Immersion lithographic performance and S610C ... - Nikon Precision

Immersion lithographic performance and 

S610C production integration at AMD 

Rolf Seltmann, Marc Staples, Holger Bald, 

Udo Nothelfer, Harry Levinson

Outline 

• Immersion challenges and prior experience at AMD 

• Overlay 

• Defectivity 

• Nikon S610C in AMD‘s 45 nm manufacturing 

• Overlay performance 

• Focus performance 

• Defectivity 

• The pattern orientation issue 

• Matching performance 

• Product performance 

• Summary/ conclusion 

2 | Nikon LithoVision | 22 January 2009

Introduction 

• The logic 45 nm technology has pitches between 130 nm and 

160 nm. 

• For dry tools, this corresponds to a k 1 between 0.31 and 

0.38. 

• With immersion we could delay the use of double 

patterning and a lot of design rule restrictions. 

• Immersion opens the door to k 1 in the range of 0.40 

and above! 

• But what about defectivity, overlay? 

• Some people questioned whether immersion was mature 

enough to put into production in 2007! 


Immersion challenges: overlay 

Indeed, early immersion tools had noticeable non-linear 

signatures: 

Advanced dry tool 

Early Immersion 

State of the art 

immersion 

4.0 nm, 3σ 9.0 nm, 3σ 4.5 nm, 3σ 


But: even with non-linear chuck-signatures we 

can achieve great overlay results 

• Measure signature difference between scanner for layer 1 and 

scanner for layer 2. 

• Signatures are time dependent: S(t 1 ), S(t 2 ), ...S(t n ). 

• S = set of overlay error vectors. 

• Apply a signature S(t i ) depending on the history of layer 1/ layer.2 

exposure. 

• This scenario can be extended to match to tools with 2 chucks. 

Mixed tool, uncorrected 

Mixed tool, corrected 

Dedicated tool/chuck 

S(ti) 

Single digit 

numbers in 

both cases 


Immersion challenges: defectivity 

Is immersion by definition worse than dry? 

Not necessarily! 

If one has good monitoring in place, and if appropriate changes made, even 

lower defect counts (at smaller defect sizes) are possible ! 

The pareto changes but the overall number is even lower! 


S610C performance 


Overlay Performance of the S610C 

Local fill technology 

promises excellent overlay 

However, < 5 nm overlay numbers required 

more: 

• Interferometer improvements (filter 

algorithm). 

• Improved airflow (more homogeneous). 

• Reduced environmental effects (chamber 

ceiling, relocated temperature sensor, ...). 

Overlay-residuals, contact to gate 

Interferometer, airflow, 

lower environmental 

effects 

7.5nm 

5nm 


Focus performance: early S610 data 

Edge die leveling is always a challenge! 

Nikon did a lot of testing and optimization: 

• Wafer edge autofocus algorithm improvement. 

• Stage control mode, data filtering. 

• Autofocus mapping route optimization 

• + some other small incremental steps 

...with big success! 


Focus performance after improvements 

before 

after 

Please note: different 

scale on the two maps 

3σ = 40 nm 3σ = 24 nm 


Focus performance after improvements 

• A 3σ value of 24 nm is an excellent achievement. 

• Good mean focus stability (

Defectivity: a basic question 

Local Fill Technology shows 

excellent overlay, .... 

but what about water loss? 

? 

An unguarded water film is quite challenging and requires 

a very robust nozzle design. 


The joint way to low level defectivity 

Essential steps toward good defectivity: 

• Use material with a high dynamic receding contact angle 

• Wafer edge / bevel optimization 

• Nozzle optimization is the key! 

• Smooth nozzle surface; prevents sticking of particles 

• Proper cleaning / nozzle flushing execution 

• Strong collaboration between Nikon and the customer! 


The joint way to low level defectivity 

as it was today target 

• At the beginning 

of the joint 

project, 

immersion 

defects were 

dominating. 

• Today, they are 

equal or lower 

than other 

(mostly track 

related) defects 


Pattern orientation and its impact 

193 nm dry 

Nikon 

Immersion 

F 

It‘s a one-time effort to get the logistics 

done. Not nice but not really a big deal! 

Immersion 

Company A • If you also have scanners from Company A 

you can‘t share reticles anymore. 

F 

• Layer dedication requires more complex 

factory management systems. 

• In a transition phase, there are extra costs for masks. 

• Technology start-up, new fabs. 

• In high volume manufacturing, dedication by tool type is more 

manageable. 


Can we use tools from different vendors for the 

same product? The overlay question 

• For manufacturing flexibility it is desirable to run even critical layers 

in a mixed tool scenario. 

• How much overlay performance do we give up if we run in mixed 

mode, ultimately mixed between different vendors? 

Higher order matching (both field and grid) is the key! 

• Grids were matched to fab 

reference better than 7/6 nm. 

• No clear systematics anymore! 

Single shot correction as 

an additional knob not used 

6.8/5.6nm (3σ) 


Production data in the matched scenario 

Field residuals 

Wafer overlay 

Single machine 

S610 – baseline, 

initial matching 

S610-baseline second 

matching iteration 

Wafer overlay map uses different scale than field residual maps 


Matched machine overlay statistics 

• RSS addition of the 

individual terms 

• Field residuals include 

the mask contribution 

• Other contains wafer to 

wafer + correctables 

• If matching is done accurately, the performance ∆ is just 20% (same 

vendor) and 30% (mixed vendor) compared to dedicated machines. 

• Slightly higher number for different vendor is due to different, noncorrectable 

grid and lens fingerprint. 

• Based on great performance, we can run all critical layer 

combinations in mixed mode (except one super-critical layer 

combination). 


OPC Matching of S610C to existing 

45 nm process 

• Even if different reticles have to be used for resource and simplicity 

reasons, it is desirable to use the same OPC-model for different 

vendors tooling. 

• Matching method. 

 

 

 

 

 

 

Expose wafer with same nominal illumination settings on the 

reference tool and the S610; measure 1D and 2D patterns. 

Simulate the response CD. Take different pupil shapes into 

account. 

Calibrate the model using the measurements. 

Determine a set of optimized illumination settings for the S610C. 

Simulate effects of small illumination changes and find optimized 

illumination settings. 

Verify optimized settings. 


OPC matching result example for 45 nm 

metal application 

Initial Space through pitch deviation of 

S610 from reference tool 

S610 Space through pitch deviation from 

reference tool after matching 

2 

6.00 

0 

4.00 

Deviation / nm 

-2 

-4 

-6 

Deviation / nm 

2.00 

0.00 

-2.00 

-8 

-4.00 

-10 

0 100 200 300 400 500 600 700 800 

-6.00 

0 200 400 600 800 

Pitch /nm 

Pitch / nm 

• Changes up to 20% on individual knobs necessary 

• Final result is noise dominated 


Electrical performance of lots processed via S610C 

• We successfully run 45 nm lots on the S610C. 

• Most critical layers: contact and gate (impact on yield, speed). 

• We achieved good yield and great speed. 

leakage 

S610 

speed 

• Other layers with hard requirements on overlay and CD control are 

running on the tool as I speak. 


Conclusion /summary 

• The S610C was introduced into AMD‘s well-established 45 nm technology. 

• In close cooperation between NIKON CORPORATION and AMD, all 

lithographic metrics were improved significantly within the project. 

• We achieved world class focus and overlay data. 

• Defectivity, which required process optimization, was improved to a 

level that justifies the use of the tool in high end production. 

• Cooperation continues to get world class performance as well. 

• We could prove very good matching performance to our FAB-baseline, 

both with respect to overlay and OPC. 

• However, issues related to the pattern orientation must be addressed. 

• We have demonstrated great product performance (yield, speed).

Immersion lithographic performance and S610C ... - Nikon Precision

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