Wafer Etching Scan Control for Uniform Center Removal
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Solution Overview
Problem
Existing semiconductor wafer etching methods struggle to control the surface shape uniformly, particularly at the central portion of the wafer, due to centrifugal forces removing etching liquid before it can effectively etch the surface.
Innovation Solution
A substrate processing method involving a reciprocating movement of the etching liquid supply above the substrate's rotation center, adjusting scan width and speed to ensure the etching liquid remains effective at the central portion, with specific control over rotation speed, scan speed, and scan-out position to maintain uniform etching across the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the substrate is rotated at high speed during etching, then the etching liquid is quickly removed from the central portion by centrifugal force, but this causes non-uniform etching distribution and poor surface shape control
Solution Approach 1:
The patent applies dynamics by implementing a reciprocating movement of the etching liquid supply in addition to the substrate rotation. The supply moves back and forth in the radial direction, creating a dynamic pattern where the etching liquid is supplied to different radial positions during each reciprocating cycle. This dynamic supply pattern ensures that the central portion receives adequate etching liquid despite centrifugal forces, while maintaining high rotation speed for productivity.
Solution Approach 2:
The reciprocating movement of the etching liquid supply creates a periodic action pattern. The supply oscillates between inward and outward movements in synchronization with the substrate rotation, providing etching liquid to the central portion at regular intervals. This periodic replenishment counteracts the continuous centrifugal removal effect, achieving uniform etching distribution while maintaining high rotation speeds.
2Device complexity
If the etching liquid supply is stationary above the rotation center, then the equipment is simple, but the etching liquid is removed by centrifugal force before effective etching occurs
Solution Approach 1:
The supply mechanism is transformed from a stationary position to a dynamic reciprocating movement. The supply moves radially inward and outward in a controlled manner, creating a dynamic supply pattern that adapts to the centrifugal force field. This dynamic movement adds complexity to the device but is the minimal necessary change to achieve uniform etching while maintaining high rotation speeds.
3Speed
If the reciprocating movement speed is increased, then the etching liquid is replenished faster at the central portion, but the scan width must be optimized to maintain etching liquid residence time
Solution Approach 1:
The patent applies parameter changes by establishing specific relationships between reciprocating speed, scan width, and substrate rotation speed. The reciprocating speed is set within a specific range (0.1 to 10 mm/s) and the scan width is optimized accordingly to ensure that the etching liquid remains on the substrate surface for an adequate residence time. This parameter optimization allows faster reciprocating movement while maintaining sufficient etching liquid contact time for uniform etching.
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 approach allows for precise control of the surface shape post-etching, achieving uniform etching distribution and improved flatness by maintaining etching liquid flow at the central portion, thus addressing the non-uniformity issues in conventional methods.
Implementation Method 1
a first time taken for the etching liquid supply that has passed the rotation center to pass the rotation center again after turning around at the end of the reciprocating movement becomes shorter than a second time taken for the etching liquid supplied to the rotation center to be removed to an outer peripheral portion of the substrate by a centrifugal force caused by a rotation of the substrate
Data Source
AI summary
A substrate processing method of processing a substrate includes etching a first surface of the substrate by supplying an etching liquid containing at least hydrofluoric acid and nitric acid onto the first surface. The etching of the first surface includes determining a scan width as a distance between return points set at both ends of a reciprocating movement, and a scan speed at which an etching liquid supply is reciprocated such that a first time taken for the etching liquid supply that has passed a rotation center to pass the rotation center again after turning around at the end of the reciprocating movement becomes shorter than a second time taken for the etching liquid supplied to the rotation center to be removed to an outer peripheral portion of the substrate by a centrifugal force; and etching the first surface with the determined scan width and the determined scan speed.