JP2008021723A - Manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of diffusing platinum in a semiconductor device. <P>SOLUTION: After a platinum film is deposited on a surface of a silicon substrate, a low temperature heat treatment process are activated at 300-500°C to form a platinum silicide (PtSi) film. Thereafter, the Pt film is removed, and Pt diffusion is activated by the PtSi film at a high temperature in a range of 800-1,000°C. The Pt film is removed after the low temperature heat treatment, whereby a diffusion temperature can be raised and high-speed switching characteristics can be improved. As a Pt concentration to an oxide film or the like on the surface of the silicon substrate can be reduced compared with a conventional method, a good withstand voltage yield ratio can be achieved with good repeatability. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device, which can stabilize mass-proof characteristics and can be mass-produced at low cost, and more particularly to a method for diffusing platinum into a silicon substrate.

  As a lifetime killer to be introduced into a semiconductor device, it is known that platinum is superior to gold in terms of softness of reverse leakage current and current change at the time of reverse recovery.

  As a method of performing platinum diffusion in the conventional manufacturing process of a semiconductor device, as shown in FIG. 3, a Pt vapor deposition film is formed on the surface of a silicon wafer, and heat treatment at a high temperature (800 ° C. to 1000 ° C.) is performed. The platinum was diffused sufficiently uniformly.

  Power diodes are also used for high frequencies and are required to shorten the reverse recovery time. There is Patent Document 1 as a technical document regarding improvement of reverse recovery time of a diode.

  Patent Document 1 (paragraph 0004) has the following description. “Lifetime control of minority carriers using heavy metal diffusion and electron beam irradiation is widely used to improve reverse recovery time of diodes”, “Reverse recovery time, reverse recovery current and reverse recovery charge are reduced. Thus, reverse recovery loss can be reduced. "

  The minority carrier lifetime control electron beam irradiation has the disadvantage of requiring high capital investment.

  Since the reverse recovery time is long in the conventional 3 μS, there is a disadvantage that switching cannot be performed at a required 50 kHz or higher.

Japanese Patent Laid-Open No. 2003-163357. “Semiconductor Device and Manufacturing Method Thereof”

Although there are drawbacks that require investment such as electron beam irradiation equipment, it is a challenge to establish a power device manufacturing method with a short reverse recovery time that can be completed and provided by an inexpensive method. Thus, the breakdown voltage characteristic is stabilized. A semiconductor device that includes a step of diffusing platinum into a silicon substrate as a lifetime killer for achieving high speed, in addition to a semiconductor device that can be manufactured at low cost with stable withstand voltage characteristics during mass production. The present invention relates to a manufacturing method invention.

In order to solve the above-mentioned problem, as a lifetime killer, instead of the method of diffusing gold by electron beam irradiation, Pt is deposited on the silicon surface by vapor deposition or the like, and heat-treated at a high temperature of about 900 ° C. Pt was diffused into a layer in which a low concentration N-type silicon layer was grown on a concentration N-type silicon substrate. In this conventional method, high-concentration Pt is diffused into the oxide film, which is an insulating film on the silicon surface. After Pt diffusion, the device was completed through a process of peeling Pt on the surface and a process of forming a metal electrode after the peeling process. When the temperature of Pt diffusion was increased, there was a defect that Pt peeling could not be performed thereafter.
The semiconductor device of the present invention was manufactured as described below. A low-temperature heat treatment process for forming a platinum silicide (PtSi) film on the silicon surface, a Pt diffusion process in the silicon by the platinum silicide (PtSi) film, and a Pt concentration in the oxide film as an insulating film is reduced by this manufacturing method. As a result, the breakdown voltage characteristics can be stabilized.

Regarding claim 1,
Step A for depositing a platinum film on the surface of the silicon substrate, Step B for forming a platinum silicide (PtSi) film on the surface of the silicon substrate, Step B for removing the Pt film remaining on the surface of the silicon substrate after the heat treatment step B The semiconductor device manufacturing method includes a high-temperature heat treatment step D in which Pt is diffused into a silicon substrate by a C, PtSi film.

Regarding claim 2,
The temperature of the low-temperature heat treatment step B is 300 ° C to 500 ° C.

Regarding claim 3,
The semiconductor device manufacturing method is characterized in that the temperature of the Pt diffusion step at a high temperature is 800 to 1000 ° C.

Regarding claim 4,
A step of forming an N− type second semiconductor layer on the upper surface of the N + type semiconductor substrate (first semiconductor layer), and a portion where an oxide film is formed on the surface of the second semiconductor layer and the oxide film is selectively removed. , Forming an anode region of a P layer (third semiconductor layer) in the second semiconductor layer by impurity diffusion, a first main electrode on the surface of the anode region, and a second main on the lower surface of the semiconductor substrate (first semiconductor layer). In the middle of the step of forming the anode region and the step of forming the first main electrode and the second main electrode, a platinum film is deposited on the upper surface of the semiconductor substrate and subjected to low-temperature heat treatment. A method of manufacturing a semiconductor device is provided, which includes a step of forming a platinum silicide (PtSi) film, removing the remaining Pt film, and diffusing Pt into the silicon substrate at a high temperature by the PtSi film.

A substrate in which a platinum film is deposited on an upper surface of a semiconductor substrate has a functional region, and an oxide film (insulating layer) is formed at the uppermost portion. Although a small amount of Pt diffuses into this oxide film, the amount of Pt diffused into the oxide film when Pt is diffused from a Pt vapor deposition film is extremely large, not the conventional platinum silicide (PtSi) film. The cause of bad characteristics was inherent.

  The reverse recovery time of the device can be shortened from the conventional 3μS to 0.5μS without using the lifetime control process by electron beam irradiation, which required equipment costs, and the reverse recovery speed is 6 times faster. It was.

As described above, the power device of the present invention can be formed without increasing the cost with a performance that is six times faster than the conventional reverse recovery time. In this conventional method, high-concentration Pt is diffused into the oxide film, which is an insulating film on the silicon surface. The device was completed through a step of peeling Pt on the surface after Pt diffusion and a step of forming a metal electrode after the peeling step. When the temperature of Pt diffusion was raised, there was a defect that this Pt peeling was not possible, but this defect was eliminated.
The semiconductor device of the present invention was manufactured as described below. A low-temperature heat treatment process for forming a platinum silicide (PtSi) film on the silicon surface, a Pt diffusion process in the silicon by the platinum silicide (PtSi) film, and a Pt concentration in the oxide film as an insulating film is reduced by this manufacturing method. As a result, the breakdown voltage characteristics can be stabilized. Low diffusion heat treatment temperature contributes to resource saving and high industrial value.

  FIG. 1 is a cross-sectional view illustrating a semiconductor device according to an embodiment of the present invention in order of manufacturing steps. This will be described in comparison with the manufacturing process sectional view of the conventional semiconductor device of FIG. In the following description, the first conductivity type is N-type and the second conductivity type is P-type, but the reverse may be possible. First, in the conventional method of FIG. 3, a low-concentration first-conductivity-type second semiconductor layer 2 is formed on a first-conductivity-type (N-type) silicon substrate 1 and then selectively etched on the surface using an etching technique. After forming the grooves, a platinum film was formed by vapor deposition on the second conductive type (P type) third semiconductor layer 3 formed (step 1), and then at a high temperature of about 900 ° C. The first main electrode 19 and the second main electrode are diffused and injected into the second semiconductor layer (step 2). After this step, the platinum film remaining on the surface is peeled off (step 3). 20 was formed (step 4). When platinum is diffused in this process and platinum is implanted into the second semiconductor layer, a high concentration of Pt is diffused in the insulating oxide film, resulting in a defect in that a withstand voltage is poor.

The manufacturing method according to the present invention eliminates this drawback, and forms a platinum film by vapor deposition or the like in step A + B of FIG. 1 with respect to step 1 of FIG. A Pt silicide film was formed on the surface. As a result of finding a method for carrying out Pt diffusion using this Pt silicide film, it has been found that this is a manufacturing method in which high-concentration Pt is diffused into the insulating oxide film and the breakdown voltage characteristics are stable. Pt diffuses with Pt silicide at a high temperature (800 to 1000 ° C.). Since Pt was peeled before this treatment as in the past, Pt is not peeled after this, so the treatment temperature is increased to shorten the treatment time. As a result, the process was shortened and the cost was reduced.

4 is compared with the characteristic diagram of the conventional semiconductor device of FIG. 4, FIG. 2 shows the breakdown voltage characteristic diagram of the semiconductor device according to the embodiment of the present invention. The leakage current has changed (increased) due to a change (increase) in voltage until the vicinity of 600V in FIG. 4 showing the conventional characteristics, and a conventional breakdown has occurred in the vicinity of 600V. Compared to this, it was confirmed that there was no increased current fluctuation up to 600V and stable breakdown voltage characteristics.

  Since the present invention has succeeded in deriving a device manufacturing method that is six times faster than the reverse recovery time without the need to introduce the conventional lifetime control process (electron irradiation) disclosed in Patent Document 1, the semiconductor device The product cost was reduced. It contributes to energy and resource saving when manufacturing semiconductor devices, and has a high industrial contribution.

It is a manufacturing process sectional view of a semiconductor device concerning an example by the present invention. It is a characteristic view of the semiconductor device based on the Example by this invention. It is sectional drawing of the manufacturing process of the conventional semiconductor device. It is a characteristic view of the conventional semiconductor device.

Explanation of symbols

1 (High concentration) N-type semiconductor layer (first semiconductor layer)
2 (Low concentration) N-type semiconductor layer (second semiconductor layer)
3 (High concentration) P-type semiconductor layer (third semiconductor layer)
8 Anode electrode (first main electrode)
9 Cathode electrode (second main electrode)
10 Insulating film (oxide film)

Claims (4)

  Step A for depositing a platinum film on the surface of the silicon substrate, Step B for low-temperature treatment for forming a platinum silicide (PtSi) film on the surface of the silicon substrate, Step for removing the Pt film remaining on the surface of the silicon substrate after the heat treatment step B A method for manufacturing a semiconductor device, comprising a high-temperature heat treatment step D in which Pt is diffused into a silicon substrate by a C, PtSi film. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the temperature of the low-temperature heat treatment step B is 300 to 500.degree. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the temperature of the Pt diffusion step at a high temperature is 800 to 1000 [deg.] C. A step of forming an N− type second semiconductor layer on the upper surface of the N + type semiconductor substrate (first semiconductor layer), and a portion where an oxide film is formed on the surface of the second semiconductor layer and the oxide film is selectively removed. , Forming a P layer (third semiconductor layer) anode region in the second semiconductor layer by impurity diffusion, a first main electrode on the surface of the anode region, and a second main electrode on the lower surface of the semiconductor substrate (first semiconductor layer). In the middle of the step of forming the anode region and the step of forming the first main electrode and the second main electrode, a platinum film is deposited on the upper surface of the semiconductor substrate, and the platinum is formed by low-temperature heat treatment. 4. The semiconductor device according to claim 1, further comprising a step of forming a silicide (PtSi) film, removing the remaining Pt film, and diffusing Pt to the silicon substrate at a high temperature by the PtSi film. Production method.

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