Structure and method for improving thermal stability and reliability of ohmic contact of N polar surface GaN

Abstract

The invention relates to a structure for improving ohmic contact performance of an N-polar surface GaN. The structure comprises a GaN material, a TiN thin layer (2) covering an epitaxial layer (1) ofthe N-polar surface GaN of the GaN material, and a metal laminated layer (3) covering the TiN thin layer (2). The invention has the following beneficial effects that the TiN thin layer has the advantages of high melting point, low work function and the like; the TiN thin layer can form a stable contact interface with the N-polar surface GaN under the condition of high temperature, so that the reaction between the ohmic contact metal and the N-polar surface GaN material is effectively inhibited, and after the ohmic metal layer is annealed in the atmosphere of protective gas, ohmic contact degradation cannot be caused, and better ohmic contact characteristics can be formed. According to the invention, the thermal stability of the ohmic contact of the N-polar surface GaN is improved, and thespecific contact resistivity of the ohmic contact of the N-polar surface GaN is reduced, so that the overall performance of the device is improved. The method is simple in process and high in repeatability and reliability.

Description

technical field [0001] The invention relates to the field of GaN semiconductor device technology, in particular to a method for using TiN with good thermal stability as an N-polar surface GaN ohmic contact electrode to improve its stability. Background technique [0002] Gallium Nitride (GaN), as a third-generation semiconductor material, has become a research hotspot in the semiconductor field in recent years due to its advantages such as large band gap, high electron saturation rate, and large breakdown electric field. GaN lateral devices on the Ga surface have been gradually industrialized, and have great application prospects in high-frequency, high-power power electronic switching devices. The research on N-side GaN devices has not stopped. Using the polarization effect, the N-side AlGaN / GaN heterojunction can form 2DHG, thereby manufacturing p-channel devices, which can be integrated with n-channel devices to form CMOS devices. In addition, because the vertical device...

AI Technical Summary

Problems solved by technology

[0003] 1. The density of dangling bonds on the surface of N-polar GaN is high, and a large amount of oxygen or hydroxide is adsorbed. During the annealing process, metal oxides will be formed with traditional metal electrode materials, which will increase the contact barrier between the metal and GaN, and deteriorate the ohmic contact. The quality of the material affects the reliability of the device (Wang Xianbin, Wang Yingli, Zhao Zhengping. Ohmic contact of Ti / Al / Ni / Au on N-polar GaN[J]. Materials Herald, 2017,31(04):14-16.)

[0004] 2. The combination metal of Ti / Al / Ni / Au is usually used to make the ohmic contact electrode, in which the metal Al reacts with GaN to form AlN in the high-temperature molten state. For GaN on the Ga polar surface, the interface between AlN and GaN will form a high Concentration of two-dimensional electron gas, which is beneficial to improve the ohmic characteristics of Ga-face GaN, but for N-face GaN, due to the opposite polarity, the interface between AlN and GaN formed by high-temperature reaction will form two-dimensional hole gas, so that Poor ohmic contact characteristics (Zhi-Hong F, Xian-BinW, Li W, et al.Ti / Al based ohmic contact to as-grown N-polar GaN[J].ChinesePhysics Letters,2015,32(8):087102 .)

[0005] 3. After the commonly used ohmic contact electrode Ti / Al / Ni / Au is annealed at high temperature, the surface morphology will deteriorate, which will not only affect the ohmic contact characteristics, but also have a negative impact on the subsequent process, such as contact exposure due to Surface roughness can cause large deviations in lithography

[0006] These problems lead to poor thermal stability of the GaN ohmic contact on the N-polar surface, and are easily affected by the subsequent manufacturing process of the device, such as: post-device annealing, etc., resulting in a decrease in device performance and reliability.

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