US-12628364-B2 - High electron mobility transistor and method for fabricating the same

US12628364B2US 12628364 B2US12628364 B2US 12628364B2US-12628364-B2

Abstract

A method for fabricating high electron mobility transistor (HEMT) includes the steps of: forming a buffer layer on a substrate; forming a first barrier layer on the buffer layer; forming a first hard mask on the first barrier layer; removing the first hard mask and the first barrier layer to form a recess; forming a second barrier layer in the recess; and forming a p-type semiconductor layer on the second barrier layer.

Inventors

Chun-Ming Chang
Che-Hung Huang
Wen-Jung Liao
Chun-Liang Hou

Assignees

UNITED MICROELECTRONICS CORP.

Dates

Publication Date: 20260512
Application Date: 20231225
Priority Date: 20191009

Claims (7)

1 . A method for fabricating high electron mobility transistor (HEMT), comprising: forming a buffer layer on a substrate; forming a first barrier layer on the buffer layer; forming a first hard mask on the first barrier layer; patterning the first hard mask made of a dielectric material, the first barrier layer, and the buffer layer to form a MESA isolation, wherein the first hard mask, the first barrier layer, and an upper portion of the buffer layer comprises a first width and a lower portion of the buffer layer comprises a second width; forming a second hard mask on a top surface of the first hard mask and sidewalls of the first hard mask, the first barrier layer, and the buffer layer; removing the first hard mask and the first barrier layer to form a recess; forming a second barrier layer in the recess while the first hard mask is on the first barrier layer and sidewalls of the first hard mask and the second barrier layer are aligned; and forming a p-type semiconductor layer on the second barrier layer and directly contacting the first hard mask, wherein a topmost surface of the first hard mask is lower than a top surface of the p-type semiconductor layer.
2 . The method of claim 1 , further comprising: forming the second barrier layer in the recess; forming the p-type semiconductor layer on the second barrier layer; removing the second hard mask; forming a passivation layer on the first hard mask; forming a gate electrode on the p-type semiconductor layer; and forming a source electrode and a drain electrode adjacent to two sides of the gate electrode.
3 . The method of claim 1 , wherein the first barrier layer and the second barrier layer comprise Al x Ga 1-x N.
4 . The method of claim 3 , wherein the first barrier layer and the second barrier layer comprise different concentrations of Al.
5 . The method of claim 3 , wherein a concentration of Al of the second barrier layer is less than a concentration of Al of the first barrier layer.
6 . The method of claim 1 , wherein a thickness of the second barrier layer is less than a thickness of the first barrier layer.
7 . The method of claim 1 , wherein sidewalls of the p-type semiconductor layer and the second barrier layer are aligned.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation application of U.S. application Ser. No. 17/745,841, filed on May 16, 2022, which is a division of U.S. application Ser. No. 16/666,414, filed on Oct. 29, 2019. The contents of these applications are incorporated herein by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a high electron mobility transistor (HEMT) and method for fabricating the same. 2. Description of the Prior Art High electron mobility transistor (HEMT) fabricated from GaN-based materials have various advantages in electrical, mechanical, and chemical aspects of the field. For instance, advantages including wide band gap, high break down voltage, high electron mobility, high elastic modulus, high piezoelectric and piezoresistive coefficients, and chemical inertness. All of these advantages allow GaN-based materials to be used in numerous applications including high intensity light emitting diodes (LEDs), power switching devices, regulators, battery protectors, display panel drivers, and communication devices. SUMMARY OF THE INVENTION According to an embodiment of the present invention, a method for fabricating high electron mobility transistor (HEMT) includes the steps of: forming a buffer layer on a substrate; forming a first barrier layer on the buffer layer; forming a first hard mask on the first barrier layer; removing the first hard mask and the first barrier layer to form a recess; forming a second barrier layer in the recess; and forming a p-type semiconductor layer on the second barrier layer. According to another aspect of the present invention, a method for fabricating high electron mobility transistor (HEMT) includes the steps of: forming a buffer layer on a substrate; forming a barrier layer on the buffer layer; forming a first hard mask on the barrier layer; forming a second hard mask on the first hard mask; removing the second hard mask and the first hard mask to form a recess; and forming a p-type semiconductor layer on the barrier layer. According to yet another aspect of the present invention, a high electron mobility transistor (HEMT) includes: a buffer layer on a substrate; a p-type semiconductor layer on the buffer layer; a first barrier layer between the buffer layer and the p-type semiconductor layer; a second barrier layer adjacent to two sides of the first barrier layer, wherein the first barrier layer and the second barrier layer comprise different thicknesses; a gate electrode on the p-type semiconductor layer; and a source electrode and a drain electrode adjacent to two sides of the gate electrode on the buffer layer. These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1-5 illustrate a method for fabricating a HEMT according to an embodiment of the present invention. FIGS. 6-10 illustrate a method for fabricating a HEMT according to an embodiment of the present invention. DETAILED DESCRIPTION Referring to the FIGS. 1-5, FIGS. 1-5 illustrate a method for fabricating a HEMT according to an embodiment of the present invention. As shown in the FIG. 1, a substrate 12 such as a substrate made from silicon, silicon carbide, or aluminum oxide (or also referred to as sapphire) is provided, in which the substrate 12 could be a single-layered substrate, a multi-layered substrate, gradient substrate, or combination thereof. According to other embodiment of the present invention, the substrate 12 could also include a silicon-on-insulator (SOI) substrate. Next, a buffer layer 14 is formed on the substrate 12. According to an embodiment of the present invention, the buffer layer 14 is preferably made of III-V semiconductors such as gallium nitride (GaN), in which a thickness of the buffer layer 14 could be between 0.5 microns to 10 microns. According to an embodiment of the present invention, the formation of the buffer layer 14 could be accomplished by a molecular-beam epitaxy (MBE) process, a metal organic chemical vapor deposition (MOCVD) process, a chemical vapor deposition (CVD) process, a hydride vapor phase epitaxy (HVPE) process, or combination thereof. Next, a first barrier layer 16 is formed on the surface of the buffer layer 14. In this embodiment, the first barrier layer 16 is preferably made of III-V semiconductor such as aluminum gallium nitride (AlxGa1-xN), in which 0<x<1, x being less than or equal to 20%, and the first barrier layer 16 preferably includes an epitaxial layer formed through epitaxial growth process. Similar to the buffer layer 14, the formation of the first barrier layer 16 on the buffer layer 14 could be accomplished by a molecular-beam epitaxy (MBE) process, a metal organic chemical vapor deposition (MOCVD) process, a chemical vapor deposition