JP2538664B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor device in which a gate electrode is formed of a tungsten film, and particularly, a high temperature heat treatment applied when manufacturing the semiconductor device. The present invention relates to a method for manufacturing a semiconductor device that can reduce the characteristic deterioration of the semiconductor device due to a tungsten film.

(Prior Art) As a semiconductor device having a gate electrode, for example, a MOS (Metal Oxide) known as an important device for constructing an LSI such as a semiconductor memory or a microprocessor is known.
Semiconductor) type FET (Field Effect Transistor).

Polycrystalline silicon (hereinafter referred to as polysilicon) is generally used as the gate electrode material of such a MOS FET. The reason is that polysilicon has good etchability, good oxidation characteristics, chemical stability, and excellent step coverage (the property of covering the underlayer with a uniform film thickness regardless of the underlying step). It was from.

However, as the integration and speed of LSIs have increased, the increase in signal delay time due to the resistance of the wiring including the gate electrode has become a problem. Therefore, recently, instead of polysilicon, an alloy (silicide) of a refractory metal and silicon and polysilicon are used as the gate electrode material, and the structure of the gate electrode is a two-layer structure of silicide / polysilicon. . However, in the future, as the integration density of LSIs further increases, this configuration will not be able to meet the requirements.
A gate electrode material having lower resistance is required.

Tungsten can be considered as a gate electrode material satisfying such requirements. FIGS. 5A to 5C show the structure of a conventional MOS FET using tungsten for the gate electrode,
It is a figure for explaining this forming method of a gate electrode, and is a process drawing roughly shown by a sectional view paying attention to a gate electrode forming process.

First, a field oxide film 13 for element isolation is formed on a silicon substrate 11 by a known method, and then a film thickness of, for example, 150 is formed on the silicon substrate 11 by, for example, a thermal oxidation method.
Å Silicon oxide film 15 for gate insulating film (hereinafter referred to as gate silicon oxide film 15). Are formed (fifth
(A).

Next, in order to obtain a gate electrode composed of a tungsten film on the gate silicon oxide film 15 by a suitable method such as a sputtering method, a CVD method or an EB (electron beam) vapor deposition method, the film thickness is, for example, about 3000 Å The tungsten (W) material film 17 is formed (FIG. 5 (B)).

Next, a resist pattern (not shown) serving as a mask for patterning the gate electrode is formed on the tungsten material film 17, and an unnecessary portion of the tungsten material film 17 is etched using the resist pattern as a mask. A gate electrode 17a is formed by using (FIG. 5 (C)). After that, a source region, a drain region and the like are formed to form a MOS type FET. However, description of the procedure for forming the source region and the like is omitted here.

Here, in the case where a tungsten material film is formed by the sputtering method, a document (IEEE TRANSACTIONS on Electron Devices (IEEE TRANSACTION)
S ON ELECTRON DEVICES) ED-34 (3) (1987.3) pp.60
7-613), the internal stress of the deposited tungsten material film changes depending on the Ar (argon) gas pressure during sputtering. FIG. 6 is a diagram showing such a state, a diagram cited from the above-mentioned document, and a characteristic curve diagram showing the argon gas pressure dependency of the internal stress of the tungsten material film.

Further, according to the above-mentioned document, when the gate electrode of the MOS-type FET is composed of a tungsten film, the magnitude of the internal stress of this tungsten film is related to the formation of the interface order, and it is possible to reduce g _m due to hot carriers. It is said to be related.

Therefore, in order to avoid this, in the above-mentioned literature, MOS
After forming a tungsten material film (the state shown in FIG. 5B) in manufacturing a type FET, the tungsten material film is heat-treated at a temperature of 900 to 1100 ° C. (hereinafter, also referred to as annealing). A method of doing is proposed. It has been shown that this annealing reduces the internal stress of the tungsten material film to a tensile stress of about 4 × 10 ⁹ dyne / cm ² . In addition, a MOS type FET that patterned the annealed tungsten material film and used it as a gate electrode
Then, it is said that the deterioration of g _m does not occur.

Further, according to this document, the tungsten material film has an internal stress of 1.5 × 10 ¹⁰ dyn after the film formation and before annealing.
It is said that a material exhibiting a compressive stress of about e / cm ² is acceptable.
The reason is that in order to form a low-stress tungsten material film from the beginning, a relatively high argon gas pressure must be used, and a tungsten material film formed under such conditions contains a large amount of oxygen. Therefore, there is a drawback that the etching shape is deteriorated, and this is to avoid this. Even if the internal stress after forming the tungsten material film is high (the compressive stress is high), there is no problem because the internal stress can be reduced by annealing according to the method of the above document.

(Problems to be Solved by the Invention) However, according to a detailed experiment (which will be described later) of the inventor of the present application, a tungsten material film formed by a sputtering method is formed after film formation and before heat treatment (as- depo
(In some cases) In the case of a tungsten material film having a high compressive stress, patterning this to form a MOS electrode capacitor and heat treating this capacitor at a temperature of about 1000 ° C. will result in a fixed charge density and an interface state density. However, there is a problem in that it increases rapidly, that is, the MOS characteristics deteriorate.

FIG. 7 and FIG. 8 are characteristic curve diagrams showing the above experimental results, FIG. 7 shows fixed charge density, and FIG. 8 shows interface state density. In both figures, the data marked with ▽ are for the heat treatment temperature of 1000 ° C, and the data marked with × are for the heat treatment temperature of 900 ° C. In both figures, when the tungsten material film for obtaining one electrode (corresponding to the gate electrode) of the MOS type capacitor is formed by the sputtering method, the RF power is kept constant and the Argan gas pressure is set to 5, 12, By changing to 20 mmTorr, the internal stress of the tungsten material film after film formation and before annealing was −3.2 × 10 ⁹ dyne / cm ² , −10.5 × 10 ⁹ dyne / cm ² , −1, respectively.
A tungsten material film of 4.3 × 10 ⁹ dyne / cm ² (both of which is compressive stress) is formed, and a MOS type capacitor is formed using these films. After the heat treatment for 1 minute, the fixed charge density and the interface state density of each were measured, and the data obtained by this measurement was arranged and obtained.

MOS composed of tungsten film with high compressive stress
If the MOS characteristics of the structure deteriorate as described above,
In a semiconductor device having a gate electrode formed of such a tungsten film, for example, a MOS type FET, the MOS characteristics are likely to deteriorate (change) due to various annealing during the manufacturing process. It is very problematic in manufacturing FET.

Here, in order to solve such a problem, it may be possible to increase the argon gas pressure during sputtering to form a tungsten material film having a small internal stress, as described in the section of the prior art. However, as described above, the tungsten material film formed under such conditions contains a large amount of oxygen, which causes a problem that the etching shape deteriorates.

The present invention has been made in view of such points,
Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a method of manufacturing a semiconductor device capable of reducing the deterioration of the characteristics of the semiconductor device due to the tungsten film forming the gate electrode.

(Means for Solving the Problem) In order to achieve this object, the inventor of the present application has conducted extensive research. As a result, a MOS structure capacitor having a gate electrode of a tungsten film formed by a CVD method using WF ₆ and H ₂ as a source gas or a CVD method using WF ₆ and SiH ₄ as a source gas has a fixed charge density, It was found that the interface state density also shows a low value that can be practically used. Among these facts, regarding the CVD method using WF ₆ and H ₂ as raw material gases, the reference a (Japane
se Journal of Applied Physics, Vol.27, N
o.11, Nov, 1988.L2161-L2163), especially in Fig. 4 and Table 1.

From these facts, the tungsten material film for forming the gate electrode is formed on the wafer (actually, by the CVD method using WF ₆ and H ₂ as the source gas or the CVD method using WF ₆ and SiH ₄ as the source gas. It is considered that the tungsten film (hereinafter, also referred to as a CVD tungsten film) may be formed on a silicon oxide film and patterned into the shape of the gate electrode. However, it was also found in the detailed study of the inventor of the present application that there are the following points to be improved merely by such a method. In other words, since this CVD tungsten film is likely to have weak adhesion with the silicon oxide film, it may be peeled off during the subsequent manufacturing process. Will also be needed.

Therefore, an attempt was made to first form a tungsten film on a wafer by a sputtering method and then form a tungsten film on the wafer by the CVD method. A tungsten film formed by the sputtering method (hereinafter also referred to as a sputtered tungsten film) is considered to have practical adhesion to a silicon oxide film, and a CVD tungsten film is formed on this sputtered tungsten film. In that case, it is considered that the two are tungsten and therefore exhibit practical adhesion. However, at that time, the stress during as-depo of the sputtered tungsten film (after film formation and before heat treatment)
It was also found from the research by the inventor of this application that it is necessary to consider the stress at the time of as-depo of the two-layer film composed of the sputtered tungsten film and the CVD tungsten film. That is, for example, in the latter half of the right column of L2161 and Fig. 1 of the above-mentioned document a relating to the inventor of this application, WF ₆ and H ₂
The internal stress at the time of as-depo of the CVD tungsten film formed by the CVD method using and as the source gas shows tensile stress in most cases under practical film forming conditions (maximum 5 × 10 ⁹ dyne /
It shows that the tensile stress is about cm ² ). From this, the sputtered tungsten film and
The internal stress at the time of as-depo of the two-layer film composed of the CVD tungsten film is larger than the internal stress at the time of as-depo of this CVD tungsten film alone, that is, the tensile stress becomes larger. It can be said that it is not preferable. This is because, empirically, a large internal stress often causes various problems. In order to prevent this from happening, it is considered that the sputtered tungsten film used as the first layer should be formed under the film forming conditions such that it exhibits compressive stress. Since the internal stresses of the sputtered tungsten film and the CVD tungsten film are in the opposite directions, the tensile stress shown by the CVD tungsten film will not be increased more than now. However, even if the sputtered tungsten film is formed so as to exhibit a compressive stress, if the internal stress at the time of as-depo of the two-layer film shows an excessive compressive stress, the fixed charge density and the interface state are still required. The density increases, which causes a problem. From the experimental results described later, it is preferable that the compressive stress of the two-layer film during as-depo be 5 × 10 ⁹ dyne / cm ² or less. Therefore, it can be said that it is necessary to control the internal stress of the sputtered tungsten film and the two-layer film during as-depo. It was also found that the internal stress of the two-layer film can be controlled by changing the film thickness ratio between the sputtered tungsten film and the CVD tungsten film, as is clear from the experimental results described later.

Therefore, according to the present invention, in manufacturing a semiconductor device using a tungsten film for the gate electrode, after the first tungsten material film is formed on the lower surface, and after the manufacturing of the semiconductor device is performed. Forming the first tungsten material film by a sputtering method under film forming conditions such that the internal stress of the first tungsten material film before being subjected to the heat treatment in the step (at the time of as-depo) becomes a compressive stress; A second tungsten material film is formed on the upper surface by a CVD method using WF ₆ and H ₂ as source gases, or WF 6.
And a step of forming a gate electrode by patterning these first and second material films with a CVD method using ₆ and SiH ₄ as source gases, and the first and second materials At the time of film formation, the film thickness ratio of these material films is adjusted so that the internal stress at the time of as-depo of the two-layer film composed of these material films becomes tensile stress or compressive stress of 5 × 10 ⁹ dyne / cm ² or less. It is characterized by changing.

(Function) According to the method of manufacturing a semiconductor device of the present invention, the first tungsten material film formed by the sputtering method and the second tungsten material film formed by the CVD method using a predetermined source gas are used. A semiconductor device intermediate having a gate electrode composed of a two-layer film which is a layer film and has an internal stress at as-depo within a predetermined range can be obtained. This intermediate can secure the adhesion between the underlayer and the gate electrode, and can prevent the increase of the fixed charge density and the interface level density even when subjected to the high temperature heat treatment in the subsequent manufacturing process. Is.
Here, one of the roles of the first tungsten material film formed by the sputtering method is to prevent the second tungsten film (CVD tungsten film) from further increasing the tensile stress at the time of as-depo. Therefore, the first tungsten material film does not have to be formed so as to exhibit a strict compressive stress value although it is sufficient to exhibit a compressive stress at the time of as-depo. Therefore, the conditions for forming the first tungsten material film can be relaxed. Further, since the film stress of the two-layer film at the time of sa-depo is in a considerably wide range, it is easy to control the film thickness ratio of the first and second tungsten films. Therefore, this intermediate is easily obtained.

(Embodiment) An embodiment of a method for manufacturing a semiconductor device of the present invention will be described below with reference to the drawings.

In each of the examples, the MO film in which the two-layer film composed of the first and second tungsten films was used as one electrode (assuming a gate electrode)
Various S-structure capacitors were produced by changing the film thickness ratio of the first and second tungsten films, and these capacitors were heat-treated, and then the fixed charge density and the interface state density were measured, respectively, It shows the effect of the method of manufacturing a semiconductor device.

Preliminary Experiment Prior to the description of the embodiments of the present invention, a preliminary experiment as described below for explaining the present invention was conducted. FIG. 2 is a diagram used for the explanation. An element isolation region 23 is formed on a silicon substrate 21, a gate silicon oxide film 25 is further formed on the silicon substrate 21, and a first silicon oxide film 25 is formed on the gate silicon oxide film 25. The tungsten film formed by the sputtering method as the tungsten material film (hereinafter, also referred to as sputtered tungsten film) 27, the tungsten film formed by the CVD method as the second tungsten material film (hereinafter referred to as the CVD tungsten film) (Also abbreviated) 29
FIG. 4 is a cross-sectional view of a main part of a sample in which and are formed in this order.

Actually, a large number of silicon substrates having the gate silicon oxide film 25 formed are prepared, these silicon substrates are divided into four groups, and the film thickness is 500Å on the gate silicon oxide film of the first group of silicon substrates. Sputtered tungsten film 2
7 is formed, a sputtered tungsten film 27 with a film thickness of 1500 Å is formed on the gate silicon oxide film of the second group of silicon substrates, and a film thickness of 2500 Å is formed on the gate silicon oxide film of the third group of silicon substrates. The sputtered tungsten film 27 was formed, and the sputtered tungsten film 27 having a film thickness of 3000 Å was formed on the gate silicon oxide film on the silicon substrate of the fourth group. Then, on the sputtered tungsten film 27 on each of the silicon substrates of the first to third groups, the sum of the film 27 and the sputtered tungsten film 27 is 3000Å.
The CVD tungsten film 29 was formed so that

In this case, each sputtered tungsten film 27 has a thickness of 2.0% before the argon gas is introduced into the film forming chamber of the sputtering device.
After evacuating to × 10 ^-7 Torr, argon gas was introduced into this film formation chamber so that the argon gas pressure was 5 mmTorr, and R
The F power was formed under the condition of ² KW (RF power density was 4 W / cm ² ). Further, each of CVD tungsten film 29, the partial pressure of WF ₆ gas using the WF ₆ and H ₂ as the raw material gas was 4 Pa, H ₂
The partial pressure of the gas was 100 Pa, and the temperature of the substrate (silicon substrate with sputtered tungsten) was 400 ° C. The internal stress at the time of as-depo of the sputtered tungsten film and the CVD tungsten film formed under such conditions is 1.4 × 10 ¹⁰ dyn for the sputtered tungsten film.
e / cm ² (compressed), 0.5 for CVD tungsten film
It was found to be × 10 ¹⁰ dyne / cm ² (tensile). In addition,
The internal stress was measured by measuring the warp of the substrate after film formation with a flat nest tester and obtaining the result (the same applies hereinafter).
The internal stress of the two-layer film composed of the sputtered tungsten film 27 and the CVD tungsten film 29 was also obtained by the same method.

Next, the thickness of the sputtered tungsten film 27 in the two-layer film is plotted on the horizontal axis and the internal stress of the two-layer film is plotted on the vertical axis, and the relationship between the film pressure of the sputtered tungsten film 27 and the internal stress of the two-layer film is shown. The results are shown in FIG. As can be understood from FIG. 3, the internal stress of the two-layer film composed of the sputtered tungsten film and the CVD tungsten film can be arbitrarily controlled from compressive stress to tensile stress by changing the film thickness ratio of the two. I understood.

Description of Capacitor Manufacturing Procedure Next, a description will be given of a manufacturing procedure of a MOS type capacitor used in the description of the embodiment. Many MOS capacitors are built on a single silicon substrate. Figure 1 (A) ~ (E)
3A to 3D are manufacturing process diagrams used for the description, showing the state of the capacitor in the main process of the manufacturing process with a cross-sectional view focusing on two of a large number of MOS capacitors in the silicon substrate. It is a thing. However, these figures are only schematically shown to the extent that the present invention can be understood, and therefore the dimensions and shapes of the respective constituents and the dimensional ratios between the respective constituents are also schematic. It should be understood that the examples are not limiting.

First, in this example, 4 × n silicon substrates (n is a positive integer) were prepared. Then, a field oxide film 23 for element isolation is formed on each silicon substrate 21 by a known technique, and a silicon oxide film 25 (hereinafter referred to as a gate oxide film) as a gate insulating film having a film thickness of about 800 Å is formed by a thermal oxidation method. A silicon oxide film contact film 25) was formed (FIG. 1 (A)).

Next, a silicon substrate on which a gate silicon oxide film is formed so that the fixed charge density can be obtained.
21 is soaked in hydrofluoric acid, and gate silicon oxide films 25a, 25a of different thickness are formed on one silicon substrate.
b was formed (FIG. 1 (B)).

Next, the 4 × n silicon substrates are divided into four groups of n each. Then, on the gate silicon oxide films 25a and 25b of each silicon substrate of the first group, a film thickness of 500 Å is formed by the sputtering method.
The sputtered tungsten film 27 of was formed respectively. In addition, the gate silicon oxide film 25 of each silicon substrate of the second group
A sputtered tungsten film 27 having a film thickness of 1500Å was formed on each of a and 25b by a sputtering method. Further, on the gate silicon oxide films 25a, 25b of each silicon substrate of the third group,
A sputtered tungsten film 27 having a thickness of 2500 Å was formed by the sputter method. Further, a sputtered tungsten film 27 having a film thickness of 3000 Å was formed on each of the gate silicon oxide films 25a and 25b of the fourth group of silicon substrates by the sputtering method (FIG. 1 (C)). The sputtered tungsten film 27 was formed under the same conditions as the film forming conditions at the time of preparing the sample for the preliminary experiment described above.

Next, the CVD tungsten film 29 is formed on the sputtered tungsten film 27 of the silicon substrate for capacitor production of the first to third groups by the CVD method and under the same film forming conditions as in the preparation of the sample of the preliminary experiment described above. The total thickness of sputtered tungsten film and CVD tungsten film is 3000Å
Were formed so as to be as follows (FIG. 1 (D)). In addition, on the silicon substrate for capacitor fabrication of the fourth group, CV
D Tungsten film is not formed.

Next, on the CVD tungsten film 29 of each of the first to fourth groups of silicon substrates, in order to prevent the tungsten film from being oxidized during the high temperature heat treatment to be performed later, a low temperature (400 ° C.) normal pressure C
A silicon oxide film (not shown) having a film thickness of about 2000 Å is formed by the VD method, and then each of these samples is annealed at a temperature of 1000 ° C. in a N ₂ atmosphere for 30 minutes together. It was

Next, a resist pattern (not shown) for patterning the gate electrode was formed on the silicon oxide film (not shown) of each of these samples. Then, using this resist pattern as a mask, a silicon oxide film (not shown), CV
Unnecessary portions of the D tungsten film 29 and the sputtered tungsten film 27 were removed for each sample, and then the remaining silicon oxide film portion was removed by hydrofluoric acid. As a result, the first tungsten film 27a made of the remaining portion of the first tungsten material film 27 and the first tungsten film made of the remaining portion of the second tungsten material film 29.
A MOS capacitor 33 having a gate electrode 31 composed of a two-layer film with 29a was obtained (FIG. 3 (E)).

Measurement of Fixed Charge Density Next, the fixed charge density N _f was obtained by the procedure described below using each sample including the MOS type capacitor manufactured as described above.

For each sample, the film thickness of the gate silicon oxide film of the capacitors at a plurality of predetermined positions among the numerous MOS capacitors formed on each sample (the gate silicon oxide film of each capacitor is shown in FIG. ) Is different as shown by 25a and 25b.) T and the flat band voltage of the capacitor
V _FB was measured by a known method, and the fixed charge density N _f was obtained from the slope of a straight line (not shown) in which each value was plotted with V _{FB on} the vertical axis and t on the horizontal axis.

Measurement of interface state density In addition, using a capacitor with a gate silicon oxide film thickness of 200 Å of each sample including the MOS-type capacitor fabricated as described above, the known quasistatic CV method (Quas
i-Static by CV method), the interface state density D _it for each sample
Respectively asked.

Discussion Next, the first and second tungsten films 27a, 29 of each sample having the MOS type capacitor manufactured as described above are
The thickness of the sputtered tungsten film of the gate electrode 31 made of a is applied to the thickness of the tungsten film in the two-layer film shown in FIG.
The internal stress at as-depo was estimated by analogy. Then, this internal stress is applied to each sample by heat treatment (in this case, the above 1000 ° C.
Fixed charge density measured after heat treatment at the temperature
The influence on N _f and interface state density D _it was considered.

FIGS. 4 (A) and 4 (B) are diagrams used for this explanation, and FIG. 4 (A) shows the internal stress on the horizontal axis and the fixed charge density on the vertical axis. The plotted characteristic curve diagram, FIG. 4 (B), is a characteristic curve diagram in which the internal stress is plotted on the horizontal axis and the interface state density is plotted on the vertical axis, and these data are plotted. .

As can be understood from FIG. 4 (A), a MOS type capacitor having a gate electrode composed only of a sputtered tungsten film (where internal stress is 14.2 × 10 ⁹ dyne / cm ² in compressive stress in FIG. 4 (A)) In the case of the one), the fixed charge density becomes large. However, the internal stress of the two-layer film composed of sputtered tungsten film and CVD tungsten film is 5 × 10 ⁹ dyne / cm ²
Two-layer film showing the following compressive stress or 2 showing tensile stress
It has been found that the fixed charge density of the MOS type capacitor having the layer film as the gate electrode is a small value of N _f , which is equal to the fixed charge density of the capacitor when the gate electrode is made of polysilicon.

Further, as can be understood from FIG. 4B, the interface state density has the same tendency as the fixed charge density, and the internal stress of the two-layer film composed of the sputtered tungsten film and the CVD tungsten film is 5 × 10 5. ^In a MOS capacitor having a gate electrode of a two-layer film showing a compressive stress of ⁹ dyne / cm ² or less or a two-layer film showing a tensile stress, the interface state density D _it becomes a small value and the gate electrode is made of polysilicon. It has been found that the interface state density of the capacitor is the same as that of the structure.

From this result, the sputtered tungsten material film and the CVD tungsten material film, which have mutually opposite internal stresses and have relatively large internal stresses, respectively, and the internal stress of the two-layer film composed of these material films is the tensile stress. Or 5 × 10
^A semiconductor device having a gate electrode made of a tungsten film having a two-layer structure obtained by patterning this two-layer film is formed to have a film thickness ratio that provides a compressive stress of ⁹ dyne / cm ² or less.
Both the fixed charge density and the interface state density are small even after the heat treatment during the manufacture of this semiconductor device. Therefore, a semiconductor device having stable MOS characteristics can be obtained.

(Effects of the Invention) As is apparent from the above description, according to the method for manufacturing a semiconductor device of the present invention, the first tungsten material film formed by the sputtering method and the CVD method using a predetermined source gas are used. It is possible to easily obtain a semiconductor device intermediate body having a gate electrode composed of a two-layer film formed of the second tungsten material film and having an internal stress at as-depo within a predetermined range. . The first material film portion in this intermediate body contributes to the stress control of the two-layer film and also secures the adhesion between the gate electrode and the base. This intermediate body can reduce fluctuations in MOS characteristics such as an increase in fixed charge density and an interface state density even if high-temperature heat treatment is performed during manufacturing of the semiconductor device, so that a semiconductor device exhibiting desired MOS characteristics can be obtained. Can be provided.

[Brief description of drawings]

FIGS. 1 (A) to 1 (E) are diagrams for explaining the present invention, process drawings showing a manufacturing procedure of a MOS type capacitor, and FIG. 2 are diagrams for explaining the present invention. FIG. 3 is a cross-sectional view of an essential part of an experimental sample, and FIG. 3 is a diagram for explaining the present invention, showing the relationship between the sputtered tungsten film thickness in a two-layer film and the internal stress of the two-layer film during as-depo. 4A and 4B are diagrams for explaining the present invention, and FIGS. 5A to 5C are diagrams for explaining the conventional technique, in which a tungsten film is used as a gate electrode. 6 is a diagram showing the dependence of the internal stress of the sputtered tungsten film on the argon gas pressure, and FIG. 7 is a fixed charge density in the conventional structure. Fig. 8 shows the internal stress dependence of the variation due to the heat treatment at the time of as-depo. It is a figure which shows the internal stress dependence at the time of as-depo of the variation by the heat treatment of the interface state density in a structure. 21 ... Silicon substrate, 23 ... Field oxide film 25 ... Gate silicon oxide film 25a, 25b ... Gate silicon oxide film with different film thickness 27 ... First tungsten material film (sputtered tungsten film) 27a. First tungsten film 29 …… Second tungsten material film (CVD tungsten film) 29a …… First tungsten film 31 …… Gate electrode 33 …… MOS type capacitor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-60-149173 (JP, A) JP-A-53-71576 (JP, A) JP-A-60-126839 (JP, A) JP-A-62-1 217419 (JP, A) JP-A-2-228032 (JP, A) JP-A-63-84154 (JP, A) JP-B 6-1768 (JP, B2) Spring 1987 34th Applied Physics Association Lecture Lecture Proceedings 28p-N-8 JJAP, Vol. 27, No. 11, Nov, 1988, pp. L2161-L2163

Claims (1)

(57) [Claims] 1. When manufacturing a semiconductor device using a tungsten film for a gate electrode, a first tungsten material film is formed on a lower surface in a post-process after manufacturing the semiconductor device. A step of forming by a sputtering method under a film forming condition such that the internal stress of the first tungsten material film before being subjected to heat treatment (at the time of as-depo) becomes a compressive stress; The second tungsten material film is formed by the CVD method using WF ₆ and H ₂ as source gases, or WF ₆
And a step of forming a gate electrode by patterning these first and second material films with a CVD method using SiH ₄ and SiH ₄ as a source gas, and the first and second material films At the time of formation, the film thickness ratio of these material films is changed so that the internal stress at the time of as-depo of the two-layer film composed of these material films becomes tensile stress or compressive stress of 5 × 10 ⁹ dyne / cm ² or less. A method of manufacturing a semiconductor device, comprising: