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Optical Correlation Techniques for Alignmentin Future Pattern Generators
KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
2013 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [sv]

Tillverkningen av fler-lagers mönsterkort kräver en precis upplinjering mellan olika lager för att undvika overlayfel i den fotolitografiska processen. Allteftersom kraven på minskade dimensioner för strukturernaständigt ökar samtidigt med högre krav på produktionstakt, innebärdetta att stora krav ställs på linjeringssystemet. Detta examensarbetepresenterar en analys av ett tänkt system för realtids-linjering, medfokus på framtida applikationer inom direktritning (LDI). Med startpunkti valet av mönster för linjerings-algoritmen diskuteras den signalbehandlingsom skulle behövas tillsammans med de relevanta parametrarnai termer av signal-brusförhållande och kontrast, uppmätta i ettverkligt scenario. Simuleringar som utförts av de föreslagna algoritmerna, applicerade på verkliga signaler, visar på att det är möjligtatt använda optiska korrelations-tekniker för positionering och linjeringi realtid. Det är också påvisat att det mönster som för närvarandeanvänds i LDI är icke-optimalt och att ett föreslaget bättre mönsterökar signal-bakgrundsförhållandet med 20% i scenariot med realtidslinjering.

Nyckelord: Mönstergenerator, fotolitografi, direktritning, mönsterregistrering,realtidslinjering, optisk korrelation, reflexsignal, kontrast, signal-brusförhållande, reflektans, Barker.

Abstract [en]

The production of multi-layer PCBs requires accurate alignment systemsin order to reduce the overlay errors in the photolithographyprocess. With the requirements for minimum feature size ever decreasing and the ones for machine throughput ever increasing, a huge burden is placed on the alignment system. The task to design analignment system that is both accurate and fast is clearly non-trivial. This Master Thesis presents the analysis and operational principle of areal-time alignment system, with focus on future applications of laserdirect imaging (LDI). Starting from the choice of the pattern to be usedin the alignment algorithm, continuing with the corresponding signal processing and further estimating the relevant signal parameters from real-case scenarios, the simulations of the suggested alignment methods show on the feasibility of using direct optical correlation techniques forread-out of the positions of structures of resist directly on copper. The currently used patterns are also shown to be non-optimal, with better correlation patterns presented that yield an improvement of 20% in the signal-to-background ratio and that show enhanced robustness to noise in a real-time alignment scenario.

Keywords: Pattern generators, photolithography, laser direct imaging, overlay, pattern registration, real-time alignment, optical correlation, reflex signal, contrast, signal-to-noise ratio, reflectivity, Barker.

Place, publisher, year, edition, pages
2013. , 83 p.
Series
Degree Project in Production Engineering Management, Second Level, 547
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-127830OAI: oai:DiVA.org:kth-127830DiVA: diva2:646334
Examiners
Available from: 2013-09-09 Created: 2013-09-09 Last updated: 2013-09-09Bibliographically approved

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