Dynamic Residue Clearing Control with In-Situ Profile Monitoring
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges in achieving uniform material removal rates across substrates due to variations in initial thickness, slurry composition, polishing pad conditions, and load, leading to inconsistencies in reaching the polishing endpoint and achieving desired profiles.
Innovation Solution
The method involves independently controlling the polishing rate of each zone on a substrate using an in-situ monitoring system to adjust polishing parameters, fitting linear functions to measurement sequences, and calculating adjustments based on error values to ensure uniform endpoint times and profiles across zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a constant pressure is applied during CMP, then the polishing process is simple to control, but the material removal rate varies across the substrate due to variations in initial thickness, slurry composition, polishing pad condition, and load
Solution Approach 1:
The substrate surface is divided into multiple zones (e.g., center, inner annular, outer annular zones) with independently controllable polishing parameters. This segmentation allows each zone to be polished at different rates to compensate for variations in initial thickness and achieve uniform material removal across the entire substrate.
Solution Approach 2:
The polishing parameters (such as downforce or rotational speed) are dynamically adjusted during the polishing process based on real-time monitoring of material removal rates. This dynamic adjustment enables the system to compensate for variations in slurry composition, pad condition, and load, maintaining consistent polishing performance throughout the substrate.
2Ease of operation
If the polishing endpoint is determined solely by polishing time, then the process is easy to manage, but it is not possible to achieve a desired profile due to variations in material removal rate
Solution Approach 1:
An in-situ monitoring system continuously measures the material removal rate during polishing and provides real-time feedback to the control system. This feedback enables dynamic adjustment of polishing parameters to achieve the desired profile accuracy, rather than relying solely on predetermined polishing time.
3Measurement precision
If optical monitoring is used to track polishing progress, then endpoint detection is improved, but existing techniques do not satisfy increasing demands for precision and throughput
Solution Approach 1:
The monitoring system divides the substrate into multiple zones and independently tracks the polishing progress of each zone. This segmented monitoring approach provides more precise endpoint detection for each zone while maintaining high throughput by enabling parallel processing of multiple zones simultaneously.
Solution Approach 2:
The system performs preliminary measurements and calculations to predict the endpoint for each zone based on real-time data, allowing the polishing process to be optimized before the actual endpoint is reached. This preliminary action reduces the need for excessive polishing and improves overall process efficiency.
Data Source
AI summary
A method for controlling the residue clearing process of a chemical mechanical polishing (“CMP”) process is provided. Dynamic in-situ profile control (“ISPC”) is used to control polishing before residue clearing starts, and then a new polishing recipe is dynamically calculated for the clearing process. Several different methods are disclosed for calculating the clearing recipe. First, in certain implementations when feedback at T0 or T1 methods are used, a post polishing profile and feedback offsets are generated in ISPC software. Based on the polishing profile and feedback generated from ISPC before the start of the clearing process, a flat post profile after clearing is targeted. The estimated time for the clearing step may be based on the previously processed wafers (for example, a moving average of the previous endpoint times). The calculated pressures may be scaled to a lower (or higher) baseline pressure for a more uniform clearing.