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Advanced Wet Silicone Etching by Controlling Oxygen and Other Gases

IP.com Disclosure Number: IPCOM000129025D
Published in the IP.com Journal: Volume 5 Issue 10A (2005-10-25)
Included in the Prior Art Database: 2005-Oct-25
Document File: 3 page(s) / 81K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

The following problems can occur in wet etching processes of α-Silicon: 1. Using the TEL POU tool (TEL, Tokyo Electron; POU, Point of Use) the selectivity of α-Silicon to implanted α-Silicon is too small. 2. An undesired signature formation on the wafer can occur. This probably results from hydrogen bubbles which are formed during α-Silicon etching block SSBS mask opening (SSBS, Single Sided Buried Strap) using the TEL POU tool. Until now the first problem is solved by increasing the SSBS BF2 implantation dose, but higher implantation dose could lead to an undesired boron penetration and/or more scattering, resulting in a lower non implanted α-Silicon etch rate. For the second problem a solution actually is not available. In the following a solution for the abovementioned problems is proposed. The core of the proposal is to control the concentration of oxygen and other gases during the etching process. During etching processes the following main reactions proceed: I) Si + 4OH- → Si(OH)4 + 4e- II) 4H2O + 4e-→ 4OH- + 2H2↑ or O2 + 2H2O + 4e-→ 4OH- The reaction II) can be controlled by the concentration of dissolved oxygen in the water/ammonia solution. For the controlling of oxygen concentration it is proposed to put a lid onto the TEL POU tank during the processing. This leads to

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Advanced Wet Silicone Etching by Controlling Oxygen and Other Gases

Idea: Kevin Huang, DE-Dresden; Martin Welzel, DE-Dresden

The following problems can occur in wet etching processes of α-Silicon:

1. Using the TEL POU tool (TEL, Tokyo Electron; POU, Point of Use) the selectivity of α-Silicon to implanted α-Silicon is too small.
2. An undesired signature formation on the wafer can occur. This probably results from hydrogen bubbles which are formed during α-Silicon etching block SSBS mask opening (SSBS, Single Sided Buried Strap) using the TEL POU tool.

Until now the first problem is solved by increasing the SSBS BF2 implantation dose, but higher implantation dose could lead to an undesired boron penetration and/or more scattering, resulting in a lower non implanted α-Silicon etch rate. For the second problem a solution actually is not available.

In the following a solution for the abovementioned problems is proposed. The core of the proposal is to control the concentration of oxygen and other gases during the etching process.

During etching processes the following main reactions proceed:
I) Si + 4OH- → Si(OH)4 + 4e-
II) 4H2O + 4e-→ 4OH- + 2H2↑ or O2 + 2H2O + 4e-→ 4OH-

The reaction II) can be controlled by the concentration of dissolved oxygen in the water/ammonia solution. For the controlling of oxygen concentration it is proposed to put a lid onto the TEL POU tank during the processing. This leads to

- a decreased oxygen concentration and a significantly increased selectivity of α-Silicon to implanted α-Silicon (see problem 1.) and - a decreased formation of undesired signatures on the wafer. A decreasing oxygen concentration the water/ammonia solution has an increasing capability to dissolve gaseous hydrogen (see...