CMP retaining rings

A substantial proportion of the overall retaining ring cost consists of the ring material cost. Choosing the best fitting plastic tube size for the machined retaining ring enables less machined waste and effort, significantly impacting the material cost. For example, changing from industry-standard size OD360/ID290 mm with 58,3 kg/m to the smaller size OD350/ID300 mm of TECAPEEK CMP with 42,2 kg/m results in up to 27 % material waste and cost savings. With almost 4000 different combinations of polymers and tube dimensions, Ensinger offers the best tube size product portfolio in the industry. 

With our PPS material TECATRON SX natural and PEEK material TECAPEEK SX natural Ensinger offers a wide range of tube dimensions for the semiconductor industries demands. In addition to a wide range of tube sizes in stock, custom order dimensions are available on request.

Please contact us for sizes not mentioned in the above overview. We will check for customer specific settings in order to get as close as possible to the final part size.

The retaining ring material is the main factor influencing the ring wear rate. Lower wear resistance leads to frequent changing of the rings and thus contributes to a reduced tool utilization and increased cost of ownership. Generally, PEEK offers up to three times better wear resistance than PPS, significantly extending ring lifetime. Further, PEEK CMP offers up to 20 % better wear resistance than standard industry PEEK. 

Minor differences in the material properties of the CMP retaining ring can alter the micro-texture of the pad, cause different amounts of pad fragments and shavings, and result in different shapes of pad asperities. For example, compared to using competitor PPS, Ensinger's TECATRON CMP shape wears the pads in a manner so that the pad asperities are optimised for enhanced material removal as well as reduced defects. Reducing the level of defective dies and improving yield has significant impact on the cost of ownership.
More information: Case Study CMP Retaining Ring

Other sources of micro-scratches are inner ring groove wear (also known as side attacks), causing uneven inner ring walls and inducing slurry and other particles to adhere to the wall, agglomerate, later dislodge, and scratch the wafer. Inner groove wear is not much of an issue with PPS or PC as the material wears on the face of the ring at a rate so the inner groove is always seeing new material. However, high performance materials like PEEK provide strong wear resistance on the face of the ring so that inner groove wear can occur and cause excessive defects. The property profile of the ring material, in particular the balance of ductility and hardness, has an impact on the inner groove wear behaviour. Ensinger has developed the shape TECAPEEK CMP with an optimised property profile that enables reduced inner groove wearing compared to standard PEEK.  
Another influencing factor for causing inner groove wearing is the distortion of ring roundness. Deformation while wearing can result by the release of residual stress in the material which is induced by the molding process. All Ensinger CMP materials are produced via extrusion, minimizing residual stress levels, and enhancing crystallinity, enabling higher dimensional stability than other processing methods such as injection molding.  

Consistent flatness and fewer ring thickness deviations are vital for minimizing pad deformation and rebounding, which causes irregular material removal and over-polishing at the wafer edges. Better uniformity of the material removal rate (MRR) enables lower within-wafer nonuniformity (WIWNU) and has a significant impact on yield. Generally, a lower residual stress level in the material of the retaining ring enables better retaining ring flatness and contact angle. Ensinger's tube materials for CMP retaining rings are manufactured using extrusion technology, which is a slow and continuous process enabling lower residual stress levels than other manufacturing methods such as injection molding. Extruded rings enable more consistent property profile than injection molded rings as there is no weld line, which also contributes to better dimensional stability.  

Ion impurities of the polymer or the additives can leach out and cause contaminations. All Ensinger CMP material grades use pure polymers, avoiding the risk of contamination. Besides the purity of the base material, impurities can also be molded-in during the manufacturing of the material. In general, the extrusion process enables better control of product and quality consistency than injection molding, lowering risks of contamination. Additionally, all Ensinger CMP material grades undergo more thorough quality controls than general-purpose grades, resulting in higher safety from foreign particles. 

 

Test in accordance with ICP-MS, concentration levels stated in ppm; (n.t.= not tested)

Ensinger runs efficient stock management and global demand planning systems to ensure that we provide the best availability and delivery performance of CMP tube materials in the industry. Warehouses all around the world are extensively stocking our CMP materials. Moreover, close partnership and supply assurances with premier raw material suppliers enable Ensinger to minimize risks of delivery bottlenecks.