The study on the effect of multi-level exposure technique to fabricate air bearing surface microstructure

Pattern Transfer Characterization after Double-Level Lithography for a Fabrication of the Three-Dimensional Aluminum Titanium Carbide Air Bearing Surface of the Hard Disk Slider

“…To obtain this and other desired T PR values for the etching process, E 1 , E 2 , and E c are optimized using the OPTOLITH simulator with the parameter extraction from our previous works. 28,33,34) In the simulation, a 20-m-thick initial AZ-P4620 PR with the refractive index, r ¼ 1:64 is coated on a 3-in. palette (TIP) AlTiC substrate.…”

“…The 2 Â 2 m hole pattern is transferred to the PR film by using the stepper parameters including the wavelength, ¼ 405 nm, the numerical aperture, NA ¼ 0:16, and the focus distance, F ¼ 7:91 m. The exposure kinetics of a Clariantz AZ-P4620 positive PR can be defined by using the Dill's parameters from the commercial photoresist datasheet, i.e., A ¼ 0:3697 m À1 , B ¼ 0:0243 m À1 , and adjusted C (C adj ) for the double exposure process. 34) In the exposure step, E 1 is varied from 50 to 800 mJ/cm 2 and E 2 are varied from 50 to 500 mJ/cm 2 . This means that the cumulative dose (E c ) for the double exposure is varied from 100 to 1300 mJ/cm 2 .…”

“…Note that, the fully exposure dose or dose-to-clear for the ABS patterning on the 20 m PR film based on our previous works is 800 mJ/cm 2 . 23) The focus distance (F) is varied from À15 to +15 m. The development kinetics can be determined by Mack's model 8,9) with parameters including the dissolution rate, R min ¼ 1:07 Â 10 À3 m/s, R max ¼ 0:2994 m/s, the dissolution selectivity, n ¼ 6:3969, and the threshold inhibitor concentration, M th ¼ 0:1849. The exposed PR is finally spray developed by potassium hydroxide (KOH) at 23 C for 2 min.…”

“…Therefore, the alternative patterning technique called multi-level photolithography is introduced. 23) The technique uses a binary intensity mask (BIM) for a light exposure across an area coated with an uniform photoresist (PR) film by changing the ultraviolet (UV) light intensity or exposure energy after moving the wafer stage to a new position until all positions are completely exposed. Note that all pattern layers of the ABS structure can be produced on a single mask plate called multi-layer reticle (MLR).…”

“…Our previous works employed a lithography simulator, an increasingly popular tool for modeling and predicting lithography processes [24][25][26][27] due to its low cost and time consuming, to study the effect of the double-exposure to the lithographic parameters 28) including photoresist Dill's para-meters [29][30][31][32] and development parameters, the model extraction for double-exposure simulation, 33) and the adjustment of the simulation parameters to obtain an accurate prediction for double-exposure. 34) The key focus of this research is to investigate pattern transfer characteristics from the initial PR film structure, which is formed using a double-exposure process and validated modeled PR parameters determined previously, 28,33,34) to the AlTiC substrate by reactive ion etching (RIE) using fluorocarbon-based plasmas. 35,36)…”