JPH0150098B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a method in which metal silicide is formed in a semiconductor portion in order to lower the resistance of a semiconductor layer formed as a diffusion layer of a semiconductor substrate or an upper film on a semiconductor substrate. The present invention relates to a method of manufacturing a semiconductor device.

[Technical background of the invention]

In recent years, as semiconductor devices have become more highly integrated and their performance has become more sophisticated, higher speed devices are required, and it is becoming increasingly important to reduce the sheet resistance of diffusion layers and polysilicon (polycrystalline silicon) films formed on semiconductor substrates. It has become necessary.

In order to meet these demands, several methods have been proposed for forming silicide of a high melting point metal on a polysilicon film serving as a diffusion layer or an upper film.

An outline of the representative means is as follows. First, a field oxide film and a gate oxide film are formed on a semiconductor (silicon) substrate, a predetermined diffusion layer is formed in the substrate, and a polysilicon wiring is formed as a gate electrode on the gate oxide film. Subsequently, a titanium film is deposited on such a semiconductor substrate. After that, this semiconductor substrate is heated to 500℃~600℃.
When the heat treatment is performed at .degree. C., the titanium in the titanium film reacts with the silicon that is in contact with the bottom of the titanium film, and a titanium silicide layer is formed on the polysilicon wiring and the diffusion layer. Further, since silicon oxide and titanium do not react, the titanium film in the portion in contact with the oxide film does not become titanium silicide but remains as a titanium film.

Next, the unreacted titanium film remaining on the semiconductor substrate is removed by chemical etching or the like so that the titanium silicide film on the diffusion layer and the polysilicon wiring layer is separated. In this way, a titanium silicide film is formed on the diffusion layer and the polysilicon wiring layer, respectively, and the sheet resistance of these diffusion layers and the polysilicon wiring layer is reduced.

[Problems with background technology]

Conventional measures to increase device speed using metal silicide films have the following problems. That is, as shown in FIG. 1a, a titanium film 15 is deposited on a stacked structure of a gate oxide film 12G and a polysilicon layer 14 so as to partially overlap a diffusion layer 13 formed on a semiconductor substrate 11. When heat treatment is performed after this, since the gate oxide film 12G is extremely thin, the diffusion layer 13 and the polysilicon film 1 are formed on the sidewall titanium film 15a deposited on the side surface of the gate oxide film 12G.
Silicon diffuses from 4. Then, this silicon reacts with the sidewall titanium film 15a to form a titanium silicide film, which remains unremoved even after a subsequent step of removing unreacted titanium, and as a result, the polysilicon film 14 and the diffusion layer 13 are The probability of an electrical short circuit was extremely high.

Furthermore, during the heat treatment, the silicon in the diffusion layer 13 continues to diffuse into the titanium film 15 on the field oxide film 12F through the sidewall titanium film 15b deposited on the stepped portion of the field oxide film 12F, and the silicon in the diffusion layer 13 continues to diffuse into the titanium film 15 on the field oxide film 12F. In some cases, the titanium silicide eventually penetrated through the diffusion layer 13 and destroyed the PN junction of the diffusion layer 13, as shown at 13a in FIG. 1B.

[Purpose of the invention]

This invention was made in view of the above points, and its purpose is to apply simple means to the diffusion layer, the polysilicon film formed on the semiconductor substrate, etc. in each region where the resistance should be reduced. It is an object of the present invention to provide a method for manufacturing a semiconductor device in which metal silicide can be formed separately and which can both improve yield and increase the speed of the device.

[Summary of the invention]

That is, in the method for manufacturing a semiconductor device according to the present invention, when a metal film is formed by vapor deposition on a steep step portion or a reversely tapered step portion, vapor deposition particles on the surface of the step portion may be deposited coarsely as in so-called oblique vapor deposition. A so-called abnormally deposited area is created where no deposited particles adhere, and the metal in this area is removed in advance by taking advantage of the phenomenon that the etching rate of the metal film in this abnormally deposited area is faster than that of a metal film deposited on a flat area. It is something to do. That is, first, the upper film such as field oxide film or polysilicon film is
A metal film of titanium, molybdenum, or the like, which can be a metal silicide, is formed on a semiconductor substrate that has been etched by an etching method capable of forming steep steps, such as RIE (reactive ion etching) or sputtering. Subsequently, the metal film is etched, for example, by wet etching until the metal film at the step portion is removed, and the metal film is divided into independent metal films along the step portion on the surface of the substrate. Thereafter, a heat treatment is performed to silicide the metal film formed on the silicon, such as on the diffusion layer or the polysilicon film, and then the metal film that has not been silicided is appropriately removed.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, a diffusion layer 13 with a junction depth of about 0.2 μm is formed in a part of the semiconductor substrate 11, and an upper film with a depth of about 1 μm is formed on the semiconductor substrate 11.
A field oxide film 12F with a thickness of approximately 200 Å, a gate oxide film 12G with a thickness of approximately 200 Å, and a polysilicon film 14 with a thickness of approximately 4000 Å are respectively formed. For patterning these plurality of upper films, for example, RIE method is used so as to obtain steep steps.

Currently, patterning in integrated circuit devices is performed using RIE to achieve higher integration and miniaturization of devices.
Anisotropic etching methods such as the etching method and the sputtering method, in which the etching cross section can be etched substantially vertically and almost no lateral etching occurs, are widely used.

Next, a titanium film 15 is formed on the upper surface of this substrate 11 while the temperature of the substrate 11 is cooled to 10°C to 15°C.
is deposited to a thickness of approximately 1500 Å. At this time, the titanium vapor deposition particles are made to be incident as perpendicularly to the substrate surface as possible. In this way, the substrate 1
1 is cooled to 10°C to 15°C and the evaporated particles are averaged and evaporated almost perpendicularly to the substrate surface for evaporation. This causes the evaporated metal to grow coarsely and abnormally on steeply stepped surfaces, which is referred to as oblique evaporation. , an abnormal growth part A is formed.

Next, this vapor-deposited titanium film 15 is treated with an etchant containing ethylene diamine tetraacetate acid (EDTA) as a main component for approximately 500% of the titanium film 15.
Å Etching.

Here, the abnormally grown portion A is etched at an etching speed about 5 to 10 times that of the normally densely formed titanium film 15.

Therefore, after etching, as shown in FIG. 2b, the abnormal growth part A is completely removed, and the titanium film 1 formed on the field oxide film 12FF, the diffusion layer 13, and the polysilicon film 14 is removed.
5 remains in a divided state.

Subsequently, the semiconductor substrate 11 is heat-treated at 400° C. to 500° C., and the polysilicon film 14 and the top of the diffusion layer 13 are heated.
The upper titanium film 15 is silicided, and as shown in FIG.
As shown in FIG.
A titanium silicide film 16 is formed on each of the layers 4 and 4. Here, since no titanium film remains in the stepped portion, the connection between the titanium silicide film 16 on the diffusion layer 13 and the polysilicon film 14, and the
The phenomenon that silicon in 3 diffuses into the titanium film 15 on the field oxide film 12F does not occur. Furthermore, since the titanium film 15 on the field oxide film 12F is not in contact with silicon, no silicide reaction occurs.

Subsequently, by chemically removing the unreacted titanium film 15 on the field oxide film 12F, the diffusion layer 13
A titanium silicide film 16 is formed on a semiconductor portion such as a polysilicon layer 14 in a divided state along a step portion on a semiconductor substrate.

As described above, for example, the diffusion layer 13 and the polysilicon film 14 do not shoot each other and have a significantly reduced sheet resistance value.

Here, in the above embodiment, the titanium film 15 is obliquely deposited on the stepped portion, titanium particles are densely deposited on the flat portion, and only the titanium film 15 attached to the stepped portion is selectively removed by light etching. In addition, the diffusion layer 13 or the polysilicon film 14
Since the oxide film or the polysilicon layer is patterned to form the region of the diffusion layer 13 or the polysilicon film 14 in a predetermined pattern, there is always a difference in level along the pattern of the diffusion layer 13 or the polysilicon film 14. It is formed. Therefore, in the etching process for the abnormally grown portion A of the titanium film 15, the diffusion layer 13 can be etched without the need for a mask pattern.
The titanium film 15 is divided into regions by self-alignment along the pattern of the polysilicon film 14.

In the above embodiment, titanium is used as the metal for forming the metal silicide with the diffusion layer 13 and the polysilicon film 14, but molybdenum, tungsten, tantalum, platinum, cobalt, aluminum, etc. can be used instead of titanium. Other materials may be used as long as they react with silicon to form metal silicide.

In addition, in the above embodiment, the case where the step part is made steep and the titanium film 15 on the side surface of the step part is obliquely vapor-deposited is described, but for example, as shown in FIG. After forming the stepped portion B into a reverse tapered shape, a separated titanium silicide film can be formed in the same manner as described above. In this case, the titanium film 15 is likely to break off as shown in the figure, and since titanium is not sufficiently adhered to the side surfaces of the stepped portion B, the stepped portion B is etched by light etching of titanium as in the previous embodiment. The nearby titanium film can be completely removed, and the occurrence of shorts between metal silicide films and junction breakdown at the PN junction can be prevented.

〔Effect of the invention〕

As described above, according to the present invention, after a metal film of a metal forming metal silicide is densely deposited on the flat portion of a semiconductor substrate and abnormally deposited on the step portion, the metal film in the abnormally deposited portion is deposited. By removing the metal silicide film and performing heat treatment, it is possible to form a metal silicide film divided into regions such as a diffusion layer or a polysilicon film where low resistance is to be achieved on the semiconductor substrate where silicon is exposed. It is possible to provide a method for manufacturing a semiconductor device that can both improve the yield and increase the speed of the device using simple means.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view explaining a conventional method for manufacturing a semiconductor device, FIG. 2 is a cross-sectional view explaining a method for manufacturing a semiconductor device according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view explaining a method for manufacturing a semiconductor device according to an embodiment of the present invention. It is a sectional view explaining an example. 11... Semiconductor substrate, 12F... Field oxide film, 12G... Gate oxide film, 13... Diffusion layer, 14... Polysilicon film, 15... Titanium film, 16... Titanium silicide film, A... Abnormality Growth part, B... step part.

Claims (1)

[Scope of Claims] 1. A metal forming metal silicide is deposited on the surface of a semiconductor substrate having a stepped portion substantially perpendicularly to the semiconductor substrate, and a metal film made of the metal is deposited on the surface of the semiconductor substrate at the stepped portion. The method includes a step of forming the metal film densely on the flat portion, a step of removing the metal film formed on the stepped portion, and a step of heat-treating the semiconductor substrate to silicide the metal film formed on the flat portion. A method for manufacturing a semiconductor device, characterized in that: 2 The metals forming the metal silicide include molybdenum, tungsten, tantalum, cobalt,
The manufacturing method according to claim 1, characterized in that titanium, platinum, or aluminum is used.