CMP Electrostatic Dissipative Pedestal for Wafer Charge Control
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Solution Overview
Problem
Mechanical and chemical-mechanical polishing processes for semiconductor wafers often result in physical and electrical damage, such as delamination, chips, and short circuits, due to electrostatic discharge and high-pressure washing, which increase fabrication costs and reduce yield.
Innovation Solution
The use of an electrostatic dissipative pedestal and controlled fluid pressure system in a CMP machine to dissipate electrostatic charge and reduce physical damage during and after polishing, by employing an electrostatic dissipative material with controlled electrical resistance and a pressure control system to minimize sudden electrostatic discharge and prevent material stripping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP polishing is performed, then satisfactory polishing and planarizing results are achieved, but wafer damage occurs due to electrostatic discharge and high-pressure washing
Solution Approach 1:
An electrostatic dissipative pedestal is introduced as an intermediary component between the wafer and the polishing system. This pedestal has controlled electrical resistance properties that allow it to safely dissipate electrostatic charge accumulated during polishing, preventing sudden electrostatic discharge that causes wafer damage while maintaining effective polishing performance
Solution Approach 2:
The electrical resistance parameter of the pedestal is specifically controlled to be within a certain range to optimize electrostatic charge dissipation. Additionally, the washing pressure parameter is reduced from conventional high pressure to a lower level that prevents material stripping while still achieving adequate cleaning, thus resolving the contradiction between effective washing and wafer damage prevention
2Ease of operation
If high-pressure washing is used after polishing, then cleaning effectiveness is improved, but material stripping and physical damage occur
Solution Approach 1:
The washing pressure parameter is changed from high pressure to a controlled lower pressure level. This parameter change maintains sufficient cleaning effectiveness for removing polishing residues while preventing the material stripping and physical damage that occurs with conventional high-pressure washing
3Productivity
If electrostatic charge accumulates on wafers during polishing, then polishing process continues, but sudden electrostatic discharge causes short circuits and electrical damage
Solution Approach 1:
The electrostatic dissipative pedestal serves as an intermediary charge dissipation path between the wafer and ground. It provides controlled resistance that allows gradual dissipation of electrostatic charge accumulated during polishing, preventing sudden discharge that would cause short circuits and electrical damage while not interfering with the polishing process continuity
Solution Approach 2:
The system replaces reliance on mechanical contact alone for charge management with an electrostatic field-based dissipation mechanism through the controlled resistance pedestal, enabling continuous polishing operation without interrupting for charge neutralization
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
The solution effectively reduces wafer damage by preventing electrostatic discharge and minimizing physical damage from high-pressure washing, thereby improving the yield and reducing the unit cost of microelectronic devices.
Implementation Method 1
employing an electrostatic dissipative material with controlled electrical resistance to dissipate electrostatic charge
Data Source
AI summary
A chemical-mechanical polishing machine and associated methods are disclosed. One embodiment of the machine includes a polishing pad, a wafer carrier corresponding to the polishing pad and configured to carry a semiconductor wafer, and a transfer station proximate to the polishing pad for holding the wafer during loading and/or unloading. At least one of the wafer carrier and the transfer station is configured to dissipate electrostatic charge from the wafer.