MASK ALIGNER INTRODUCTION Provides a means to

MASK ALIGNER: INTRODUCTION • Provides a means to align a pattern on a chip to the pattern on a mask; and then to expose this pattern UV-light Mask: quartz + Cr pattern Photoresist substrate

The aligner Pump, service corridor Lamp power supply

microscope Manometer box Mirror house Microscope Translation-control Lamp house Sample holder Mask holder Alignment stage

Mercury lamp • g - line : 436 nm • h-line: 405 nm • i - line 365 nm S-1800 series are g-line photoresit

Mercury lamp • Life time: 600 h • Nitrogen cooling is very important. • Lamp must be cool before restarting … or you risk damaging the lamp. Therefore wait ~30 minutes after previous use. But it is better to leave the lamp on for several hours than turn off and on and off and on …. • The first exposure after turning on the lamp should be done with no wafer. If the bulb explodes, it will fill the lithography area with toxic mercury vapor. This can cause severe neurological damage. EVACUATE THE LAB FOR AT LEAST 30 MIN. The mask aligner will also be seriously damaged.

Mercury lamp power supply • It can be operated at constant power or constant Intensity • Constant intensity better reproducibility • CI 1 refers to 365 nm • CI 2 refers to 405 nm In constant intensity mode, the controller monitors the lamp intensity measure on the feedback sensor and varies the power supplied to the lamp to keep the intensity selected • We work with CI 2 because is the power meter we have. I= 25 m. W/cm 2

1. Lamp 7. Diffraction reducing lens plates (69 mm) 2. Elipsoidal mirror 8. Turning mirror 3. Cold mirror 9. Front lens 4. Fly’s eyes lens 5. Condenser lens (32 mm) 6. Frame for filters UV-400 optics

WHAT’S NEW? Before NOW Turn on/off the whole machine, and Nitrogen in service corridor No vacuum no possibility of different exposures modes ONLY H 2 and air switches on the aligner controller unit Vacuum is available. Possibility to choose Height adjustment in contact NEVER height adjustment in contact. The Lever separation was The lever separation must be not used Exposures in constant power Exposures in constant mode intensity mode

Air pressure and nitrogen switches ON/OFF ON all the time

Travel limits: X: 3 mm Y: 3 mm : 3 ONLY MOVE THIN ENDS!!!!!

CONTACT ARM CONTACTSEPARATION LEVER

Exposure modes Mode How does it work? Resolution Vacuum Contact (HP) vacuum is drawn between the mask and ~0. 8 µm pitch the wafer prior exposure. RISK OF BREAKING THE MASK Standard (ST) Hard contact mode During exposure, the vacuum holding ~1. 5 µm pitch the substrate to the chuck is switched off and positive nitrogen pressure is used to press the substrate against the mask. RISK OF BREAKING THE MASK Soft Contact mode The substrate is held to the mask just by ~2 µm pitch mechanical pressure of chuck throughout the exposure. The vacuum holding the substrate to the chuck remains on. SAFE Proximity contact Exposures are made with a small gap between the mask and substrate. The gap is determined by the height adjustment. SAFE. It has to be adjusted manually ? ? Depends on separation comments

MICROSCOPE 1. Fiber optic light pipe 2. Single field /splitfield shutter 3. Rotation for focus 4. Objective separation for splitfield operation 5. Iris diaphram 6. Objectives 7. SPLITFIELD= left shutter fully clockwise; right shutter fully anticlockwise Left objective=left shutter half way; right shutter fully anticlockwise Right objective=left shutter fully clockwise; right shutter half way