• PDF / 320,795 Bytes
• 6 Pages / 585 x 783 pts Page_size
• 71 Downloads / 206 Views

DOWNLOAD

REPORT

---

Harry M. Meyer, III Microscopy, Microanalysis, and Microstructures Group, Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831

Husam H. Abu-Safe, Hameed Naseem, and W.D. Brown Department of Electrical Engineering, University of Arkansas, Fayetteville, Arkansas 72701 (Received 4 October 2005; accepted 14 December 2005)

A metal-induced crystallization (MIC) technique was used to produce large-grain poly-crystalline silicon. Two sets of samples were prepared by first sputtering Al onto glass substrates. For one set of samples, hydrogenated amorphous silicon (a-Si:H) was sputtered on top of the Al without breaking the vacuum. For the second set, the samples were taken out of the vacuum chamber and exposed to the atmosphere to grow a very thin layer of native aluminum oxide before sputter depositing the a-Si:H. Both sets of samples were then annealed at temperatures between 400 and 525 °C for 40 min. X-ray diffraction patterns confirmed the crystallization of the samples. Scanning Auger microanalysis was used to confirm that the a-Si:H and Al layers exchanged positions in this structure during the crystallization process. Auger mapping revealed the formation of large grain poly-silicon (10–20 ␮m). A model is proposed to explain how the crystallization process progresses with anneal temperature. I. INTRODUCTION

For the past several years, metal-induced crystallization (MIC) of a-Si has been receiving a significant amount of attention by researchers. The primary interest in poly-crystalline silicon (poly-Si) prepared by MIC is in the fabrication of thin film solar cells and thin film transistors.1 Because MIC poly-Si is prepared at low temperatures, it can be used to fabricate electronic devices on glass or flexible plastic substrates. Researchers have investigated the MIC of a-Si deposited using several different techniques and different constituent material deposition sequences. Of these various deposition techniques, plasma-enhanced chemical vapor deposition (PECVD) has been used extensively2–8 to prepare Al/a-Si:H/glass structures. Researchers have also studied a-Si/Al/glass structures using non-hydrogenated a-Si prepared by sputtering.9,10 The crystallization temperature in this case is above 450 °C, which is much higher than the case for hydrogenated a-Si in an as-deposited Al/a-Si:H/glass structure. At this crystallization (anneal) temperature, Al ends up as

a)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2006.0091 J. Mater. Res., Vol. 21, No. 3, Mar 2006

http://journals.cambridge.org

Downloaded: 01 Apr 2015

a top layer with poly-Si underneath the Al (as deposited structure was a-Si/Al/glass). This layer exchange is thought to occur by silicon diffusing through the Al and precipitating on top of the glass as a poly-Si layer.9 To explore large grain poly-crystalline Si formation, a study was carried out using the as-deposited structure a-Si:H/Al/glass. Both the Al and a-Si:H layers were deposited by sputtering. Marwan et al.11 rep