Annular Polishing Pad for Wafer Notch Integrity
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Solution Overview
Problem
Wafers with notches indicating crystal axis orientation are prone to chipping or cracking during polishing, leading to waste due to inadequate polishing techniques for these specific shapes.
Innovation Solution
A polishing pad with an annular shape and a polishing surface composed of a binder resin, fibers, and pores, which allows for excellent followability and minimizes chipping or cracking by pressing against the notch, using a base material of thermoplastic polyurethane and polyethylene terephthalate fibers, and retaining polishing particles within the base material or pores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polishing pads are used on wafers with notches, then the polishing process can be performed, but the wafer chips or cracks near the notch resulting in wafer waste
Solution Approach 1:
The polishing pad employs different material properties in different regions: the base material (thermoplastic polyurethane) provides flexibility and followability to conform to the notch shape, while the embedded polishing particles (alumina, silica, or diamond) provide cutting action. This local differentiation allows the pad to simultaneously accommodate the notch geometry and perform effective polishing without causing damage.
Solution Approach 2:
The polishing pad is constructed as a composite material system combining thermoplastic polyurethane binder resin with reinforcing fibers (polyester, polypropylene, or aramid) and abrasive polishing particles. This composite structure integrates the flexibility needed to follow the notch contour with the mechanical strength and abrasion resistance required for effective polishing, preventing both chipping and cracking.
2Reliability
If the polishing pad presses against the notch to prevent chipping, then wafer integrity is improved, but the complexity of the polishing process increases
Solution Approach 1:
The polishing pad's base material is designed to automatically conform to the notch shape through its inherent flexibility and elastic properties. The pad self-adjusts to the substrate geometry without requiring external guidance mechanisms or complex positioning systems. The binder resin and fibers work together to provide passive followability, eliminating the need for active control systems.
Solution Approach 2:
The thermoplastic polyurethane binder resin exhibits temperature-dependent property changes that aid in followability. At polishing temperatures, the material becomes slightly more compliant, allowing it to conform to the notch shape. The fibers provide structural reinforcement that maintains shape memory. This parameter change enables the pad to adapt to complex geometries without increasing process complexity.
3Ease of operation
If a soft polishing pad is used to follow the notch shape, then followability is improved, but wear resistance decreases
Solution Approach 1:
The pad combines soft thermoplastic polyurethane binder resin with high-strength fibers (polyester, polypropylene, or aramid) and abrasive particles. The fibers provide tensile strength and structural integrity that prevent excessive wear, while the binder resin maintains flexibility for followability. The abrasive particles embedded in the matrix provide cutting action. This multi-component composite achieves both softness for conformability and hardness for wear resistance.
Solution Approach 2:
Different components perform different functions: the binder resin provides flexibility and followability, the fibers provide structural strength and wear resistance, and the polishing particles provide abrasive cutting action. This local functional differentiation allows the pad to be soft enough to conform to notches while remaining durable enough to resist wear during the polishing process.
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 polishing pad effectively reduces wafer wastage by preventing chipping or cracking near the notch during polishing, ensuring smooth surfaces and efficient polishing with minimal wear and no unpolished parts, while allowing for high productivity and wear resistance.
Implementation Method 1
polishing particles retained in the base material or in the pores
Implementation Method 2
pressing the polishing surface against the notch
Data Source
AI summary
A polishing pad (1) of the present teaching is formed in an annular shape and is centered on a first rotation axis center (P). The polishing pad (1) has a first surface (1a), a second surface (1b), and a polishing surface (3) that connects the first surface (1a) and the second surface (1b) on an outer circumference of the polishing pad (1). The polishing pad (1) polishes a notch (7), which is formed in a disc-shaped wafer (5) and indicates an orientation of a crystal axis, by rotating around the first rotation axis center (P) while pressing the polishing surface (3) against the notch (7). The polishing surface (3) is formed of a polishing body that includes: a base material composed of a binder resin and fibers and having a plurality of pores formed therein; and polishing particles retained in the base material or in the pores.