LTW Automation Logo Case Studies

| Wafer Handling | Foucault Pendulum | Host Communication |
| SMIF Pod I/O | Transport System | Pod Shuttle |

Front-end Automation of Horizontal Diffusion Furnaces

GaSonics Two-Stack HiPox Oxidation Furnace
Two PRi-2000 Robots
Horizontal Laminar Flow Hoods
Capacity: 600 wafers (200 mm) in four batches
Automatic operation of wafer transfer
Automatic scan for missing wafers
Automatic packing to eliminate gaps
Programmable monitor wafer or test wafer by slot location
Programmable dummy wafers typically at each end of boat
Each wafer is returned to the same cassette slot
Automatic selection of single or multiple wafer pick to optimize transfer speed
Interleaving from 1/4" cassette spacing to 1/8" spacing in quartz boats
Work-cell control of robots and furnaces
SECS II host communication and control
Recipe management
Data capture and reporting
Touch screen user interface

In 1986, one of our customers asked us to participate in automating their diffusion furnace, to be installed in IBM's first 200 mm semiconductor fab. We were already familiar with the furnace having made many of the pressure vessel parts from the beginning stages of the product. In addition to wafer handling automation, IBM asked us to tie in the furnace process-control unit with the robots, thus creating a single entity with which the host computer can communicate. Further, IBM required that the system survive a power outage/failure with no loss of data and the ability to resume operations with a minimum of operator intervention.

The final system consisted of two diffusion furnaces with controllers and two track mounted robots. One robot is used for transporting 25-wafer cassettes and moving wafers from cassettes to 75-wafer quartz boats and one robot to handle the quartz boats and load them into the furnace. Process control automation was handled by using SECS-II to communicate with the two furnace controllers to send and receive recipes, remote start, capture process data in real time, and to communicate with the host computer.

We did the mechanical design, researched and purchased the robots and clean air hoods, made the support frame, and attached the entire unit to the furnace in five months. During that same period our software team designed and created a work-cell controller that would communicate via SECS-I and SECS-II to both furnace controllers, the two robots, and the host computer. This software "work-cell controller" was one of the first such systems to run on an IBM AT (80286) computer platform. Typically such systems ran on much more expensive computers. Testing, debugging, and system integration followed, and final installation and hand-off of the system in the IBM fab occurred about a year after the project start.

Our customer contracted with us to install several more systems, including one in Germany, as we trained their field technicians. The systems are still operational at various fabs around the world.

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World's Largest Foucault Pendulum for the Oregon Convention Center

36 inch diameter bronze pendulum
900 pounds live weight
70' cable length
15' diameter swing
Electro-magnetic control system
18 hour progression
2 million cycles per year

Click on image to see a higher resolution version

Foucault Pendulum Foucault Pendulum

As a vendor to the California Academy of Sciences over the past 60 years, Lathe Tool Works has manufactured most of the world's Foucault pendulums. When artists Kristin Jones and Andrew Ginzel needed a special pendulum for the Oregon Convention Center in Portland, the Academy recommended LTW. Thus began a very interesting project resulting in, according to the Guinness Book of Records, the largest pendulum in the world. Kristin and Andrew named it Principia. Typically Foucault pendulums swing in pits below floor level, knocking over little pins to mark the rotation of the earth under the pendulum. However, this one was to swing 20 feet over the heads of everyone walking through the lobby of the convention center. The pendulum is 36 inches in diameter, weighs 900 pounds, and swings over 15 feet in its 15-second period. The cable anchor is 90 feet off the floor, attached to the roof of the glass towered building.

The design challenge wasn't so much scaling up an existing pendulum and operating mechanism design as it was to recalculate the cable strength and suspension system for safety. We designed the mechanism and at the same time contracted with an outside engineering agency to duplicate our design work from a theoretical aspect. As it turned out, their work agreed with what we had done and we got busy fabricating the unit.

The pendulum is made of two bronze hemispheres, which are first machined, and then put together to make the sphere. After the foundry work was done, we scalloped out the inside of each hemisphere and made dovetail joints at the mating surfaces. Then we set the unit up for shrink fitting. It was a very tense moment when we lowered the heated (expanded) half over the cool half with a crane and it was extremely satisfying when the halves joined forever with a bang. With the ball together, all that was left was machining the outside surface that stretched our machines and our patience to the limit, for three weeks! The final polishing step made it look like a 900-pound Christmas tree ornament.

The pendulum was installed at the convention center in September of 1990. Since then the pendulum has swung over 20 million cycles and it should continue for the next century or so, as long as the electricity to the helper magnet automation stays on.

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SEMI-spec SECS-II Remote Operation on Complex System

SECS I, RS-232 Interface
SECS II messaging protocol
GEM compliant scenarios
One Host Input
Eight SECS II or ASCII Outputs
Intel Hardware Platform
DOS or Windows OS

In 1992 IBM asked LTW to automate an oxidation furnace in a brand new state-of-the-art 200 mm production fab in Fishkill, New York. The space requirements had changed since the last similar automation system for the same type of furnace necessitating a major redesign of the robotics. This time the wafer handling was done by a single track-mounted robot with interchangeable "end-effectors." The robot can handle individual 200 mm wafers, 13-wafer groups, 25-wafer plastic cassettes, and 75-wafer quartz boats. The exact placement of production wafers, control wafers, and blanks in the quartz boats is programmable. Again, IBM wanted host-control, however this time it needed to be more sophisticated and support complex "user-defined" reports and data capturing capabilities. For this system LTW implemented a complete SEMI-spec GEM and SECS-protocol based communications package for remote control via a host computer.

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200 mm SMIF Input/Output Device

All pneumatic operation provides quiet, smooth, simple operation
Control modes: manual, semi-automatic, tool controlled (via "parallel" interface), or host remote control
Parallel interface provides tool hardware handshake and safety interlock
Controllable Pod Latching
Class I cleanliness

In the semiconductor manufacturing industry the steady shift to pod technology has precipitated the need to adapt many tools, previously designed for open cassette operation, to make them compatible with SMIF pods. LTW was asked by BYE/Oasis to prototype an automated I/O device for 200 mm wafer pods. That prototype became a product called SMIF_Z. The first unit was unique in that it had entirely pneumatic control and was very simple both from a maintenance point of view and in operation. However, we all knew the end users would want more bells and whistles so we modified this design to be an electro-mechanical device with all that entails. We maintained the air cylinder actuators, but replaced the control system with a microprocessor. This change made it possible for the device to be programmable, remotely controlled, and to deal with and report error conditions and safety related events. The SMIF_Z can be controlled in three different ways: through a manual control switch, via a simple tool oriented interface, and/or SECS protocol communications typically from a host computer.

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Overhead Pod Transport System

Modular design
Turntables and elevators
Bi-directional transport
Variable speed
Programmable acceleration
Class I compatible
Open Cassette or Pod
High level communication interface
RS-485 network
Fault tolerant/self-diagnostic

Although much of this project is proprietary to one of our clients, we designed and built a railroad style SMIF-pod transport system. The system goals were to be modular, programmable, and reliable.

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Curved Track Shuttle for 300 mm Pods

Bi-directional pod transport
Pneumatic for clean, smooth, and quiet operation
Low maintenance
Designed to be Class I compatible
High-level communication interface
RS-485 network
Opto-mechanical pod present detectors

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