JP2002093741A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Problem] To provide a method of forming a gate electrode and a self-aligned contact that can use an antireflection film having an optical constant adjusted to an optimum value and can secure a sufficient insulation margin. SOLUTION: An anti-reflection film 27a made of an oxynitride film is formed on a conductive layer for forming a gate electrode using a plasma CVD method.
To form After that, the substrate is exposed to oxygen plasma to terminate the NH bond on the surface of the oxynitride film with oxygen. In addition, the antireflection film is left as it is during the etching step for forming the gate electrode. Then, an etching step for forming a self-aligned contact is performed by utilizing the etching selectivity of the remaining antireflection film and the interlayer insulating film 31.

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 gate electrode using an antireflection film to secure a sufficient insulation margin between an electrode and a contact, and a self-alignment using the same. The present invention relates to a method for forming a contact.

[0002]

2. Description of the Related Art As the degree of integration of semiconductor devices increases, the width and spacing of wirings gradually decrease, and devices having a design rule of 0.2 μm or less have appeared. One of the most difficult problems in manufacturing an element having such a fine pattern is that it is difficult to secure an alignment margin in a photolithography process. In particular, the miniaturization of contacts of semiconductor memory devices is remarkable, and there is a limit in forming a miniaturized contact as a mask alignment technique in a current photolithography process. Therefore, a technique for overcoming such limitations with an etching technique has been developed, and a typical contact forming method thus developed is a self-aligned contact (SAC) forming method.

In the SAC forming step, the upper surface of each gate electrode is covered with a nitride film, and nitride film spacers are formed on both sides of the gate electrode to define in advance the portions where contacts are to be formed. Then, a contact hole is formed between the gate electrodes by interlayer insulating film etching using a high etching selectivity between the oxide film and the nitride film.

However, in the conventional SAC forming process, when the oxide film is selectively etched to form the contact hole, the nitride film spacer cannot be completely prevented from being etched. Therefore, if misalignment occurs during mask alignment in a photolithography process for etching an oxide film, the nitride film is partially etched at corners of the gate electrode. Further, when the degree of misalignment becomes severe, it becomes difficult to maintain the minimum insulation margin that should be maintained between the gate electrode and the contact. Between them.

Therefore, when fabricating a device having a small design rule, it is necessary to consider a method for effectively preventing a short circuit between a gate electrode and a contact in a SAC forming process.

On the other hand, in order to improve the operation speed of the device, it is necessary to form the gate electrode with a material having high electric conductivity. For this reason, the use of a so-called “polymetal structure” in which a metal film is stacked on a polysilicon film doped with impurities has been studied as a gate electrode structure.

In the case of forming a gate electrode having a polymetal structure, it is necessary to use an antireflection film in order to reduce the influence of irregular reflection by a metal film having a high reflectance in a photolithography process.

As a conventional technique for solving these problems, an antireflection film used when forming a gate electrode is used.
By leaving the gate electrode even after the gate electrode is formed, the gate electrode can be formed not only in the photolithography process for forming a SAC between the gate electrodes but also in the photolithography process for forming a direct contact on the SAC. How to reduce the effects of diffuse reflection from
For example, it is disclosed in JP-A-11-340336.

[0009]

However, conventionally, a silicon oxynitride film formed by LP-CVD has been generally used as an antireflection film. Reactions other than the general stoichiometric composition are difficult because the film is formed by the reaction, and the optical constants such as the refractive index and extinction coefficient necessary to reduce the influence of diffuse reflection by the metal film are adjusted to the optimum values. There was a problem that it was difficult to pack.

In general, in order to adjust the optical constant of the antireflection film to an optimum value, it is more preferable to form the film by plasma CVD in which the film is formed by energy of plasma in addition to heat. However, a silicon oxynitride film formed by plasma CVD is preferable. Is a film having a large hydrogen content and a weak bond between atoms because the film is usually formed at about 300 to 400 ° C.

For this reason, it cannot be used as an insulating film requiring a high etching selectivity with an oxide film at the time of etching an interlayer insulating film as in the SAC forming step. For the above reasons, a silicon oxynitride film formed by LP-CVD has been used to secure an etching selectivity.

In order to form a silicon oxynitride film, it is necessary to always use a gas containing oxygen irrespective of the method of film formation, and the oxygen reacts with the metal film to react with the surface of the metal film. Oxidized.

In recent years, a chemically amplified resist that generates an acid upon exposure to light and promotes development has been used. When the chemically amplified resist is patterned on a silicon oxynitride film, the shape of the resist after patterning becomes a base. There was a problem called "footing" that took shape.

In view of the above, an anti-reflection film that replaces the anti-reflection film used in the SAC forming process with a conventional silicon oxynitride film formed by LP-CVD is desired.

That is, the present invention relates to an antireflection film in which optical constants such as a refractive index and an extinction coefficient are optimized in order to minimize the influence of irregular reflection by a metal film. A method of manufacturing a semiconductor device including a method of forming an antireflection film that can prevent a metal film from reacting and oxidizing a metal film, and does not cause footing in which a resist shape after patterning is transformed into a trapezoidal shape. The purpose is to provide.

[0016]

In order to achieve the above object, in a method of manufacturing a semiconductor device according to the present invention, a step of sequentially depositing a polysilicon film and a metal film on a substrate on which a gate insulating film is formed. Forming a silicon oxynitride film also functioning as an anti-reflection film on the metal film by a plasma CVD method, and exposing the silicon oxynitride film to a plasma of an oxygen-containing gas after forming the silicon oxynitride film by the plasma CVD method. A step of performing a surface treatment for terminating the NH bond on the surface of the silicon oxynitride film with oxygen, a step of applying a resist film to the silicon oxynitride film, and a lithography step of forming the resist film into a desired pattern shape And the step of transferring the desired pattern shape by etching the silicon oxynitride film,
Etching the metal film and the polysilicon film using the silicon oxynitride film processed into the desired pattern shape as a hard mask to form a gate electrode having a polymetal structure in which an anti-reflection film pattern is stacked on the metal film and the polysilicon film; And characterized in that:

The use of the plasma CVD method for forming the anti-reflection film makes it possible to adjust the optical constant of the anti-reflection film to an optimum value, and to terminate the NH bond on the surface with oxygen. As a result, footing does not occur.

In the step of forming the silicon oxynitride film, it is preferable that a film forming temperature when the silicon oxynitride film is formed by the plasma CVD method is 500 ° C. or more and 700 ° C. or less. By forming a film in this temperature range, a film having a low hydrogen content and a strong bond between atoms can be formed, and the etching selectivity with the silicon oxide film at the time of etching the interlayer insulating film is sufficiently increased. Becomes possible.

Preferably, the plasma of the oxygen-containing gas is either nitrous oxide plasma or oxygen plasma. This is because, by using nitrous oxide or oxygen plasma, the NH bond on the surface of the silicon oxynitride film can be terminated with oxygen.

In the step of forming the insulating film, it is preferable that the surface of the metal film is nitrided in a plasma of a gas containing nitrogen before the formation of the insulating film by the plasma CVD method. This can prevent the metal film used for the polymetal gate electrode from being oxidized.
In addition, ammonia plasma or nitrogen plasma can be used as the plasma of the nitrogen-containing gas.

According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming a conductive layer on a substrate having a gate insulating film formed thereon; and forming a silicon oxide film on the conductive layer which also functions as an anti-reflection film. Forming a nitride film by a plasma CVD method at a film formation temperature of 500 ° C. or more and 700 ° C. or less, and exposing the silicon nitride film to a plasma of an oxygen-containing gas after forming the silicon nitride film by the plasma CVD method. Performing a surface treatment for terminating the N—H bond with oxygen, applying a resist film to the silicon oxynitride film, forming the resist film into a desired pattern by a lithography process, Transferring the desired pattern shape by etching the nitride film; and removing the silicon oxynitride film processed into the desired pattern shape. Etching the conductive layer and the polysilicon film as a gate mask to form a plurality of gate electrodes on which an anti-reflection film pattern is stacked, and forming a plurality of gate electrodes on the top and side walls of each of the gate electrodes and the anti-reflection film pattern. Depositing the first insulating film and forming a spacer made of the first insulating film on the side wall of each of the gate electrodes and the antireflection film pattern by anisotropically etching the first insulating film. Forming an interlayer insulating film so as to cover each of the gate electrodes and the spacers; and etching a part of the interlayer insulating film by a lithography method to form the first insulating film and the first insulating film between each of the gate electrodes. Forming a contact hole exposing the substrate; and filling a conductive member in the contact hole to form a contact. The features.

It is preferable that the conductive layer has a laminated structure of a polysilicon film doped with impurities and a metal film.

As the first insulating film, a silicon nitride film can be used.

The method may further include, before forming the interlayer insulating film, forming a second insulating film functioning as an etching stop layer on the substrate so as to cover the gate electrode and the spacer. Is also good.

As the second insulating film, a silicon nitride film can be used.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 to 6 are cross-sectional views illustrating a method of forming a gate electrode and a SAC according to a preferred embodiment of the present invention in the order of steps.

Referring to FIG. 1, a gate oxide film 22 having a thickness of about 6 nm is formed on a semiconductor substrate 20 having an active region defined by a field region 21, and an impurity doped polysilicon is formed thereon as a conductive layer. A silicon film 23 is formed to a thickness of about 50 nm using an LP-CVD method, and a metal nitride film 24
Are sequentially formed to a thickness of about 50 nm by a sputtering method. As the metal nitride film 24, for example, a tungsten nitride film, a titanium nitride film, or the like can be used.

As the metal film 25, for example, a tungsten film, a titanium film, a cobalt film or the like can be used.

Next, a nitriding process is performed on the surface of the metal film 25 using a plasma processing apparatus to form a metal nitride film 26 of about 10 nm on the surface of the metal film 25. The conditions of the nitriding treatment are, for example, as follows.

Substrate temperature: 400 ° C. Pressure: 533 Pa (4 Torr) Gas type and flow rate per minute under standard conditions
Ammonia gas, 2000 ml RF power: 1000 W (13.56 MHz) Processing time: 20 seconds Next, using a plasma CVD method, an anti-reflection film 27 is formed on the metal nitride film 26 under the following conditions by about 200 nm. Form.

Substrate temperature: 600 ° C. Gas type and flow rate per minute under standard conditions
Monosilane gas: nitrogen: nitrous oxide = 150 ml: 20
00 ml: 500 ml Pressure: 333 Pa (2.5 Torr) RF power: 1000 W (13.56 MHz) Since the metal film 25 is covered with the metal nitride film 26, the metal film 25 is anti-reflective. It does not react with nitrous oxide, which is a deposition gas for the film 27, and is not oxidized.

Next, under the following conditions, the antireflection film 27
An oxidation treatment is performed by exposing the surface to nitrous oxide plasma to terminate the NH bond on the surface of the antireflection film 27 with oxygen.

Substrate temperature: 400 ° C. Gas type and flow rate per minute under standard conditions
Nitrous oxide, 2000 ml Pressure: 533 Pa (4 Torr) RF power: 1000 W (13.56 MHz) Processing time: 30 seconds Next, the first photo covering the region on the semiconductor substrate 20 where the gate electrode is to be formed A resist pattern 28 is formed on the anti-reflection film 27. Since the NH bonds on the surface of the antireflection film 27 are terminated with oxygen, no footing occurs in which the resist shape after patterning changes to a trapezoidal shape.

Referring to FIG. 2, the anti-reflection film 27 is anisotropically etched using the first photoresist pattern 28 as an etching mask to form a mask pattern 27a of the anti-reflection film pattern. Then the first resist pattern 2
Remove 8

Referring to FIG. 3, the metal film 25 and the metal nitride films 24, 2 are formed by using the mask pattern 27a as an etching mask.
6 and an anisotropically etched impurity-doped polysilicon film 23 to form a polymetal structure including an impurity-doped polysilicon film pattern 23a, a metal nitride film pattern 24a, a metal film pattern 25a, and a metal nitride film pattern 26a. Is formed.

At this time, at the same time when the gate electrode is formed by the etching process, the anti-reflection film pattern 27a of the mask pattern 28 is partially consumed and its thickness is reduced.

Referring to FIG. 4, a spacer 29 made of a nitride film is formed on the side wall of the gate electrode and the mask pattern 27a. For this purpose, the gate electrode and the mask pattern 27a
A silicon nitride film on the semiconductor substrate 20 on which
The entire surface is vapor-deposited with a thickness of 3 mm, and this is etched back again to leave the spacer 29. At this time, the antireflection film pattern 27a is further consumed and remains thin.

Referring to FIG. 5, an etching stop layer 30 is formed to a thickness of about 20 nm on the entire surface of the resultant structure of FIG. The etching stop layer 30 is formed of a silicon nitride film. The formation of the etching stopper layer 30 prevents the oxide film in the field region 21 from being consumed by the etching in the subsequent interlayer insulating film etching process for forming the SAC, and reduces the margin of the etching process. In order to increase the number, this step may be omitted in some cases.

Next, an oxide film such as B
A PSG (boro-phospho-silicate glass, phosphor-boron glass) film is formed to a thickness of 1000 nm, and this is formed by CMP (Chemical Mecha).
An interlayer insulating film 31 is formed by flattening by a nical polishing (chemical mechanical polishing) process.

Thereafter, a second photoresist pattern 32 for defining the SAC formation region is formed on the interlayer insulating film 31. The second photoresist pattern 32 is formed so as to expose the interlayer insulating film 31 in a region between the adjacent gate electrodes.

Since the anti-reflection film pattern 27a still remains on the upper portion of the gate electrode, the influence of irregular reflection by the metal film pattern 25a constituting the gate electrode when forming the second photoresist pattern 30 is obtained. The effect is to reduce.

Referring to FIG. 6, the exposed interlayer insulating film 31 and the underlying etch stop layer 30 are anisotropically etched using the second photoresist pattern 32 as an etching mask. As a result, an insulating film pattern 31a having a spacer 29 formed on the side wall of the gate electrode and a contact hole H exposing the surface of the semiconductor substrate 20 is obtained. Then, the contact hole H is filled with a conductive material and etched back.
A SAC is formed therein.

At this time, the spacer 29 is formed during the etching process.
Even if a part of is etched, an insulation distance between the gate electrode and the SAC formed by filling the contact hole H with a conductive material in a subsequent process can be ensured to obtain a sufficient insulation margin. it can. In most cases, the second photoresist pattern 32 is not accurately aligned in the actual process, but is misaligned in a shifted state as shown in FIG. 5 to form a photoresist pattern.

However, according to the method of the present invention, the anti-reflection film pattern 27a remains on the gate electrode in the step of etching the interlayer insulating film for forming the SAC, and the silicon oxynitride film forming the anti-reflection film pattern 27a is formed. Has a high etching selectivity with respect to the oxide film forming the interlayer insulating film 31. Therefore, even when the misaligned photoresist pattern 32 is formed as in the case of FIG. 5, the exposed portion of the anti-reflection film pattern 27a is etched during the interlayer insulating film etching process for forming the SAC. However, the etching rate is much lower than the oxide film etching rate.

As a result, the anisotropic etching for forming the SAC is performed using the misaligned photoresist pattern 32 to protect the gate electrode when the interlayer insulating film pattern 31a having the contact hole is formed. Only a small amount of the spacer 29 is consumed. Therefore, a sufficient insulation margin between the gate electrode and the SAC formed in the contact hole can be secured.

FIG. 7 shows the film forming temperature of the silicon oxynitride film forming the antireflection film pattern 27a, the etching rate ratio with the oxide film when etching the interlayer insulating film for forming the SAC, and the number of particles increased. is there.

In the present embodiment, the selection ratio necessary to secure a sufficient insulation margin with SAC is 8,
Since a selectivity of 8 and a selectivity of 13 or more can be secured at a film formation temperature of 500 ° C. and 600 ° C., a sufficient selectivity can be obtained by forming a silicon oxynitride film at a film formation temperature of 600 ° C. However, when the film formation temperature of the silicon oxynitride film exceeds 700 ° C., there is a problem that a gas phase reaction mainly occurs and particles increase, and thus the film formation is preferably performed in a temperature range of 500 ° C. to 700 ° C.

Further, SAC is provided in the contact hole H.
After the formation, the antireflection film pattern 27a remains on the gate electrode as before. Accordingly, in a subsequent process, when a photolithography process for forming a direct contact on the SAC through the SAC and connected to the active region of the semiconductor substrate 20 is performed, the metal film forming the gate electrode may be formed. The effect of irregular reflection from the pattern 25a can be reduced by the antireflection film pattern 27a.

[0050]

As described above, according to the present invention, since the plasma CVD method is used for forming the anti-reflection film, optical properties such as a refractive index and an extinction coefficient necessary for reducing the influence of irregular reflection by the metal film are obtained. The constant can be adjusted to the optimum value.

Further, according to the present invention, the method further comprises the step of performing the surface treatment of the antireflection film with the plasma of the oxygen-containing gas after the formation of the antireflection film. -H suppresses the generation of acid in the chemically amplified resist, and does not cause a problem called footing in which the resist shape is deformed into a trapezoidal shape.

Further, since the surface of the metal film is nitrided by the plasma of the nitrogen-containing gas before the formation of the anti-reflection film, it is possible to prevent the metal film from being oxidized when the anti-reflection film is formed.

When an oxide film used as an interlayer insulating film is etched to form a SAC necessary for a highly integrated semiconductor device having a fine design rule of 0.2 μm or less between each gate electrode, an etching mask is used. Even if misalignment occurs during mask alignment in the photolithography process for formation, the silicon oxynitride film, which is an anti-reflection film, is formed at a film formation temperature of 500 ° C. to 700 ° C. by a plasma CVD method. It has a high etching selectivity with respect to the film, and a sufficient insulation margin between the gate electrode and the SAC can be secured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a method of forming a gate electrode and a SAC according to a preferred embodiment of the present invention in the order of steps.

FIG. 2 is a cross-sectional view illustrating a method of forming a gate electrode and a SAC, following FIG. 1, according to a process order;

FIG. 3 is a sectional view illustrating a method of forming a gate electrode and a SAC, following FIG. 2, according to a process order;

FIG. 4 is a sectional view illustrating a method of forming a gate electrode and a SAC, following FIG. 3, according to a process order;

FIG. 5 is a sectional view illustrating a method of forming a gate electrode and a SAC, following FIG. 4, according to a process order;

FIG. 6 is a sectional view illustrating a method of forming a gate electrode and a SAC in accordance with a process order, following FIG. 5;

FIG. 7 is a graph showing the relationship between the film formation temperature of a silicon oxynitride film, the etching rate ratio with an oxide film, and the number of increased particles.

[Explanation of symbols]

 20 Semiconductor substrate 21 Field region 22 Gate oxide film 23 Polysilicon film 23a Polysilicon film pattern 24 Metal nitride film 24a Metal nitride film pattern 25 Metal film 25a Metal film pattern 26 Metal nitride film 26a Metal nitride film pattern 27 Antireflection film 27a Mask Pattern 28 first photoresist pattern 29 spacer 30 etching stop layer 31 interlayer insulating film 31a insulating film pattern 32 second photoresist pattern H contact hole

Front page of the continued F-term (reference) 4M104 AA01 BB01 BB04 CC05 DD02 DD04 DD08 DD19 DD37 DD43 DD55 DD66 DD86 DD89 EE14 EE17 FF13 FF18 GG08 GG13 HH14 5F033 HH04 HH15 HH18 HH19 HH33 HH34 MM08 NN40 PP09 PP15 QQ04 QQ08 QQ09 QQ16 QQ25 QQ28 QQ30 QQ31 QQ37 QQ48 QQ90 RR06 RR08 RR15 SS15 TT08 XX15 5F040 EC02 EC04 EC07 EH08 EJ07 FA00 FA03 FA07 FC00 FC22

Claims (10)

[Claims] A step of sequentially depositing a polysilicon film and a metal film on a substrate on which a gate insulating film is formed, and forming a silicon oxynitride film also functioning as an antireflection film on the metal film by a plasma CVD method. Forming and plasma C
Exposing the silicon oxynitride film to a plasma of oxygen-containing gas after forming the silicon oxynitride film by a VD method to perform a surface treatment for terminating the NH bond on the surface of the silicon oxynitride film with oxygen; A step of applying a resist film, a step of forming the resist film into a desired pattern shape by a lithography step, a step of transferring the desired pattern shape by etching the silicon oxynitride film, and a step of transferring the desired pattern shape Etching the metal film and the polysilicon film using the processed silicon oxynitride film as a hard mask to form a gate electrode having a polymetal structure having an antireflection film pattern laminated thereon. A method for manufacturing a semiconductor device. 2. The method according to claim 1, wherein, in the step of forming the silicon oxynitride film, a film forming temperature when the silicon oxynitride film is formed by the plasma CVD method is 500 ° C. or more and 700 ° C. or less. The manufacturing method of the semiconductor device described in the above. 3. The method according to claim 1, wherein the plasma of the oxygen-containing gas is one of nitrous oxide plasma and oxygen plasma. 4. The step of forming the silicon oxynitride film, wherein the surface of the metal film is nitrided in a plasma of a gas containing nitrogen before the formation of the silicon oxynitride film by the plasma CVD method. The method of manufacturing a semiconductor device according to claim 1, wherein 5. The method according to claim 4, wherein the plasma of the nitrogen-containing gas is ammonia plasma or nitrogen plasma. 6. A step of forming a conductive layer on a substrate on which a gate insulating film is formed, and forming a silicon oxynitride film, which also functions as an antireflection film, on the conductive layer at a temperature of 500 ° C. by a plasma CVD method. A step of forming the silicon nitride film at a temperature of 700 ° C. or lower and a surface treatment of exposing the silicon nitride film to N-H bonds on the surface of the silicon nitride film with oxygen after the silicon nitride film is formed by the plasma CVD method. Performing, a step of applying a resist film to the silicon oxynitride film, a step of forming the resist film into a desired pattern shape by a lithography step, and etching the silicon oxynitride film to form the desired pattern shape. Transferring the conductive layer and the polysilicon film using the silicon oxynitride film processed into the desired pattern shape as a hard mask. Etching to form a plurality of gate electrodes having an anti-reflection film pattern laminated thereon, and depositing a first insulating film on the top and side walls of each gate electrode and anti-reflection film pattern; Forming a spacer made of the first insulating film on a side wall of each of the gate electrodes and the antireflection film pattern by anisotropically etching the first insulating film; Forming an interlayer insulating film so as to cover, and forming a contact hole exposing the first insulating film and the substrate between the respective gate electrodes by etching a part of the interlayer insulating film by a lithography method And a step of forming a contact by filling a conductive member in the contact hole. 7. The method according to claim 10, wherein the conductive layer has a stacked structure of a doped polysilicon film and a metal film. 8. The method according to claim 6, wherein the first insulating film is made of a silicon nitride film. 9. The method according to claim 1, further comprising, before forming the interlayer insulating film, forming a second insulating film functioning as an etching stopper layer on the substrate so as to cover the gate electrode and the spacer. The method for manufacturing a semiconductor device according to claim 6, wherein: 10. The method according to claim 9, wherein the second insulating film is made of a silicon nitride film.