Device processing involving an optical interferometric thermometry using the change in refractive index to measure semiconductor wafer temperature

• US 5,229,303 A
• Filed: 12/13/1991
• Issued: 07/20/1993
• Est. Priority Date: 08/29/1989
• Status: Expired due to Term

• Current Assignee: AT&T, Inc.
• Original Assignee: AT&T, Inc.
• Inventors: McCaulley, James A., Donnelly, Vincent M. Jr.
• Primary Examiner(s): Hearn, Brian E.
• Assistant Examiner(s): EVERHART, BYRON S
• Application Number:
  US07/808,949
• Time in Patent Office: 585 Days
• Field of Search: 437/7, 437/8, 204/192.13, 204/192.33, 156/626, 156/627
• US Class Current: 438/7
• CPC Class Codes: G01K 11/00 Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00

Abstract

A method for fabricating a semiconductor device, which involves a technique for monitoring the temperature of the semiconductor substrate in which the device is formed, is disclosed. In accordance with the inventive technique, light, to which the substrate is substantially transparent, is impinged upon the substrate, and the intensity of either the reflected or transmitted light is monitored. If, for example, the intensity of the reflected light is monitored, then this intensity will be due to an interference between the light reflected from the upper surface of the semiconductor substrate and the light transmitted through the substrate and reflected upwardly from the lower surface of the substrate. If the temperature of the substrate varies, then the optical path length of the light within the substrate will vary, resulting in a change in the detected intensity. By comparing the detected intensity with intensities corresponding to known temperature variations, the temperature of the substrate is readily determined.

Claims

1. Method of manufacturing a semiconductor device, the method comprising

a) providing a semiconductor body having a first and a second major surface,

b) carrying out one or more processing steps on the body, at least one of the steps depending on the temperature of the body;

characterized in that the method further comprises

c) exposing the body to electromagnetic radiation and detecting radiation reflected from, or transmitted through, the body wherein said radiation undergoes interference;

d) monitoring the intensity variation with time through an extremum of the detected radiation as the temperature of the body changes during one of said processing steps to determine a value representative of said temperature based at least in part on the change of refractive index of said body with said temperature, the processing step to be carried out at a nominal processing temperature T_p ; and

e) controlling at least one of said processing steps in accordance with the result of step d).

2. Method of claim 1, wherein the method comprises comparing the intensity of the detected radiation with a known calibration target intensity associated with the temperature T_p.

3. Method of claim 1, wherein both major surfaces of the body are relatively smooth such that each surface specularly reflects at least 3% of said radiation that is incident thereon.

4. Method of claim 1, wherein the semiconductor body is a semiconductor wafer, and wherein the semiconductor comprises a material selected from the group consisting of Si, Ge, GaAs, InP, GaP, CdTe and InSb.

5. Method of claim 1, wherein said radiation is in the wavelength range 600 to 10,000 nm, and wherein the radiation is laser radiation.

6. Method of claim 1, wherein the intensity of the detected radiation is a function of the optical path length of the detected radiation in the semiconductor body, the optical path length being a function of the temperature of the body, with greater than 50% of the change of optical path length with temperature being due to a change of the refractive index of the body with temperature.

7. Method of claim 1, wherein a portion of the first major surface is exposed to the radiation, the portion being substantially but not exactly parallel to the second major surface, such that a plurality of spatial interference fringes are formed, a change in the temperature of the body resulting in a movement of the fringes;

wherein the method comprises sensing the direction of movement of the fringes, whereby the sense of the temperature change can be determined.

8. Method of claim 1, wherein the semiconductor body comprises a relatively thick first semiconductor substrate and at least one relatively thin second semiconductor layer, the second layer differing in composition and/or doping level from the first layer, step b) including changing the thickness of the second layer, wherein a property of said layer depends on the temperature of the body.

9. Method of claim 1, wherein said radiation is laser radiation.