Contact-Area-Changeable CMP Conditioning for Enhancing Pad Lifetime

At a Glance

Metadata	Details
Publication Date	2021-04-14
Journal	Applied Sciences
Authors	Jungyu Son, Hyunseop Lee
Institutions	Tongmyong University, Dong-A University
Citations	12
Analysis	Full AI Review Included

Technical Documentation & Analysis: Contact-Area-Changeable CMP Conditioning

This document analyzes the requirements and results of the research paper “Contact-Area-Changeable CMP Conditioning for Enhancing Pad Lifetime” and aligns them with the advanced MPCVD diamond solutions offered by 6CCVD.

Executive Summary

This study successfully demonstrates a novel approach to Chemical-Mechanical Polishing (CMP) pad conditioning using a split (contact-area-changeable) diamond conditioner, significantly extending pad lifetime and improving process stability.

Core Challenge Addressed: Conventional swing-arm conditioning (Case I) causes non-uniform, excessive pad wear, leading to a rapid 44.9% drop in Material Removal Rate (MRR) and increased Within-Wafer Non-Uniformity (WIWNU) after just 12 hours.
Proposed Solution: Implementation of a split, contact-area-changeable diamond conditioner (Case II) allowing independent load control and targeted wear reduction in critical wafer-pad contact zones.
Performance Improvement (Lifetime): Pad lifetime was extended from less than 16 hours (Case I) to over 20 hours (Case II) while maintaining stable performance metrics.
Performance Improvement (MRR Stability): The MRR reduction over the experimental period was drastically minimized, dropping only 7.4% (Case II) compared to 44.9% (Case I).
Uniformity Control: WIWNU remained stable and low (< 3%) for the full 20 hours in Case II, demonstrating uniform pad wear and consistent process quality.
Material Requirement: The success of this system relies entirely on the durability and precise arrangement of high-quality diamond grit, a core offering of 6CCVD’s MPCVD Polycrystalline Diamond (PCD).

Technical Specifications

The following hard data points were extracted from the experimental setup and results, highlighting the critical parameters for CMP conditioning and performance metrics.

Parameter	Value	Unit	Context
Pad Lifetime (Case I)	< 16	hours	Wafer broke due to excessive pad wear.
Pad Lifetime (Case II)	> 20	hours	Stable MRR/WIWNU maintained.
MRR Reduction (Case I)	44.9	%	Decrease over 16 hours (401.3 to 221.0 nm/min).
MRR Reduction (Case II)	7.4	%	Decrease over 20 hours (387.7 to 359.0 nm/min).
WIWNU Stability (Case II)	< 3	%	Maintained for the full 20 hours.
SiO₂ Film Thickness	1.5	µm	Initial thickness on Si wafers (200 mm).
Conditioning Load	4	kgf	Total load applied during conditioning.
Platen Rotational Speed	93	rpm	CMP and Conditioning speed.
Conditioner Rotational Speed	101	rpm	Conditioning speed.
Inner Conditioner Diameter	64	mm	Split conditioner dimension.
Outer Conditioner Width	31	mm	Split conditioner dimension (ring width).
Gap Between Conditioners	2.5	mm	Required precision gap for split design.
Wafer Pressure (CMP)	34.3	kPa	Applied pressure during polishing.
Retaining-Ring Pressure	44.1	kPa	Applied pressure during polishing.
Slurry Flow Rate	150	mL/min	TSO-12 Silica Slurry.

Key Methodologies

The experiment focused on comparing a conventional full-contact diamond conditioner (Case I) with a novel split, contact-area-changeable diamond conditioner (Case II).

1. CMP System and Consumables

Machine: R&D CMP machine (POLI-762, G&P Technology Inc.).
Wafer: 200 mm diameter Si wafer with 1.5 µm thick SiO₂ film.
Pad: Hard polyurethane KONI pad.
Slurry: TSO-12 Silica slurry.
Polishing Time: 60 seconds per CMP test.

2. Conditioning System and Parameters

System Type: Swing-arm conditioning system.
Conditioner Design:
- Case I: Conventional disk-type (468 diamond grits).
- Case II: Split conditioner (Inner: 200 grits, Outer Ring: 268 grits).
Conditioning Load: 4 kgf (independently controllable for split conditioner).
Rotational Speeds: Platen (93 rpm), Conditioner (101 rpm).
Swing Motion: Fixed at 9 sweeps per minute.
Conditioning Zones: Swing movement partitioned into five radial zones (50 mm to 370 mm from pad center), with equal 20% duration time in each zone to isolate the effect of the split conditioner design.

3. Measurement and Analysis

Pad Profile Measurement: Pad Measurement System (PMS, G&P Technology) with 0.1 µm resolution, used to measure pad thickness profiles before and after conditioning.
Film Thickness Measurement: Reflectometer (ST5030-SL) used to measure SiO₂ film thickness at 39 radial points.
Performance Metrics: Material Removal Rate (MRR) and Within-Wafer Non-Uniformity (WIWNU) were calculated using standard deviation (σ) and average MRR (MRR_avg).
Wear Analysis: Scanning Electron Microscope (SEM) imaging was used to confirm the disappearance of pad grooves in Case I versus the retention of grooves in Case II after prolonged conditioning.

6CCVD Solutions & Capabilities

The research highlights the critical need for highly durable, precisely dimensioned diamond components to manage pad wear and extend CMP process stability. 6CCVD is uniquely positioned to supply the next generation of diamond conditioner materials required to replicate and advance this research.

Applicable Materials

The diamond grit used in CMP conditioning must withstand extreme mechanical and thermal stress over extended periods. 6CCVD recommends the following MPCVD diamond materials for advanced CMP dressers:

6CCVD Material	Description	Application Relevance to Study
Polycrystalline Diamond (PCD)	High-purity, robust MPCVD diamond plates (up to 125 mm diameter).	Ideal for Dressers: Provides superior hardness, thermal stability, and wear resistance necessary for high-volume, long-lifetime conditioning disks (Case II).
Optical Grade SCD	Single Crystal Diamond, highest purity, Ra < 1 nm polish available.	R&D/Precision Studies: Suitable for ultra-precision single-point diamond dressing experiments or fundamental studies on grit-pad interaction.
Boron-Doped Diamond (BDD)	Electrically conductive diamond films.	Future Integration: Potential for use in advanced electrochemical CMP conditioning or integrated sensor applications within the dresser head.

Customization Potential

The success of the contact-area-changeable system (Case II) relies on the precise geometry of the split conditioner (64 mm inner disk, 31 mm outer ring, 2.5 mm gap). 6CCVD offers the necessary fabrication capabilities to support custom CMP tool development:

Custom Dimensions: 6CCVD provides PCD plates and wafers up to 125 mm in diameter, allowing for the fabrication of large-scale, custom-geometry conditioning disks required for 200 mm and 300 mm wafer processing.
Precision Cutting and Shaping: We offer advanced laser cutting and machining services to achieve the precise inner/outer ring geometries and the critical 2.5 mm gap tolerance demonstrated in this study.
Metalization Services: While the paper focused on mechanical wear, future integrated dressers may require electrical contacts or thermal management layers. 6CCVD provides in-house metalization (Au, Pt, Pd, Ti, W, Cu) for bonding or sensor integration onto the diamond substrate.
Ultra-Low Roughness Polishing: We guarantee surface roughness (Ra) < 5 nm on inch-size PCD, ensuring optimal diamond grit exposure and consistent contact mechanics for predictable pad wear profiles.

Engineering Support

The research demonstrates that optimizing the diamond contact area is key to controlling the pad wear profile and maintaining low WIWNU. 6CCVD’s in-house PhD team specializes in the material science of diamond wear and friction.

Material Selection for CMP: Our experts can assist researchers and engineers in selecting the optimal diamond grain size, density, and substrate material (PCD vs. SCD) to achieve specific pad cut rate profiles and maximize lifetime for similar CMP Pad Conditioning projects.
Wear Modeling Consultation: We provide consultation on how diamond material properties (e.g., crystal orientation, defect density) influence the kinematic wear models used in this study (e.g., Lee et al. [35] method).
Global Supply Chain: 6CCVD ensures reliable, global shipping (DDU default, DDP available) of high-quality MPCVD diamond components, supporting continuous R&D and manufacturing operations worldwide.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Chemical-mechanical polishing (CMP) is a process that planarizes semiconductor surfaces and is essential for the manufacture of highly integrated devices. In CMP, pad conditioning using a disk with diamond grit is adopted to maintain the surface roughness of the polishing pad and remove polishing debris. However, uneven pad wear by conditioning is unavoidable in CMP. In this study, we propose a contact-area-changeable conditioning system and utilize it to conduct a preliminary study for improving pad lifetime. Using the conventional conditioning method (Case I), the material removal rate (MRR) decreased rapidly after 12 h of conditioning and the within-wafer non-uniformity (WIWNU) increased. However, the results of conditioning experiments show that when using a contact-area-changeable conditioning system, uniform pad wear can be obtained in the wafer-pad contact area and the pad lifetime can be extended to more than 20 h. Finally, the newly proposed conditioning system in this study may improve the CMP pad lifetime.

Tech Support

Original Source

DOI: https://doi.org/10.3390/app11083521

References

1995 - Observations on Polishing and Ultraprecision Machining of Semiconductor Substrate Materials [Crossref]
2020 - Review on modeling and application of chemical mechanical polishing [Crossref]
2004 - Chemical mechanical planarization for microelectronics applications [Crossref]
2010 - Chemical Mechanical Planarization: Slurry chemistry, Materials, and Mechanism [Crossref]
2010 - Effect of CMP Pad and Slurry to STI and ILD Polishing [Crossref]
2008 - Study on Adhesion Removal Model in CMP SiO2 ILD [Crossref]
2005 - A dishing model for STI CMP process [Crossref]
2004 - Characterizing STI CMP Processes with an STI Test Mask Having Realistic Geometric Shapes [Crossref]