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Surface Optical Reflectance Process Monitor

IP.com Disclosure Number: IPCOM000088337D
Original Publication Date: 1977-May-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 5 page(s) / 53K

Publishing Venue

IBM

Related People

Kircher, CJ: AUTHOR [+2]

Abstract

A manufacturing process monitor is presented which utilizes changes in surface optical reflectance to measure changes in the character of the surface resulting from many possible sources (e.g., oxide growth, deposition and chemisorption). An incident laser beam and the reflected version thereof from the sample surface are compared to provide a signal indicative of the reflectance of the surface. The technique obtains sufficient stability in the measured reflectance that reflectance changes corresponding to films of submonolayer (as small as 0.02 Angstroms) thickness (as well as much thicker films) can be detected directly in real time. This sensitivity is also retained in spatially-resolved measurements of small portions of the surface on the order of 1-5 microns in size.

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Surface Optical Reflectance Process Monitor

A manufacturing process monitor is presented which utilizes changes in surface optical reflectance to measure changes in the character of the surface resulting from many possible sources (e.g., oxide growth, deposition and chemisorption). An incident laser beam and the reflected version thereof from the sample surface are compared to provide a signal indicative of the reflectance of the surface. The technique obtains sufficient stability in the measured reflectance that reflectance changes corresponding to films of submonolayer (as small as 0.02 Angstroms) thickness (as well as much thicker films) can be detected directly in real time. This sensitivity is also retained in spatially-resolved measurements of small portions of the surface on the order of 1-5 microns in size.

Essentially, the contribution of this article involves two parts. One part is the optical aspect by which a reflected beam is obtained from a sample and the difference between the reflected beam and the original beam provides a measure of the reflectance of the sample. In a process monitor, the changes in the sample reflectance provide a measure of the change in the process parameter at the surface. The reflectance properties at the surface of a sample are obtained by a capability of measuring changes in the reflectance to a very high level of accuracy sufficient to obtain information considerably better than one percent, even down to a hundredth of one percent.

The present technology has a number of advantages: (1) nondestructive reflectance monitor, (2) any surface (opaque or transparent), (3) high spatial resolution (1-5 microns) for circuitry element, (4) multiple process sensitive to (sub) monolayers (~0.02 Angstroms); thin oxide growth by thermal oxidation or sputtering, thin film deposition by evaporation or sputtering, adsorption by gas exposure or deposition, and (5) real-time monitor displaying reflectance changes directly. Furthermore, the practice of this technology obtains the following identified advantages: (1) Use of optical reflectance measurements for a process monitor of surface treatments of a sample in vacuum (effects in a transparent liquid cell at the solid liquid interface and in some cases at a solid/solid interface can also be studied). (2) Nondestructive optical monitor of sample surface condition having high spatial resolution (1-5 Microns), i.e., monitor only such a small section of sample surface e.g., a circuit element. (3) Highly simplified, easy-to-align, optical system for measurement of reflectance changes due to surface treatments. (4) Sensitivity to changes affecting as little as 0.02 Angstroms thickness at the surface or to thin films grown or deposited on the surface with similar thickness. (5) Results obtained directly and in real time.

The advantages over the ellipsometry technique are: (1) much easier alignment with much smaller errors resulting from misalignment; (2) much cheap...