Standpipe Diagram

Figure 2.1 Standpipe system flow

Laser Type Tool Quantity Lens A/B replaced

counts Lens A/B lifetime ( month ) Pulse energy ( mj )

7600 1 0 18 7.5

6610 12 6 14 8

7610 17 8 4 10

2005 Dec. ~ 2006 Sep. lens A/B replaced statistics

1 2 3

In figure 2.1 you can see the processing flow of the standpipe-filled. Blue box is a standpipe that has a kilogram capacity of 10. Violet object is a pump for supplying 20 kilograms water to the standpipe. The water of the pump source passes through the pipe (while object) that with one hundred percent of the transmission rate, the water will flow over of the standpipe. So, we used regulator with 1/2-proportioned (green object) to control 10 kilograms water could transfer to the standpipe only.

One day, the pipe was blocked to have seventy-five percent of the transmission rate only (figure 2.2).

The regulator must be adjusted to 2/3-proportioned to ensure enough capacity of the standpipe. As the same reason, the regulator must be adjusted to 1/1-proportioned to cover the pipe with fifty percent of the transmission rate (figure 2.3).

In the program, we could found a doubtful point: If the standpipe needs to be filled by 10 kilograms water only, why should we need to support 20 kilograms? And install the regulator especially for filter out unnecessary water?

2.2 Scanner Intensity Loop

Scanner intensity loop is like the standpipe system (figure 2.2). Laser is like the pump that supports the intensity for system, lens A/B is a medium for light that is like the water pipe or filter, the VA is like the regulator to filter out unnecessary light.

Figure 2.2 Standpipe system flow with scanner intensity control loop

17

VA was the adjustable device in the original ASML scanner intensity control system. It blocked and filtered out unnecessary light (figure 2.3). So, the higher laser energy induced the lens A/B contamination and replacement needed the VA adjustment happening with increasing frequency.

Figure 2.3 Scanner intensity control loop

Table 2.2 Laser power W.R.T VA angle or the transmission rate

According to the understanding of the ASML scanner intensity control system, we have a new idea as below.

1. To fix the transmission rate of the VA to the maximum as possible. (figure 2.4 transmission rate of the green object was 1/1-proportioned)

2. Adjust laser energy to match the required of the wafer level intensity, 3. Increase laser energy if the lens A/B had contamination

According record, lens A/B lifetime was 4 months only

In other word, we would use Laser power adjustment to instead of ASML standard VA angle adjustment method.

Figure 2.4 New Scanner intensity control loop

2.3 Laser Energy Control Loop

Laser energy could be controlled by the piezoelectric devices or software. In the case of Laser energy adjustment, we are willing to use software. It had no difficulty in operation and spent less time.

Increase laser energy to follow lens A/B contamination

19

Figure 2.5 Laser energy control loop

Laser had one parameter “Configure 24” that was the gain calibration for the photocell signal from the energy monitor in the WSM. After experiment, then found it had fine linear curve (figure 2.6). Simply operation and linear power curve decided us to use it.

Intensity of the Wafer Level ( ELS-6600 series )

y = -124.34x + 4299.7

37000 41000 45000 49000 53000 57000 61000 65000

Laser C24 mcahine constant Intensity of the Wafer Level(mW/cm2)

Intensity linearity

Intensity of the Wafer Level ( ELS-7600 series )

y = -270.52x + 8997.1

49000 51000 53000 55000 57000 59000 61000 63000 65000

Laser C24 mcahine constant Intensity of the wafer Leel(mW/cm2) Intensity linearity Intensity of the Wafer Level ( ELS-6600 series )

y = -124.34x + 4299.7

37000 41000 45000 49000 53000 57000 61000 65000

Laser C24 mcahine constant Intensity of the Wafer Level(mW/cm2)

Intensity linearity

Intensity of the Wafer Level ( ELS-7600 series )

y = -270.52x + 8997.1

49000 51000 53000 55000 57000 59000 61000 63000 65000

Laser C24 mcahine constant Intensity of the wafer Leel(mW/cm2) Intensity linearity

Figure 2.6 Intensity curve

From performance index, the new method could lower LASER working voltage but other performance index like E95 of laser pulse bandwidth was kept with original data (figure 2.7) which is major concern by the CD variation of the proximity effect. Secondly the laser pulse energy was kept

the same and stable (figure 2.8). The laser pulse energy is still concern by the CD variation which was impacted the CD mean value effect. The result is which we had anticipated. Lower LASER working voltage will extend LASER chamber, WSM and LNP lifetime.

Figure 2.7 Laser E95 Comparable Data

Figure 2.8 Laser Performance Check

21

Chapter 3 Result/Discussion (Experiment, Result, Analysis…)

3.1 Lens A/B have double lifetime.

We used old type Lens A/B and new methodology at APD8E3 from Nov. 2006, then it got great improvement, kept wafer level intensity stable more than 8 months and low intensity decay rate (<15 mW/cm2 / month) till now. Besides, we tried to assess the effects of the long-life Lens A/B that was new design from ASML at APD8E5. The performance shows new method with old lens A/B is better than old methodology with long life lens A/B, kept stable 5 months and have monthly 334 mW/cm2 intensity decay rate. (Old type: 66,000 NT/set; New type: 102,400 NT/set)

Figure 3.1 Tool A and Tool B wafer level intensity trend chart

Tool A

APD8E5 Wafer Level Intensity Trend Chart

0

Sep-05 Oct-05 Nov-05 Dec-05 Jan-06 Feb-06 Mar-06 Apr-06 May-06 Jun-06 Jul-06 Aug-06 Sep-06 Oct-06 Nov-06 Dec-06 Jan-07 Feb-07 Mar-07 Apr-07 May-07 Jun-07 Jul-07

Date

According to long lifetime Lens A/B’s profitability was better than old type. We will be glad to combine long lifetime Lens A/B with new intensity control methodology in the future. It’s effects was assessing. Currently, our Lens A/B lifetime had extended form 4 months to more than 8 months and it will help us to reduce 1,683,000 NT/year [17 X (12/4 – 12/8) X 66,000 NT/set].

3.2 Laser Chamber have double lifetime.

Lower LASER working voltage will extend chamber lifetime from 19 billion (≒ 16 months) to 39 billion(≒ 32 months), and it will help us to reduce 20,429,516 NT/year [17 X (12/16 – 12/32) X 3,204,630 NT/year].

Figure 3.2 APD8E3 Lifetime extend estimate by LASER working voltage

3.3 Methodology change compare with production yield.

-No yield impact

23

TMR309 CP Yield

75 80 85 90 95 100

W640 W641 W642 W643 W644 W645 W646 W647 W648 W649 W650 W651 W652 W653 W701 W702 W703 W704 W705 W706 W707 W708 W709

Date

Percentage (%)

Totall Tool APD8E3

Figure 3.3 Production yield compared

Chapter 4 Conclusion With the Model of Car Speed

We could easy to fit the research of the simple model for car speed control. In general, ASML request laser vender to provide the fully laser pulse energy to fulfill the scanner need to achieve the maximum WPH, but scanner side need to control the maxmum intensity to prevent the post optics damaged by the high intensity, so it design the VA (variable attenuator) to lower down the intensity to specific value. But it waste the intensity due to VA is a attenuator to decreased the intensity and waste around 30% intensity when all optics is new.

It like the car speed control. We fully use the engine to fulfill value to gain the maximum speed but due to we need to control the maximum speed to achieve the speed control is within the rule. So we add the brake to lower down the speed, but we waste the brake effect and the engine efficiency (figure 4.1)

25

In the new model of the car speed control, we could control the engine by control the engine driving value to control the car speed and do not need to add the brake to lower down the speed. This is dynamic control the car speed by efficiency control to achieve accuracy value, which is a new concept to control car speed. It is like the new methodology to control the laser pulse energy to make it more efficiency and could lower down to the require value to achieve exposure energy and it could improve the Lens A/B life time and Laser chamber lifetime. (Fig 4.2)

Figure 4.2 New Concept of the Car Speed Control

2

Chapter 5 Conclusion

(Root Cause, Improvement, Prevention

According to experiment’s result, we make sure the root cause of the wafer level intensity decay issue is due to higher energy laser. And we find the new intensity control method is effective in extending lens A/B & laser chamber lifetime. The new intensity control method flow as below:

Figure 5.1 The New Intensity Control Method Flow

This methodology could save a lot of cost and also pass ECIP change management for cross FAB experiment sharing.

27

Vita

Study of DUV 248 Lens A/B and Laser Chamber Lifetime Extend by Efficient

Power Cure Control

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