JPH0382080A - Bipolar type semiconductor switching device - Google Patents

Abstract

PURPOSE:To facilitate leading of a buried gate electrode and to simultaneously obtain a large capacity device having high electrical and mechanical long-term reliability accurately and easily by forming the leading of a buried gate substantially on the same plane as that of at least one main electrode formed in a mesa shape. CONSTITUTION:In a bipolar type semiconductor switching device in which first and second main electrodes 7, 8 are formed on both main surfaces through semiconductor substrates 1, 2 to become main current paths, and having buried gate electrode regions 3, 4 for controlling ON, OFF of a main current in the substrates near at least one main electrode, the leading 19 of the buried gate is formed substantially in the same plane as that of at least one electrode 8 formed in a mesa shape. For example, second gate leading protrusions 18 are formed on both buried gate type static induction thyristors, second gate leading electrode wirings 19 covering the whole part is provided, and second gate leading electrode wiring 19 is formed simultaneously in the same step, material and thickness as those of anode electrode wirings 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of bipolar semiconductor switching elements, and particularly to the gate electrode structure of high-speed, large-capacity elements such as GTO thyristors and SI thyristors.

[Conventional technology]

An example of a conventional type is a double-sided buried gate type electrostatic induction thyristor (hereinafter referred to as Buried-Gate type DQu).
ble GateStatic Induction
DG-3ITh, which is a part of Thyristor, will be explained. DG-8IT prototyped by our company
h (Proceedings of 1988 In
terrationalSymposinrn on
Pmer Semt conductor Deviu
s, Tokyo.

pp, 183-188 r A Dou) cue -
Gate-Type 5tatic-tndduct
ionThyristor J) is shown in FIG. 4.

In the figure, (1) is an N high resistivity semiconductor substrate, (2) is a p
A high resistivity semiconductor substrate, each of which has a first conductivity type opposite to the lamp.
．． There are second gate regions +3+ and +41, which control on/off of the main current flowing between the cathode +N low resistance region (5) and the anode P low resistance region (6). +7) 18
+ +9) tl (D is the cathode, anode, the first
The gate, the electrode wiring of the second gate part, antiz are the high resistivity channel bright areas that serve as the path for the main current flowing between the anode (6) and the power sword (5), (13 is the mechanical reinforcement of the element and the load sink) 111 L of the second gate electrode wiring αG, and the gate part Mai in the center of the part
ll (14 is insulated with an insulating ceramic seal α9, and the Mo part around the element is also insulated with an insulating ceramic seal U■. 07) is a mechanical-electrical seal around the element where the PN junction is glH. The padding film is made of St rubber for stability, and is a metal wiring such as solder, which is characteristic of the prior art.

Next, the operation will be explained.

DG-8I Th is 1st gate (3) - Power sword (5)
By applying a forward or reverse bias between the gate and the second gate (4) and the node (6), a depletion layer is generated in the channel region Qll (121), which becomes the main current path, and the channel region (Ill (2) By opening and closing, the main current is turned 0N-OFF.Therefore, in order to take as many main current paths as possible within the limited element area and to make the reverse bias voltage as high as possible when the gate is reverse biased. A buried gate structure in which the first gate and cathode or the second gate and anode are arranged three-dimensionally is effective.In this structure, in order to take out the gate, the cathode and anode parts must be mesa-etched. Since it is left in the form of an island, a step difference of about 30 μml is created between the electrode extraction portion of the gate portion and the anode and cathode electrode portions.

[Problem to be solved by the invention]

Since the conventional Otani needle bipolar semiconductor switching device such as DG-9ITh was constructed as described above, it had the following problems.

First, since the central gate portion 1136 of the element is recessed in the shape of several tens of micrometers as mentioned above, it was originally the anode MO.
It is desirable that the center gate electrode recess 14) of the disk be shaped into a convex shape depending on the degree of depression on the element side.
Considering the machining accuracy of the Mo plate surface roughness, the structure of the insulating ceramic seal, and the variations in the level difference on the element side, it is virtually impossible to
4) On one side, wiring must be done using an electrode material that is flexible due to heating, melting, deformation, etc. for a stepped shape like the one made by Chunichi Electrode Co., Ltd.; There were problems in that controllability was poor and device reliability was difficult to obtain.

Second, in order to improve the electrical, mechanical, and thermal adhesion of high-power devices such as thyristors with corner plate Mo electrodes, etc., the semiconductor substrate and anode plate were originally attached using the A/gold alloy method. However, the gate electrode In L part is shown in Fig. 400.
Since the gate is recessed, it is impossible to bond the alloy to the gate portion, and therefore, in this case as well, there is a problem in that it is difficult to ensure the long-term reliability of the device's electrical characteristics.

Thirdly, when assembling the device package, several hundred Kf
The elements are pressure-welded at a pressure of f/cd, but since the central second gate part is separated from the anode plate Mo plate over a wide area, it is not possible to maintain a very large pressure-welding pressure, and the cathode electrode wiring on the lk electrode side and the first There was a problem of ε, which made the contact resistance at the electrode wiring part of the gate unstable.

Fourthly, at least one of the semiconductor substrate and the anode plate has a thickness of several tens of μm.
Since the process of providing a general-purpose thick film metal electrode is required, there is a problem that the process is more complicated and longer than the bonding process using the A/gold alloy method.

This invention was made to solve the above-mentioned problems, and at the same time facilitates the removal of the buried gate electrode, it also provides a large-capacity, high-density, bad d-polar type semiconductor switching device with high long-term electrical and mechanical reliability. The purpose is to obtain a device with high precision and a slow process.

[Means for Solving the Problems] A bipolar semiconductor switching device according to the present invention is such that the IBL portion of the buried gate has an electrode at the same height as at least one of the cathode and the anode. be.

[Effect]

In this invention, a part of the buried gate electrode is not excavated by etching, but is left with the same height of 8 as the cathode or anode, and in some cases, a region of the same conductivity type as the buried gate region is formed on the surface. By doing so, electrode removal at the gate portion is facilitated and the electrical and mechanical reliability of the device is improved.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, the parts that are different from the conventional one are the protrusion for the second gate IHt of 0, and the electrode wiring for the second gate 11 that completely covers this part.Other symbols is the same as the conventional one, so the explanation will be omitted.

Next, the operation will be explained.

In this example, a part of the central second gate surface is left unexcavated by etching, etc., so the surface of the gate has the same shape as the other anode electrode (8). ,
The second gate of this part is formed at the same time as the anode electrode wiring (8) using the same material and thickness in the same process as the anode electrode wiring (8). Therefore, the contact resistance, mechanical strength, and electrical reliability are the same as those of the connection between the anode plate α and the anode electrode wiring (8), and the electrode wiring tl for the second gate opening 1h
l and anode plate central gate part Mo! It is possible to connect 1t14, and it is possible to provide the element with mechanical strength that can withstand large pressure during packaging.

In addition, in the above embodiment, the electrode wiring a for the second gate is placed on the surface of the portion directly above the second gate in the center that is left without being etched, in such a way that it extends to the surface of the second gate where the trench 1b is formed. However, in the embodiment shown in FIG.
Form a region ■, and form a second gate IB on a part of the surface of the
It is possible to obtain the same effect by forming electrode wiring Qq for #B.

Further, the embodiment shown in FIG. 2 shows a structure ε in which the second gate IBL circular electrode wiring a9 is formed only in the part of the anode Mo plate α in contact with the central second gate extraction gate portion Mo rod round. However, this central second gate IB t,
The electrode wiring curve for the buried gate trench IM L as shown in Figure 1.
, may extend to the surface of the part.

In the embodiments shown in FIGS. 1 and 2, the buried gate IBL
Although the case has been described in which the mesa-shaped projection portion of , is formed only on one side of the anode side, it is also possible to form the buried gate IHL projection portion on both the anode side and the cathode side as shown in FIG. In this case, since the cathode side gate extraction is formed on the same plane as the cathode part, it becomes easily applicable to the full press method in which the single conductor element is not attached to the anode plate or the like and puff caging is performed only by mechanical pressure bonding.

In addition, in the above embodiment, the buried gate type DG-8ITh was explained, but the GTO (Gate-Full-OF)
F) It will soon be possible to apply it to all bipolar semiconductor switching elements, including thyristors.

〔Effect of the invention〕

That's all VC,! According to the invention of -, a part of the lead-out electrode of the buried gate is taken out from a plane at the same height as at least one of the cathode and the anode.
The contact resistance of each electrode part is small and stable, and the A/gold alloy method is applied! This has the effect of providing stable and highly reliable electromechanical properties of the entire device.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing a double-sided buried gate type electrostatic induction thyristor which is an example of a large-capacity bipolar semiconductor switching device according to an embodiment of the present invention, and FIGS.
The figure is a schematic sectional view of a semiconductor switching device of the same type as FIG. 1 showing another embodiment of the present invention, and FIG. 4 is a schematic sectional view of a semiconductor switching device of the prior art. In the figure, +11, (21 are N type and P type hole resistivity semiconductor substrates respectively, +3114+ are first gate P type and second gate respectively) -N type low resistance hook region, +51 (6) are each cathode N type , anode P-type low resistance region, 17) +8
1 is each cathode and anode electrode wiring, (9) 1it
) are the first. Second gate electrode wiring, (11) tlZ
are the cathode side and anode height measurement resistivity channel regions, respectively,
03 is an anode Mo plate, (141 is a gate Mo rod, i
19 is an insulating ceramic seal between the anode and the second gate, 00 is an insulating ceramic seal, 0 is a puffy basitan film, os G! 2nd gate recess l protrusion,
(1!J is the electrode wiring for the second gate/BL, ■ is the second gate poor conduction type bright area on the surface of the projection for taking out the second gate F, Qυ is the first gate IBL, The protrusion, ■ indicates the first gate on the surface of the protrusion for taking out the first gate, and the electrode wiring for the conductive type ship, and ■ indicates the electrode wiring for the first gate/HL. , or a corresponding portion.

Claims (1)

[Claims] First and second main electrodes are formed on both main surfaces sandwiching a semiconductor substrate serving as a main current path, and a buried gate is formed in the semiconductor substrate near at least one of the main electrodes to control on/off of the main current. 1. A bipolar semiconductor switching device having an electrode region, characterized in that a lead-out portion of the buried gate is formed substantially on the same plane as at least one main electrode formed in a mesa shape.