JPH11238880A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing semiconductor devices, which enables cleaning after forming a tungsten nitride film. SOLUTION: The method contains a film formation process in which plural layers 15, 16 and 17 of conductor films, including a tungsten nitride film 16, are formed on a semiconductor substrate 11, a patterning process to shape the conductor films 15, 16 and 17 into a specified pattern, and a cleaning process to clean the patterned conductor films 15, 16 and 17, wherein a heat treatment process is executed after the process step of forming the tungsten nitride film 16 in the film formation process, and before the cleaning process, to crystallize the tungsten nitride film 16 to change to a crystallized tungsten nitride film 13a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device using a refractory metal nitride for a gate electrode.

[0002]

2. Description of the Related Art MOSFETs (Metal Oxids) constituting integrated circuits
The gate electrode of e Semiconductor Feild Effect Transistor (MOS type field effect transistor) is generally made of polycrystalline silicon. However, as the gate length of the gate electrode is shortened due to the high integration of the LSI, the wiring resistance of the gate electrode is increased, which causes a problem of delay in signal propagation speed. Therefore, WSi ₂ , TiSi ₂ , which are materials having lower resistance than polycrystalline silicon,
It has been proposed to use an alloy (silicide) of silicon having a high melting point such as MoSi ₂ and silicon, and stack this silicide layer and a polycrystalline silicon layer to form a gate electrode having a two-layer structure. However, as the degree of integration of LSI further increases, a gate electrode having a lower resistance than the gate electrode having the two-layer structure is required, and tungsten has been attracting attention as a gate electrode material that satisfies such requirements. As an example, K. Kasai et al., "W / WNx / Poly-Si Gate Technology for
Future High Speed Deep Submicron CMOS LSIs ”, 1
994 International Electron Devices Conference
rence), a gate electrode having a three-layer structure of a polycrystalline silicon layer, a tungsten nitride layer, and a tungsten layer
A MOSFET is proposed. In this structure, the tungsten nitride layer is disposed to prevent the polycrystalline silicon layer and the tungsten layer from reacting to form a high-resistance silicide layer. The tungsten nitride layer is
It is deposited by a reactive sputtering method.

[0003]

However, according to a study by the inventors, when manufacturing a MOSFET having a gate electrode having a three-layer structure of a polycrystalline silicon layer, a tungsten nitride layer, and a tungsten layer, a tungsten nitride layer is required. Was found to be problematic in the resistance to the cleaning solution. That is, when a MOSFET having this three-layered gate electrode is manufactured by a generally known method, the tungsten nitride layer may be dissolved in a cleaning solution and disappear. This will be further described with reference to FIGS. When manufacturing a MOSFET having this three-layered gate electrode by a generally known method, first, a field oxide film 13 for element isolation and a p-type well layer 12 are formed on a silicon substrate 11. Next, after a gate oxide film 14 is formed by a thermal oxidation method, the polycrystalline silicon film 1 is formed thereon.
5 is deposited by a chemical vapor deposition method (hereinafter referred to as a CVD method) (FIG. 1A).

A tungsten nitride film 16 and a tungsten film 17 are formed on the polycrystalline silicon film 15 by a sputtering method. The tungsten nitride film 16 is in an amorphous state when formed by a sputtering method. Thereafter, a silicon nitride film 18 is formed on the tungsten film 17 by a plasma CVD method (FIG. 1B).

Next, patterning is performed by a usual photolithography method, and a total of four layers of a polycrystalline silicon film 15, a tungsten nitride film 16, a tungsten film 17, and a silicon nitride film 18 are processed into a shape of a gate electrode by dry etching. (FIG. 1 (c)). During the dry etching, the etching gas and the resist or the material of the four layers constituting the gate electrode react to generate a compound, and the compound adheres to the side wall of the gate electrode. Therefore, after the dry etching is completed, the substrate shown in FIG. 1C is washed to remove the product film attached to the side wall of the gate electrode.

Thereafter, a source region and a drain region are formed in the p-type well layer 12, and a source electrode, a drain electrode, an insulating layer and the like are formed to complete the MOSFET.

In the above-mentioned cleaning, a cleaning solution generally used in a semiconductor manufacturing process, for example, a mixed solution of ammonia water, hydrogen peroxide solution and ultrapure water, hydrochloric acid, hydrogen peroxide solution and ultrapure water A mixed solution of hydrofluoric acid diluted with ultrapure water, a mixed solution of hydrofluoric acid, hydrogen peroxide water and ultrapure water, or the like is used.

However, according to the inventors' evaluation,
As described above, it was found that the tungsten nitride film 16 formed by the sputtering method was easily dissolved in the cleaning liquid. Therefore, it has been found that in the above-described cleaning step, the tungsten nitride film 16 may be etched from the side surface of the gate electrode or may be lost in the worst case. However, if cleaning is not performed for fear of dissolution of the tungsten nitride film 16, the device characteristics will be deteriorated.

The present invention has been made in view of the above problems, and is a method of manufacturing a semiconductor device using tungsten nitride. The method of manufacturing a semiconductor device which enables cleaning after forming a tungsten nitride film is provided. To provide.

[0010]

According to the present invention, there is provided the following method of manufacturing a semiconductor device.

That is, a film forming step of forming a plurality of conductor films including a tungsten nitride film on a semiconductor substrate, and a processing step of patterning the conductor film into a desired shape;
A cleaning step of cleaning the processed conductor film, and crystallizing the tungsten nitride film after the step of forming the tungsten nitride film in the film forming step and before the cleaning step. This is a method for manufacturing a semiconductor device in which a step of heat-treating the tungsten nitride film is performed to make the tungsten nitride film heat-treated.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, a method of manufacturing a MOS field effect transistor (MOSFET) using a three-layer film containing tungsten nitride as a gate electrode will be described.

First, as shown in FIG. 2A, a field oxide film 13 for element isolation is formed on a silicon substrate 11 by a known method, and then a p-type well layer 12 is formed. Further, the surface of the silicon substrate 11 between the field oxide films 13 is thermally oxidized to form a silicon oxide film having a thickness of about 10 nm. This silicon oxide film is called a gate oxide film 14. Next, a polycrystalline silicon film 15 doped with phosphorus is deposited on the gate oxide film 14 to a thickness of about 100 nm by a chemical vapor deposition method (FIG. 2A).

Next, a tungsten nitride film 16 and a tungsten film 17 are sequentially formed on the polycrystalline silicon film 15 by sputtering to have a thickness of 10 nm and 100 nm, respectively.
As a target at the time of this sputtering, tungsten is used for both the tungsten nitride film 16 and the tungsten film 17. When the tungsten nitride film 16 is formed, nitrogen gas is introduced into the plasma to nitride and deposit tungsten. The tungsten nitride film 16 deposited by this method is in an amorphous state when deposited. Next, a 200 nm-thick silicon nitride film 18 is formed on the tungsten film 17 at a low temperature of about 400 ° C. by a plasma CVD method (FIG. 2B).

Next, heat treatment is performed at 900 ° C. for 1 minute in a nitrogen atmosphere using a rapid heat treatment apparatus. This heat treatment changes the amorphous tungsten nitride film 16 into a crystallized tungsten nitride film 16a (FIG. 2).
(C)). As a result of analysis by the X-ray diffraction method, it was confirmed that the tungsten nitride film 16a contained a W ₂ N crystal.

Next, patterning is performed by a usual photolithography method, and a total of four layers of a polycrystalline silicon film 15, a tungsten nitride film 16a, a tungsten film 17 and a silicon nitride film 18 are processed into a shape of a gate electrode by dry etching. (FIG. 2 (d)). Of these four layers, the polycrystalline silicon film 15, the tungsten nitride film 16a
The three layers of the tungsten film 17 function as the gate electrode 19. During the dry etching, the etching gas and the resist or the material of the four layers constituting the gate electrode react with each other to generate a compound, and the compound adheres to the side wall of the gate electrode. After the completion, the substrate shown in FIG. 2D is washed to remove the product film attached to the side wall of the gate electrode. Washing is
Perform in two stages. First, 28wt% ammonia water and 30w
t% hydrogen peroxide solution and ultrapure water in a volume ratio of 1: 0.05:
30 and heated to 40 ° C. as a cleaning liquid, and the Si substrate 11 on which the gate electrode is formed is contained in the cleaning liquid.
For 5 minutes to perform the first cleaning. After washing with water for 10 minutes, 50 wt% hydrofluoric acid and 30 wt%
The second cleaning is performed for 5 minutes using a cleaning liquid in which a hydrogen peroxide solution and ultrapure water are mixed at a volume ratio of 1: 10: 500.

Thereafter, as shown in FIG. 3E, an n ⁺ -type source region 20 and an n ⁺ -type drain region 21 are formed in the p-type well layer 12, and a polycrystalline silicon film 15 and a tungsten nitride film are formed. The side surfaces of the four layers 16a, the tungsten film 17 and the silicon nitride film 18 are covered with the silicon nitride film 22. Further, after the entire surface is covered with the insulating film 23, n
^A source electrode 24 and a drain electrode 25 reaching the ⁺ type source region 20 and the n ⁺ type drain region 21, respectively, are formed to complete the MOSFET. The gate electrode 1
The polycrystalline silicon film 15 of the three layers constituting the layer 9 is arranged to improve the adhesion between the lower gate oxide film 14 and the gate electrode 19. The tungsten nitride film 16a is arranged to prevent the tungsten film 17 from reacting with the polycrystalline silicon film 15 to generate high-resistance silicide.

As described above, the MOSFET of the present embodiment
It is provided with the tungsten nitride film 16a, a tungsten nitride film 16a, and crystallized prior to the cleaning process, W ₂
The tungsten nitride film 16a containing N crystal is used. The tungsten nitride film 16a crystallized to include the W ₂ N crystal does not dissolve in a general cleaning solution, so that the side surface of the tungsten nitride film 16a of the gate electrode 19 is not etched. For confirmation, after the cleaning process (Fig. 2
When the cross section of the gate electrode 19 in (d) was observed by SEM (scanning electron microscope), the sidewall of the tungsten nitride film 16a was hardly etched, and there was no problem in the shape of the gate electrode 19.

On the other hand, for comparison, the step of heat treatment for crystallization shown in FIG.
As it was, a comparative sample was manufactured under the same other conditions.
When the shape of the gate electrode 19 after the cleaning step (FIG. 2D) was similarly observed for this comparative sample, the tungsten nitride film 16 had a thickness of 20 to 30 nm inward from the side wall.
Had been etched.

Thus, as in the present embodiment, a step of crystallizing the tungsten nitride film to include the W ₂ N crystal before the cleaning step is performed, whereby the tungsten nitride film from the side wall of the tungsten nitride film is removed. Although etching and disappearance could be prevented, it was confirmed. Therefore, according to the manufacturing method of the present embodiment, a low-resistance tungsten film and a tungsten nitride film can be used as the gate electrode 19,
It is possible to manufacture a highly reliable MOSFET having stable element characteristics.

In this embodiment, the heat treatment process for turning the tungsten nitride film 16 into the crystallized tungsten nitride film 16a is performed after the formation of the silicon nitride film 18. This may be performed before, after the tungsten film 17 is formed, or after the dry etching process.

Although the heat treatment is performed at 900 ° C. in this embodiment, the temperature of the heat treatment is
Any temperature may be used as long as W ₂ N crystal is generated. Specifically, 500
A treatment in the range of ~ 1000 ° C is desirable.

Also, the step after the formation of the tungsten nitride film 16 and before the cleaning step is a high-temperature step similar to the heat treatment step, so that this step can also be used as a heat treatment step. Can be. For example, in the present embodiment, the silicon nitride film 18 is formed at a low temperature of about 400 ° C. by the plasma CVD method after the tungsten nitride film 16.
The process can be changed to a process of forming a film by a low pressure CVD method at about 0 ° C. In this case, the silicon nitride film 1
Since the tungsten nitride film 16 is crystallized during the film forming process of No. 8, it is not necessary to separately provide the heat treatment in the nitrogen atmosphere described in the above embodiment.

In the present embodiment, a case where a mixed solution of ammonia water, hydrogen peroxide solution and ultrapure water, or a mixed solution of hydrofluoric acid, hydrogen peroxide solution and ultrapure water is used as the cleaning solution is described. As described above, in addition to these, a mixed solution of hydrochloric acid, hydrogen peroxide and ultrapure water, or a cleaning solution of hydrofluoric acid diluted with ultrapure water can be used.

In the present embodiment, the p-type well layer 1
Forming source and drain regions in MOS 2
Although the FET has been described, a MOSFET that forms an n-type well layer instead of the p-type well layer 12 may be used.

In this embodiment, the MOSFET has been described. However, in the case of a semiconductor device requiring low-resistance electrodes and wirings, the structure of these electrodes and wirings should be the gate electrode 19. Thereby, a low-resistance electrode or wiring can be realized. At this time, as in the present embodiment, W
By using the tungsten nitride film 16a comprising ₂ N crystals, since the risk of a tungsten nitride film 16a is etched by the cleaning step is eliminated, it is possible to manufacture without being limited to the cleaning process,
A highly reliable semiconductor device having stable element characteristics can be manufactured.

[0028]

As described above, according to the present invention, it is possible to provide a method of manufacturing a semiconductor device using tungsten nitride, which can perform cleaning after forming a tungsten nitride film.

[Brief description of the drawings]

1 (a) to 1 (c) show a conventional general method,
MO having a three-layered gate electrode of tungsten film 17, tungsten nitride film 16, and polycrystalline silicon 16
FIG. 4 is a cross-sectional view showing a procedure for forming an SFET.

2 (a) to 2 (d), a MOSFET having a three-layered gate electrode of a tungsten film 17, a tungsten nitride film 16 and a polycrystalline silicon 16 is formed by a manufacturing method according to an embodiment of the present invention. Sectional drawing which shows a procedure.

3 (e), (f) A MOSFET having a three-layered gate electrode of a tungsten film 17, a tungsten nitride film 16, and polycrystalline silicon 16 is formed by the manufacturing method according to the embodiment of the present invention. Sectional drawing which shows a procedure.

[Explanation of symbols]

11 silicon substrate, 12 p-type well layer, 13 field oxide film, 14 gate oxide film, 15 polycrystalline silicon film, 16 amorphous tungsten nitride film,
16a: crystallized tungsten nitride film, 17: tungsten film, 18: silicon nitride film, 19: gate electrode,
20 ... n ⁺ type source region, 21 ... p ⁺ type drain region, 2
2 ... silicon nitride film, 23 ... insulating film, 24 ... source electrode, 25 ... drain electrode.

Claims (7)

[Claims] A film forming step of forming a plurality of conductive films including a tungsten nitride film on a semiconductor substrate; a processing step of patterning the conductive film into a desired shape; and cleaning the processed conductive film. After the step of forming the tungsten nitride film in the film forming step, and before the cleaning step, the tungsten nitride film is crystallized to crystallize the tungsten nitride film. A method for manufacturing a semiconductor device, comprising performing a heat treatment step. 2. The method of manufacturing a semiconductor device according to claim 1, wherein said heat treatment is performed at a temperature at which a W ₂ N crystal is formed in said tungsten nitride film. . 3. The method of manufacturing a semiconductor device according to claim 1, wherein the heat treatment step is performed at a temperature of 500 to 1000 ° C. 4. The method of manufacturing a semiconductor device according to claim 1, wherein said heat treatment step also serves as a step of forming another film on said conductor film. Production method. 5. The method of manufacturing a semiconductor device according to claim 1, wherein said semiconductor device is a field effect transistor, and said film forming step includes: forming a polycrystalline silicon film, said tungsten nitride film, A method of manufacturing a semiconductor device, comprising: stacking three layers of a tungsten film; and the processing step is a step of processing the conductor film into a shape of a gate electrode. 6. A semiconductor substrate comprising: a semiconductor substrate; and a conductor film formed in a desired pattern on the semiconductor substrate, wherein the conductor film has a multilayer structure including a tungsten nitride film. Crystallized,
A semiconductor device comprising a W ₂ N crystal. 7. A conductive film comprising a polycrystalline silicon film, a tungsten nitride film, and a tungsten film laminated on a substrate as a gate electrode, wherein the tungsten nitride film is crystallized;
A field effect transistor comprising a W ₂ N crystal.