Method and system for vertical gradient freeze 8 inch gallium arsenide substrates
AssigneeAXT, Inc.
InventorsWeiguo Liu, Rajaram Shetty, Wei Zhang
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Abstract
Methods and wafers for vertical gradient freeze 8 inch gallium arsenide (GaAs) substrates. In disclosed examples, vertical gradient freeze systems for forming gallium arsenide (GaAs) substrates having silicon as a dopant, the system includes a crucible to contain a GaAs liquid melt and seed material during a formation process; one or more heating coils arranged in a plurality of heating zones; and a pedestal to move relative to the crucible, the system operable to control heating of the plurality of heating zones and movement of the pedestal to form a single crystal GaAs substrate.
Claims18
A method for forming single crystal gallium arsenide substrates, the method comprising:
- sealing charge material comprising polycrystalline gallium arsenide (GaAs) liquid melt, B2O3 encapsulant, and carbon in a crucible;
- sealing the crucible in a quartz ampoule;
- performing a vertical gradient freeze crystal growth process by heating the ampoule using a multi-zone heating system to progressively melt the charge material until a portion of a seed crystal is melted, wherein each zone of the multi-zone heating system is enabled to heat the crucible at different temperatures, and wherein each zone of the multi-zone heating system includes two or more heating coils;
- moving a pedestal relative to the crucible through three or more zones of the multi-zone heating system, the system operable to control heating of the multi-zone heating system and movement of the pedestal;
- implementing controlled cooling of the multi-zone heating system during growth from the partially melted seed to form a single crystal 8 inch GaAs substrate;
- and
- controlling a shape of the interface to be concave to the melt utilizing cooling rates in the multi-zone heating system to form a solidified gallium arsenide crystal, wherein the shape of the interface is concave, such that the center is 5-20 mm lower than an edge of the substrate.
A method for forming single crystal gallium arsenide substrates, the method comprising:
- sealing charge material comprising polycrystalline gallium arsenide (GaAs) liquid melt, B2O3 encapsulant, and carbon in a crucible;
- sealing the crucible in a quartz ampoule;
- performing a vertical gradient freeze crystal growth process by heating the ampoule using a multi-zone heating system to progressively melt the charge material until a portion of a seed crystal is melted;
- moving a pedestal relative to the crucible, the system operable to control heating of the multi-zone heating system and movement of the pedestal;
- and
- implementing controlled cooling of the multi-zone heating system during growth from the partially melted seed;
- and
- controlling a shape of the interface to be concave to the melt utilizing cooling rates in the multi-zone heating system to form a solidified gallium arsenide crystal, wherein the shape of the interface is between 5-20 mm concave, such that the center is 5-20 mm lower than an edge of the substrate to form a single crystal 8 inch GaAs substrate.
Dependencies are inferred from the claim text.