JPH0121633B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to the structure of a high voltage semiconductor device, such as a planar bipolar power transistor.

(2) Description of conventional technology Power transistors are used in the field of power electronics, and their applications are expanding and demand is increasing, and higher performance is required (for example, Shunji Miura:・Power transistors with increasing speed and integration technology,” Electronics (Ohmsha), December 1979 issue (vol. 24, No.
14), pp. 1267-1279).

The applicant proposed a planar type high voltage semiconductor device having the structure shown in FIG. 1 in Japanese Patent Application No. 131320/1982. The proposed high-voltage semiconductor device is superior to previous devices in that it can minimize element dimensions and provide highly reliable characteristics. As shown in FIG. 1, this semiconductor device is, for example,
N ⁺ type semiconductor (silicon) substrate 1, N ^- type epitaxial growth layer 2, P type base region 3, N ⁺ emitter region 4, P type guard ring 5, N ⁺ type channel stopper 6, insulating layers 7, 7' , collector electrode 8,
Base electrode 9, emitter electrode 10, guard ring floating electrode 11, channel stopper 12 and P ⁺
It consists of mold contact regions 13 and 14. base region 3, emitter region 4, guard ring 5, channel stopper 6 and P ⁺ type contact region 13,
14 is produced in the epitaxially grown layer 2 by diffusion, and a guard ring 5 completely surrounds the base region 3 at a distance, with a channel stop 6 arranged outside it. The base electrode 9 is connected to a field plate 1 extending from the collector-base junction to the collector region 2, as shown in FIG.
5, and similarly the floating electrode 11 of the guard ring 5 extends from the outer periphery of the guard ring 5 in the direction of the channel stopper 6.
6. By forming such field plates 15 and 16, electric field concentration caused by the curvature of the junction can be alleviated. However, in the above-mentioned high voltage semiconductor device, the distance L between the outer periphery of the field plate of the base electrode 9 and the inner periphery of the guard ring 5 is typically 20 μm.
As described above, the effect of electric field relaxation by guard ring formation is not sufficient, and the voltage drop (breakdown voltage) of the semiconductor device
The improvement effect was not so great.

(3) Object of the Invention An object of the present invention is to enable a high voltage semiconductor device having the above-described structure to fully exhibit the electric field relaxation effect of the guard ring and to improve the voltage resistance.

(4) Structure of the invention In the electric field distribution on the silicon surface below the field plate of the base electrode, there is a peak of electric field intensity just below the outer periphery (edge) of the field plate.
In order to effectively alleviate this electric field with a guard ring, in the planar type high voltage semiconductor device having the above structure, the distance L between the outer periphery of the field plate of the base electrode and the inner periphery of the guard ring is set to 5 to 15 μm. That is, the semiconductor device according to the present invention includes: a semiconductor layer or region having one conductivity type; a base region of an opposite conductivity type selectively formed within the semiconductor layer or region; and a base region spaced apart from the base region. a guard ring region of opposite conductivity type disposed surrounding the semiconductor layer or region; an insulating layer disposed on the surface of the semiconductor layer or region; a PN in contact with the base region and between the base region and the semiconductor layer or region; a first conductive layer extending over the insulating layer beyond the junction; a PN in contact with the guard ring region and between the guard ring region and the semiconductor layer or region on the side opposite to the base region; a second conductive layer extending over the insulating layer beyond the junction; a distance between an outer peripheral edge of the first conductive layer and an inner peripheral edge of the guard ring region; is 5
This is a high voltage semiconductor device characterized by having a thickness of ~15 μm.

(5) Embodiments of the Invention A planar type high voltage semiconductor device having the structure shown in FIG.
It was manufactured as follows, except that the thickness and distance L were changed.

Semiconductor substrate 1...N ⁺ type, silicon single crystal Epitaxial layer 2...N ^- type, silicon single crystal growth layer, 45 μm thick Resistance value of epitaxial layer 2...10, 20 and 30
Ωcm Base region 3...P type, 5μm depth Emitter region 4...N ⁺ type, 3μm depth Guard ring 5...P type, 5μm depth Contact regions 13, 14...P ⁺ type, 2μm depth Field from base region end Distance to outer periphery of plate...80μm Channel stopper 6...N ⁺ type, 3μm depth Insulating layer 7...Silicon dioxide (SiO ₂ ) Thickness of insulating layer 7...1.0, 1.5 and 2.5μm Collector electrode 8...Nickel plating and solder Base electrode 9 , the emitter electrode 10, the floating electrode 11 of the guard ring, and the electrode 12 connected to the channel stopper...Aluminum (Al) Distance L from the outer periphery of the field plate 15 of the base electrode 9 to the inner periphery of the guard ring 5...0, 5,
10, 15, 20, 25 and 50 μm When the collector-base breakdown voltage of the semiconductor device thus manufactured was measured, the results shown in FIGS. 2 and 3 were obtained. In Figure 2, the resistance value is 20Ω.
In the case of epitaxial layer 2 with cm, insulating layer 7
It shows the relationship between the distance L from the outer periphery of the field plate to the inner periphery of the guard ring and the withstand voltage between the collector and base, depending on the thickness of the field plate.
It is clear that when the thickness is 15 μm, the withstand voltage is high regardless of the thickness of the insulating layer. In addition, the second
Lines A, B, and C in the figure represent cases where the thickness of the insulating layer (SiO ₂ layer) 7 is 1.0 μm, 2.0 μm, and 2.5 μm.

Furthermore, FIG. 3 shows the relationship between the distance L depending on the resistance value of the epitaxial layer and the breakdown voltage when the thickness of the insulating layer 7 is 1.5 μm. It is clear that the breakdown voltage is higher when the distance L is 5 to 15 μm for any epitaxial layer. Note that lines D, E, and F in Figure 3 indicate epitaxial layer resistance values of 10Ωcm, 20Ωcm, and 30Ωcm.
This is the case for cm.

The reason why the breakdown voltage changes depending on the distance L as shown in the above results is considered as follows. When a reverse voltage is applied between the collector and the base, the peak of the electric field intensity in the electric field distribution on the surface of the silicon (epitaxial layer) is at point A (Fig. 1) just below the outer periphery of the field plate 15 of the base electrode 9 and at the floating electrode of the guard ring 5. It is located at point B (FIG. 1) just below the outer periphery of the field plate 16 at 11. When the distance L is 20 μm or more, the peak at point A will be high as shown in FIG. 4A, and eventually breakdown will occur at point A. On the other hand, when the distance L is shorter than 5 μm,
As shown in FIG. 4B, the peak at point B becomes high, and breakdown will occur at point B. If the distance L is 5 to 15 μm, which is the case of the present invention, then the fourth
As shown in diagram C, the electric field strengths at points A and B become approximately the same value, so that the electric field strengths are equally divided, and the breakdown voltage (breakdown voltage) between the collector and base becomes the highest.

FIG. 5 shows a planar type high voltage semiconductor device according to another embodiment of the present invention. In this device, a P type guard ring 21, a P ⁺ type contact region 22 and its floating electrode 23 are added. The distance M (FIG. 5) between the outer circumference of the field plate 16 of the inner guard ring 5 and the inner circumference of the outer guard ring 21 is set to be the same as the distance L, 5 to 15 μm. By using two or more guard rings in this way, the withstand voltage can be further improved.

In the above-described high breakdown voltage semiconductor device, the base region is of P type, but it can also be of the opposite type, N type.

(6) Effects of the Invention As is clear from FIGS. 2 and 3, according to the present invention, by setting the distance between the outer periphery of the field plate of the base electrode and the inner periphery of the guard ring to 5 to 15 μm, the collector base Improved pressure resistance. Further, the structure of the present invention can be applied not only to the above-mentioned bipolar transistors but also to high voltage diodes with guard rings, high voltage MOS FETs, etc. to achieve high voltage resistance.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view of a planar high-voltage semiconductor device, and Figure 2 shows the epitaxial layer resistance value.
This is a diagram showing the relationship between the distance L and the collector-base breakdown voltage when the resistance is 20Ωcm.
FIG. 4A, FIG. 4B, and FIG. 4C are diagrams showing the electric field intensity peak in the electric field distribution. FIG. FIG. 2 is a schematic cross-sectional view of a planar type high voltage semiconductor device having two semiconductor devices. 1... Semiconductor substrate, 2... Epitaxial layer, 3...
Base region, 5... Guard ring, 7, 7'... Insulating layer, 8... Collector electrode, 9... Base electrode, 11...
Floating electrode, 15, 16...Field plate, 2
1... Guard ring.

Claims (1)

[Scope of Claims] 1. A semiconductor layer or region having one conductivity type, a base region of an opposite conductivity type selectively formed in the semiconductor layer or region, and a base region spaced apart from and surrounding the base region. a guard ring region of opposite conductivity type disposed; an insulating layer disposed on the surface of the semiconductor layer or region; in contact with the base region, forming a PN junction between the base region and the semiconductor layer or region; a first conductive layer extending over the insulating layer, contacting the guard ring region and forming a PN junction between the guard ring region and the semiconductor layer or region on a side opposite to the base region; a second conductive layer extending over and over the insulating layer, wherein a distance between an outer peripheral edge of the first conductive layer and an inner peripheral edge of the guard ring region is 5. A high voltage semiconductor device characterized by having a thickness of 15 μm to 15 μm.