JP2003068753A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor structure which can prevent concentration of the electric field at the corner part when a reverse bias is applied, and which has a small size and a large current capacity, and to provide a manufacturing method thereof. SOLUTION: Since the surface of a semiconductor substrate 30 is formed in a wave shape, a PN junction area is increased, and the current capacity can be drastically increased. Additionally, since the surface is formed in a wave shape, the concentration of the electric field disappears at the corner part of the PN junction when the reverse bias is applied, and it is possible to provide a extremely small mount structure capable of preventing deterioration of a breakdown voltage or breaking. Hereby, it is realized to provide a semiconductor device optimal for mounting a minute semiconductor chip, and a manufacturing method thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly to a semiconductor device and a method of manufacturing the same which can increase a junction area while keeping a chip area small.

[0002]

2. Description of the Related Art In a conventional semiconductor device, as shown in FIG. 10, a flat base region 72 and a flat emitter region 71 are provided on a semiconductor substrate 70 serving as a collector region, an aluminum film 73 is provided on the upper surface, and silicon oxide is provided on the peripheral edge. It had a structure covered with the film 75.

Between the collector region 70 and the base region 72, a depletion layer 74 uniformly spreads from the PN junction during reverse bias.

In this structure, in order to increase the area of the PN junction in order to improve the current capacity of the semiconductor device, it was necessary to increase the surface area of the semiconductor chip.
However, if the chip size is increased in order to increase the current capacity, the size of the final semiconductor device also increases, which is not suitable for miniaturization. Further, there has been a problem that the manufacturing cost also increases.

In order to solve the problem, a semiconductor device having a rectangular surface as shown in FIG. 6 has been developed by anisotropic etching. As a structure, as shown in FIG. 6A, a base region 52 and an emitter region 51 each having a rectangular surface are formed on a silicon substrate 50 serving as a collector region, and the surface of each region is covered with an aluminum film 53. Had a structure covered with a silicon oxide film 55.

At the time of reverse bias, the depletion layer 54 spreads between the collector region 50 and the base region 52.

Further, as shown in FIG. 6B, the rectangle is formed in a stripe shape or a lattice shape, and the emitter electrode 51a having a flat surface is formed on the rectangular surface (the stripe shape in the figure). And the base electrode 52a is formed.

By making the surface of this semiconductor device rectangular, the effective surface area is increased more than 1.5 times and the current capacity is proportionally 1.
It was possible to raise it by more than 5 times.

An embodiment of the method of manufacturing the semiconductor device will be described with reference to FIGS.

First step: See FIGS. 7A, 7B and 7C. First, as shown in FIG. 7A, a silicon substrate 50 prepared by previously doping silicon with phosphorus is prepared as a substrate.
A silicon oxide film 55 is formed on the surface, and etching is performed so that the silicon oxide film 55 remains at the peripheral edge of the silicon substrate 50. Further, a resist 56 is applied on the upper surface, exposed, and developed so as to remain in a stripe shape.

Next, as shown in FIG. 7B, anisotropic dry etching is performed using a CF type gas. At this time, the silicon substrate 50 not covered with the resist 56 is dry-etched to form a groove having a certain depth.

Next, as shown in FIG. 7C, the resist 56 remaining on the silicon substrate 50 on the substrate is removed.

Second step: See FIGS. 8A and 8B As shown in FIG. 8A, boron is diffused on the substrate by a diffusion method. At this time, since the silicon oxide film 55 also functions as a mask, the substrate 5 not covered with the oxide film 55 is used.
Boron is diffused on 0.

Then, as shown in FIG. 8B, a base region 52 is formed on the silicon substrate 50.

Third step: See FIGS. 9A, 9B and 9C. As shown in FIG. 9A, a silicon oxide film 57 is formed on a silicon substrate and etched as shown.

Subsequently, phosphorus is diffused on the silicon substrate. At this time, since the silicon oxide film 57 also functions as a mask, phosphorus is diffused on the substrate 50 not covered with the silicon oxide film 57.

Then, an emitter region 51 is formed as shown in FIG. 9 (B). At this time, etching is performed so as to leave the silicon oxide film 57 as illustrated.

Finally, as shown in FIG. 9C, the aluminum film 53 is fixed by using the sputtering method.

[0019]

However, there are still problems in the above-mentioned conventional semiconductor device and manufacturing method. This is because breakdown is likely to occur due to concentration of an electric field at a corner portion during reverse bias due to the substrate surface being rectangular. That is, in the junction surface having a rectangular cross-section, electric field concentration occurs in the corner portion, and when the applied voltage is increased, the corner portion reaches the critical electric field before the planar portion reaches the critical electric field, causing breakdown. , The withstand voltage becomes low, and it becomes vulnerable to damage.

[0020]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a one-conductivity type semiconductor substrate serving as a collector region having a corrugated surface and a shape corresponding to the corrugated shape. It is characterized by comprising a reverse conductivity type base region and a one conductivity type emitter region having a shape corresponding to the corrugated shape, and increasing a junction area of a PN junction formed by the collector region and the base region.

Also, anisotropically etching a semiconductor substrate of one conductivity type to form an uneven region, isotropically etching the semiconductor substrate to form the uneven region into a corrugated shape, and And a step of forming a corrugated base region by introducing an impurity of opposite conductivity type, and a step of forming a corrugated emitter region by introducing an impurity of one conductivity type into the base region. To do.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor device of the present invention will be described with reference to FIG. 1A is a cross-sectional view of the present invention, FIG.
(B) shows a top view of the present invention. As shown in FIG. 1A, a corrugated base region 32 and an emitter region 31 are provided on a silicon substrate 30 serving as a collector region,
An aluminum film 53 is provided in each region, and the peripheral edge is covered with a silicon oxide film 55.

Further, the silicon substrate 30 which becomes the collector region
A depletion layer 34 extends from the PN junction between the base region 32 and the base region 32 at the time of reverse bias.

The greatest feature of the present invention is that the upper surface of the silicon substrate 30, which is the collector region, that is, the portion in contact with the base region 32 is corrugated. As a result, a sufficient current capacity can be obtained as in the conventional P
It is possible to secure the junction area of the N junction, and further, the concentration of the electric field at the corner portion which occurs at the time of reverse bias can be avoided by the waveform shape of the PN junction.

Further, as shown in FIG. 1B, the corrugations are formed in a stripe shape or a lattice shape (not shown).

Further, the emitter electrode 31a and the base electrode 3
A flat portion is provided to form 2a.

An embodiment of the method of manufacturing a semiconductor device of the present invention will be described with reference to FIGS.

First step: See FIGS. 2A, 2B and 2C. As shown in FIG. 2A, first, a silicon substrate 30 serving as a collector region is prepared by previously doping silicon with phosphorus. A silicon oxide film 35 is formed on the upper surface, and etching is performed so that the silicon oxide film 35 remains on the peripheral edge of the silicon substrate 30. Further, a resist 36 is applied on the surface, exposed, and developed so as to remain in a stripe shape.

Next, as shown in FIG. 2B, anisotropic dry etching is performed using a CF type gas. At this time, the silicon substrate 30 not covered with the resist 36 is dry-etched to form a groove 37 having a certain depth.

Next, as shown in FIG. 2C, the resist 36 remaining on the silicon substrate 30 is removed.

Second step: See FIGS. 3A and 3B. Isotropic etching is performed as shown in FIG. 3A so that the angular portion is rounded. As the isotropic etching, a spin etching method is used. As is well known, in the spin etching method, a wafer is vacuum-sucked or mechanically chucked on a support and sprayed with a chemical solution while rotating to perform etching. By performing isotropic etching, it is possible to secure a junction area of the PN junction that can obtain a sufficient current capacity as in the case where the upper surface is rectangular, and at the time of reverse bias when the surface is rectangular. It can be possible to avoid it by making the corners rounded.

Then, as shown in FIG. 3B, the surface of the silicon substrate 30 which is uneven from the groove 37 has a corrugated shape.

Third step: See FIGS. 4A and 4B As shown in FIG. 4A, boron is diffused on the surface of the substrate by a diffusion method. At this time, since the silicon oxide film 35 at the peripheral edge functions as a mask, boron is diffused on the surface of the substrate 30 not covered with the oxide film 35.

As shown in FIG. 4B, the silicon substrate 30
A corrugated base region 32 is formed on the surface.

Fifth step: See FIGS. 5A, 5B, and 5C As shown in FIG. 5A, etching is performed so that the silicon oxide film 37 remains on the silicon substrate 30.

Subsequently, phosphorus is diffused on the silicon substrate 30. At this time, since the silicon oxide film 37 also functions as a mask, phosphorus is diffused on the substrate 30 which is not covered with the silicon oxide film 37.

Then, as shown in FIG. 5B, the emitter region 31 is formed on the surface of the base region 32. At this time, etching is performed so as to leave the silicon oxide film 37 as illustrated.

Finally, as shown in FIG. 5 (C), an aluminum film 33 is attached by a sputtering method to form a base electrode and an emitter electrode.

[0039]

According to the present invention, the surface area of the semiconductor device can be expanded without changing the chip size by making the surface of the semiconductor device into a wavy shape and the contact surface between the collector region and the base region also having a wavy shape. This makes it possible to significantly improve the current capacity.

Furthermore, when the surface of the semiconductor device is rectangular, the breakdown that has occurred at the time of reverse bias can be prevented by forming the surface in a wavy shape, and the breakdown voltage becomes low and it is vulnerable to breakage. It became possible to solve the problem of being lost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view (A) illustrating a semiconductor device of the present invention,
It is a top view (B).

FIG. 2 is a diagram illustrating a method for manufacturing a semiconductor device according to the present invention.

FIG. 3 is a diagram illustrating a method for manufacturing a semiconductor device according to the present invention.

FIG. 4 is a diagram illustrating a method for manufacturing a semiconductor device according to the present invention.

FIG. 5 is a diagram illustrating a method for manufacturing a semiconductor device of the present invention.

6A and 6B are a cross-sectional view (A) and a top view (B) illustrating a conventional semiconductor device.

FIG. 7 is a diagram illustrating a conventional method for manufacturing a semiconductor device.

FIG. 8 is a diagram illustrating a conventional method for manufacturing a semiconductor device.

FIG. 9 is a diagram illustrating a conventional method for manufacturing a semiconductor device.

FIG. 10 is a diagram illustrating a conventional semiconductor device.

Claims (7)

[Claims] 1. A one-conductivity-type semiconductor substrate having a corrugated collector surface, an opposite-conductivity-type base region having a shape corresponding to the corrugated shape, and one-conductivity-type emitter region having a shape corresponding to the corrugated shape. And increasing the junction area of the PN junction formed by the collector region and the base region. 2. The semiconductor device according to claim 1, wherein when the PN junction between the base region and the collector region is reverse biased, a depletion layer is uniformly spread along the corrugated shape. 3. The semiconductor device according to claim 1, wherein the corrugated shape is formed in a stripe shape. 4. The semiconductor device according to claim 1, wherein the corrugated shape is formed in a lattice shape. 5. The semiconductor device according to claim 1, wherein a flat extraction region is provided in the center of the corrugated shape. 6. A step of anisotropically etching a one-conductivity-type semiconductor substrate to be a collector region to form a concavo-convex region, and a step of isotropically etching the semiconductor substrate to form the corrugated region in the concavo-convex region. The method comprises the steps of introducing an impurity of opposite conductivity type into the semiconductor substrate to form a corrugated base region, and introducing an impurity of one conductivity type into the base region to form a corrugated emitter region. A method of manufacturing a semiconductor device, comprising: 7. The method of manufacturing a semiconductor device according to claim 6, wherein the impurity of the opposite conductivity type is introduced by diffusion.