Stable Motion for When the Chips Fly

--Richard Mandel

Most every facet of semiconductor manufacture has an element of risk involved -- thin, brittle disks of silicon to be moved in and out of machines; atom-scale layers to be built up and etched; layout and connections made on real estate that trades acres for micro-handfuls of angstroms. Precision and smoothness are the paladins of the industry, frequently performing in Class 10,000 cleanrooms and high vacuums. And, by the way, speed is needed to achieve management's production goals.

Case history 1: wafer movement

Brooks Automation, Chelmsford, MA, has been involved in automated systems for the semiconductor industry since 1978. Today their focus is on substrate handling robots, modules, software controls, and fully integrated cluster tool platforms that put several chip processes into a single machine to reduce floor space and handling distances. Brooks prides itself on innovation -- many advances seen today in substrate-material-handling products were based on original Brooks designs.

Vacuum Cassette Elevator:
by Brooks Automation

Early in the company's history, they elected to use motors from Pittman, Harleysville, PA, for critical motion handling tasks. Pittman motors are currently used in most all of the Brooks catalog, primarily, according to Brooks purchasing manager Rich Stecchi, "because of their quality, their low cost, and that the company is good to work with."

One system that is critical in its motor requirements is Brooks' Vacuum Cassette Elevator Modules. These devices move cassettes of 20 to 26 silicon wafers, each up to 200mm in diameter, within a self-contained, environmentally-isolated chamber that can maintain a vacuum down to 10^-6 Torr. The module is passed from process machine to process machine, or process machine to factory interface, dropping a vertical door to allow wafers from the cassette to transfer into the work zone. Transfer of the unit is handled by a robotic system or a human operator.

The cassette itself is moved vertically to present each wafer in its turn. This vertical motion is handled by a Pittman brushed DC motor that drives the lift via a toothed belt, which is also used for reduction. The motor is isolated from the vacuum and temperatures inside the process module, simplifying the requirements for the motor. The system moves the five pound cassette at a profiled rate of 35mm/sec, with a vertical position repeatability of ±0.1mm, through a total range of 231mm. Pittman installs a Brooks-specified HP encoder on the motors, and the controller is of a Brooks design.

For more information, contact:

Brooks Automation, 15 Elizabeth Dr., Chelmsford, MA 01824. 508-262-2400. http://www.brooks.com Circle 420.

Pittman, 343 Godshall Dr., Harleysville, PA 19438. 877-PITTMAN. http://www.pittmannet.com Circle 421.

Case history 2: wire bonder

Swiftly approaching a half century since its founding, Kulicke & Soffa Industries, Inc., Willow Grove, PA, designs and manufactures integrated assembly equipment for the semiconductor manufacturing industry. Products include wafer and hard materials dicing, die bonding and wire bonding machines.

K & S's current generation of wire bonding equipment provides broader process capability at an increased degree of assembly productivity. The initial offering was the Model 8020 automatic gold ball bonder, capable of bonding any IC package thrown at it, from low lead count PDIPs to fine pitch BGA packages. The Model 8028, introduced earlier this year, was based on the 8020 platform, but with a 15% increase in throughput and a larger bonding area.

The bond head of these units, which is comprised of the bond head assembly and the moving optics assembly, moves in the Z axis. The IC package being processed rides on an X-Y table that moves on Model RNG linear bearings supplied by Schneeberger. The bearing has a small cross-section, providing a highly loadable guidance system. According to John Molnar, engineering manager for the XYZ systems, the Schneeberger bearings were selected because they had the requisite stiffness to support table speeds of 2.54 millimeters in 15 milliseconds, and still achieve resolutions of 0.1 microns. Wire bonding speeds are up to 85 msec.

For more information, contact:

Kulicke & Soffa Industries Inc., 2101 Blair Mill Road, Willow Grove, PA 19090. 215-784-6000. Circle 423.

Schneeberger Inc., 11 de Angelo Drive, Bedford, MA 01730. 781-271-0140. http://www.schneeberger-usa.com Circle 424.