Custom Engineering Solution: Custom 300mm Vacuum Puck Heater

Optimizing Thermal Uniformity at 400°C Under Severe Spatial Constraints

Executive Summary

A leading semiconductor fabricator faced critical yield losses due to thermal non-uniformity and severe physical footprint limitations within their vacuum deposition chamber. The legacy incumbent heating assembly was too thick and featured an overly bulky vacuum feedthrough design that interfered with internal mechanics.

Engineering delivered a custom, low-profile 300mm Vacuum Puck Heater utilizing 304 Stainless Steel (304SS) and a novel vacuum side-mounted flange design. 

The solution achieved a +/- 1.5⁰C   thermal uniformity profile at 400°C, maintained high-vacuum integrity at 5 x 10 ̄⁹ and eliminated chamber interference, and increased operational throughput by 14%.

Technical Challenges

• Spatial Limitations: Standard bottom-mount heating assemblies interfered with existing lower-chamber robotic substrate handling mechanisms.
• Incumbent Failure: The competitor's part was physically too thick, and its large vacuum feedthrough footprint blocked critical internal clearances.
• Thermal Target: The process required a continuous, stable operating temperature of 400°C.
• Uniformity Metric: Strict process windows demanded a total thermal variance of less than 3% across the entire 300mm substrate surface.
• Vacuum Integrity: High-vacuum compliance required low-outgassing materials capable of operating continuously at 5 x 10 ̄⁹ without structural deformation.

The Engineering Solution

Technical parameter	Legacy incumbent / competitor limitation	BCE custom engineering solution	Quantified technical & operational benefit
Physical profile / thickness	Assembly too thick; blocked critical internal clearances	Ultra-low profile 300mm puck design	100% clearance of vertical zone beneath the puck; zero robotic interference
Vacuum feedthrough design	Overly bulky footprint; interfered with lower-chamber robotics	Proprietary, ultra-compact side-mounted flange assembly	Single minimized custom side port routing; completely bypasses bottom clearance traps
Thermal uniformity at 400°C	High thermal variance causing critical wafer yield losses	Multi-zone, high-density resistive heating element layout	Achieved +/- 1.5°C thermal uniformity
Vacuum leak integrity	Outgassing and deformation issues under high vacuum	Stress-relieved 304SS body with custom fittings	Maintained stable ultra-high vacuum environment at 5 × 10-9
Operational efficiency	Slow stabilization times and mechanical interference bottlenecks	Optimized thermal ramping and reliable mechanical clearances	14% increase in overall operational throughput

Advanced Material Selection

Engineers selected 304 Stainless Steel (304SS) for the low-profile puck body. This material provides an optimal balance of thermal conductivity, high mechanical strength at 400°C, and excellent corrosion resistance under vacuum conditions. 

Ultra-Compact Vacuum Side-Mounted Flange

To bypass the bottom-chamber clearance restrictions and overcome the competitor's bulky layout, engineering designed a proprietary side-mounted flange assembly. This ultra-compact configuration routed all electrical feedthroughs and internal thermometry horizontally through a single minimized custom side port.

• Footprint Reduction: Cleared 100% of the vertical clearance zone beneath the puck by eliminating excess thickness.
• Vacuum Integrity: Maintained a stable environment at 5 x 10 ̄⁹ using custom vacuum fittings.

HK 300mm Compressed Heater Chuck

 BACKGROUND

To reduce the overall cost for an existing application, BCE developed a 300mm aluminum heater chuck that is un-brazed utilizing the compression of two plates with countersink set screws. The heater surface specs were 0.003” flatness at a 0.005” parallelism. Using a 208-volt power supply at 9.7ohm, start @ 25°C temperature and ramped from 100°C to 465°C in 23 minutes. 

SCOPE

Aluminum Heater Chuck needed to satisfy the following:

• Achieve temperature up to 435°C  @ +/- 2% or better 
• Internal element must be able to withstand temperatures up to 600°C
• Anodized surface for electrical isolation 
• 208 Volt, 9.7 Ohm, 4,460 Watt (+5% / - 10%) 
• Thermocouple bore hole to be placed at the center (variable) 
• 4 point temperature profile on the top surface of the heater 
• Used an infrared sensor for each 4 point locations
• FINISH: Hard coat anodize per MIL-A-8625F, Type 3 Class1 Hard-coat thickness  

OUTCOME

BCE produced a highly effective high 300mm heater with exceptional uniformity better than the proposed 435°C (+/-2%).  After the initial ramp, the heater maintained 435°C (+/- 1%) as per the chart below (Temp profile #5). 

BCE

510-274-1990

https://bcemfg.com

Consistent, Repeatable and Efficient Results from a 300mm Semiconductor Chuck Heater with Mirror Finish

300mm Hot Chuck Heater with Mirror Finish

Semiconductor fabrication involves numerous processes, materials, and specialized equipment. The base semiconductor material from which integrated circuits and microchips are manufactured comes in the form of round, thin crystalline disks referred to as wafers. During semiconductor production, wafer temperature uniformity is one of the most critical factors affecting product quality and consistency.

To increase the speed at which a physical or chemical reaction takes place, heat is applied at various stages of the process. Heat is applied through the use of heated chucks which provide precise thermal uniformity which, as mentioned above, is critical for production.

Click image for larger view.

To summarize, the goal of the heated chuck is to provide a very high level of temperature uniformity across the entire wafer surface so that processing output is highly consistent, repeatable and efficient.

BCE, a manufacturer of custom electric heaters and thermal systems was asked by a customer

to replace a cast aluminum heater plagued with surface finish problems. Poor surface finish equates to poor thermal uniformity and heat transfer. To add insult to injury, the vendor was quoting extremely long lead-times for replacements.

Using their broad experience in semiconductor chuck heater design, BCE knew immediately the best solution would be a vacuum brazed-in 6061 T6 aluminum heater with a 2-3 Ra μin surface.

Specification to be met:

• Temperature uniformity +/- 1%
• 350°C - 450°C Temperature range
• Surface finish of 2-3 Ra μin
• Hard coat Anodize
• 6061 T6 Aluminum
• Be able to heat ceramic top plate
•  20 Meg-ohm isolation at 1000 VDC
• Hi-pot 2E + 1K at 3mA

Results

BCE designed a chuck heater using their own proprietary internal element patterns, notches, and thermocouple holes, as well as adding additional manufacturing processes to provide the 2-3 Ra μin finish. Vacuum integrity for the customer has been greatly increased as well as contact with the ceramic workpiece and temperature uniformity.

For more information, contact BCE by calling 510-274-1990 or through visiting their website at https://bcemfg.com.