JPH01272158A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device having a small leakage current and a short turn-off period with low degree of irregularity by a method wherein a buried region having the conductivity reverse to an anode region is provided at the position opposing to the cathode region in an anode region. CONSTITUTION:A thyristor 1 is equipped with an anode region 2 provided on the rear surface of a semiconductor substrate 1a, a cathode region 4 provided on the surface, and a gate region 5, and a high specific resistance region 3 to be used as a current path, is provided between the anode region 2 and the cathode region 4. On the thyristor 1, a buried region 6 with which the life of a charged carrier (a hole in this case) is provided on the position opposite to the cathode region 4 in the anode region 2. The buried region 6 in the impurity region of the conductivity reverse to that of the anode region 2. As a result, a hole is instantaneously vanished by the above-mentioned buried region 6 without increasing a leakage current, and the region 6 works to shorten the turn-off period. Moreover, as the density of impurities is in an excellently uniform state, the degree of irregularity in the turn-off period is small.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor device and its manufacturing method [Prior Art] As a semiconductor device, an anode, such as a static induction silice or an insulated gate bipolar transistor (IGBT), A high resistivity region of the opposite conductivity type to the anode region is provided between the region and the cathode region, and the current flowing through the high resistivity region is controlled according to the voltage applied to the gate electrode, so that both electrons and the genuine tag There are devices in which charge carriers serve as carriers. For example, an electrostatic induction cyrisk has a configuration as shown in FIG.

The electrostatic induction thyristor 20 includes a high resistivity region (base region) 22 between an anode region 21 and a cathode region 23, and a gate region 24 near the cathode region 23. Of course, each region 21, 23, 24 has an electrode 21'
, 23', and 24' are provided, respectively. This electrostatic induction thyristor 20 has the characteristics of high current density, low forward voltage drop (on resistance), and short turn-on time. However, when shutting off, the holes injected from the anode side are not instantaneously cut off, so the turn-off time is shortened, for example, when the MOS F E
There is a problem that it is longer than T, etc. (usually about several μs to several tens of μs).

Conventionally, in order to shorten the turn-off time, electron beams or protons are irradiated into the high resistivity region to form a lattice defect region, or heavy metals such as gold or platinum are diffused to form a lifetime killer region. things are being done. The lattice defect region and lifetime killer region immediately annihilate holes injected from the anode side at turn-off.
Turn-off time becomes shorter.

[Problem to be solved by the invention]

However, the formation of the lattice defect region and the if-time killer region are accompanied by a decrease in the performance of the semiconductor device, such as an increase in reverse leakage current.

Moreover, in the formation of lattice defect regions by electron beam or proton irradiation and the formation of lifetime killer regions by heavy metal diffusion, it is difficult to keep the defect concentration and heavy metal concentration constant, so the turn-off time varies widely.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a semiconductor device having a low leakage current and a short turn-off time with little variation, and a method for manufacturing the same.

[Means to solve the problem]

In order to solve the above problem, a semiconductor device according to a first aspect of the present invention includes an anode region on one side of the semiconductor substrate, a cathode region on the other side, and a high resistivity region between the circular regions that serves as a current path. In the structure, a buried region of a conductivity type opposite to that of the anode region is provided at a position facing the cathode region in the anode region.

In the method for manufacturing a semiconductor device according to claim 2, a semiconductor substrate having a thickness of a part of the total thickness of the anode region is used,
The method includes a step of forming an impurity region of the opposite conductivity type in a portion facing the cathode region, and then laminating the remaining thickness of the anode region.

[For production]

In the semiconductor device according to claim 1, in the anode region,
There is a buried region of the opposite conductivity type in a position opposite to the cathode region where many charge carriers (for example, holes) remain during turn-off, and during turn-off, the buried region effectively recombines the holes in the anode region. As a result, the holes disappear in an extremely short period of time. Furthermore, there is no lattice defect region or heavy metal diffusion region in the substrate that would cause an increase in leakage current, and there is only a buried impurity region of the opposite conductivity type that allows for precise control of impurity concentration.

In the invention according to claim 2, an impurity region of an opposite conductivity type is formed in a portion of the substrate having a part of the total thickness of the anode region facing the cathode region, and then a part of the remaining thickness of the anode region is formed. The parts are laminated. The impurity region is buried by the remaining thickness of the stack, so that a buried region is formed in the anode region.

The buried region is formed by impurity diffusion and semiconductor layer stacking (
This is a process that is extremely commonly used in the manufacturing of semiconductor devices, such as epitaxial growth (e.g., epitaxial growth), and it is easier to control the impurity concentration in the impurity diffusion region than to control the lattice defect density or heavy metal concentration. .

Furthermore, in the invention as claimed in claim 2, the impurity diffusion for forming the buried region is shallow and the diffusion time is short, because the impurity region is buried in 81 layers of the remaining thickness of the anode region. When the diffusion time is short, there are fewer variations in the completed impurity region itself than when the diffusion time is long. The dimensions and impurity concentrations of the regions are well matched.

〔Example〕

Hereinafter, the semiconductor device and its manufacturing method according to the present invention will be described.
One embodiment of the invention will be described in the order of the apparatus and the manufacturing method, with reference to the accompanying drawings.

FIG. 1 shows an electrostatic induction thyristor (hereinafter referred to as "thyristor") which is an example of a semiconductor device according to a first aspect of the present invention.

The thyristor 1 includes an anode region 2 provided on the back surface (-example) of a semiconductor substrate 1a, and a surface (other side) of the substrate 1a.
A cathode region 4 and a gate region 5 are provided. A high resistivity region 3 serving as a current path is provided between the anode region 2 and the cathode region 4. It goes without saying that this high resistivity region (also referred to as a base region) 3 may be an intrinsic semiconductor layer. Anode area 2
, an anode electrode 2' is provided in the cathode region 4, a cathode electrode 4' is provided in the cathode region 4, and a gate electrode 5' is provided in the gate region 5, respectively. In this thyristor 1, the high resistivity region 3 is controlled (so-called conduction modulation) by adjusting the voltage applied to the gate electrode 5' to conduct conduction/cutoff operations. A buried region 6 that shortens the lifetime (in case of holes) is provided at a position opposite to the cathode region 4 in the anode region 2 . The buried region 6 is an impurity region of a conductivity type opposite to that of the anode region 2. Therefore, as described above, the buried region 6 acts to instantly eliminate holes and shorten the turn-off time without increasing leakage current. Moreover, since the impurity concentration is well kept constant, there is little variation in the turn-off time.

Next, a description will be given of the production of SIRISK according to an example of the method for producing a semiconductor device according to the second aspect.

First, as shown in FIG. 2(a), a semiconductor substrate 10 having an N- layer on a P layer is prepared. Pffi is the thickness of a portion of the anode region. On the other hand, the N- layer becomes a high resistivity region, and of course, a gate region and a cathode region are formed therein. According to the second aspect of the invention, the semiconductor substrate is manufactured using a semiconductor substrate having a thickness that is a part of the total thickness of the anode region.

Next, a mask (not shown) is provided on the surface of the N- layer and impurities are selectively diffused to form a gate region 5 as shown in FIG. 2(b). After the formation of the gate region 5, as shown in FIG. A window 14 is formed in the film for diffusing impurities for forming a buried region.The window 14 is formed directly below the window 12.
A mask 11 with a window 14 and a mask 13 with a window 14 are formed.

After forming masks 11 and 13, N-type impurities are implanted and diffused. Then, as shown in Figure 2 (C1), N
A type impurity region is formed. N' region cathode region 4 formed in the window 2, and N" region 6 formed in the window 14.
' becomes the embedding area. The N area 6' is located exactly opposite the cathode area 4. This is because the window 14 was directly below the window 12.

After removing the mask 13 on the back surface by etching, P''N is deposited on the P layer at a concentration of C5tlB = 10'' or more. Then, as shown in FIG. 2(d), the anode region 2 and the buried region 6 are completed.

Finally, each electrode is formed to complete the thyristor, similar to the thyristor 1 shown in FIG. 1.

In this way, it is possible to create a cyrisk with the advantages mentioned above.

In the example of the manufacturing method described above, the steps up to forming a resist on both 5ins films to cover areas other than the areas where the windows 12.14 are bright when forming the mask 11.13 are performed in separate operations. After that, the 5iOi film was etched to form the window 1.
Opening the window 2.14 and forming an impurity region in the window 12.14 can be performed at the same time. Therefore, the only additional work required is the work of providing a patterned resist for forming the mask 13 on the surface of the P layer and the work of epitaxially growing the P+ layer.

In addition, in FIG. 1 and FIG. 2(d), for convenience, the entire anode region 2 is represented as P'' in the drawings, but strictly speaking, it is PJi near the high resistivity region 3. This is because a part of the thickness of the anode region 2 is made up of two layers.The reason why the part of the thickness formed before the anode region 2 is made into two layers with a slightly lower impurity concentration than the P' layer to be stacked later is to This is because if the impurity concentration is too high in PM, even if N-type impurities are diffused, a large amount will be canceled out by P-type impurities, making it difficult to change the N+ region.

Of course, a portion of the thickness of the anode region formed first is P
Conversely, the remaining portion of the anode region to be deposited later may be PM.

This invention is not limited to the above embodiments. For example, the thyristor may not be of the surface gate type as shown in FIG. 1, but may have another structure such as a so-called buried gate type.

The semiconductor device may also be another type of semiconductor device such as an insulated gate bipolar transistor. Note that in the case of a transistor, the cathode region is usually the source region,
The anode region is called the drain region.

〔Effect of the invention〕

The semiconductor device according to the first aspect described above has the following effects.

During the turn-off operation, there is a buried layer of the opposite conductivity type in a position opposite to the cathode region where many charge carriers remain, and this buried layer promotes the recombination of charge carriers and instantly eliminates them, so the turn-off time is shortened. is short.

There are no lattice defect regions or lifetime killer regions, so leakage current is low.

Since the impurity concentration in the buried region is relatively well aligned, there is little variation in turn-off time.

The invention according to claim 2 provides the following effects in addition to being able to obtain a semiconductor device having the above effects.

The manufacturing of the semiconductor device is easy because the steps required to form the buried region are those commonly used in semiconductor manufacturing, such as diffusion of impurities and lamination of semiconductor layers.

Since the impurity diffusion when forming the buried region is only performed shallowly, there is little variation in the buried region itself, and the
Variations in turn-off time are reduced.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a thyristor as an example of a semiconductor device according to the invention as claimed in claim 1, and FIGS. FIG. 3 is a vertical cross-sectional view showing the basic structure of a thyristor in the order of steps during manufacturing according to an example. ■...Sirisk (semiconductor device) la...Semiconductor substrate 2...Anode region 3...High resistivity region 4...Cathode region 6...Buried region
lO... Semiconductor substrate having a part of the total thickness of the anode region Patent attorney Takehiko Matsumoto Figure 2 (b) Figure 2 (C) (d)

Claims (1)

[Scope of Claims] 1. A semiconductor device comprising an anode region on one side of a semiconductor substrate, a cathode region on the other side, and a high resistivity region serving as a current path between the two regions. A semiconductor device characterized in that a buried region of a conductivity type opposite to that of the anode region is provided at a position facing the cathode region. 2. In a method for manufacturing a semiconductor device comprising an anode region on one side of a semiconductor substrate, a cathode region on the other side, and a high resistivity region serving as a current path between the two regions, the total thickness of the anode region using a semiconductor substrate having a thickness of a part of the thickness, forming an impurity region of an opposite conductivity type in a portion facing the cathode region, and then laminating the remaining thickness of the anode region. A manufacturing method for semiconductor devices.