Nishtha Bhatia Washington High School July 31 st, 2014

Transcription

1 Nishtha Bhatia Washington High School July 31 st, 2014

2 MY PROJECTS Programming Photolithography o Incorporate image slider to Nanolab website homepage o MNL s current i-line PR OiR i is discontinued o Greater functionality than previous.gif o Qualify new resist, OiR i-line

3 FRONT-END DEVELOPMENT

4 OBJECTIVES Image slider that runs across homepage of nanolab.berkeley.edu Ease in uploading images Ability to link images to reports/pdfs/web pages Ability to display captions across images

5 IMPLEMENTATION Programmed with JavaScript jquery Created nine different layouts for image slider, each with different features, including: Image re-sizing Transitions Thumbnail display Nested Thumbnails Pause/Forward/Rewind Buttons

6 LAYOUTS CREATED

7 LAYOUTS CREATED

8 FINAL SLIDER - Demo berkeley.edu/

9 FINAL SLIDER - Code

10 OiR i-line PHOTORESIST

11 THE BASICS What is photolithography? Process of transferring geometric shapes on a mask to a thin film of photoresist Photoresist is on the surface of a substrate typically a silicon wafer Used in industry for integrated circuit manufacturing

12 PROJECT PURPOSE MNL s current i-line resist (OiR i) = discontinued To maintain i-line litho, new resist must be qualified > OiR photoresist END GOAL Find optimal conditions to consistently produce standard 1.2, 1.7, 2.1, and 2.8 µm films of resist + resolve at least 0.7 µm lines and spaces

13 EXPERIMENTAL SETUP - Tools Nanospec Prime Oven Svgcoat1 + Svgdev1 Gcaws6 UV bake LEO SEM

14 EXPERIMENTAL SETUP - Wafers We used three wafers of each thickness (1.2, 1.7, 2.1, and 2.8 µm) #1: used to measure photoresist thickness after hard bake No exposure #2: used to measure photoresist thickness after UV bake No exposure #3: uniformly exposed wafer Used for analysis with LEO scanning electron microscope

15 EXPERIMENTAL PROCEDURE 1. Primed wafers using recipe #2 90 C, 11 min, 780 torr 2. Coat bare wafers with svgcoat1 track: modified programs 1, 3, 5, and , 1.7, 2.1 µm -> manual dynamic dispense µm -> manual static dispense 3. Expose one wafer of each thickness on gcaws6 4. Develop all wafers in svgdev1 track (std. prog. 1) 5. Run one set of wafers through svgdev1 again for hard bake, & the other set of wafers were put into UV bake 6. Examine wafers with LEO SEM

16 NEW SPIN COAT PROGRAMS The faster the spin speed, the thinner the coat of photoresist spin coat technique Wafer ID Target Thickness (µm) Svgcoat1 process to modify Spin speed (rpm) (1, 1) (3, 1) (5, 1) (7, 4) 820 Table 1: Expected spin speeds to produce targeted photoresist thicknesses in the experiment

17 Film Thickness (µm) FILM THICKNESS VS. SPIN SPEED Projected Film Thickness vs. Spin Speed Expected Actual Spin Speed (rpm) Table 2: Spin speeds with expected and actual film thickness

18 COATED PR THICKNESSES 1.2, 1.7, 2.1 µm ID Top Left Flat Right Center Aver. Unif. 1.2 A % 1.2 B % 1.7 A % 1.7 B % Measurements taken on nanospec, like so: T L C R F 2.1 A % 2.1 B % Centripetal force makes PR spin radially outward Table 3: Pre-development photoresist thickness measurements (µm)

19 Optimal Focus & Exposure Conditions F & E values chosen after careful analysis of previous focus-exposure matrix experiments Wafer Exposure Focus 1.2 um 1.0 sec um 1.2 sec um 1.8 sec -10 Table 4: Focus & exposure values for 1.2, 1.7, and 2.1 wafers in experiment

20 PR THICKNESS LOST: POST DEV. All wafers = run through svgdev1 track Standard programs: (1, 1) - no hard bake [yet] TL due to selectivity~ 0.1 µm Wafer Top Left Flat Right Center Aver. 2.1 A Table 5: Post-development measurements

21 HARD BAKE + UV BAKE RESULTS Wafer Top Left Flat Right Center Aver Table 6 (left): Post Hard Bake Measurements TL ~ 0.06 µm Wafer Proc. Top Left Flat Right Center Aver. Table 7 (right): Post UV Bake Measurements TL ~ 0.08 µm 1.2 A A S

22 2.8 µm: CONTACT VS PROXIMITY Contact bake left ghost image of rings on wafer Had to change settings to carry out proximity bake rather than contact bake VS Contact Bake Proximity Bake

23 NEW PR COAT CONDITIONS Extreme improvement in accuracy noted when spin speed changed to 820 rpm rather than 500 rpm as previously conducted Wafer Top Left Flat Right Average Unif. 2.8 A % 2.8 B % Table 8: Pre-development measurements without new program (µm) Unoptimized Wafer Top Left Flat Right Center Aver. Unif. 2.8 A % 2.8 B % Table 9: Pre-development measurements with new program (µm) Optimized

24 OPTIMAL FOCUS & EXPOSURE 2.8 Wafer Exposure Focus Table 10 (left): Focus/exposure values for the 2.8 um wafer (µm) Table 11: Post-development measurements for the 2.8 um wafer (µm) Wafer Top Left Flat Right Center Average

25 POST HARD BAKE MEASUREMENTS Wafer Top Left Flat Right Center Aver. 2.8 A Table 12: Post hard bake measurements (µm) **NOTE: The UV bake resulted in excessive damage to the photoresist film; thus, not recommended to UV bake wafers of this thickness

26 LEO SEM IMAGES 1.2 um Minimum Resolved Feature 0.5 µm

27 LEO SEM IMAGES 1.7 um Minimum Resolved Feature 0.5 µm 4 : 1 aspect ratio

28 LEO SEM IMAGES 2.1 um Minimum Resolved Feature 0.6 µm 3.5 : 1 aspect ratio

29 LEO SEM IMAGES 2.8 um Minimum Resolved Feature 0.6 µm 4 : 1 aspect ratio

30 SUMMARY Best Conditions Wafer ID Svgcoat1 Process to be modified Svgdev1 Process Spin Speed (rpm) Target Thickness (µm) Measured Thickness Pre-dev (µm) Measured Thickness Post-dev (µm) Thickness after Hard- Bake Thickne ss after UV Bake Min Res Feat 1 (1,1) (1,1) (3,1) (1,1) (5,1) (1,1) (4,7) (1,1)

31 ACKNOWLEDGEMENTS Thank you Jeff Clarkson for mentoring me throughout my time in the Nanolab, and helping me execute my project every step of the way! Thank you Olek Proskurowski for guiding, mentoring and teaching me so much about web development! Thank you Hussain Alseddiq and Kim Chan for answering all my questions about my projects and helping me throughout them whenever problems arose! Thank you Cheryl Chang for teaching me all about photolithography and how to use so many tools in the lab! Thank you David Lo and Greg Mullins for maintaining much of the equipment used for this work! Thank you Marilyn Kushner and Adrienne Ruff for taking us to SemiCon! Thank you Bill Flounders for this amazing opportunity! Thank you to the entire staff for taking time out of their busy schedules to help me and for being so supportive!

32 MODIFIED PROGRAMS svgcoat1 1.2 ORIGINAL Program P E O A T S A 1 1 SPIN SPIN DSP SPIN SPIN END Modified Program P E O A T S A 1 3 SPIN ORIGINAL Program P E O A T S A 5 1 SPIN SPIN DSP SPIN SPIN END Modified Program P E O A T S A 5 3 SPIN ORIGINAL Program P E O A T S A 3 1 SPIN SPIN DSP SPIN SPIN END Modified Program P E O A T S A 3 3 SPIN Modified Program Coat P E O A T S A 7 1 SPIN SPIN SPIN END Oven P E O A T S A 4 1 STEP STEP STEP COOL END