Electrostatic Chuck Cold-Edge Layout for Wafer Edge Temperature Control
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Solution Overview
Problem
Current electrostatic chuck (ESC) designs for plasma etching processes lack effective temperature control, leading to non-uniformity in wafer etching and increased costs due to complex heater configurations and high temperatures at the wafer edges, which affect etch rate and profile.
Innovation Solution
The ESC design incorporates a base plate with cooling channels and a thin bond layer, along with an inner and outer heating element, creating two temperature zones and a cold edge region through thermally conductive cooling, allowing for precise temperature control of the wafer edges by adjusting the chiller set-point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If multiple heaters are used to control temperature zones, then temperature control capability is improved, but device complexity increases
Solution Approach 1:
The heating system is segmented into two distinct temperature zones: a first temperature zone directly overlying the heater and a second temperature zone at the wafer edge. This segmentation allows independent temperature control in different regions, achieving sophisticated temperature management while using a single heater component rather than multiple heaters.
Solution Approach 2:
The patent creates different thermal conditions in different spatial locations. The wafer center region experiences heating from the heater, while the wafer edge region is intentionally cooled to a lower temperature. This local quality differentiation enables precise control of etch profiles by maintaining warm temperatures at the center and cool temperatures at the edges.
2Productivity
If high temperatures are maintained at wafer edges, then etch rate is improved, but etch uniformity deteriorates
Solution Approach 1:
The patent implements periodic or pulsed heating cycles where the heater is activated during specific phases of the etch process and deactivated during other phases. During heating phases, the entire wafer including edges receives thermal energy to maintain etch rate. During cooling phases, the heater is turned off, allowing natural thermal dissipation at the edges to improve uniformity. This temporal modulation resolves the contradiction between maintaining high edge temperatures for etch rate and allowing temperature reduction for uniformity.
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
This design improves etch rate and uniformity by maintaining the wafer edge temperature lower than other areas, reducing system complexity and costs by using fewer heaters, and enhancing the control of bottom critical dimension profiles.
Implementation Method 1
The plurality of cooling channels is disposed below the inner heating element, below the outer heating element, and below the annular heater setback region. Each of plurality of the cooling channels is configured to flow a cooling fluid to cause thermally conductive cooling in the annular heater setback region of the ceramic plate.
Implementation Method 2
The heater includes an inner heating element and an outer heating element. The inner heating element is arranged in a central circular area adjacent to the bottom surface of the ceramic plate and the outer heating element is arranged in an annular area that surrounds the central circular area and is adjacent to the bottom surface of the ceramic plate.
Data Source
AI summary
An electrostatic chuck is provided. In one example, the electrostatic chuck includes a base plate, a bond layer disposed over the base plate, a ceramic plate, and a heater. The ceramic plate includes a bottom surface disposed over the bond layer and a raised top surface for supporting a substrate. The raised top surface includes an outer diameter. The heater is disposed between the bottom surface of the ceramic plate and the bond layer. The heater element includes an inner heating element and an outer heating element. The inner heating element is arranged in a central circular area adjacent to the bottom surface of the ceramic plate and the outer heating element is arranged in an annular area that surrounds the central circular area and is adjacent to the bottom surface of the ceramic plate. An outer diameter of the outer heating element is inset from an annual heater setback region of the ceramic plate. The annular heater setback region is between the outer diameter of the raised top surface and the outer diameter of the outer heating element. The base plate includes a plurality of cooling channels. The plurality of cooling channels is disposed below the inner heating element, below the outer heating element, and below the annular heater setback region. Each of plurality of the cooling channels are configured to flow a cooling fluid to cause thermally conductive cooling in the annular heater setback region of the ceramic plate.