Linton Crystal Technologies has applied for a U.S. Utilities Patent for an Active Balancing Seed Lift/Rotate Mechanism for Czochralski furnaces. The new mechanism reduces the orbiting of the seed cable that contributes to defects in grown crystals.
“We are constantly working on innovations that will help customers grow higher quality crystals, more efficiently,” explains John Reese, mechanical engineering manager with LCT. “This patent-pending technology is the latest advancement that will help reduce factors that contribute to some of the most common crystal defects.”
The standard seed lift/rotate mechanism becomes imbalanced as the cable wrapping spool shifts away from the position where the unit was factory balanced. This is because the fixed counterweight on the mechanism cannot fully compensate for the weight of the spool shifting away from that position. This can contribute to defects such as crystal structure slip (loss of structure), fluctuating crystal diameter, a corkscrew shape of the crystal body (due to the cable orbit), and extended growth times from multiple melt backs.
“As the lifting capacity of the seed lift/rotate mechanisms have increased (450kg capacity in 2013 to 1000kg capacity in 2020), the rotating mass has also increased dramatically. At the same time, the crystal receiving chambers have increased in length from 3.5M to upward of 7M,” notes Joel Stefl, senior mechanical designer with LCT. “With this increase in rotating mass, the balance of the mechanism becomes more and more critical. As this chamber loses stability (or induces a vibration) the structural integrity of the growing crystal is impacted negatively.”
Linton’s new, Active Balancing Mechanism keeps the seed lift mechanism balanced during rotation and translation of the spool, dramatically reducing or eliminating the vibration created by a standard seed lift/rotate mechanism. The Mechanism uses an actively moving counterweight that shifts in the opposite direction of the spool’s translation travel. So, as the mass of the spool shifts left, the mass of the active counterweight moves right to counteract the mass shift of the spool. This in turn dramatically reduces, if not eliminates the “wobble” or vibration created by a standard seed lift/rotate mechanism.
The new mechanism will ship standard on all of Linton Crystal’s semiconductor CZ growers starting in 2021. It also will be available as an option on the company’s solar growers.
Linton Crystal Technologies is the world leader in the design, development, and manufacture of equipment for producing monocrystalline ingots for the semiconductor and solar industries. The company specializes in silicon and produces equipment for materials such as germanium and gallium arsenide. They also provide technical support, process engineering support, and replacement parts to help clients get businesses off the ground, improve productivity, and continue to innovate.