Process for imaging laserinterferometry and a laserinterferometer for carrying out said process

• US 4,838,694 A
• Filed: 09/09/1987
• Issued: 06/13/1989
• Est. Priority Date: 01/08/1986
• Status: Expired due to Fees

• Current Assignee: Fraunhofer-Gesellschaft ZUR Forderung Der Angewandten Forschung EV
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Pelka, Joachim, Betz, Hans, Mader, Herman
• Primary Examiner(s): Willis, Davis L.
• Assistant Examiner(s): Koren, Matthew W.
• Application Number:
  US07/113,275
• Time in Patent Office: 643 Days
• Field of Search: 356/357, 156/626
• US Class Current: 356/504
• CPC Class Codes: G01B 11/0675 using interferometry

Abstract

The present invention relates to a laserinterferometric process, in particular, for use in etching thin layers, whereby a layer to be examined is radiated with a laser passing over a surface of the layer and the intensity of the reflected laser beam, which is composed of a beam reflected from the surface of the layer to be examined and one reflected from its lower interface is ascertained and evaluated by a data processing system from which the information concerning the layer to be examined is read out. The present invention also relates to an imaging laserinterferometer comprising a modulator, which deflects the laser beam, a detector for the reflected laser beam and a data processing systen, which analyzes the detector signals.

Claims

1. A laserinterferometric process for examining a thin layer on a substrate comprising:

radiating a specific surface of said thin layer to be examined by passing a laser beam over said specific surface;

deflecting said laser beam by an electrically modulated crystal onto said specific surface;

detecting the intensity of a reflected laser beam which is composed of a beam reflected from said specific surface and a beam reflected from the interface of said thin layer and said substrate;

evaluating said detected intensity in a data processing system; and

providing a readout of information concerning said layer to be examined.

2. A processing according to claim 1, including directing said laser beam over said specific surface by optics.

3. A processing according to claim 1, including focusing said laser beam to increase the resolution.

4. A process according to claim 1, including electronically evaluating said reflected beam for a desired point of the surface of the layer to be examined.

5. A process according to claim 4 for use in etching thin layer, including determining the etch rate for a desired point of the surface of the layer to be etched.

6. A process according to claim 4 for use in etching thin layers, including detecting the point of termination at a desired point of the surface of the layer to be examined.

7. A process according to claim 6, including determining the uniformity of the etch rate and the point of termination in the layer to be etched.

8. A process according to claim 4, including differentiating a layer to be etched from its surroundings.

9. A process according to claim 4, wherein said evaluating of said reflected laser beam is performed simultaneously with etching.

10. A process according to claim 1, including controlling a process with signals from the data processing system.

11. A process according to claim 1, including visually representing the information of said reflected laser beam.

12. A laserinterferometer for examination of a surface of a layer on a substrate comprising:

laser means for producing a laser beam;

modulator means including an electrically modulated crystal for deflecting said laser means on to said layer;

detector means for detecting reflected laser beams and providing detector signals; and

data processing means for analysis of said detector signals and providing a readout of information concerning said layer.

13. A laserinterferometer according to claim 12, including a glass fiber optic means for guiding the laser beam to the surface to be examined.

14. A laserinterferometer according to claim 12, including a focusing optic means for focusing said laser beam on the surface to be scanned.

15. A laserinterferometer according to claim 12, including means for increasing the signal-to-noise ratio.

16. A laserinterferometer according to claim 12, including a display screen connect to the data processing means.

17. A laserinterferometer according to claim 12, including a plotter connected to the data processing means.

18. The use of said laserinterferometer according to claim 12, wherein said data processing means provides a process control signal.

19. A laserinterferometric process for examining a thin layer on a substrate comprising:

radiating a specific surface of said thin layer to be examined by passing a laser beam over said specific surface;

modulating the intensity of said laser beam with a fixed frequency;

detecting the intensity of a reflected laser beam in a narrow band about the modulating fixed frequency which is composed of a beam reflected from said specific surface and a beam reflected from the interface of said thin layer and said substrate;

evaluating said detected intensity in a data processing system; and

providing a readout of information concerning said layer to be examined.

20. A process according to claim 19, including deflecting said laser beam electro-mechanically onto said specific surface.

21. A process according to claim 19, including electronically separating detected modulated signals and suppressing noise using said separated signals.