Kinematic Prediction and Experimental Demonstration of Conditioning Process for Controlling the Profile Shape of a Chemical Mechanical Polishing Pad

At a Glance

Metadata	Details
Publication Date	2021-05-11
Journal	Applied Sciences
Authors	Hanchul Cho, Taekyung Lee, Doyeon Kim, Hyoungjae Kim
Institutions	Korea Institute of Industrial Technology
Citations	7
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for CMP Conditioning

Executive Summary

This research successfully demonstrates a methodology for kinematically predicting and experimentally controlling the wear profile of Chemical Mechanical Polishing (CMP) pads, a critical factor for achieving ultra-fine semiconductor uniformity.

Core Challenge Addressed: Maintaining the flatness and uniformity of the CMP pad profile over extended conditioning periods, which directly impacts final wafer quality.
Methodology: A kinematic simulation was developed based on the trajectory density of diamond abrasives (from the conditioner disc), accurately predicting pad wear profiles across various Relative Occupancy Time (ROT) conditions.
Key Achievement (Flatness): Through optimization of the conditioning arm overhang (return point set to 375 mm) and disc size (60 mm diameter), the maximum pad thickness deviation was maintained at 10 µm or less over 2 hours of continuous conditioning.
Material Requirement: The success of the kinematic model and experimental control relies fundamentally on the consistent geometry and high durability of the diamond abrasives used in the conditioner disc.
6CCVD Value Proposition: 6CCVD provides the necessary high-quality, custom-dimensioned MPCVD Polycrystalline Diamond (PCD) and Single Crystal Diamond (SCD) materials required to manufacture next-generation, ultra-uniform diamond conditioner discs.

Technical Specifications

Data extracted from the experimental demonstration of controlled CMP pad conditioning.

Parameter	Value	Unit	Context
Maximum Pad Thickness Deviation	< 10	µm	Maintained under controlled conditions for 2 hours
Pad Diameter (IC1000 series)	760	mm	Total pad size
Nominal Conditioner Disc Diameter	100	mm	Standard configuration (50 mm radius)
Optimized Conditioner Disc Diameter	60	mm	Simulated size to reduce edge slope zone
Conditioner Rotation Speed	103	rpm	Fixed speed during analysis
Pad Rotation Speed	97	rpm	Nominal speed (varied 96-99 rpm)
Conditioning Arm Sweep Speed	7	cycles/min	Nominal speed (varied 8-10 sweeps/min)
Conditioning Load	40	N	Applied force during conditioning
Optimized Return Point (Overhang)	375	mm	Used to increase pressure and ensure flat wear profile
Pad Profiler Resolution	1	µm	Contact dial gauge measurement precision

Key Methodologies

The study utilized a combination of kinematic modeling, simulation, and in situ measurement to achieve precise control over pad wear.

Kinematic Modeling: Developed a mathematical model describing the relative motion of three factors: pad rotation, conditioner rotation, and conditioning arm sweep speed.
Trajectory Density Calculation: The trajectory of the working diamond abrasives was calculated and integrated within specific areas (dx and dy) to derive the relative wear amount, which is proportional to the pad wear profile.
Simulation Development: A prediction simulation (using LabVIEW) visualized the center trajectory and the full trajectory of the diamond abrasives, allowing for rapid verification of conditioning parameters.
Relative Occupancy Time (ROT) Control: The sweep zone was divided into 11 or 15 radial zones, and eight different ROT profiles (e.g., Even, Linear Center Fast, Parabolic) were tested to generate specific wear shapes.
Experimental Validation: Conditioning was performed for 10 minutes (and 2 hours for long-term tests) using a diamond conditioner disc (72 grit count) under a 40 N load. Pad profiles were measured before and after abrasion using an in situ profiler (1 µm resolution).
Optimization via Overhang: Experimental results confirmed that increasing the overhang length (return point from 350 mm to 375 mm) dramatically increased pressure at the edge, ensuring a flat wear profile over the entire pad surface.

6CCVD Solutions & Capabilities

The successful control of pad wear relies entirely on the consistency and durability of the diamond abrasive material. 6CCVD specializes in providing the high-specification MPCVD diamond required to manufacture the next generation of ultra-precision CMP conditioner discs.

Applicable Materials

To replicate or extend this research, the diamond conditioner disc requires materials with exceptional uniformity, hardness, and thermal stability.

Application Requirement	6CCVD Recommended Material	Rationale
Large-Area Abrasive Discs	Polycrystalline Diamond (PCD)	Available in custom dimensions up to 125 mm. PCD offers superior toughness and fracture resistance, ideal for high-load, large-area conditioning applications.
Ultra-Precision Grit/Tips	Single Crystal Diamond (SCD)	For applications requiring the highest possible geometric precision and lowest surface roughness (Ra < 1 nm). SCD ensures maximum consistency in abrasive geometry (grit count 72).
Conductive/Electro-Chemical Conditioning	Boron-Doped Diamond (BDD)	If the conditioning process were to be extended to include electrochemical planarization, BDD provides the necessary high conductivity and chemical inertness.

Customization Potential

The research highlights the need for precise control over conditioner disc geometry (e.g., reducing diameter from 100 mm to 60 mm) and the ability to integrate the diamond material into the conditioning arm.

Custom Dimensions: 6CCVD supplies PCD and SCD plates/wafers in custom dimensions up to 125 mm, allowing researchers to rapidly test various conditioner diameters (e.g., 60 mm, 100 mm) as explored in the simulation (Figure 10).
Precision Processing: We offer in-house laser cutting and shaping services to ensure the diamond material meets the exact geometric tolerances required for kinematic modeling accuracy.
Advanced Metalization: The integration of the diamond abrasive into the conditioner requires robust bonding. 6CCVD provides internal metalization services (Au, Pt, Pd, Ti, W, Cu) for reliable mounting and thermal management.
Surface Finish: Our polishing capabilities (Ra < 5 nm for inch-size PCD) ensure the base diamond material is perfectly flat, minimizing initial geometric errors that could compromise the 10 µm flatness target.

Engineering Support

The successful implementation of this kinematic control strategy requires deep expertise in both material science and tribology.

In-House PhD Team: 6CCVD’s engineering team, composed of PhD material scientists, can assist researchers and engineers in selecting the optimal diamond material (SCD vs. PCD), grit density, and thickness (0.1 µm - 500 µm) to replicate or extend the results achieved in this CMP pad profile control project.
Global Supply Chain: We offer global shipping (DDU default, DDP available) to ensure rapid delivery of custom diamond solutions worldwide.

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

View Original Abstract

The uniformity of the wafer in a chemical mechanical polishing (CMP) process is vital to the ultra-fine and high integration of semiconductor structures. In particular, the uniformity of the polishing pad corresponding to the tool directly affects the polishing uniformity and wafer shape. In this study, the profile shape of a CMP pad was predicted through a kinematic simulation based on the trajectory density of the diamond abrasives of the diamond conditioner disc. The kinematic prediction was found to be in good agreement with the experimentally measured pad profile shape. Based on this, the shape error of the pad could be maintained within 10 μm even after performing the pad conditioning process for more than 2 h, through the overhang of the conditioner.

Tech Support

Original Source

DOI: https://doi.org/10.3390/app11104358

References

1927 - The Theory and Design of Plate Glass Polishing Machines
2002 - Pad conditioning in chemical mechanical polishing [Crossref]
2009 - Novel diamond conditioner dressing characteristics of CMP polishing pad [Crossref]
2004 - A theory of pad conditioning for chemical-mechanical polishing [Crossref]
2010 - Investigating the effect of diamond size and conditioning force on chemical mechanical planarization pad topography [Crossref]
2009 - A Material Removal Model for CMP Based on the Contact Mechanics of Pad, Abrasives, and Wafer [Crossref]
2011 - Effect of CMP conditioner diamond shape on pad topography and oxide wafer performances [Crossref]
1997 - Stress distribution in chemical mechanical polishing
1997 - Von Mises Stress in Chemical-Mechanical Polishing Processes [Crossref]