Upload
others
View
7
Download
0
Embed Size (px)
Citation preview
Optical Emission Analysis ofCF4/CHF3/Ar Plasma Etch of Oxide
Anjali Walia
Irvington High School
8/13/15
1
RIE : Reactive Ion Etch
• Type of dry etching
• Chemically reactive plasmaremoves material deposited on on wafers
• Plasma created by applying strong RF field
• Electrons accumulate on platen -> - DC self Bias
• Plasma sheath has positive charge
• Positive ions drift toward wafer platen and react with surface
2
Centura MxP
• Magnetically enhanced RIE chamber
• Cathode receives RF power
• Rotating magnetic field applied -> more ionized, reactive gas
• Magnetic field decreases DC bias by lowering resistance of plasma
• Channels distribute He across back of wafer -> prevents photoresist reticulation
3
CF4/CHF3/Ar etching
C
F
F
F
F
F
F
H
F
Si substrate
PR PR
SiO2
OO
C
• F reacts with SiO2 -> O2 becomes a part of the etch
• C forms teflon-like polymer that is attacked by O2
• Polymerizes over non-O2 bearing surfaces4
Optical Emission Spectroscopy
• Method of chemicalanalysis
• Intensity of light emittedfrom spark at particularwavelength used to determine relative quantities of elements in plasma
• Wavelength -> identity of element
• Intensity proportional to number of atoms of element
• Used to obtain spectrum of etch process5
Optical Setup
• Ocean Optics spectrometer with range195 – 900 nm
• Ocean Optics software for spectrum
• 2 meter Fiber Patch Cable from Thorlabs with range 200-1200 nm
Centura MXP
Fiber
Spectrophotometer
LaptopUSB
6
Test Structure
• 2 main sets of tests: Oxide Etch and Spacer Etch
• Different wafers run for each set: 10 μ SiO2/Si
1 μ SiO2/Si
PR/Si
Thin PR(DUV 210 - 0.6)/10 μ SiO2/Si
PR(OiR 906 - 12)/1 μ SiO2/Si
• Ran O2 Clean process on a Bare Si wafer before and after each test to clean the chamber
• Each process run for 10 minutes
• Scans every 10 milliseconds 7
Standard Etch Profiles
8
Relevant Wavelength Data
Species Wavelength
O2 (O) 437, 497, 502, 533, 544, 615, 616, 646, 700, 725, 777
N2 337, 326, 331, 390, 391, 428, 576, 580, 655, 662, 671, 688, 727, 790
Ar 451, 485, 550, 603, 697, 707, 750, 416
F 624, 635, 641, 677, 683, 686, 687, 690, 691, 697, 714, 713, 720, 733, 740, 743, 751, 755, 757, 761 776, 780
CO2 288, 290, 337
CO 484
CF4 (CF) 240, 256
SiF4 (SiF) 640, 777
CH4 (CH) 431
C4F8 (CF2) 249, 252, 246, 255, 260, 263, 271, 275, 288, 292, 321
CN 359, 386, 387, 418, 420, 422, 647, 693, 709, 785
NO 237, 245, 256, 268, 272, 286
9
< 350 nm -> overwhelmed by CF / polymerization reactions
Ar peak
10
11
Relevant Wavelength Data
Species Wavelength
O2 (O) 437, 497, 502, 533, 544, 615, 616, 646, 700, 725, 777
CO2 288, 290, 337
CO 484
CF4 (CF) 240, 256
SiF4 (SiF) 640, 777
12
13
14
15
16
Suggested Further Tests
• Rerun spacer etch on PR patterned oxide, test for polymerization after 4 minutes
• Testing of nitride films to see if they cross contaminate between etches, specifically low stress nitride and stoichiometric silicon nitride
17
Thanks for listening!
Special Thanks To…
• Ryan Rivers
• Jayss Marshall
• Jesse
• Cheryl
• Marilyn
• Bill Flounders
18
Works Cited
• Centura MxP manual
• P5000 Endpoint Manual
19
Optical Model
• Created model to correct for loss of intensity through fiber
• Used dataset for optical fiber from Thorlabs to approximate attenuation coefficients for spectrometer output
• Back calculated to find input intensity using the known output intensity and percent transmittance
• No effect on dataset
20
21