Method for improving adhesive force between polymer and surface of GaN high-voltage power chip

Abstract

The invention discloses a method for improving the adhesive force between a polymer and the surface of a GaN high-voltage power chip, and the method sequentially comprises the following steps: S10, depositing a SiO2 thin film on the surface of GaN, then carrying out the photoresist coating in a yellow light environment, photoetching a periodic micro-groove pattern at the SiO2 thin film, then carrying out the corrosion to manufacture a SiO2 thin film groove, and removing the photoresist after the corrosion is completed; s20, performing surface selective wet etching on the groove bottom of the SiO2 thin film groove to form a nanoscale pit; and S30, the surface of GaN is coated with a polymer, and stepped curing is carried out in the N2 atmosphere. According to the method for improving the adhesive force between the polymer and the surface of the GaN high-voltage power chip, the adhesive force of a GaN-polymer interface can be effectively improved, the interface stress and electric leakage are reduced, and the breakdown withstand voltage yield is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor device processing, and in particular to a method for improving the adhesion between a polymer and the surface of a GaN high-voltage power chip. Background Art

[0002] Polymer materials, such as polyimide, epoxy resin, polyetheretherketone (PEEK), polyetherimide, polyphenylene sulfide, etc., generally have low surface energy (~40-50mJ / m 2 ), poor chemical compatibility with the GaN surface (polar surface), and other issues, resulting in insufficient interface adhesion.

[0003] In addition, due to the difference in coefficient of thermal expansion (CTE) (GaN: ~5.6ppm / ℃ vs. polymer: ~50ppm / ℃), interface delamination after thermal cycling is easily caused. At the same time, traditional roughening treatments (such as plasma etching) may also destroy the electrical properties of the GaN surface, making it difficult to form stable chemical bonds.

[0004] The above reasons lead to the problem of weak adhesion when directly coating the polymer on the GaN surface, which is prone to peeling in a long-term hot and humid environment. Summary of the Invention

[0005] The embodiments of the present application provide a method for improving the adhesion between a polymer and the surface of a GaN high-voltage power chip, which can effectively improve the adhesion of the GaN-polymer interface.

[0006] The present invention provides a method for improving the adhesion between a polymer and a surface of a GaN high-voltage power chip, comprising the following steps:

[0007] S10, depositing a SiO2 film on the GaN surface, then applying photoresist under yellow light, photoetching a periodic micro-groove pattern at the SiO2 film position, and then etching to form the SiO2 film grooves. After the etching is completed, the photoresist is removed;

[0008] S20, forming nanoscale pits at the bottom of the SiO2 film groove by surface selective wet etching;

[0009] S30, coating a polymer on the GaN surface and performing step curing in an N2 atmosphere.

[0010] In a possible implementation, the width of the SiO2 film grooves is 1-5 um, and the groove spacing is 2-10 um.

[0011] In a possible implementation, the depth of the nanoscale pits is 10-20 nm.

[0012] In a possible implementation, in step S10, a SiO2 film is deposited on the GaN surface by a PECVD machine, wherein the thickness of the SiO2 film is 50-200 nm.

[0013] In a possible implementation, in step S10, before photoresist coating is performed under yellow light, RTA high-temperature rapid annealing is first performed to eliminate hydrogen bonds in the SiO2 film and reduce micropores.

[0014] In a possible implementation, the surface selective wet etching is specifically: using a KOH / NaOH mixed solution for short-time etching, with the etching time being 1-5 minutes.

[0015] In a possible implementation, the concentration of the KOH / NaOH mixed solution is 0.1-1 mol / L, and the temperature is 40-60°C.

[0016] In a possible implementation, in step S30 , before coating the polymer on the GaN surface, the GaN surface is first subjected to an O 2 plasma treatment.

[0017] In a possible implementation, in step S30 , the thickness of the polymer is 8-12 um.

[0018] In a possible implementation, in step S30, the step curing is specifically: curing in a gradient temperature increase sequence, wherein the temperature increase gradient is specifically RT°C → 150°C → 250°C → 350°C.

[0019] Beneficial effects: Compared with the prior art, the method provided in the present application for improving the adhesion between the polymer and the surface of the GaN high-voltage power chip can effectively improve the adhesion of the GaN-polymer interface, wherein the scratch test is: the critical load is increased from 8N to 22N at most, wherein SEM observation: there is no crack in the interface, and the coupling agent is evenly covered, wherein the wet heat test: the peel strength retention rate after 1000 hours is 95%, and in addition, after electrical verification: the average leakage current is reduced from 4.44*10-5 to 3.9*10-5, a reduction ratio of about 13%, the average breakdown voltage is increased by 28V, and the overall change is convergent.

[0020] These and other objects, features and advantages of the present invention will be fully reflected in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic flow chart of the method for improving the adhesion between a polymer and the surface of a GaN high-voltage power chip according to the present application is shown.

[0022] Figure 2A parameter index curve diagram of the improved method for improving the adhesion between polymer and GaN high-voltage power chip surface in the present application is shown.

[0023] Figure 3 A schematic diagram showing a gap between polymer and GaN in the prior art is shown.

[0024] Figure 4 A schematic diagram showing the close connection between the polymer and GaN after improvement using the method of the present application.

[0025] Figure 5 A schematic diagram is shown of leakage improvement using the method of the present application, wherein the average reverse leakage at a voltage level of 1200V is reduced from 4.44*10-5 to 3.9*10-5, a reduction of approximately 13%.

[0026] Figure 6 A schematic diagram shows the improvement of withstand voltage using the method of the present application, wherein the average withstand voltage is increased from 1057V to 1085V, an increase of 28V, and the overall withstand voltage level becomes convergent. DETAILED DESCRIPTION

[0027] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are for illustrative purposes only, and those skilled in the art will readily appreciate other obvious variations. The basic principles of the present invention defined in the following description may be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0028] Those skilled in the art should understand that, in the disclosure of the specification, the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like to indicate the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0029] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the elements may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0030] refer to Figures 1 to 6 The present invention provides a method for improving the adhesion between a polymer and a GaN high-voltage power chip surface, comprising the following steps:

[0031] S10, depositing a SiO2 film on the GaN surface by or using a PECVD machine, wherein the thickness of the SiO2 film is 50-200 nm, and then performing or using RTA high-temperature rapid annealing to eliminate hydrogen bonds in the SiO2 film, reduce micropores, and rearrange atoms, thereby improving density and pressure resistance, and then performing photoresist coating under a yellow light environment, and using a stepper to photoetch a periodic micro-groove pattern at the SiO2 film position, and then performing BoE etching to produce SiO2 film grooves. After the etching is completed, the photoresist is removed, and the production of micro-nano grooves on the GaN surface is completed, wherein the groove width of the SiO2 film groove is 1-5 μm and the groove spacing is 2-10 μm;

[0032] It is worth mentioning that under different groove widths and groove spacings, the displayed indicators (mainly critical load and withstand voltage) are slightly different, but compared with the existing technology, they have all been significantly improved, as shown in the table below:

[0033]

[0034] In addition, the above table lists some of the data, not all of them. You can also select other pairing methods for the groove width and groove spacing data. For example, when the groove width is 2um, the groove spacing can be 6um, 7um, 9um, etc., and when the groove spacing is 4um, the groove width can be 3um, 4um, 5um, etc., as long as it is within the range of 1-5um for the groove width and 2-10um for the groove spacing.

[0035] S20, forming nanoscale pits at the bottom of the SiO2 film groove by surface selective wet etching to increase the mechanical anchoring effect, wherein the depth of the nanoscale pits is 10-20 nm, that is, the nanoscale pits can be selected from any value between 10 nm and 20 nm, including all natural numbers and decimals therebetween, wherein the surface selective wet etching is specifically: short-term etching using a KOH / NaOH mixed solution, the etching time is 1-5 minutes, wherein the concentration of the KOH / NaOH mixed solution is 0.1-1 mol / L, and the temperature is 40-60° C.;

[0036] S30, first perform O2 plasma treatment to increase the surface energy of GaN, then coat the GaN surface with a polymer with a thickness of 8-12um, and then perform step curing in an N2 atmosphere, wherein the step curing is specifically: curing in a gradient temperature rise sequence, wherein the temperature rise gradient is specifically RT℃→150℃→250℃→350℃, so as to reduce the stress increase caused by curing.

[0037] Therefore, the method provided in the present application for improving the adhesion between the polymer and the surface of the GaN high-voltage power chip is simple to implement and easy to operate, and can effectively improve the adhesion of the GaN-polymer interface, wherein the polymer includes polyimide, epoxy resin, polyetheretherketone (PEEK), polyetherimide, polyphenylene sulfide, etc., which has been verified to have unexpected results. After the improvement, the interface adhesion was tested, such as the standard scratch test: the critical load was increased from 8N to 22N at the highest and 16N at the lowest, which has an exponential increase effect;

[0038] As observed by SEM: there is no crack at the interface and the coupling agent is evenly covered;

[0039] For example, after 1000 hours of wet heat test, the peel strength retention rate is still as high as 95%.

[0040] It is also worth noting that the above three indicators show that the adhesion of the GaN-polymer interface has been significantly improved. In addition, standard electrical verification shows that the average leakage current has been reduced from 4.44*10-5 to 3.9*10-5, a reduction of about 13%, and the average breakdown voltage has increased by 28V, with overall convergence. This shows that while improving interface adhesion, it was unexpectedly found that this method can significantly improve the electrical characteristics of GaN chips.

[0041] Therefore, the method provided in this application for improving the adhesion between the polymer and the surface of the GaN high-voltage power chip can effectively improve the adhesion of the GaN-polymer interface, reduce interface stress and leakage, and improve the breakdown voltage yield.

[0042] Those skilled in the art will appreciate that the embodiments of the present invention described above and shown in the accompanying drawings are intended to be illustrative only and are not intended to limit the present invention. The advantages of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and illustrated in the embodiments. Any variations or modifications may be made to the embodiments of the present invention without departing from the principles described.

Claims

1. A method for improving the adhesion between a polymer and a GaN high-voltage power chip surface, characterized in that: The following steps are included in sequence: S10, depositing a SiO2 film on the GaN surface, then applying photoresist under yellow light, photoetching a periodic micro-groove pattern at the SiO2 film position, and then etching to form the SiO2 film grooves. After the etching is completed, the photoresist is removed; S20, forming nanoscale pits at the bottom of the SiO2 film groove by surface selective wet etching; S30, coating a polymer on the GaN surface and performing step curing in an N2 atmosphere.

2. The method for improving the adhesion between a polymer and a GaN high-voltage power chip surface according to claim 1, wherein: The width of the SiO2 film grooves is 1-5 μm, and the groove spacing is 2-10 μm.

3. The method for improving the adhesion between a polymer and a GaN high-voltage power chip surface according to claim 2, wherein: The depth of the nanoscale pits is 10-20 nm.

4. The method for improving the adhesion between a polymer and a GaN high-voltage power chip surface according to claim 1, wherein: In step S10, a SiO2 film is deposited on the GaN surface by a PECVD machine, wherein the thickness of the SiO2 film is 50-200 nm.

5. The method for improving the adhesion between a polymer and a GaN high-voltage power chip surface according to claim 1 or 4, characterized in that: In step S10, before photoresist coating is performed under yellow light, RTA high-temperature rapid annealing is first performed to eliminate hydrogen bonds in the SiO2 film and reduce micropores.

6. The method for improving the adhesion between a polymer and a GaN high-voltage power chip surface according to claim 1, wherein: The surface selective wet etching specifically includes: using a KOH / NaOH mixed solution for short-time etching, and the etching time is 1-5 minutes.

7. The method for improving the adhesion between a polymer and a GaN high-voltage power chip surface according to claim 6, wherein: The concentration of the KOH / NaOH mixed solution is 0.1-1 mol / L, and the temperature is 40-60°C.

8. The method for improving the adhesion between a polymer and a GaN high-voltage power chip surface according to claim 1, wherein: In step S30 , before coating the polymer on the GaN surface, the GaN surface is first subjected to an O 2 plasma treatment.

9. The method for improving the adhesion between a polymer and a GaN high-voltage power chip surface according to claim 1, wherein: In step S30 , the thickness of the polymer is 8-12 μm.

10. The method for improving the adhesion between a polymer and a GaN high-voltage power chip surface according to claim 9, wherein: In step S30, the step curing is specifically: curing by gradually increasing the temperature in sequence, wherein the temperature increasing gradient is specifically RT°C→150°C→250°C→350°C.

Images