Epitaxial Wafer Heating Ring for Edge Thickness Uniformity
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Solution Overview
Problem
Existing methods for depositing epitaxial layers on semiconductor wafers often result in uneven thickness at the edge due to varying growth rates caused by crystal orientation, requiring modifications to the susceptor or wafer shape.
Innovation Solution
A ring with inwardly projecting projections made of low IR transmittance material is positioned below the susceptor to selectively reduce thermal radiation intensity at specific edge regions, ensuring uniform growth rates by adjusting heating patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thermal radiation is applied uniformly to heat the semiconductor wafer during epitaxial deposition, then the wafer reaches deposition temperature, but the edge region exhibits non-uniform thickness due to varying growth rates caused by crystal orientation
Solution Approach 1:
The patent applies local quality by introducing a ring with selective radiation-blocking projections that create non-uniform heating zones. The ring blocks thermal radiation to specific angular ranges (15°-25°) corresponding to crystal orientation directions with higher growth rates, thereby locally reducing temperature in those edge regions to compensate for their inherently faster growth, achieving overall thickness uniformity across the wafer edge.
Solution Approach 2:
The patent changes the temperature parameter locally by using the ring structure to modulate thermal radiation intensity in specific angular directions. By blocking radiation in 15°-25° angular ranges, the temperature in corresponding edge subregions is reduced relative to other areas, transforming the uniform temperature field into a controlled non-uniform field that compensates for crystal orientation effects.
2Manufacturing precision
If the susceptor structure is modified to compensate for edge thickness variations, then thickness uniformity improves, but device complexity increases
Solution Approach 1:
The patent segments the radiation-blocking function into a separate ring component with discrete projections, rather than integrating complexity into the susceptor itself. The ring is held by susceptor support arms and can be independently positioned and adjusted, allowing the susceptor to remain simple while achieving thickness uniformity through the auxiliary ring structure that selectively blocks radiation in specific angular directions.
3Manufacturing precision
If the wafer edge region shape is modified to limit width, then thickness uniformity improves, but manufacturing flexibility decreases
Solution Approach 1:
The patent introduces the ring with radiation-blocking projections as an intermediary element between the heat source and the wafer. This mediator selectively attenuates thermal radiation in specific angular directions corresponding to problematic crystal orientations, allowing the wafer to maintain its standard shape and size while achieving uniform edge thickness through controlled differential heating.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Achieves uniform thickness of the epitaxial layer at the edge of semiconductor wafers without altering the susceptor or wafer shape, improving flatness and reducing thickness variations.
Implementation Method 1
heating of the semiconductor wafer to a deposition temperature by means of thermal radiation directed to a front and a back of the semiconductor wafer
Implementation Method 2
the ring segment being made of a material with low transmittance in the IR region of the spectrum
Implementation Method 3
heating of the semiconductor wafer to a deposition temperature by means of thermal radiation
Implementation Method 4
The deposition of an epitaxial layer on the front surface of a semiconductor wafer is typically achieved using chemical vapor deposition (CVD)
Data Source
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AI summary
The invention relates to a method and to a device for depositing an epitaxial layer on a front side of a semiconductor wafer of monocrystalline material. The method comprises the following: providing the semiconductor wafer; arranging the semiconductor wafer on a susceptor; heating the semiconductor wafer to a deposition temperature by means of thermal radiation, which is directed at a front side and at a rear side of the semiconductor wafer; conducting a deposition gas across the front side of the semiconductor wafer; and selectively reducing the intensity of a component of the thermal radiation directed at the rear side of the semiconductor wafer, whereby first portions at the edge of the semiconductor wafer, in which first portions a growth rate of the epitaxial layer is greater than in adjacent second portions in the case of uniform temperature of the semiconductor wafer because of the orientation of the monocrystalline material, are heated less intensely.