Sumco Corporation

Sumco Phoenix Corporation

Aoti Operating Company, Inc

Benno Orschel

Keiichi Takanashi

Joel Kearns

Volker Todt

Andrzej Buczkowski

Fritz Kirscht

Bernd Srocka

Jan Helm

A method and apparatus for growing a semiconductor crystal include pulling the semiconductor crystal from melt at a pull speed and modulating the pull speed by combining a periodic pull speed with an average speed. The modulation of the pull speed allows in-situ determination of characteristic temperature gradients in the melt and in the crystal during crystal formation. The temperature gradients may be used to control relevant process parameters that affect morphological stability or intrinsic material properties in the finished crystal such as for instance the target pull speed of the crystal or the melt gap, which determines the thermal gradient in the crystal during growth.

Procedure for in-situ determination of thermal gradients at the crystal growth front

An improvement to a method and an apparatus for growing a monocrystalline silicon ingot from silicon melt according to the CZ process. The improvement performs defining an error between a target taper of a meniscus and a measured taper, and translating the taper error into a feedback adjustment to a pull-speed of the silicon ingot. The conventional control model for controlling the CZ process relies on linear control (PID) controlling a non-linear system of quadratic relationship defined in the time domain between the diameter and the pull-speed. The present invention transforms the quadratic relationship in the time domain between the diameter and the pull-speed into a simile, linear relationship in the length domain between a meniscus taper of the ingot and the pull-speed. The present invention applies a linear control (modified PID) which operates in the length domain, and controls a system that has a linear relationship between the ingot taper and the pull-speed in the length domain to control the diameter of a growing silicon ingot.

Method and apparatus for controlling diameter of a silicon crystal ingot in a growth process

The present invention provides a method and apparatus for controlling the growth of a silicon ingot in which the diameter of the growing silicon ingot can be accurately measured. A camera captures an image of the interface ring between the growing silicon ingot and the silicon melt. An image processor extracts local intensity maxima from the captured image, which are then digitized into an image data which comprises attributes of the pixels forming the local intensity maxima. An analyzer statistically analyzes the image data to derive parameters of an equation statistically simulating the interface ring. A probabilistic filter conducts the statistical analysis on the equation in which the respective pixels are weighted by their weight factors. The weight factor functions to attenuate the effect of noises caused by pixels which do not represent the interface ring. The statistical analysis may be repeated, using the renewed parameters, to progressively attenuate the effect of the noises to thereby obtain a satisfactorily accurate diameter of the silicon ingot.

Method and apparatus for controlling the growth process of a monocrystalline silicon ingot

A system and method correct crystal pulling motor speed deviations in a crystal pulling mechanism. In a first embodiment, a processor implements a tracking filter by estimating new filter state based on previous state and the since-then-travelled nominal distance, and then updating the filter state based on estimation error and filter gains which are also functions of the travelled nominal distance. In a second embodiment, a harmonic tracking filter suppresses residual harmonic modulation and allows a short time constant. Rapid variations of pulling speed may thus be corrected.

Method for correcting speed deviations between actual and nominal pull speed during crystal growth

A method of determining a diffusion length of a minority carrier in a material which includes applying a first excitation light having a first photon flux to a material, measuring a first surface photo voltage resulting from the application of the first excitation light, applying a second excitation light having a second photon flux to the material, measuring a second surface photo voltage resulting from the application of the second excitation light, applying a third excitation light having a third photon flux, having a predetermined ratio to the first photon flux, to the material, measuring a third surface photo voltage resulting from the application of the third excitation light, determining a diffusion length of a minority carrier in the material based on the measured first, second and third surface photo voltages.

Method for determining a minority carrier diffusion length using surface photo voltage measurements

For determining the dependence of a first measuring quantity (Y) on a second measuring quantity (P) the second measuring quantity (P) is periodically modified with a frequency (f ). The first measuring quantity (Y) changing accordingly is measured. From the obtained measuring signal of the first measuring quantity (Y) the components of the first measuring quantity (Y) are determined with at least a plurality of frequencies. From the components thus determined the first measuring quantity (Y) is reconstructed for at least a plurality of values of the second measuring quantity (P) by signal processing.

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Salem, OR, United States of America

Benno Orschel