Optical Lithography Resources

Trove of lithography application notes from MicroChemicals covering troubleshooting, procedures, techniques, theory

KNI Photoresists

Photoresists provided by KNI:

• S1805, 1813, 1818: field standard positive, may be used for liftoff and withstands some acid etching. Designed with lower toxicity materials. (Manufacturer Spec Sheet) Shipley 1800 series 0.5-1.9μm range available. 0.5-3.2μm available from manufacturer. Suitable for multiple applications but not niche optimized as latter resists.
• AZ 5214: exposable as positive and image reversal negative. Optimized for liftoff processes with negative sidewall profile. Structure is stable to 130°C after postbake. 1-2μm thickness (Manufacturer Spec Sheet)
• AZ 9245, 9260: Intended for thick positive structures 4-20μm. Lower optical absorption and sensitivity permits tall structures but development is slow. (Product Page)
• AZ nLof 2020, 2035, 2070: Also optimized for liftoff processes but thicker than 5214 at 2-7μm spinnable. Structures can be made stable to 250°C. High chemical stability, e-beam exposable, but more difficult to remove. (Product Page)
• AZ 3330-F: medium resolution resist, high thermal stability, optimized for metal RIE etch or plating process environments. 1.0-5.0µm spinnable (Product Page)
• AZ 4620: improved surface adhesion for etching and plating applications, photosensitivity is broad and low, spinnable to 6 - 20 µm.(Product Page)

SU8 Photoresists are no longer provided by KNI (SU8 Developer IS provided by KNI):

• SU-8 2002, 2025, 2075, 2100, 3025, 3050: epoxy-based negative resist. Optimal for tall high-aspect ratio permanent structures. (Manufacturer Spec Sheet ). Difficult to remove. Spinnable to 1.5-200μm thickness.

Reminder of lamp intensities:

Suss 1 Exposure Settings

• Channel 1 is 365nm wavelength at 15 mW/cm2.
• Channel 2 is 405nm wavelength at 25 mW/cm2.

Suss 2 Exposure Settings

• Channel 1 is 365nm wavelength at 10 mW/cm2.
• Channel 2 is 405nm wavelength at 15 mW/cm2.

Reminder of room conditioning:

• Temperature is specified to 68±1° F in the photolithography and surrounding rooms.
• Humidity is typically 50% in the photolithography room, KNI is specified to 40-70%. Remember that moving resist coated samples to dryer rooms, they will need to rehydrate over some time period.

Positive Photoresist Recipes

See recipe notes for additional information on wafer cleaning and prep, edge bead removal, and spin curves.

Resist	Wafer Prep	Spin	Thickness	Prebake	Exposure	Postbake	Flood	Development	Hardbake	Lamp	Notes
S1813	Dehydrate on hot plate	3000rpm	1.6μm	115°C 1min	8-10s	-	-	MF 319 45-60s	-	Suss1 Ch2	Measured 11/19
	Dehydrate on hot plate	5000rpm	1.1μm	115°C 1min	8-10s	-	-	MF 319 45-60s	-	Suss1 Ch2	Measured 11/19
AZ 5214	Dehydrate on hot plate	3500rpm	1.4μm	100°C 1min	25s	-	-	MF319 60s	-	Suss1 Ch1	Measured 10/19
AZ 9260	Dehydrate on hot plate	3000rpm	8μm	110°C 165s	100s	-	-	MF319 12min	-	Suss2 Ch2	Measured 1/20

Negative Photoresist Recipes

See recipe notes for additional information on wafer cleaning and prep, edge bead removal, and spin curves.

Resist	Wafer Prep	Spin	Thickness	Prebake	Exposure	Postbake	Flood	Development	Hardbake	Lamp	Notes
AZ5214	Dehydrate on hot plate	2000rpm	1.8μm	100°C 1min	12s	110°C 45-60s	40s	MF319 60s	-	Suss1 Ch1	Measured 10/19
	Dehydrate on hot plate	3500rpm	1.4μm	100°C 1min	9s	110°C 45-60s	30s	MF319 60s	-	Suss1 Ch1	Measured 10/19
nLoF 2070	Dehydrate on hot plate	2500rpm	7um	110C 90s	12s	110C 90s	-	AZ 726 2min	-	Suss1 Ch1	Measured 12/19

SU-8 Recipes

SU-8 is available in thicknesses ranging from 500nm to 500microns. Remember to use Laurel Spinner 1 and develop in the Wet Chemistry room on the Solvent Bench.

BYU SU-8 Guide

Resist	Wafer Prep	Spin	Thickness	Prebake	Exposure	Postbake	Development	Hardbake	Lamp	Notes
2002	Dehydrate on hot plate	3000rpm	50μm	65C 3min 95C 9min	X	65C 2min 95C 7min	SU-8 Developer X seconds	Optional	Suss1 Ch1	Measured 10/19
2025	Dehydrate on hot plate	3000rpm	50μm	65C 3min 95C 9min	X	65C 2min 95C 7min	SU-8 Developer X seconds	Optional	Suss1 Ch1	Measured 10/19
2100	Dehydrate on hot plate	3000rpm	50μm	65C 3min 95C 9min	X	65C 2min 95C 7min	SU-8 Developer X seconds	Optional	Suss1 Ch1	Measured 10/19

Other Photoresists

• BYU Comprehensive list of photoresists

• UCSB Photoresist Recipes Page 1

• UCSB Photoresist Recipes Page 2

• BYU Photoresist Recipes

Non-KNI Photoresist Recipes

Resist	Wafer Prep	Spin	Thickness	Prebake	Exposure	Postbake	Flood	Development	Hardbake	Lamp	Notes
SPR 220-7.0	-	-	-	-	-	-	-	-	-	-	Measured 10/19

KNI Developers

These developers can be used on the Develop Bench in the Optical Lithography room or on the BASE Bench in the Wet Chemistry room:

• AZ 726 MIF: 2.38% TMAH-based, pre-diluted (ready-to-use) and slightly further diluted only when the application requires it. Contains surfactants to improve development uniformity, so avoid stirring. MIF identifies the developer as 'Metal Ion Free' as it does not contain potassium as in KOH-based developers, it is based on TMAH, an ammonium salt, which prevents metal contamination of semiconductors. 726 is a recommended developer for almost all AZ resists MicroChemicals Development Application Note

• Microposit MF 319: (Metal-Free) TMAH: 2.45%, Polyalkylene glycol <1%, pH: 13. Paired to Shipley/Microposit 1800 series resists, S1805,S1813,S1818 MSDS

• Microposit CD-26: TMAH <5.0 % , pH 13, Also 1800 series targeted, no additional surfactants.

• AZ 400K: KOH-based. "The recommended dilutions for the AZ® 400 K or AZ® 351 B for most of the processes are developer concentrate : Water = 1: . For very thick resist films, up to a 1:3 ratio can be applied [with lower contrast], with a very fine (sub-µm) structures, a 1:5 or 1:6 ratio can support a high resolution using thin resist films." Ref: MicroChemicals Development Application Note Users can adjust dilution for accuracy and length of time they will tolerate.
  • Critical note on KOH use: "Incompatibilities between MIC and MIF Developers Even small traces of TMAH-based metal ion-free developers such as the AZ® 326 MIF, 726 MIF or 826 MIF) can significantly reduce the development rate of metal ion-containing developers (such as the AZ® 400K or 351B). If both types of developers are used, extremely clean work is to be ensured to prevent mutual contamination even in the ppm range, such as in the dispensing system or developer containers." Ref: MicroChemicals Development Application Note

• Microposit 2401: Legacy developer

SU-8 developer can ONLY be used on the SOLVENT Bench in the Wet Chemistry room:

• SU-8 Developer: (Organic Solvent Solution) 1-Methoxy-2-propanol acetate, >99.5%, Synonym propylene glycol monomethyl ether acetate 2-Methoxy-1-propanol acetate, <0.5%. MSDS Paired to SU8 series resists.

Surfactants

Surfactants were developed and added in the 1980s to photoresist developers to combat photoresists' hydrophobic surfaces which cause "hot spots" of fast development. They reduce the surface tension and improve wetting (giving homogeneous development). The common drawback of their inclusion is foaming and an oily nature which makes them incompatible with some agitated processes. Surfactacts also change development speed since they coat photoresist surfaces and inhibit the dissolution reaction. As such exposure-development times must be adjusted and while contrast is improved, resolution may be lost. See here for more in depth discussion: The Lithography Tutor: Photoresist Development

Addtional Photolithography Resources

• BYU Photolithography Guide

• Lithography Terminology

• Lithography Terminology 2

• Resolution Limits of Photolithography