600V-900V GaN-on-Si Process Technology for Schottky Barrier Diodes and Power Switches Fabricated in a Standard Si-Production Fab J.J.T.M. Donkers 1 , S.B.S. Heil 2 , G.A.M. Hurkx 1 , H. Broekman 3 , R. Delhougne 1 , J.A. Croon 2 , D.J. Gravesteijn 1 , J. Šonský 1 1 NXP Semiconductors Research, Kapeldreef 75, 3001 Leuven, Belgium 2 NXP Semiconductors Research, High Tech Campus 32, 5656 AA Eindhoven, The Netherlands 3 NXP Semiconductors Nijmegen, Gerstweg 2, 6534 AE Nijmegen, The Netherlands Tel: +31 24 353 4167, E-mail: johan.donkers@nxp.com Keywords: GaN, Au-free, HEMT, Schottky barrier, breakdown voltage, leakage current Abstract This paper describes a GaN-on-Si Schottky process technology being developed in one of NXP’s standard Si production fabs. It runs alongside standard Si-component manufacturing sharing the same production tools. It supports up to 900V-rated Schottky barrier diodes and power switches. Up to 8A-rated diodes and 100mΩ switches with breakdown voltage above 1000V are demonstrated. INTRODUCTION AND MOTIVATION Future high-efficiency power converters require fast switching, low conduction loss devices that can handle high voltages. GaN is a good candidate for voltages up to 1kV and shows excellent switching behavior in Schottky diodes and in High Electron Mobility Transistors (HEMTs). Thanks to the advancements in GaN-on-Si epitaxy, the industry is now actively combining III-V specific device expertise with low- cost high-volume Si main-stream production facilities [1]. Key issues to be resolved in GaN Schottky diodes and HEMTs are the reduction of leakage current, lagging behavior (dynamic R on or current collapse) and optimization of the electrical field distribution for high breakdown voltage. DEVICE PROCESSING NXP’s GaN-on-Si process technology is using Ti/Al-based ohmic contacts and Ni-based Schottky contacts. These are patterned in a silicon nitride passivation-first integration scheme by dry etching. Argon implantation is used for device isolation. Two Al-metal layers are used as interconnect and for high current routing. Plasma Enhanced Chemical Vapor Deposited (PECVD) silicon nitride layers are used as pre- metal and inter-metal dielectrics and final passivation. PROCESS CONTROL MONITORING During the process flow the following parameters are monitored for process control: ohmic contact resistivity ρ c , Schottky diode forward voltage V ca at 0.1A/cm 2 , reverse leakage current I r at 50V and diode ideality n. Circular TLM structures with varying metal to metal spacing were used to extract ρ c . Circular diode structures with varying anode- cathode spacing were used for the Schottky forward voltage, ideality and reverse leakage. Each measurement set was performed on 24 dies. Intermediate testing was done after (i) the ohmic module and device isolation; (ii) Schottky formation and contact opening; (iii) metal 1 and 2 aluminum back-end and (iv) final silicon nitride passivation. Typical measurements are shown in Fig. 1. Figure 1: (a) Ohmic contact resistivity in Ω·cm 2 , (b) Schottky diode forward voltage at 0.1A/cm 2 , (c) Schottky diode non-ideality versus die number at different stages of manufacturing. As can be seen from Fig. 1a, the ohmic contact resistivity varies across the wafer, but is very stable throughout the process. End-of-process ρ c ranges typically from 5×10 -6 to 1×10 -5 Ω·cm 2 , which corresponds to Contact resistivity ρ c (Ω·cm 2 ) Diode forward voltage V ca (V) Non-ideality factor n (-) Die number (c) (b) (a)