Semiconductor chip repairing method

Abstract

The invention discloses a method for repairing a semiconductor chip, which comprises the following steps of: firstly, screening out an electrode unit with unqualified withstand voltage in the semiconductor chip, and marking the electrode unit; and then, laser beams are adopted to heat the marked electrode units in the semiconductor chip to remove the metal layer. The laser beam is used for heating the metal layer to gasify the metal layer, the laser action time is short, the efficiency is high, the heat radiation influence on the surrounding area is small, the electrode unit is repaired through the method, the damage risk caused by manual introduction is greatly reduced, the repairing efficiency of the electrode unit is improved, and therefore the yield of a semiconductor chip is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors, and in particular relates to a semiconductor chip repair method. Background Art

[0002] With the development of power electronic devices and the demand for applications, the R&D of high-voltage and high-capacity power electronic devices is becoming more and more urgent. Taking the semiconductor device GCT (Gate-Commutated Thyristor) as an example, GCT has the advantages of high blocking voltage, large capacity, low cost and high reliability. It is a key component of high-voltage and high-capacity power electronic devices. Furthermore, the GCT chip is a device based on a silicon-based whole wafer, which consists of thousands of unit cells connected in parallel on the entire wafer. Figure 1 As shown. Currently, 4-inch and 6-inch GCT chips have been successfully developed. Figure 2 As shown, the GCT cell is a three-layer PN junction composed of four layers of semiconductor materials (i.e. Figure 2 The structure of J1, J2, and J3 in the GCT chip is equivalent to two double-layer PN junction transistors. When the GCT chip is turned off, a reverse voltage needs to be applied to the gate, which requires J3 to have sufficient voltage resistance, namely Vgk. According to the application requirements, the gate cathode voltage resistance is generally required to be above 20V. Before the GCT chip is packaged, the Vgk of each gate cathode unit (i.e., comb bar) needs to be tested first, and then for individual comb bars with abnormal Vgk, the aluminum electrode on the cathode is removed and the comb bar is insulated and isolated. As the wafer size increases, the number of comb bars on the GCT chip increases exponentially, and the Vgk testing of each comb bar of the GCT chip and the repair of abnormal comb bars have become more important.

[0003] At present, the conventional method for repairing GCT slivers is to first use mechanical methods, such as a scalpel to scrape off the metal aluminum layer on the abnormal sliver, and then manually brush the insulating curing material on the corresponding sliver to isolate the sliver. In actual operation, pure manual operation is used, which requires extremely high proficiency and skills of personnel, making the sliver repair work time-consuming and seriously affecting production capacity. In addition, the mechanical repair method is prone to scratches on the silicon, resulting in chip failure.

[0004] Therefore, how to improve the yield of semiconductor chips is becoming an increasingly urgent technical problem to be solved. Summary of the invention

[0005] In view of the above problems, the present invention provides a semiconductor chip repair method, which improves the semiconductor chip yield and repair efficiency.

[0006] The object of the present invention is to provide a semiconductor chip repair method, comprising:

[0007] Screen out the electrode units with unqualified withstand voltage in the semiconductor chip and mark them;

[0008] A laser beam is used to heat the marked electrode units in the semiconductor chip to remove the metal layer.

[0009] Further, using a laser beam to heat the marked electrode unit to remove the metal layer includes:

[0010] Using optical inspection equipment to determine the morphology and size of unqualified electrode units;

[0011] Based on the determined morphology and / or size, the unqualified electrode units are heated to remove the metal layer by adjusting the beam diameter, beam line and / or energy of the laser beam.

[0012] Furthermore, adjusting the beam diameter of the laser beam includes the following adjustment methods:

[0013] Adjust the focusing distance of the laser output beam, adjust the position and parameters of the optical elements in the laser, or couple the output fiber of the laser into the optical fiber and light guide;

[0014] Adjusting the beam line of the laser beam includes determining the moving step length and direction of the moving device during the heating and removing of the metal layer;

[0015] Adjusting the energy of the laser beam includes setting an energy value.

[0016] Furthermore, screening out the electrode units with unqualified withstand voltage in the semiconductor chip includes performing a reverse withstand voltage test on the electrodes in the semiconductor chip.

[0017] Furthermore, the method also includes increasing the nitrogen pressure to purge the surface of the semiconductor chip when heating to remove the metal layer, and recovering the gasified and condensed metal slag through vacuum.

[0018] Furthermore, it also includes

[0019] Automatically load the semiconductor chips to be repaired and transfer them to the bottom of the optical inspection equipment.

[0020] Furthermore, the method further comprises applying an insulating protective material on the electrode unit after heating and removing the metal layer, wherein:

[0021] The height of the electrode unit after being coated with the insulating protective material is lower than the height of any other identical electrode located on the same side of the electrode unit with the metal layer removed in the semiconductor chip.

[0022] Furthermore, the semiconductor chip includes a silicon-based chip and a non-silicon-based substrate type chip.

[0023] Furthermore, the metal layer includes metal materials and alloy materials.

[0024] Further, the semiconductor chip includes a GCT chip, the electrode unit includes a comb bar in a gate cathode of the GCT chip, and the metal material in the metal layer includes aluminum.

[0025] The semiconductor chip repair method of the present invention uses a laser beam to heat the metal layer to vaporize it. The laser action time is short, the efficiency is high, and the thermal radiation effect on the surrounding area is small. The electrode unit is repaired by this method, which greatly reduces the risk of damage introduced by humans and improves the repair efficiency of the electrode unit, thereby improving the yield of the semiconductor chip and greatly shortening the production cycle of the chip.

[0026] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 A GCT chip in the prior art is shown;

[0029] Figure 2 A schematic diagram of a GCT cell structure in the prior art is shown;

[0030] Figure 3 A schematic flow chart of a semiconductor chip repair method according to an embodiment of the present invention is shown;

[0031] Figure 4a A front view of a GCT chip in an embodiment of the present invention is shown;

[0032] Figure 4b A top view of a GCT chip in an embodiment of the present invention is shown;

[0033] Figure 5a A schematic diagram of the structure of a GCT chip before repair in an embodiment of the present invention is shown;

[0034] Figure 5b A schematic diagram of the structure of a GCT chip after repair in an embodiment of the present invention is shown;

[0035] Figure 5cA schematic structural diagram of a GCT chip after being repaired and coated with insulating material in an embodiment of the present invention is shown.

[0036] Description of the drawings: 1. Aluminum electrode above cathode, 2. Gate ring, 3. Gate, 4. Anode, 5. Groove, 6. Insulating material. DETAILED DESCRIPTION

[0037] 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.

[0038] like Figure 3 As shown, an embodiment of the present invention introduces a semiconductor chip repair method, the repair method comprising, first, screening out the electrode units in the semiconductor chip that fail the withstand voltage test and marking them; then, using a laser beam to heat the marked electrode units in the semiconductor chip to remove the metal layer. The above method uses a laser beam to heat the metal layer to vaporize it, the laser action time is short, the efficiency is high, and the thermal radiation effect on the surrounding area is almost negligible. Repairing the electrode unit by this method greatly reduces the risk of chip damage caused by scraping off the metal layer, improves the repair efficiency of the electrode unit, thereby improving the yield of the semiconductor chip, and also greatly shortens the production cycle of the chip.

[0039] In the embodiment of the present invention, the semiconductor chip includes a silicon-based chip and a chip of a non-silicon-based substrate type, wherein the semiconductor chip includes but is not limited to a silicon-based GCT chip, and may also be other silicon-based chips and chips of non-silicon-based substrates such as SiC (silicon carbide), GaAs (gallium arsenide), GaN (gallium nitride), etc., which are also applicable to the present invention. The metal layer includes a metal material and an alloy material, and the metal material includes aluminum, but is not limited thereto, and other metal materials or alloy materials are applicable to the present invention.

[0040] In the embodiment of the present invention, the semiconductor chip is a gate commutated thyristor GCT chip as an example to illustrate the above repair method. Figure 4a , 4b The GCT chip shown includes an aluminum electrode 1 above the cathode, a gate ring 2, a gate 3 and an anode 4, wherein the electrode includes a gate and a cathode, and the electrode unit is a comb bar in the gate cathode. Repairing the GCT chip includes:

[0041] First, the electrode units with unqualified withstand voltage in the semiconductor chip are screened out and marked; among them, the gate cathode of the GCT chip is made with an aluminum electrode, that is, an aluminum layer is set on the gate and cathode. After the gate cathode aluminum electrode of the GCT chip is made, the withstand voltage of the PN junction between the gate (P) and the cathode (N) is tested, that is, the gate cathode reverse withstand voltage Vgk test is performed, and the combs with unqualified Vgk are screened out and marked. Figure 5a The GCT chip state before repair is shown. Assuming that the comb strip corresponding to the aluminum electrode 1 above the second cathode from left to right fails to withstand the voltage, a laser beam is used to heat the comb strip that fails to withstand the voltage to remove the aluminum layer. Specifically, the aluminum layer of the comb strip on the cathode with insufficient withstand voltage can be removed, such as Figure 5b As shown, the aluminum electrode 1 above the cathode is removed to form a groove 5. In addition, the repair method also includes automatically loading the semiconductor chip to be repaired and automatically transferring it to the bottom of the optical detection device. Automatic loading and repair of semiconductor chips realizes automatic transmission of semiconductor chips, greatly shortens the repair time and improves the repair efficiency. Furthermore, the optical detection equipment is used to detect the morphology and / or size of the comb strip, and uses the information feedback to adjust the beam diameter of the laser beam, the beam motion line of the laser beam, and the energy. Among them, the optical detection equipment can be an AOI (Automated Optical Inspection) fully automatic optical detector.

[0042] Then, based on the determined morphology and / or size, the unqualified electrode unit is heated to remove the metal layer by adjusting the beam diameter, beam motion line and / or energy of the laser beam. Exemplarily, based on the determined morphology and / or size of the unqualified comb strip, the comb strip of the GCT chip is heated to remove the aluminum layer by adjusting the beam diameter, laser beam motion line and / or laser beam energy. Specifically, the morphology of the comb strip includes surface profile, edge, thickness and roughness, etc. Among them, the beam diameter size of the laser beam can be based on the morphology and / or size of the comb strip that fails the pressure resistance to adjust the focusing distance of the laser output beam, adjust the position and parameters of the optical element (such as a lens), or couple the output optical fiber of the laser to an appropriate optical fiber and light guide to control the spot size, so as to achieve the adjustment of the laser beam diameter. Preferably, the spot size does not exceed the size of the electrode unit (i.e., the comb strip), and adjusting the beam motion line of the laser beam includes determining the moving step and direction of the moving device during the removal of the metal layer. Specifically, the moving device includes a stage and a laser head. The laser head fixes the stage and moves, and the stage fixes the laser head. Based on the morphology and size of the unqualified comb strips, the motor drives the stage or the laser head to move along the set X, Y (i.e., coordinate) directions according to the set step length. Furthermore, each movement step of the stage and the laser head is within the morphology range of the comb strips. The energy of the laser beam can be adjusted by setting the energy value, etc. Specifically, the energy value of the laser beam is adjusted based on the morphology. By setting the beam diameter, stroke (i.e., beam line) and laser energy of the laser beam, the laser beam only acts on the abnormal comb strips and does not affect the surrounding normal areas. In addition, the laser action time is short and the efficiency is high, which further improves the efficiency of repairing the comb strips.

[0043] In an embodiment of the present invention, the repair method further includes, when heating to remove the metal layer, using increased nitrogen pressure to purge the surface of the semiconductor chip and recovering the vaporized and condensed metal slag through vacuum. Exemplarily, for the GCT chip, when heating to remove the aluminum layer, using nitrogen pressure to purge the surface of the semiconductor chip and recovering the vaporized and condensed aluminum slag through vacuum. While the laser beam is removing the aluminum layer, increasing a certain nitrogen pressure to purge the chip surface helps prevent the aluminum slag from sticking back, and at the same time, the vaporized and condensed aluminum slag is recovered through vacuum. Thus, the efficiency of the comb repair is improved by preventing the aluminum slag from sticking back and recovering the aluminum slag, and the reliability of the GCT chip is further improved.

[0044] Further, an insulating protective material is applied on the electrode unit after the metal layer is removed by heating, wherein the height of the electrode unit after the insulating protective material is applied is lower than the height of any other identical electrode on the same side of the electrode unit where the metal layer is removed in the semiconductor chip. Specifically, Figure 5cAs shown, the insulating protective material 6 is applied to the comb strips after the aluminum layer is removed by heating, wherein the height of the comb strips after the insulating protective material is applied is lower than the height of the aluminum electrode above any other cathode on the GCT chip. Preferably, the height of the comb strips after the insulating protective material is applied is lower than the height of the aluminum electrode above any surrounding cathode adjacent to it on the GCT chip. The comb strips are isolated by using an insulating curing material, wherein the thickness of the insulating curing material should be able to completely cover the comb strips from which the aluminum has been removed, and should not exceed the metal surface of the surrounding cathodes, thereby avoiding the stress concentration point during crimping, which may cause the chip to rupture and be damaged during crimping. Preferably, the comb strips coated with the insulating protective material 6 are also heated to heat and cure the newly applied insulating protective material to achieve passivation protection for the comb strips.

[0045] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A semiconductor chip repair method, characterized in that: include, Screen out the electrode units with unqualified withstand voltage in the semiconductor chip and mark them; A laser beam is used to heat the marked electrode units in the semiconductor chip to remove the metal layer.

2. The semiconductor chip repair method according to claim 1, characterized in that: Using a laser beam to heat the marked electrode unit to remove the metal layer includes: Using optical inspection equipment to determine the morphology and size of unqualified electrode units; Based on the determined morphology and / or size, the unqualified electrode units are heated to remove the metal layer by adjusting the beam diameter, beam line and / or energy of the laser beam.

3. The semiconductor chip repair method according to claim 2, characterized in that: Adjusting the laser beam diameter includes the following adjustment methods: Adjust the focusing distance of the laser output beam, adjust the position and parameters of the optical elements in the laser, or couple the output fiber of the laser into the optical fiber and light guide; Adjusting the beam line of the laser beam includes determining the moving step length and direction of the moving device during the heating and removing of the metal layer; Adjusting the energy of the laser beam includes setting an energy value.

4. The semiconductor chip repair method according to any one of claims 1 to 3, characterized in that: Screening out electrode units with unqualified withstand voltage in the semiconductor chip includes performing a reverse withstand voltage test on the electrodes in the semiconductor chip.

5. The semiconductor chip repair method according to claim 4, characterized in that: The method also includes increasing the nitrogen pressure to purge the surface of the semiconductor chip when heating to remove the metal layer, and recovering the gasified and condensed metal slag through vacuum.

6. The semiconductor chip repair method according to claim 5, characterized in that: It also includes automatically loading semiconductor chips to be repaired and automatically transferring them to the bottom of the optical inspection equipment.

7. The semiconductor chip repair method according to claim 6, characterized in that: The method further comprises applying insulating protective material on the electrode unit after heating and removing the metal layer, wherein: The height of the electrode unit after being coated with the insulating protective material is lower than the height of any other identical electrode located on the same side of the electrode unit with the metal layer removed in the semiconductor chip.

8. The semiconductor chip repair method according to claim 7, characterized in that: The semiconductor chips include silicon-based chips and non-silicon-based substrate type chips.

9. The semiconductor chip repair method according to claim 8, characterized in that: The metal layer includes metal materials and alloy materials.

10. The semiconductor chip repair method according to claim 9, characterized in that: The semiconductor chip includes a GCT chip, the electrode unit includes a comb bar in a gate cathode of the GCT chip, and the metal material in the metal layer includes aluminum.

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