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 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 MASK ALIGNER: INTRODUCTION
Pump, service corridor Lamp power supply The aligner
Lamp house microscope Microscope Translation-control Mask holder Alignment stage Manometer box Mirror house Sample holder
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
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 CI2 because is the power meter we have.
I= 25mW/cm2
It can be operated at constant power or constant Intensity
Constant intensity better reproducibility
CI1 refers to 365 nm
CI2 refers to 405 nm
Exposures in constant intensity mode
Exposures in constant power mode The lever separation must be used The Lever separation was not used NEVER height adjustment in contact. Height adjustment in contact Vacuum is available. Possibility to choose No vacuum no possibility of different exposures modes ONLY H2 and air switches on the aligner controller unit Turn on/off the whole machine, and Nitrogen in service corridor NOW Before
Air pressure and nitrogen switches ON/OFF ON all the time
ONLY MOVE THE THIN ENDS!!!!! Travel limits:
X: 3mm
Y: 3mm
: 3
CONTACT ARM CONTACT-SEPARATION LEVER
Exposure modes
SAFE. It has to be adjusted manually ?? Depends on separation Exposures are made with a small gap between the mask and substrate. The gap is determined by the height adjustment.
Proximity contact SAFE ~2 µm pitch The substrate is held to the mask just by mechanical pressure of chuck throughout the exposure. The vacuum holding the substrate to the chuck remains on.
Soft Contact mode RISK OF BREAKING THE MASK ~1.5 µm pitch
During exposure, the vacuum holding the substrate to the chuck is switched off and positive nitrogen pressure is used to press the substrate against the mask.
Standard (ST)
Hard contact mode RISK OF BREAKING THE MASK ~0.8 µm pitch
vacuum is drawn between the mask and the wafer prior exposure. Vacuum Contact (HP) comments Resolution How does it work? Mode
Fiber optic light pipe
Single field /splitfield shutter
Rotation for focus
Objective separation for splitfield operation
Iris diaphram
Objectives
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
MICROSCOPE
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