DFC™ Design

Dual Frequency Confined™ Technology

Dual Frequency Confined (DFC) technology, employed in Lam's dielectric etch systems, is today's leading technology for critical front— and back—end dielectric etch applications for technology nodes from 180nm to sub—65nm. DFC technology enables Lam's dielectric etch systems to perform critical back—end processes, such as in situ oxide and low k dual damascene etch; critical front—end applications, such as high aspect ratio contact (HARC) and self—aligned contact (SAC) etch; and large open—area applications, such as gate mask open (GMO), spacer, and passivation etch. DFC technology also provides capability for emerging applications such as photoresist etchback for via—first dual damascene integration schemes.

How It Works

Dual Radio Frequency (RF) Source
The dual frequency power source provides enhanced process flexibility and allows for the etching of different materials, such as organic low k and oxide, in one chamber. Process results are impacted by changes in this ratio. As a result, this capability allows the flexibility to optimize processes.

Confined Plasma
Physically confining the plasma to an area directly above the wafer prevents chemical interaction with the chamber walls. The confined plasma can be described like a box within a box (see diagram), where the process chemistries and plasma are physically confined within a small area inside the chamber. The smaller inner—box volume has a uniform, low—residence—time plasma. Confinement eliminates the potential for polymer build up on the walls that may later flake off onto wafers being processed, causing contamination. Another benefit is lower consumption of process gases.

Clean—mode Operation
Confined plasma allows for the cleaning of chamber components after each wafer is etched using Lam's in situ Waferless Autoclean™ (WAC™) technology. The in situ cleans provide a consistent process environment that prevents process drift and ensures repeatable process results wafer to wafer and chamber to chamber (see chart). Lam's DFC and WAC technologies combine to provide clean—mode operation, which allows for multiple process steps to be carried out sequentially in one chamber. In situ processing can reduce the number of steps required for a typical via—first dual damascene scheme at 130nm by 50 percent, which reduces both process complexity and costs. In situ processing also reduces capital costs for an overall cost reduction of 10—20 percent (see diagrams).

View comparing costs of in situ versus integrated processing.



In situ processing advantages
8—20% higher system output2 • Reduced number of wafer transfers
• Integrated flow has ~40secs additional time (stop process, move wafer & restart process) 2Based on dual dam. in—chamber time of 500—200 sec
8% lower cycle time for 4—chamber system • 9% lower for 2 chambers 3Based on 25 wafer batch
>60% more predictable cycle—time • Single chamber failure (on a 4 chamber system) scenario;
      • In situ flow reduces output by 25%
      • Integrated flow reduces output by 50%

Lam 2300 Exelan In Situ
Dual Damascene Process Flow1
1) Via Etch
2) Via Strip
Re—pattern
3) Trench Etch
4) Trench Strip
5) Barrier Removal		   Integrated Dual
Damascene Process Flow1
1) Via Etch
2) Via Strip
Re—pattern
3) Trench Etch
4) Trench Strip
5) Barrier Removal

1BARC open in situ, plug fill etchback not included

In situ processing has 10% lower capital equipment costs

Higher system output with in situ processing

  • Assumptions: 5000w/w, 75% Utilization, FSG, 6 level DD (1SD, 5DD)*
  • In situ: 300sec chamber busy time = 45wph, requires 39 chambers
  • Integrated : 340sec chamber busy time = 41wph, requires 43 chambers

In situ processing has 2.9 Million fewer wafer transfers

  • Fewer added defects and less wafer breakages
    • Assumptions: 5000w/w, FSG, 6 level DD (1SD, 5DD)
    • In situ VS Integrated
      • Integrated has an additional 11 wafer transfers per wafer*
      • 2.86M additional transfers/year
        • 1 breakage/50,000 transfers
          • 57 broken wafers (@ $17K/wafer) = $969K
        • 1 killer defect/500 transfers
          • 5,720 die lost (@ $150/die) = $858K

Low Residence Time
Not only is the DFC chamber kept clean with only small volumes of process gases used — chemistries are eliminated from the chamber quickly with a high—powered turbo—molecular pump.

Key Advantages