CASE STUDY
BAKE-COOL MODULE
PROBLEM
A semiconductor equipment manufacturer was developing a Resist Processing System. To expedite product introduction, the client needed to outsource a key module of the overall system. This module had to integrate seamlessly into their design and manufacturing process.
BAKE COOL MODULE SPECIFICATIONS AND FEATURES
The module had to interface with the overall system and had to:
- Communicate with the top level system via a standard interface.
- Accept wafers delivered to the module via the systems' main robotic arm.
- Control operational functions within the module including: Three separate actuators under servo motor controls, thermal control of the bake plate surface, vacuum wafer pick-up, vacuum transport arm, and vacuum wafer hold down on the bake and chill plates.
- Hand off finished wafers to the main robotic arm.
- Size envelope to system specifications: 18.0" L X 16.0" H x 9.0" W
- Design for manufacturing and assembly.
KEY FEATURES
- Proximity bake, fixed or programmable, ensures bake uniformity and minimizes effects of backside contamination. Selectable full contact bake.
- Programmable temperature range of 35-365º in 0.1 degree increments.
- Module controller combined with PID temperature control provides guaranteed stability of bake and chill process. Software algorithm controls plate energy transfer, thus enabling the module to reach programmed substrate temperature more rapidly.
- Chill station features contact, proximity, and moving pin proximity substrate handling, provides active temperature control to ±0.1º.
SOLUTION
The design and manufacture of the module involved the collected disciplines of mechanical, electronic, and software engineering as well as support from mechanical design, PCB layout, techs and machine fabrication shop services.
Wafer bake sub-assembly
The wafer bake assembly receives wafers from the main robotic arm. The wafers, having
Photo-resist applied, must now be baked as part of the wafer manufacturing process. The temperature uniformity of the bake plate is critical in this process. To meet this requirement, the bake plate was designed using a custom film heater in conjunction with minimizing surface contact of the heated plate assembly and the main mount plate. The design was modeled using a thermal FEA program. The analysis helped define the heater watt density vs. radial location and predicted bake plate temperature uniformity of 0.1 C.
Transport System
The transport system consists of two vacuum pick-up actuators and a vacuum pick-up shuttle mechanism. The actuators accept and hand-off wafers at the bake and chill stations from and to the main robotic handler. Additionally, the actuators position the wafers to either be proximity baked (slightly displaced from the bake plate) or direct contact baked with vacuum hold down assist. The shuttle picks up the baked wafer after processing and hands it off to the vacuum pick-up actuator at the chill station. The vacuum actuator lowers the wafer to the chill plate and vacuum is applied between the plate and wafer to efficiently cool the wafer. The vacuum is removed and the chill plate actuator raises the wafer for hand-off to the main robot.
Electronics
The system involves a custom PCB that controls the functions of the bake-chill module as well as communications with the main system. Within the module the board controls the three motor drives, heaters, vacuum sequencing, and heater temperature.
Manufacture
Eight units were built as prototypes and full documentation was provided to the client.
View showing bake and chill plates and shuttle transport with vacuum end effector.
Overall view of the Bake-Cool Module
|
