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Measuring the Layer Thickness of Extremely Thin SiO(2) Films

IP.com Disclosure Number: IPCOM000082820D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 21K

Publishing Venue

IBM

Related People

Bohg, A: AUTHOR [+2]

Abstract

This method for measuring the layer thickness of SiO(2) films with a layer thickness from 1 to 100 Angstrom consists in determining the quantity of copper separated out of an NH(4)F/NH(4)OH/CuSO(4).5H(2)O/solution, after the SiO(2) layer has been removed by etching. The layer thickness is computed on the basis of the time the sample spends in the etching solution minus the time required for separating the respective quantity of copper, and on the basis of the known etch rate of the etching solution. Method: Reagents: a) NH(4)F, crystalline, b) 25% aqueous Solution of NH(4)OH, c) concentrated nitric acid, d) CuSO(4) solution, 0.393 g CuSO(4) 5H(2)0 are dissolved in water and adjusted with water to 100 ml. Etching Solution: 40 g NH(4)F, 60 ml H(2)0, 0.

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Measuring the Layer Thickness of Extremely Thin SiO(2) Films

This method for measuring the layer thickness of SiO(2) films with a layer thickness from 1 to 100 Angstrom consists in determining the quantity of copper separated out of an NH(4)F/NH(4)OH/CuSO(4).5H(2)O/solution, after the SiO(2) layer has been removed by etching. The layer thickness is computed on the basis of the time the sample spends in the etching solution minus the time required for separating the respective quantity of copper, and on the basis of the known etch rate of the etching solution. Method:

Reagents:

a) NH(4)F, crystalline,

b) 25% aqueous Solution of NH(4)OH,

c) concentrated nitric acid,

d) CuSO(4) solution,

0.393 g CuSO(4) 5H(2)0 are dissolved in water and adjusted

with water to 100 ml.

Etching Solution:

40 g NH(4)F,

60 ml H(2)0,

0.5 ml of the above CuSO(4) solution, and

0.3 ml of the 25% aqueous solution of NH(4)OH.

A wafer with a surface of 25.6 cm/2/ and the SiO(2) layer thickness to be measured, is immersed in the etching solution after its rear side has been coated. After the SiO(2) layer has been removed by etching which is indicated by drops forming on the hydrophobic silicon surface, the wafer is taken from the etching solution and rinsed with distilled water. The etching time is accurately recorded.

The copper deposited on the stripped silicon surface after the SiO(2) layer has been removed by etching, is dissolved in nitric acid and analytically determined. The time required...