Hard Polishing Pad CMP Process for Copper Barrier Layer
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Solution Overview
Problem
The existing copper/barrier chemical mechanical polishing (CMP) process using soft pads for barrier polishing has a short pad lifetime, unstable removal rate, and unsatisfactory uniformity, leading to frequent pad changes and reduced tool uptime and product throughput.
Innovation Solution
A copper/barrier CMP process using multiple hard polishing pads with specific hardness ranges and alkaline condition chemicals, including triethanolamine, ethylene glycol, and citric acid, to improve pad durability and uniformity, along with a transparent window for thickness measurement and periodic rejuvenation of the polishing surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If soft polishing pads are used for barrier polishing, then the polishing process can be performed, but the pad lifetime is short and removal rate is unstable
Solution Approach 1:
The patent changes the hardness parameter of the polishing pad from soft to hard (specifically, a hard polishing pad with Shore A hardness of 70-90). This parameter change resolves the contradiction by providing both extended pad lifetime and stable removal rate, as the harder pad maintains its structural integrity and polishing characteristics throughout its service life.
Solution Approach 2:
The patent employs a composite polishing pad structure consisting of a hard polishing pad layer and a backing layer with specific properties. This composite structure combines the durability of hard materials with the flexibility and support of the backing layer, achieving both long pad lifetime and consistent removal rate.
2Manufacturing precision
If soft polishing pads are used for barrier polishing, then the polishing process can be performed, but the uniformity is unsatisfactory
Solution Approach 1:
By changing the hardness parameter to a hard polishing pad (Shore A 70-90), the patent achieves superior polishing uniformity while simultaneously extending pad lifetime. The hard pad maintains consistent contact pressure and wear characteristics throughout its extended service life.
3Manufacturing precision
If frequent pad changes are made to maintain polishing quality, then polishing uniformity can be maintained, but tool uptime and product throughput are reduced
Solution Approach 1:
The patent changes the pad hardness parameter to extend pad lifetime from hours to days or weeks, dramatically reducing the frequency of pad changes. This maintains polishing uniformity while significantly improving tool uptime and productivity.
Solution Approach 2:
By using a hard polishing pad that maintains its performance characteristics over an extended period, the patent enables continuous polishing operations without frequent interruptions for pad replacement, thus maintaining both quality and productivity.
4Reliability
If multiple hard polishing pads with specific hardness ranges are used, then pad lifetime is extended and uniformity is enhanced, but process complexity increases
Solution Approach 1:
The patent specifies a hardness range (Shore A 70-90) rather than a single value, providing process flexibility and robustness. This parameter specification achieves reliable process stability while keeping the implementation straightforward through clear material selection criteria.
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 process extends pad lifetime, stabilizes removal rates, and enhances uniformity, resulting in improved throughput and reliability with reduced costs.
Implementation Method 1
A copper/barrier CMP process using multiple hard polishing pads with specific hardness ranges and alkaline condition chemicals, including triethanolamine, ethylene glycol, and citric acid, to improve pad durability and uniformity
Implementation Method 2
along with a transparent window for thickness measurement
Implementation Method 3
The polishing pad may be either a 'standard' pad or a fixed-abrasive pad. A fixed-abrasive pad has abrasive particles held in a containment media
Implementation Method 4
The polishing process is assisted by chemical compounds within the polishing slurry that facilitate removal of the material being polished
Data Source
AI summary
A chemical mechanical polishing process includes placing a substrate on a first polishing pad of a first platen, wherein the substrate has a bulk metal layer and a barrier layer; polishing the bulk metal layer by using the first polishing pad having a hardness of above 50 (Shore D) until the barrier layer is exposed; polishing the barrier layer on a second polishing pad of a second platen after removing the bulk metal layer, wherein the second polishing pad has a hardness ranging between 40 and 50 (Shore D) and includes an upper layer and a lower backing layer and the upper layer has a hardness less than 50 (Shore D).