XeF2 Silicon etching system

Warning: XeF2 is toxic and dangerous; read material safety data sheet before using it!

Handle gently, and especially avoid any contact with water! XeF2 is a white powder, fumes are reactive, and it can react with water to form HF fumes: only handle in working and dry exhaust hood.

Contents

  1. Introduction
  2. Equipment description
  3. Operations instructions
  4. Photos gallery

I. Introduction

Isotropic and controlled chemical etching of Si on small samples with extreme selectivity to e.g. SiO2.

The tool operates in ‘pulsed’ mode; applying pulses of XeF2 gas for typically 30s with a pressure of typically 1000-2000 mTorr.

II. Equipment description

  • The XeF2 powder is contained in an short metal angled tube attached to the back of the etcher (on the outside). It has a manual valve to close it. Always keep this valve closed when the machine is not in use.
  • Computer-controlled valve 5 opens the XeF2 powder to the pulsing chamber (expansion chamber). This chamber can also be vented with nitrogen through computer-controlled valve 4.
  • Computer-controlled valve 3 lets XeF2 gas from the pulsing chamber into the etching chamber (sample chamber) in which the samples reside. This chamber is closed by a glass lid to allow for inspection of the samples during etching with the microscope.
  • The etching chamber can be vented (purged) with nitrogen through computer-controlled valve 2, and evacuated through computer-controlled valve 1 in combination with a manual valve (black knob on front). Note that the pump is only directly
    connected to the etching chamber. In order to evacuate the pulsing chamber, valve 3 must be additionally opened.
  • Valves 1-5 are controlled by a computer (default) or manually. There is a small switch panel on the left of the front of the machine. The ‘on’ switch should be in the down position to operate, and the ‘A’ switch should be in the up position to allow computer control of the valves. If the ‘A’ switch is in
    the down position, the 5 switches on the bottom row control the valves.
  • The software controlling the etcher is a labview script labeled ‘090123 – XeF2 etching.vi’ on the
    desktop. The camera is accessed usin WinTV2000.

III. Operation instructions

Detailed operations are available on this document.

IV. Photos gallery