JPS60119777A - Gate turn-off thyristor - Google Patents

Abstract

PURPOSE:To perform lead bonding with high efficiency without deteriorating gate turn-off thyristor characteristics by a method wherein regions on the surface of a chip whereto leads are to be bonded are so metallized as to ensure solderability. CONSTITUTION:The lead bonding regions 107a, 106a of a cathode metallized electrode 107, gate metallized electrode 106 are to be so metallized as to be solderable. The other regions of the electrodes 107, 106 are to be made of Al layers capable of a fine pattern for the realization of performance characteristics specified for the given gate turn-off thyristor. An Al-Ni-Au laminate, for example, is the solderable structure to be used for the lead bonding regions 107a, 106a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a gate turn-off thyristor, and particularly to an electrode structure of a lead wire bonding region in a metallized electrode on a chip surface thereof.

[Prior Art] Currently, energy saving and energy saving have become a social mission. In order to cope with this, new functional elements have been developed in the field of power electronics, and the demand for them is rapidly increasing. Recently, gate turn-off thyristors have been attracting attention as elements used particularly in inverter chopper circuits. The reason for this is that the gate turn-off thyristor is superior to both conventional transistors and high-speed switching thyristors as an element for high-speed switching power, and has ideal features. Its major features are listed below. (1) Since it has a self-shutoff ability, a forced commutation circuit unlike conventional high-speed switching thyristors is not required, and the device can be made smaller and lighter.

(2) It is possible to control the Δ and A° of the element with a small amount of control power. (3) A thyristor with a short turn-off time can be obtained relatively easily compared to conventional high-speed switching thyristors.

(4) It is easy to make high-voltage and large-current devices. (5) It has a surge current withstand capacity of 4fIi, which is similar to that of the circuit C Lister. The main application fields of gate turn-off thyristors, which have the advantages mentioned above, are industrial equipment that mainly uses electric power, power converters such as inverters, and power supply devices, but the field of application will continue to expand in the future. There is expected.

Generally, a thyristor has a P-type emitter I'11. N-type base layer, P-type base layer, and N-type 1-type PNPN
The P-type emitter N, P-type base layer, and N-type emitter layer each have an anode metallized electrode (hereinafter referred to as "A electrode j
), gate metallized electrode (hereinafter referred to as "G electric t^")
), and cathode metalized electrode (hereinafter referred to as "K"), and cathode metallized electrode (hereinafter referred to as "K
Three electrodes (also referred to as "electrodes") are provided. If a predetermined voltage is applied between the A- electrodes so that the A electrode has a positive potential, and a small current is passed from the G electrode to the electrodes, the thyristor shifts from the OFF state to the ON state.
A large main current (on current) flows from the electrode to the electrode. That is, it can operate as a non-contact switch. However, in a general thyristor, the control function of the G electrode is lost once the thyristor changes from the off state to the on state. In order to return a general thyristor from the on state to the off state, (1) reduce the on-current to below the holding current, or (2) force a current to flow in the opposite direction between the electrodes A- from the outside. It is necessary to use one of the following methods: On the other hand, a gate turn-off thyristor has the same basic structure as a general thyristor, but a major feature different from a general thyristor is that it has a self-shutoff ability. That is, to G- of the gate turn-off thyristor in the on state! It has a feature that the gate turn-off thyristor can be shifted from the on state to the off state by flowing a reverse current (current from the K electrode to the G electrode) between the electrodes.

Next, the structure of a conventional gate turn-off thyristor chip will be explained using FIGS. 1 to 3. FIG. 1 is a top view of the gate turn-off thyristor chip 100. A glass passivation 109 is provided on the periphery of the chip 1000, and a gate metallized electrode 106 is numbered and roughened inside the glass passivation 109. On the inside thereof, there are arranged electrodes 106 and cathode metallized electrodes 107 which are intricately shaped like teeth of a comb, and the distance between these electrodes is 1! It is insulated by oxide 11108.

FIG. 2 shows a cross-sectional structure along the 2-12 section of the chip shown in FIG. A type base layer 103 and a P-type emitter layer 102 are formed, and gallium, boron, or the like is diffused as a P-type impurity. In the upper surface layer of the P-type base layer, there is an N-type emitter layer 10 in which an N-type impurity such as phosphorus is diffused in a partial region.
4 is formed. P-type emitter layer 102. P type base l1g103. Further, on the surfaces of the N-type bases 11!104, an anode metallized electrode 105 and a gate metallized electrode 106. and a cathode metallized electrode 107 are formed in ohmic contact. FIG. 3 shows the cross-sectional structure of the chip 100 taken along the section 3--3 in FIG. 1, and the structure of each part is the same as that in FIG. 2. Generally, the metallized layer of the anode metallized electrode 105 is made of, for example, AI-Mo so that the chip 100 can be fixed to a heat sink or the like by soldering.
-Ni -Au, AI -Zn -1'Ji -A
A laminated metallization such as u, cr-Ni-Au is used.

On the other hand, for the metallized layers of the gate metallized electrode 106 and the cathode metallized electrode 107, A1 is used, which is suitable for processing and forming a fine pattern necessary for a gate turn-off thyristor without achieving a predetermined performance.

The transition process from the on state to the off state of the gate turn-off thyristor, that is, the transition process during the turn-off process, the node current (A current) i], the gate current i (H) and the anode-cathode voltage The time change of V is shown in Figure 6 (a
), (b>, (c), respectively, the time t on the horizontal axis in J3
It is shown on the vertical axis. In Figure 6(d), i
The respective positional relationships of t and lG oVA are shown. Turn-off gain (GOrf) is one of the evaluation items for gate turn-off thyristors. Qon
is expressed as the ratio of 1t(H,o (controllable on-current) and IG,(goo1 to reverse current peak la) as shown in equation (1).

Qoff −+ 7 G c , /! a a -('
I) Therefore, at turn-off, the gate current ig flows in the opposite direction -IGM^×"l TGO/'f GR.

For example, I T a o =200A, Qoff
In the element with =4, triR = 50A, and a large gate reverse current will flow. Further, the overcontrol on-current f TGO of the gate No. 1 to No. 1 futhyristors is expressed by equation (2), and is inversely proportional to the cathode effective electrode width (S).

I TI$≦Q-GofF-V**□VIrT/S・/
Dp ・−(2) Here, VRG: gate reverse voltage, Wp
: Thickness of P type base 103, ■: Length of cathode electrode 107, S: Width of cathode electrode 107, pr
: To P type under N type emitter Jilil1104 ~
This is the lateral resistance of the base layer 103.

Therefore, in order to obtain a predetermined gate turn-off thyristor resistance by increasing the controllable on-current 1tco, it is necessary to make the cathode effective electrode width (S) as narrow as possible, and formation of a fine pattern is required. Therefore, A1 is suitable as the metallization for the cathode metallized electrode 107 and the gate metallized electrode 106, and is generally employed. On the other hand, in the O/X assembly method for gate turn-off thyristors with a TGO of up to about 200 A, due to cost considerations, the anode side is soldered to the heat sink plate of the anode metallized electrode 105, and the cathode metallized electrode 105 is soldered to the heat sink plate. As shown in the enlarged view in FIG. 7(a), the electrode 107 and gate metallized electrode 106 have a thickness of 300 to 400 μm to the A1 metallized surface.
A common method is to take out the electrode to the outside by ultrasonically welding 300 A1 thin wires with a diameter of about m. However, as described above, a large current flows through both IT c o + j RG, so when using A1 thin wire, it is necessary to ultrasonically weld a plurality of wires in parallel, which has the drawback of poor assembly workability.

[Summary of the Invention] The present invention has been made in view of the drawbacks of the conventional gate turn-off thyristors, and provides a method for attaching lead wires to the cathode metallized electrode and the gate metallized electrode without impairing the performance of the gate turn-off thyristor. The purpose is to provide a gate turn-off thyristor that has high reliability and can be installed with good workability.

The present invention is characterized by: 11 base layers made of a semiconductor of a first conductivity type; a second base layer made of a semiconductor of a second conductivity type adjacent to one side of the first base layer; a first emitter layer made of a second conductivity type semiconductor adjacent to the other side of the first base layer; and a first conductive layer formed in a partial region of the surface layer of the second base layer. a second emitter layer made of a type semiconductor, the surface pattern of the second emitter layer is comb-shaped;
In the gate turn-off thyristor, the gate turn-off thyristor has a metallized electrode portion that is in ohmic contact with the surfaces of the emitter layer, the second base layer, and the second l-mitter layer, respectively. The area where the lead wires of the metallized electrode part are connected has a metal electrode structure that can be soldered.

[Embodiments of the Invention] A chip structure of a gate turn-off thyristor according to the present invention will be described with reference to FIGS. 4, 2, and 5. FIG. 4 shows a chip top view of a gate turn-off thyristor according to the invention. The cross-sectional structure of the chip along section 2--2 in FIG. 4 is the same as that in FIG. 2, and the cross-sectional structure along section 5-5 is shown in FIG. The structure of the main parts of the gate turn-off thyristor chip according to the present invention is the same as that of the conventional one, so a detailed explanation of that part will be omitted.

The structural boundary between the gate turn-off thyristor chip according to the present invention and the conventional one is the lead wire connection region 107a of the cathode metallized electrode 107 and the gate metallized electrode 106.

The metallized structure of 106a is formed as a metallized layer to which lead wires can be soldered, and the metallized structure of cathode metallized electrode 107 and gate metallized electrode 06 other than the lead wire connection part is formed to obtain a predetermined performance of the gate turn-off thyristor. The reason is that it is made of All-all, which is suitable for fine pattern processing. The metallized structure that can be soldered to the lead wire connection areas 107a and 106a is AI-Mo-Nl-Au or A.
Laminated metallization such as I-Zll-Ni-Au is used. As a method for forming the laminated metallization in this portion, a vapor deposition method or a combination method such as vapor deposition and plating can be used. Also, as a method for forming the metallized layer in this part, the lead wire connection areas 107a, 106
At the time of forming the A1 metallized layer other than a, an A1 metallized layer is simultaneously formed under the metallized regions 107a and 106a by a vapor deposition method, and then the metallized region 'IO'7a is formed.
, 106a, or a method in which only the metallized regions 107a and 106a are formed separately from the A1 metallization of the metallized regions 107 and 106, and the metallization in each region is formed in a separate process so that they are continuous. Needless to say.

An example of a method for connecting the lead wires to the lead wire connection areas 107a and 106a is shown in FIG. 7(b). A nickel-plated lead wire 400 made of a metal such as copper in a relatively thin plate shape and capable of being soldered is attached to the solder layer 20.
Cathode metallized electrode portion 107a or gate metallized electrode 1 formed for lead wire connection through 0
Soldering is fixed to 06a. It goes without saying that the method of the present invention may be applied only to the cathode metallized electrode structure depending on the size of IGR determined from the current capacity of the gate turn-off thyristor (1vGo).

Furthermore, the present invention provides, in addition to the gate turn-off risk,
Needless to say, the present invention can also be applied to semiconductor devices such as power transistors having fine pattern metallized electrodes.

[Effects of the Invention] As described above, according to the present invention, a highly reliable gate turn-off thyristor is provided that allows connection of lead wires with good assembly workability without impairing the characteristics of the gate turn-off thyristor. be able to.

[Brief explanation of drawings]

FIG. 1 is a top view of a conventional gate turn-off thyristor chip. FIG. 2 is a cross-sectional structural diagram of the chip shown in FIGS. 1 and 4 taken along section 2-2. FIG. 3 is a cross-sectional structural diagram of the chip shown in FIG. 1 taken along section 3--3. FIG. 4 is a top view of a gate turn-off thyristor chip which is an embodiment of the present invention. Figure ff15 is a cross section 4 along section 5-5 of the chip in Figure 4.
It is a fi drawing. FIG. 6 is a diagram showing the time changes and measured values d of the anode current, gate 7tf current, and anode-cathode voltage during the turn-off process of the gate turn-off thyristor. <a> is the time change of the node current j,
(b) shows the change in the current i(H), (C> shows the time change in the anode-cathode voltage ν8, and (d
) are these i,,i6. Let us show the positional relationship of v. FIG. 7 is a diagram showing a method of connecting a lead wire to a cathode metallized electrode or a gate metallized electrode. (a
) shows the conventional method, and (b) shows the method according to the present invention. In the figure - (, 100 is a gate turn-off thyristor chip, 101 is an N-type base layer made of an N-type semiconductor, 10
2 is a P-type emitter layer made of a P-type semiconductor, 103 is a P-type base layer, 104 is an N-type emitter, 105 is a 7-node metallized electrode, 106 is a gate metallized electrode, 1
06a is the lead wire connection area of the gate metallized electrode, 1
07 is the cathode metal rice core, 107a is the lead wire connection area of the cathode metal rice electrode, and 108 is the gate electrode.
Cathode insulation II oxide film, 109 is glass passivation film, 200 is solder layer, 300 is A1111!1
wire, 400 is copper lead plate, A is 7 node electrode, 1<14
G is the cathode electrode, G is the gate electrode, i↑ is the anode (A) current, and IG is the gate current. In each figure, the same reference numerals indicate the same content or corresponding parts. Agent Masuo Oiwa Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Hand 1 sale month) Positive ;! ：(self-pleased)G(kottr)
i Month 11 1. Indication of the case No. 1987-228043 2. Name of the invention Kate turn off the lister ζ 3, Na+Ii iJ: Representative of the person doing the work +I+ f: 8 Part 5, Specification subject to amendment Column 6 for detailed description of the invention and brief description of drawings in the book, contents of amendment (1) [N-type base fi11] on page 6, line 12 of the specification
04J is corrected to “N-type emitter J1104J.” (2) riGnAx in the third line of page 8 of the specification = 1st +
o, /Ic*J as I'tGMAx-tGR=
Corrected to ITao/GoffJ. (3) Change “over-controlled on-current” on page 8, line 7 of the specification to “
Corrected to ``controllable on-current.'' (4) Change “lateral resistance” on page 6, line 12 of the specification to “
Corrected to "average resistivity". (5) "Resistance" on page 8, line 16 of the specification is corrected to "performance." (6) rloooJ on page 15, line 3 of the specification
Correct to J. (7) "IG indicates gate current" on page 15, line 16 of the specification [iG indicates gate current, VA indicates anode-cathode voltage. ” is corrected. that's all

Claims (3)

[Claims] (1) a first base layer made of a semiconductor of a first conductivity type; a second base layer made of a semiconductor of a second conductivity type adjacent to one side of the first base layer; a first emitter layer made of a second conductivity type semiconductor adjacent to the other side of the first base layer; and a first conductivity type formed in a partial region of the surface layer of the second base layer. a second emitter layer made of a semiconductor, the surface pattern of the second emitter layer is comb-shaped, and the first emitter layer, the second base layer, and the second emitter layer are In the turn-off thyristor having metalized electrode parts in ohmic contact with the surfaces of the layers, at least a connection area for connecting a lead wire to the metal electrode part on the second emitter layer is provided. A gate turn-off thyristor characterized by a metallized electrode structure that allows soldering. (2) The gate turn-off thyristor according to claim 1, wherein the connection region on the second base layer is made of a metalized electrode wet structure that can be soldered. (3) The metallized electrode structure of the connection area, which can be soldered, is connected to the AI from the first or second semiconductor surface side.
-Mo -Nl-Au or AI -Zn -Nl-A
3. The gate turn-off thyristor according to claim 1, wherein the gate turn-off thyristor has a laminated structure.