JPH05160065A - Forming method of silicide plug - Google Patents

Abstract

PURPOSE:To obtain a stable TiSi2 plug which is excellent in burying properties, low in leakage and contact resistance, and hardly corrodes a base. CONSTITUTION:A silicide plug is formed through such a method that an opening 16 is provided to an interlayer insulating layer 14 formed on a semiconductor substrate 10 and silicide is filled into the opening 16. In a first way, a process where a silicon layer 18 is formed on the base of an opening and another process where silicide is filled into the opening through a CVD method are provided. In a second way, a process where a silicide thin film is formed on the base of an opening and then the thin film is nitrided, and another process where silicide is filled into the opening through a CVD method are provided.

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 plug in a contact hole of a semiconductor device.

[0002]

2. Description of the Related Art In a VLSI, there is a tungsten CVD method as a technique for filling a fine opening with a wiring material to form a contact hole (hereinafter also referred to as a connection hole). The tungsten CVD method has excellent step coverage and burying ability as compared with the conventional tungsten sputtering method. In the tungsten CVD method, for example, WF ₆ gas / SiH ₄ gas and H ₂ gas are used.
WF ₆ is reduced by H ₄ and H ₂ and tungsten is deposited in the openings.

The tungsten CVD method includes a blanket tungsten CVD method and a selective tungsten CVD method. Currently, the blanket tungsten CVD method is the mainstream. In the blanket tungsten CVD method, an interlayer insulating layer is formed on the surface of a semiconductor substrate and an opening is provided in the interlayer insulating layer. Then, after depositing tungsten by CVD on the surface of the interlayer insulating layer and in the opening, the tungsten is left only in the opening by etch back. As a result, a metal plug made of tungsten is formed in the opening, and the connection hole is completed.

In the selective tungsten CVD method, tungsten is difficult to grow on the surface of the insulating film, and the tungsten is selectively grown only in the opening by the CVD method.
With this method, a metal plug made of tungsten is formed in the opening to complete the connection hole.

In the blanket tungsten CVD method, the adhesion between tungsten and the underlying silicon oxide film is not so good. Is intervened between. TiN
Has a high contact resistance, so titanium (Ti) or titanium silicide (T
iSi ₂ ) is deposited to reduce the contact resistance.

At present, since these adhesion layers are deposited by the sputtering method, the coverage of the adhesion layer on the bottom of the opening having a high aspect ratio and a small diameter formed in the interlayer insulating layer is poor. As a result, there is a problem in that the silicidation of titanium does not occur uniformly under the influence of the natural oxide film, and the contact resistance increases.

Further, in the blanket tungsten CVD method, the tungsten plug formed in the connection hole has a multilayer structure of tungsten (W) / TiN / Ti. Therefore, it is necessary to etch W with a fluorine-based gas and TiN / Ti with a chlorine-based gas at the time of etchback, which causes a problem that the etchback process becomes complicated.

As a means for solving the above problems of the blanket tungsten CVD method, a method of forming a TiN film by the CVD method to form a plug made of TiN is being studied. However, even if a TiN film with a small amount of impurities in the film and excellent step coverage is obtained by the CVD method, the TiN plug itself has a high resistance, and in order to obtain a low contact resistance, a Ti layer or TiSi _x film is required. Need layers.

Instead of a plug of tungsten or TiN, the opening is filled with a single layer of TiSi _x ,
A technique has been proposed in which a plug made of TiSi ₂ is formed in the contact hole to realize a low contact resistance and to simplify the etchback process. Currently, as a method of forming this TiSi _x embedded plug,
The following methods can be mentioned. (A) Thermal CV using TiCl ₄ gas and SiH ₄ gas
The opening is embedded by the D method (for example, "Contact
Plug Formed With Chemical Vapor Deposited TiN '',
K. Mori, et al, Extended Abstracts of the 1991 Int
ernational Conference on Solid State Device and Ma
terials, Yokohama, 1991, pp. 210-212). (B) After selectively forming an epitaxial or polycrystalline silicon layer in the opening, titanium is deposited on the silicon layer by sputtering. Then, an annealing process is performed to cause titanium and silicon in the opening to react with _{each other} to form TiSi ₂ only in the opening (for example, “The Use of Selective Silicon Or Silici
de Plugs For Submicron Contact Fill '', CS Wei et
al, ULSI Sci Tech, 1989, pp.637-648).

[0010]

In these methods of filling the opening with TiSi ₂ , the plug can be formed by etching back the TiSi _x layer by plasma etching with a chlorine-based gas. Therefore, the etching process can be simplified as compared with the blanket tungsten CVD method.

However, the above method also has the following problems. (A) The method (A) has excellent embedding property, but when the ratio of TiCl ₄ gas to SiH ₄ gas changes, the quality of the formed TiSi _x film changes greatly. In particular, when the ratio of SiH ₄ / TiCl ₄ is a small value such as 0 to 1, TiCl ₄ may erode the underlying diffusion layer. Also, the TiSi _x film forming temperature is about 700.
It is as high as ° C. Therefore, TiCl _{4 as the} source gas significantly corrodes the underlying diffusion layer, and the leak current increases. (B) In the above method (B), since titanium is deposited by the sputtering method, the coverage of titanium in the opening having a small diameter is poor, and voids are likely to occur in the titanium deposited in the opening.

Therefore, an object of the present invention is to establish a technique for forming a stable plug of TiSi ₂ which is excellent in embedding property, has no fear of eroding the base, and can obtain low leak and low contact resistance. It is in.

[0013]

According to a method of forming a silicide plug of the present invention for achieving the above object, an opening is provided in an interlayer insulating layer formed on a semiconductor substrate, and the opening is filled with silicide. Is the way.

The first aspect of the method for forming a silicide plug of the present invention is (a) a step of forming a silicon layer at least at the bottom of the opening, and (b) filling the opening with silicide by a CVD method. It is characterized by comprising a process.

In the first aspect, in the step (a), it is desirable to form a silicon layer on the bottom of the opening, the side wall and the surface of the interlayer insulating layer. Further, the silicide is preferably made of titanium silicide. Subsequent to the step (b), it is preferable to nitride the surface of the silicide embedded in the opening.

A second aspect of the method for forming a silicide plug of the present invention is to include (a) a step of forming a thin film of silicide at least at the bottom of the opening and then nitriding the thin film, and (b) a CVD method. And filling the opening with silicide.

In the second aspect, it is preferable that the thin film of silicide in the step (a) is formed by a plasma CVD method. Further, it is desirable to nitride the surface of the silicide embedded in the opening after the step (b).

[0018]

In the method for forming a silicide according to the first aspect of the present invention, since the silicon layer is formed at least at the bottom of the opening, the silicide source gas does not come into direct contact with the base, and the source gas is It is possible to prevent erosion of the base due to. Further, since the opening is filled with the silicide by the CVD method, the burying property of the silicide in the opening is excellent.

In the method of forming a silicide according to the second aspect of the present invention, since a thin film made of silicide is formed at least at the bottom of the opening, the thin film is nitrided. Also, the barrier property of the silicide against the source gas is improved.
Therefore, the raw material gas of the silicide does not come into direct contact with the base, and the base gas can be more effectively prevented from being eroded by the raw material gas. Further, since the opening is filled with the silicide by the CVD method, the burying property of the silicide in the opening is excellent.

In the first and second aspects of the present invention, subsequent to the step (b), the surface of the silicide embedded in the opening is nitrided to thereby form a TiN barrier layer for the aluminum wiring formed thereafter. Can be easily formed on the plug surface.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments with reference to the drawings. Each drawing is a schematic partial cross-sectional view of the semiconductor element.

(Embodiment 1) First, the first aspect of the method for forming a silicide plug of the present invention will be explained based on Embodiment 1.

[Step-100] After the diffusion layer 12 is formed on the semiconductor substrate 10, the interlayer insulating layer 14 is deposited thereon, and then the opening 16 is formed in the interlayer insulating layer 14 ((A in FIG. 1). )reference). The opening 16 can have a diameter of 0.4 μm and an aspect ratio of 2, for example.

[Step-110] Next, after removing the natural oxide film by dilute hydrofluoric acid cleaning, a silicon layer 18 having a film thickness of 20 to 40 nm is selectively formed at the bottom of the opening 16 (FIG. 1).
(B)). The silicon layer 18 can be formed, for example, by selective epitaxial Si growth or selective polycrystalline Si growth. When selective epitaxial Si growth is used, the conditions are SiH ₂ Cl ₂ = 300 s
ccm, HCl = 300 to 1000 sccm, pressure 30
The temperature can be set to 00 to 7000 Pa and the temperature to 800 to 1000 ° C. When the selective polycrystalline Si growth is used, the conditions can be SiH ₂ Cl ₂ / HCl = 2 to 3, pressure 1000 Pa, and temperature 700 to 800 ° C.

[Step-120] Next, the opening is filled with silicide by the thermal CVD method. This step will be described below in Step-120A to Step-120C.

[Step-120A] Using TiCl ₄ and SiH ₄ as the source gas for silicide, a thermal CVD method is used to deposit TiSi _{x on} the surface of the interlayer insulating layer 14 and inside the opening 16.
The layer 20 is deposited (see FIG. 1C). TiSi _x
The conditions for depositing the layer 20 can be, for example, a temperature of 700 ° C. and SiH ₄ / TiCl ₄ = 1 to 5.
Care must be taken not to generate voids in the TiSi _X layer 20 inside the opening 16. The formed TiS
The value of X of i _X is about 1.0 to 1.8. In this step, since the silicon layer 18 has already been formed at the bottom of the opening 16, the TiCl ₄ gas does not come into direct contact with the diffusion layer 12 and the erosion of the diffusion layer 12 by TiCl ₄ can be prevented. it can.

[Step-120B] Next, under N ₂ , NH ₃ or Ar gas atmosphere, 800-1000 ° C., 30-
Annealing treatment is performed under the condition of 60 seconds, and the silicon layer 18 and the TiSi _x layer 20 are reacted with each other at the bottom of the opening 16 to generate the TiSi ₂ layer 22 ((A) of FIG. 2).
reference). That is, the deposited TiSi _X layer 20 (X = 1.0
.About.1.8) is Ti-rich, the annealing treatment causes the silicon layer 18 at the bottom of the opening 16 to be TiSi.
It is diffused and absorbed in the _X layer 20. This allows TiSi _x
Becomes stoichiometrically TiSi ₂ and a TiSi ₂ layer 22 is formed. Since the TiSi ₂ layer 22 is in direct contact with the diffusion layer 12, low contact resistance is obtained.

[Step-120C] Next, the TiSi ₂ layer 22 formed on the surface of the interlayer insulating layer 14 is etched back and removed by plasma etching using a chlorine-based gas, and only in the opening 16. The TiSi ₂ layer 22 is left (see FIG. 2B). The etch back conditions are Cl ₂
/ Ar = 50/25 sccm, RF power 250 W, pressure 20 Pa. As a result, the opening 16 is filled with the silicide made of TiSi _2, and the connection hole having the silicide plug is completed. In the blanket tungsten CVD method, since it is necessary to etch back the W / TiN / Ti multilayer structure layer, it is necessary to etch W with a fluorine-based gas and TiN / Ti with a chlorine-based gas. The process becomes complicated. On the other hand, in the present invention, the etch back process is simplified because it is sufficient to etch back TiSi ₂ .

[Step-130] After forming a plug made of TiSi ₂ , if necessary, the surface of the plug is nitrided in an NH ₃ atmosphere at a temperature of 700 to 900 ° C. for 10 to 60 seconds. TiN24 can be formed (see FIG. 2C).

[Step-140] Next, an aluminum wiring is formed by a usual method. That is, Ti is sputtered
ON and aluminum may be sequentially deposited to form an aluminum wiring layer (see FIG. 3).

Example-2 The first aspect of the method for forming a silicide plug of the present invention will be further described with reference to Example-2. In Example-1, the silicon layer 18 was formed on the bottom of the opening 16, but in Example-2, the silicon layer is formed not only on the opening 16 but also on the surface of the interlayer insulating layer 14.

[Step-200] This step is the same as Example-1.
Since it is the same as the process-100 in step No. 1, detailed description thereof will be omitted.

[Step-210] Next, after removing the natural oxide film by cleaning with dilute hydrofluoric acid, a silicon layer 18 having a film thickness of 20 to 40 μm is formed on the bottom and side walls of the opening 16 and the interlayer insulating layer 14. (See Figure 4). The silicon layer 18 can be formed, for example, by amorphous Si growth or polycrystalline Si growth. When using amorphous Si growth, the conditions are SiH ₄ / He = 500/3
The pressure can be 0 sccm, the pressure is 270 Pa, and the temperature is 550 ° C. When polycrystalline Si growth is used, the conditions can be SiH ₄ / He = 100/400 sccm, pressure 70 Pa, and temperature 650 ° C.

[Step-220] to [Step-240] The following steps are from [Step-120A] in Example-1.
[Step-120C], [Step-130] and [Step-1]
40] and detailed description thereof will be omitted. However, in the step-220, Ti on the surface of the interlayer insulating layer 14 is
Not only the Si ₂ layer but also the silicon layer 18 is etched back.

(Embodiment 3) A second aspect of the method for forming a silicide plug of the present invention will be described based on Embodiment 3. In Example-1 and Example-2, the silicon layer 18 was formed at least on the bottom of the opening 16, but Example-3 was used.
In (1), after forming a thin film of TiSi _{x on} the bottom of the opening, this thin film is nitrided.

[Step-300] This step is the same as Example-1.
Since it is the same as the process-100 in step No. 1, detailed description thereof will be omitted.

[Step-310] Next, a thin film of silicide is formed on the bottom of the opening by thermal CVD, and then the thin film is nitrided. This step is hereinafter referred to as step-310A-
It demonstrates in process-310B. [Step-310A] First, using TiCl ₄ and SiH ₄ as source gases, a thin film 30 made of TiSi _{X is} formed by thermal CVD on the bottom and side walls of the opening 16 and the surface of the interlayer insulating layer 14 (FIG. 5 (A)). Thin film 3
The formation condition of 0 is, for example, SiH ₄ / TiCl ₄ = 8 to 1
The temperature may be 0 and the temperature may be 700 ° C. [Step-310B] Next, lamp annealing is performed in an ammonia (NH ₃ ) atmosphere at 800 ° C. for 30 seconds to nitride the surface of the thin film 30 made of TiSi _x (see FIG. 5B). ). This allows TiSi _x
The thin film 30 made of is a TiN layer 32 / TiSi _x layer 34.
To a thin film having a two-layer structure.

[Step-320] Next, the opening is filled with a silicide of TiSi _x by the thermal CVD method. This step will be described below according to steps-320A and 320B.

[Step-320A] First, the TiSi _X layer 20 is formed into 800 to 10 layers until the opening 16 is sufficiently filled.
It is deposited to a thickness of 00 nm in the opening 16 and on the surface of the interlayer insulating layer 14 by a thermal CVD method (see FIG. 5C). TiS
The deposition conditions of the i _X layer 20 are the same as the formation conditions of the thin film 30 described in Step-310A. At the bottom of the opening 16, the TiN layer formed in Step-310B is present, so the TiN layer used for depositing the TiSi _x layer 20 is Ti.
It is possible to prevent Cl ₄ from eroding the underlying diffusion layer.

[0040] [Step -320B] Next, by plasma etching using a chlorine-based gas, TiSi _X layer 20 formed on the surface of the interlayer insulating layer 14, TiN layer 32 / T
The iSi _X layer 34 is etched back and removed to form the opening 16
The TiSi _x layer 20 is left only inside (see FIG. 6). The etch back conditions are Cl ₂ / Ar = 50/25 sccm,
The RF power may be 250 W and the pressure may be 20 Pa. As a result, the opening 16 is filled with the silicide made of TiSi _2, and the connection hole having the silicide plug is completed.

Since the steps after [Step-330] and [Step-340] are the same as [Step-130] and [Step-140] of Example-1, detailed description will be omitted.

(Embodiment 4) The erosion phenomenon of WF ₆ on the underlying diffusion layer observed by the selective tungsten CVD method becomes more remarkable as the CVD growth temperature becomes higher. In Example-3, the thermal CVD method was used to form the thin film 30 made of TiSi _x , and the temperature condition was 700 ° C.
In the example 4, the thin film 30 made of TiSi _x is formed by the plasma CVD method. T by plasma CVD method
The temperature condition for forming the thin film 30 of iSi _x can be about 450 ° C.
It is possible to further prevent the erosion of Cl _{4 on} the base.

[Step-400] This step is the same as Example-1.
Since it is the same as the process-100 in step No. 1, detailed description thereof will be omitted.

[Step-410] Next, a thin film of silicide is formed on the bottom of the opening by plasma CVD, and then the thin film is nitrided. This step will be referred to as step-41 below.
0A to step-410B will be described.

[Step-410A] First, similarly to the case shown in FIG. 5A, TiCl ₄ and SiH _{4 were used} as source gases.
Using a plasma thin film 30 made of TiSi _X on the bottom and side walls and the surface of the interlayer insulating layer 14 of the opening 16 C
It is formed by the VD method. The conditions for forming the thin film 30 are, for example,
SiH ₄ / TiCl ₄ = 1 to 8, temperature 450 ° C., and RF power 200 to 400 W. TiSi _x
Since the forming temperature of the thin film 30 composed of is as low as 450 ° C,
The erosion of TICl _{4 on} the substrate is less than that of the thermal CVD method.

[Step-410B] Next, in the same manner as shown in FIG. 5B, for example, 700 to 900 ° C., 10 to 6
Annealing is performed for 0 seconds in an ammonia (NH ₃ ) atmosphere to nitride the surface of the thin film 30 made of TiSi _x . As a result, the thin film 30 made of TiSi _x has a T
The thin film has a two-layer structure of iN layer 32 / TiSi _x layer 34.

[Step-420] to [Step-440] CV
The steps subsequent to the step of filling the opening with the silicide made of TiSi _x by the D method are the same as those in [Step-320 of Example-3].
Since it is similar to A] to [Step-340], detailed description will be omitted.

The present invention has been described above based on the preferred embodiments, but the present invention is not limited to these embodiments. Various conditions in each step are exemplifications, and depend on an apparatus and the like used for carrying out the method of the present invention.

[0049]

In the present invention, since the silicon layer or the TiN layer / TiSi _X layer on at least the bottom portion of the opening portion is formed, without the raw material gas of the silicide is in direct contact with the underlying base by the material gas The erosion can be effectively prevented. As a result, a silicide plug with low leak and low contact resistance can be formed.

Further, since the plug is formed of TiSi _x , the etchback process can be simplified and the resistance of the plug itself can be reduced. Furthermore, since the opening is filled with silicide by the CVD method, the filling property is excellent. If the surface of the plug is nitrided after forming the silicide plug, the TiN barrier layer for the aluminum wiring can be easily formed.

[Brief description of drawings]

FIG. 1 is a schematic partial cross-sectional view of a semiconductor device showing each step of the method described in Example-1 of the present invention.

FIG. 2 is a schematic partial cross-sectional view of a semiconductor device for showing each step following FIG.

FIG. 3 is a schematic partial cross-sectional view of the semiconductor element for showing each step following FIG.

FIG. 4 is a schematic partial cross-sectional view of a semiconductor device showing a part of each step of the method described in Example-2 of the present invention.

FIG. 5 is a schematic partial cross-sectional view of a semiconductor device showing a part of the steps of the methods described in Examples-3 and 4 of the present invention.

FIG. 6 is a schematic partial cross-sectional view of the semiconductor element for showing each step following FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Semiconductor substrate 12 Diffusion layer 14 Interlayer insulation layer 16 Opening 18 Silicon layer 20 TiSi _X layer 22 TiSi ₂ layer 24 TiN layer 30 Thin film made of silicide 32 TiN layer 34 TiSi _X layer

Claims (7)

[Claims] 1. A method of forming an opening in an interlayer insulating layer formed on a semiconductor substrate, and filling the opening with silicide to form a silicide plug, comprising: (a) forming a silicon layer at least at the bottom of the opening. A method for forming a silicide plug, which comprises: a step of forming a silicide plug; and (b) a step of filling the opening with silicide by a CVD method. 2. The method for forming a silicide plug according to claim 1, wherein in the step (a), a silicon layer is formed on the bottom of the opening, the side wall and the surface of the interlayer insulating layer. 3. The method for forming a silicide plug according to claim 1, wherein the silicide is titanium silicide. 4. The formation of the silicide plug according to any one of claims 1 to 3, wherein after the step (b), the surface of the silicide embedded in the opening is nitrided. Method. 5. A method for forming an opening in an interlayer insulating layer formed on a semiconductor substrate and filling the opening with silicide to form a silicide plug, which comprises (a) at least a bottom of the opening made of silicide. A method for forming a silicide plug, comprising: a step of nitriding the thin film after forming the thin film; and (b) a step of filling the opening with silicide by a CVD method. 6. The method of forming a silicide plug according to claim 5, wherein the thin film of silicide in the step (a) is formed by a plasma CVD method. 7. The method for forming a silicide plug according to claim 5, wherein after the step (b), the surface of the silicide embedded in the opening is nitrided.