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Planetary Evaporation System having Multiple Rotations

IP.com Disclosure Number: IPCOM000080755D
Original Publication Date: 1974-Feb-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 4 page(s) / 98K

Publishing Venue

IBM

Related People

Lee, MS: AUTHOR

Abstract

This is a program for calculating the thickness uniformity, evaporation intensity and quality of the step coverage of thin films, deposited on semiconductor wafers in a planetary evaporation system having multiple rotations. The program predicts the quality of evaporation by varying the following parameters: 1) Direction and rotational speed of each wafer, cluster of wafers and the dome supporting the clusters; 2) The number and position of the evaporation sources; and 3) Distance between sources and wafers. Fig. 1 illustrates an evaporation system having three degrees of rotation. Semiconductor wafers 1 rotate individually and independently of the other wafers. Each wafer is arranged in a cluster of five mounted on supports 2 which also rotate. Clusters 2 are mounted on the surface of revolving dome 4.

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Planetary Evaporation System having Multiple Rotations

This is a program for calculating the thickness uniformity, evaporation intensity and quality of the step coverage of thin films, deposited on semiconductor wafers in a planetary evaporation system having multiple rotations. The program predicts the quality of evaporation by varying the following parameters:
1) Direction and rotational speed of each wafer, cluster of wafers and the dome supporting the clusters;
2) The number and position of the evaporation sources; and
3) Distance between sources and wafers.

Fig. 1 illustrates an evaporation system having three degrees of rotation. Semiconductor wafers 1 rotate individually and independently of the other wafers. Each wafer is arranged in a cluster of five mounted on supports 2 which also rotate. Clusters 2 are mounted on the surface of revolving dome 4. Stationary sources 6 of the material to be deposited are located at the bottom of the dome at a distance `h' from surface 3. The distance from the evaporation sources to any point on a wafer is generally denoted as `r'.

Fig. 2 is a top view of the system illustrating the rotations of the dome, the cluster with respect to the dome and the wafers with respect to the cluster: w1, w2, and w3, respectively. From a surface point source of material 6, evaporation takes place from a small sphere so that the atoms are ejected normal to the surface. The thin-film deposition on point R of a wafer from all of the sources 6 during one complete revolution of dome 4 is:

(Image Omitted)

where:

d(C) - is the thickness of deposition for one revolution;

A - is the function of the particular evaporant material;

the symbols within the brackets represent the

distance from sources 6 to the particular point

on wafer 1 under consideration; and

w1 - is the rotational speed of dome 4 in radians/second.

To compare the thickness uniformity across each wafer, the total thickness d(T) deposited at the center of the wafer and at the edge of the wafer is compared.

An important measurement in evaporation systems, is the determination of whether steps within a wafer are exposed uniformly to the evaporation sources during the process. The steps in the wafers are those areas between...