JPH05343352A - Forming method for film of silicide - Google Patents

Abstract

PURPOSE:To form a film of silicide having no mixture of impurity in a boundary between a base layer and a silicide film and excellent adhesive properties with the base layer. CONSTITUTION:A polysilicon film 14 is formed on a gate oxide film 13, and a SWiX film 16 is deposited thereon through a seed layer such as a polysilicon thin film 15, etc. A natural oxide film on a surface of the film 14 is buried therein, a boundary with the film 16 becomes an ideal state, adhesive properties of the film 16 are improved, and a decrease in resistance of polyside is achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a silicide film used in a semiconductor device manufacturing process, for example, for forming a so-called polycide structure silicide film formed on polysilicon.

[0002]

2. Description of the Related Art LSI to be Solved
With the higher integration, the wiring resistance of the conventional polysilicon gate has reached a level that affects the operating speed of the transistor. In view of this, a so-called polycide structure was devised in which the wiring resistance of the gate is lowered by forming a double layer of polysilicon and a refractory metal silicide such as tungsten silicide (WSix).

Since a normal refractory metal silicide has a conductivity of about 10 times that of conventional polysilicon after the process, a gate having a polycide structure has an operating speed of a transistor having a fine gate to be highly integrated. It is advantageous to improve

The refractory metal silicide such as WSix has heretofore been deposited by the sputtering method, but in recent years, it has been deposited by the CVD method which is excellent in film characteristics in terms of mixing of impurities and step coverage. Deposition is becoming common.

FIG. 3 shows an example of a conventional method for forming a refractory silicide film on a silicon substrate. This method is performed, for example, as shown in FIG.
3B, a gate oxide film 3 is formed, a phosphorus-doped polysilicon film 4 is deposited on the gate oxide film 3 by a CVD method, and then a polysilicon film is formed. on film 4, as shown in FIG. 3 (C), and a tungsten silicide (WSi _X) 5 is deposited by a CVD method.

However, until now, the underlying polysilicon of the polycide structure and the refractory metal silicide, such as tungsten silicide, are deposited in different devices, so that the polysilicon is exposed to the atmosphere after the CVD and then the polysilicon is exposed. Even if a natural oxide film is formed on the surface and the dipping treatment with dilute hydrofluoric acid is performed, the natural oxide film is regrown by subsequent running water or exposure to the atmosphere. Depositing tungsten silicide on this causes the problems listed below due to the native oxide film grown on this polysilicon.

(1) The adhesion between the tungsten silicide and the underlying polysilicon is deteriorated. This is because although tungsten silicide is in close contact with polysilicon,
This is because it is difficult to adhere to O ₂ .

(2) After the heat treatment, the excess Si in the tungsten silicide is not sufficiently deposited due to the existence of the natural oxide film at the interface, and as a result, the crystal growth of WSi _x is suppressed, so that the heat treatment of the polycide gate is performed. Resistance does not fall sufficiently. At this time, tungsten silicide
CVD for the purpose of reducing stress and improving oxidizable characteristics
Immediately after that, the composition is controlled to have a Si-rich composition near X = 2.6.

(3) When the polycide gate is oxidized, tungsten is also oxidized because Si is not smoothly supplied from the underlying polysilicon, and WO ₃
Tungsten oxide such as is formed. Since this substance is volatile at a temperature of about 700 ° C., the polycide gate causes film breakage, film peeling and surface roughness during the oxidation as shown in FIG. 3 (D).

In addition, for example, in the case of depositing tungsten silicide by a dichlorosilane reduction process, this process is very sensitive depending on the surface condition of the underlying substrate and the type of the underlying substrate, and the formation density of initial WSi _x nuclei and Since the growth process changes, the reproducibility of tungsten silicide CVD becomes difficult to obtain due to the growth of the natural oxide film on the substrate surface. In particular, the time until the initial growth nuclei of tungsten silicide are sparsely formed by the growth of the natural oxide film and the deposition is started (delay time; Incub
cation time), the morphology of the film surface is deteriorated and the reproducibility between wafers is deteriorated.

In response to this fact, a method for effectively removing the natural oxide film on the surface of polysilicon has been considered. It is, for example, as follows.

(A) A native oxide film on the surface of polysilicon is removed by an in-situ dry pretreatment (usually plasma is applied to an etching gas).

(B) Using a chemical etch such as anhydrous HF in-situ to remove the native oxide film on the polysilicon surface.

(C) The underlying polysilicon and WSi _x are continuously formed without breaking the vacuum.

However, when the method (a) is used, ion damage due to plasma and etching used.
Depending on the gas (for example, when using a gas system such as CF ₄ or C ₂ F ₆ where the selection ratio between the underlying polysilicon and the natural oxide film is easy), impurities from etching gas such as C (carbon) are mixed. There is a fear of If impurities such as C remain, WSi _{X obtained} by reducing dichlorosilane has a low nucleus density during initial growth, so that crystals do not grow even after annealing and the resistivity increases.

Further, in the method (b), a material such as Monel alloy having resistance to corrosive gas such as anhydrous HF must be used in the gas path, and when water is mixed, Since the corrosiveness of HF remarkably increases, the inside of the apparatus must be completely dehydrated and the process gas must be highly purified, which is an expensive apparatus in practice.

Further, in the method (c), a hot wall type polysilicon CVD device and a cold wall type WSi _X having completely different concepts from each other are used.
The CVD tool must be combined with a cluster tool, which is also a very large, complicated and expensive device.

The present invention was devised in view of the above-mentioned conventional problems, and provides a method for forming a silicide film having good adhesion without the inclusion of impurities at the interface between the silicide and the underlying layer. It is what you get.

[0019]

The invention according to claim 1 is
In a method of forming a silicide film for depositing a silicide film on a semiconductor substrate, a solution is to deposit a thin seed layer made of polysilicon or amorphous silicon and then successively deposit a silicide film. ..

According to a second aspect of the present invention, after depositing a thin seed layer of polycrystalline germanium or amorphous germanium, a silicide film is subsequently deposited.
The solution is.

According to a third aspect of the present invention, after depositing a thin seed layer made of polysilicon, amorphous silicon, polycrystalline germanium, or amorphous germanium, a silicide film is continuously formed with dichlorosilane and hexafluorosilane. Forming by a CVD method using tungsten oxide as a reaction gas is a solution.

In a fourth aspect of the present invention, a seed layer made of polysilicon or amorphous silicon is deposited to a thickness of 50 nm or less, and then the seed layer is formed in the same reaction chamber by a CVD method using dichlorosilane and tungsten hexafluoride. The solution is to deposit the silicide film at approximately the same deposition temperature as the layer.

[0023]

According to the first and second aspects of the present invention, a seed layer made of very thin polysilicon is CVD-processed in the metal silicide CVD apparatus immediately before the metal silicide film CVD on the surface of the polysilicon having the natural oxide film. By continuously performing CVD on the metal silicide film, the natural oxide film is not formed at this time because the interface between the very thin seed layer and the metal silicide film is not polluted by atmospheric components. The contamination layer that originally existed on the surface of the underlying polysilicon, etc., is buried inside in a sandwich shape due to the deposition of this very thin seed layer, so the interface with the metal silicide has a natural oxide film. Not in an ideal state. At this time, the underlying layer has a seed layer / natural oxide film / polysilicon structure, but since the seed layer made of polysilicon or the like and SiO ₂ have originally good adhesion, no problem such as film peeling occurs.

Generally, a metal silicide CVD apparatus is of a cold wall type in general, and when a film of polysilicon or the like is formed in a reaction rate-determining region in this type of apparatus, a cold wall type CVD apparatus has a uniform wafer temperature. Since the property is not good, the film thickness distribution of the film such as polysilicon becomes poor. However, in the case of the present invention, since a very thin seed layer is additionally deposited on the existing polysilicon, there is no particular problem even if the film thickness distribution of the seed layer deposited later is somewhat poor. For example, a thin film (seed layer) deposited by adding 90 ± 2 nm (± 2.2% in-plane distribution) to the initially deposited polysilicon film is 10 ± 2 nm (± 3).
If the distribution is 0%), the final value is 100 ±
The film thickness distribution is 5 nm (± 5.0% in-plane distribution), which is acceptable.

In the third aspect of the present invention, a surface reaction rate-determining process such as WSi _x deposition of dichlorosilane reduction is performed. In this case as well, the surface state and type of the underlayer (polysilicon etc.) are kept constant. Since they can be aligned, a wafer with excellent in-plane uniformity and reproducibility can be obtained. Further, by increasing the initial nucleus density (seed density), silicide (WS) having excellent surface morphology is obtained.
i _X ) can be formed. Further, since the time until the deposition of the silicide is shortened, there is an effect that WSi _X excellent in controllability and reproducibility can be formed.

Further, according to the invention of claim 4, a film can be formed by using the same reaction chamber and changing the gas flow sequence at substantially the same temperature.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the method for forming a silicide film according to the present invention will be described below with reference to the embodiments shown in the drawings.

(Embodiment 1) This embodiment is an example in which the present invention is applied to a gate electrode in a MOS formation process.

First, as shown in FIG. 1 (A), after isolation of a portion to be an active region on a surface of a silicon substrate 11 (a LOCOS oxide film 12 is formed), a gate oxide film is formed on the active region. 13 is grown, and a polysilicon film 14 is further formed thereon (FIG. 1 (B)). Since the polysilicon film 14 is finally used as a conductor, it is necessary to sufficiently dope phosphorus (Phos) or the like. However, after the polysilicon film 14 is formed, it may be doped by an ion implantation method or a solid phase diffusion method. Alternatively, it may be doped in-situ during CVD. The CVD conditions for in-situ doping are, for example, as follows.

(Deposition conditions of in-situ doped polysilicon film) Temperature: 550 ° C. Pressure: 270 Pa (2 Torr) Gas and its flow rate SiH ₄ (100%) 400 _SCCM PH ₃ (0.5%) + SiH ₄ (99.5%) ... 100
_SCCM Next, after the natural oxide film on the polysilicon film 14 is once write-etched with a dilute hydrofluoric acid solution, it is very thin in, for example, a WSi _X CVD apparatus in a gas flow sequence as shown in FIG. Polysilicon thin film 15 as seed layer
And the WSi _X film 16 are continuously formed (see FIG. 1).
(C)).

Very thin polysilicon thin film 15 and WSi
The deposition conditions for the _X film 16 (WSi _x reduced in this case with dichlorosilane) are as follows, for example.

(Deposition conditions of the polysilicon thin film 15) Temperature: 580 ° C. Pressure: 13.3 Pa (100 mTorr) Gas and its flow rate SiH ₄ ... 100 _SCCM Film thickness: 10 nm (WSi _X film 16 deposition conditions) ○ Temperature… 580 ° C ○ Pressure… 40 Pa (300 mTorr) ○ Gas and its flow rate WF ₆ … 2.5 _SCCM SiH ₂ Cl ₂ … 150 _SCCM Ar… 100 _SCCM ○ Film thickness… 100 nm After that, the polycide is patterned and the whole gate is formed. A normal transistor forming process such as heat treatment in an oxidizing atmosphere is performed below. As a result, as shown in FIG. 1 (D), WSi _x film / film peeling and generation of WO ₃ did not occur,
A good polycide layer could be formed. Since the Si deposition from the WSi _x film 16 was sufficient, WSi _x crystal growth occurred, and the resistance of polycide could be sufficiently reduced.

Further, this embodiment has an advantage that the polysilicon thin film 15 (seed film) and the WSi _x film 16 can be continuously formed in the same reaction chamber at the same temperature.

(Embodiment 2) This embodiment is an example in which the present invention is applied when a continuous process is performed.

The process itself is the same as that of the first embodiment, but S is used for depositing the polysilicon thin film 15 as the seed layer.
When using i ₂ H ₆ , the polysilicon thin film 1 at this time
The deposition conditions of No. 5 are as follows, for example.

(Conditions for depositing polysilicon thin film) Temperature: 580 ° C. Pressure: 13.3 Pa (100 mTorr) Gas and its flow rate Si ₂ H ₆ 100 _SCCM He 100 _SCCM ○ Film thickness 10 nm This polysilicon thin film The steps before and after step 15 are the same as those in Example 1 above.

As described above, as the source gas of the polysilicon thin film 15, other high order silanes (Si _n H _{2n + 2} ) other than monosilane (SiH ₄ ) can be cited. In addition, at this time, phosphorus (Phos) is added to the polysilicon in-situ.
May be doped. At this time, phosphine (PH ₃ ) is used as the doping gas. In addition to polysilicon, amorphous Si, polycrystalline germanium, amorphous germanium, or the like may be used as the deposited film.

Further this embodiment shows a WSi _X dichlorosilane reduction may be any WSi _X of monosilane reduction as WSi _X. In this case, a thin polysilicon thin film 15
The deposition temperature may be slightly different between the WSi _X film 16 and the WSi _X film 16, but if the cold wall type CVD apparatus of the rapid heating and quenching type is used, the decrease in the through-put can be minimized.

Although the respective embodiments of the present invention have been described above, the present invention is not limited to these, but can be applied to other silicide film formation, and various design changes can be made.

[0040]

As is apparent from the above description, according to the method for forming a silicide film according to the present invention, the interface between the silicide and the polysilicon does not contain any impurities such as oxygen and carbon related to atmospheric components. There is an effect that a side gate can be manufactured. As a result, the following effects can be expected.

That is, since excess Si in the silicide is sufficiently precipitated after the heat treatment, it is possible to manufacture a polycide gate having a low resistance.

Further, since the number of effective bonds on the polysilicon is effectively increased, the adhesion between the silicide and the polysilicon is improved.

Furthermore, no abnormal oxidation of tungsten is observed even when oxidizing the polycide gate.
_The substance of ₃ is not formed, and there is an effect that the surface of the gate is not roughened.

Even in the case where a surface reaction rate-determining process such as WSi _x deposition of dichlorosilane reduction is performed, the surface state and type of the underlying polysilicon can be made uniform, so that the wafer has excellent in-plane uniformity and reproducibility. Is obtained. Further, by increasing the initial nucleus density, WSi _x having excellent surface morphology can be formed.

Further, since the delay time (time until the start of deposition) is shortened, there is an effect that WSi _X having excellent controllability and reproducibility can be formed.

Further, the very simple method of partially modifying the existing CVD apparatus such as WSi _X has the effect that it can be executed only by changing the gas flow sequence.

[Brief description of drawings]

FIG. 1A to FIG. 1D are cross-sectional views of essential parts showing steps of Examples 1 and 2 of the present invention.

FIG. 2 is an explanatory diagram showing a gas flow sequence of an example.

FIG. 3A to FIG. 3D are cross-sectional views of relevant parts showing the steps of the conventional technique.

[Explanation of symbols]

 11 ... Silicon substrate 14 ... Polysilicon film 15 ... Polysilicon thin film (seed layer) 16 ... WSi film (silicide film)

Claims (4)

[Claims] 1. A method of forming a silicide film on a semiconductor substrate, comprising depositing a thin seed layer of polysilicon or amorphous silicon and then successively depositing the silicide film. And a method of forming a silicide. 2. A method of forming a silicide film on a semiconductor substrate, comprising depositing a thin seed layer of polycrystalline germanium or amorphous germanium, and then depositing the silicide film. And a method of forming a silicide. 3. The method for forming a silicide according to claim 1, wherein the silicide film is formed by a CVD method using dichlorosilane and tungsten hexafluoride as reaction gases. 4. A method for forming a silicide film, comprising depositing a silicide film on a semiconductor substrate, wherein a seed layer made of polysilicon or amorphous silicon is deposited to a thickness of 50 nm or less, and then dichlorosilane and hexafluorosilane are placed in the same reaction chamber. CV using tungsten oxide
A method of forming a silicide, characterized in that the silicide film is deposited by the D method at a deposition temperature substantially the same as that of the seed layer.