Semiconductor Processing Chuck Heaters
In semiconductor processing, electric chuck heaters are used to heat the surface of a chuck, which is a device that holds a wafer in place during processing. The chuck is typically made of aluminum or copper and is used to hold the wafer during the various processing steps, such as photolithography, etching, and deposition. The chuck is typically cooled to prevent thermal damage to the wafer during processing, but it must also be heated to maintain a consistent temperature and prevent thermal gradients across the wafer.
The electric chuck heater consists of a heating element, typically made of resistive wire, that is embedded in the chuck. When current is passed through the heating element, it generates heat, which is conducted through the chuck and heats the surface of the chuck. The temperature of the chuck is controlled by adjusting the current flowing through the heating element.
The use of electric chuck heaters in semiconductor processing is important for several reasons. First, it helps to maintain a consistent temperature across the wafer, which is important for maintaining process repeatability and yield. Second, it helps to prevent thermal gradients across the wafer, which can cause warping and other defects. Finally, it can help to prevent contamination of the wafer by preventing condensation on the chuck surface.
Mini Clean Flow (MCF) Air Heater – Three Phase
BACKGROUND
The application requirement was a 2” Stainless Steel heater capable of 120 CFM with a 250⁰C outlet temperature. The inlet temperature was ambient air. The heater required two Conflat Flanges (CF2.75), which could be used in a parallel flow configuration at the customer site. The heater needed to be air tight.
SCOPE
MCF – Three Phase:
- 250⁰C @ 120CFM using (2) units in a parallel flow pattern
- Stainless steel 304, all wetted parts
- Pressure tested to 90 PSI (or equivalent 5 x 10 ¯⁴ ATM, cc/sec or better)
- 3-phase with three heated zones
- (3) independent internal type “K” thermocouples for each zone
- 11KW (± 10%) , 240 Volt, 3-phase (or 1-phase optional)
- 36” Lead wires for each zone with 12” wire braid for strain relief
- 304SS CF 2.75 inlet and outlet flange
- Medium being heated: Air, ambient
- He Leak Tested = 5 x 10¯⁴ ATM, CC/sec or better
OUTCOME
The heater was laser welded on the flanges and brazed on the heater zones. The heater helium leak test passed up to 1 x 10 ¯⁸ cc/sec in during the testing phase. There were no problems heating ambient air at 2.5CFM to 200°C during the live power test at BCE. The part was cleaned and passed the required 700 Volt DC Hi-pot test for 5 seconds @ 0.5mA.
Mini Clean Flow (MCF) – Large DI Water Heater
BACKGROUND:
Deionized water application requiring the recirculation of 3 gallons per minute to reach 66ºC in 2 hours. NEMA 4 moisture resistant housing was required.
SCOPE:
MCF – Large DI Water Heater:
- Temperature from 18ºC to 66ºC in 2 hours
- 316 Stainless Steel All wetted parts
- Pressure tested to 90 PSI
- NEMA 4 Housing
- RTD, 3-wire 100 ohm process sensor built-in near outlet
- An additional TC for bottom temperature read
- 16KW (± 10%) , 208 Volt, 3-phase
- Mounting threads on the bottom of the assembly
- Medium being heated: Deionized Water (DI Water)
- Recirculate at 3gpm
OUTCOME:
The heater zones were individually heated at lower voltage then pressure tested up to 90 PSI at 20ºC - 25ºC. The typical ramp temperature for a bench test prior to shipping is 100ºC. The response time in an air medium environment was immediate as the temperature was achieved in under 20 minutes. All zones passed the recommended 700 VDC for 5 seconds on the Hi-Pot test prior to shipping. The heater was cleaned & packaged then sent out for delivery.
Vacuum Chamber Heater Platen 350mm
BACKGROUND
Find a solution in a Vacuum Chamber for the testing and processing of silicon and glass components ~650⁰C. The heater surface, 350mm x 300mm x 12.7mm thick, was flat with no lift pin holes or gates to hold the product in place. The long length cold pin section exiting from the center of the heater to the flange, needed to be long enough to exit into the atmosphere. A slotted designed bottom plate was welded to keep the heat source in place and increase heater efficiency.
SCOPE
The Vacuum Heater Platen:
- Temperature 650⁰C-700⁰C
- 18” Long cold pin section with CF Vacuum Flange on the bottom
- Helium Leak rate of 1 x 10̄¯9 cc/sec He on CF Flange only
- 300mm x 350mm x 12.7mm thick for silicon and glass products
- Thermocouple built-in for over-temp protection or control
- 2,400 Watt (± 10%) , 240 Volt
- Mounting threads on the bottom of the assembly
- Material: 304 Stainless Steel
OUTCOME
The Vacuum Heater Platen was ramped to 650⁰C at 75% of power (1800 watt) in atmosphere with a ceramic fiber insulation cover. After a 1 hour ramp, the heater reached 650⁰ C and was turned off to let cool. There was discoloration on the top surface, however this is expected in atmosphere at this temperature. The electrical specifications were checked again and the heater was cleaned & packaged for delivery.
ALD Vacuum Chamber Pedestal Heater with Extended Sleeve
BACKGROUND
Heating solution for an ALD Vacuum Chamber Heater testing 6” (152mm) wafers up to 450⁰C. There were obvious space constraints at the customer site requiring an extended sleeve of 25”. The extra-long length enabled the placement of the wafer on the top surface eliminating the need to modify the existing chamber.
SCOPE
The Vacuum Pedestal Heater needed to satisfy the following:
- Temperature 450⁰C
- 25” Long sleeve with 2.75 CF Flange on the bottom
- Body must pass Helium Leak rate of 1 x 10̄¯9 cc/sec He
- 6” overall diameter for 6” (152mm) wafers
- Top surface must have a flatness of ± .005”
- Thermocouple for additional temperature measurement
- 1,000 Watt (± 10%) , 120 Volt
- Material was 304 Stainless Steel
OUTCOME
The Vacuum Pedestal Heater was ramped in atmosphere to 450⁰C in approximately 45 minutes. Due to the 360⁰ weld, there was some deflection on the top surface causing it to be out of tolerance. After the 450⁰C ramp, the Vacuum Pedestal Heater was polished down to below ± .005”. A leak test was performed to spec and cleaned to high purity standards then shipped in clean room bags.
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