CN107818916B - Preparation method of front metal electrode structure of crimping type IGBT device - Google Patents

Abstract

The present invention relates to a method for preparing a front-side crimping metal electrode structure of a crimping IGBT device, which comprises the following steps: step 1, providing an IGBT wafer prepared with a front-side cell structure; step 2, depositing metal on a substrate key is combined on the connecting metal electrode layer; step 3, depositing the required metal on the above-mentioned metal deposition substrate, and the deposited metal is electrically connected to the connecting metal electrode layer through the metal deposition pattern; step 4, depositing the metal The deposition substrate is separated from the connecting metal electrode layer; step 5, a required passivation layer is prepared on the front side of the above-mentioned IGBT wafer. The invention has simple process steps, is compatible with the existing technology, can effectively realize the preparation of the crimped metal electrode layer on the front side of the crimped IGBT device, and can save the photolithography process of crimped the metal electrode layer on the crimped IGBT device. Effectively shorten the processing cycle of the crimp IGBT device, reduce the processing cost, and be safe and reliable.

Description

Preparation method of front metal electrode structure of press-contact IGBT device

technical field

The invention relates to a preparation method, in particular to a preparation method of a front-side crimping metal electrode structure of a crimping IGBT device, and belongs to the technical field of microelectronics.

Background technique

IGBT (Insulated Gate Bipolar Transistor, Insulated Gate Bipolar Transistor) is a voltage-controlled power device with high input impedance of MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor, Metal-Oxide Semiconductor Field-Effect Transistor). and BJT (Bipolar Junction Transistor, Bipolar Junction Transistor) two advantages of low on-voltage drop, because IGBT devices have the advantages of small driving power and reduced saturation voltage, IGBT devices are widely used as a high-voltage switch. each field.

Compared with the traditional welding IGBT package, the crimp IGBT does not need chip welding, avoids the binding of leads, and can reduce the parasitic inductance of the circuit; the crimp IGBT module can dissipate heat on both sides, with higher heat dissipation efficiency and reliability. better. The crimped IGBT module broadens the application field of the welded IGBT module.

In crimping applications, IGBT chips need to withstand pressure (between 8-65kN). This pressure will affect the structure of the chip and then affect its electrical characteristics. Therefore, special design is required for IGBT chips used in crimping packaging to minimize The effect of pressure on electrical properties. At present, one of the common methods in the world is to design a special crimping area on the IGBT chip, but the waste of the IGBT chip is too large; another common method is: adding a layer of soft metal on the front electrode of the traditional IGBT chip to increase the The thickness of the metal, the ductility of the metal with the increased thickness plays a certain buffering effect on the force of the chip; among them, the increased metal mainly forms the crimping metal electrode layer, and the original metal layer forms the connecting metal electrode layer, which can be formed by connecting the metal electrode layer. The connection lead-out electrode of the front cell of the press-contact IGBT.

When the soft metal is used to increase the thickness of the metal, there are three specific implementations: first, after the metal electrode is completed, the secondary metal deposition, photolithography process, and metal etching are performed to prepare the soft metal, but this method A corrosion barrier layer (usually SixNy) needs to be grown before the second layer of metal is deposited, and a photolithography process needs to be added, which leads to prolonged chip processing cycles and increased processing costs. The specific process steps are shown in Figure 2; the second , directly depositing thick metal, which is completed by two photolithography processes and metal etching. However, because metal etching is generally wet etching, the thickness of the two layers of metal is not easy to control, and the process accuracy is required to be high. The specific process steps are as follows As shown in Figure 3; thirdly, the two layers of metal are formed by two times of growth and two photolithography, and there is no need to etch a barrier layer in the middle of the two layers of metal etching. The specific process steps are shown in Figure 4; In other words, the requirement for process accuracy is low, which can save the cost of tape-out. In terms of the conventional semiconductor process process, the third solution still adds a lithography process.

To sum up, the existing process for realizing soft metal requires that two layers of metal electrodes on the front side of the crimp IGBT need to be grown twice and lithography twice, and the lithography process has high cost and long production cycle, which is not conducive to the crimp IGBT. The production cost of wafers is reduced.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies in the prior art, and to provide a method for preparing a front metal electrode structure of a crimp IGBT device, which has simple process steps, is compatible with the existing technology, and can effectively realize the front side of a crimp IGBT device. The preparation of the upper crimped metal electrode layer can save the photolithography process of the crimped metal electrode layer on the crimped IGBT device, effectively shorten the processing cycle of the crimped IGBT device, reduce the processing cost, and be safe and reliable.

According to the technical solution provided by the present invention, a preparation method of a front metal electrode structure of a press-contact IGBT device, the preparation method of the front metal electrode structure comprises the following steps:

Step 1, providing an IGBT wafer prepared with a front cell structure, and a connecting metal electrode layer drawn from the front cell structure is also provided on the IGBT wafer;

Step 2, providing a metal deposition substrate with a metal deposition pattern, and bonding the metal deposition substrate on the connecting metal electrode layer;

Step 3, depositing the required metal on the above-mentioned metal deposition substrate, and the deposited metal is electrically connected to the connecting metal electrode layer through the metal deposition pattern;

Step 4, separating the metal deposition substrate from the connecting metal electrode layer to obtain a crimping metal electrode layer electrically connected to the connecting metal electrode layer;

Step 5. Prepare the required passivation layer on the front side of the above-mentioned IGBT wafer.

After the required passivation layer is prepared on the front side of the IGBT wafer, a backside processing step of the IGBT wafer is also included. The backside processing steps of the IGBT wafer include backside thinning, ion implantation and activation, and backside metallization.

The metal deposition substrate is circular, and the metal deposition substrate is provided with a missing corner or a gap, and the missing corner or gap provided on the metal deposition substrate is determined by the wafer and is consistent with the shape of the wafer.

The material of the metal deposition substrate includes glass.

The thickness of the metal deposition substrate is 50 μm˜300 μm.

The metal deposition pattern includes a plurality of positioning holes penetrating through the metal deposition substrate. After passing through the positioning holes, the deposited metal can be in contact with the connecting metal electrode layer and be electrically connected. The setting of the positioning holes of the metal deposition substrate is consistent with the design of the metal electrode layer crimped on the chip.

The advantages of the invention: the metal deposition substrate can be bonded on the connecting metal electrode layer, the metal deposition pattern is used to deposit metal, and after the metal deposition substrate is separated from the connecting metal electrode layer, the connecting metal electrode can be obtained The crimping metal electrode layer electrically connected to each other can be used continuously after the metal deposition substrate is separated from the connecting metal electrode layer, the process steps are simple, and it is compatible with the existing process, and can effectively realize the crimping metal on the front side of the crimping IGBT device. The preparation of the electrode layer can save the photolithography processing procedure of pressing the metal electrode layer on the pressing IGBT device, effectively shorten the processing cycle of the pressing IGBT device, reduce the processing cost, and be safe and reliable.

Description of drawings

FIG. 1 is a cross-sectional view of a conventional press-contact IGBT device.

Fig. 2 is a flow chart of the existing first preparation process steps.

Fig. 3 is the flow chart of the existing second preparation process steps.

FIG. 4 is a flow chart of the existing third preparation process steps.

FIG. 5 is a flow chart of the preparation process steps of the present invention.

FIG. 6 is a schematic structural diagram of the metal deposition substrate of the present invention.

FIG. 7 is another structural schematic diagram of the metal deposition substrate of the present invention.

Description of reference numerals: 1-N-type base region, 2-N+ buffer region, 3-P+ collector region, 4-P-type base region, 5-N+ source region, 6-field oxide layer, 7-conductive polysilicon, 8 -Interlayer dielectric layer, 9-connecting metal electrode layer, 10-crimping metal electrode layer, 11-collector metal layer, 12-metal deposition substrate, 13-missing corner, 14-notch and 15-gate oxide layer .

Detailed ways

The present invention will be further described below with reference to the specific drawings and embodiments.

As shown in Figure 5: In order to effectively realize the preparation of the crimped metal electrode layer on the front of the crimped IGBT device, the photolithography process of the crimped metal electrode layer on the crimped IGBT device can be omitted, and the crimped IGBT device can be effectively shortened. The processing cycle of the IGBT device reduces the processing cost, and the preparation method of the front metal electrode structure of the present invention comprises the following steps:

Step 1, providing an IGBT wafer prepared with a front cell structure, and a connecting metal electrode layer 9 leading out of the front cell structure is also provided on the IGBT wafer;

Specifically, the front cell structure and the connecting metal electrode layer 9 can be prepared by using technical means commonly used in the technical field, and the source electrode of the IGBT wafer can be formed by connecting the metal electrode layer 9, which is well known to those skilled in the art. It is not repeated here.

As shown in FIG. 1 , the front-side cell structure includes a P-type base region 4 disposed in the N-type base region 1 , an N+ source region 5 is arranged in the P-type base region 4 , and an N+ source region 5 is arranged on the front surface of the N-type base region 1 . The field oxide layer 6 and the gate oxide layer 15 are provided with conductive polysilicon 7 on the field oxide layer 6 and the gate oxide layer 15. The conductive polysilicon 7 is supported on the field oxide layer 6 and the gate oxide layer 15, and the conductive polysilicon 7 is also connected to the P-base. A gate oxide layer 15 is spaced between the regions 4 . The conductive polysilicon 7 is insulated and isolated from the connecting metal electrode layer 9 through the interlayer dielectric layer 8 , and the connecting metal electrode layer 9 is in ohmic contact with the N+ source region 5 and the P-type base region 4 .

Step 2, providing a metal deposition substrate 12 with a metal deposition pattern, and bonding the metal deposition substrate 12 on the connecting metal electrode layer 9;

Specifically, the metal deposition substrate 12 has a circular shape, and the metal deposition substrate 12 is provided with a missing corner 13 or a notch 14 . In FIG. 6 , the metal deposition substrate 12 is a schematic diagram of setting a cutout 13 , and in FIG. 7 , the metal deposition substrate 12 is a schematic diagram of a cutout 14 . In the specific implementation, the metal deposition substrate 12 is provided with a cutout 13 . The case of the notch 14 is mainly related to the shape of the crimp IGBT wafer, and the notch 13 or the notch 14 provided on the metal deposition substrate 12 can be consistent with the shape of the crimp IGBT wafer. After the shape of the metal deposition substrate 12 is consistent with the shape of the pressure-contact IGBT wafer, when the metal deposition is performed, the deposited metal will only contact and electrically connect with the connecting metal electrode layer 9 through the metal deposition pattern. The connection state of the remaining positions of the connection metal electrode layer 9 above the front side of the press-contact IGBT wafer will not be affected.

In a specific implementation, the material of the metal deposition substrate 12 includes glass. The thickness of the metal deposition substrate 12 is 50 μm˜300 μm. The metal deposition pattern includes a number of positioning holes penetrating the metal deposition substrate 12, the positioning holes penetrate the metal deposition substrate 12, the positioning holes are periodically repeated or regularly distributed on the metal deposition substrate, and the positioning holes are located in the metal deposition substrate. The area position, opening area, shape and spacing on the deposition substrate 12 are all determined according to the design of the crimped metal electrode layer directly above the crimped IGBT wafer, which is well known to those skilled in the art, and will not be repeated here. Repeat.

Step 3, depositing the required metal on the above-mentioned metal deposition substrate 12, and the deposited metal is electrically connected to the connecting metal electrode layer 9 through the metal deposition pattern;

Specifically, the deposited metal material and the deposition process conditions are the same as those in the prior art, which are well known to those skilled in the art, and will not be repeated here. Due to the existence of the metal deposition pattern, the deposited metal can be electrically connected to the connecting metal electrode layer 9 through the metal deposition pattern.

Step 4, separating the metal deposition substrate 12 from the connecting metal electrode layer 9 to obtain a crimping metal electrode layer 10 electrically connected to the connecting metal electrode layer 9;

Specifically, the metal deposition substrate 12 is bonded and separated from the connecting metal electrode layer 9 by using technical means commonly used in the technical field. After the metal deposition substrate 12 is separated from the connecting metal electrode layer 9, a crimping metal The distribution of the electrode layer 10 and the crimping metal electrode layer 10 is consistent with the metal deposition pattern. After the metal deposition substrate 12 is separated from the connecting metal electrode layer 9, it can continue to be used for the preparation of the crimping metal electrode layer 10 of other IGBT devices, as long as the metal deposition pattern of the metal deposition substrate 12 is consistent with the required pressure. The connection to the metal electrode layer 10 can be adapted.

Step 5. Prepare the required passivation layer on the front side of the above-mentioned IGBT wafer.

Specifically, after the required passivation layer is prepared on the front side of the IGBT wafer, a backside processing step of the IGBT wafer is also included. The backside processing steps of the IGBT wafer include backside thinning, ion implantation and activation, and backside metallization. The thinning of the back includes the use of mechanical grinding and thinning. After ion implantation and activation, the N+ buffer area 2 and the P+ collector area 3 are obtained on the back of the IGBT wafer, and the collector metal 11 and the collector metal 11 are obtained after metallization. 3 ohm contact with the P+ collector.

Claims (3)

1. a preparation method of the front metal electrode structure of a crimping type IGBT device, is characterized in that, the preparation method of the described front metal electrode structure comprises the steps: Step 1, providing an IGBT wafer prepared with a front cell structure, and a connecting metal electrode layer drawn from the front cell structure is also provided on the IGBT wafer; Step 2, providing a metal deposition substrate with a metal deposition pattern, and bonding the metal deposition substrate on the connecting metal electrode layer; Step 3, depositing the required metal on the above-mentioned metal deposition substrate, and the deposited metal is electrically connected to the connecting metal electrode layer through the metal deposition pattern; Step 4, separating the metal deposition substrate from the connecting metal electrode layer to obtain a crimping metal electrode layer electrically connected to the connecting metal electrode layer; Step 5, preparing the required passivation layer on the front side of the above-mentioned IGBT wafer; The metal deposition substrate is circular, and the metal deposition substrate is provided with a missing corner or a notch; The material of the metal deposition substrate includes glass; The metal deposition pattern includes a plurality of positioning holes penetrating through the metal deposition substrate. After passing through the positioning holes, the deposited metal can be in contact with the connecting metal electrode layer and be electrically connected. 2. The method for preparing a front metal electrode structure of a crimped IGBT device according to claim 1, wherein after the required passivation layer is prepared on the front side of the IGBT wafer, it also comprises a backside processing step of the IGBT wafer, Backside processing steps for IGBT wafers include backside thinning, ion implantation and activation, and backside metallization. 3 . The method for preparing a front metal electrode structure of a press-contact IGBT device according to claim 1 or 2 , wherein the thickness of the metal deposition substrate is 50 μm˜300 μm. 4 .

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