Surface passivation of InGaP/GaAs HBT using silicon-nitride film deposited by ECR–CVD plasma

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• 作者：L.T. Manera ; L.B. Zoccal ; J.A. Diniz ; P.J. Tatsch ; I. Doi
• 关键词：Silicon-nitride film ; Passivation ; ECR– ; CVD plasma ; HBT
• 刊名：Applied Surface Science
• 出版年：2008
• 期刊代码：6_01694332
• 类别：ms
• 出版时间：30 July 2008
• 卷：254
• 期：19
• 页码：6063-6066
• 文件大小：413 K

摘要

In this paper we have developed a passivation technique with silicon-nitride (SiN_X) film that requires no surface pre-treatment, and is fully compatible to monolithic microwave integrated circuits (MMICs). The nitride depositions were carried out by ECR–CVD (electron cyclotron resonance–chemical vapor deposition) directly over InGaP/GaAs heterojunction structures, which are used for heterojunction bipolar transistors (HBTs). Optical emission spectrometry (OES) was used for plasma characterization, and low formation of H and NH molecules in the gas phase was detected at pressure of 2.5 mTorr. These molecules can degrade III–V semiconductor surfaces due to the preferential loss of As or P and hydrogen incorporation at the substrate. The substrates were cleaned with organic solvents using a Sox-let distillate. The ECR depositions were carried out at a fixed substrate temperature of 20 °C, SiH₄/N₂ flow ratio of 1, Ar flow of 5 sccm pressure of 2.5 mTorr and microwave (2.45 GHz) power of 250 W and RF (13.56 MHz) power of 4 W. We have applied this film for InGaP/GaAs HBT fabrication process with excellent results, where two major contribuiton is related to this passivation technique, the enhancement in the transistor dc gain β and the improvement in the signal-to-noise ratio when compared unpassivated and passivated devices.