Dynamic Control for Double-Sided Wafer Polishing Flatness
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Solution Overview
Problem
Conventional double-sided polishing methods for semiconductor wafers face issues with maintaining flatness and parallelism due to polishing pad wear, leading to 'doming' or 'dishing' effects, which increase production costs and downtime, and are heavily dependent on personal expertise for adjusting parameters.
Innovation Solution
A dynamic control system that includes a controller and memory to determine required tuning for flatness control parameters, generate recipes based on historical statistical process control feedback data, and automatically adjust parameters such as platen rotational speeds and pressures to maintain optimal wafer flatness during the polishing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polishing machines with rotating polishing pads are used, then polishing operation can be performed, but pad wear causes unacceptable flatness parameters and doming/dishing effects
Solution Approach 1:
The polishing system dynamically adjusts the normal force applied to different radial zones of the polishing pad during the polishing process. By varying the downforce profile across the pad radius in real-time, the system compensates for pad wear and maintains uniform material removal rates, preventing doming and dishing effects while extending pad service life.
Solution Approach 2:
The system changes the polishing parameters (normal force distribution) as a function of pad wear progression. By monitoring pad wear and adjusting the force profile accordingly, the system maintains optimal polishing conditions throughout the pad's service life, ensuring consistent wafer flatness parameters even as the pad degrades.
2Productivity
If polishing pad wear is allowed to proceed naturally, then production continues without interruption, but wafer flatness parameters become unacceptable requiring pad replacement
Solution Approach 1:
The system continuously monitors wafer flatness parameters during the polishing process and uses this feedback to adjust the normal force distribution on the polishing pad in real-time. This closed-loop control enables the system to maintain acceptable flatness parameters throughout production, eliminating the need for periodic pad replacements and ensuring continuous productivity.
Solution Approach 2:
The polishing system automatically adjusts its own operating parameters (force profile) based on real-time measurements of pad wear and wafer flatness. This self-regulating capability allows the system to maintain optimal performance without external intervention or manual parameter changes, sustaining both productivity and precision throughout the polishing process.
3Manufacturing precision
If manual adjustment of polishing parameters based on personal expertise is used, then some flatness control can be achieved, but significant variations occur between different operators
Solution Approach 1:
The system replaces manual operator adjustments with an automated control system that uses sensors and algorithms to determine optimal polishing parameters. This substitution eliminates operator dependency and personal expertise requirements, providing consistent, repeatable flatness control across different operators while maintaining high manufacturing precision.
Solution Approach 2:
The polishing system automatically determines and adjusts its own parameters based on real-time process data and pre-programmed algorithms. This self-determination capability removes the need for operator intervention and personal expertise, ensuring consistent results regardless of which operator is performing the polishing operation.
4Manufacturing precision
If polishing parameters are frequently adjusted to maintain flatness, then wafer quality improves, but production time and costs increase
Solution Approach 1:
The system performs parameter adjustments continuously during the polishing process rather than requiring interruptions for manual adjustments. The automated real-time control maintains continuous polishing operation while dynamically optimizing parameters, eliminating production stoppages and reducing total production time while maintaining high wafer flatness quality.
Solution Approach 2:
The system uses real-time feedback from sensors monitoring wafer flatness to make immediate parameter adjustments during polishing. This continuous feedback loop eliminates the need for time-consuming intermediate measurements and manual interventions, maintaining high precision while minimizing production time losses.
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 reduces variations in wafer flatness and production costs by enabling real-time adjustments and automated recipe generation, improving the consistency and efficiency of double-sided polishing without relying on personal experience, thus enhancing the quality of semiconductor wafers.
Implementation Method 1
A polishing slurry, typically including chemical polishing agents and abrasive particles, is applied to the pad for greater polishing interaction between the polishing pad and the surface of the wafer
Implementation Method 2
A polishing slurry, typically including chemical polishing agents and abrasive particles, is applied to the pad for greater polishing interaction
Implementation Method 3
As the pad wears, e.g., after a few hundred wafers, wafer flatness parameters degrade because the pad is no longer flat, but instead has a worn annular band forming a depression along the polishing surface of the pad
Data Source
AI summary
A polishing apparatus for double-sided polishing of semiconductor wafers including a first platen, a second platen, a wafer carrier, and a controller is disclosed. The controller is configured to perform operations including determining whether a batch of the semiconductor wafers is loaded on the wafer carrier for double-sided polishing and retrieving specification for the batch of semiconductor wafers. The operations include based on the retrieved specification, determining an amount of tuning required for one or more flatness control parameters, and based on the amount of tuning required for the one or more flatness control parameters, identifying, or generating a recipe to perform the double-sided polishing on the batch of the semiconductor wafers. The operations include storing statistical process control (SPC) feedback data in a database to perform one or more additional iterations of the double-sided polishing on the batch of the semiconductor wafers.