JPH07263674A - Field effect semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To provide a field effect semiconductor device wherein P, B, As, etc., with which an amorphous or polycrystalline silicon layer of polycide structure as a gate electrode is doped are prevented from diffusing outward an account of the heat in the post-process, and the gate electrode can be prevented from turning to the state of depletion. CONSTITUTION:A gate electrode has the polycide structure composed of an amorphous or polycrystalline silicon layer 5 and a tungsten silicide layer 6 formed, via a gate insulating film 4, on a source region 2 and a drain region 3 formed on an Si substrate 1. As to at least the surface layer 7 of the tungsten silicide layer 6, the Si composition (x) of tungsten silicide WSix is set lower than or equal to 2.4. The Si composition (x) is gradually decreased from about 2.55 in the part in contact with the amorphous or polycrystalline silicon layer 5 to 2.4 in the uppermost layer. Thereby the separation of a gate electrode can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field effect semiconductor device and a manufacturing method thereof, and more particularly to a field effect semiconductor device having a gate electrode having a polycide structure and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, along with the demand for higher speed, it has been required to miniaturize the gate electrode of a field effect semiconductor device to the submicron order and to reduce the resistance. The gate electrode has a single layer structure of polysilicon. Instead of the above, the polycide structure is formed by two layers of a polysilicon layer and a tungsten silicide layer.

FIG. 3 is an explanatory view of a conventional field effect semiconductor device having a gate electrode having a polycide structure.
(A) shows the structure at the time of ion implantation, and (B) shows the structure at the time of forming SiO ₂ HTO. In this figure, 21 is a silicon substrate, 22 is a source region, 23 is a drain region, 24 is a gate insulating film, 25 is an amorphous silicon layer, 26 is a tungsten silicide layer, 27 is a SiO ₂ HTO sidewall, 28 is a SiO ₂ HTO. It is a protective film.

In the case of manufacturing a field effect semiconductor device having a conventional polycide structure gate electrode, as shown in FIG. 3A, the surface of the silicon substrate 21 is thermally oxidized to form a gate insulating film 24. and, forming an amorphous silicon layer 25 for improving the strength peeling thereon, after forming a tungsten silicide (WSi _X) layer 26 thereon, the gate insulating film 24 and the amorphous silicon layer 2
5 and the tungsten silicide layer 26 are patterned to leave them in a region for forming a gate, and P ⁺ ions are implanted by using this laminated structure as a mask to form a source region 22 and a drain region 23, Impurities are introduced into the amorphous silicon layer 25 to give it conductivity. Si tungsten silicide (WSi _X) layer 26 in this case
The composition x is about 2.55.

Next, the entire surface including the laminated structure thereon
And stoichiometric SiO₂To improve dielectric strength
Therefore, SiO at a high temperature of about 750 to 800 ° C.₂HTO
(High Temperature Oxide) film
And anisotropically etched by RIE to form SiO.
₂HTO sidewall 27 is formed and SiO is formed on it.
₂The HTO protective film 28 is formed.

[0006]

However, as described above, the conventional gate electrode having a polycide structure has a thickness of 750 to 80.
When the SiO ₂ HTO film is formed by CVD at a high temperature of about 0 ° C., P ^+, which has been ion-implanted at a high concentration to give conductivity to the amorphous silicon layer 25, is outwardly diffused to leave only 5% of the initial amount. However, since the resistance of the amorphous silicon layer 25 becomes high, the portion having the high resistance is depleted, which causes a problem that the controllability of the drain current by the signal applied to the gate electrode is deteriorated.

In this conventional field effect semiconductor device
The tungsten silicide layer 26 at a pressure of 200 mTo
rr, SiH_FourFlow rate of 1000 cc / min
And WF ₆Flow rate of 8 cc / m and film formation temperature of 350
℃ and deposit, P⁺Is 20 keV and the dose is 4
× 10¹⁵cm^-2And Of P measured by X-ray fluorescence
From the strength, impurities in the amorphous silicon layer 25
The remaining amount of (P) was determined, but HTO was deposited at 775 ° C.
In this case, the remaining amount of impurities (P) was about 35%. Na
The impurity implanted into the amorphous silicon layer 25 is B
⁺, As⁺In case of etc., the same phenomenon as above occurs
It

The present invention is an electric field effect which can prevent P, B, As, etc., which are doped in an amorphous or polycrystalline silicon layer having a polycide structure, which is a gate electrode, from out-diffusing by heat in a subsequent process. An object of the present invention is to provide a semiconductor device.

[0009]

In a field effect semiconductor device according to the present invention, an amorphous or polycrystalline silicon layer and tungsten are used to prevent outward diffusion of a doped species in the amorphous or polycrystalline silicon layer. In the gate electrode having a polycide structure composed of a silicide layer, at least the surface of the tungsten silicide layer is
2 composition x of Si tungsten silicide WSi _X.
A structure formed of 4 or less tungsten silicide was adopted.

In this case, the tungsten silicide layer formed on the amorphous or polycrystalline silicon layer is replaced by
From the side in contact with the amorphous or polycrystalline silicon layer to the surface, the tungsten silicide WSi _x S
The composition x of i can be continuously changed from about 2.55 to 2.4 or less.

Further, in the method of manufacturing a field effect semiconductor device according to the present invention, an amorphous or polycrystalline silicon layer and a tungsten silicide layer are formed in order to prevent outward diffusion of the doped species in the polysilicon layer. forming the gate electrode of the polycide structure, at least the surface of the tungsten silicide layer is adopted depositing such a composition x of Si tungsten silicide WSi _X is 2.4 or less.

In this case, the amount of the tungsten silicide layer is small.
When depositing the surface without SiH _Four/ WF₆Flow ratio
It can be less than 83 and also tungsten tungsten
When depositing at least the surface of the id layer, the deposition temperature is set to 25
The temperature can be set to 0 ° C or higher and 380 ° C or lower.

[0013]

In a gate electrode having a polycide structure composed of an amorphous or polycrystalline silicon layer and a tungsten silicide layer as in the field effect semiconductor device of the present invention, at least the surface of the tungsten silicide layer is made of tungsten silicide WSi _x Si. Is formed of tungsten silicide having a composition x of 2.4 or less, then SiO ₂ is formed at a high temperature of about 750 to 800 ° C.
Even if the HTO film is formed by CVD, it is possible to prevent impurities such as P ^+, which have been ion-implanted at a high concentration in order to make the amorphous silicon layer have conductivity, from being lost by outward diffusion.

In this case, the tungsten silicide layer formed on the amorphous or polycrystalline silicon layer is
From the side in contact with the amorphous or polycrystalline silicon layer to the surface, the tungsten silicide WSi _x S
When the composition x of i is continuously changed from about 2.55 to 2.4 or less, peeling of the tungsten silicide layer can be further reduced.

FIG. 4 is a diagram for explaining the effect of reducing the outward diffusion of impurities according to the present invention. FIG. 4A shows the relationship between the composition of tungsten silicide and the transmittance of impurities, and FIG. The relationship of the amount of impurities (P) is shown.

The horizontal axis in FIG. 4 (A) shows the composition x of Si tungsten silicide WSi _X, the vertical axis represents the impurity (P)
Shows the transmittance, ie, the ease of removal (100%).
According to this figure, S of tungsten silicide WSi _x
When the composition x of i = x = 2.4, impurities (P) are generated in the growth of HTO at 750 ° C. and the growth of HTO at 775 ° C.
It can be seen that the transmittance is low. On the other hand, x = 2.
It can be seen that at 55 or more, in the growth of HTO at a temperature higher than 750 ° C., the transmittance of the impurity (P) is high and almost all of the impurities (P) are eliminated.

The horizontal axis of FIG. 4B shows the relationship between the time (depth) for removing the polycide structure by sputtering and the amount of residual impurities (P) by SIMS analysis. According to this figure, in the case of tungsten silicide WSi _X of Si composition x of x = 2.4, much amount of residual impurities (P), x = 2.55, in the case of x = 2.8, the It can be seen that the amount of residual impurities (P) is drastically reduced.

FIG. 5 is a diagram for explaining the relationship between the SiH ₄ / WF ₆ flow rate ratio and the Si composition ratio of tungsten silicide. In the experiment shown in this figure, the deposition temperature was 360 ° C., the pressure was 200 mTorr, and the flow rate of SiH ₄ was 1000 c.
It was carried out with a fixed c / min. In this figure, the horizontal axis shows the flow rate of WF ₆ when the flow rate of SiH ₄ when depositing a tungsten silicide film by CVD is 1000 cc / min, and the vertical axis shows the Si of the deposited tungsten silicide WSi _x at that flow rate. Composition ratio x
Is shown.

[0019] As shown in this figure, the flow rate of WF ₆ is increased, i.e., as the SiH ₄ / WF ₆ flow rate ratio is decreased, the composition x of Si tungsten silicide WSi _X is decreased. To the composition x of Si tungsten silicide WSi _X as in the present invention to 2.4 or less, the flow rate of the WF ₆ 12 cc / min or less, i.e.,
It is necessary to set the SiH ₄ / WF ₆ flow rate ratio to 83 or less.

In the above experiment, the temperature for depositing the tungsten silicide layer was set to 350 ° C. and 360 °.
Although an example in which the temperature is set to ℃ is shown, this temperature is set to 250 ℃ or higher, 38
It can be in the range of 0 ° C. or less. The temperature for depositing the tungsten silicide layer is 250 ° C. or higher, 380
When the temperature is lower than ℃, the bulk resistance of the tungsten silicide WSi _x before annealing becomes 1000 μΩ · cm or lower, which is smaller than the bulk resistance of polysilicon doped with impurities, so that the technical effect of lowering the resistance of the polycide layer occurs. .

When the temperature for depositing the tungsten silicide layer is set to 250 ° C. or higher and 380 ° C. or lower,
The ratio of Si in WSi _x is reduced, the Si—F bond is reduced, and out-diffusion of the doped species can be effectively prevented. If SiH ₄ / WF _{6 is set} to 83 or less, WSi
The ratio of Si in _X can be reduced, resulting in S
The i-F bond is reduced, and out-diffusion of the doped species can be effectively prevented.

[0022]

EXAMPLES Examples of the present invention will be described below. (First Embodiment) FIG. 1 is a structural explanatory view of a field effect semiconductor device having a gate electrode having a polycide structure of the first embodiment. In this figure, 1 is a silicon substrate, 2 is a source region, 3 is a drain region, 4 is a gate insulating film, 5 is an amorphous silicon layer, 6 is a first tungsten silicide layer, and 7 is a second tungsten silicide layer. .

In the field effect semiconductor device having the gate electrode of the polycide structure of this embodiment, the surface of the silicon substrate 1 is thermally oxidized to form the gate insulating film 4, and peeling strength is improved on the gate insulating film 4. Of amorphous silicon layer 5 is formed, and tungsten silicide WSi is formed on the amorphous silicon layer 5.
First tungsten silicide layer 6 in which x of _X is 2.55
Form, and after x of tungsten silicide WSi _X thereon to form a second tungsten silicide layer 7 of 2.4 or less, the gate insulating film 4 and the amorphous silicon layer 5 and the first tungsten silicide layer 6 a Patterning the stacked structure of the tungsten silicide layer 7 of No. 2 and leaving it in the region for forming the gate, and ion implantation of P ⁺ using this stacked structure as a mask to form the source region 2 and the drain region 3; There is.

In this embodiment, the pressure of the first tungsten silicide layer 6 is set to 200 mTorr, the flow rate of SiH ₄ is set to 1000 cc / min, and the flow rate of WF ₆ is set to 8 cc.
/ M, and the second tungsten silicide layer 7 is deposited.
To 150 mTorr and the flow rate of SiH ₄ to 100
The deposition rate was 0 cc / min and the flow rate of WF ₆ was 10 cc / m.

In the field effect semiconductor device of this embodiment, the uppermost second tungsten silicide layer 7 effectively diffuses the impurities (P) introduced into the underlying amorphous silicon layer 5 outwardly. Can be prevented.

(Second Embodiment) FIG. 2 is a structural explanatory view of a field effect semiconductor device having a gate electrode having a polycide structure of the second embodiment. In this figure, 11 is a silicon substrate, 12 is a source region, 13 is a drain region, 14 is a gate insulating film, 15 is an amorphous silicon layer, and 16 is a tungsten silicide layer.

Gate electrode of polycide structure of this embodiment
In a field effect semiconductor device having a
Gate insulating film with a thickness of 120Å by thermally oxidizing the surface of plate 11
14 to form the thickness for improving peel strength
Form a 400 Å amorphous silicon layer 15 and
600 Å thick tungsten silicide WSi on top of _X
Form a tungsten silicide layer 16 with x of 2.4 or less
After the formation, the gate insulating film 14 and the amorphous silicon layer
15 and a tungsten silicide layer 16 are stacked.
This product is then turned and left in the area forming the gate.
P using the layer structure as a mask⁺Ion implant the source
A region 12 and a drain region 13 are formed.

Further, in this embodiment, the pressure of the tungsten silicide layer 16 is set to 150 mTorr, the flow rate of SiH ₄ is set to 1000 cc / min, and the flow rate of WF ₆ is set to 10.
to cc / m, the film formation temperature is deposited in the 350 ° C., P ⁺
Was 20 keV and the dose was 4 × 10 ¹⁵ cm ⁻² .

In the field effect semiconductor device of this embodiment, the tungsten silicide layer 16 can effectively prevent the outward diffusion of the impurity (P) introduced into the underlying amorphous silicon layer 15. The remaining amount of impurities (P) in the amorphous silicon layer 15 was calculated from the intensity of P measured by fluorescent X-ray.
When the film was formed at 75 ° C., the residual amount of impurities (P) was about 83%. This is 35 when the conventional x is 2.55.
%, It can be seen that the effect of preventing the outward diffusion of the impurity (P) introduced into the amorphous silicon layer 15 is remarkable.

In the field effect semiconductor device of the first embodiment described above, one tungsten silicide layer having x of 2.4 or less is used, and x is 2.55 and x is 2.4 or less. Although the case where the two tungsten silicide layers are used has been described, it is also possible to use tungsten silicide in which x continuously changes from 2.55 to 2.4 or less, and in this case, the tungsten silicide layer is more difficult to peel off. Become.

[0031]

As described above, according to the present invention,
Impurities such as P, B, As introduced into the lower amorphous or polycrystalline silicon layer forming the gate electrode of the polycide structure are diffused out by the heat treatment of the subsequent step without increasing the number of steps. Difficult, and as a result, the effect that the depletion of the gate is hard to occur, the next generation,
It greatly contributes to the speedup of next-generation VLSI.

[Brief description of drawings]

FIG. 1 is a configuration explanatory view of a field effect semiconductor device including a gate electrode having a polycide structure of a first embodiment.

FIG. 2 is a structural explanatory view of a field effect semiconductor device including a gate electrode having a polycide structure of a second embodiment.

3A and 3B are explanatory views of a field effect semiconductor device including a conventional gate electrode having a polycide structure, in which FIG. 3A shows a structure at the time of ion implantation and FIG. 3B shows a structure at the time of forming SiO ₂ HTO.

4A and 4B are explanatory diagrams of the effect of reducing the outward diffusion of impurities according to the present invention. FIG. 4A shows the relationship between the composition of tungsten silicide and the transmittance of impurities, and FIG. 4B shows the depth of the polycide structure and residual impurities (P). ) Shows the relationship of the amount.

FIG. 5 is an explanatory diagram of a relationship between a SiH ₄ / WF ₆ flow rate ratio and a Si composition ratio of tungsten silicide.

[Explanation of symbols]

1 silicon substrate 2 source region 3 drain region 4 gate insulating film 5 amorphous silicon layer 6 first tungsten silicide layer 7 second tungsten silicide layer 11 silicon substrate 12 source region 13 drain region 14 gate insulating film 15 amorphous silicon layer 16 tungsten Silicide layer 21 Silicon substrate 22 Source region 23 Drain region 24 Gate insulating film 25 Amorphous silicon layer 26 Tungsten silicide layer 27 SiO ₂ HTO sidewall 28 SiO ₂ HTO protective film

Claims (5)

[Claims] 1. In a gate electrode having a polycide structure composed of an amorphous or polycrystalline silicon layer and a tungsten silicide layer, at least the surface of the tungsten silicide layer has an S content of tungsten silicide WSi _x .
A field-effect-type semiconductor device, which is formed of tungsten silicide having a composition x of i of 2.4 or less. Wherein amorphous or polycrystalline tungsten silicide layer formed on the silicon layer of, toward the surface from the side in contact with the silicon layer of amorphous or polycrystalline, the composition x of Si tungsten silicide WSi _X 2.55 The field effect semiconductor device according to claim 1, wherein the field effect semiconductor device continuously changes from about 2.4 to less than 2.4. 3. When forming a gate electrode having a polycide structure composed of an amorphous or polycrystalline silicon layer and a tungsten silicide layer, at least the surface of the tungsten silicide layer is formed of tungsten silicide WSi _x.
2. The method for manufacturing a field effect semiconductor device, comprising depositing Si so that the composition x of Si is 2.4 or less. 4. The method for manufacturing a field effect semiconductor device according to claim 3, wherein the SiH ₄ / WF ₆ flow rate ratio is set to 83 or less when depositing at least the surface of the tungsten silicide layer. 5. The deposition temperature is 250 ° C. or higher and 380 ° C. when depositing at least the surface of the tungsten silicide layer.
The method for manufacturing a field effect semiconductor device according to claim 3, wherein: