Particle Density of Pt Produced by Electroless Displacement Deposition on Single-crystalline Silicon

Abstract

By immersion of Si into a solution containing metal-salt and HF, fine metal particles are deposited onto the Si surface by electroless displacement reaction. The density of the deposited metal particles on the surface varies widely according to the metal-salt and Si pretreatment. The Pt particle density depends particularly strongly on the Si pretreatment. This study assessed the Pt electroless displacement deposition process. Single-crystalline n-Si （100） wafers were pretreated using the following three methods: immersion in a mixture of HF, HNO 3 , CH 3 COOH, and H 2 O （3:5:3:22 in volume） （ CP4A） , ordinary RCA method, and oxidization of the Si surface by immersion in HNO 3 after RCA （RCA＋ HNO 3 ） . The electroless displacement deposition of Pt particles onto the Si surface proceeds by immersion of Si wafers into a H 2 PtCl 6 solution containing HF for 5-900 s. On the Si surface pretreated using the CP4A method, Pt particles were deposited in the progressive mode. For the RCA method, Pt particles were deposited in two-stage progressive mode, which is separated at 180 s. For pretreatment of RCA＋HNO 3 , Pt particles deposited in two-stage progressive mode were separated at 120 s. These two-stage progressive modes result from the local anodic reaction, which dissolved the Si surface in electroless displacement deposition solution. However, irrespective of the pretreatment method, Pt particles were deposited on the order of 10 9 cm -2 particle density by deposition for 900 s.