Workpiece Holder Vacuum Wetting for Semiconductor Wafer
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Solution Overview
Problem
Existing methods for electroplating on small features of semiconductor wafers face challenges in wetting due to cohesive forces, and previous vacuum impregnation techniques are difficult to implement without damaging the wafer by creating uneven pressure differentials.
Innovation Solution
A system that uses a workpiece holder with a ring to create a fluid seal and control pressure differentials between the front and back surfaces of the wafer, allowing for the introduction of a fluid to wet the surface while minimizing stress on the wafer, using a chamber that can be evacuated to reduce surface tension and promote uniform wetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If high-pressure spraying is used to wet small features, then fluid delivery is improved, but cohesive forces prohibit fluid from flowing into small features
Solution Approach 1:
The patent changes the pressure parameter from high-pressure spraying to reduced-pressure vacuum environment, which fundamentally alters the fluid behavior. By reducing the ambient pressure, the cohesive forces in the fluid are minimized, allowing the fluid to flow into small features without requiring high pressure that would cause splashing or uneven distribution.
Solution Approach 2:
The patent employs vacuum pressure (negative pressure) to deliver the fluid into small features. The vacuum pump creates a pressure differential that draws the fluid through the small features, replacing the traditional high-pressure hydraulic approach. This pneumatic method overcomes the cohesive forces that prevent fluid entry into micron-sized features.
2Reliability
If vacuum impregnation is used to wet small features, then cohesive forces are minimized and fluid flows into features, but pressure differential damages the workpiece
Solution Approach 1:
The patent segments the workpiece holder into two separate chambers: a front chamber that contacts the fluid and a back chamber connected to the vacuum pump. This segmentation allows independent pressure control on each side of the workpiece, enabling the front chamber to be at reduced pressure for wetting while the back chamber maintains atmospheric pressure to support the workpiece mechanically.
Solution Approach 2:
The patent introduces a fluid seal (such as a liquid seal or flexible membrane) as an intermediary between the front and back chambers. This intermediary transmits pressure equilibrium to the workpiece while preventing direct fluid contact with the backside, allowing the workpiece to experience minimal pressure differential during the wetting process.
3Productivity
If pressure differential is applied to wet the surface, then fluid penetration is improved, but stress and strain on the workpiece increases
Solution Approach 1:
The workpiece holder is segmented into front and back chambers that can be independently pressurized or evacuated. This allows the system to apply pressure differential only when needed for fluid penetration, while maintaining workpiece support through the back chamber, thus preserving workpiece strength during the wetting process.
Solution Approach 2:
The patent employs dynamic pressure control where the pressure differential is applied temporarily during fluid introduction and then reduced or eliminated. The system transitions between different pressure states to achieve wetting while minimizing stress on the workpiece, making the pressure application dynamic rather than static.
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
Enables uniform and repeatable wetting of small features on semiconductor wafers, preventing damage from pressure differentials and improving the consistency of subsequent electroplating processes.
Implementation Method 1
Before wetting, vacuum can be applied to minimize cohesive forces in the fluid, and facilitate flowing of a fluid (e.g., a substantially degassed fluid) into the small features
Implementation Method 2
maintaining a fluid seal to prohibit the fluid from reaching the edge or backside of the workpiece
Implementation Method 3
The port affects pressure in the cavity to minimize a pressure differential between the front and back surfaces of the workpiece
Data Source
AI summary
A method and apparatus for wetting the surface of a workpiece is disclosed. The apparatus includes a chamber with a vacuum port and a fluid port and a workpiece holder including a body, a ring, and a port. The body includes a surface and defines a cavity extending from the surface. The ring is adapted to retain the workpiece on the surface of body over the cavity. The ring forms a fluid seal relative to the workpiece and to the workpiece holder. The port is defined in the body and in communication with the cavity. The port affects pressure in the cavity to minimize a pressure differential between the front and back surfaces of the workpiece. The fluid port is in communication with the chamber. The fluid port delivers a fluid (e.g., a substantially degassed fluid) to wet the front surface of the workpiece during operation of the chamber at a reduced pressure relative to atmosphere.