Ultra thin silicon wafers technology for mirror application

Artur Miros 1Bronisław Piątkowski Barbara Surma 2,3

1. Institute of Electronic Materials Technology, Silicon Department (ITME), Wólczynska 133, Warszawa 01-919, Poland
2. Institute of Electronic Materials Technology (ITME), Wólczyńska 133, Warszawa 01-919, Poland
3. Institute of Electron Technology (ITE), al. Lotników 32/46, Warszawa 02-668, Poland

Abstract

It has been postulated that silicon ultra-thin wafers (around 50 micron thick) should be one of the best material for application as a mirror for focusing He-atom beam in scanning helium microscope. The mirror is created by electrostatical deformation of silicon wafer passivated with hydrogen (Si(111)-H(1x1) surface). The bending force depends on the wafer thickness in 5th power. The aim of the project, the paper is involved in, is to increase the resolution from the nowadays achievable 1.5 µm to submicron range. For this application the silicon wafers with thickness around 50 microns and its variability all around the active area (used for the helium beam focusing) up to +/- 0.5micron are necessary. ,

The aim of this paper was to improve the technology for double-side polished wafers so as to meet these requirements. Two stage polishing process using double-sided polishing and one-sided polishing machines has been found to be optimized for ultra-thin wafers preparation. Such parameters as wax composition, its thickness and purity appeared to be the most important technological parameters for the achieving assumed geometrical parameters. The additional blocks for individual pressing of the wafer during sticking process were constructed and applied. The decisive and crucial factor in polishing process was getting of desirable shape of the thickness distribution.

Wafer thickness map was collected by optical confocal thickness and flatness measuring system, constructed within the confines of INA project. In spite of this the thickness value was controlled by using Fourier spectrophotometer and scanning microscope. Wafers with thickness distribution up +/- 0.6micron for focusing area as well as a satisfactory its distribution and surfaces shapes for the wafers has been achieved.

The project is funded by European Commission and Polish Ministry of Scientific Research under 6 FP EU - grant No. 509014 (INA)

 

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Presentation: Poster at Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth, by Artur Miros
See On-line Journal of Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth

Submitted: 2007-03-08 09:08
Revised:   2009-06-07 00:44