Equipment capability is changing
Equipment has position-specific control capabilities, but the recipe does not determine itself
CMP and Etch tools do not apply exactly the same condition across an entire wafer. Control mechanisms such as zones, temperature, and gas are increasingly segmented so center, middle, and edge regions can be corrected separately.
Multi-zone polishing and real-time profile control
CMP tools adjust the within-wafer polishing profile using polishing heads with multiple pressure zones and in-situ metrology. Some production tools can also correct the profile in real time as incoming profiles or polishing rates change.
- Multi-zone polishing head
- Within-wafer uniformity management
- Profile and endpoint control
Expanding control mechanisms for edge, temperature, gas distribution, and more
Etch tools also use mechanisms such as wafer-edge plasma conditions, wafer temperature, and gas distribution to adjust across-wafer uniformity and profile. Implementations differ by equipment, but the direction is clear: increasingly fine correction of position-specific results.
- Wafer-edge plasma / sheath tuning
- Radial wafer temperature tuning
- Multi-zone gas distribution and local correction
When there are only a few variables, engineers can tune conditions through experience and repeated experiments. As zones and actuators multiply, changing one variable can affect several locations at once and interactions among variables become stronger.
Whenever the product or target profile changes, engineers may test several recipes, process wafers, review metrology, and modify the conditions again. This repetition is why sophisticated equipment control features can still be difficult to use directly by hand.
Pressure zones, edge control, temperature, and gas distribution are physical control knobs that change process results.
Starting from the target wafer profile, calculate the required combination of control variables and review the expected result and constraints before production deployment.
R2R control is not limited to wafer-to-wafer variation
R2R control is often described as using the previous wafer or lot result to correct the average value of the next run. But if the equipment has position-specific actuators, the control target can expand from an average to the spatial distribution within the wafer.
Expand the control target
Keep the Run-to-Run control cycle while expanding the managed output from wafer averages to the within-wafer profile.
WIWNU is an important management metric. Depending on the product and downstream process, matching the wafer profile itself to the desired shape can matter more than the WIWNU number alone.
When product conditions or process targets change during production, the optimal wafer profile can change as well. Traditionally, retuning the recipe for a new target can require substantial repeated work.
Once an engineer defines a new target profile, the required process conditions can be calculated and the expected result and constraints reviewed before application. This reduces long cycles of manual tuning whenever the profile changes.
A workflow for using equipment control capabilities in real production
Conventional manual tuning
Define a new profile for the product or process target.
Choose conditions based on engineer experience and DOE.
Test on actual equipment and review the result.
Modify the recipe again if it differs from the target.
Repeat testing and adjustment until the target is reached.
Amfibian
The engineer defines the required wafer profile.
The model calculates control conditions that match the target.
Review expected results and process/equipment constraints.
Apply to the real process according to the customer's approval procedure.
Equipment spatial-control capabilities are already sophisticated. The difficult part is having engineers manually combine many control variables and find the optimal recipe every time.
Amfibian does not replace equipment actuators. It uses existing actuators and process data to calculate the conditions required for the target result, validate them, and then deploy them to production.
This approach is particularly intuitive in processes such as CMP where multi-zone actuators are explicit. The same concept can also be applied to Etch according to the equipment's spatial-control mechanisms, including edge control, wafer temperature, gas distribution, and local processing.
The actual control scope depends on equipment architecture, available actuators, metrology, and process constraints. Amfibian defines the modeling and validation scope around the control variables actually available in each process.
Examples of equipment technologies in public materials
- Applied Materials — Reflexion CMP: multi-zone polishing head and real-time profile control
- Lam Research — Kiyo3x: edge control and profile shaping through radial wafer-temperature tuning
- Lam Research — Flex G Series: CD-uniformity control based on multi-zone gas distribution
- Tokyo Electron — Acrevia: location-specific processing that adjusts etch amount by wafer position