Abstract: A method and system for controlling growth of a taper portion of a semiconductor single crystal based on the slope of the taper. A crystal drive unit pulls the growing crystal from a melt at a target pull rate that substantially follows an initial velocity profile for growing the taper. A controller calculates a taper slope measurement as a function of a change in crystal diameter relative to a change in crystal length. The controller then generates an error signal as a function of the difference between the taper slope measurement and a target taper slope and provides a pull rate correction to the crystal drive unit as a function of the error signal. In turn, the crystal drive unit adjusts the pull rate according to the pull rate correction to reduce the difference between the taper slope measurement and the target taper slope. The target taper slope is defined by a function having a generally exponential component and a generally linear component.

Abstract: A control method for use with a Czochralski crystal puller. The method includes pulling the growing crystal from the melt at a first target pull rate to grow a taper portion of the crystal and measuring the crystal diameter of the taper. The method also includes estimating a slope of the diameter as a function of a change in crystal diameter relative to time and the first target pull rate. The method further includes predicting a crystal diameter Di at which to initiate body growth from the taper as a function of the estimated slope. By increasing the pull rate to a second target pull rate when the measured crystal diameter reaches the predicted crystal diameter Di, the method controls growth of the crystal for transitioning from taper growth to body growth. The method also determines the second target pull rate as a function of the estimated slope when using a predefined diameter Di at which to initiate growth of the crystal body.

Abstract: An open loop control method for use with an apparatus for growing a silicon single crystal having a zero dislocation state and an improved diameter and growth rate uniformity in accordance with the Czochralski process. According to the invention, a heat and mass transfer model based on the silicon charged to a crucible is determined as a function of one or more reference parameters. The reference parameter values are determined from the growth of a reference silicon single crystal. A power profile is then determined as a function of the heat and mass transfer model for a given pull rate profile and model diameter profile. The power profile generated is representative of the power supplied to a heater for providing an amount of thermal energy to the crucible for substantially maintaining a thermal equilibrium at the interface between the melt and the crystal.

Abstract: A Czochralski method of producing a single crystal silicon ingot having a uniform thermal history from a silicon melt contained in a crucible coaxial with the ingot. In the process the pulling rate of the end-cone of the ingot is maintained at a relatively constant rate which is comparable to the pulling rate for the second half of the main body of the ingot. During the pulling of the end-cone of the crystal at a constant rate, the process may be further refined by, either independently or in combination, increasing the heat supplied to the melt, reducing the crystal rotation rate and/or reducing the crucible rotation rate. The second half of the main body of a single crystal silicon ingot grown in accordance with this process exhibits a relatively uniform axial concentration of flow pattern defects and amount of oxygen precipitated.

Abstract: Apparatus and methods for pulling a semiconductor crystal according to a Czochralski method are disclosed. The apparatus includes a crucible containing a melt, a crystal pulling mechanism which pulls the semiconductor crystal from the melt, a motor coupled to the crucible, and a control circuit for energizing the motor to rotate the crucible at a variable speed. The control circuit may energize the motor to rotate the crucible at a continuously varying acceleration and continuously varying rotational speed while the crystal pulling mechanism is pulling at least a portion of the semiconductor crystal from the melt in the crucible. The control circuit may also energize the motor to rotate the crucible at a rotational speed which monotonically increases and decreases.

Abstract: Apparatus and methods for pulling a semiconductor crystal according to a Czochralski method are disclosed. The apparatus includes a crucible containing a melt, a crystal pulling mechanism which pulls the semiconductor crystal from the melt, a motor coupled to the crucible, and a control circuit for energizing the motor to rotate the crucible at a variable speed. The control circuit may energize the motor to rotate the crucible at a continuously varying acceleration and continuously varying rotational speed while the crystal pulling mechanism is pulling at least a portion of the semiconductor crystal from the melt in the crucible. The control circuit may also energize the motor to rotate the crucible at a rotational speed which monotonically increases and decreases.