Susceptor for float-zone apparatus

• US 6,251,182 B1
• Filed: 05/11/1993
• Issued: 06/26/2001
• Est. Priority Date: 05/11/1993
• Status: Expired due to Term

• Current Assignee: Hemlock Semiconductor Corporation (Corning Incorporated)
• Original Assignee: Hemlock Semiconductor Corporation (Corning Incorporated)
• Inventors: Luna, Joaquin Enrique, Wheelock, Scott Allen
• Primary Examiner(s): HITESHEW, FELISA CARLA
• Application Number:
  US08/060,767
• Time in Patent Office: 2,968 Days
• Field of Search: 233/01, 156/603, 156/604, 156/608, 156/DIG.98, 422/245, 422/246
• US Class Current: 117/49
• CPC Class Codes: C30B 13/20 by induction, e.g. hot wire technique C30B13/18 takes precedence

Abstract

The present invention is an improved susceptor for a float-zone apparatus for the float-zone processing of silicon elements. The susceptor is of a cylindrical design which allows the susceptor to be positioned around a free end of a silicon element to heat the free end of the silicon element to facilitate inductive coupling of the free end of the silicon element with an RF induction coil heater. In a preferred embodiment of the present invention, the susceptor is formed from tantalum.

Claims

1. In combination with a float-zone apparatus for processing a silicon element, the apparatus having an RF induction coil heater and an element holder and a seed holder aligned vertically above and below the RF induction coil heater, the element holder being adapted to hold one end of a silicon element and the seed holder being adapted to hold a seed crystal of silicon, means for positioning the element holder relative to the RF induction coil heater to bring the free end of the silicon element into proximity with the RF induction coil heater to melt the free end of the silicon element forming a molten zone, and means for positioning the seed holder relative to the RF induction coil heater so that the seed crystal contacts and fuses with the molten zone, and means for varying the relative position of the RF induction coil heater to the silicon element such that the molten zone is moved along the length of the silicon element, the improvement comprising:

a cylindrical susceptor positionable around the free end of the silicon element.

2. A float-zone apparatus according to claim 1, where the cylindrical susceptor is formed from a material selected from a group consisting of carbon, graphite, silicon carbide coated carbon or graphite, molybdenum, tungsten, and tantalum.

3. A float-zone apparatus according to claim 1, where the cylindrical susceptor is formed from tantalum.

4. A float-zone apparatus according to claim 1, where the cylindrical susceptor is formed from tantalum and the cylindrical susceptor has a wall thickness within a range of about 0.3 mm to 5 mm.

5. A float-zone apparatus according to claim 1, where the cylindrical susceptor is formed from tantalum and the cylindrical susceptor has a wall thickness within a range of about 0.5 mm to 1.5 mm.

6. In combination with a float-zone apparatus for processing a semiconductor grade silicon element of irregular shape, the apparatus having an RF induction coil heater and an element holder and a seed holder aligned vertically above and below the RF induction coil heater, the element holder being adapted to hold one end of the semiconductor grade silicon element and the seed holder being adapted to hold a seed crystal of monocrystalline silicon, means for positioning the element holder relative to the RF induction coil heater to bring the free end of the semiconductor grade silicon element into proximity with the RF induction coil heater to melt the free end of the semiconductor grade silicon element forming a molten zone, and means for positioning the seed holder relative to the RF induction coil heater so that the seed crystal contacts and fuses with the molten zone, and means for varying the relative position of the RF induction coil heater to the silicon element such that the molten zone is moved along the length of the semiconductor grade silicon element, the improvement comprising:

a tantalum cylindrical susceptor positionable around the free end of the semiconductor grade silicon element of irregular shape.

7. In a method for float-zone processing of a semiconductor grade silicon element of irregular shape in a float-zone apparatus, the improvement comprising:

positioning a tantalum cylindrical susceptor around a free end of a semiconductor grade silicon element of irregular shape and heating the cylindrical susceptor by RF inductive coupling to an RF induction coil heater to provide radiant heat to the free end of the silicon element and thereby facilitating coupling of the RF induction coil heater to the silicon element.