Low-Temperature Metal CMP Pad Control to Minimize Dishing
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges in temperature control, leading to variations in polishing rate, uniformity, dishing, erosion, and corrosion, which affect the quality of semiconductor wafers and the lifespan of polishing pads.
Innovation Solution
A CMP system with temperature control mechanisms, including a coolant dispenser and a heating system, uses liquid and gas coolants like liquid nitrogen and carbon dioxide, and steam to regulate the polishing pad temperature during different stages of the polishing process, such as metal clearing and over-polishing, to maintain optimal conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If temperature control mechanisms (coolant dispenser and heating system) are added to the CMP system, then temperature-dependent issues like dishing and corrosion are reduced, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the temperature of the polishing pad during different stages of the CMP process. A coolant dispenser delivers coolant to lower the temperature during metal clearing and over-polishing stages, while a heating system can raise temperature during bulk polishing. This temperature parameter control reduces dishing and corrosion, improving polishing uniformity despite adding system complexity.
Solution Approach 2:
The patent implements dynamics by making the temperature control system adjustable and stage-specific. The coolant dispenser and heating system are controlled to operate at different temperatures and at different stages of the polishing process (bulk polishing vs. metal clearing/over-polishing). This dynamic temperature adjustment allows optimization for each stage, resolving the contradiction between precision and complexity.
2Manufacturing precision
If coolant is applied during metal clearing and over-polishing steps, then dishing and corrosion are minimized, but polishing rate may decrease
Solution Approach 1:
The patent applies periodic action by using temperature control at specific stages of the polishing process. Coolant is delivered during metal clearing and over-polishing steps when precision is critical, while the heating system operates during bulk polishing when removal rate is prioritized. This periodic, stage-specific temperature control minimizes dishing and corrosion without sacrificing overall productivity.
Solution Approach 2:
The patent uses preliminary action by controlling temperature before critical issues arise. The coolant system is activated during metal clearing and over-polishing steps to prevent dishing and corrosion from developing, while bulk polishing removes material efficiently. This staged approach addresses precision requirements before they become problems, maintaining both quality and productivity.
3Manufacturing precision
If polishing pad temperature is lowered during metal clearing and over-polishing, then pad asperity uniformity is improved, but energy consumption increases
Solution Approach 1:
The patent applies local quality by targeting temperature control specifically at the polishing pad surface during metal clearing and over-polishing steps. The coolant dispenser delivers coolant locally to the pad surface where asperity uniformity is critical, rather than cooling the entire system. This localized approach improves pad asperity uniformity while minimizing overall energy consumption.
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 temperature-dependent issues like dishing and corrosion, improves polishing uniformity, extends pad lifetime, and enhances wafer-to-wafer uniformity by tightly controlling the polishing pad temperature.
Implementation Method 1
a dispenser having one or more apertures suspended over the platen to direct coolant from the source of coolant onto the polishing surface of the polishing pad
Implementation Method 2
lowering the temperature of a polishing surface of a polishing pad used in a chemical mechanical polishing (CMP) process
Implementation Method 3
steam, i.e., gaseous H2O generated by boiling, can be injected into slurry to transfer energy with low liquid content
Implementation Method 4
steam, i.e., gaseous H2O generated by boiling
Implementation Method 5
The source of gas coolant medium can be connected to a vortex tube configured to direct a cold stream of gas onto the polishing pad
Data Source
AI summary
A chemical mechanical polishing system includes a platen to support a polishing pad having a polishing surface, a source of coolant, a dispenser having one or more apertures suspended over the platen to direct coolant from the source of coolant onto the polishing surface of the polishing pad; and a controller coupled to the source of coolant and configured to cause the source of coolant to deliver the coolant through the nozzles onto the polishing surface during a selected step of a polishing operation.