Apparatus for monitoring crystal growth

• US 4,277,441 A
• Filed: 03/17/1980
• Issued: 07/07/1981
• Est. Priority Date: 01/15/1979
• Status: Expired due to Term

• Current Assignee: ASE Americas Incorporated
• Original Assignee: Mobil Tyco Solar Energy Corporation
• Inventors: Sachs, Emanual M.
• Primary Examiner(s): Sever, Frank
• Application Number:
  US06/130,816
• Time in Patent Office: 477 Days
• Field of Search: 422/105, 422/248, 422/249, 358/139, 358/305, 156/600, 156/601, 156/617 R, 156/617 SP, 156/617 V
• US Class Current: 117/202
• CPC Class Codes: C30B 15/26 using television detectors; using photo or X-ray detectors
• CPC Class Codes: C30B 15/34 Edge-defined film-fed crystal-growth using dies or slits
• CPC Class Codes: Y10T 117/1008 with responsive control means
• CPC Class Codes: Y10T 117/1044 including means forming a flat shape [e.g., ribbon]

Abstract

A system and method are disclosed for monitoring the growth of a crystalline body from a liquid meniscus in a furnace. The system provides an improved human/machine interface so as to reduce operator stress, strain and fatigue while improving the conditions for observation and control of the growing process. The system comprises suitable optics for forming an image of the meniscus and body wherein the image is anamorphic so that the entire meniscus can be viewed with good resolution in both the width and height dimensions. The system also comprises a video display for displaying the anamorphic image. The video display includes means for enhancing the contrast between any two contrasting points in the image. The video display also comprises a signal averager for averaging the intensity of at least one preselected portions of the image. The value of the average intensity, can in turn be utilized to control the growth of the body. The system and method are also capable of observing and monitoring multiple processes.

Claims

1. A system for controlling the growth of a crystalline body of selected material from a growth pool of melt so that said body has a selected cross-sectional shape for some predetermined distance along its length, said growth pool being characterized by a meniscus which joins said body at said growth pool to form a solid/liquid/vapor junction, said system comprising

(1) means, including a crucible for heating said material, for establishing said growth pool,

(2) optical means for forming an image of at least the entire width of said junction and the portions of the body and meniscus above and below said junction;

(3) video display means for displaying said image, said video display means comprising

(a) means for generating a video signal representative of said image;

(b) averaging means for averaging the amplitudes of portions of the video signal representative of at least one preselected portion of said image, and

(c) means for generating an electrical signal representative of the average of said amplitudes; and

(4) means responsive to said electrical signal for controlling the growth of said body.

2. A system according to claim 1, wherein said means for generating said video signal includes means for generating an analog signal representative of said image and means for digitizing said analog video signal so as to produce a digitized video signal, and wherein said averaging means averages the amplitude of portions of the digitized video signal.

3. A system according to claim 2, wherein said means for digitizing said analog video signal comprises means for comparing the amplitude of said analog video signal with a predetermined threshold level and for providing said digitized video signal at a first signal level when said analog video signal exceeds the threshold level and at a second level when said analog video signal is below said threshold level.