Lithography

A laser source pattern generator used for making photomasks.  Resolution limit of 0.6 microns.

Usually 4 inch and 5 inch photomasks are patterned, however, has alignment capability to direct write on silicon wafers.

Photomask Making Process

DWL 66 Write Time Chart

Please use this chart for calculating the approximate write time for making a mask. Use this information to schedule the appropriate amount of time on the online scheduler for the DWL66. You will need to know the field area and which lens (2mm, 4mm, or 10mm) you plan to use.

The cleanroom also has a Quintel Q4000-6 mask aligner object (LC01). This object enables alignment of 2-level masks in addition to standard exposure capability. The resolution of this object 2 microns.

Daily Startup Checks

Karl Suss MA6 BA6 Contact Aligner/Printer: 1000 W broadband UV arc lamp produces 8 – 12 mW/cm2 intensity at the wafer.  Resolution demonstrated to .5 micron spaces between geometries.  Substrate size ranges from 5×5 mm to 150 mm (6 inch).  We have mask/wafer hardware for 3, 4 and 6 in diameter substrates.  System has automatic wedge compensation for both contact and proximity printing.  Alignment gap is programmable from 0 to 300 micron, resolution 1 micron.  Substrates and photomasks are loaded manually.  For extra small substrate alignment, the system uses a reference and scan alternating alignment microscope motion.  Objective lens separation distance is 40 to 140 mm.  Alignment microscope illumination is filtered to prevent resist exposure on substrate.  There are three objective lenses: 5x, 10x, and 20x magnification.  This system also has back side alignment and illumination microscopes.  The system is microprocessor controlled for convenient operator interface.

Daily Startup Checks & Operational Verifications

Lithography imprint system for defining nano-meter features.

An automated system that can clean multiple masks using detergent and high pressure DI water.

A Brewer Scientific system for coating silicon wafers with a controlled thickness of photoresist.

A precision vented hotplate, built into the chassis, allows controlled post baking of the resist.

Spin Theory

The CB-15 Headway spinner has a 15 inch bowl in a vented SS hood.  The spinner is used  to spin coat thin films of photoresist onto silicon wafers and photomasks.

The CPK Acid and Base  processor can spin-spray acids, bases, water, and nitrogen onto substrates in a programmable process with variable spin speeds and chemical spray times.  Several programs are stored to enable chrome etching of photomasks, and development of photoresists.

Daily Startup Checks & Operational Verifications

The CPK Solvent  processor can spin-spray solvents (acetone, Ipa) , water, and nitrogen onto substrates in a programmable process with variable spin speeds and chemical spray times.  Several programs are stored to enable cleaning of substrates or developing of resists.

Daily Startup Checks & Operational Verifications

The Blue M ovens are used for resist process bake steps. Four ovens cover temperatures from 65 to 180 C.

Blue M Oven Enclosure Exhaust Flow

The Cole Parmer digital ovens are used for SU-8 thermal bake processing typically for MEMS processes.

The YES 310 vacuum oven is used to coat substrates with HMDS to enhance resist adhesion to the substrates.

Daily Startup Checks & Operational Verifications

UTD received funding from the National Science Foundation for a high resolution electron beam lithography system as a result of a proposal written by Dr. Walter Hu, Dr. Lawerence Overzet and Dr. J. B. Lee for the purpose of providing researchers in the North Texas area capability for patterning nano-scale devices commensurate with the leading edge of nano-scale research.  The system purchased is the new Raith 150Two EBL system, and it was installed and commissioned in the UTD NSERL Cleanroom in May of 2012. Staff and appropriate graduate students have been trained on the system by Raith training engineers and are currently starting projects using the object. Staff is in the process of characterizing performance and documenting the object procedures and lithography processes.

 Key System Capability Specs:

• Thermal Field Emitter filament with beam size=/<2nm
• Beam current range 5 pA-20 nA
• Beam energy 100 eV – 30 keV
• Stage x,y,z travel range 150 x 150 x 20 mm

• Current density >/=20,000 A/cm (squared)
• Stitching accuracy =/< 40 nm (mean + 3 sigma)
• Overlay accuracy =/< 40 nm (mean + 3 sigma)
• Minimum resolution =< 10 nm
• Configured with 4″ wafer holder
• GDSII pattern creation software is included in object software and also available on line

“Squirm Mark Array” Alignment: Preliminary Test Process

Raith Overlay Alignment: e-Beam over Optical Patterns

Raith Freehand Leads: Patterning for Random Graphene Flakes

Wafer Alignment for Raith e-Beam Writer