1. NanoFab Trainer Update Nick Reeder, February 28, 2014

2. Updates to User Interface Added progress bars to show progress during time-consuming operations.

3. Performance Improvement Added code that removes points from displayed polygons if the points are spaced more closely than a pixel’s width; in some cases this greatly reduces the number of polygon vertices, improving performance of subsequent operations. See next slide for comparison of original code to revised code.

4. Performance Improvement Original Code SiO 2 polygons contain 2112 vertices. Revised Code SiO 2 polygons contain 29 vertices.

5. Change to Etch Code Etch code now has a time resolution of one second instead of one-half minute. New code requires considerably more time for etch operations but gives the user greater control and sometimes results in smoother edge profiles after an etch. (See next slide.) Question: Should dialog box for etch let user specify time in seconds only or in combined minutes:seconds?

6. Change to Etch Code Original Resolution (One half-minute ) SiO 2 polygons contain 29 vertices. New Resolution (One second) SiO 2 polygons contain 32 vertices.

7. Change to Materials Database Added Cl 2 plasma as an etchant. Williams’ 1996 paper has little data for Cl 2 plasma, and 2003 paper has none. See next slide for etch rates.

8. Cl2 + He Al + 2% Si SputteredW Ti Sputtered- W SputteredW Si Single crystal500 Poly n+570 Poly undoped320 SiO2 Wet oxide0.8 Dry oxide- LTO undoped anneald 6 Unan. PSG LPCVD23 Ann. PSG LPCVD14 Si3N4 Stoich LPCVD56 Low-stress LPCVD53 OCG820 positive resist300 Olin Hunt 6512 positive resist270 Etch Rates (nm/min) per Williams 1996 Cl2 Ag, Evap or Sputtered0 + warn Al, Evap or Sputtered 10 Au, Evap or Sputtered0 + warn Cr, Evap or Sputtered 0 + warn Cu, Evap or Sputtered0 + warn Ni, Evap or Sputtered0 + warn Pt, Evap or Sputtered0 + warn Ti, Evap, CVD, or Sputtered0 + warn W, CVD or Sputtered10 Ge, Evap or Sputtered0 + warn Si, Wafer or Evap or Sputtered500 Al2O3, Evap or Sputtered 0 + warn SiO2, Thermal Evap or CVD or Sputtered 10 Si3N4, Evap or CVD or Sputtered 55 Ta2O5 0 + warn TiO2 0 + warn SPR 955 285 SU8 2015285 Proposed Simulated Etch Rates (nm/min)

9. Updates to Expose Code Making progress on passing results from Andrew’s Dill exposure code to the trainer. Image below is from 15 second exposure.

10. Questions about Exposing Photoresist How to generate the incident beam profile at resist surface (as in the figure at right from p. 5 of Andrew’s photoresist chapter), given intensity, wavelength, distance of mask from surface, and width of mask opening? chapter What if surface of resist being exposed is uneven? Can Andrew’s code handle this?

11. Another Question about Exposing Photoresist Page 1 of Andrew’s photoresist chapter states that solubility of exposed resist is about four orders of magnitude greater (i.e., about 10,000 times greater) than solubility of unexposed resist. Why on page 5 do we use S 0 = 2 µm/min and S 1 = 0.05 µm/min, an increase of less than two orders of magnitude?chapter

12. Question about Developing Photoresist Page 5 of Andrew’s photoresist chapter states that example uses S 0 = 2 µm/min. How can image on p. 6 show about 1.0 µm removed in a 15-second develop, which equates to a rate of 4 µm/min?chapter

13. Performance of Expose Code Wondering how far can we reduce the following parameters in Andrew’s code without sacrificing accuracy? – Number of columns in 2D grid (xp) = 1001 – Number of rows in 2D grid (zp) = 500 – Number of time points (tp) = 1000 See next slide for test using 501 for xp and 500 for tp.

14. Performance Comparison xp = 1001 zp = 500 tp = 1000 Time to run = 221 seconds xp = 501 zp = 500 tp = 500 Time to run = 42 seconds 10-second exposure, resist thickness  1.5 µm.

15. More Questions about Exposing Photoresist In Andrew’s code, what is the point of including a two-wavelength-thick layer of air above the resist surface? Is it just to leave some blank space in the final images, or does the air layer play a role in the computations? Can Andrew’s model based on Dill parameters handle negative resist as well as positive? Do we want to let user choose UV wavelengths other than 365 nm? If so, where to find Dill values for other wavelengths? Do we want to wash out the interference ripples, as discussed on last page of Andrew’s photoresist chapter?chapter

16. Date Added To-Do Item Who’s Responsible Date Finished 3/16/12Write code to provide top-down view of mask.NR 3/30/12Add Cl 2 as an etchant.NR 2/11/14 3/30/12 Write code to implement polish, given user parameters of grit size & time. NR 3/30/12 Provide algorithm to determine polish rate given material and grit size. JM 4/20/12Incorporate Andrew’s code for photoresist exposure.NR 4/20/12Fix photoresist underhang problem in spin-coat code.NR 5/4/12 Write code to implement stopping powers of layers to determine whether underlying Si is doped during implantation. NR 5/27/12Write code to implement lift-off.NR1/29/14 5/29/12Write code to implement bake of photoresist.NR 5/31/12 Provide realistic limits on the following user-provided parameters: pressure and temperature when performing CVD; dose and ion energy when performing implantation. AS 6/28/12Niu suggests iterating etch code in seconds instead of minutes.NR2/9/14 1/18/13 Provide look-up table data for 1.) CVD deposition rates based on user- supplied pressure & temperature; 2.) evaporation deposition rates based on user-supplied current & voltage; 3.) sputter deposition rates of Au, Ni, Pt, W, Si 3 N 4, Ta 2 O 5, TiO 2, and Si based on user-supplied pressure & power. AS 1/18/13Write code to implement annealing after implantation.NR 1/18/13Write code to implement doping by diffusion.NR

17. Date Added To-Do ItemWho’s Responsible Date Finished 3/1/13 Write code to implement projection lithography as well as contact lithography. NR 4/14/13 Decide whether to accept Nick’s suggested edits (sent on 4/14/13 and 5/8/13) to Andrew’s seventeen tutorial chapters. AS 6/19/13 Surinder suggests automatically filling in dialog-box parameters if user clicks a point in a “View Rate” graph. NR 10/23/13 Jamshid suggests providing link in dialog boxes to display the relevant “View Rate” graph. NR1/21/14 10/30/13 Jamshid’s student Rajput suggests making it easier for user to know which solvents etch which materials. NR1/21/14 11/3/13Fix bug causing photoresist spikes per Jamshid’s student Chico.NR1/6/14 11/3/13Address performance issue per Jamshid’s student Jarrod.NR2/2/14 Write code to track and plot time, cost, quality of user operations.NR Provide algorithm for tracking time, cost, quality of user operations.AS Write code to implement cleaning.NR Write code to implement profilometer.NR Record video clips (in.flv format) of lab operations.AS & JM Write online help text.NR Test the trainer and report problems to Nick.ALL 1/17/14Revise CVD code to distinguish LPCVD and PECVD.NR