CMP Slurry Concentration Control for Metal Gate Bump Defects
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Solution Overview
Problem
The chemical mechanical polishing (CMP) process in semiconductor manufacturing generates a large number of metal ions, leading to significant bump defects on the wafer surface, which results in unsatisfactory manufacturing yield and defective semiconductor devices.
Innovation Solution
A method involving a two-step chemical mechanical polishing process with a diluted slurry set, followed by hydrogen peroxide buffing and cleaning, reduces metal ion byproducts and subsequent bump defects by using a first slurry set with higher concentration, a second slurry set with lower concentration and hydrogen peroxide, and a combination of organic acids and non-fluorinated cleaning solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional CMP process with standard slurry concentration is used, then the polishing efficiency is maintained, but a large number of metal ions are generated causing bump defects
Solution Approach 1:
The patent applies parameter changes by adjusting the slurry concentration from standard levels to a reduced concentration range (5-20 wt%), and by controlling the polishing pressure (0.5-2.0 psi) and speed (30-100 rpm) to minimize metal ion generation while maintaining adequate polishing efficiency
Solution Approach 2:
The patent introduces an intermediary cleaning step using hydrogen peroxide (H2O2) solution between polishing operations to remove metal ions from the wafer surface, preventing their accumulation and subsequent bump defect formation
2Object-generated harmful factors
If the slurry concentration is reduced to minimize metal ions, then bump defects are reduced, but the polishing efficiency may be compromised
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: slurry concentration (5-20 wt%), polishing pressure (0.5-2.0 psi), and polishing speed (30-100 rpm) to achieve a balance where metal ion generation is minimized while maintaining sufficient polishing rate for manufacturing requirements
Solution Approach 2:
The patent implements a continuous multi-step process where reduced-concentration polishing is followed by hydrogen peroxide cleaning and then anti-reflective coating, ensuring that the useful action of removing material continues while intermittently removing harmful metal ions
3Reliability
If multiple polishing steps with different slurries are implemented, then metal ion residues are minimized, but the process complexity increases
Solution Approach 1:
The patent segments the polishing process into distinct steps: first polishing with reduced concentration slurry, followed by hydrogen peroxide cleaning, then anti-reflective coating deposition. This segmentation allows each step to be optimized for its specific function while maintaining overall process control
Solution Approach 2:
The patent converts the potentially harmful effect of extended process time into a benefit by using the additional steps to thoroughly remove metal ions and prevent defects, where the extra cleaning and coating steps ultimately improve wafer quality and device reliability
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 significantly reduces bump defects on the wafer surface, enhancing the quality and yield of semiconductor devices by minimizing metal ion residues and ensuring a satisfactory manufacturing process.
Implementation Method 1
applying hydrogen peroxide (H2O2) to the wafer for performing a buffing process on the wafer
Implementation Method 2
using a first slurry set to perform a first chemical mechanical polishing process on the wafer
Data Source
AI summary
A method for processing a wafer (in a process of manufacturing semiconductor devices) may include the following steps: using a first slurry set to perform a first chemical mechanical polishing process on the wafer, wherein the wafer includes a plurality of metal gate structures; using a second slurry set to perform a second chemical mechanical polishing process on the wafer, wherein a concentration of a slurry material in the second slurry set is less than a concentration of the slurry material in the first slurry set; performing a cleaning process on the wafer; and providing an anti-reflective coating on the wafer.