JP3610710B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device, and in particular, in a semiconductor device in which a refractory metal silicide film is formed on a part of a silicon layer, the silicon layer and the metal wiring, the refractory metal silicide layer and the metal wiring, etc. The present invention relates to a method for manufacturing a semiconductor device capable of obtaining good electrical connection.
[0002]
[Prior art]
In a semiconductor device, in order to obtain a good electrical connection between a diffusion layer formed on a silicon substrate, a refractory metal silicide layer, etc., and a metal wiring, a natural silicon oxide film (hereinafter referred to as a silicon oxide film) formed on these layers is used. It is necessary to remove the 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 hydrogen fluoride whose weight content of hydrofluoric acid is 3 to 5% A method of removing with a buffered solution (buffer solution) containing acid, ammonium fluoride and water has been used.
[0003]
[Problems to be solved by the invention]
However, in the method using the above mixed solution and buffered solution, not only the natural oxide film but also the refractory metal silicide film is etched, and the etching rate is larger than the etching rate of the oxide film. 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. Since a natural oxide film (not shown) is formed on these layers 32 and 34, if the natural oxide film is removed by a conventional method, the silicide layer 32 is also etched together with the oxide film. . For this reason, 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.
[0004]
Therefore, an etching solution having a small ratio between the etching rate R _Si of the refractory metal silicide film and the etching rate R _Ox of the silicon oxide film, that is, R _Si / R _Ox has been desired.
[0005]
On the other hand, Japanese Patent No. 2522389 proposes a method of removing this kind of oxide film. In this method, the silicon semiconductor layer is etched with a solution containing hydrofluoric acid, ammonium fluoride, and water satisfying (HF) / (HF + NH ₄ F + H ₂ O) (weight ratio) of 0.5% or less. The natural oxide film is removed. If this solution is used, the ratio R _Si / R _Ox between the etching rate of the refractory metal silicide film and the etching rate of the silicon oxide film can be reduced. The etching characteristics in the case of the Ti silicide film are shown in FIG. It can be seen that when the content of hydrofluoric acid is 0.5% or less, the ratio R _Si / R _Ox is small.
[0006]
However, this solution is not compositionally stable and has a characteristic that the etching rate changes as soon as it is used. For this reason, it has been desired to develop a process that is easier to apply by using a solution having a suitable etching rate and compositionally stable.
[0007]
The object of the present invention has been made in view of such a demand. On a silicon semiconductor layer partially formed with a silicide layer, good contact is made between silicon and a metal and between a refractory metal silicide and a metal. An object of the present invention is to provide a method for manufacturing a semiconductor device capable of obtaining characteristics.
[0008]
[Means for Solving the Problems]
Therefore, the present invention has the following configuration.
[0009]
In the method for manufacturing a semiconductor device according to the present invention, a step of forming a refractory metal silicide film on a silicon semiconductor layer, and a solution containing at least hydrofluoric acid, ammonium fluoride, water and ethylene glycol, and Etching the natural silicon oxide film on the silicon semiconductor layer and the refractory metal silicide film with a solution having a total content of hydrofluoric acid and ammonium fluoride of 5% by weight or less.
[0010]
Thus, a solution containing at least hydrofluoric acid, ammonium fluoride, water, and ethylene glycol, and having a total content of hydrofluoric acid and ammonium fluoride of 5% by weight or less has a composition The etching rate is less likely to fluctuate. Furthermore, this solution also has a characteristic that the ratio between the etching rate of the refractory metal silicide film and the etching rate of the silicon oxide film is small. Therefore, when a natural oxide film is applied to the etching, the film loss of the silicide layer is reduced. In addition, the natural oxide film can be removed.
[0011]
In a method for manufacturing a semiconductor device according to the present invention, a step of forming a refractory metal silicide film on the surface of a diffusion layer provided on a silicon semiconductor layer, a step of forming an insulating film on the silicon semiconductor layer, a metal wiring, A step of providing an insulating film with a contact hole for connecting the diffusion layer and the metal wiring to the refractory metal silicide film, and a solution containing at least hydrofluoric acid, ammonium fluoride, water and ethylene glycol A step of etching the natural silicon oxide film on the diffusion layer and the refractory metal silicide film with a solution having a total content of hydrofluoric acid and ammonium fluoride of 5% by weight or less, and a metal Forming a wiring.
[0012]
Thus, a solution containing at least hydrofluoric acid, ammonium fluoride, water, and ethylene glycol, and having a total content of hydrofluoric acid and ammonium fluoride of 5% by weight or less has a composition The etching rate is less likely to fluctuate. In addition, since this solution has a characteristic that the ratio between the etching rate of the refractory metal silicide film and 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 also be removed while reducing the film thickness of the layer. Therefore, good electrical characteristics can be obtained between silicon and metal and between refractory metal silicide and metal.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to the accompanying drawings. Moreover, the same code | symbol is attached | subjected to the same part and the overlapping description is abbreviate | omitted.
[0014]
1 to 3 are schematic cross-sectional views showing a process cross-section of one embodiment of a method for manufacturing a semiconductor device according to the present invention. This embodiment will be described with reference to these drawings. A case where the silicon semiconductor substrate 1 (hereinafter referred to as a substrate) is used as the silicon semiconductor layer will be described. Note that a silicon semiconductor layer formed over an insulating substrate may be used.
[0015]
First, the element isolation film 3 is formed on the substrate 1 (FIG. 1A). As the element isolation film 3, for example, a thermal oxide film is formed by the LOCOS method under conditions of a temperature of 950 [° C.] and wet oxidation. The element isolation film 3 electrically isolates a diffusion layer and a silicide layer that will be formed later.
[0016]
Next, the diffusion layer 5 is formed (FIG. 1B). For example, the diffusion layer is ion-implanted with arsenic (As ⁺ ) at an energy of 10 to 30 [keV] and a dose of 1 × 10 ¹⁴ to 1 × 10 ¹⁵ [cm ⁻² ], and then a temperature of 900 [° C.] for a time. A heat treatment of 30 [minutes] is performed to activate the impurities and form an N-type diffusion layer. In the case of forming a P-type diffusion layer, boron (B ⁺ ) or the like may be ion-implanted.
[0017]
After the diffusion layer 5 is formed, a silicide mask film 7 is formed (FIG. 1C). The mask film 7 is an insulating film and is formed so as to cover the diffusion layer where the silicide layer is not formed. The mask film 7 is formed, for example, by forming a silicon oxide film having a thickness of 500 [nm] on the entire surface of the substrate by a CVD (Chemical Vapor Deposition) method and forming a pattern using a photolithography technique. Then, using this pattern as a mask, anisotropic etching is performed by RIE (Reactive Ion Etching) method to remove the oxide film on the diffusion layer on the left side of FIG.
[0018]
Subsequently, a metal film 9 for forming silicide is formed (FIG. 2A). As a material of the metal film 9, a metal that forms a silicide alloy with silicon is used. Furthermore, a refractory metal is preferable from the viewpoint of consistency with the thermal process of the semiconductor manufacturing process. In particular, titanium (Ti) is preferably used because low-resistance silicide can be formed. As other metal materials, cobalt (Co), nickel (Ni), or the like may be used. An example of the deposition conditions for the metal film 9 is a method of depositing a Ti thin film having a thickness of 30 nm on the entire surface of the substrate by sputtering. 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.
[0019]
After the metal film 9 is formed, a silicide film 11 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 heat treatment conditions is shown below. First, by RTA (Rapid Thermal Anneal) method, heat treatment is performed under conditions of a temperature of 650 [° C.] and a time of 30 [seconds] to react silicon and Ti to form silicide. Ti that has not reacted with silicon is removed using a mixed solution of sulfuric acid and hydrogen peroxide. Thereafter, when annealing is performed in a heat treatment furnace under conditions of a temperature of 800 [° C.] and a time of 30 [seconds], the Ti silicide film 11 is formed. Thereby, a refractory metal silicide film is formed on a part of the surface of the substrate.
[0020]
Next, an insulating film 13 is formed (FIG. 2C). The insulating film 13 is an interlayer insulating film formed over the entire surface of the substrate in order to insulate the silicide film 11 and the like on the substrate from the upper metal wiring. An example of the conditions for forming the interlayer insulating film 13 is to form an oxide film having a thickness of 800 [nm], for example, a BPSG (boron, phosphorus, doped silicate glass) film by an atmospheric pressure CVD method, and a temperature of 850 [° C. There is a method in which reflow is performed in a heat treatment furnace under the condition of time 30 [minutes] to flatten the substrate surface. As the material of the interlayer insulating film 13, without being limited thereto, SiN-based, SiON-based material or the like is contained other Si0 ₂ system or these other elements (element added as an impurity into the semiconductor) has, It is preferable because film formation and processing are easy. Further, these plural materials may be laminated and formed. As a method for planarizing the insulating film, an etch back method using resist or SOG (Spin On Glass) may be used.
[0021]
After forming the interlayer insulating film 13, a contact hole 15 is opened (FIG. 3A). The contact hole 15 forms a pattern in a contact formation region using a photolithography technique, and anisotropically etches the interlayer insulating film 13 by RIE until reaching the conductor layers 5 and 11 formed under the interlayer insulating film 13. To form.
[0022]
Subsequently, a pretreatment for forming a contact plug 17 by filling a conductor in the contact hole 15 is performed. An example of this method is shown below.
[0023]
First, a natural oxide film (not shown) formed on the contact hole 15 is removed by etching in order to achieve good electrical connection between silicon and metal and between silicide and metal. As an etching solution, when a solution containing at least hydrofluoric acid, ammonium fluoride, water, and ethylene glycol and having a total content of hydrofluoric acid and ammonium fluoride of 5% by weight or less is used, Therefore, the etching rate is difficult to vary, and the etching rate or the ratio of the etching rates is within a preferable range. Therefore, it was found that the solution is preferable as a solution for removing the natural oxide film on the substrate. An etching time of about 180 [seconds] is preferable for achieving good electrical connection between the silicide film 11 and the diffusion layer 5. In the above solution, the total content of hydrofluoric acid and ammonium fluoride is 5% by weight or less because the selection ratio between the silicide and the natural oxide film is in a preferable range and the etching rate is stable. It is because it is also favorable. On the other hand, if the total content exceeds 5% by weight, the stability of the etching rate is deteriorated or the selectivity between the silicide and the natural oxide film is deteriorated.
[0024]
Using an example of the etching solution, the results of measuring the etching rate of various films are shown 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]
It becomes. From this data, the Ti silicide film has an etching rate almost equal to that of the silicon oxide film. For example, the ratio between the etching rate R _Ti of the Ti silicide film and the etching rate R _Ox of the silicon oxide film is about R _Ti / R _Ox = 1.32. On the other hand, when the natural oxide film is removed by a buffered solution containing hydrofluoric acid, ammonium fluoride, and water having a conventional hydrofluoric acid weight content of 3 to 5%, As shown in FIG. 5, the etching rate of the titanium silicide film / the etching rate of the silicon oxide film (R _Ti / R _Ox ) = about 3 to 5. Thus, the etching amount of the refractory metal silicide film is less than before, and the natural oxide film on the surface of the substrate can be stably removed. Therefore, good electrical connection can be established between silicon and metal and between silicide and metal.
[0025]
Next, a conductive adhesion layer (not shown) is formed on silicon and silicide. Since the adhesiveness is good, TiN or the like is preferable as the material. Further, the film forming method is preferably a sputtering method because step coverage is good.
[0026]
Thereafter, a contact plug 17 is formed by burying a conductor in the contact hole 15 (FIG. 3B). An example of a method for forming the plug 17 is to form a tungsten (W) film on the entire surface of the substrate by the CVD method, and etch the W film using the etch back method until the interlayer insulating film 13 is exposed. There is a method of forming a tungsten plug 17 embedded in the substrate 15. The plug 17 is preferably made of a conductive material, and particularly a refractory metal such as tungsten (W), an aluminum alloy, or the like because it is relatively easy to form and process.
[0027]
After forming the plug 17, the wiring 21 is formed (FIG. 3C). The wiring 21 is formed by forming a conductive film on the entire surface of the substrate, forming a wiring pattern using a photolithography technique, and etching this pattern as a mask. For example, the wiring 21 is formed by forming an aluminum alloy film containing copper (Cu) by a sputtering method and performing anisotropic etching by an RIE method. Other materials for the wiring 21 are preferably conductive materials such as various aluminum alloys such as pure aluminum, Al-silicon (Si), and Al-Si-Cu because they can be easily formed and processed. Moreover, you may use what formed by laminating | stacking these materials.
[0028]
In the above description, the case of ensuring good electrical connection between the N-type diffusion layer and the metal and between the refractory metal silicide layer and the metal has been described. However, the silicon semiconductor layer is limited to the N-type diffusion layer. Alternatively, a P-type diffusion layer may be used. Further, the present invention can be similarly applied between the polysilicon layer and the metal.
[0029]
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, or the like.
[0030]
Therefore, as described above, a solution containing at least hydrofluoric acid, ammonium fluoride, water, and ethylene glycol, the total content of hydrofluoric acid and ammonium fluoride being 5% by weight or less Since the composition is stable and the ratio between the etching rate of the refractory metal silicide film and the silicon oxide film, that is, R _Si / R _Ox is small, it is useful as a solution for etching a natural oxide film.
[0031]
【The invention's effect】
As described above in detail, in the method for manufacturing a semiconductor device according to the present invention, a solution containing at least hydrofluoric acid, ammonium fluoride, water and ethylene glycol, and hydrofluoric acid and fluoride A solution having a total ammonium content of 5% by weight or less is compositionally more stable than 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 the manufacturing process is facilitated.
[0032]
In addition, since this solution has a small ratio R _Si / R _Ox between the refractory metal silicide film and the etching rate of the silicon oxide film, the natural oxide film formed on the conductive layer such as the silicon layer or the silicide layer is etched. In this case, the natural oxide film can be removed while reducing the removal amount of the silicide film.
[0033]
Therefore, it is possible to provide a method for manufacturing a semiconductor device that ensures good electrical connection between silicon and metal, between silicide and metal, or the like.
[Brief description of the drawings]
FIGS. 1A to 1C are schematic cross-sectional views showing one embodiment of a method for manufacturing a semiconductor device according to the present invention, respectively.
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, respectively.
FIGS. 3A to 3C are schematic sectional views showing one embodiment of a method for manufacturing a semiconductor device according to the present invention.
FIG. 4 is a schematic diagram of a semiconductor device for explaining a conventional technique.
FIG. 5 is a characteristic diagram showing a characteristic of a ratio between an etching rate of a Ti silicide film and an etching rate of a silicon oxide film in the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Silicon semiconductor substrate, 3 ... Element isolation film, 5 ... N type diffused 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)

Forming a refractory metal silicide film on the silicon semiconductor layer;
A solution containing at least hydrofluoric acid, ammonium fluoride, water and ethylene glycol, and having a total content of hydrofluoric acid and ammonium fluoride of 5% by weight or less on the silicon semiconductor layer and Etching a natural silicon oxide film on the refractory metal silicide film;
A method for manufacturing a semiconductor device, comprising: Forming a refractory metal silicide film on the surface of the diffusion layer provided on the silicon semiconductor film;
Forming an insulating film on the silicon semiconductor layer;
Providing a contact hole in the insulating film for connecting the metal wiring and the diffusion layer and connecting the metal wiring and the refractory metal silicide film;
A solution containing at least hydrofluoric acid, ammonium fluoride, water and ethylene glycol, and having a total content of hydrofluoric acid and ammonium fluoride of 5% by weight or less on the diffusion layer and Etching a natural silicon oxide film on the refractory metal silicide film;
Forming the metal wiring;
A method for manufacturing a semiconductor device, comprising:

Images