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Top Side Conductor vacuum deposition Aluminum sputter deposit in Argon plasma
CVC 601-sputter deposition tool
A conductor metal is vacuum deposited on to the wafer
Because of cost and equipment, aluminum will be used in stead of silver
Sputtered aluminum
Photolithography• Photolithography is the transfer of patterns,
circuits, device structures, etc. to a substrate or wafer using light and a mask or stencil to stop the light.
• Photolithography was used extensively in the progression of microelectronics.
• Today, because of the sizes involved in current computer microprocessor devices, other methods like direct patterning using electron beams are used.
• Photolithography is still used for dimensions down to about 0.5um. The wavelength of UV light is .35-.45 um.
Top side conductor grid needs to be designed
Pattern is created on a transparency sheet to keep cost low
Once top side conductor grid is finalized, a chrome on glass professional mask can be
made
Typical top side conductor Because of tester limitations (100mA) – cell
size to be 3 cm2 max
UV light sensitive material called photoresist is spin coated on to the conductor side of
the wafer
Wafers are spin coated with Shipley 1813 UV sensitive photoresist
spin coating produces a uniform coating
A vacuum chuck holds the wafer
Spin speed is set here
Light sensitive material is stored in
amber dropper bottles – Use 1813
Transparency is used as a photomask
Cells can be of various sizes but must line up for saw
cutting
The antenna design, arrayed on a transparency sheet, is placed on top of the wafer. This transparency is called a photo mask. Production photo masks would be made on
glass plates with high precision patterns.
Ultraviolet light is projected down on to the photoresist coated wafer
HTG mask aligner and UV light source The UV light source is a mercury vapor lamp at 436nm
wavelength
Exposure time set on timer
Wafer is held by vacuum, mask is placed on top and brought into contact with
wafer
Clear glass plates are
used to make sure the
transparency lays flat to the
wafer
UV light with filter
surrounding it
The wafer is developed, leaving photoresist where no UV light has penetrated the mask
Solitec automatic developer
Vacuum switch
Start switch
Aluminum is etched using chemicals specific to the metal
Aluminum etch
After etching, the top conductor grid pattern, will be left on the wafer
Top side conductor complete
Top conductor
Once the top side conductor grid is complete, the back side
conductor can be deposited
For this fabrication run, aluminum will also be sputtered as the back
side contact
Assignment
Submit your top side conductor grid pattern
one per team