Automatic Diameter Control

Because crystal growth is controlled solidification, I have spent a great deal of my career developing precision control techniques. I have designed and developed several Automatic Diameter Control (ADC) systems using both optical pyrometers and crystal weighing via a load cell. For one particularly complicated system, I developed a combined system using both optical and weight control.

I have developed both analog and digital ADC systems. I currently have an extremely sophisticated PC-based ADC program which is in use by a number of consulting clients (see table). This program runs on the Microsoft Windows and is developed on the LabVIEW platform.

A 100-mm diameter sapphire crystal grown as part of a technology transfer for an Ammono, Ltd., Warsaw Poland. Scale is in inches.

 Data Collection Sampling

The ADC program fully automates the entire crystal growth process from heat-up, melt equilibration, growth from seed diameter to full diameter, extraction of the crystal at the end of growth and cool-down. The only manual operation required is the initial dipping of the seed crystal and establishing equilibrium between the seed and melt.

The program has a graphical interface that allows the user to monitor the operation of the power supply (usually an induction heater), the weight of the crystal, the crystal diameter, the growth rate and other parameters.

The ADC program collects a large amount of data in a Microsoft Excel formatted file which can subsequently be graphed and analyzed to monitor, control and refine the crystal growth process.

The table below shows a sample of the data collected during a typical crystal growth run. Following that is a graph of data from the growth of a 100 mm diameter sapphire crystal. Typically I graph out six or seven parameters from a given data set in order to get a good sense of the functioning of the process and to identify process upsets that may lead to crystalline defects. The program has 64 user adjustable parameters that allow the user to customize the growth process to any particular material. These parameters include the solid density, liquid density, pull speed, rotation rate, heat-up time, cool-down time, as well as many others.

The ADC program has the capability to adjust both rotation rate and pull speed during the crystal growth process. These features can be used to modify the shape of the growth interface and to compensate for the melt drop rate during the growth of the top of the crystal. The program can also detect power failures and extract the crystal rapidly from the melt to prevent damage to the seed rotation mechanism. It is fully documented with a 72-page instruction manual.

Additional information as well as a demonstration version of the ADC program on a CD-ROM is available on request. Click here to request a copy.  (Client is deciding how this should work – will get back to you)

ADC Software Clients
Client Location
Ames Research Laboratories Ames, Iowa
Ammono, Ltd. Warsaw, Poland
Chungshan Institute of Science and Technology Taiwan
City University of New York New York, NY
Crystal Technology Palo Alto, California
Deltronic Crystal Industries Dover, New Jersey
Honeywell Specialty Materials* Victoria, B.C. Canada
North China Research Institute for Electro-Optics Beijing, China
Pennsylvania State University Freeport, Pennsylvania
SAES Getters Milan, Italy
SAES Opto Materials Sardinia, Italy
Saint-Gobain Crystals and Detectors** Washougal, Washington
Shanghai Advanced Silicon Technology Shanghai, China
Sino American Silicon Taiwan
Thermal Technology, Inc. Santa Rosa, California
Univeristy of Santiago de Compostela Santiago, Spain
Universal Technical Resource Services Butte, Montana
Universiti Teknologi Malaysia Johor, Malaysia
*now Silian Sapphire Corp.
**formerly Union Carbide Corporation