JP2003197924A - Semiconductor element and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a convenient and highly reliable semiconductor element equipped with a shot key barrier electrode and a semiconductor element. <P>SOLUTION: A first metallic layer 19 made of Pd silicide is formed so as to be exposed in a contact opening 18 of an insulating film 17 in the surface area of a semiconductor substrate 12. A second metallic layer 20 made of Ti silicide is formed on the surface of the first metallic layer and the insulating film 17. Then, a third metallic layer made of Al is formed on the second metallic layer so that a shot key barrier electrode 13 made of three metallic layers 19, 20, and 21 can be formed. In this case, the first metallic layer 19 is formed by the thermal diffusion of the Pd to the surface area of the semiconductor substrate 12 through the second metallic layer 20. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having a Schottky barrier electrode and a semiconductor device.

[0002]

2. Description of the Related Art A Schottky barrier diode using a Schottky junction is widely used as a switching element or the like. The Schottky barrier diode includes a semiconductor substrate, a silicon-based insulating film having an opening on one surface of the semiconductor substrate, and an anode electrode (Schottky barrier electrode) electrically connected to the one surface of the semiconductor substrate through the opening. )
And a cathode electrode provided on the other surface of the semiconductor substrate and in ohmic contact with the semiconductor substrate.

The Schottky barrier electrode forms a Schottky barrier having a predetermined barrier height at the interface with one surface of the semiconductor substrate. The size of the barrier height of the Schottky barrier is determined by the material of the metal film forming the Schottky barrier electrode. Therefore, the metal material forming the Schottky barrier electrode is appropriately selected according to the desired size of the barrier height.

Here, in order to form a Schottky barrier having a desired barrier height, for example, palladium (P
In some cases, a material such as d) having low adhesion to the silicon-based insulating film is used. In such a case, a structure in which the Schottky barrier electrode is composed of a plurality of metal films as shown in FIG. 4 is adopted.

The Schottky barrier diode 1 shown in FIG.
The Schottky barrier electrode 101 of 00 has a thin metal film (barrier metal film 105) in contact with the semiconductor substrate 104 in the contact opening 103 of the insulating film 102, and the barrier metal film 1
05, a metal film (overoxide film 106) formed on one surface of the semiconductor substrate 104 and a metal film (electrode metal film 107) formed on the overoxide film 106.

In the structure shown in FIG. 4, the overoxide film 106 is made of a metal having a high adhesiveness with the insulating film 102 (silicon oxide film), for example, titanium (Ti).
Further, the electrode metal film 107 is made of a metal capable of favorably performing wire bonding or the like, for example, aluminum (Al). The overoxide film 106 also has high adhesion to Al, which is a metal, and as a result, the Schottky barrier electrode 101 as a whole has high adhesion to the insulating film.

The barrier metal film forming the Schottky barrier electrode as described above is formed by using, for example, the lift-off method or the ultrasonic peeling method. When the lift-off method is used, first, a semiconductor substrate is prepared, and an insulating film having a contact opening is formed on one surface of the semiconductor substrate. Then, a resist film is formed on one surface of the semiconductor substrate, and an opening communicating with the contact opening is formed. Further, a metal film such as Pd forming a barrier metal film is formed on one surface of the semiconductor substrate. Finally, the metal film formed on the resist film is removed together with the resist film. As a result, the barrier metal film is selectively formed in the contact opening.

According to the ultrasonic peeling method, first, a semiconductor substrate is prepared, and an insulating film having a contact opening is formed on one surface of the semiconductor substrate. Next, a metal film forming a barrier electrode is formed on one surface of the semiconductor substrate. Then, the semiconductor substrate is immersed in water or an organic solvent, and ultrasonic vibration is applied. By applying ultrasonic vibration, the electrode film on the insulating film, which has low adhesiveness to the insulating film, is peeled and removed due to the difference in adhesiveness between the insulating film and the semiconductor substrate. As a result, the barrier metal film is selectively formed in the contact opening.

[0009]

The method of forming the Schottky barrier electrode in which a plurality of metal films are laminated as described above has the following problems. For example, the above method generally requires complicated steps such as using an ultrasonic device. Further, when the lift-off method is used, since the metal film is formed on the resist film, the inside of the film forming apparatus is easily contaminated, and the reliability of the process may be reduced. Further, when the ultrasonic peeling method is used, the metal particles peeled from the insulating film by the ultrasonic treatment may be redeposited on the semiconductor substrate or the metal film, which may reduce the reliability of the treatment.

As described above, in the conventional method for manufacturing a semiconductor element having a Schottky barrier electrode having a barrier electrode having low adhesion to an insulating film, the steps are complicated and a highly reliable semiconductor element is obtained. I couldn't do it.

In view of the above circumstances, it is an object of the present invention to provide a method for manufacturing a semiconductor device having a Schottky electrode, which is simple and highly reliable, and a semiconductor device.

[0012]

In order to solve the above-mentioned object, a method of manufacturing a semiconductor device according to a first aspect of the present invention is provided so as to be in contact with one surface of a semiconductor substrate containing silicon. A method of manufacturing a semiconductor device having a Schottky barrier electrode for forming a Schottky barrier between the insulating film and a surface of the semiconductor substrate, the method comprising: forming a silicon-based insulating film having an opening on one surface of the semiconductor substrate; A step of sequentially forming a first metal layer containing a first metal and a second metal layer containing a second metal thereon; and the second metal contained in the second metal layer. Is thermally diffused to the surface region of the semiconductor substrate through the first metal layer,
A thermal diffusion step of contacting the first metal layer through the opening to form a third metal layer containing a silicide of the second metal; and an external electrode on one surface of the semiconductor substrate after thermal diffusion. Forming a fourth metal layer containing a third metal, which is connected to the.

According to the method of the above configuration, the barrier metal layer (third metal layer) of the Schottky barrier electrode is formed by thermal diffusion to the surface region of the semiconductor substrate via the first metal layer. By thus diffusing through the first metal layer, a highly reliable barrier metal layer in which contamination and the like are prevented can be obtained.

In the above structure, in the heat diffusion step,
At the same time that the third metal layer is formed, silicon contained in the semiconductor substrate may be diffused into the first metal layer. That is, by siliciding the first metal layer, the oxidation of the first metal layer, for example, the titanium layer in the processing step can be prevented, and the increase in electrical resistance due to the oxidation can be reduced. Further, the silicidation improves the adhesion between the first metal layer and the insulating film.

In order to achieve the above object, a semiconductor device according to a second aspect of the present invention is provided so as to contact one surface of a semiconductor substrate containing silicon, and a Schottky barrier is provided between the semiconductor element and the one surface. A semiconductor device having a Schottky barrier electrode to be formed, wherein:
A silicon-based insulating film having an opening, a first metal layer formed in a surface region of the semiconductor substrate and containing a silicide of a first metal, the first metal layer and the opening. A second metal layer formed on the insulating film so as to be in contact with each other and containing a second metal, and a second metal layer formed on the second metal layer and containing a third metal, the third metal layer being connected to an external electrode. A metal layer of No. 3 and the silicide of the first metal reacts between the first metal thermally diffused through the second metal layer and silicon contained in the semiconductor substrate. It is formed.

In the semiconductor device having the above structure, the barrier metal layer (first metal layer) of the Schottky barrier electrode is the second metal layer.
Is formed by thermal diffusion to the surface region of the semiconductor substrate through the metal layer of. By thus diffusing through the second metal layer, the barrier metal layer thus formed becomes highly reliable with prevention of contamination and the like.

In the above structure, the second metal layer is
It is desirable to include a silicide of the second metal formed by the reaction of the second metal with the silicon thermally diffused from the semiconductor substrate. That is, the second silicided
Is a second metal layer in the process step, for example,
It prevents oxidation of the titanium layer and reduces the increase in electrical resistance due to oxidation. Further, high adhesion between the second metal layer and the silicon-based insulating film can be obtained.

The second metal is composed of, for example, titanium. Titanium has good adhesion to the silicon-based film, and a highly reliable semiconductor element can be obtained. The first metal is composed of palladium, for example. Palladium provides a unique barrier height, but has low adhesion to silicon-based films. For this reason, as in the above-described structure, the semiconductor element is formed so as not to adhere to the insulating film, and is covered with the insulating film by, for example, the second metal layer made of titanium, so that the semiconductor element having high adhesiveness and higher reliability is obtained. Is obtained.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION A semiconductor device according to an embodiment of the present invention will be described below with reference to the drawings. In this embodiment, an example in which the present invention is applied to a Schottky barrier diode will be described.

FIG. 1 shows a sectional view of a semiconductor device 11 according to this embodiment. As shown in FIG. 1, the semiconductor device 1
Reference numeral 1 denotes a semiconductor substrate 12 and a Schottky barrier electrode 1 which is provided on one surface of the semiconductor substrate 12 and constitutes an anode electrode.
3 and the cathode electrode 14 provided on the other surface of the semiconductor substrate 12.

The semiconductor substrate 12 is formed of, for example, a substantially rectangular silicon single crystal substrate, and the N-type first semiconductor region 15 forming a surface of the semiconductor substrate 12 and having a relatively low impurity concentration, and the semiconductor substrate 12. And an N-type second semiconductor region 16 having a relatively high impurity concentration which constitutes the other surface. Here, the second semiconductor region 16 may be formed by epitaxial growth on the first semiconductor region 15 composed of a silicon single crystal substrate.

An insulating film 17 is formed on one surface of the semiconductor substrate 12. The insulating film 17 is made of a silicon-based film, for example, a silicon oxide film formed by thermal oxidation or the like. The insulating film 17 has a contact opening 18 formed substantially in the center of the semiconductor substrate 12 so that the first semiconductor region 15 is exposed inside thereof.

The Schottky barrier electrode 13 comprises a first metal layer 19, a second metal layer 20 and a third metal layer 21.

The first metal layer 19 is mainly composed of palladium (Pd) silicide. First metal layer 1
9 is formed in the surface region of the first semiconductor region 15 so as to be exposed in the contact opening 18. The first metal layer 19 is formed by thermal diffusion of Pd into the surface region of the silicon semiconductor substrate 12 (first semiconductor region 15) as described later.

The first metal layer 19 is electrically connected to the semiconductor substrate 12 and functions as a barrier metal layer forming a Schottky barrier at the interface with the surface of the semiconductor substrate 12. The barrier height of the Schottky barrier is adjusted to a desired value by adjusting the thickness of the first metal layer 19. The first metal layer 19 is provided with a thickness of, for example, about 20 nm. As described above, the first metal layer 19 is an extremely thin film and can be called a “diffusion region” containing palladium silicide.

The second metal layer 20 is mainly composed of titanium (Ti) silicide. Second metal layer 20
Is provided on one surface of the semiconductor substrate 12 including the surface of the insulating film 17 and the surface of the first metal layer 19 in the contact opening 18. The second metal layer 20 has contact openings 18
Is in contact with and electrically connected to the first metal layer 19.

The second metal layer 20 is provided to complement the low adhesion of the first metal layer 19 containing Pd to the silicon-based insulating film 17. The second metal layer 20 containing Ti has high adhesion to the metal film and the silicon-based film. The second metal layer 20 covers the surface of the first metal layer 19 and at least the surface of the insulating film around the first metal layer 19, and adheres to both surfaces with high adhesion.

The second metal layer 20 is formed by thermal diffusion of silicon (Si) contained in the semiconductor substrate 12 into the Ti layer, as described later. Here, the thermal diffusion is performed to the extent that the silicidation of the second metal layer 20 is possible even in the Ti layer on the insulating film 17.

The formation of the second metal layer 20 (formation of Ti silicide) is performed in the same heat treatment (thermal diffusion) process as the formation of the first metal layer 19 (formation of Pd silicide) described above. Specifically, the heat treatment is performed after the Pd layer is stacked on the Ti layer formed on the one surface of the semiconductor substrate 12.
At this time, Pd goes through the Ti layer toward the semiconductor substrate 12, while Si of the semiconductor substrate 12 goes toward the Ti layer. Thus, formation of silicide in the Ti layer (formation of the second metal layer 20) and formation of Pd silicide region in the surface region of the semiconductor substrate 12 (first metal layer 19).
Formation), and at the same time. Here, the second metal layer 20 after the heat treatment contains almost no Pd.

The third metal layer 21 is made of aluminum. The third metal layer 21 is formed on the second metal layer 20 by vacuum vapor deposition or the like. The third metal layer 21 is electrically connected to the semiconductor substrate 12 via the first metal layer 19 and the second metal layer 20. Ti forming the second metal layer 20
Although it has high adhesion to the silicon-based insulating film 17, it is not a material suitable for wire bonding. Third metal layer 2
1 is provided to complement this, and is formed of a material (aluminum) suitable for wire bonding. Terminals and the like are connected to the surface of the third metal layer 21 by wire bonding or the like. Here, the second metal layer 20 formed as Ti silicide has higher adhesion to the silicon-based film than the ordinary Ti layer.

As described above, the first to third metal layers 19 to 21
By stacking the layers, the Schottky barrier electrode 13 having a desired barrier height, high adhesiveness with the insulating film 17, and highly reliable bonding can be obtained. That is, even when Pd, which has low adhesion to the silicon-based film, is used, high adhesion to the semiconductor substrate 12 and the insulating film 17 of the entire Schottky barrier electrode 13 is obtained, and a highly reliable semiconductor suitable for wire bonding or the like. The element 11 is obtained.

The cathode electrode 14 is made of titanium, nickel,
It is composed by sequentially stacking palladium and silver. The cathode electrode 14 is formed on the second semiconductor region 16 by vacuum vapor deposition or the like. External electrode terminals and the like are soldered to the cathode electrode 14.

Hereinafter, a method of manufacturing the semiconductor element 11 of the present embodiment will be described with reference to FIGS. 2 (a) to 2 (d), 3 (e) and 3 (f).

First, N having a relatively low impurity concentration on one side is
A semiconductor substrate 12 including a type semiconductor region 15 and an N-type semiconductor region 16 having a relatively high impurity concentration on the other surface is prepared. Next, the insulating film 17 made of a silicon oxide film is formed on the other surface of the semiconductor substrate 12 by thermal oxidation or the like. The insulating film 17 is formed with a thickness of, for example, about 1 μm. Further, the insulating film 17 is patterned to form a contact opening 18 as shown in FIG.

Subsequently, as shown in FIG. 2B, a Ti layer 22 is formed on the other surface of the semiconductor substrate 12 including the insulating film 17 by vacuum vapor deposition or the like. The Ti layer 22 is, for example, 50
It is formed with a thickness of nm to 150 nm. Next, FIG. 2 (c)
As shown in, the Pd layer 23 is formed on the Ti layer 22 by vacuum deposition or the like. The Pd layer 23 has, for example, 500 nm or more.
It is provided with a thickness of about 1000 nm.

Subsequently, the semiconductor substrate 12 in which the Ti layer 22 and the Pd layer 23 are laminated is subjected to heat treatment at a temperature of about 600 ° C. for a time of about 40 minutes, for example. At this time, Pd diffuses from the Pd layer 23 on the Ti layer 22 to the surface region of the semiconductor substrate 12 through the Ti layer 22.
Pd is silicon (Si) in the surface region of the semiconductor substrate 12.
Reacting with Ti, which causes Ti in the contact opening 18 to react.
A Pd silicide layer (first metal layer 19) is formed between the layer 22 and the surface of the semiconductor substrate 12. At the same time, Si in the semiconductor substrate 12 diffuses into the Ti layer 22,
The Ti layer 22 changes to a Ti silicide layer (second metal layer 20). The width of the end of the insulating film 17 is set to be sufficiently small so that the Ti layer 22 is also silicidized at the end. However, the Ti layer 2 on the insulating film 17
On 0, the degree of silicidation is lower than that on the Ti layer 20 on the Pd silicide layer 19.

Here, in the heat treatment, almost the entire Pd layer 23 is diffused to the semiconductor substrate 12 side, and the Pd layer 2 on the Ti layer 22 is
3 is carried out such that 3 does not substantially remain. As a result of the heat treatment, as shown in FIG. 2D, the Pd layer 23 substantially disappears, and the Pd silicide layer (first metal layer 19) and the Ti silicide layer (first layer) are formed on the other surface of the semiconductor substrate 12. A state in which the two metal layers 20) are laminated is obtained. The Pd layer 23 may remain on the Ti layer 22 after the heat treatment.

Next, as shown in FIG. 3E, an Al layer is formed on the Ti silicide layer by vacuum vapor deposition or the like.
The Al layer (third metal layer 21) is provided with a thickness of, for example, about 1 μm. As described above, the Schottky barrier electrode 13 including the first metal layer 19 containing Pd silicide, the second metal layer 20 containing Ti silicide, and the third metal layer 21 containing Al is formed.

Next, on the other surface of the semiconductor substrate 12, for example, Ti, Ni, Pd and Ag are sequentially laminated by vacuum vapor deposition or the like. Thereby, the cathode electrode 14 is formed. The cathode electrode 14 may be formed before the Schottky barrier electrode 13 is formed. Above,
The manufacturing process ends, and the semiconductor element 11 shown in FIG. 3F is formed.

As described above, in the present embodiment,
The Pd layer 23 stacked on the Ti layer 22 is substantially entirely diffused downward by heat treatment, and a barrier metal layer (first metal layer) made of Pd silicide is formed on the surface region of the semiconductor substrate 12 below the Ti layer 22. 19) is formed.

Since the formation of the first metal layer 19 (formation of Pd silicide) is performed by a heat treatment, a complicated and easily deteriorated process such as a lift-off method using a resist or an ultrasonic peeling method using an ultrasonic wave. Is not necessary, and the barrier metal layer can be easily formed with high reliability.

The formation of the first metal layer 19 is performed by using Ti
This is done by thermal diffusion through the layer 22 into the semiconductor region. Therefore, the formation of the first metal layer 19 does not require etching treatment, planarization treatment, or the like, and can be performed in a short step with substantially no contamination due to etching residues or the like. Therefore, the semiconductor element 11 including the Schottky barrier electrode 13 can be easily manufactured with high reliability.

Further, the second metal layer 20 formed by siliciding the Ti layer 22 is the third metal layer 21 thereafter.
It is harder to oxidize than normal Ti when forming a film such as.
Therefore, increase in resistance and the like due to the formation of the oxide film can be prevented.

The present invention is not limited to the above embodiment, but various modifications and applications are possible. Hereinafter, modifications of the above-described embodiment applicable to the present invention will be described.

A so-called guard ring formed of a P-type semiconductor region may be provided in the N-type second semiconductor region 16. As a result, a high reverse breakdown voltage can be obtained by the depletion layer formed from the PN junction when the reverse voltage is applied.

In the above embodiment, the third metal layer 21 on which wire bonding or the like is performed is made of aluminum. However, the present invention is not limited to this, and other metal materials capable of favorably performing wire bonding or the like, such as AlCu, can be used.

In the above embodiment, the barrier metal layer (first
The metal layer 19) was configured as Pd silicide containing Pd. However, the metal material forming the barrier metal layer is not limited to this, and may be another metal material such as platinum, nickel, or cobalt. Also, in the above example,
Although Ti is used as the second metal layer 20, the present invention is not limited to this, and other metal materials such as vanadium, chromium, molybdenum, tantalum, and tungsten that have good adhesion to the silicon-based film may be used.

In the above embodiment, the N-type semiconductor substrate is used. However, the configuration is not limited to this, and a P-type semiconductor substrate may be used. Further, another semiconductor substrate such as silicon carbide or germanium containing silicon can be used.

Further, in the above embodiment, an example in which the present invention is applied to a Schottky barrier diode has been shown. However, needless to say, the present invention can be applied to the case where the Schottky diode is formed on the substrate as an element such as a field effect transistor, a constituent element of an LSI (Large Scale Integrated Circuit) or an imaging sensor, etc. Absent.

[0050]

As described above, according to the present invention,
Provided are a simple and highly reliable method for manufacturing a semiconductor device including a Schottky barrier electrode and a semiconductor device.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a semiconductor element according to an embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the semiconductor device shown in FIG.

FIG. 3 is a diagram showing a manufacturing process of the semiconductor device shown in FIG. 1;

FIG. 4 is a diagram showing a configuration of a conventional Schottky barrier electrode.

[Explanation of symbols]

11 Semiconductor element 12 Semiconductor substrate 13 Schottky barrier electrode 14 Cathode electrode 15 First semiconductor region 16 Second semiconductor region 17 Insulating film 18 Contact opening 19 First metal layer 20 Second metal layer 21 Third Metal Layer

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4M104 AA01 AA03 BB14 BB20 BB21                       BB22 BB23 CC03 DD78 DD83                       DD84 FF13 GG03 GG12

Claims (6)

[Claims] 1. A method of manufacturing a semiconductor device, comprising a Schottky barrier electrode which is provided in contact with one surface of a semiconductor substrate containing silicon and forms a Schottky barrier with the one surface of the semiconductor substrate. Forming a silicon-based insulating film having an opening on one surface of a semiconductor substrate; a first metal layer containing a first metal and a second metal layer containing a second metal on the insulating film; And a step of sequentially forming the second metal contained in the second metal layer into the surface region of the semiconductor substrate by thermal diffusion through the first metal layer, and through the opening. A thermal diffusion step of forming a third metal layer in contact with the first metal layer and containing a silicide of the second metal; and an external electrode connected to one surface of the semiconductor substrate after the thermal diffusion. Process for forming a fourth metal layer containing a third metal A method of manufacturing a semiconductor device, comprising: 2. The thermal diffusion step, wherein the silicon contained in the semiconductor substrate is diffused into the first metal layer at the same time when the third metal layer is formed. Of manufacturing a semiconductor device of. 3. A semiconductor device comprising a Schottky barrier electrode which is provided in contact with one surface of a semiconductor substrate containing silicon and forms a Schottky barrier with the one surface of the semiconductor substrate. A silicon-based insulating film having an opening, a first metal layer formed in a surface region of the semiconductor substrate and containing a silicide of a first metal, the first metal layer and the opening. A second metal layer that is formed on the insulating film and includes a second metal, and a third metal that is formed on the second metal layer and is in contact with the external electrode. And a third metal layer, wherein the silicide of the first metal reacts with the first metal thermally diffused through the second metal layer and silicon contained in the semiconductor substrate. Formed by Body element. 4. The second metal layer includes a silicide of a second metal formed by a reaction between silicon thermally diffused from the semiconductor substrate and the second metal. Item 5. The semiconductor device according to item 3. 5. The second metal comprises titanium.
The semiconductor device according to claim 3, wherein the semiconductor device is a semiconductor device. 6. The semiconductor device according to claim 3, wherein the first metal is composed of palladium.