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Temperature Profiles via DAQ

TEL™ Unity IIe SCCM, 200mm - Temperature Profiles using Noah DAQ

 

Process:

Oxide Etch

RF Power:

3.6kW (combined upper & lower electrode)

T Set-point:

20 °C at lower electrode

(*) Chiller:

OEM qualified compressor-based chiller vs. Noah POU system

 

The data acquisition equipment set-up is typical. We have documented the lower electrode cooling loop supply and return fluid temperatures at the request of the customer.

 

We have also captured the TEL ESC (wafer) temperatures and have used this to correlate the Noah DAQ data. The process recipe information follows:

Contact Etch Process Recipe

 

Step Name

Step #

Step Time

RF Lower

RF Upper

Stab

1

14/60

0

0

Breakthrough

2

20

800

1500

Stab

3

8/60

0

0

Main Etch

4

130

1800

1800

Stab

5

6/60

0

0

Over-etch

6

10

100

1000

Stab

7

4/60

0

0

Dechuck

8

17

100

1000

Pump

9

2

0

0

211 Seconds or ~3 minutes

Application & Obstacles

  • the customer experiences significant 1st wafer effect and through-the-lot temperature rise due to RF-induced temperature drifts (8 °C+) in their TEL Unity IIe SCCM chambers with the OEM qualified chiller(s)
  • temperature alarms occur with the OEM qualified chiller at their desired 20 °C set-point, so the customer is currently forced to run the process at 25 °C
  • the customer has considered switching back to 20 °C and adding recipe cool-down time for the OEM qualified chiller, however this would negatively impact chamber/tool throughput
  • the OEM qualified chiller’s front panel (operator interface) continues to display 20 °C throughout processing!

Evaluating the POU Solution

  • Ramp rate comparison (cooling efficiency)
  • Through-the-lot temperature profile comparisons (25 wafer lots)
    • ESC RTD readings downloaded from the tool’s software (screenshots)
    • Noah DAQ – supply & return fluid temperatures monitored with TCs

 

OEM Qualified Chiller

Noah POU Chiller

 

 

Ramp Up - 489% Faster

Noah POU ramp/stable UP:

1.7 mins

OEM chiller ramp/stable UP:

9.0 mins

Ramp Down - 175% Faster

Noah POU ramp/stable DOWN:

3.3 mins

OEM chiller ramp/stable DOWN:

5.7 mins

 

ESC RTD Readings

 

OEM Qualified Chiller

  • chiller has 2.5kW cooling capacity
  • 2 season/dummy wafers were run prior to LOT
  • (1st wafer effect ~4 °C temp. rise during seasons not shown)
  • 2.1 °C rise of initial wafer temperature post-seasoning
  • 1/5 °C rise of final wafer temperatures post seasoning
  • ESC temperature average through-the-lot is > 27 °C +
  • Process temperature set-point is 25 °C
  • OEM qualified chiller reads 20 °C through LOT processing

NOAH POU Chiller

  • POU has only 1.2kW of cooling capacity @ 20 °C
  • NO seasoning dummy wafers were run prior to this Noah lot
  • < 2.0 °C rise of initial wafer temperatures
  • ~ 2.0 °C rise of final wafer temperatures
  • Noah system closer to original target set-point of 20 °C

Though-the-lot Temperature Profile Comparisons

 

The fluid temperature profiles below were captured during a production run. This data shows ~2 °C fluid temperature rise per wafer and includes a overall temperature rise through-the-lot. The customer was NOT surprised to see these temperature excursions, as this problem is something the customer has been enduring since the tool was installed. It is important to reiterate; “The OEM qualified chiller was reporting a ~20 °C through the entire process!! (shown as supply fluid temperature)”

 

OEM Qualified Chiller

 

 

Noah POU chiller

 

 

The fluid temperature profiles above were captured during a production run under “identical conditions” as the previous data-set. Note the improved temperature uniformity. It is important to point out that this data-set was acquired using DEFAULT P.I.D. settings on the Noah controller. Even with FACTORY SETTINGS, the Noah POU system has reduced the overall temperature variance per wafer by more than 50%.

 

 
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Control Systems, Including Dynamic Point-of-Use Chillers
for Semiconductor Wafer Processing Equipment.
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