JPH04206780A - Semiconductor device - Google Patents

Abstract

PURPOSE:To reduce an operating resistance by a method wherein a reverse conductive type first region is formed in one conductive type semiconductor layer and a reverse conductive type second region having high impurity density is formed in this first region. CONSTITUTION:A window is selectively opened in an oxidation film 2 on an N type semiconductor substrate 1, P type impurities are introduced from the surface of the N type semiconductor substrate 1 through this window, and a first P region 3 comprising a PN connection is formed. Thereafter, the oxidation film 2 is again formed, a window is opened in a central portion of the first P region 3, the P type impurities having high density are introduced into the first P region 3 through this window, and a second P region comprising a P<+>-connection, namely a P<+> region 4, is formed. At this time, the P<+> region 4 is formed so as to penetrate into the first P region 3 and reach an N type semiconductor, and the depth is made about slightly deeper than the first P region 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device including a planar PN junction diode, and particularly to a constant voltage diode with low operating resistance.

[Conventional technology]

An example of a conventional semiconductor device of this type is shown in the cross-sectional view of FIG. 5(a). As shown in the figure, a window is selectively formed in the oxide film 2 provided on the surface of the N-type semiconductor substrate 1, and a P-type impurity is introduced through the window to form a P-type head region 3B as a guard ring. Further, after forming an oxide film on the N-type semiconductor substrate 1 again, a high concentration of P is applied to the region surrounded by the P-type head region 3B.
A type impurity is introduced to form a P″ region 4B having a required breakdown voltage.Then, an anode electrode 5 is formed through a window of the oxide film 2.
A cathode electrode 6 is formed on the back surface of the semiconductor substrate 1.

The semiconductor device configured in this manner connects the anode electrode 5 and the cathode electrode 6 to an external circuit via a lead or the like,
And a predetermined sealing is performed.

Further, a conventional bidirectional voltage regulator diode has a configuration shown in FIG. 6, and parts corresponding to those in FIG. 5(a) are given the same reference numerals. Note that 5 is a front electrode, and 6 is a back electrode.

[Problem to be solved by the invention]

In a semiconductor device having such a configuration, when a voltage is applied in the opposite direction between the anode electrode 5 and the cathode electrode 6,
As shown in FIG. 5(b), a depletion layer 7B spreads on the PN junction surface, breakdown occurs at the portion A, and current flows. In this case, since the resistivity of the depletion layer 7B is higher than that of the N-type semiconductor substrate 1, the current is concentrated in the B portion. Therefore,! There was a problem with the characteristics that the resistance bones in the section became large and the movement resistance became large. In particular, in the case of a low-noise type voltage regulator diode, S in the figure is very small, so the influence is large.

This also applies to the bidirectional voltage regulator diode shown in FIG.

An object of the present invention is to provide a semiconductor device with reduced operating resistance.

[Means to solve the problem]

In the semiconductor device of the present invention, on the surface of a semiconductor layer of one conductivity type,
A first region of an opposite conductivity type is formed to constitute a PN junction, and a second region of an opposite conductivity type having a higher impurity concentration is formed within this first region.

In this case, the second region penetrates the first region and reaches the semiconductor layer of one conductivity type.

[Effect]

According to the present invention, the section of the depletion layer formed between the first region and the second region and the semiconductor substrate becomes narrower, and the current concentration region becomes narrower, thereby reducing the operating resistance.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1(a) is a sectional view of a first embodiment of the present invention. In the figure, a window is selectively opened in an oxide film 2 on an N-type semiconductor substrate 1, and P from the surface of the N-type semiconductor substrate 1 through this window.
A first P Si region 3 in which type impurities are introduced to form a PN junction that has a breakdown voltage higher than the target breakdown voltage.
form.

After that, an oxide film 2 is formed again, and the first P 91
A window is formed in the center of the region 3, and a high concentration of P-type impurity is introduced into the first P region 3 through this window to form a second P”-N junction with the desired breakdown voltage as the main junction. P
A Si region, that is, a P′ region 4 is formed. At this time, P
``region 4 is formed so as to penetrate through the first P region 3 and reach the N-type semiconductor region, but its depth is smaller than that of the first P region 3.
The structure is slightly deeper than the previous one.

Then, an anode electrode 5 is formed to be in contact with the P'' region 4 through the window, and a cathode electrode 6 is formed on the back surface of the N-type semiconductor substrate 1 to complete the diode.

According to the diode with this configuration, when a voltage is applied in the reverse direction, the depletion layer 7 expands as shown in FIG.
Breakdown occurs in some parts and current flows.

At this time, since the resistivity of the depletion layer 7 is high, the current is concentrated in the B portion. However, in this configuration, the depth of the P'' region 4 is slightly deeper than the depth of the first P region 3, so the section can be shortened compared to the conventional configuration. , it becomes possible to reduce the operating resistance by the amount that this ! section is shortened.

FIG. 2(a) is a cross-sectional view of a second embodiment of the present invention, and parts corresponding to the previous embodiment are given the same reference numerals. In this embodiment, the depth of the P+ region 4A is formed to be slightly shallower than the depth of the P region 3, forming a P-P-N junction.

According to this configuration, when a voltage in the opposite direction is applied between the anode electrode 5 and the cathode electrode 6, the depletion layer 7A expands as shown in FIG. flows. Even in this case compared to traditional pellets!
The section becomes shorter and the operating resistance becomes smaller. However, P″
The depth of the region 4A is P'', the depletion layer of the region 4A is P?TI
It is important to set it so that it exists within the depletion layer section (L section) of region 3.

Note that the pellet of the semiconductor device formed in this way is
For example, as shown in FIG. 3, a DHD type diode is constructed by placing the diode in a glass tube 11, applying slug leads 12a and 12b from both sides, and melting the glass tube by heating to airtightly seal it.

If the diode of the present invention is applied to a pellet with a main junction size of about 40 pieces φ, the operating resistance can be reduced by 20 to 30%.

FIG. 4 is a sectional view of a third embodiment in which the present invention is applied to a bidirectional voltage regulator diode.

In this embodiment, a window is formed in the oxide films 2a and 2b provided on both the front and back surfaces of the N-type semiconductor substrate 1, and the p85 region 3a, which uses this window to achieve a breakdown voltage higher than the target breakdown voltage, 3b is formed. Similarly, after opening a window in the oxide film, the P region 3a is formed.

Main junction P'' regions 4a and 4b are formed within 3b.

Then, electrodes 5 and 6 are formed on each surface to form a pellet of a semiconductor device.

According to this configuration, the same effects as in each of the embodiments described above can be obtained, and the pellet size is reduced by (,1,+12)" compared to the conventional bidirectional voltage regulator diode shown in FIG. Incidentally, if this embodiment is applied to a pellet with a pellet size of about 0.40 mm11, the pellet size can be reduced by about 20%.

The present invention can be similarly applied to a diode in which N-type first and second regions are formed on a P-type semiconductor substrate.

〔Effect of the invention〕

As explained above, the present invention forms a first region of an opposite conductivity type in a semiconductor layer of one conductivity type, and forms a second region of an opposite conductivity type with a high impurity concentration within this first region. Therefore, the section of the depletion layer formed between the first and second regions and the semiconductor substrate becomes narrower, and the range of current concentration becomes narrower, resulting in an effect that the operating resistance can be reduced.

[Brief explanation of the drawing]

FIG. 1(a) is a sectional view of the first embodiment of the present invention, and FIG. 1(b)
) is a diagram showing the state of the depletion layer at the time of reverse bias, and Figure 2 (
FIG. 3A is a cross-sectional view of the second embodiment of the present invention, FIG. The figure shows a sectional view of the third embodiment of the present invention, FIG. 5(a) is a sectional view of a conventional diode, FIG. FIG. 2 is a cross-sectional view of a bidirectional voltage regulator diode. 1... N-type semiconductor substrate, 2.2a, 2b... Oxide film, 3.3A, 3B... P region (first region), 4.4
A, 4B...P+ head region (second region), 5... Anode electrode (front electrode), 6... Cathode electrode (back electrode). Figure 3 Figure 4 Figure 6

Claims (1)

[Claims] 1. A first region of an opposite conductivity type is formed on the surface of a semiconductor layer of one conductivity type to constitute a PN junction, and an impurity concentration higher than that of the first region is formed in the first region. A semiconductor device characterized in that a second region of a highly opposite conductivity type is formed. 2. The semiconductor device according to claim 1, wherein the second region extends through the first region to reach the semiconductor layer of one conductivity type.