Polishing Pad Dressing via Rotational Direction Alternation
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Solution Overview
Problem
Existing methods for dressing polishing pads used in semiconductor wafer polishing do not provide long-lasting or satisfactory polishing quality, leading to frequent re-dressing needs and suboptimal surface preparation.
Innovation Solution
A method involving multiple combinations of rotational directions between polishing plates and dressers, utilizing diamond-covered dressing elements, to effectively restore and maintain the polishing pads' asperities, allowing for longer-lasting polishing quality and improved surface preparation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single-direction dressing methods are used, then the polishing pad surface is restored, but the polishing quality deteriorates quickly requiring frequent re-dressing
Solution Approach 1:
The patent applies periodic action by alternating the direction of rotation of the dresser relative to the polishing pad during the dressing process. The dresser rotates in one direction for a period, then reverses and rotates in the opposite direction for another period. This periodic reversal creates varied friction patterns that prevent uniform wear and maintain asperity structures longer, thereby extending the duration of effective polishing action.
Solution Approach 2:
The patent implements dynamics by making the dresser rotation direction variable rather than fixed. The system dynamically changes the rotational direction of the dresser during operation, creating time-varying friction forces on the polishing pad surface. This dynamic approach prevents the pad from reaching a uniform wear state too quickly, maintaining polishing effectiveness for longer periods.
2Manufacturing precision
If frequent re-dressing is performed to maintain polishing quality, then surface quality is maintained, but productivity decreases due to downtime
Solution Approach 1:
By implementing periodic reversal of the dresser rotation direction, the patent extends the effective life of the polishing pad between re-dressing operations. This reduces the frequency of downtime for re-dressing while maintaining consistent surface quality, thereby increasing overall productivity.
3Ease of operation
If the dresser rotates in the same direction as the polishing plate, then the dressing process is simple, but the asperities are not effectively restored
Solution Approach 1:
The patent applies inversion by rotating the dresser in the opposite direction to the polishing plate during dressing operations. This reverse rotation creates friction forces that effectively raise and restore asperities on the polishing pad surface, which cannot be achieved when both rotate in the same direction. The inverted rotation direction is key to achieving proper asperity restoration.
Solution Approach 2:
The system periodically alternates between dressing with the dresser rotating in the opposite direction to the polishing plate, and sometimes in the same direction. This periodic variation optimizes asperity restoration while maintaining operational simplicity through automated direction control.
4Manufacturing precision
If diamond-covered dressing elements are used, then asperity restoration is effective, but the device complexity increases
Solution Approach 1:
The patent changes the physical parameter of the dressing elements by covering them with diamond material, which has extreme hardness. This parameter change enables effective asperity restoration through controlled abrasion. The complexity increase is managed through automated direction control systems that simplify operation despite the more sophisticated dressing mechanism.
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 method achieves a significantly longer-lasting and enhanced polishing effect, improving plane-parallelism and surface quality of semiconductor wafers, while reducing the frequency of re-dressing foamed polishing pads, and maintaining a high removal rate during polishing.
Implementation Method 1
utilizing diamond-covered dressing elements, to effectively restore and maintain the polishing pads' asperities
Data Source
AI summary
A method dresses one polishing cloth or two polishing pads simultaneously, in which a polishing cloth has been applied to a polishing plate, with at least one dresser (4), which is equipped with at least one dressing element (8), this at least one dressing element (8) being in contact with the at least one polishing cloth (11, 12) to be dressed, wherein the at least one polishing plate (21, 22) is rotated with a relative rotational speed and the at least one dresser (4) is rotated with a relative rotational speed and at least two different combinations of directions of rotation of the two pairs of polishing plates (21, 22) and pin wheels (31, 32) are executed during the simultaneous dressing of two polishing pads (11, 12) or during the dressing of one polishing cloth (11) of the polishing plate (21) and of the at least one dresser (4).