An improved system based on the Czochralski process for continuous growth of a single crystal ingot comprises a low aspect ratio, large diameter, and substantially flat crucible, including an optional weir surrounding the crystal. The low aspect ratio crucible substantially eliminates convection currents and reduces oxygen content in a finished single crystal silicon ingot. A separate level controlled silicon pre-melting chamber provides a continuous source of molten silicon to the growth crucible advantageously eliminating the need for vertical travel and a crucible raising system during the crystal pulling process. A plurality of heaters beneath the crucible establish corresponding thermal zones across the melt. Thermal output of the heaters is individually controlled for providing an optimal thermal distribution across the melt and at the crystal/melt interface for improved crystal growth. Multiple crystal pulling chambers are provided for continuous processing and high throughput.

System for continuous growing of monocrystalline silicon

A system and process for growing extremely high quality single crystal materials, particularly silicon and other semiconductor materials, containing a generally uniform distribution of dopants, impurities, and oxygen, both axially and radially, wherein the concentration of impurities and oxygen and the number of defects are minimized. A significant feature is the use of a shallow tray-like crucible consisting of a replenishment zone and at least one crystal growth zone independently heated by one or more heating elements through the bottom of the crucible. In the preferred embodiment, an oval shaped crucible is used which consists of one replenishment zone and one growth zone. In one embodiment, a spiral shaped heater is centered underneath the feed rod and growing crystal and a "picture frame" shaped heater is located underneath the outer edges of the replenishment and growth zones to provide a more controlled thermal gradient. Mechanical pumping produces a controlled, directed, three-dimensional flow within the melt from the replenishment zone to the growth zone. The pumping is achieved either by rotation of a solid feed rod in the replenishment zone or by a strong directed flow of an inert gas onto the surface of the melt. Guide elements positioned within the crucible assist in directing the pumped flow from the replenishment zone to the growth zone so that the flow sweeps through the growth zone under the crystal to produce a thin boundary layer at the growing crystal surface, uniformly mixes in the dopant, and removes any impurity build up in the growth zone. Optionally, magnets to increase apparent melt viscosity and improve flow control and separate dopant addition mechanisms may be utilized.

System for growth of single crystal materials with extreme uniformity in their structural and electrical properties

A method for automatically controlling growing a single crystal neck portion by the CZ method, comprising the steps of pulling up a seed crystal (30) at 2 mm/min. for five minutes so as to grow a single crystal 32; next measuring a diameter of the lower end of the crystal; modifying an electric power for heating a melt based on the difference between the measured diameter and a reference value; waiting for five minutes; keeping the electric power constant for 10 minutes with controlling the pulling up speed so as to approach the diameter of the crystal to the reference value and with measuring the pulling up speed repeatedly; and next modifying the power based on the difference between the mean speed and a reference value. The last two steps are repeated alternatively.

Method of automatic control of growing neck portion of a single crystal by the CZ method

A heat shield for use in a crystal puller around a monocrystalline ingot grown out of a crucible in the crystal puller filled with molten semiconductor source material. The heat shield includes a reflector having a central opening sized and shaped for surrounding the ingot as the ingot is grown to reduce heat transfer from the crucible. The reflector is adapted to be surpported in the crystal puller between the molten material and a camera aimed toward at three separate points on a meniscus formed between the ingot and an upper surface of the molten material. The reflector has at least three passages extending through the reflector. Each of the passages is located along an imaginary line extending between the camera and one of the points on the meniscus. This permits the camera to view the points so the positions of the points can be determined by the camera for calculating the diameter of the ingot while minimizing heat loss through the passages.

Heat shield for crystal puller

A thermocouple vacuum sensor is provided, the thermocouple being surrounded by a gas or mixture of gases the pressure of which is to be measured. Cyclically the thermocouple is heated until its temperature reaches an upper temperature threshold. The thermocouple is subsequently cooled until its temperature reaches a lower temperature threshold. The heating time required to heat the thermocouple from the lower to the upper temperature threshold is measured. The cooling time required to cool the thermocouple from the upper temperature threshold to the lower temperature threshold may also be measured. The pressure surrounding the thermocouple may then be determined as a function of either the heating time, or the cooling time, or both.

Thermocouple vacuum gauge

The circumference of a crystal rod is monitored and controlled during the rod growing process by providing relative rotation between the growing crystal rod and a melt of the crystal material as the rod is being pulled from the melt according to the Czochralski method, and by using a radiation-sensitive control system for adjusting growth conditions of the rod in response to variations in a radiation signal which is indicative of the circumferential dimension of the rod. An electronic circuit integrates the radiation signal over each complete rotation of the rod, thereby eliminating unnecessary adjustment of the growth conditions in response to diametric variations of the rod which recur regularly in each rotation.

Method for circumferential dimension measuring and control in crystal rod pulling

Circumferential error signal apparatus for crystal rod pulling

A thermocouple pressure gauging system for measuring partial vacuum is provided which uses AC current to heat the thermocouple to constant temperature. A signal proportional to pressure is derived from the AC current needed to heat to constant temperature.

Richard A. Scholl

Papers

Method for circumferential dimension measuring and control in crystal rod pulling

Circumferential error signal apparatus for crystal rod pulling

Thermocouple vacuum gauge