This is a very interesting solution for the semiconductor industry. Integrated circuits are made by extremely precise photolithography on large silicon wafers. These wafers must be essentially perfect by every measure. A rotary silicon wafer polishing machine was needed to provide a precise oscillation pattern. Hoffman gained the project through referral by a satisfied customer.
- Rigidity and a small envelope were both required by the solution
- We had to maintain stiffness of the spindle that drives the rotary polishing head
- Our challenge was to couple a drive motor producing sufficient torque without changing the machine’s ability for the spindle to provide a soft radial force and natural positioning
- The solution was use of a welded metal bellow as the flexible coupling element: it provided by torsional stiffness and radial softness
The application is semiconductor wafer polishing for a Silicon Valley chip maker. The design called for precision, high torque and extreme stiffness on a reversing indexing table. Absent off-the-shelf solutions, Hoffman was chosen to design and build a custom assembly.
The customer was unable to find a rotary motion coupling that satisfied their needs for precision and torque. Since we were replacing an existing problematic coupling, we had limited space to work in.
The required torque was high for the allotted space. The customer needed a very stiff coupling that allowed some misalignment of the drive train. It had to be a dry coupling for cleanliness and to avoid contamination of the clean room environment. The design materials had to withstand potential corrosion typical in the chemistry environment of semiconductor manufacturing.
We started with a standard coupling and ended up with a totally custom coupling that saved the customer money by simplifying their design. In order to stiffness up the coupling we used a special material that had more strength and stiffness. We integrated a QD as one half of the coupling to save space. The other hub was a custom part to fit the limited space and mate with the machine. We used a pilot to insure concentricity. To transmit the torque we used a face keyway and a series of screws. We used all stainless steel hardware to prevent corrosion. To keep cost down we nickel plated the major parts.