Bulk Silicon Polishing Cycles to Prevent CMP Overpolishing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional chemical mechanical polishing (CMP) processes for bulk silicon substrates often result in uneven polishing and damage to thin silicon layers due to irregularities in the silicon, leading to overpolishing and device damage.
Innovation Solution
A method involving cyclic alternation between a silicon-reactive slurry and deionized water during mechanical polishing, where the silicon slurry reacts with bulk silicon to remove it, and deionized water interrupts this reaction to prevent overpolishing of thin silicon layers, allowing precise control over the polishing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional chemical mechanical polishing (CMP) is used on bulk silicon substrates, then polishing efficiency is improved, but uneven polishing and damage to thin silicon layers occur due to irregularities in the silicon
Solution Approach 1:
The patent applies periodic action by cyclically alternating between applying silicon-reactive slurry and rinsing with deionized water during the polishing process. This periodic alternation allows the polishing head to remove bulk silicon efficiently when slurry is present, then interrupts the chemical reaction with water to prevent overpolishing of thin silicon layers, thereby achieving both high polishing efficiency and uniformity without damage to thin areas
Solution Approach 2:
The patent maintains continuity of useful action by keeping the polishing head continuously operating on the silicon substrate throughout the process. The slurry is applied and rinsed in cycles, but the mechanical polishing action continues uninterrupted, ensuring consistent material removal while the chemical reaction is periodically controlled to protect thin regions
2Productivity
If continuous silicon slurry is applied during polishing, then bulk silicon removal is efficient, but overpolishing of thin silicon layers occurs causing device damage
Solution Approach 1:
The patent uses periodic action by implementing cyclic alternation between slurry application and water rinsing. During slurry application phases, bulk silicon is removed efficiently through chemical-mechanical reaction. During water rinsing phases, the chemical reaction is interrupted, preventing further removal and protecting thin silicon layers from overpolishing and device damage
Solution Approach 2:
The patent introduces deionized water as an intermediary substance that mediates between the silicon-reactive slurry and the silicon substrate. The water acts as a reaction interrupter, temporarily stopping the chemical etching process to prevent overpolishing of thin areas, while allowing the mechanical polishing to continue. This intermediary enables precise control over the polishing depth and protects sensitive device regions
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 enables precise removal of silicon layers without damaging thin areas, ensuring uniformity and preventing device damage by controlling the reaction time of the silicon slurry, thus maintaining the integrity of the semiconductor device.
Implementation Method 1
a reaction between the bulk silicon and the slurry takes place allowing the polishing head to remove the bulk silicon
Implementation Method 2
The deionized water interrupts this reaction and helps prevent overpolishing of thin silicon layers
Data Source
Figure 1A~1C
Figure 2
Figure 3A~3B
AI summary
Methods for polishing bulk silicon are disclosed. In one aspect, mechanical polishing is facilitated by cyclically alternating between a silicon reactive slurry and deionized water while a mechanical polishing head operates on a surface. In example aspects, the polishing head is polishing a bulk silicon carrier wafer to expose a backside of a radio frequency (RF) complementary metal oxide semiconductor (CMOS) switch, although other semiconductors may also benefit from example aspects of the present disclosure. While the silicon slurry is present, a reaction between the bulk silicon and the slurry takes place allowing the polishing head to remove the bulk silicon. The deionized water interrupts this reaction and helps prevent overpolishing which might otherwise damage the device.