Polyurethane composition for cmp pads and method of manufacturing same

Abstract

Polyurethane composition based on a certain polyether and polyester prepolymer reaction mixture, wherein the composition is utilized in manufacturing chemical mechanical polishing / planarizing (CMP) pads. The CMP pads have low rebound and can dissipate irregular energy as well as stabilize polishing to yield improved uniformity and less dishing of the substrate.

Description

[0001]This application is a continuation of prior U.S. application Ser. No. 12 / 537,862, filed Aug. 7, 2009, which is incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to chemical mechanical polishing / planarization pads based on a novel composition, and method for manufacturing same. Specifically, the CMP pads are polyurethane pads derived from a polyether / polyester prepolymer reaction mixture, wherein the resulting pads exhibit a moderate hardness with high porosity, a high tear resistance and high damping performance.BACKGROUND OF THE INVENTION[0003]Chemical mechanical planarization, also known as chemical mechanical polishing or CMP, is a technique used to planarize the top surface of an in-process semiconductor wafer or other substrates, such as optical, magnetic type of substrates in preparation of subsequent steps or for selectively removing material. The technique employs a slurry that can have corrosive and abrasive properties in conju...

AI Technical Summary

Benefits of technology

[0008]It has been found that CMP pads with low rebound tend to absorb relatively high amounts of energy during cyclic deformation, causing less dishing during polishing and yielding better WID uniformity. Stiffness is likewise an important consideration for WID uniformity and prolonged pad life. One attempt to describe damping effects quantitatively has used a parameter named Energy Loss Factor (KEL). KEL is defined as the energy per unit volume lost in each deformation cycle. Generally, the higher the value of KEL for a pad, the lower the elastic rebound and the lower the observed dishing.

[0009]To increase the KEL value, the pad can be made softer. However, this approach tends to also reduce the stiffness of the pad. The reduced stiffness results in decreased planarization efficiency and increases dishing due to conformation of the pad around the device corner.

[0010]Another approach for increasing the KEL value of the pad is to alter its physical composition in such a way that KEL is increased without reducing stiffness. In an attempt to attain the right balance, it has been found that a formulation of co-cured polyether and polyester prepolymers in a particular weight percentage provides a polyurethane chemical polishing pad with high damping properties, low rebound and dishing. Specifically, in a preferred embodiment of this invention, the polyurethane material is a reaction mixture of a polyether prepolymer in an amount of about 60-80 weight percent (wt %) with a polyester prepolymer in an amount of 20-40 wt %. Naturally, the microcellular pad formulation includes surfactants, frothing agents, curatives, and optionally other additives, such as fillers. Thus, the polyurethane microcellular the CMP pads of the preferred composition exhibit a high damping performance, while retaining moderated hardness with high porosity and high tear resistance.

[0011]The invention addresses demands placed on CMP pads used in the manufacture of traditional and advanced electronic, optical or magnetic components and has many advantages. The highly damping polymeric material of the invention has high energy dissipation and can absorb irregular bouncing and oscillating energy at the polishing interface to yield better uniformity. CMP pads manufactured from this material provide good WIW and WID uniformities, smooth polishing performance, low dishing and / or erosion. The pads generally have a high degree of stable hardness or stiffness, providing good planarization performance and long pad life.

[0014]Advantageously, the CMP pad can be prepared utilizing prepolymers that are commercially available, thus enabling and simplifying the overall fabrication process. Aspects of gas frothing and casting can be carried out using standard techniques or equipment. In certain chemistry formulations of the pad, frothing time can be decreased without sacrificing foaming characteristics and quality.

Problems solved by technology

However, this approach tends to also reduce the stiffness of the pad.

The reduced stiffness results in decreased planarization efficiency and increases dishing due to conformation of the pad around the device corner.

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