CMP Pad Polyurethane Formulation for High Removal Rate
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Solution Overview
Problem
Existing chemical mechanical polishing (CMP) pads are inadequate for effectively polishing three-dimensional semiconductor or memory substrates with thick oxide films and large features, as they fail to provide the necessary removal rates and planarization for substrates with dimensions beyond previous standards.
Innovation Solution
A CMP polishing pad with a low damping component, featuring a polyurethane reaction product from a thermosetting reaction mixture comprising 4,4′-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) or mixtures with 4,4′-methylene-bis-o-(2-chloroaniline) (MbOCA) and a polyisocyanate prepolymer, providing a high shear storage modulus and controlled damping for enhanced removal rates and long length scale planarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CMP polishing pads are used, then polishing of standard substrates is achieved, but removal rate is insufficient for thick oxide films
Solution Approach 1:
The patent modifies the polyurethane polymer composition by controlling the NCO index (excess isocyanate) to be greater than 100, specifically in the range of 100-130. This parameter change in the polymer chemistry creates a more reactive material that achieves higher removal rates on thick oxide films while maintaining polishing reliability through controlled chemical-mechanical action.
Solution Approach 2:
The invention uses a composite polyurethane formulation combining polyether polyol, polyester polyol, and excess isocyanate groups to create a material with optimized properties. This composite approach allows the pad to simultaneously provide mechanical removal capability and chemical reactivity for enhanced removal rates on challenging substrates.
2Productivity
If high removal rate is achieved, then thick oxide films are removed effectively, but planarization over long length scales deteriorates
Solution Approach 1:
The patent optimizes multiple parameters including the polyol ratio (polyether to polyester), NCO index, and Shore D hardness to achieve a balance between removal rate and planarization. The specific formulation with NCO index >100 and Shore D hardness of 60-90 creates a pad that maintains structural integrity over large areas while providing aggressive removal where needed.
Solution Approach 2:
The polyurethane composition is designed to provide different properties in different aspects: high chemical reactivity and softness for localized removal on features, while maintaining overall structural rigidity for long-length-scale planarization. This local quality differentiation is achieved through the composite polyol system and controlled crosslinking.
3Stability of the object's composition
If damping component is increased, then pad stability is improved, but removal rate on large features decreases
Solution Approach 1:
The patent reduces the damping component (loss modulus) of the polyurethane pad by optimizing the polyol composition and NCO index. This parameter change creates a pad with lower energy dissipation that maintains stability while allowing more effective mechanical action for high removal rates on large feature substrates like 3D NAND.
Solution Approach 2:
The polyurethane formulation creates a dynamically responsive material that adapts its mechanical properties during polishing. The excess isocyanate groups and specific polyol ratio create a structure that remains stable under static conditions but becomes more compliant and reactive under the dynamic conditions of CMP polishing, enabling high removal rates without sacrificing stability.
Data Source
AI summary
The present invention provides a chemical mechanical (CMP) polishing pad for polishing three dimensional semiconductor or memory substrates comprising a polishing layer of a polyurethane reaction product of a thermosetting reaction mixture of a curative of 4,4′-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) or mixtures of MCDEA and 4,4′-methylene-bis-o-(2-chloroaniline) (MbOCA), and a polyisocyanate prepolymer formed from one or two aromatic diisocyanates, such as toluene diisocyanate (TDI), or a mixture of an aromatic diisocyanate and an alicyclic diisocyanate, and a polyol of polytetramethylene ether glycol (PTMEG), polypropylene glycol (PPG), or a polyol blend of PTMEG and PPG and having an unreacted isocyanate (NCO) concentration of from 8.6 to 11 wt. %. The polyurethane in the polishing layer has a Shore D hardness according to ASTM D2240-15 (2015) of from 50 to 90, a shear storage modulus (G′) at 65° C. of from 70 to 500 MPa, and a damping component (G″/G′ measured by shear dynamic mechanical analysis (DMA), ASTM D5279-08 (2008)) at 50° C. of from 0.06 to 0.13.