Industrial Example: ANOVA

17 Pages·2003·0.28 MB·English

Industrial Example: ANOVA
•Semiconductor Processing example: Photolithography
Registration Improvements:
•PROBLEM to SOLVE: We are getting a 20% rework rate and
10% of contact layer wafers are getting rejected for failure to align.
We have an idea that we can improve this layer’s alignment signal strength by
changing the photoresist thickness. The alignment syestem siganl strength is
based on thin films reflectivity.
DATA and background:
* Prolith simulations
* Reflectivity at 632nm
* CD swing curves for various oxide thickness
* Actual data and Statistical analysis
1/3/03 ANOVA/Industrial 1
Example_5_ANOVA
Industrial Example: ANOVA Data and background
ALIGNMENT SIGNAL STRENGTH: CT-P1 alignment How the AMSL align
632 nm illumination system “sees” the ASML marker PROLITH Modeling
Reflectivity. Film thickness varaiations
CT Oxide thickness over marker at CT TiSi2 SiCr Overcoat TOTAL
5400
TiSi2 lo SiCr lo 4050 1350
5700
TiSi2 lo SiCr high 4050 1650
5850
TiSi2 target SiCr lo 4500 1350
6150
TiSi2 target SiCr high 4500 1650
TiSi2 target SiCr Target 6000
4500 1500
5550
TiSi2 lo SiCr Target 4050 1500
6450
TiSi2 high SiCr Target 4950 1500
6300
TiSi2 high SiCr lo 4950 1350
6600
TiSi2 high SiCr high 4950 1650
PHOTORESIST Low Target High
Photo resist IX405 0 ASML marker depth 1140 1170 1200
Photo resist IX405 1200 ASML marker depth 1260 1290 1320
1/3/03 ANOVA/Industrial 2
Example_5_ANOVA
Industrial Example: ANOVA Data and background
ALIGNMENT SIGNAL STRENGTH: CT-P1 alignment How the AMSL align
632 nm illumination system “sees” the ASML aligmnent marker PROLITH
Modeling Reflectivity ASML marker zero depth.
CT ASML Alignment Signal Analysis
0.35
CT target Photoresist Thickness 1170nm
CT target Photoresist Thickness 1140nm
m CT target Photoresist Thickness 1200nm
0.3 CT no Photoresist
n

2
3
6
t 0.25
a

y
t
i
v
0.2
i
t
c
e
l
f
e 0.15
R

t
s
i
s
e 0.1
r
o
t
o
h 0.05
P
0
500 520 540 560 580 600 620 640 660 680 700 720 740
CT Total Oxide film Thickness nm
1/3/03 ANOVA/Industrial 3
Example_5_ANOVA
Industrial Example: ANOVA Data and background
ALIGNMENT SIGNAL STRENGTH: CT-P1 alignment How the AMSL align 632 nm
illumination system “sees” the ASML marker PROLITH Modeling Reflectivity delta top of
marker to bottom of marker 1200A depth. Desire maximum delta = thinner photoresist!
CT ASML Alignment Signal Analysis
Photoresist 11400A delta Reflectivity
Photoresist 11700A delta Reflectivity
Photoresist 12000A delta Reflectivity
0.2
er 0.15
k
r
a
m
L 0.1
M
m
A
n
elta 632 0.05
y dat
vitm 0
ectiotto 500 520 540 560 580 600 620 640 660 680 700 720 740
flb -0.05
Rep-
t o
st
si -0.1
e
r
o
t
o -0.15
h
P oxide over P2 thickness range
-0.2
CT Total Oxide film Thickness nm
1/3/03 ANOVA/Industrial 4
Example_5_ANOVA
Industrial Example: ANOVA Data and background
ALIGNMENT SIGNAL STRENGTH: CT-P1 alignment How the AMSL align
632 nm illumination system “sees” the ASML marker PROLITH Modeling
Reflectivity ASML marker 0 and 1200A depths Minimum photoresist thickness
CT ASML Alignment Signal Analysis
0.2
CT target Photoresist Thickness 1140nm
0.18
CT target Photoresist Thickness 1260nm (min PR thickness marker depth
m
n 0.16
2
3
6 0.14
t
a
y
t 0.12
vi
ti
ec 0.1
fl
e
R 0.08
t
s
si
e 0.06
r
o
t
o 0.04
h
P
0.02
0
500 520 540 560 580 600 620 640 660 680 700 720 740
CT Total Oxide film Thickness nm
1/3/03 ANOVA/Industrial 5
Example_5_ANOVA
Industrial Example: ANOVA Data and background
ALIGNMENT SIGNAL STRENGTH: CT-P1 alignment How the AMSL align
632 nm illumination system “sees” the ASML marker PROLITH Modeling
Reflectivity ASML marker 0 and 1200A depths Target photoresist thickness
CT ASML Alignment Signal Analysis
0.2
CT target Photoresist Thickness 1170nm
0.18
CT target Photoresist Thickness 1290nm (target PR thickness marker depth
m
n 0.16
2
3
6 0.14
t
a
y
t 0.12
vi
ti
c
e 0.1
fl
e
R 0.08
t
s
si
e 0.06
r
o
t
o 0.04
h
P
0.02
0
500 520 540 560 580 600 620 640 660 680 700 720 740
CT Total Oxide film Thickness nm
1/3/03 ANOVA/Industrial 6
Example_5_ANOVA
Industrial Example: ANOVA Data and background
ALIGNMENT SIGNAL STRENGTH: CT-P1 alignment How the AMSL align
632 nm illumination system “sees” the ASML marker PROLITH Modeling
Reflectivity ASML marker 0 and 1200A depths maximum photoresist thickness
CT ASML Alignment Signal Analysis
0.2
CT target Photoresist Thickness 1200nm
0.18
CT target Photoresist Thickness 1320nm (Max PR thickness marker depth
m
n 0.16
2
3
6 0.14
t
a
y
t 0.12
vi
ti
ec 0.1
fl
e
R 0.08
t
s
si
e 0.06
r
o
t
o 0.04
h
P
0.02
0
500 520 540 560 580 600 620 640 660 680 700 720 740
CT Total Oxide film Thickness nm
1/3/03 ANOVA/Industrial 7
Example_5_ANOVA
Industrial Example: ANOVA Data and background
ALIGNMENT SIGNAL STRENGTH: CT-P1 alignment signal improves with
thinner or thicker photoresist film. We’d prefer to go thicker: 12300A but for
nominal oxide thickness the swing curve is not optimal ( desire a CD minimum
thickness): hence we need to run an actual swing curve for all three contact types:
CT over DI, P1, and P2/P1.
Prolith: CT layer Swing: Contact CD Various oxide
Thicknesses
880
5490A oxide
860
6090A oxide
840 6690A oxide
820 6230A oxide
m
800
n
780
D
C 760
t 740
c
a 720
t
n 700
o
680
C
660
640
620
600
1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280
IX405 Thickness nm
1/3/03 ANOVA/Industrial 8
Example_5_ANOVA
Industrial Example: ANOVA Actual data
•Experimental data Photoresist impact on alignment and registration
•Run experiment: look at the effect of five different photoresist thicknesses on align
ment varaibles:
•Independent variables or factors: Photoresist thickness: Levels = 5
•Response variables: Alignment signal strength %; X axis registration error amd Y axis
error
CT-P1 ASML Alignment Signal Strength ASML 13 Vs CT Photoresist
Thickness WC19Y Lot 069
% 24
er 22 M%
k Poly. (M%)
r 20
a
m
L 18 y = 3E-05x2 - 0.7993x + 4663.1
A 16 R2 = 0.8971
h
gt 14
n 12
e
r
St 10
al 8
n
g 6
Si
L 4
M 2
S
A 0
11000 11200 11400 11600 11800 12000 12200 12400
IX405 Photoresist Thickness A
1/3/03 ANOVA/Industrial 9
Example_5_ANOVA
Industrial Example: ANOVA Actual data
•Experimental data Photoresist impact on alignment and registration
• Maximum registration error
CT-P1 Registration Error Vs CT Photoresist
Thickness WC19Y Lot 069
0.210
0.190
m
u Max |Error|
r 0.170
o
r Poly. (Max |Error|)
er 0.150
g
e 0.130
R
x
a 0.110
m
1 0.090 y = -1E-07x2 + 0.0027x - 15.756
P
T- R2 = 0.4768
C 0.070
0.050
11000 11200 11400 11600 11800 12000 12200 12400
IX405 Photoresist Thickness A
1/3/03 ANOVA/Industrial 10
Example_5_ANOVA