EE 410 / Saraswat Handout #3 - Stanford Nanofabrication Facility

EE410 / Saraswat Handout #3
o Slow pull.
• This deposition takes ~2 hr of furnace time.
• Target is ~50 nm undoped and ~550 nm doped (8% Phosphorus) oxide.
4I. Week #5: Preparation
18. LTO Densification (STEPS 4.320-4.360)
Standard Pre-Diffusion Clean
LTO (Glass) Densification
• Program "WET950" in Tylan. Reflow Time = 30 min.
• Use tylan1 ot tylan2
• Process summary:
o Slow push at 800°C.
o Ramp to 950°C in N2 (30 min).
o Reflow: Steam (30 min). Heavily doped LTO (such as the 8% PSG that we are
using) will become somewhat "plastic" at 950°C in steam. This will tend to
smooth out any rough edges over poly steps and will ultimately improve the shape
of the steps that the aluminum metallization has to cover. The steam is bracketed
by dry oxidations.
o Ramp down in N2 (20 min).
o Slow pull.
• This reflow takes ~1 hr and 30 min of furnace time.
19. PM #5: Contact Holes (STEPS 5.000-5.190)
Contact Lithography:
Contact lithography is often difficult since it is a dark field alignment and is over the LTO which
is rough and shows a “starry sky” in dark field.
• Singe & Prime in the yes
• Spin coat using svgcoat/2 programs 9 (no prime), 7 (1.0 µm of 3612 resist w/2 mm EBR),
and 1 (prebake 90 C for 60").
• Expose on the asml
Job name: EE410R_1
Layer ID: 6
Layer Number: CONTACT
Image ID: CONTACT
Reticle ID: EE410RET3
• Post-exposure bake on svgdev/2 using programs 9 (no develop) and 1 (post-expose
bake@110º C for 60").
• Resist develop on svgdev using programs 3 (develop) and 1 (postbake@110º C for 60")
• Inspect. Check the alignment Verniers and record the alignment offsets. You should be
able to align to within 0.5 µm from the ACTIVE level.
Revised Jan. 11, 2008 Page 26/47