CMP Polishing Apparatus Thickness Feedback Control
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Solution Overview
Problem
In semiconductor wafer polishing, it is challenging to initiate the second polishing step with an optimal thickness of the uppermost-layer film due to variations in initial thickness among substrates and deterioration of consumable members, leading to prolonged polishing times and potential dishing or erosion.
Innovation Solution
A method and apparatus that measure the thickness of the uppermost-layer film before polishing, determine polishing rates for each step based on measured thickness and processing time, and adjust the first polishing step time to ensure consistent thickness at the start of the second step, using torque detection to change polishing objects without needing additional thickness measurement tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the first polishing step uses a polishing liquid with high polishing rate for the oxide film, then the polishing amount of oxide film increases and overall polishing time shortens, but the surface irregularities of the oxide film are not eliminated
Solution Approach 1:
The polishing process is divided into two distinct steps with different objectives: the first polishing step removes the majority of the oxide film quickly, while the second polishing step eliminates surface irregularities. This segmentation allows each step to be optimized independently for its specific function.
Solution Approach 2:
The function of removing surface irregularities is extracted from the first polishing step and assigned to the second polishing step. This extraction allows the first step to focus solely on high-rate material removal without being constrained by the need to also smooth the surface.
2Manufacturing precision
If the second polishing step is initiated when the oxide film remains in excess, then the surface irregularities can be eliminated, but the overall polishing time becomes longer
Solution Approach 1:
The system measures the thickness of the oxide film before polishing and uses this information to determine the polishing rates. This feedback mechanism allows optimization of the polishing process parameters to achieve the desired surface flatness while minimizing polishing time.
3Manufacturing precision
If the second polishing step is carried out over a long time to eliminate surface irregularities, then the surface flatness improves, but excessive polishing occurs in the trenches forming dishing or erosion
Solution Approach 1:
By measuring the oxide film thickness before polishing and calculating the polishing rates, the system can precisely control the polishing duration. This feedback control prevents over-polishing that would cause dishing or erosion while still achieving the necessary surface flatness.
Solution Approach 2:
The polishing process parameters (time, pressure, polishing liquid flow rate) are adjusted based on the measured oxide film thickness and calculated polishing rates. This dynamic parameter adjustment ensures optimal polishing conditions that achieve surface flatness without causing harmful effects.
4Manufacturing precision
If the initial thickness of the oxide film varies among substrates, then different polishing times are required, but this increases process complexity
Solution Approach 1:
The system measures the oxide film thickness before polishing and uses this feedback information to calculate appropriate polishing rates and durations. This automated feedback control handles thickness variations without requiring complex manual adjustments or multiple measurement tools.
Solution Approach 2:
The system replaces complex mechanical measurement and adjustment mechanisms with a simpler approach: measuring the oxide film thickness once before polishing and using calculated polishing rates to control the process. This substitution reduces device complexity while maintaining precision.
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 equalized thickness of the uppermost-layer film at the start of the second polishing step across all workpieces, reducing overall polishing time and preventing surface defects like dishing or erosion, while also accounting for consumable member wear.
Implementation Method 1
polishing by a chemical mechanical polishing (CMP) apparatus
Implementation Method 2
measuring a thickness of a film, forming the uppermost layer of a workpiece, before polishing
Implementation Method 3
polishing by a chemical mechanical polishing (CMP) apparatus
Implementation Method 4
polishing the uppermost-layer film partway and a subsequent second polishing step to polish the remaining uppermost-layer film
Data Source
AI summary
A polishing method enables to initiation a second polishing step of a workpiece with an optimal thickness of an uppermost-layer film to be polished. The polishing method comprises: measuring a thickness of an uppermost-layer film, and then carrying out a first polishing step to polish the uppermost-layer film partway and a second polishing step to polish the remaining uppermost-layer film and a next-layer film; determining the polishing rates of the uppermost-layer film in the first and second polishing steps; and measuring a thickness of an uppermost-layer film of a predetermined nth workpiece and setting a processing time for the first polishing step of the nth workpiece or a next predetermined nth workpiece.