Hough transform based CZ monocrystal silicon bar diameter measuring method

Abstract

The invention relates to a hough transformation- base method for measuring the diameter of vertical pulling single crystal silicon bar. It comprises following steps: collecting image during crystal growth, pretreating image, checking crystal growth information with Hough transforamtion and getting diameter, X coordinate for circle center and Y coordinate for circle center, average value clustering for space curve crossing point and getting accurate diameter measuring value. The invention employs one pick-up head and measures diameter for seeding and constant diameter process, the measuring accuracy is high and speed is fast.

Description

technical field [0001] The invention belongs to the technical field of photoelectric detection, and relates to a method for measuring the diameter of a silicon rod when the Czochralski method is used to produce single crystal silicon, in particular to an image measuring method for the diameter of a silicon rod with Hough transform as the core. Background technique [0002] As the main basic material of the semiconductor industry, silicon single crystal has played a pivotal role in the development of the semiconductor industry. At present, the Czochralski method is the main method for manufacturing single crystal silicon. In the process of manufacturing single crystal silicon by the Czochralski method, it is the basic requirement to ensure the growth of crystals with equal diameters. Therefore, accurate detection and automatic control of crystal diameters are key technologies to ensure crystal quality and yield. With the development trend of silicon wafer manufacturing to lar...

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Problems solved by technology

[0004] 1. The image acquisition method using "zoom lens" or "dual CCD system" is complex and costly

[0005] 2. Since the aperture image during crystal growth is a distorted and incomplete ring, in order to achieve reliable detection, traditional image processing methods require the lowest point of the arc in the image as the positioning reference. This requirement applies to the observation window and diversion barrel of the single crystal furnace The design brings a lot of inconvenience

[0006] 3. In order to reflect the strong radiant heat in the furnace, the quartz glass of the camera observation window must be metal-coated

Since the time interval of the interference is similar to the time constant of the natural change of the diameter signal, the low-pass filter based on the frequency difference will cause a large lag in the measurement signal, resulting in a decrease in the quality of the diameter control during the approach process

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