JP3312040B2 - Semiconductor device manufacturing method - Google Patents

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. More specifically, the present invention relates to a method of manufacturing a semiconductor device in which a polysilicon film is interposed between a semiconductor region and a metal wiring film for an electrode in order to expand a safe operation region by adjusting a resistance value of an electrode contact.

[0002]

2. Description of the Related Art A semiconductor substrate has an n-type region and / or a p-type region.
A mold region is formed, a semiconductor circuit is formed, and a metal material for an electrode is attached to a semiconductor region that needs to be electrically connected from the outside in each of the n-type or p-type regions to form respective electrodes. A semiconductor device is configured.

[0003] For example, FIG. 6 is a sectional explanatory view of an npn bipolar transistor. In FIG. 6, impurities such as boron are diffused into an n-type silicon
A base region is formed with a mold region, and an impurity such as phosphorus is diffused into the base region 2 to form an emitter region 3 of an n-type region. Further, a surface protective film 4, for example, a silicon dioxide film, which is a surface protective film of the semiconductor substrate 1, is formed on the entire surface, and the protective films 4 at the electrode formation locations of the base region 2 and the emitter region 3 are cut out to form contact holes 5, 6. , An electrode material such as aluminum is formed on the entire surface by sputtering or the like, a wiring pattern is formed on the protective film 4 by etching, and the contact holes 5 and 6 are directly covered with aluminum on the base region 2 and the emitter region 3 respectively. The base electrode 7 and the emitter electrode 8 are formed by being attached. The n-type semiconductor crystal layer of the semiconductor substrate 1 operates as a collector region, and a metal material such as gold is applied to the back surface of the semiconductor substrate 1 to form a collector electrode 9.

In addition, in the case of an IC or the like, if aluminum as an electrode material is directly formed on a semiconductor region, contact resistance increases due to imperfect contact due to a difference in material, which causes deterioration of characteristics. In order to reduce the density, a method of forming a semiconductor region at an electrode formation location partially in a high-concentration region is generally adopted.

[0005]

On the other hand, in a semiconductor device such as a bipolar IC, on the other hand, since the diffusion depth is generally shallow, the base resistance and the emitter resistance are small, and there is no portion acting as a ballast resistance. There is a problem that the current is easily concentrated, the safe operation area (hereinafter, referred to as ASO) is narrow, and the breakdown strength is weak.

In order to widen the ASO and improve the breakdown strength, a semiconductor film is provided between a semiconductor region and a metal wiring film for an electrode, and a semiconductor film which functions as a ballast resistor by introducing impurities into the polysilicon film. A device has been separately proposed by the inventor. However, this electrode contact is often formed in both different conductivity types (n-type region and p-type region), such as a base region and an emitter region of a transistor. In this case, since different impurities have to be introduced, the opposite sides must be masked and diffusion or ion implantation must be performed, resulting in a problem that the number of manufacturing steps increases and the cost increases.

According to the present invention, the polysilicon film functioning as a ballast resistor is interposed between the semiconductor region and the metal wiring film for the electrode without significantly increasing the manufacturing cost. It is an object of the present invention to provide a method for manufacturing a semiconductor device.

[0008]

According to a method of manufacturing a semiconductor device according to the present invention, a first conductivity type region serving as a base region and a second conductivity type region serving as an emitter region are formed by diffusing impurities into a semiconductor substrate. forming semiconductor regions, respectively, the protective film formed on the surface of the semiconductor substrate, forming a contact hole exposing a portion of the base region and the emitter region, said base region and exposed by the contact hole Forming a polysilicon electrode film on the emitter region, and performing heat treatment to remove impurities in the base region and the emitter region from the polysilicon electrode film on the base region and the polysilicon electrode on the emitter region.
Step diffused simultaneously into the respective electrode film, and consists step of forming an electrode metal wiring layer on the polysilicon electrode film, so that the resistance of the polysilicon electrode film becomes a predetermined resistance value that acts as a ballast resistor In addition, the impurity concentration of the base region and the emitter region and the conditions of the diffusion step are set.

[0009]

According to the present invention, since the impurity introduced into the semiconductor region is diffused as an impurity source into the polysilicon electrode film formed on the semiconductor region, the p-type region and the n-type region are mixed. Even if each electrode is formed at a location, a polysilicon electrode film is formed in one step, and impurities can be diffused into the polysilicon electrode films of all the electrodes by a single heat treatment. , A polysilicon electrode film having an arbitrary resistance value can be formed.

Further, the impurity concentration of the semiconductor region is usually set at 10 ¹⁸
/ Cm ³ to than smaller rather formed Kashii flame, but according to the method of the present invention, since the impurity semiconductor region is despread into the polysilicon film, the impurity concentration of the semiconductor region small no longer, improving the ASO it can.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the drawings. 1 to 5 are explanatory views showing a cross-sectional structure of each manufacturing process of a bipolar npn transistor according to one embodiment of the present invention.

First, as shown in FIG. 1, n-type and p-type semiconductor regions are formed on a semiconductor substrate 1. That is, an impurity such as boron is diffused into the silicon semiconductor substrate 1 to be an n-type collector region to form a p-type region to be a base region 2. Further, an impurity such as phosphorus is diffused into the p-type region to form an n-type region, and an emitter region 3 is formed.

As a specific example, a protective film 12 such as a silicon oxide film is formed on the surface of the semiconductor substrate 1, and the protective film 12 where the base region 2 is to be formed is cut out to form boron trichloride (BCl ₃ ).
In a gas atmosphere, a heat treatment at about 1100 ° C. is performed for about 120 minutes to diffuse boron, thereby forming a p-type region to be the base region 2. Further, a protective film is formed on the surface, and the protective film at the place where the emitter region is formed is cut out.
Under atmosphere of Cl _3), a heat treatment at about 1000 ° C. to about
The process was performed for 40 minutes to diffuse phosphorus to form an n-type region to be the emitter region 3.

Next, as shown in FIG. 2, contact holes 5 and 6 are formed at the locations where the electrode films are to be formed. As a specific example,
The protective film 4 such as a silicon oxide film was formed again on the surface of the semiconductor substrate 1, masked with a photoresist, and etched by a photolithography process to form contact holes 5 and 6.

Next, a polysilicon film is formed on the entire surface of the semiconductor substrate 1, and polysilicon electrode films 10 and 11 are formed by patterning. As a specific example, a polysilicon film having a thickness of about 1 μm is deposited on the entire surface of the semiconductor substrate 1 by performing a heat treatment at about 700 ° C. for about 30 minutes under monosilane (SiH ₄ ) and nitrogen gas. . This polysilicon film is etched using a photoresist as a mask, leaving the polysilicon film only at the electrode formation location and removing other unnecessary portions, thereby forming a polysilicon electrode film as shown in FIG.
10, 11 were formed.

Next, the semiconductor substrate 1 is heat-treated,
Impurities are diffused into the polysilicon electrode films 10 and 11 from the lower semiconductor region. As a specific example, a heat treatment is performed at about 1000 ° C. for about 30 minutes, so that boron as an impurity from the base region 2 becomes the polysilicon electrode film 10 and phosphorus as an impurity from the emitter region 3 becomes polysilicon as shown in FIG. Electrode film
Back-diffused to 11. As a result, the p-type impurity of boron diffuses into the polysilicon electrode film 10 to a concentration of about 10 ¹⁸ / cm ³ to have a specific resistance of 0.1 Ω · cm, while the n-type impurity of phosphorus Diffuses to a concentration of about 10 ²⁰ / cm ³ , reaching a specific resistance of about 10 ⁻³ Ω · cm.

Next, an electrode metal wiring film is formed on the polysilicon electrode films 10 and 11. As a specific example, aluminum was deposited on the entire surface of the semiconductor substrate 1 by a sputtering method, masked and etched, and a base electrode 7 and an emitter electrode 8 were formed except for a portion required as a wiring film. Similarly, an aluminum metal film was formed on the back surface of the semiconductor substrate 1 to form a collector electrode 9.

When the impurity in the semiconductor region is back-diffused into the polysilicon electrode film, the concentration of the polysilicon film can be adjusted by the impurity concentration of the semiconductor region, the diffusion temperature and the diffusion time, and the resistance value can be adjusted. That is, the specific resistance is
In order to form a p-type polysilicon film of about 0.1 Ω · cm with a thickness of 1 μm, the impurity concentration of the semiconductor region is set to 5 × 10 ¹⁸ / cm.
formed in cm ³ position, are example by a heat treatment at about 1000 ° C. for about 30 minutes, also, the n-type polysilicon film resistivity 10 ^-3 Ω · cm position to form a thickness of 1μm Can be obtained by forming the impurity concentration of the semiconductor region at about 10 ²¹ / cm ³ and performing a heat treatment at about 1000 ° C. for about 30 minutes.

Further, in the above-described embodiment, an example of an npn transistor has been described. However, the same applies to a pnp transistor. In the above-described embodiment, a polysilicon electrode film is formed on both the emitter electrode and the base electrode. As described above, the present invention is effective even when the polysilicon electrode film is formed only on one of the emitter and the base. Further, the present invention can be similarly applied to not only a transistor but also a part of each electrode of a diode or a semiconductor integrated circuit. In addition, although the introduction of impurities into the semiconductor region has been described by way of example of diffusion, it goes without saying that the same can be achieved by ion implantation.

[0020]

According to the present invention, a polysilicon electrode film is interposed between a semiconductor region and a metal for an electrode, and impurities in the polysilicon film are introduced by back diffusion from the semiconductor region to adjust the resistance value. Therefore, the semiconductor device can be formed easily and inexpensively with a small number of steps, and a semiconductor device in which the resistance value of the electrode portion is adjusted at low cost can be formed.

As a result, the polysilicon electrode film functions as a ballast resistor, the ASO is widened, and a high-performance semiconductor device resistant to destruction can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing a manufacturing process of an npn transistor portion of a semiconductor device according to one embodiment of the present invention.

FIG. 2 is an explanatory sectional view showing a manufacturing process of an npn transistor portion of the semiconductor device according to one embodiment of the present invention;

FIG. 3 is an explanatory sectional view showing a manufacturing process of an npn transistor portion of the semiconductor device according to one embodiment of the present invention;

FIG. 4 is an explanatory sectional view showing a manufacturing step of an npn transistor portion of the semiconductor device according to one embodiment of the present invention;

FIG. 5 is an explanatory sectional view showing a final manufacturing step of an npn transistor portion of the semiconductor device according to one embodiment of the present invention;

FIG. 6 is an explanatory sectional view of a conventional npn transistor portion.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2 base region (p-type region) 3 emitter region (n-type region) 4 protective film 5, 6 contact hole 7 base electrode 8 emitter electrode 10, 11 polysilicon electrode film

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/311 H01L 21/28 301 H01L 29/732

Claims (1)

(57) [Claims] An impurity is diffused into a semiconductor substrate.
Forming a semiconductor region of a second conductivity type region to the first conductivity type region and the emitter region to more base region, respectively, the protective film formed on the surface of the semiconductor substrate, a part of the base region and the emitter region Forming a polysilicon electrode film on the base region and the emitter region exposed by the contact hole; and removing impurities of the base region and the emitter region by heat treatment to form a polysilicon on the base region. Silicon electrode film and the above
A step of simultaneously diffusing each of the polysilicon electrode films on the emitter region and a step of forming a metal wiring film for an electrode on the polysilicon electrode film, wherein the resistance of the polysilicon electrode film is ballasted. A method of manufacturing a semiconductor device, wherein an impurity concentration of the base region and the emitter region and a condition of the diffusion step are set so as to have a predetermined resistance value acting as a resistance.