JP2001168097A - Method of forming wiring, method of manufacturing semiconductor device and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the forming of high-performance polymetal wirings at low cost by extremely easily and reliably preventing metal films from being oxidated using the conventional film forming apparatus, without any troublesome additional means or additional processes in adopting the polymetal technology, thus greatly contributing to the manufacturing of the next generation integrated circuits. SOLUTION: After forming a W film 13 through a WN film 12 for avoiding reactions on a polycrystalline Si film 11, a WN film 14 is formed on the W film 13 as a protection thin film for preventing the abnormal oxidation of the W film 13 by the sputtering method, the same as forming the WN film 12, in an environment not oxidating the W film 13, concretely under a film forming setting condition such as in a high vacuum or in an atmosphere not containing oxygen in situ, then an SiN film 15 is formed and the films 11-15 are patterned into wiring shapes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for forming a wiring,
The present invention relates to a method for manufacturing a semiconductor device and a semiconductor device, and is particularly suitable for forming a gate electrode and the like.

[0002]

2. Description of the Related Art Conventionally, metal wiring is mainly used as a so-called back-end process (a wiring forming process after a main process of a transistor typified by formation of a gate electrode and a source / drain) is completed in a manufacturing process of a semiconductor device. Point.).

In recent years, with the progress of miniaturization and high performance of MOS transistors, there is a strong demand for reducing the sheet resistance of a gate electrode. In order to meet this demand, attempts have been made to form a polycide layer formed by laminating a silicide film of a refractory metal such as W on a polycrystalline silicon film using a gate electrode as a metal wiring.

However, as the miniaturization of LSIs progresses, it is becoming difficult to reduce the resistance as much as expected with the refractory metal silicide technology such as W.
In order to achieve a reduction to an extent that meets recent requirements, it is necessary to increase the film thickness, which hinders the demand for miniaturization.

[0005] Therefore, in order to further reduce the sheet resistance and to exhibit high heat resistance, tungsten (W) or the like is formed on the polycrystalline silicon film through a reaction prevention film such as tungsten nitride (WN). A technique of forming a gate electrode by laminating a pure metal film, that is, forming a so-called polymetal electrode has been studied. According to this polymetal technology, it is possible to reduce the resistance of wiring without forming a pure metal film thick, and it can be applied to DRAMs and the like because of its excellent heat resistance.

[0006]

When the polymetal technique is used, it is necessary to prevent the oxidation of the upper pure metal film in the manufacturing process. For this reason, conventionally, as shown in FIG. 4A, a W film 104 is formed on a polycrystalline silicon film 102 over a semiconductor substrate 101 via a tungsten nitride film (WN film) 103, and then a heat treatment is performed. A silicon nitride film (SiN film) 105 having a thickness of about 200 nm was formed as an oxidation resistant film to prevent oxidation of the W film 104.

However, in this case, the oxidation resistant film SiN
There is a problem in the formation of the film 105 itself. That is, since the film formation process is performed at a high temperature of about 780 ° C., the surface of the W film 104 is oxidized by the influence of the entrained oxygen generated in a small amount. As a result, as shown in FIG.
Needle-like whiskers 106 are formed on the surface of the film 104.

As a countermeasure against this problem, a so-called load lock chamber is provided in a film forming apparatus used for forming a silicon nitride film in order to prevent the influence of entrained oxygen, and the substrate is temporarily held in the load lock chamber. After completely replacing the entrained oxygen with a gas such as N ₂ or Ar, the substrate is introduced into the film forming chamber or a so-called low-temperature load-in (once the temperature in the film forming apparatus is set to about 400 ° C. (usually, in the apparatus). Is maintained at about 600 ° C. in consideration of throughput.)
After loading the wafer into the apparatus, the atmosphere inside the apparatus is sufficiently replaced, and then a special method such as performing a film formation by raising the film formation temperature to 780 ° C.) is performed.

As described above, conventionally, the adoption of the polymetal technology makes it possible to reduce the wiring resistance in response to recent demands for high performance and miniaturization. On the other hand, however, a detour means such as a load lock chamber is provided. However, there is a serious problem that the cost of the entire process apparatus is increased, and a special process such as low-temperature load-in is added, so that the throughput is significantly reduced.

In view of the above, according to the present invention, when a polymetal technique is employed, a conventional film-forming apparatus can be used to prevent oxidation of a metal film very easily and reliably without the need for complicated additional means and additional steps. It is an object of the present invention to provide a method for forming a wiring, a method for manufacturing a semiconductor device, and a semiconductor device, which can form a polymetal wiring at low cost and can greatly contribute to the manufacture of a next-generation integrated circuit. .

[0011]

The present invention has the following aspects to solve the above-mentioned problems.

According to a first aspect of the present invention, there is provided a method for forming a wiring, comprising the steps of: forming a silicon film on a substrate; forming at least a metal film on the silicon film; A step of forming a protective thin film on the surface of the metal film in an environment in which the metal film is not subsequently oxidized; a step of removing the substrate from the environment; and a step of forming an oxidation-resistant film on the protective thin film. ,at least,
Processing the oxidation-resistant film, the protective thin film, the metal film, and the silicon film into a wiring shape.

In the first aspect, it is preferable that the protective thin film is one selected from WN, TiN, SiN, SiO ₂ and WSi ₂ .

A second aspect of the present invention is characterized in that the method for forming a wiring according to the first aspect is applied to the formation of a gate electrode and is used in a method for manufacturing a semiconductor device.

A third aspect of the present invention is a semiconductor device, wherein a gate electrode has at least a metal film and an oxidation resistant film laminated on a silicon film, and a protective thin film is provided between the metal film and the oxidation resistant film. It is characterized by being formed.

[0016]

In the present invention, the surface of a metal film laminated on a silicon film is formed on the surface of the metal film in an environment in which the metal film is not oxidized subsequent to the formation of the metal film, specifically, in situ.
u, a protective thin film is formed under a film-forming setting state such as in a high vacuum or oxygen-free atmosphere. As the protective thin film, one that can be formed relatively easily is selected. Due to the presence of this protective thin film, the lower metal film is protected from oxidation due to entrained oxygen generated when the upper oxidation resistant film is formed. Therefore, it is possible to continuously execute each step of wiring formation with the conventional apparatus configuration without requiring any special additional means or additional steps, and to easily and surely introduce the polymetal technology to reduce the resistance of the wiring. Can be planned.

[0017]

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

(First Embodiment) In this embodiment, a case where the present invention is applied to a case where a metal wiring of a predetermined semiconductor device is formed by a polymetal technique will be exemplified. In the present embodiment, for convenience, the configuration of the metal wiring will be described together with its forming process.

First, as shown in FIG. 1A, a polycrystalline silicon film 11 is formed to a thickness of 70 n on a silicon semiconductor substrate 1 in a chamber of a CVD apparatus by, for example, a low pressure CVD method.
m. This polycrystalline silicon film may be an amorphous silicon film. Normally, an amorphous silicon film is crystallized by a heat treatment in a later step and is changed into a polycrystalline silicon film.

Next, the semiconductor substrate 1 is set in a chamber of a sputtering apparatus, nitrogen (N ₂ ) gas is introduced, and a film thickness of 5 nm is formed on the surface of the polycrystalline silicon film 11 by a sputtering method.
A thin tungsten nitride (WN) film 12 is formed. The WN film 12 serves to establish electrical continuity between the polycrystalline silicon film 11 and a tungsten (W) film 13 described later, and to prevent a chemical reaction between the two. Next, a W film 13 is deposited on the WN film 12 as a metal film to a thickness of about 40 nm by sputtering.

Subsequently, as shown in FIG.
In an environment where the W film 13 is not oxidized following the formation of
Specifically, in the in-situ, high-vacuum or oxygen-free atmosphere setting conditions, the W film 13 is prevented from being abnormally oxidized on the W film 13 by the sputtering method similarly to the formation of the WN film 12. To form a protective thin film. here
In situ, that is, by introducing N ₂ gas into the same chamber, the N film is caught on the surface of the W film 13 and the W film 1 is affected by oxygen.
A thin WN film 14 having a thickness of about 5 nm is formed as a protective thin film for preventing oxidation of No. 3. The polycrystalline silicon film 11, the W film 13, and the WN film 14 via the WN film 12
A tungsten polymetal layer 21 is formed.

Here, the W film 13 may be deposited and formed by the CVD method, and the WN film 14 may be formed by the CVD method in the same chamber of the CVD apparatus. Further, according to the amount of entrained oxygen, for example, when the amount of entrained oxygen is relatively large, the WN film 14 may be adjusted so as to increase the thickness accordingly.

The protective thin film may be any one as long as it is in the above-mentioned film formation setting state and can suppress the influence of entrained oxygen. In addition to the WN film, titanium nitride (TiN) which is hardly oxidized as compared with a pure metal is used. And) a film having complete oxidation resistance, such as a film or a nitride film. Furthermore, a silicon oxide film (LTO film) formed at a low temperature can be applied as long as the lower W film 13 is not oxidized at the film formation temperature.
This is because, although the silicon oxide film allows permeation of entrained oxygen, even if the entrained oxygen diffuses in the silicon oxide film, W
This is because the W film 13 is not oxidized because the gas in the chamber is purged before reaching the surface of the film 13.

Subsequently, the semiconductor substrate 1 is carried out of the chamber, and the semiconductor substrate 1 is washed by a usual method (for example, a wet treatment using diluted sulfuric acid) as a pretreatment for forming an oxidation resistant film.

Subsequently, as shown in FIG.
A silicon nitride film (Si) having a thickness of about 200 nm as an oxidation resistant film on the W film 13 at a temperature of about 780 ° C.
An N film 15 is formed. At this time, due to the presence of the WN film 14, the W film 13 is not affected by the entrained oxygen even at a relatively high temperature of about 780 ° C.

Thereafter, as shown in FIG. 1D, the SiN film 15, the WN film 14, the W film 13, and the WN film 12 are formed by photolithography and subsequent dry etching.
Then, the polycrystalline silicon film 11 is processed into a wiring shape, and a tungsten polymetal wiring 22 is pattern-formed on the upper layer of the semiconductor substrate 1.

As described above, according to the forming method of the present embodiment, when the polymetal technique is employed, complicated and complicated additional means and additional steps are not required, and it is extremely easy and reliable to use a conventional film forming apparatus. In addition, it is possible to form a high-performance polymetal wiring at a low cost by preventing the oxidation of the metal film, here, the W film 13, thereby greatly contributing to the manufacture of next-generation integrated circuits.

Specifically, oxidation resistance of a metal film by a protective thin film
An experimental example examining the sexual effect will be described. This experiment was
Form SiN film as oxidation resistant film required for remetal wiring
The purpose of this study is to examine the effect of entrained oxygen on
Low-temperature silicon oxide film (LTO) as protective thin film
In this state, the semiconductor substrate 1 is annealed under various temperature conditions.
The change in sheet resistance, which is an index of oxidation of the W film,
Specified. Here, LTO is formed at a film forming temperature of 400 ° C.
And annealing conditions are 500 ° C. to 10 ° C.
A large amount of entrained oxygen exists at each temperature of 00 ° C
Open N _TwoHeat treatment under atmosphere for 10 minutes
Was.

FIG. 2 shows the experimental results. Usually, when an SiN film is formed as an oxidation-resistant film on a W film having no protective thin film, the W film is easily oxidized at a temperature of about 600 ° C. On the other hand, according to FIG.
No increase in sheet resistance was observed at each of the
It can be seen that O shows extremely high oxidation resistance of the W film against entrained oxygen.

Although the present embodiment has exemplified the case where the W film is formed as the metal film of the polymetal wiring, the present invention is not limited to this, and the low-resistance metal film is, for example, Ta, Mo or the like. It is also preferable to form a thin film.

(Second Embodiment) This embodiment exemplifies a case where the present invention is applied to a method of manufacturing a MOS transistor in which a gate electrode is formed by a polymetal technique. In the present embodiment, the configuration of the MOS transistor will be described together with its manufacturing process for convenience. Note that the same reference numerals are given to constituent members and the like common to the first embodiment, and description thereof will be omitted.

FIG. 3 is a schematic sectional view showing a method of manufacturing the MOS transistor according to the present embodiment in the order of steps. First, after defining an element active region (not shown) by forming an element isolation region, as shown in FIG.
4 nm on a P-type silicon semiconductor substrate 1 by thermal oxidation
A silicon oxide film 2 serving as a gate insulating film is formed so as to have a thickness of the order of.

Subsequently, as shown in FIG. 3B, a gate electrode 3 is formed on the silicon oxide film 2 by using a polymetal technique. Specifically, the method is almost the same as the method of forming the metal wiring described in the first embodiment with reference to FIG. Here, a so-called tungsten polymetal electrode formed by forming a tungsten film on a polycrystalline silicon film is exemplified as the gate electrode.

First, for example, by a low pressure CVD method,
The polycrystalline silicon film 11 is formed to a thickness of 70 in the chamber of the apparatus.
It is deposited to a thickness of about nm. Next, the semiconductor substrate 1 is set in a chamber of a sputtering apparatus, a nitrogen (N ₂ ) gas is introduced, and a thin tungsten nitride (WN) film having a thickness of about 5 nm is formed on the surface of the polycrystalline silicon film 11 by a sputtering method. 1
Form 2 The WN film 12 is a polycrystalline silicon film 1
1 to electrically connect a tungsten (W) film 13 described later to prevent a chemical reaction between the two.
Next, W is used as a metal film on the WN film 12 by sputtering.
A film 13 is deposited to a thickness of about 40 nm.

Subsequently, following the formation of the W film 13, the W film 1
In an environment in which no. 3 is not oxidized, specifically, in a film formation setting state such as in situ, in a high vacuum, or in an atmosphere containing no oxygen, W
A protective thin film for preventing abnormal oxidation of the W film 13 is formed on the film 13. Here, in situ, that is, by introducing N ₂ gas into the same chamber, a thin WN film having a thickness of about 5 nm is formed as a protective thin film for preventing the W film 13 from being entrapped on the surface of the W film 13 and oxidized by the influence of oxygen. The film 14 is formed. The polycrystalline silicon film 11, the W film 13, and the WN film 14 via the WN film 12 form a tungsten polymetal layer 21.

Here, the W film 13 may be deposited and formed by the CVD method, and the WN film 14 may be formed by the CVD method in the same chamber of the CVD apparatus. Further, according to the amount of entrained oxygen, for example, when the amount of entrained oxygen is relatively large, the WN film 14 may be adjusted so as to increase the thickness accordingly.

The protective thin film may be any one as long as it is in the above-mentioned film formation setting state and can suppress the influence of entrained oxygen. In addition to the WN film, titanium nitride (TiN) which is hardly oxidized as compared with a pure metal is used. And) a film having complete oxidation resistance, such as a film or a nitride film. Furthermore, a silicon oxide film (LTO film) formed at a low temperature can be applied as long as the lower W film 13 is not oxidized at the film formation temperature.
This is because, although the silicon oxide film allows permeation of trapped oxygen, even if trapped oxygen diffuses in the silicon oxide film, W
This is because the W film 13 is not oxidized because the gas in the chamber is purged before reaching the surface of the film 13.

Subsequently, the semiconductor substrate 1 is carried out of the chamber, and the semiconductor substrate 1 is washed by a usual method (for example, a wet treatment using diluted sulfuric acid) as a pretreatment for forming an oxidation resistant film.

Subsequently, a silicon nitride film (SiN film) 15 having a thickness of about 200 nm is formed on the WN film 14 at a temperature of about 780 ° C. by a CVD method. At this time, WN
Due to the presence of the film 14, the W film 13 is not affected by the entrained oxygen even at a relatively high temperature of about 780 ° C.

Then, by photolithography and subsequent dry etching, the SiN film 15 and the WN film 1 are formed.
4, the W film 13, the WN film 12, the polycrystalline silicon film 11, and the silicon oxide film 17 are processed into an electrode shape, and a gate electrode 3, which is a tungsten polymetal electrode, is patterned on the gate insulating film 2.

Next, using the gate electrode 3 as a mask, an n-type impurity, here arsenic (As ⁺ ), is applied to the surface layer of the semiconductor substrate 1 on both sides of the gate electrode 3 at an acceleration energy of 10 keV and a dose of 1 × 10 ¹⁴ / cm ^2. Ion implantation under the conditions of
The D layer 16 is formed.

Next, as shown in FIG. 3C, a SiN film is deposited and formed so as to cover the gate electrode 3, and then this SiN film is deposited.
By performing anisotropic etching on the entire surface of the N film, the SiN film is left only on the side surfaces of the gate electrode 3 to form the sidewalls 4.

Next, as shown in FIG. 3D, using the SiN film 15 and the side wall 4 as a mask, an n-type impurity, here arsenic (As ⁺ ), is formed on the surface layer of the semiconductor substrate 1 on both sides of the gate electrode 3. Is implanted under the conditions of an acceleration energy of 20 keV and a dose of 4 × 10 ¹⁵ / cm ² ,
The source / drain 5 is formed by performing an annealing process for about 10 seconds at a temperature condition of ° C.

Thereafter, an interlayer insulating film for burying the gate electrode 3 and the like is formed, and various wiring layers electrically connected to the source / drain 5 and the like via the contact holes are formed.
Complete the MOS transistor.

As described above, according to the manufacturing method of the present embodiment, when the polymetal technology is adopted, complicated and complicated additional means and additional steps are not required, and it is extremely easy and reliable to use a conventional film forming apparatus. In addition, a high-performance polymetal electrode can be formed at low cost by preventing the oxidation of the metal film, here, the W film 13, which can greatly contribute to the manufacture of next-generation integrated circuits.

Although the present embodiment has exemplified the case where the W film is formed as the metal film of the polymetal electrode, the present invention is not limited to this. For example, the low-resistance metal film such as Ta, Mo or the like may be used. It is also preferable to form a thin film.

In this embodiment, a MOS transistor has been described as an example. However, the present invention is not limited to this, and may be applied to other various semiconductor elements and semiconductor memories.

The following embodiments also constitute the present invention.

Embodiment 1 is a method for forming a wiring, characterized in that a reaction preventing film for both is formed between the silicon film and the metal film.

Embodiment 2 is a method for forming a wiring, characterized in that the environment is under one kind of film formation setting selected from in situ, high vacuum or an atmosphere containing no oxygen. .

Embodiment 3 is a method for forming a wiring, wherein the metal film is formed by a sputtering method in a film forming chamber.
The protective thin film is formed in the same film forming chamber by a sputtering method.

A fourth aspect is a method for forming a wiring, wherein the metal film is formed by a CVD method in a film forming chamber, and the protective thin film is formed by a CVD method in the same film forming chamber. And

A fifth aspect of the present invention is a method of forming a wiring, wherein after forming the metal film, the substrate is transferred in a high vacuum to form the protective thin film.

Each of the forming methods according to the first to fifth aspects is applied to a method for manufacturing a semiconductor device, and is used for forming a gate electrode or various wirings of the semiconductor device.

A sixth aspect is a wiring in which at least a metal film and an oxidation resistant film are laminated on a silicon film, wherein a protective thin film is formed between the metal film and the oxidation resistant film. And

[0056]

According to the present invention, when a polymetal technique is adopted, the oxidation of a metal film can be prevented very easily and reliably using a conventional film forming apparatus without requiring complicated additional means or additional steps. Thus, a high-performance polymetal wiring can be formed at a low cost, which can greatly contribute to the manufacture of a next-generation integrated circuit.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a method of forming a polymetal metal wiring according to a first embodiment in the order of steps.

FIG. 2 is a characteristic diagram illustrating a relationship between a processing temperature and a sheet resistance value of a metal film when a protective thin film is formed and an annealing process is performed.

FIG. 3 is a schematic cross-sectional view showing a method for manufacturing a MOS transistor according to a second embodiment in the order of steps.

FIG. 4 is a schematic sectional view showing formation of a conventional polymetal metal wiring.

[Explanation of symbols]

 Reference Signs List 1 silicon semiconductor substrate 2 gate insulating film 3 gate electrode 4 side wall 5 source / drain 11 polycrystalline silicon film 12 WN film (for reaction prevention) 13 W film 14 WN film (for oxidation prevention) 15 SiN film 16 LDD layer 17 silicon Oxide film 21 Tungsten polymetal layer 22 Tungsten polymetal wiring

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 4M104 AA01 BB01 DD04 DD37 DD41 DD62 DD65 EE06 EE12 EE14 EE17 FF18 GG09 HH16 5F033 HH04 HH19 HH20 HH21 HH28 HH32 HH33 HH34 HH35 KK01 PP09 PP15 QQ10Q11 Q06 Q08 XX10

Claims (5)

[Claims] A step of forming a silicon film on a substrate; a step of forming at least a metal film on the silicon film; and an environment in which the metal film is not oxidized following the formation of the metal film. Forming a protective thin film on the surface of the substrate; removing the substrate from the environment; forming an oxidation-resistant film on the protective thin film; at least the oxidation-resistant film, the protective thin film, and the metal film And processing the silicon film into a wiring shape. 2. The method according to claim 1, wherein the protective thin film is made of WN, TiN, Si.
N, SiO_Two, WSi _TwoThat it is one kind selected from
The method for forming a wiring according to claim 1, wherein: 3. A method of manufacturing a semiconductor device having a gate electrode and a source / drain, wherein, when forming the gate electrode, a step of forming a silicon film on a semiconductor substrate; and at least a metal film on the silicon film. Forming a protective thin film on the surface of the metal film in an environment where the metal film is not oxidized following the formation of the metal film; and removing the substrate from the environment; Manufacturing a semiconductor device, comprising: forming an oxidation-resistant film on a thin film; and processing at least the oxidation-resistant film, the protective thin film, the metal film, and the silicon film into a gate electrode shape. Method. 4. The protective thin film is made of WN, TiN, Si.
N, SiO_Two, WSi _TwoThat it is one kind selected from
The method for manufacturing a semiconductor device according to claim 3. 5. A semiconductor device having a gate electrode and a source / drain, wherein the gate electrode is formed by stacking at least a metal film and an oxidation-resistant film on a silicon film, and the metal film, the oxidation-resistant film, A semiconductor device, wherein a protective thin film is formed therebetween.