the interlayer insulating film while being left on the pattern of the lower material film, the surface step of the substrate is increased.

However, as can be seen from the fact that the elemental composition ratio of SiON is approximately Si: O: N = 2: 1: 1, about 50% is occupied by Si, and its dry etching characteristics are also similar to those of Si and SiO. _x (silicon oxide). Therefore, it is not always easy to optimize the etching conditions.

[0007] That is, when etched with a fluorocarbon-based gas according to dry etching conditions for general SiO _x antireflection film of the SiON-based, the etching rate decreases extremely. This is because SiON is Si
This is because, since it is Si-rich than O _x, the removal of C atoms by O atoms does not progress and the deposition of carbon-based polymer becomes excessive.

On the other hand, when the SiON-based antireflection film is etched under a Si-based etching condition using a chlorine-based gas, a large amount of O ^* (oxygen radicals) is generated at the time of etching because SiON is O-rich than Si. Released.
However, since the chemical species to O ^* efficiently trapped in the plasma does not exist O ^* becomes large excess, removing the sidewall protection film formed on the pattern side on the walls of the base material, further the exposed pattern side wall To attack. As a result, there is a great possibility that the anisotropic shape of the pattern of the base material that has already been formed is deteriorated.

In particular, a Si substrate 1 as shown in FIG.
And tungsten (W) on gate oxide film 2-
In the case of polycide gate electrode processing, the lower polysilicon layer 3e is of course, but the upper layer W
Significant immersion erosion is generated in the Si _x layer 4e, resulting in the gate electrode 5e [subscript e caused a deterioration in shape representing that are Hitasawa (eroded). ] Is formed. This is because the cooperation of the O ^* and Cl in plasma ^* generated from SiON antireflection film 6a, W from WSi _x film is drawn at a high speed in the form of WClO ^*, accelerated etching progresses . The gate electrode 5a before the removal of the SiON antireflection film 6a [the subscript a is an anisotropic shape (a
nisotropic). ] Is as shown by the broken line in the figure. When the anisotropic shape of the gate electrode is deteriorated in this way, wiring resistance deviates from a design value, and inconveniences such as difficulty in forming a sidewall for forming an LDD structure are caused.

Accordingly, the present invention provides a method of forming a SiON film after resist patterning and etching of an underlying material film.
It is an object of the present invention to provide a method of manufacturing a semiconductor device for easily removing an anti-reflection film.

[0011]

SUMMARY OF THE INVENTION A method of manufacturing a semiconductor device according to the present invention is proposed in view of the above-mentioned object.
The SiON-based material film is reformed through an annealing process in a predetermined gas atmosphere and then removed by etching. Here, the SiON-based material film is typically formed by a plasma CVD method, but depending on the composition of the raw material gas used at this time, a composition containing hydrogen atoms, that is, a SiONH-based material film is used. In some cases.

Representative examples of the predetermined gas atmosphere include an oxygen-based gas atmosphere and a nitrogen-based gas atmosphere. The modification in the former is a composition approximation to a silicon oxide-based material film, and the modification in the latter is a composition approximation to a silicon nitride-based material film.
Further, the annealing treatment includes furnace annealing,
Alternatively, RTA using a halogen lamp (Rapid
Thermal annealing). Especially R
In the case of TA, if this is performed in an oxygen-based gas atmosphere, so-called RTO (rapid thermal oxidation),
If the process is performed in a nitrogen-based gas atmosphere, a process called RTN (rapid thermal night illumination) is performed.

Here, one of the practically important uses of the SiON-based material film is as an antireflection film in photolithography. This photolithography
This is performed to form a resist mask for etching a material film on the underside of the SiON-based material film. At this time, the underlying material film may be a conductive film or an insulating film.

Typical examples of the conductive film used for manufacturing a normal semiconductor device are a high melting point metal silicide film, a polycide film, a high melting point metal film, a Cu-based material film and the like, all of which have a high light reflectance. It is a membrane. However, in the present invention, SiON
In order to perform an annealing process for modifying the base material film, the conductive film needs to have a certain degree of heat resistance. From such a viewpoint, the Al-based material film is inappropriate.

On the other hand, a typical example of the insulating film is a SiO _x -based material film. However, since the insulating film used for manufacturing the semiconductor device is usually transparent, the SiON
The system material film is provided not only for the light reflected from the insulating film but also for mainly preventing the light reflected from the lower conductive film or the Si substrate.

In the present invention, the annealing of the SiON-based material film is performed after removing the resist mask. The reason why the timing of the annealing process is not set before the formation of the resist mask is that the change in the optical constant due to the modification does not affect the photolithography process. The removal of the resist mask may be performed after all the dry etching of the underlying material film is completed, or may be performed after the dry etching is performed with a small amount of the remaining portion left.

In the former case, the modified SiON-based material film is basically removed by etching alone. In the latter case, it is of course possible to remove the SiON-based material film alone. However, considering the efficiency of the process, the remaining portion of the underlying material film and the modified SiON-based material film are simultaneously removed. It is particularly effective to do so. this is,
In the course of the above-mentioned annealing treatment, the remaining portion exposed on the surface of the substrate at that time may be simultaneously modified depending on the constituent material, and appropriate etching conditions should be set according to the content of the modification. This is because simultaneous removal is possible if selected.

The modified SiON-based material film can be removed by wet etching or dry etching. Which etching is selected may be determined according to a desired selection ratio and shape, or the type of material to be removed by etching. For example, when it is desired to remove the sidewall protective film adhered to the pattern sidewall simultaneously with the SiON-based material film, wet etching that allows isotropic etching is suitable. Also, the removal of the SiON-based material film also serves to remove the remaining portion of the underlying material film, and when the remaining portion is to be processed anisotropically, dry etching is suitable.

[0019]

The point of the present invention is that, prior to the removal of the SiON-based material film by etching, the film is modified by annealing beforehand to facilitate the removal by etching. When the above-mentioned reforming is performed in an oxygen-based gas atmosphere or a nitrogen-based gas atmosphere, a composition approximation to a silicon oxide-based material film or a silicon nitride-based material film is performed, whereby the SiON-based material film is relatively Si-rich. Not. Therefore, the SiON-based material film can be quickly removed basically based on the etching conditions for silicon oxide or silicon nitride. As a result, a decrease in the etching rate unlike the conventional case does not occur. not to mention,
Since there is no need to select etching conditions for Si at all, the problem of anisotropic shape degradation due to excessive O ^* can also be avoided.

The SiON-based material film is typically used as an anti-reflection film. However, since the modification by annealing is performed after removing the resist mask, the resolution characteristics in photolithography are not affected at all. Also,
The removal of the SiON-based material film by wet etching or dry etching can be performed alone or in accordance with the degree to which the etching of the underlying material film is completed and the resist mask is removed. In any case, since the SiON-based material film is a thin film, the etching removal is completed within a short time, and does not cause any damage to other parts.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

Embodiment 1 In this embodiment, in processing a W-polycide gate electrode, the W-polycide film and the SiON antireflection film thereon are anisotropically etched through a resist mask, and further the resist mask is formed. In this example, the SiON antireflection film is modified by performing an annealing process in an O ₂ atmosphere after ashing, and the SiON antireflection film is removed by a dilute hydrofluoric acid process. The process of this embodiment will be described with reference to FIGS.

FIG. 1 shows an etched sample in this embodiment.
The configuration of the wafer used as the above is shown. Here, the Si substrate
1 through a gate oxide film 2 having a thickness of about 8 nm.
Side film 5 and SiON antireflection film 6 are sequentially laminated
And a pattern patterned on it
A resist mask 7 is formed. Here, W-
The polycide film 5 contains impurities in order from the lower layer side.
A polysilicon film 3 having a thickness of about 50 nm and a polysilicon film 3 having a thickness of about 50 nm
WSi_xThe film 4 is sequentially laminated. Also on
The SiON antireflection film 6 is made of, for example, SiH_Four/ N _Two
29n thickness by plasma CVD using O mixed gas
m. Further, the resist mask 7
Is a chemically amplified resist material (manufactured by Wako Pure Chemical Industries; trade name: WK
R-PT1) and KrF excimer laser stepper
Formed with a thickness of about 1 μm and a pattern width of about 0.25 μm
Have been.

Next, the wafer is set in an RF bias application type magnetic field microwave plasma etching apparatus,
As an example, the SiON antireflection film 6 and W
-The polycide film 5 was collectively etched. Cl ₂ flow rate 72 SCCM O ₂ flow rate 8 SCCM Gas pressure 0.4 Pa Microwave power 750 W (2.45 GH)
z) RF bias power 40 W (2 MHz) Wafer mounting electrode temperature 0 ° C. (using alcohol-based refrigerant) In this etching, SiO _x -based side wall protective film (not shown) due to the contribution of O ₂ in the etching gas. ) Was formed, anisotropic etching proceeded, and a gate electrode 5a having an anisotropic shape was formed as shown in FIG.
In the drawings, the material layers that have been subjected to anisotropic processing are indicated by the original symbols with the suffix a.

Next, after the resist mask 7 was removed by ordinary O ₂ plasma ashing, furnace annealing in an O ₂ atmosphere was performed under the following conditions as an example. O ₂ flow rate 10 liter / min Annealing temperature 850 ° C. Annealing time 25 min By this annealing, as shown in FIG. 3, the SiON antireflection film 6a has a modified layer 6m having a composition closer to SiO _x [subscript m is Indicates that the data has been modified. ].

Next, dilute hydrofluoric acid treatment was performed as wet etching, and a part of the modified layer 6m was promptly removed as shown in FIG. Since the etching mechanism in this dilute hydrofluoric acid treatment is isotropic, the SiO _x -based side wall protective film adhered to the side wall surface of the gate electrode 5a was also removed at this time. Thereby, a favorable anisotropic shape of the gate electrode 5a could be maintained.

Incidentally, damage to the gate oxide film 2 at this time could be minimized.

Embodiment 2 In this embodiment, the etching of the W-polycide film in the embodiment 1 is completed with a small amount of the underlying polysilicon film left, and after the resist mask is ashed, it is annealed in an N ₂ atmosphere. The treatment was performed to modify the SiON antireflection film and the remaining portion of the polysilicon film, and both of them were simultaneously removed by dry etching. The process of the present embodiment
This will be described with reference to FIGS. 5, 6, and 4. FIG.

FIG. 5 shows that the etching of the W-polycide film 5 described in the first embodiment shows that the lower polysilicon film 3 has a small residual portion 3r [subscript r is a residual. ] Has been stopped at the place where [] has been left. Here, the thickness of the remaining portion 3r is set substantially equal to the thickness of the SiON antireflection film 6a. This is because the dry etching of both is completed almost simultaneously in a later step.

Next, after the resist mask 7 was removed by ordinary O ₂ plasma ashing, furnace annealing in an N ₂ atmosphere was performed under the following conditions as an example. N ₂ flow rate 10 liter / minute Annealing temperature 900 ° C. Annealing time 25 minutes By this annealing, as shown in FIG. 6, the SiON antireflection film 6a has a modified layer 6 having a composition close to SiN _x.
m. At the same time, the remaining portion 3r of the polysilicon layer also has a modified layer 3 having a composition closer to SiN _x.
m.

Next, this wafer is set in an RF bias application type magnetic field microwave plasma etching apparatus for etching an oxide film, and dry etching for removing the modified layers 3m and 6m is performed under the following conditions as an example. went. CHF ₃ flow rate 45 SCCM O ₂ flow rate 5 SCCM gas pressure 1.3 Pa Microwave power 900 W (2.45 GH)
z) RF bias power 100 W (800 kHz) Wafer mounting electrode temperature 0 ° C. By this etching, the modified layers 3 m and 6 m are quickly removed, and as shown in FIG. A gate electrode 5a having a shape was obtained. Note that the above etching conditions are typical SiN _x / SiO _x selective etching conditions, and a higher selectivity than that of Example 1 for the gate oxide film 2 could be achieved.

Embodiment 3 In this embodiment, a SiO _x anti-reflection film is laminated on SiO _x.
In the process of opening the contact holes in the interlayer insulating film, etching of the SiO _x interlayer insulating film underlying Si
Stopping just before the substrate is exposed, ashing the resist mask, annealing in an O ₂ atmosphere,
reforming iON antireflection film was the remainder of the modified SiON antireflection film and a SiO _x interlayer insulating film simultaneously removed by dry etching. The process of this embodiment will be described with reference to FIGS.

FIG. 7 shows the structure of a wafer used as an etching sample in this embodiment. This wafer has a thickness of about 1 μm on a Si substrate 11 on which a diffusion layer 12 is formed in advance.
A SiO ₂ interlayer insulating film 13, a 50 nm thick SiON antireflection film 14, and a resist mask 15 having a thickness of about 1.0 μm and having an opening 16 according to a hole pattern are sequentially formed.

This wafer is subjected to a magnetic field microwave plasma
It is set in an etching apparatus, and as an example, S
The entire iON antireflection film 14 and about 95% of the thickness of the SiO ₂ interlayer insulating film 13 were etched. CHF ₃ flow rate 45 SCCM CH ₂ F ₂ flow rate 5 SCCM Gas pressure 0.2 Pa Microwave power 1000 W (2.45 GH
z) RF bias power 200 W (800 kHz)
z) Wafer mounting electrode temperature 0 ° C. (using alcohol-based refrigerant) By this etching, as shown in FIG. 8, a contact hole 17 is formed halfway, and a bottom surface is formed with S
The remaining portion 13r of the iO _x interlayer insulating film 13 remained.

Next, after removing the resist mask 15 by ordinary O ₂ plasma ashing, O ₂ annealing was performed under the same conditions as those described in the first embodiment. This annealing, as shown in FIG. 9, the modified layer SiON antireflection film 14 has a composition similar to the SiO _x 14
m. At this time, the remaining portion 13r of the SiO _x interlayer insulating film 13 is similarly exposed to the oxidizing atmosphere, but the composition of the remaining portion 13r does not change any more.

Next, as an example, the entire surface of the modified layer 14m and the remaining portion 13r of the SiO ₂ interlayer insulating film 13 was etched back under the following conditions. CHF ₃ flow rate 40 SCCM CH ₂ F ₂ flow rate 10 SCCM Gas pressure 0.2 Pa Microwave power 1000 W (2.45 GH)
z) RF bias power 180 W (800 kHz)
z) Wafer mounting electrode temperature 0 ° C. (using alcohol-based refrigerant) This condition is that the selection ratio between SiO ₂ / Si is improved because the flow rate ratio of CH ₂ F ₂ is higher than the previous etching condition. It is. However, since the composition of the modified layer 14m formed by the above-described annealing process is close to SiO ₂ , the remaining layer 1 of the modified layer 14m and the SiO _x interlayer insulating film 13
Etching was rapidly performed at a speed substantially equal to that of 3r.
As a result, as shown in FIG. 10, a contact hole 17 having an anisotropic shape was completed. Naturally, a high selectivity was secured for the underlying Si substrate 11 (diffusion layer 12).

Although the present invention has been described based on three embodiments, the present invention is not limited to these embodiments, but includes annealing conditions, oxygen-based gas and nitrogen-based gas used. The details such as the type of the sample, the configuration of the sample wafer, the dry etching apparatus to be used, and the dry etching conditions can be changed as appropriate.

[0038]

As is clear from the above description, according to the present invention, the etching removal of the SiON-based material film can be facilitated through the annealing treatment. Therefore, a practical etching rate can be achieved, and the anisotropic shape of the pattern of the already formed base material film is not impaired.

The SiON-based material film is promising as an anti-reflection film in excimer laser lithography, and its improvement in etching removal characteristics is greatly required to enhance the precision and reliability of microfabrication of next-generation and subsequent semiconductor devices. It will contribute.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a state of a wafer before etching in an example of a process in which the present invention is applied to W-polycide gate electrode processing.

FIG. 2 is a schematic cross-sectional view showing a state where the SiON antireflection film and the W-polycide film of FIG. 1 are anisotropically etched.

[3] removing the resist mask of Figure 2, further O ₂
FIG. 4 is a schematic cross-sectional view showing a state where annealing is performed to change a SiON antireflection film into a modified layer.

FIG. 4 is a schematic cross-sectional view showing a state where a modified layer of FIG. 3 is removed and a gate electrode is completed.

FIG. 5 is a schematic cross-sectional view showing a state in which a W-polycide film is etched leaving a part of a polysilicon film in another process example in which the present invention is applied to W-polycide gate electrode processing.

6 is a schematic cross-sectional view showing a state in which N ₂ annealing has been performed to change the remaining portions of the SiON antireflection film and the polysilicon film of FIG. 5 into modified layers, respectively.

FIG. 7 is a schematic sectional view showing a state of a sample wafer before etching in a process example in which the present invention is applied to contact hole processing.

[8] SiON antireflection film and a SiO _x interlayer insulating film 7 is etched, it is a schematic sectional view showing a state where the contact hole is opened halfway.

FIG. 9: The resist mask of FIG. 8 is removed and O ₂
FIG. 4 is a schematic cross-sectional view showing a state where annealing is performed to change a SiON antireflection film into a modified layer.

FIG. 10 is a schematic cross-sectional view showing a state in which a modified layer of FIG. 9 and a remaining portion of the SiO _x interlayer insulating film are simultaneously removed.

FIG. 11 is a schematic cross-sectional view showing a state in which the anisotropic shape of the gate electrode has deteriorated in the conventional W-polycide gate electrode processing.

[Explanation of symbols]

1,11 Si substrate 3 Polysilicon film 3m Modified layer (of polysilicon film 3) 3r Remaining part 4 (of polysilicon film 3) 4WSi _x film 5 W-polycide film 5a Gate electrode 6,14 SiON antireflection film 6m , (the SiON antireflection film 6, 14) 14m (the SiO _x interlayer insulating film 13) modified layer 7, 15 resist mask 13 SiO _x interlayer insulating film 13r remainder 17 contact hole

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065

Claims (8)

(57) [Claims] 2. A method of manufacturing a semiconductor device, comprising: modifying a SiON-based material film through an annealing process in a predetermined gas atmosphere; 2. The method for manufacturing a semiconductor device according to claim 1, wherein the predetermined gas atmosphere is an oxygen-based gas atmosphere, and the modification is a composition approximation to a silicon oxide-based material film. 3. The method according to claim 1, wherein the predetermined gas atmosphere is a nitrogen-based gas atmosphere, and the modification is a composition approximation to a silicon nitride-based material film. 4. The SiON-based material film is used as an anti-reflection film in photolithography for forming a resist mask for dry-etching the underlying material film, and the annealing removes the resist mask. The method according to claim 1, wherein the method is performed after performing the method. 5. The method according to claim 4, wherein the removal of the resist mask is performed after all the dry etching of the underlying material film is completed. 6. The removal of the resist mask is performed after the dry etching of the material film on the base side is completed in a state where a residual portion is left, and the residual portion is modified with the SiO 2 that has been modified.
5. The method of manufacturing a semiconductor device according to claim 4, wherein the etching is performed simultaneously with the N-based material film. 7. The method of manufacturing a semiconductor device according to claim 1, wherein the removal of the modified SiON-based material film is performed by wet etching. 8. The method according to claim 1, wherein the modified SiON-based material film is removed by dry etching.