Watson, George Patrick

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Now showing 1 - 10 of 11
  • Publication
    Surface Treatment and Adhesion Study
    (2018-10-23) DeLessio, Maegan; Watson, Pat
    In photolithography, it is often the case that the resist has difficulty adhering to a wafer due to its hydrophobic nature. The purpose of this study was to determine the best method for avoiding such adhesion problems. This study describes that four different surface treatments, (1) No bake before resist coating, (2) Bake at 115ºC before priming, (3) SURPASS coating, and (4) HDMS priming, are examined for UV lithography of sub-ten micron-sized lines and pillar arrays, and that HDMS vapor priming is the most effective surface treatment in promoting adhesion.
  • Publication
    Effect of Developer Temperature on Photoresist Contrast in Grayscale Lithography
    (2021-05-12) Farnan, Dale; Watson, George Patrick
    SPR 220-3 photoresist was spin-coated onto a silicon wafer, exposed using a Heidelberg DWL66+ laserwriter at different laser powers, and developed at different temperatures. The effect of developer temperature on photoresist contrast was examined. Results show that increasing developer temperature decreased photoresist contrast and increased required dose.
  • Publication
    Influence of NaOH Concentration on Transfer Process of Graphene
    (2019-09-13) Saldana, Francisco; Wen, Chengyu; Watson, George Patrick
    The process of transferring a monolayer of graphene using two different concentrations of sodium hydroxide (NaOH) solution unto a silicon dioxide (SiO2) coated Si chip using electrochemistry was performed. The transfer process is crucial for the delamination of a continuous graphene monolayer film from copper foil. After examining and inspecting the integrity of the graphene monolayer, it was observed that the lower concentration to NaOH led to slower rate of hydrogen bubble generation; this condition was found to be less destructive and yielded a graphene film with fewer visible tears.
  • Publication
    Fabrication of Organic Thin Film Transistors using Inkjet Printing of PEDOT:PSS
    (2019-11-13) Das, Sourajit; Venkatakrishnan, Akshaya; Yamamoto, Hiromichi; Watson, George Patrick
    An Organic Thin Film Transistors (OTFT) using poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) is fabricated using a Fuji film Dimatix Inkjet printer, and successfully shows the characteristics of field effect transistor as a result of optimization of the inkjet printing condition. The V-I characteristics of the two devices also satisfy the fundamental property of transistors that wider is the channel length, smaller is the drain current. Another significant property is observed that the higher gate voltage induces the higher drain current as it allows larger carrier concentration in the channel region.
  • Publication
    Inkjet Printing of Graphene
    (2020-12-17) Hoang, Lauren; Yamamoto, Hiromichi; Suh, Yeonjoon; Watson, George Patrick
    The optimization of inkjet printing graphene using a Fujifilm Dimatix Inkjet printer, is described in this study. The number of printing passes were varied, and relatively uniform lines were obtained. The printing parameter considerations and optimized printing parameters for graphene are also discussed.
  • Publication
    How to cleave wafers: LatticeGear protocol
    (2021-02-10) Wan, Shenshen; Watson, George Patrick
    We report on the process protocol to cleave wafers using LatticeGear cleaving and scribing tools sets.
  • Publication
    Optimization of Bilayer Lift-Off Process to Enable the Gap Size of 1μm Using LOR 3A and S1813
    (2021-01-29) Suh, Yeonjoon; Watson, George Patrick
    Bilayer lift-off process for 1μm feature size is demonstrated using LOR 3A and S1813 photoresist. The thickness of photoresists was fixed, whereas development time is varied. The process was further investigated by measuring the undercut depth and undercut rate by scanning electron microscopy. An optimized and reproducible recipe is provided.
  • Publication
    Effect of Annealing on the Contact Resistance of Aluminum on a p-type Substrate
    (2019-11-14) Shah, Shrey; Watson, George Patrick
    Aluminum contacts are widely used to form both ohmic and rectifying contacts. The process to form these contacts involves annealing, thus it is important to study the effect of annealing on the electrical properties of the contacts. Here, we present a way to measure the contact resistance of aluminum contacts formed on a p-type silicon substrate. It was found the contact resistivity decreased by an average of 18%. It was thus found that annealing at 400°C in a forming gas environment improves the electrical properties of aluminum contacts.
  • Publication
    Correction of pattern size deviations in the fabrication of photomasks made with a laser direct-writer
    (2019-10-04) Xie, Ningzhi; Watson, George Patrick
    When using Heidelberg DWL66+ laser writer to fabricate the photomask, the pattern feature dimensions may have deviations. These deviations can be caused by the lithography process and the undercut in the metal etch process. The same deviation value of 0.8µm was found to appear in all the patterns independent of the pattern original size and local pattern density. To overcome this universal deviation, a universal bias is suggested to be applied to the original patterns during the data preparation for the lithography process. In order to ensure this pre-exposure bias method can work, both the laser direct-write exposure conditions (laser power, filters, focus parameters) and the metal etch time should be kept consistent.
  • Publication
    Reactive Ion Etching Selectivity of Si/SiO2: Comparing of two fluorocarbon gases CHF3 and CF4
    (2019-03-01) Zhang, Meiyue; Watson, Pat
    Two reactive ion etching (RIE) processes were studied to show the relative etch selectivity between SiO2 and Si using two fluorocarbon gases, CF4 and CHF3. Results show that CHF3 gives better selectivity (16:1) over CF4 (1.2 :1). On the other hand, the etch rate of SiO2 of CF4 is approximately 52.8 nm/min, faster than CHF3 (32.4 nm/min).