METHOD FOR DETECTING DEFECTS IN GALLIUM NITRIDE HIGH ELECTRON MOBILITY TRANSISTOR

Abstract

A method for detecting defects in a GaN high electron mobility transistor is disclosed. The method includes steps of measuring a plurality of electrical characteristics of a GaN high electron mobility transistor, measuring the plurality of electrical characteristics after performing a deterioration test on the GaN high electron mobility transistor, irradiating the GaN high electron mobility transistor in turns with a plurality of light sources with different wavelengths and measuring the plurality of electrical characteristics after each irradiation of the GaN high electron mobility transistor by each of the plurality of light sources, and comparing changes of the plurality of electrical characteristics measured in the above steps to determine the defect location of the GaN high electron mobility transistor.

Claims

1. A method for detecting defects in a GaN high electron mobility transistor comprising: measuring a plurality of electrical characteristics of a GaN high electron mobility transistor; measuring the plurality of electrical characteristics after performing a deterioration test on the GaN high electron mobility transistor; irradiating the GaN high electron mobility transistor in turns with a plurality of light sources with different wavelengths and measuring the plurality of electrical characteristics after each irradiation of the GaN high electron mobility transistor by each of the plurality of light sources; and comparing changes of the plurality of electrical characteristics that are measured to determine a defect location of the GaN high electron mobility transistor.

2. The method as claimed in claim 1, wherein the plurality of electrical characteristics is an on-state current and an initial voltage of the GaN high electron mobility transistor.

3. The method as claimed in claim 1, wherein one of the plurality of light sources emits a visible light within a wavelength range between 400 nm and 700 nm and is configured to incur a response at an interface between a silicon nitride layer and an aluminum gallium nitride layer of the GaN high electron mobility transistor.

4. The method as claimed in claim 1, wherein one of the plurality of light sources emits an ultraviolet light with a wavelength of 365 nm and is configured to incur a response at a gallium nitride layer of the GaN high electron mobility transistor.

5. The method as claimed in claim 1, wherein one of the plurality of light sources emits an ultraviolet light with a wavelength of 265 nm and is configured to incur a response at an aluminum gallium nitride layer of the GaN high electron mobility transistor.

6. The method as claimed in claim 1, wherein the GaN high electron mobility transistor comprises an electron supply layer laminated on a channel layer, a gate electrode located on the electron supply layer, and a passivation layer covering the electron supply layer and the gate electrode, wherein the defect location of the GaN high electron mobility transistor includes a power supply zone, a buffer zone, a passivation zone and a drift zone, wherein the power supply zone is located in the electron supply layer and under the gate electrode, the buffer zone and the drift zone are located in the channel layer, with the buffer zone located under the gate electrode and the drift zone located aside the buffer zone, and the passivation zone is located in the passivation layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

[0019] FIG. 1 is a lamination cross-sectional diagram of a defect location according to a preferred embodiment of the present invention.

[0020] FIG. 2 is a characteristic curve diagram of defect detection according to the preferred embodiment of the present invention.

[0021] FIG. 3 is a characteristic curve diagram of another defect location as compared with FIG. 2.

[0022] In the various figures of the drawings, the same numerals designate the same or similar parts. Furthermore, when the terms “top”, “bottom”, “increase”, “reduce”, “side” and similar terms are used hereinafter, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings, and are utilized only to facilitate describing the invention, rather than restricting the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0023] A method for detecting defects in GaN high electron mobility transistor according to a preferred embodiment of the present invention includes steps of performing a withstand voltage test on a GaN high electron mobility transistor, and irradiating the GaN high electron mobility transistor with several light sources in turn.

[0024] Referring to FIG. 1, the GaN high electron mobility transistor is sequentially stacked from bottom to top with a silicon substrate W, a buffer layer B, a channel layer 1, an electron supply layer 2 and a passivation layer 3. Both ends of the channel layer 1 and the electron supply layer 2 are respectively electrically connected to a source electrode S and a drain electrode D. A gate electrode G is further disposed on the electron supply layer 2. The passivation layer 3 covers the electron supply layer 2, the gate electrode G, the source electrode S, and the drain electrode D.

[0025] The defect location of the GaN high electron mobility transistor includes a power supply zone T1, a buffer zone T2, a passivation zone T3, and a drift zone T4. The power supply zone T1 is located in the electron supply layer 2 and under the gate electrode G, and the material of the power supply zone T1 may be aluminum gallium nitride (AlGaN). The buffer zone T2 and the drift zone T4 are located in the channel layer 1. The buffer zone T2 is located under the gate electrode G. The drift region T4 is located aside the buffer zone T2. The material of the buffer zone T2 and the drift zone T4 may be gallium nitride (GaN). The passivation zone T3 is located in the passivation layer 3, and the material of the passivation zone T3 may be silicon nitride (SiN).

[0026] Referring to FIGS. 1 and 2, gradually increasing gate voltages are provided to the gate electrode G of the GaN high electron mobility transistor, and the changes of the drain current at the drain electrode D are measured. When the gate voltage is greater than an initial voltage, the drain current begins to increase drastically. Further, the increasing trend of the drain current stabilizes when reaching a value of an on-state current. As shown in FIG. 2, the initial state of the GaN high electron mobility transistor is measured by an electrical test after the transistor is produced. The first initial voltage V.sub.T1 and the first on-state current I.sub.on1 of the transistor in the initial state may be obtained from the characteristic curve diagram recorded in the electrical test.

[0027] After obtaining the electrical characteristic of the GaN high electron mobility transistor in the initial state, the degradation test of the GaN high electron mobility transistor can be performed by placing the transistor in a harsh environment, such as 1.5 times the working voltage. Therefore, the transistor is forced to degrade in a short time, so as to predict the reliability and life of the transistor under normal working conditions. By analyzing the degraded transistor, the defect mode can be determined and serve as a reference for improving process. As shown in FIG. 2, the second initial voltage V.sub.T2 and the second on-state current I.sub.on2 of the transistor in the state after the deterioration test may be obtained again from the electrical test. Compared with the first initial voltage V.sub.T1 and the first on-state current I.sub.on1, the second initial voltage V.sub.T2 shifts in the positive direction, while the second on-state current Ione decreases.

[0028] In addition, photons can promote the escape of the carriers injected into the defects, so that the GaN high electron mobility transistor after deterioration can restore its electrical characteristics to a limited extent. As shown in FIG. 2, the third initial voltage V.sub.T3 and the third on-state current I.sub.on3 of the transistor in the state after irradiation and deterioration may be obtained again from the electrical test. The third on-state current I.sub.on3 is higher than the second on-state current I.sub.on2, but is still lower than the first on-state current I.sub.on1.

[0029] According to the changes in the electrical characteristic of the GaN high electron mobility transistor among the initial state, the state after the degradation test, and the state after irradiation, the defect locations can be determined. When a defect is located in the power supply zone T1 and the buffer zone T2, the caused changes in electrical characteristic are the drift of the initial voltage and the increasing or reducing of the on-state current. When the defect is located in the passivation zone T3 and the drift zone T4, the caused changes in electrical characteristic are the reducing and restoring of the on-state current. In addition, irradiating visible light with a wavelength range between 400 nm and 700 nm can incur a response at an interface between a silicon nitride layer and an aluminum gallium nitride layer. Irradiating the transistor with ultraviolet light with wavelength of 365 nm can incur a response at a gallium nitride layer. Irradiating the transistor with ultraviolet light with wavelength of 265 nm can incur a response at an aluminum gallium nitride layer. Thereby, carrier injection defects at the locations with the occurrence of light response can be reduced.

[0030] Referring to FIGS. 1 and 2, the second on-state current I.sub.on2 has reduced in the GaN high electron mobility transistor after the deterioration test. If the third on-state current I.sub.on3 increases after the irradiation by visible light, it can be determined that the defect is located in the passivation zone T3. If the third on-state current I.sub.on3 increases after the irradiation by ultraviolet light, it can be determined that the defect is located in the drift zone T4.

[0031] Referring to FIGS. 1 and 3, the second initial voltage V.sub.T2 has increased and the second on-state current I.sub.on2 has reduced in the GaN high electron mobility transistor after the deterioration test. If the third initial voltage V.sub.T3 reduces and the third on-state current Ion3 increases after the irradiation by ultraviolet light with wavelength of 365 nm, it can be determined that the defect is located in the buffer zone T2. If the third initial voltage V.sub.T3 reduces and the third on-state current I.sub.on3 increases after the irradiation by ultraviolet light with wavelength of 265 nm, it can be determined that the defect is located in the power supply zone T1.

[0032] Based on the above, the method for detecting defects in GaN high electron mobility transistor according to the present invention determines whether there are defects in the transistor and identifies the location distribution of the defects by irradiating lights of various wavelengths and measuring the electrical characteristic changes of the transistor, which can accurately determine the defects and distribution thereof, ensuring the effects of improving the process of component production and increasing the efficiency of product inspection.

[0033] Although the invention has been described in detail with reference to its presently preferable embodiments, it will be understood by one of ordinary skill in the art that various modifications can be made without departing from the spirit and the scope of the invention, as set forth in the appended claims.