JPH10189722A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent contact characteristics between silicon and a metal and between high-melting metal silicide and the metal, in a silicon semiconductor layer in a part of which a silicide layer is formed. SOLUTION: After a layer insulating film 13 is formed, a contact hole 15 is opened and a contact plug 17 is formed by burying a conductor in this hole. In order to ensure excellent electric connection between a diffusion layer 5 and metal 17 and between a silicide layer 11 and the metal 17 at this time, a natural oxide film formed in the contact hole 15 is removed. For this purpose, a substrate is wet-etched by using a solution which contains a hydrofluoric acid, ammonium fluoride, water and ethylene glycol at least and of which the total content of the hydrofluoric acid and the ammonium fluoride is 5wt.% or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a semiconductor device in which a refractory metal silicide film is formed on a part of a silicon layer. The present invention relates to a method for manufacturing a semiconductor device capable of obtaining good electrical connection between a layer and a metal wiring or the like.

[0002]

2. Description of the Related Art In a semiconductor device, a diffusion layer formed on a silicon substrate, a refractory metal silicide layer, and the like, and a natural wiring formed on these layers in order to obtain good electrical connection with metal wiring. It is necessary to remove a silicon oxide film (hereinafter, referred to as a natural oxide film). Conventionally, as a method of removing this kind of oxide film, a method of removing with a mixed solution of hydrofluoric acid and water, or a method of removing hydrogen fluoride having a weight content of hydrofluoric acid of 3 to 5% A method of removing with a buffered solution (buffer solution) containing an acid, ammonium fluoride and water has been used.

[0003]

However, in the above-mentioned method using the mixed solution and the buffered solution, not only the natural oxide film but also the refractory metal silicide film is etched, and the etching rate is lower than the etching rate of the oxide film. Was also big. FIG. 4 is a schematic diagram for explaining such a situation. The refractory metal silicide layer 32 and the silicon semiconductor layer 34 separated by the LOCOS oxide film 36 are mixed on the semiconductor substrate 30. These layers 3
Since a natural oxide film (not shown) is formed on 2 and 34, if the natural oxide film is to be removed by a conventional method, the silicide layer 32 will be etched together with this oxide film. Therefore, if a sufficient etching time is taken to sufficiently remove the natural oxide film, the etching of the silicide layer 32 also proceeds, which is not preferable in terms of the characteristics of the semiconductor device.

Therefore, an etching solution having a small ratio of the etching rate R _Si of the refractory metal silicide film to the etching rate R _Ox of the silicon oxide film, that is, R _Si / R _Ox has been desired.

On the other hand, Japanese Patent No. 2522389 proposes a method for removing such an oxide film. According to this method, the silicon semiconductor layer is etched with a solution containing hydrofluoric acid, ammonium fluoride, and water that satisfies (HF) / (HF + NH ₄ F + H ₂ O) (weight ratio) of 0.5% or less. To remove the natural oxide film. By using this solution, the ratio R _Si of the etching rate of the refractory metal silicide film to the etching rate of the silicon oxide film can be obtained.
/ R _Ox can be reduced. FIG. 5 shows the etching characteristics in the case of a Ti silicide film. The content of hydrofluoric acid is 0.
It can be seen that the ratio R _Si / R _Ox is small below 5%.

However, this solution is not compositionally stable, and has the property that the etching rate changes as soon as it is used. For this reason, there has been a demand for developing a process that is more easily applied by using a solution having a suitable etching rate and being compositionally stable.

The object of the present invention has been made in view of such a demand, and has been made on the silicon semiconductor layer where the silicide layer is partially formed, between the silicon and the metal and between the high melting point metal silicide and the metal. An object of the present invention is to provide a method for manufacturing a semiconductor device capable of obtaining good contact characteristics.

[0008]

Therefore, the present invention has the following configuration.

In the method of manufacturing a semiconductor device according to the present invention, a step of forming a refractory metal silicide film on a silicon semiconductor layer is performed by using a solution containing at least hydrofluoric acid, ammonium fluoride, water and ethylene glycol. And etching the silicon semiconductor layer with a solution having a total content of hydrofluoric acid and ammonium fluoride of 5% by weight or less.

Thus, a solution containing at least hydrofluoric acid, ammonium fluoride, water and ethylene glycol, wherein the total content of hydrofluoric acid and ammonium fluoride is 5% by weight or less Is stable in composition, so that the etching rate hardly fluctuates.
Furthermore, since this solution also has a characteristic that the ratio of the etching rate of the refractory metal silicide film to the etching rate of the silicon oxide film is small, when a natural oxide film is used for etching, the reduction in the film thickness of the silicide layer is reduced. While
In addition, a natural oxide film can be removed.

In the method of manufacturing a semiconductor device according to the present invention, a step of forming a refractory metal silicide film on a surface of a diffusion layer provided on a silicon semiconductor layer; a step of forming an insulating film on the silicon semiconductor layer; Providing a contact hole in the insulating film for making a connection between the metal wiring and the diffusion layer and a connection between the metal wiring and the high melting point metal silicide film; and containing at least hydrofluoric acid, ammonium fluoride, water and ethylene glycol And the total content of hydrofluoric acid and ammonium fluoride is 5
The method includes a step of etching the silicon semiconductor layer with a solution that is not more than weight% and a step of forming a metal wiring.

Thus, a solution containing at least hydrofluoric acid, ammonium fluoride, water and ethylene glycol, wherein the total content of hydrofluoric acid and ammonium fluoride is 5% by weight or less Is stable in composition, so that the etching rate hardly fluctuates.
In addition, since this solution has a characteristic that the ratio of the etching rate of the refractory metal silicide film to the etching rate of the silicon oxide film is small, when the natural oxide film formed in the contact hole is applied to the etching,
The natural oxide film can be removed while reducing the film loss of the silicide layer. Therefore, good electrical characteristics can be obtained between silicon and the metal and between the high melting point metal silicide and the metal.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. In addition, the same portions are denoted by the same reference numerals, and overlapping description will be omitted.

FIGS. 1 to 3 are schematic cross-sectional views showing process cross-sections of one embodiment of a method for manufacturing a semiconductor device according to the present invention. The present embodiment will be described with reference to these drawings. Note that a case where the silicon semiconductor substrate 1 is used as a silicon semiconductor layer (hereinafter, referred to as a substrate) will be described. Note that a silicon semiconductor layer formed over an insulating substrate may be used.

First, an element isolation film 3 is formed on a substrate 1 (FIG. 1A). The element isolation film 3 has a temperature of 950, for example.
Under a condition of [° C.] and wet oxidation, a thermal oxide film is formed by the LOCOS method. The diffusion layer and the silicide layer formed later are electrically separated by the element isolation film 3.

Next, a diffusion layer 5 is formed (FIG. 1).
(B)). The diffusion layer has, for example, an energy of 10 to 30.
[KeV], dose amount 1 × 10 ¹⁴ to 1 × 10 ¹⁵ [c
m ⁻² ], arsenic (As ⁺ ) is ion-implanted, followed by a heat treatment at a temperature of 900 ° C. for a time of 30 minutes to activate the impurities and form an N-type diffusion layer. When forming a P-type diffusion layer, boron (B ⁺ ) or the like may be implanted.

After forming the diffusion layer 5, a silicide mask film 7 is formed (FIG. 1C). This mask film 7 is an insulating film and is formed so as to cover a diffusion layer on which a silicide layer is not formed. The mask film 7 is formed, for example, by CVD (Ch
A silicon oxide film having a thickness of 500 [nm] is formed on the entire surface of the substrate by an electronic vapor deposition (chemical vapor deposition) method, a pattern is formed by using a photolithography technique, and RIE (Reactive) is performed using this pattern as a mask. Ion Etching)
The oxide film on the diffusion layer on the left side of FIG. 1C is removed by anisotropic etching by a method, thereby forming a mask film 7.

Subsequently, a metal film 9 for forming a silicide is formed (FIG. 2A). As a material of the metal film 9, a metal forming a silicide alloy with silicon is used. Further, a high melting point metal is preferable from the viewpoint of compatibility with the heat process in the semiconductor manufacturing process. In particular, titanium (Ti) is preferably used because a low-resistance silicide can be formed. As another metal material, cobalt (Co), nickel (Ni), or the like may be used. As an example of the conditions for forming the metal film 9, there is a method in which a Ti thin film having a thickness of 30 [nm] is formed over the entire surface of the substrate by a sputtering method. This film forming method is not limited to the sputtering method, but may be a physical vapor deposition method such as a vacuum vapor deposition method or a CVD method.

After forming the metal film 9, the silicide film 1
1 is formed (FIG. 2B). The silicide film 11 is formed by reacting silicon in the diffusion layer 5 and metal in the metal film 9 by heat treatment. An example of the heat treatment conditions is shown below. First, RTA (Rapid Thermal Ann)
eal) method, temperature 650 [° C.], time 30 [sec]
Heat treatment under the conditions described above to react silicon and Ti to form silicide. Ti that did not react with silicon
It is removed using a mixture of sulfuric acid and aqueous hydrogen peroxide. Thereafter, when annealing is performed in a heat treatment furnace at a temperature of 800 ° C. and a time of 30 seconds, a Ti silicide film 11 is formed. Thereby, a refractory metal silicide film is formed on a part of the surface of the substrate.

Next, an insulating film 13 is formed (FIG. 2).
(C)). The insulating film 13 is an interlayer insulating film formed on the entire surface of the substrate in order to insulate the silicide film 11 and the like on the substrate from the metal wiring thereon. An example of the conditions for forming the interlayer insulating film 13 is as follows. An oxide film having a thickness of 800 [nm], for example, a BPSG (boron / phosphorus-doped silicate glass) film is formed by a normal pressure CVD method, and the temperature is 850 [° C.]. ], Time 30
There is a method in which reflow is performed in a heat treatment furnace under the condition of [minutes] to flatten the substrate surface. The material of the interlayer insulating film 13 is not limited to this, and may be a SiN-based, SiON-based,
Other SiO ₂ -based materials or materials containing other elements (elements added to semiconductors as impurities) are preferable because film formation and processing are easy. Further, these plural materials may be laminated and formed. As a method of flattening the insulating film, a resist or SOG (SpinOn Glass) is used.
An etch-back method using s) may be used.

After forming the interlayer insulating film 13, a contact hole 15 is opened (FIG. 3A). The contact hole 15 is formed by forming a pattern in a contact formation region using a photolithography technique, and anisotropically etching the interlayer insulating film 13 by RIE until reaching the conductor layers 5 and 11 formed below the interlayer insulating film 13. Formed.

Subsequently, a pretreatment for forming a contact plug 17 by burying a conductor in the contact hole 15 is performed. An example of this method is shown below.

First, a natural oxide film (not shown) formed on the contact hole 15 is removed by etching in order to obtain good electrical connection between silicon and a metal and between silicide and a metal. As an etching solution, at least hydrofluoric acid, ammonium fluoride,
When a solution containing water and ethylene glycol and having a total content of hydrofluoric acid and ammonium fluoride of 5% by weight or less is used, since the composition is stable, the etching rate is hardly fluctuated and the etching is further performed. The ratio of the rate or the etching rate is in a suitable range. Therefore,
It turned out to be preferable as a solution for removing a native oxide film on the substrate. 180 [sec] as the etching time
The degree is preferable for obtaining good electrical connection with the silicide film 11 and the diffusion layer 5. In the above solution, the reason that the total content of hydrofluoric acid and ammonium fluoride is set to 5% by weight or less is that the selectivity between silicide and the natural oxide film is in a preferable range and the stability of the etching rate is high. Is also good. On the other hand, if the total content exceeds 5% by weight, the stability of the etching rate deteriorates, or the selectivity between the silicide and the native oxide film deteriorates.

The results of measuring the etching rates of various films using one example of the above etching solution are as follows: silicon oxide film: 0.79 [nm / min] Ti silicide film: 1.04 [nm / min] Interlayer insulating film: 2.91 [nm / min] Polysilicon film: 0.74 [nm / min] According to this data, the etching rate of the Ti silicide film is substantially equal to that of the silicon oxide film. For example,
The ratio of the etching rate R _Ti of the Ti silicide film to the etching rate R _Ox of the silicon oxide film is R _Ti / R _Ox =
It is about 1.32. Therefore, the amount of etching of the refractory metal silicide film is smaller than before, and the native oxide film on the substrate surface can be removed stably. Therefore, good electrical connection can be obtained between silicon and the metal, and between silicide and the metal.

Next, a conductive adhesion layer (not shown) is formed on silicon and silicide. The material is preferably TiN or the like because of good adhesion. In addition, the film formation method is preferably a sputtering method because of good step coverage.

Thereafter, a conductor is embedded in the contact hole 15 to form a contact plug 17 (FIG. 3).
(B)). An example of a method for forming the plug 17 is CV
A tungsten (W) film is formed on the entire surface of the substrate by the D method,
There is a method of forming a tungsten plug 17 buried in the contact hole 15 by etching the W film using an etch-back method until the interlayer insulating film 13 is exposed. The material of such a plug 17 is a conductive material, and in particular, a high melting point metal such as tungsten (W), an aluminum alloy, or the like is preferable because film formation and processing are relatively easy.

After forming the plug 17, the wiring 21 is formed (FIG. 3C). The wiring 21 is formed by forming a conductive film over the entire surface of the substrate, forming a wiring pattern using photolithography, and etching using the pattern as a mask. The wiring 21 is formed by, for example, forming an aluminum alloy film containing copper (Cu) by a sputtering method and anisotropically etching by an RIE method. As the other material of the wiring 21, a conductive material such as various aluminum alloys such as pure aluminum, Al-silicon (Si), and Al-Si-Cu is preferable because film formation and processing are easy. Further, a material formed by stacking these materials may be used.

In the above description, a case has been described in which good electrical connection is ensured between the N-type diffusion layer and the metal, and between the refractory metal silicide layer and the metal. However, the N-type diffusion layer is used as the silicon semiconductor layer. However, a P-type diffusion layer may be used. Further, the same can be applied to a portion between a polysilicon layer and a metal.

By using the method described above, it is possible to manufacture a semiconductor device having good contact characteristics between the silicon layer and the metal, between the silicide and the metal, and the like.

Therefore, as described above, a solution containing at least hydrofluoric acid, ammonium fluoride, water and ethylene glycol, wherein the total content of hydrofluoric acid and ammonium fluoride is 5% by weight or less. Is stable in composition, and furthermore, the ratio of the etching rate of the refractory metal silicide film to the silicon oxide film,
That is, since R _Si / R _Ox is small, it is useful as a solution for etching a native oxide film.

[0031]

As described above in detail, in the method of manufacturing a semiconductor device according to the present invention, a solution containing at least hydrofluoric acid, ammonium fluoride, water and ethylene glycol, and A solution having a total content of hydrogen acid and ammonium fluoride of 5% by weight or less is compositionally stable as compared with a conventional solution, so that the etching rate is not easily changed. That is, since the stability of the etching solution is improved, application to a manufacturing process is facilitated.

At the same time, the solution has a ratio R _Si / r of the etching rate of the refractory metal silicide film and the silicon oxide film.
Since R _{Ox is} also small, when etching a natural oxide film formed on a conductive layer such as a silicon layer or a silicide layer,
The natural oxide film can be removed while reducing the removal amount of the silicide film.

Therefore, it is possible to provide a method of manufacturing a semiconductor device in which good electrical connection is ensured between silicon and a metal, between silicide and a metal, and the like.

[Brief description of the drawings]

FIGS. 1A to 1C are schematic cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device according to the present invention.

FIGS. 2A to 2C are schematic cross-sectional views showing one embodiment of a method for manufacturing a semiconductor device according to the present invention.

FIGS. 3A to 3C are schematic cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device according to the present invention.

FIG. 4 is a schematic view of a semiconductor device for explaining a conventional technique.

FIG. 5 is a characteristic diagram showing characteristics of a ratio between an etching rate of a Ti silicide film and an etching rate of a silicon oxide film in a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon semiconductor substrate, 3 ... Element isolation film, 5 ... N type diffusion layer, 7 ... Silicon oxide film, 9 ... Ti film, 11 ... Ti silicide film, 13 ... Insulating film, 15 ... Contact hole,
17 contact plug, 21 wiring

Claims (2)

[Claims] A step of forming a refractory metal silicide film on a silicon semiconductor layer; a step of forming a solution containing at least hydrofluoric acid, ammonium fluoride, water and ethylene glycol; Etching the silicon semiconductor layer with a solution having a total content of ammonium chloride of 5% by weight or less. A step of forming a refractory metal silicide film on a surface of the diffusion layer provided on the silicon semiconductor layer; a step of forming an insulating film on the silicon semiconductor layer; Providing a contact hole for making a connection and a connection between the metal wiring and the refractory metal silicide film in the insulating film; and a solution containing at least hydrofluoric acid, ammonium fluoride, water and ethylene glycol. A step of etching the silicon semiconductor layer with a solution having a total content of hydrofluoric acid and ammonium fluoride of 5% by weight or less; and a step of forming the metal wiring. Semiconductor device manufacturing method.