Method for testing uniformity of thermal resistance of wafer functional layer of diamond GaN HEMT (High Electron Mobility Transistor) device

Abstract

The invention discloses a method for testing the thermal resistance uniformity of a wafer functional layer of a diamond GaN HEMT (High Electron Mobility Transistor) device. The method comprises the steps of compatible design of a test structure, design and preparation of a thermoelectric signal electrode, parameter control and test of an electrical method, and thermal resistance calculation and uniformity analysis of the functional layer. On the basis of a diamond GaN HEMT device structure and a wafer tape-out process, a thermal resistance test area is designed, a thermoelectric signal electrode is prepared, and the cooperative compatibility of a thermal test structure, the device structure and the wafer tape-out process is solved; in combination with a nine-point test area selected on the wafer, the thermal resistance uniformity analysis of a functional layer of the wafer is represented, and the direct analysis of the thermal resistance uniformity of the wafer interface of the device wafer of 4 inches and below can be realized at most; technical support is provided for control and optimization of a diamond GaN HEMT device wafer integration interface; the test method is more economical and convenient, and meets the development requirements of a new generation of semiconductor devices based on diamond materials and a thermal management technology thereof.

Description

Technical Field

[0001] The invention belongs to the technical field of diamond GaN device development and research, and in particular relates to a method for testing the thermal resistance uniformity of a diamond GaN HEMT device wafer functional layer. Background Art

[0002] GaN devices are widely used in radar, 5G communications, aerospace and other fields, but as GaN devices continue to develop towards higher power and higher efficiency, efficient thermal management technology has become an important factor restricting the performance improvement of devices. At present, the commonly used GaN device substrate materials are Si and SiC, etc., and the thermal conductivity is difficult to meet the heat dissipation requirements under high power conditions, which seriously limits the performance of GaN devices. The thermal conductivity of diamond material can reach 2200W / (m•K), which is 4 times that of SiC and 13 times that of Si. By heterogeneously integrating diamond with high-power devices GaN, the heat dissipation bottleneck of GaN HEMT devices can be effectively solved. However, the thermal resistance of the functional layer of diamond GaN HEMT devices is a direct reflection of the bonding quality and design quality of diamond and GaN devices. Therefore, the uniformity test of the thermal resistance of the functional layer of diamond GaN HEMT device wafer is the most direct method to realize the development of diamond GaN power devices and evaluate the advantages and disadvantages of the bonding integration process of diamond GaN power devices. However, this test technology has not yet formed a unified and standard test method.

[0003] Therefore, it is urgent to develop a testing method suitable for the thermal resistance of the functional layer of diamond GaN HEMT device wafers. Summary of the invention

[0004] Technical problem solved: In response to the above technical problem, the present invention provides a test method for the uniformity of thermal resistance of the functional layer of a diamond GaN HEMT device wafer. Based on the electrical method, a test method suitable for the thermal resistance of the functional layer of a diamond GaN HEMT device wafer is developed to meet the technical requirements for optimization of the bonding integration process of diamond GaN power devices and device performance evaluation.

[0005] Technical solution: A method for testing the uniformity of thermal resistance of a diamond GaN HEMT device wafer functional layer, comprising the following steps: S1. Test structure compatible design; S2. Design and preparation of thermoelectric signal electrodes; S3, electrical parameter control and testing; S4. Calculation and uniformity analysis of thermal resistance of functional layer.

[0006] Preferably, the specific process of the compatible design of the test structure in step S1 is: the thermal resistance of the wafer functional layer includes a bonding layer, a barrier layer and a passivation layer arranged in sequence from bottom to top, that is, a three-layer thin film structure constitutes the wafer functional layer; wherein the passivation layer material is an insulating material with a thickness of ≤300 nm, and the preparation process of the test area is to remove the top BCB protective layer of the diamond GaN HEMT device by plasma etching technology, and etch to the passivation layer to form a test area, and the overall etching range of the test area is 3-5μm larger than the plane size of the thermoelectric signal electrode.

[0007] Furthermore, the insulating material is SiN.

[0008] Preferably, in step S2, the thermoelectric signal electrode is designed to have a width of 5 μm-40 μm, an effective length of 750 μm-1500 μm, and a thickness of 50 nm-100 nm; the effective length is extended by 150 μm-250 μm to form a four-way circuit interconnection area, and the size of the circuit interconnection area is a square of 200 μm-500 μm.

[0009] Furthermore, the thermoelectric signal electrode material is Ti with a total thickness of 20% and Au with a total thickness of 80%, which is prepared by evaporation process of Ti first and Au later on the passivation layer. In order to ensure good contact between the electrode and the wafer functional layer, the process route of first electrode preparation, then BCB preparation, and finally BCB etching of the test area is adopted, which can effectively ensure the test accuracy.

[0010] Preferably, in step S3, to ensure the test accuracy, the test frequency is controlled at 3000Hz~100Hz, the frequency test interval is controlled at 5Hz~25Hz, the test frequency points are ≥100, and the number and interval of the selected frequency points can be coordinated and optimized according to the time and accuracy that need to be met, and the fundamental wave and 3 times harmonic signal changes with frequency are tested respectively.

[0011] Preferably, in step S4, the frequency range selected for the calculation and uniformity analysis of the thermal resistance of the wafer functional layer is ≥1000 Hz, and the number of frequency points selected is ≥100. The thermal resistance of the wafer functional layer is obtained by fitting the electrical calculation formula. Its uniformity is determined by selecting a 9-point method on the wafer, testing the thermal resistance of each point, and realizing the analysis of uniformity.

[0012] Beneficial effects: Based on the diamond GaN HEMT device structure and wafer flow process, the present invention designs a thermal resistance test area and prepares a thermoelectric signal electrode, thereby solving the synergistic compatibility between the thermal test structure and the device structure and the wafer flow process; and in combination with the selection of 9 test areas on the wafer, it is used to characterize the thermal resistance uniformity analysis of the wafer functional layer, and can achieve direct analysis of the thermal resistance uniformity of the wafer interface of 4-inch and below device wafers at most; it provides technical support for the control and optimization of the integrated interface of the diamond GaN HEMT device wafer; the test is more economical and convenient than other laser methods, and meets the development needs of a new generation of semiconductor devices based on diamond materials and their thermal management technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of a test structure designed in a method for testing the uniformity of thermal resistance of a functional layer of a diamond GaN HEMT device wafer according to the present invention; Figure 2 It is a schematic diagram of a test area in a method for testing the uniformity of thermal resistance of a functional layer of a diamond GaN HEMT device wafer according to the present invention. DETAILED DESCRIPTION

[0014] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments: Example 1

[0015] A method for testing the thermal resistance uniformity of a diamond GaN HEMT device wafer functional layer comprises the following steps: S1. Test structure compatible design: Figure 1 As shown, the test structure compatibility design is a secondary compatibility design based on the diamond GaN HEMT device process and structure. The wafer functional layer thermal resistance is a multi-layer structure, which includes a bonding layer, a barrier layer and a passivation layer from bottom to top, that is, a three-layer thin film structure constitutes the wafer functional layer; the passivation layer material is SiN, and the thickness is ≤300nm. The preparation process of the test area is to remove the top BCB protective layer of the diamond GaN HEMT device by plasma etching technology, and etch it to the passivation layer to form a test area. The overall etching range of the test area is 3-5μm larger than the plane size of the thermoelectric signal electrode ( Hk ), there must be a certain gap (H zone) between the test electrode and BCB. If the gap is too small, it will affect the influence and interference of BCB on the thermoelectric signal during the test process. If the gap is too large, it will affect the performance of the device.

[0016] S2. Design and preparation of thermoelectric signal electrodes. Specifically: The thermoelectric signal electrode includes an effective area (D) and four circuit interconnection areas (T). The thermoelectric signal electrode is designed to be between 5μm and 40μm wide, the effective area (Dl) is between 750μm and 1500μm long, and the thickness is between 50nm and 100nm; the effective area length is extended by 150μm-250μm to form 4 circuit interconnection areas (T), and the size of the circuit interconnection area (T) is a square of 200μm-500μm. The overall electrode design size is less than 1800μm*500μm. Too small affects the convenience of testing, and too large affects the cost of the device. In terms of process, the thermoelectric signal electrode material is 20% of the total thickness of Ti metal (Hdow) and 80% of the total thickness of Au material (Hup), which is prepared by the evaporation process of Ti first and then Au on the passivation layer. In order to ensure good contact between the electrode and the functional layer of the wafer, the process route of first preparing the electrode, then preparing the BCB, and finally etching the BCB in the test area is adopted, which can effectively ensure the test accuracy.

[0017] S3, electrical parameter control and testing: In order to ensure the test accuracy during the test process, the electrical parameter control and test settings are set to control the test frequency at 3000Hz~100Hz, based on the wafer functional layer structure setting; the frequency test spacing is controlled to 5Hz~25Hz, and the test frequency points are ≥100. The number and spacing of the selected frequency points can be coordinated and optimized according to the time and accuracy that need to be met. Test the changes of the fundamental wave and the 3rd harmonic signal with the frequency respectively.

[0018] S4. Calculation and uniformity analysis of thermal resistance of functional layer: The selected frequency range is ≥1000Hz, the number of selected frequency points is ≥100, and the thermal resistance of the wafer functional layer is obtained by fitting the electrical calculation formula. The uniformity is determined by selecting 9 points on the wafer. Figure 2 As shown, the 9 points selected are 1 point at the center of the wafer, 4 points at the 25% position of the horizontal and vertical lines, and 4 points at the 45% position of the vertical line after the horizontal and vertical lines are rotated 45 degrees; the thermal resistance of each point is tested, and the 9 groups of data and the deviations of the 9 groups of data from the average value are compared to realize the analysis of uniformity. The uniformity deviation is the percentage of the absolute value of the deviation between the test and the average value of each point and the average value. Example 2

[0019] A test method for the uniformity of thermal resistance of the functional layer of a diamond GaN HEMT device wafer is used to implement the test and analysis of the uniformity of thermal resistance of the functional layer of a 3-inch wafer of a diamond GaN HEMT device. The following is an explanation through specific tests: A 3-inch diamond GaN HEMT device was selected and taped to the passivation layer, which was made of SiN material with a thickness of 250nm. The photolithography evaporated electrode on the passivation layer was 100nm thick (20nm thick Ti, 80nm thick Au), 10μm wide, and 750μm effective length; the effective length was epitaxially extended by 250 μm to form a 4-way circuit interconnection area, and the size of the circuit interconnection area was a 200μm square. Subsequently, the BCB protective layer was prepared and the test area was etched. The overall etching range of the test area was 4μm larger than the plane size of the thermoelectric signal electrode. Subsequently, the diamond GaN HEMT device wafer test sample was placed in the test bench for interconnection, and the thermal resistance of its 9 point areas was tested and analyzed. The test frequency was designed to be 100Hz~2800Hz, and its frequency test interval was 20Hz, with 135 test frequency points. The input signal voltage of the electrical method was adjusted to ensure that the fundamental wave was 400mV, which met the high-precision acquisition of the electrical signal, and the fundamental wave and 3 times harmonic signal were tested with frequency. Finally, the thermal resistance of the wafer functional layer was obtained by fitting the electrical calculation formula. In order to ensure accuracy, the frequency range was selected as 200Hz-2500Hz, and the number of frequency points was selected as 115. The thermal resistance of the 9-point area was obtained by fitting the calculation formula, which was 121.59 m 2 K / GW, 123.87 m 2 K / GW, 120.69 m 2 K / GW, 122.78m 2 K / GW, 123.57 m 2 K / GW, 121.37 m 2 K / GW, 122.78 m 2 K / GW, 123.57 m 2 K / GW and 122.37 m 2 K / GW, and the average value is calculated to be 122.51 m 2 K / GW, the uniformity deviation is less than 1.11%.

[0020] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for testing the thermal resistance uniformity of a diamond GaN HEMT device wafer functional layer, characterized in that: The following steps are involved: S1. Test structure compatible design; S2. Design and preparation of thermoelectric signal electrodes; S3, electrical parameter control and testing; S4. Calculation and uniformity analysis of thermal resistance of functional layer.

2. The method for testing the thermal resistance uniformity of a diamond GaN HEMT device wafer functional layer according to claim 1, characterized in that: The specific process of the compatible design of the test structure in step S1 is as follows: the thermal resistance of the wafer functional layer includes a bonding layer, a barrier layer and a passivation layer arranged in sequence from bottom to top, that is, a three-layer thin film structure constitutes the wafer functional layer; wherein the passivation layer material is an insulating material with a thickness of ≤300 nm, and the preparation process of the test area is to remove the top BCB protective layer of the diamond GaN HEMT device by plasma etching technology, and etch to the passivation layer to form a test area, and the overall etching range of the test area is 3-5μm larger than the plane size of the thermoelectric signal electrode.

3. The method for testing the thermal resistance uniformity of a diamond GaN HEMT device wafer functional layer according to claim 2, characterized in that: The insulating material is SiN.

4. The method for testing the thermal resistance uniformity of a diamond GaN HEMT device wafer functional layer according to claim 1, characterized in that: In step S2, the thermoelectric signal electrode is designed to have a width of 5 μm-40 μm, an effective length of 750 μm-1500 μm, and a thickness of 50 nm-100 nm; the effective length is extended by 150 μm-250 μm to form a four-way circuit interconnection area, and the size of the circuit interconnection area is a square of 200 μm-500 μm.

5. The method for testing the thermal resistance uniformity of a diamond GaN HEMT device wafer functional layer according to claim 4, characterized in that: The thermoelectric signal electrode material is Ti with a total thickness of 20% and Au with a total thickness of 80%, which is prepared by evaporation process of Ti first and Au later on the passivation layer. In order to ensure good contact between the electrode and the wafer functional layer, the process route of electrode preparation first, BCB preparation second, and BCB etching of the test area last is adopted, which can effectively ensure the test accuracy.

6. The method for testing the thermal resistance uniformity of a diamond GaN HEMT device wafer functional layer according to claim 1, characterized in that: In step S3, to ensure the test accuracy, the test frequency is controlled at 3000Hz~100Hz, the frequency test interval is controlled at 5Hz~25Hz, the test frequency points are ≥100, and the number and interval of the selected frequency points can be coordinated and optimized according to the time and accuracy that need to be met, and the fundamental wave and 3 times harmonic signal are tested with frequency changes respectively.

7. The method for testing the thermal resistance uniformity of a diamond GaN HEMT device wafer functional layer according to claim 1, characterized in that: In step S4, the frequency range selected for the calculation and uniformity analysis of the thermal resistance of the wafer functional layer is ≥1000 Hz, and the number of frequency points is selected to be ≥100. The thermal resistance of the wafer functional layer is obtained by fitting the electrical calculation formula. Its uniformity is determined by selecting a 9-point method on the wafer, testing the thermal resistance of each point, and realizing the analysis of uniformity.

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