CMP Pressure Profiling for Precession-Induced Thickness Asymmetry
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) systems struggle with angular asymmetry in substrate polishing due to variations in initial substrate thickness, slurry composition, polishing pad condition, and load variations, leading to inconsistent material removal rates and endpoint determination.
Innovation Solution
A polishing control model that accounts for substrate precession relative to the carrier head, using a Preston matrix to adjust pressures differentially over time based on substrate orientation, optimizing polishing parameters to achieve a target thickness profile through a cost function minimization algorithm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP systems use uniform polishing pressure across the substrate, then the polishing process is simple to control, but angular asymmetry in material removal occurs due to substrate precession and variations in initial thickness, slurry composition, and pad condition
Solution Approach 1:
The polishing system divides the substrate or carrier head into multiple angular zones with independently controllable pressures. This segmentation allows different pressure levels to be applied to different angular regions, compensating for asymmetry caused by substrate precession and initial thickness variations, thereby achieving more uniform material removal across the substrate surface.
Solution Approach 2:
The system dynamically adjusts polishing pressures during the polishing process based on real-time or pre-calculated asymmetry compensation requirements. By making the pressure profile time-dependent and adaptive rather than static and uniform, the system counteracts the effects of substrate precession and maintains consistent material removal rates despite variations in initial conditions.
2Productivity
If polishing pressure is increased to accelerate material removal, then productivity improves, but variations in material removal rate across the substrate and from substrate to substrate increase
Solution Approach 1:
The system applies different pressure levels to different angular zones of the substrate based on local requirements. Areas that need faster removal receive higher pressure, while areas approaching the target thickness receive lower pressure. This localized quality control maintains high overall productivity while ensuring consistent material removal across different substrates and angular positions.
Solution Approach 2:
The system uses feedback from measured substrate thickness profiles and material removal rates to dynamically adjust polishing pressures. By continuously monitoring the polishing process and adjusting pressures in response to measured variations, the system maintains consistent material removal rates across substrates while achieving high productivity through optimized pressure distribution.
3Manufacturing precision
If the polishing process does not account for substrate precession, then the control system is simpler, but angular asymmetry in the polished substrate profile cannot be corrected
Solution Approach 1:
The system performs preliminary calculations of substrate precession behavior and asymmetry characteristics before the polishing process begins. Based on these pre-calculated models, the system pre-determines the optimal pressure distribution and timing to compensate for expected asymmetry, allowing the control system to counteract precession effects without requiring complex real-time measurements during polishing.
Solution Approach 2:
The system incorporates feedback mechanisms that measure substrate orientation and precession during polishing, using this information to dynamically adjust pressures to maintain angular symmetry in the final profile. This feedback-driven approach enables the control system to adapt to actual precession behavior and correct asymmetry in real-time.
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 reliably corrects angular asymmetry and achieves consistent substrate polishing by dynamically adjusting pressures, ensuring precise material removal and reducing angular asymmetry in polished substrates.
Implementation Method 1
The exposed surface of the substrate is typically placed against a rotating polishing pad with a durable roughened surface
Implementation Method 2
Chemical mechanical polishing (CMP) is one accepted method of planarization
Implementation Method 3
The carrier head provides a controllable load on the substrate to push it against the polishing pad
Implementation Method 4
A polishing liquid, such as a slurry with abrasive particles, is typically supplied to the surface of the polishing pad
Data Source
AI summary
Generating a recipe for a polishing process includes receiving a target removal profile that includes a target thickness to remove for locations spaced angularly around a center of a substrate, storing a first function providing substrate orientation relative to a carrier head over time, storing a second function defining a polishing rate below a zone of the zone as a function of one or more pressures of one or more zones of the carrier head, and for each particular zone of the plurality of zones, calculate a recipe defining a pressure for the particular zone over time. Calculating the recipe includes calculating an expected thickness profile after polishing from the second function defining the polishing rate and the first function providing substrate orientation relative to the zone over time, and applying a minimizing algorithm to reduce a difference between the expected thickness profile and the target thickness profile.