CN107644810B - Front electrode processing method of crimping IGBT/FRD chip - Google Patents

Abstract

The invention provides a front electrode processing method of a crimping IGBT/FRD chip, which comprises the steps of forming a first film layer above a first metal layer by adopting a chemical vapor deposition method and etching the first film layer to form a first window; performing back splash etching on the first metal layer exposed at the first window; growing a second metal layer on the surface of the combined structure formed by the first metal layer and the first film layer by adopting a sputtering method, and etching the second metal layer; and coating a second film layer on the surface of the combined structure formed by the first film layer and the second metal layer, and etching the second film layer to form a second window for welding. Compared with the prior art, the front electrode processing method of the crimping IGBT/FRD chip provided by the invention has the advantages that the existing equipment is not required to be improved, and the operation is simple.

Description

A front electrode processing method for a press-fit IGBT/FRD chip

Technical Field

The invention relates to the technical field of power electronic power devices, and in particular to a method for processing a front electrode of a press-fit IGBT/FRD chip.

Background technique

The fully controlled power electronic device IGBT (Insulated Gate Bipolar Transistor) is widely used in the field of high-power and high-voltage equipment due to its superior gate control function, low conduction loss and simple drive circuit. The fully controlled power electronic device IGBT mainly includes press-fit IGBT and weld-fit IGBT in terms of packaging form. The press-fit IGBT has the following advantages over the weld-fit IGBT:

①: The internal leads are connected by crimping, eliminating most of the welding points, thus effectively reducing the failure rate of welding point cracking due to power cycling and thermal cycling;

②: It can achieve double-sided heat dissipation, so the heat dissipation efficiency is higher and the reliability is better;

③: Easy to connect in series, which can increase the voltage level of the equipment;

④: Its packaging failure mode is short-circuit mode, that is, during the overvoltage breakdown process, the internal leads and silicon chip of the press-fit IGBT form a eutectic conductive alloy, forming a short circuit between its emitter and collector; based on this short-circuit mode, when the press-fit IGBT is applied to DC transmission projects, even if any one of the series-connected press-fit IGBTs fails, the remaining redundant press-fit IGBTs can still work normally.

In summary, the press-fit power module based on the press-fit IGBT chip can be widely used in the fields of flexible DC transmission and reactive power compensation technology. However, the press-fit IGBT chip and FRD chip (Fast Recovery Diode) contained in the press-fit power module need to withstand a pressure of 8 to 65 kN. This pressure will affect the structure and electrical characteristics of the press-fit IGBT chip and FRD chip, thereby reducing the reliability of the press-fit power module.

The current method to solve the pressure on the press-fit IGBT/FRD chip is to add a layer of soft metal on its front electrode, using the ductility of the metal to buffer the pressure on the press-fit IGBT/FRD chip. There are two main process methods for adding a layer of soft metal to the front electrode in conventional semiconductor processes:

1. Direct method

Thick metal is directly deposited on the front electrode through two photolithography and etching processes. However, it is difficult to control the thickness of the two metal layers using wet etching, so the process requires high precision and is difficult to achieve.

2. Indirect method

After the front-end process of the press-fit IGBT/FRD chip is completed, the metal mask is used for evaporation, and the metal reaches the substrate surface through the window of the metal mask, and is deposited in the designated area to form a thick metal electrode. Although the indirect method reduces one photolithography and etching process compared to the direct method, shortening the processing cycle and cost, it requires the modification of existing equipment, which is difficult to implement.

Summary of the invention

In order to overcome the defects of the prior art, the present invention provides a front electrode processing method of a press-fit IGBT/FRD chip, a press-fit IGBT chip, a press-fit FRD chip and a press-fit power module.

In the first aspect, the technical solution of a method for processing the front electrode of a press-fit IGBT/FRD chip in the present invention is:

The front electrode comprises a first metal layer and a second metal layer, and the front electrode processing method comprises:

forming a first thin film layer on the first metal layer by chemical vapor deposition and etching the first thin film layer to form a first window;

Performing back sputtering etching on the first metal layer exposed at the first window to remove the oxide layer on the surface of the first metal layer and roughen the surface;

sputtering the second metal layer onto the surface of the combined structure formed by the first metal layer and the first thin film layer, and etching the second metal layer;

A second thin film layer is coated on the surface of the combined structure formed by the first thin film layer and the second metal layer, and the second thin film layer is etched to form a second window for welding.

The preferred technical solution further provided by the present invention is that the thickness of the first metal layer exposed at the first window by back sputtering etching is 50 angstroms.

The preferred technical solution further provided by the present invention is: coating the second film layer on the surface of the combined structure formed by the first film layer and the second metal layer comprises:

The second film layer is spin-coated on all surfaces of the combined structure.

The present invention further provides a preferred technical solution: the thickness of the first metal layer is 4 microns; the thickness of the second metal layer is 3-8 microns.

The present invention further provides a preferred technical solution: the first film layer is a SixNy film layer; the second film layer is a polyimide film layer.

The preferred technical solution further provided by the present invention is: the thickness of the first film layer is 0.7 micrometers; the thickness of the second film layer is 20 micrometers.

In the second aspect, a technical solution of a press-fit IGBT chip in the present invention is:

The press-fit IGBT chip comprises a collector electrode, an emitter electrode and a gate electrode, wherein the emitter electrode is a front electrode manufactured by the above-mentioned front electrode processing method of a press-fit IGBT/FRD chip.

In a third aspect, a technical solution of a press-fit FRD chip in the present invention is:

The press-fit FRD chip includes a front electrode manufactured by the above-mentioned front electrode processing method of a press-fit IGBT/FRD chip.

In a fourth aspect, a technical solution of a press-fit power module in the present invention is:

The press-fit power module comprises a plurality of the press-fit IGBT chips and a plurality of the press-fit FRD chips.

Compared with the closest prior art, the beneficial effects of the present invention are:

1. A method for processing a front electrode of a press-bonded IGBT/FRD chip provided by the present invention. The front electrode of the press-bonded IGBT/FRD chip comprises two metal layers. The ductility of the metal layers can be used to buffer the pressure borne by the press-bonded IGBT/FRD chip, thereby reducing the influence of the pressure on the electrical characteristics of the press-bonded IGBT/FRD chip.

2. The present invention provides a front electrode processing method for a press-fit IGBT/FRD chip, which performs back sputtering etching on the first metal layer exposed at the first window, which can not only remove the oxide layer on the surface of the first metal layer, but also roughen the first metal layer, which is conducive to sputtering the second metal layer on the first metal layer, thereby increasing the adhesion of the two metal layers;

3. The present invention provides a method for processing the front electrode of a press-fit IGBT/FRD chip, wherein the thickness of the first metal layer is 4 microns, the thickness of the second metal layer is 3-8 microns, and the thickness of the combined structure of the two metal layers after sputtering can reach 7-12 microns, which can increase the pressure that the front electrode can withstand;

4. A press-fit IGBT chip provided by the present invention has an emitter electrode comprising two layers of soft metal, which is conducive to buffering the pressure borne by the press-fit IGBT chip, and the pressure value can reach 8-65kN;

5. A press-fit FRD chip provided by the present invention has a front electrode comprising two layers of soft metal, which is conducive to buffering the pressure borne by the press-fit IGBT chip, and the pressure value can reach 8-65kN;

6. A press-fit power module provided by the present invention comprises a plurality of press-fit IGBT chips and a plurality of press-fit FRD chips, wherein the emitter electrode of the press-fit IGBT chip comprises two layers of soft metal, which is beneficial for buffering the pressure borne by the press-fit IGBT chip, and the pressure value can reach 8-65kN; the front electrode of the press-fit FRD chip comprises two layers of soft metal, which is beneficial for buffering the pressure borne by the press-fit IGBT chip, and the pressure value can also reach 8-65kN.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of an implementation process of a method for processing a front electrode of a press-fit IGBT/FRD chip according to an embodiment of the present invention;

FIG2 is a schematic structural diagram of a front electrode of a press-fit IGBT/FRD chip according to an embodiment of the present invention;

Wherein, 201: substrate; 202: first metal layer; 203: second metal layer; 204: first thin film layer; 205: second thin film layer.

Detailed ways

In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

A front electrode processing method of a press-fit IGBT/FRD chip provided by an embodiment of the present invention is described below in conjunction with the accompanying drawings.

FIG1 is a schematic diagram of the implementation process of a method for processing a front electrode of a press-fit IGBT/FRD chip in an embodiment of the present invention, and FIG2 is a schematic diagram of the structure of a front electrode of a press-fit IGBT/FRD chip in an embodiment of the present invention. As shown in the figure, the front electrode of the press-fit IGBT/FRD chip in this embodiment includes a first metal layer 202 and a second metal layer 203. After the first metal layer 202 is processed at a corresponding position of the press-fit IGBT/FRD chip using a conventional semiconductor process, the front electrode composed of the first metal layer 202 and the second metal layer 203 is processed according to the following steps:

Step S101: Form a first thin film layer 204 on the first metal layer 202 by chemical vapor deposition, and etch the first thin film layer 204 to form a first window. The first metal layer 202 can be made of aluminum, with a thickness of 4 microns, and the substrate 201 can be a silicon wafer. The first thin film layer 204 can be made of SixNy thin film, with a thickness of 0.7 microns.

In this embodiment, the first thin film layer 204 may be etched by dry etching to form the first window.

Step S102: performing back sputtering etching on the first metal layer 202 exposed at the first window to remove the oxide layer on the surface of the first metal layer 202 and roughen its surface.

In the present embodiment, the main purpose of performing the reverse sputtering etching process on the first metal layer 202 exposed at the first window is: since metal aluminum is easily oxidized in the air, the oxide layer on the surface of the first metal layer 202 can be removed by the reverse sputtering etching process, and the surface of the first metal layer 202 can also be roughened, which is beneficial to sputtering the second metal layer 203 on the first metal layer 202, that is, it is beneficial to the adhesion between the two metal layers.

In this embodiment, the thickness of the back sputtering etching performed on the first metal layer 202 exposed at the first window may be 50 angstroms, so as to remove the oxide layer on the surface of the first metal layer 202 .

Step S103: sputter the second metal layer 203 on the surface of the combined structure formed by the first metal layer 202 and the first film layer 204, and etch the second metal layer 203. The second metal layer 203 can be made of metal aluminum, and its thickness can be 3-8 microns.

Step S104: coating a second thin film layer 205 on the surface of the combined structure formed by the first thin film layer 204 and the second metal layer 203, and etching the second thin film layer 205 to form a second window for welding.

In this embodiment, coating the second film layer 205 on the surface of the combined structure includes: spin coating the second film layer 205 on all surfaces of the combined structure. The second film layer 205 can be a polyimide film layer PI (Polyimide, PI) with a thickness of 20 microns.

The present invention also provides a press-fit IGBT chip and gives a specific embodiment. In this embodiment, the press-fit IGBT chip includes a collector electrode, an emitter electrode and a gate electrode. Among them, the emitter electrode is a front electrode manufactured by the front electrode processing method of the above-mentioned press-fit IGBT/FRD chip shown in Figure 2. The emitter electrode contains two layers of soft metal, which is conducive to buffering the pressure borne by the press-fit IGBT chip. In this embodiment, the press-fit IGBT chip can withstand a pressure of 8-65kN.

The present invention also provides a press-fit FRD chip and gives a specific embodiment. In this embodiment, the press-fit FRD chip includes a front electrode manufactured by the front electrode processing method implementation process of the above-mentioned press-fit IGBT/FRD chip shown in Figure 2. The front electrode contains two layers of soft metal, which is conducive to buffering the pressure borne by the press-fit FRD chip. In this embodiment, the press-fit FRD chip can withstand a pressure of 8-65kN.

The present invention also provides a press-fit power module and gives a specific embodiment. In this embodiment, the press-fit power module includes a plurality of press-fit IGBT chips and a plurality of press-fit FRD chips. Among them, the press-fit IGBT chip can be the press-fit IGBT chip provided in the above embodiment, and the press-fit FRD chip can be the press-fit FRD chip provided in the above embodiment. In this embodiment, the press-fit power module can withstand a pressure of 8-65kN.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims (9)

1. A method for processing a front electrode of a press-fit IGBT/FRD chip, wherein the front electrode comprises a first metal layer and a second metal layer, wherein the method for processing the front electrode comprises: forming a first thin film layer on the first metal layer by chemical vapor deposition, and etching the first thin film layer to form a first window; Performing back sputtering etching on the first metal layer exposed at the first window to remove the oxide layer on the surface of the first metal layer and roughen the surface; sputtering the second metal layer onto the surface of the combined structure formed by the first metal layer and the first thin film layer, and etching the second metal layer; A second thin film layer is coated on the surface of the combined structure formed by the first thin film layer and the second metal layer, and the second thin film layer is etched to form a second window for welding. 2. A method for processing a front electrode of a press-fit IGBT/FRD chip as claimed in claim 1, characterized in that the thickness of the first metal layer exposed at the first window by back sputtering etching is 50 angstroms. 3. A front electrode processing method for a press-fit IGBT/FRD chip according to claim 1, characterized in that the second film layer is coated on the surface of the combined structure formed by the first film layer and the second metal layer: The second film layer is spin-coated on all surfaces of the combined structure. 4. The method for processing the front electrode of a press-fit IGBT/FRD chip according to claim 1, wherein the thickness of the first metal layer is 4 microns; the thickness of the second metal layer is 3-8 microns. 5. The method for processing the front electrode of a press-fit IGBT/FRD chip according to claim 1, wherein the first film layer is a SixNy film layer; and the second film layer is a polyimide film layer. 6. A method for processing the front electrode of a press-fit IGBT/FRD chip as described in claim 1, 3 or 5, characterized in that the thickness of the first film layer is 0.7 microns; the thickness of the second film layer is 20 microns. 7. A press-fit IGBT chip, comprising a collector electrode, an emitter electrode and a gate electrode, wherein the emitter electrode is a front electrode manufactured by the front electrode processing method of a press-fit IGBT/FRD chip according to any one of claims 1 to 6. 8. A press-bonded FRD chip, characterized in that the press-bonded FRD chip has a front electrode manufactured by the front electrode processing method of a press-bonded IGBT/FRD chip according to any one of claims 1 to 6. 9 . A press-fit power module, characterized in that the press-fit power module comprises a plurality of press-fit IGBT chips according to claim 7 and a plurality of press-fit FRD chips according to claim 8 .