Polishing Apparatus Weighted Average Rate Control
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) methods face challenges in maintaining a stable polishing rate due to variations in surface conditions of the polishing pad, pad conditioner, polishing liquid composition, temperature, and material properties, leading to irregularities in film thickness and increased manufacturing costs and yield loss.
Innovation Solution
A polishing apparatus equipped with a measurement section to input desired film thickness, store polishing rate data, and calculate optimal polishing time using a weighted average method, incorporating a calibration substrate for maintaining measurement accuracy and accounting for variations in polishing rate data to prevent excessive polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional CMP methods are used with average polishing rate calculation, then measurement complexity is reduced, but film thickness control precision deteriorates
Solution Approach 1:
The system performs preliminary measurements on a test substrate before actual polishing to determine the specific polishing rate. This preliminary action allows the system to establish accurate polishing parameters in advance, ensuring precise film thickness control during subsequent production polishing without requiring complex real-time measurement systems.
Solution Approach 2:
The polishing apparatus uses itself to perform measurements and determine polishing rates through automated measurement and calculation functions. The system self-calibrates by measuring test substrates and automatically adjusting polishing parameters, eliminating the need for external complex measurement equipment while maintaining high precision.
2Manufacturing precision
If polishing time is extended to ensure adequate polishing, then film thickness uniformity improves, but productivity decreases
Solution Approach 1:
The system dynamically adjusts polishing parameters including pressure, speed, and time based on measured polishing rates from test substrates. By optimizing these parameters specifically for each polishing condition, the system achieves uniform film thickness with shorter polishing times, thereby maintaining high productivity while ensuring quality.
Solution Approach 2:
The system implements feedback control by measuring actual polishing rates on test substrates and using this information to adjust polishing time and other parameters for production substrates. This closed-loop feedback ensures optimal polishing time is used, achieving uniform thickness without excessive polishing time that would reduce productivity.
3Manufacturing precision
If polishing rate variations are accommodated by increasing safety margins, then film thickness accuracy improves, but polishing time increases
Solution Approach 1:
The system performs preliminary measurements to determine actual polishing rates before production polishing. By knowing the specific polishing rate in advance through preliminary testing, the system can calculate the exact polishing time needed without adding excessive safety margins, thus achieving accurate film thickness control without unnecessary time 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
The solution ensures accurate film thickness control, reduces reworking, and minimizes yield loss by stabilizing the polishing process and optimizing polishing time, thereby maintaining manufacturing efficiency and cost-effectiveness.
Implementation Method 1
a measurement section for measuring a thickness of a film formed on the substrate
Implementation Method 2
a polishing section for pressing the substrate against a polishing surface so as to bring the substrate into sliding contact with the polishing surface to polish the substrate
Implementation Method 3
In the chemical mechanical polishing, with use of a polishing apparatus, while a polishing liquid containing abrasive particles such as silica (SiO2) therein is supplied onto a polishing surface such as a polishing pad, a substrate such as a semiconductor wafer is brought into sliding contact with the polishing surface, so that the substrate is polished
Data Source
AI summary
A polishing apparatus has a polishing section (302) configured to polish a substrate and a measurement section (307) configured to measure a thickness of a film formed on the substrate. The polishing apparatus also has an interface (310) configured to input a desired thickness of a film formed on a substrate to be polished and a storage device (308a) configured to store polishing rate data on at least one past substrate therein. The polishing apparatus includes an arithmetic unit (308b) operable to calculate a polishing rate and an optimal polishing time based on the polishing rate data and the desired thickness by using a weighted average method which weights the polishing rate data on a lately polished substrate.