JPH02254754A - Semiconductor device - Google Patents

Abstract

PURPOSE:To facilitate the manufacture of electrodes and to make it possible to reduce sufficiently an electrode resistance by a method wherein the thicknesses of the stem parts of the electrodes are made thicker than the thicknesses of the branch parts of the electrodes. CONSTITUTION:A cathode electrode 13 and a gate electrode 16, which are formed on the surface of a semiconductor substrate 2, respectively consist of stem parts 13' and 16' and a multitude of branch parts 13'' and 16'' which are extended from the stem parts 13' and 16' in a comb-teeth form. In these electrodes 13 and 16, the stem parts 13' and 16' are both formed wider in steps as they go from their points toward their joints. Moreover, in the electrode 13 and the electrode 16, two Al layers are laminated at the stem parts, but one layer of an Al layer simply exists at the branch parts. In such a way, as the thicknesses of the stem parts, on which a current is concentrated, of the element electrodes are thicker than the thicknesses of their branch parts, a work of the branch parts does not become a difficult task and an electrode resistance can be reduced.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a semiconductor device.

[Conventional technology]

In a semiconductor device, an electrode for the semiconductor element is usually formed on the surface of a semiconductor substrate on which the semiconductor element is provided. may be used. FIG. 4 shows a conventional surface gate type electrostatic induction thyristor having this type of electrode.

This thyristor 50 includes a cathode region 52 on the front surface of a semiconductor substrate 51 and an anode region 5 on the back surface.
3, and these cathode region 52 and anode region 53
A high resistivity region (base region) 54 serving as a current path is provided therebetween, and a gate region 55 is further provided on the surface portion of the semiconductor substrate 51.

A cathode electrode 62 is provided in the cathode region 52, an anode electrode 63 is provided in the anode region 53, and a gate electrode 65 is provided in the gate region 55. The cathode electrode 62 and gate electrode 65 provided on the surface of the semiconductor substrate 510 are each composed of a trunk and branches extending from the trunk in a comb-like shape. For example, the gate electrode 65 has a wide trunk 65a and Many thin branches 65b
It consists of

This electrostatic induction thyristor 50 has many advantages such as high switching speed, low forward voltage drop, large current density, and high breakdown voltage.

(Problem to be Solved by the Invention) However, although the above-mentioned electrostatic induction SI risk is an element that can achieve high current density, the resistance of the electrode is not low enough, so the forward voltage at the electrode part There is a problem in that the drop is large and, as a result, the current withstand characteristics are insufficient.

In order to lower the electrode resistance, for example, it is possible to increase the electrode thickness.However, patterning of the metal film is required for electrode formation, and when increasing the electrode thickness, the metal film is thicker and has a comb-like shape. There is a problem in that patterning (processing) in the technical department becomes increasingly difficult.

An object of the present invention is to provide a semiconductor device in which an electric bridge for an element consisting of a trunk and a branch on the surface of a semiconductor substrate is easy to manufacture and has sufficiently low resistance. [Means for Solving the Problem] The above-mentioned problem In order to solve the problem, in the semiconductor device of the present invention,
The thickness of the main part of the semiconductor element electrode on the surface of the semiconductor substrate is made thicker than the thickness of the comb-like part.

Examples of such electrodes include those having a multilayer structure in which a metal layer with a pattern of only the trunk is laminated on a metal layer with a pattern of trunks and branches. Of course, it is not limited to this.

Furthermore, in addition to the above, the width of the stem of the electrode is increased stepwise or continuously from the tip side to the base where the current is concentrated. Of course, the lead wire is in contact with the base, and the collected current is ultimately guided from the base to the external terminal.

The electrode consisting of a trunk and a comb-like part is used as a cathode electrode or a gate electrode when the semiconductor element is a static induction thyristor, and is used as a source electrode or a gate electrode when the semiconductor element is a static induction transistor. Used as a gate electrode.

When there are a plurality of electrodes each consisting of a trunk and a comb-teeth-like section, the thickness of only the trunk of one electrode may be made thicker than the thickness of the branch. For example, only the cathode electrode or the source electrode may have a trunk thickness that is thicker than the branch part thickness, while the gate electrode may not have such a thickness.On the contrary, only the gate electrode may have a trunk thickness that is thicker than the branch part thickness. The cathode electrode and the source electrode do not have to be like that.

The electrode can be formed, for example, by patterning an aluminum film using photolithography technology.

It goes without saying that the type of semiconductor element, the type of electrode, the material for forming the electrode, and the method for forming the electrode are not limited to those exemplified above.

[For production]

An electrode consisting of a trunk and a comb-like part has a lower resistance because the frame is thicker. In the electrode trunk, the current flowing through each branch (if) gathers, so if the resistance in this part is reduced, the forward voltage drop can be effectively reduced.Moreover, the comb-like part is thin. There is no problem with processing, so processing is not difficult.

The base of the electrode trunk is a current concentration point, so
If the width at the base is wide (low resistance), for example, the forward voltage drop can be effectively reduced.

When the electrode resistance decreases, the forward voltage drop at the cathode and source electrodes becomes smaller, improving current withstand capability, and the control signal rises faster at the gate electrode.
Switching speed can be improved.

〔Example〕

Next, an electrostatic induction silicate according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the surface on which the cathode electrode and gate electrode are formed of a normally off type surface gated electrostatic induction cell according to an embodiment of the present invention.

FIG. 2 partially shows the internal structure of this electrostatic induction thyristor, and FIG. 3 schematically shows the basic structure of the electrostatic induction thyristor.

As shown in FIG. 2.3, the electrostatic induction thyristor 1 includes a cathode region (N" region) 3 on the front surface of a semiconductor substrate 2, and an anode region (P" region) 4 on the back surface. A high resistivity region (N- region) 5 serving as a current path is provided between the region 3 and the anode region 4, and a gate region (P'' region 6) is further provided on the surface portion of the semiconductor substrate 2.

In addition, 8 is the EQR electrode, 20 is the insulation electrode, and 21.2
2 is a bassibasin membrane. Furthermore, the section G at the end of the semiconductor substrate 2 has a guard ring structure for improving withstand voltage.

A cathode electrode 1'3 is provided in the cathode region 3, an anode electrode 14 is provided in the anode region 4, and a gate electrode 16 is provided in the gate region 6. As shown in FIG.
Both the cathode electrode 13 and the gate electrode 16 are composed of the stems 13', 16' and a number of comb-like protrusions 13'', 16'' extending from the stems 13', 16'.
As ′ goes from the tip to the base, the fortune becomes wider in a stepwise manner. Furthermore, the cathode electrode 13 and the gate electrode 16 have two aluminum layers laminated at the top, but
In the branches there is only one layer of aluminum. The gate electrode 8ii116 is composed of a lower aluminum layer 161 whose pattern including the trunk and branches combined has a thickness of about 1n, and an upper aluminum layer 162 whose pattern including only the trunk has a thickness of approximately 1n. Although not shown, the cathode electrode 13 has the same layer structure as the gate electrode 16. Both the cathode electrode 13 and the gate electrode 16 have their trunks thicker than their branches due to the overlying aluminum layer.

When a positive voltage is applied to the gate electrode 16 of the normally-off type electrostatic induction thyristor L, the depletion layer extending from the gate region 6 to the front surface of the cathode region 3 is removed, and a current flows between the cathode and the anode. It becomes like this.

Next, the results of measuring the forward voltage drop of the electrostatic induction thyristor 1 and the results of subjecting the thyristor 1 to a current withstand test will be explained. For comparison, an electrostatic induction thyristor was manufactured in the same manner as in the example except that there was no upper layer of the trunk and the electrode trunk and branch portions had the same thickness, and were similarly measured and tested. The results are shown in the table below.

Note that the forward voltage drop is a value when the current between the anode and the cathode is 3A. In addition, the main conditions for the current withstand test are as follows.

di/ld: 120A/μSEC Period: 150m5EC Pulse width = 1.2μSEC As seen from the above results, the electrostatic induction thyristor according to the example has significantly improved forward voltage drop and current withstand characteristics compared to the conventional one. For example, although the electrodes were made of aluminum, the cathode electrodes may be made of other materials such as doped polysilicon. The structure may be a combination of a plurality of materials in which the lower layer is doped polysilicon and the upper layer is aluminum, or the electrostatic induction thyristor may be of a normally-on type.

〔Effect of the invention〕

As described above, in the semiconductor device of the present invention, since the thickness of the element electrode where the current concentrates is thicker than the thickness of the branch part, the electrode resistance can be lowered without making processing of the branch part difficult. , characteristics such as forward voltage drop and current withstand capability are improved, and reliability is increased.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the formation surface of the cathode electrode and gate electrode of an electrostatic induction thyristor according to an embodiment of the present invention, FIG. 2 is a partial cross-sectional view of this electrostatic induction thyristor, and FIG. is a schematic sectional view for explaining the basic structure of the electrostatic induction thyristor, and FIG. 4 is a partial sectional view of a conventional electrostatic induction thyristor. 1... Electrostatic induction thyristor (semiconductor device) 2...
・Semiconductor substrate 13...Cathode 1 hole (electrode for element) 16...Gate bridge (electrode for element) 13',
16'... Executive 13'16'... Branch agent Patent attorney Takehiko Matsumoto Procedural amendment (Viewed August 21, 1999 Patent order No. 076008 Address: Oaza, Kadoma City, Osaka Prefecture 1048 Kadoma Name Name (583) Matsushita Electric Works Co., Ltd. Representative Lee □ Toshio Miyoshi 4, No representative As shown in attached document 6, Specification subject to amendment 7, Contents of amendment■ Page 9 of the specification, 7th from the bottom Correct the line ``rd I/l'' to rd I/d tJ.

Claims (1)

[Claims] 1. In a semiconductor device in which an electrode for a semiconductor element is formed on the surface of a semiconductor substrate on which the semiconductor element is provided, and the electrode is composed of a trunk and a branch extending in a comb-like shape from the trunk,
A semiconductor device characterized in that the thickness of the main part of the electrode is thicker than the thickness of the branch part.