Transcript CLEANROOM PROJECT 3: Evaluating baseline recipes for

Evaluating Baseline Deposition
and Etch Recipes for Silicon
Dioxide and Silicon Nitride
using PECVD and RIE Tools
Presented by
Ayesha K. Denny
NNIN RET GIFT Fellow
Ga Tech MiRC Summer 2007
Research Objectives
1.
2.
3.
Verify process rates of standard recipes on deposition and
etching tools. The tools utilized for deposition were: Unaxis
PECVD, Plasma Therm PECVD (left chamber SiN, right
chamber SiO2), and STS PECVD. Etching tools used were
Plasma Therm RIE (right chamber) and the Vision Oxide
(Advance Vac). Substances deposited and etched were
silicon dioxide and silicon nitride.
Evaluate deposition uniformity of the Plasma Therm
PECVD.
Comparing deposition samples before and after
maintenance on the Unaxis PECVD.
Research Procedure for Verifying
Deposition Rates of Standard SiO2 and SiN
Recipes
1.
10 minute cleaning process of each deposition tool prior to use.
2.
1 minute seasoning of standard recipe on a “miscellaneous wafer” to
create the desired environment in the chamber.
3.
Place wafer in the center of the chamber and run the standard recipe for
SiO2 or SiNx using the appropriate tool.
4.
Measure film thickness of each wafer by completing a 5 point scan using
the Woollam Ellipsometer and then determining the deposition rate and
uniformity using the data obtained.
5.
Spin coat each wafer with HMDS and photoresist 1827 and then bake for
10 minutes at 110°C on a hotplate.
Research Procedure con’t.
6.
Expose the mask pattern to each wafer using the MA6.
7.
Develop each exposed wafer using developer MF319.
8.
Evaluate sufficient development of each wafer by checking its profile
using the P15 profilometer or Alpha Step 500.
Research Procedure for Verifying Etch
Rates of Standard SiO2 and SiN Recipes
1.
10 minute cleaning process of each etching tool prior to use.
2.
1 minute seasoning of standard recipe on a “miscellaneous wafer” to create the
desired environment in the chamber.
3.
Place the wafer in the center of the chamber for the Adv. Vac or the front right
position of the PT RIE (for consistency purposes only), and run the standard
etching recipe for the specified time using the appropriate etching tool.
4.
Obtain a post-etch profile of each wafer using P15 Profilometer or the Alpha Step
500 after stripping the sample of its photoresist using 1165 Remover and use the
data obtained to determine the etch rate for each process.
Research Procedure for Uniformity
Evaluation Using the Plasma Therm
PECVD
1.
10 minute cleaning process of Plasma Therm PECVD prior to use.
2.
Run a 1 minute seasoning deposition on a “miscellaneous wafer” to
create the desired environment in the chamber.
3.
Place wafers in the chamber, making note of each wafer’s position.
4.
Run the standard silicon dioxide deposition recipe for 20 minutes on the
wafers.
5.
Measure film thickness of each wafer by completing a 5 point scan using
the Woollam Ellipsometer and then determining the deposition and
uniformity rate using the data obtained.
Process Recipes
Cleaning Chamber (10 minutes)
Unaxis PECVD
 CLN_250.PRC
STS PECVD
 quickcln.set
PT PECVD
 CLEANR.PRC At 250C
Adv. Vac
 CleanO2
PT RIE
 CLNLOVAC.PRC
Depositions
Unaxis PECVD

STD_OX
Step 1 – Initial  250°C
Step 2 – Gas Stabilization

900mTorr

SiH4 1k 400 sccm

N2O 2k 900 sccm

Power 0 W
Step 3 – SiO2 deposition

900 mTorr

SiH4 1k 400 sccm

N2O 2k 900 sccm

Power 25W
Process Recipes
Deposition
Deposition
STS PECVD

lfsinO2a.set ( standard low
frequency silicon dioxide)
a)
N2O 1420 (actual 1413 – 1427)
b)
2% SiH4/N2 2% SiH4 400 sccm
c)
Process pressure 550 mTorr
d)
APC Angle 0 (actual 67.4)
e)
Process temp. 300°C
f)
Aux. Temp. 250°C (actual 241°C)
g)
Power @ 380 kHz 60W (actual 4953)
h)
Load position 10.0% (actual 24.4%)
i)
Tune position 62.0% (actual 59.8%)
STS PECVD

lfsina.set (standard low frequency
silicon nitride)
a)
NH3 20 sccm
b)
2% SiH4/N2 2% SiH4 2000 sccm
c)
Process pressure 550 mTorr
d)
Process temp. 300°C (actual 298°C)
e)
Aux temp. 250°C (actual 240 °C)
f)
Power @ 380 kHz 60W (actual 5358)
g)
Load position 3% (actual 14.7%)
h)
Tune position 65% (actual 61.2% –
61.4%)
Process Recipes
Deposition
PT PECVD

STDOX.PRC (standard silicon
dioxide right chamber)
250°C
Step 4 – Gas stabilization

700 mTorr

SiH4 400 sccm

N2O 900 sccm

Power 0 W
Step 5 – Deposition

700 mTorr for SiO2 (actual 723-725
mTorr)

900 mTorr for SiN (actual 920-922
mTorr)

Power 25 W (actual range 22-28W)
Deposition
PT PECVD

STDNIT.PRC (standard silicon
nitride left chamber)
250°C
Step 4 – Gas stabilization

900 mTorr

SiH4 200 sccm

N2 900 sccm

NH3 5.00 sccm

Power0 W
Step 5 – Deposition

900 mTorr

SiH4 200 sccm

N2 900 sccm

NH3 5.00 sccm

Power 30 W
Process Recipes
Measuring Film Thickness
Woollam Ellipsometer
 Thin oxide recipe for SiO2 projected
thickness less than 2500 Å.

Thick oxide recipe for SiO2 projected
thickness greater than 2500 Å.

Thin nitride recipe for SiN projected
thickness less than 2500 Å.

Thick nitride recipe for SiN projected
thickness greater than 2500 Å.

4 inch, 5 point scan
Spin coating using CEE 100CB Spinner
HMDS
 3000 rpm
 1000 rpm/s
 15s
Photoresist 1827
 3000 rpm
 1000 rpm/s
 30s
Baking on a hotplate
 110°C
 10 minutes
Process Recipes
Profiling
Exposing and Developing
MA6
 Channel 2
 Exposure time: 30 sec
 Exposure type: Low Vacuum contact
 Wavelength : 405nm
MF319 Developer
 Agitate exposed wafer until mask
pattern is visible and “rainbow color”
on wafer disappears– approx. 45 to
120 seconds.
P15
 Sampling rate at 50Hz
 Applied force of 0.5 mg
Alpha Step 500
 AS5 recipe
Process Recipes
Etching
PT RIE (right chamber)

STDOX.PRC (standard silicon
dioxide)
a)
Step 2 – Gas stabilization

20 mTorr

CHF3 22.5 sccm

O2 2.5 sccm

Power 0 W
b)
Step 3 – Etching

20 mTorr

CHF3 22.5 sccm

O2 2.5 sccm

Power 300W
Etching
PT RIE (right chamber)

STDNIT.PRC (standard silicon
nitride)
a)
Step 2 – Gas stabilization

40 mTorr

CHF3 45.0 sccm

O2 5.0 sccm

Power 0 W
b)
Step 3 – Etching

40 mTorr

CHF3 45.0 sccm

O2 5.0 sccm

Power 200 W
DEPOSITION AND ETCH MAPPING FOR
WAFERS 1 - 12
PT
RIE (right
chamber)
Adv. Vac
RIE
Unaxis
PECVD
STS
PECVD
PT
PECVD
1, 2, 19
5,6
9,10
3,4
7,8
11,12, 15,
16, 17, 18
Wafer Positions on the Platen for
Deposition Uniformity Evaluation of the
Plasma Therm PECVD
Back left
Back right
Front left
Front right
UNIFORMITY AND
DEPOSITION
RATE RESULTS
Uniformity (Measured by the Woollam Ellipsometer)
and Deposition Rates
(Determined by dividing the thickness of the deposition by the time of deposition)
Wafer
Tool
Material and
Time
Deposited
Uniformity
Projected
Deposition
Actual
Deposition
1
Unaxis
SiO2
5 min
45.424%
600 Å/ min
439 Å/ min
2
Unaxis
SiO2
20 min
1.7554%
600 Å/ min
573 Å/ min
3
Unaxis
Before
maintenance
SiN
20 min
1.2248%
100 Å/ min
Unaxis
After
maintenance
SiN
20 min
2.1816%
Unaxis
SiN 40 min
1.7464%
19
4
88 Å/ min
100 Å/ min
93 Å/ min
100 Å/ min
90 Å/ min
Con’t. Uniformity and Deposition Rate
Wafer
Tool
Material and
Time
Deposited
Uniformity
Projected
Deposition
Actual
Deposition
5
STS
SiO2 5 min
3.9952%
720 Å/ min
710 Å/ min
6
STS
SiO2 20 min
1.1929%
720 Å/ min
721 Å/ min
7
STS
SiN 20 min
1.5113%
460 Å/ min
377 Å/ min
8
STS
SiN 40 min
1.4945%
460 Å/ min
473 Å/ min
9
PT
SiO2 5 min
3.1974%
400 Å/ min
517 Å/ min
10
PT
SiO2 20 min
3.4404%
400 Å/ min
527 Å/ min
11
PT
SiN 20 min
1.6205%
100 Å/ min
154 Å/ min
12
PT
SiN 40 min
1.1027%
100 Å/ min
142 Å/ min
Uniformity Results determined by the Woollam
Ellipsometer for the 20 minute Silicon Dioxide
Process – Plasma Therm PECVD
3.0724%
5.4553%
3.6207%
3.6400%
Deposition Rate for the Uniformity 20 minute
Silicon Dioxide Process on the Plasma Therm
PECVD (400 Å/min projected)
458 Å/min
471 Å/min
494 Å/min
486 Å/min
ETCH
RATE
RESULTS
Step Height and Etch Rate Data
Wafer
and
Material
Etched
Etching
Tool and
Time
Step height
measurement
without photoresist
Projected
Etch Rate
Actual
Etch Rate
1
SiO2
PT RIE
5 min
1950 Å
400-500 Å/min
390 Å/min
2
SiO2
PT RIE
5 min
2125 Å
400-500 Å/min
425 Å/min
3
SiN
Adv. Vac
2 min
(SiO2
recipe)
250 Å
???
125 Å/min
Step height and etch rate data using the Alpha Step 500
Wafer
and Material
Etched
Etching
Tool and Time
Step height
measurement
without photoresist
Projected
Etch Rate
Actual
Etch Rate
10
SiO2
PT RIE
5 min
2100 Å
400-500
Å/min
420 Å/min
15 SiO2
back right
PT RIE
5 min
2175 Å
400-500
Å/min
435 Å/min
16 SiO2
front right
PT RIE
5 min
2100 Å
400-500
Å/min
420 Å/min
17 SiO2
front left
PT RIE
5 min
2000 Å
400-500
Å/min
400 Å/min
18 SiO2
back left
PT RIE
5 min
2125 Å
400-500
Å/min
425 Å/min
Step height and etch rate data using the Alpha Step 500
Wafer
and Material
Etched
Etching
Tool and Time
Step height
measurement
without
photoresist
Projected
Etch Rate
4
SiN
Adv. Vac 2 min
(SiO2 recipe)
200 Å
???
5
SiO2
PT RIE
5 min
2000Å
400-500 Å/min
400 Å/min
6
SiO2
PT RIE5 min
400-500 Å/min
360 Å/min
7
SiN
Adv. Vac 5 min
(SiO2 recipe)
425 Å
???
9
SiO2
PT RIE 5 min
3800 Å
400-500 Å/min
Actual
Etch Rate
100 Å/min
1800 Å
85 Å/min
760 Å/min
And thickness variations
Thickness variation describes the percentage
difference of thickness between the lowest and highest
points of the materials deposited on the wafer
Step 1:
Min. thickness/Max thickness = A
Step 2:
A x 100% = B%
Step 3:
100% - B% = % of thickness variation
5 minute Silicon Dioxide
Unaxis PECVD
Oxide Thickness Å
Mean = 2194.4
Min = 1045.0
Max = 2996.5
Std Dev = 996.79
Uniformity = 45.424 %
2671.25
2346
2020.75
1695.5
1370.25
1045
Thickness variation is 65.1%
Highest thickness area
Lowest
thickness
area
20 minute Silicon Dioxide
Unaxis PECVD
Oxide Thick ne s s Å
Mean = 11469
Min = 11191
Max = 11719
Std Dev = 201.33
Uniformity = 1.7554 %
11631
11543
11455
11367
11279
11191
Thickness variation is 4.5%
Lowest
thickness
area
Highest
Thickness
area
20 minute Silicon Nitride before and
after maintenance - Unaxis PECVD
Nitride Thick ne s s Å
Mean = 1762.7
Min = 1733.8
Max = 1787.4
Std Dev = 21.590
Uniformity = 1.2248 %
Thickness variation is 3.0%
Lowest
thickness area
1778.47
1769.53
1760.6
1751.67
1742.73
1733.8
Highest
thickness area
Nitride Thick ne s s Å
Mean = 1850.8
Min = 1794.8
Max = 1896.7
Std Dev = 40.378
Uniformity = 2.1816 %
1879.72
1862.73
1845.75
1828.77
1811.78
1794.8
Before manual cleaning
Thickness variation is 5.4%
Highest thickness area
Lowest
thickness area
After manual cleaning
40 minute Silicon Nitride
Unaxis PECVD
Nitride Thick ne s s Å
Mean = 3601.8
Min = 3533.1
Max = 3687.5
Std Dev = 62.902
Uniformity = 1.7464 %
Thickness variation is 4.2%
Lowest thickness area
3661.77
3636.03
3610.3
3584.57
3558.83
3533.1
Highest thickness area
5 minute Silicon Dioxide
STS PECVD
Oxide Thick ne s s Å
Thickness variation is 9.2%
Mean = 3550.2
Min = 3447.9
Max = 3797.4
Highest thickness area
Std Dev = 141.84
Uniformity = 3.9952 %
3739.15
3680.9
3622.65
3564.4
3506.15
3447.9
Lowest thickness area
20 minute Silicon Dioxide
STS PECVD
Oxide Thick ne s s Å
Thickness variation is 2.9%
Mean = 14420
Min = 14294
Max = 14715
Std Dev = 172.02
Uniformity = 1.1929 %
Highest thickness area
14644.8
14574.7
14504.5
14434.3
14364.2
14294
Lowest thickness area
20 minute Silicon Nitride
STS PECVD
Nitride Thick ne s s Å
Thickness variation is 3.7%
Mean = 7546.3
Min = 7412.6
Max = 7696.3
Std Dev = 114.05
Uniformity = 1.5113 %
Highest thickness area
7649.02
7601.73
7554.45
7507.17
7459.88
7412.6
Lowest thickness area
40 minute Silicon Nitride
STS PECVD
Nitride Thick ne s s Å
Mean = 18935
Min = 18522
Max = 19310
Std Dev = 282.98
Uniformity = 1.4945 %
Thickness variation is 4.9%
Highest thickness area
19178.7
19047.3
18916
18784.7
18653.3
18522
Lowest thickness areas
5 minute Silicon Dioxide
Plasma Therm PECVD
Oxide Thick ne s s Å
Thickness
l
variation is 7.3%
Mean = 2583.4
Min = 2475.4
Max = 2670.4
Std Dev = 82.603
Uniformity = 3.1974 %
2637.9
2605.4
2572.9
2540.4
2507.9
2475.4
Lowest thickness area
Highest thickness area
20 minute Silicon Dioxide
Plasma Therm PECVD
Oxide Thick ne s s Å
Mean = 10535
Min = 10087
Max = 11026
Std Dev = 362.44
Uniformity = 3.4404 %
Thickness variation is 8.5%
Lowest thickness area
10869.5
10713
10556.5
10400
10243.5
10087
Highest thickness area
20 minute Silicon Nitride
Plasma Therm PECVD
Nitride Thick ne s s Å
Thickness variation is 3.8%
Mean = 3080.9
Min = 2993.0
Lowest thickness area
Max = 3110.5
Std Dev = 49.927
Uniformity = 1.6205 %
3090.92
3071.33
3051.75
3032.17
3012.58
2993
Highest thickness area
40 minute Silicon Nitride
Plasma Therm PECVD
Nitride Thick ne s s Å
Mean = 5661.9
Min = 5570.2
Max = 5716.1
Std Dev = 62.432
Uniformity = 1.1027 %
Thickness variation is 2.6%
Lowest thickness area
5691.78
5667.47
5643.15
5618.83
5594.52
5570.2
Highest thickness area
Uniformity Evaluation for a 20 minute Standard
Silicon Dioxide Deposition using the
Plasma Therm PECVD
Oxide Thick ne s s Å
M ean = 9157.2
M i n = 8728.0
M ax = 9459.1
Std Dev = 281.35
Uni form i ty = 3.0724 %
Thickness variation is 7.3%
Lowest thickness
area
9337.25
9215.4
9093.55
8971.7
8849.85
8728
Oxide Thick ne s s Å
M ean = 9428.9
M i n = 8818.3
M ax = 10145
Std Dev = 514.38
Uni form i ty = 5.4553 %
Thickness variation is 13.1%
Lowest thickness area
9923.88
9702.77
9481.65
9260.53
9039.42
8818.3
Highest thickness area
Oxide Thick ne s s Å
M ean = 9871.7
M i n = 9461.7
M ax = 10270
Std Dev = 357.42
Uni form i ty = 3.6207 %
10135.3
10000.6
9865.85
9731.13
9596.42
9461.7
Highest thickness
area
Oxide Thick ne s s Å
Thickness variation is 7.9%
Lowest
thickness
areas
Highest thickness
area
M ean = 9717.2
M i n = 9340.1
M ax = 10233
Std Dev = 353.71
Uni form i ty = 3.6400 %
10084.2
9935.37
9786.55
9637.73
9488.92
9340.1
Thickness variation is 8.7%
Lowest thickness areas
Highest thickness
area
Bar Graph
Representations of
Deposition Rates
Unaxis PECVD Deposition Rates
700
573
600
500
439
Rate of
400
Deposition
(A/min)
300
200
88
100
93
90
0
SiO2 -- 5 min
SiO2 -- 20 min
SiNx (premaintenance) - SiNx (postmaintenance) - SiNx -- 40 min
- 20 min
- 20 min
Materials and Deposition Time
S1
STS PECVD Deposition Rates
900
800
710
721
700
600
Rate of Deposition 500
(A/min)
473
377
400
300
200
100
0
SiO2 -- 5 min
SiO2 -- 20 min
S1
SiNx -- 20 min
SiNx -- 40 min
Materials and Deposition Time
Plasma Therm PECVD Deposition Rates
Rate of
Deposition (A/min)
700
600
500
400
300
200
100
0
517
527
154
142
SiO2 -- 5
SiO2 -SiNx -- 20
min
SiNx -- 40
20 min
min
min
Materials and Deposition Time
S1
Plasma Therm PECVD Uniformity Deposition Rates
Rate of
Deposition
500
490
480
470
460
450
440
486
494
471
458
SiO2
right
back
SiO2 SiO2 left
right front SiO2 left
back
front
Material and Position in
Chamber
S1
Bar Graph Representations of
Etch Rates
Etch Rates of 5 Minute Silicon Dioxide Processes using the
Plasma Therm RIE
Material and Wafer
Number
SiO2 - 17
SiO2 - 15
SiO2 - 9
SiO2 - 5
SiO2 - 1
Rate of Etch
(A/min)
900
760
700
425
425
500
360
435
400
300
100
-100 390 400
420 420
S1
Etch Rates of Silicon Nitride using the
Advance Vac (Vision Oxide)
140
120
Rate of Etching 100
80
(A/min)
60
40
20
0
125
100
85
SiN -- 2
SiN -- 2
SiN -- 5
min
min
min
Material Etched and
Time
S1
Conclusions
o
o
o
o
o
o
o
Silicon nitride deposition rates were more consistent than silicon dioxide depositions
using the Unaxis PECVD.
Silicon dioxide deposition rates were more consistent than silicon nitride depositions
using the STS PECVD.
Deposition rates for silicon dioxide and silicon nitride were more consistent using the
Plasma Therm PECVD.
Depositions rates are higher in the front of the chamber for the Plasma Therm
PECVD.
After maintenance (thorough cleansing) showed a 1% increase in uniformity.
Etch rates for silicon dioxide using the Plasma Therm RIE varied but fell within the
projected range most of the time.
Etch rates using the Advanced Vac were inconclusive due to insufficient data (tool
was down).
Mentors
 Dr.
Nancy Healy
 Janet Cobb-Sullivan
 Cristina Scelsi
 Dr. Kevin Martin
A Special Thank you to…











Cristina Scelsi
Janet Cobb-Sullivan
Nathan Hull
Jaime Zahorian
Keri Ledford
Charlie Suh
Tran-Vinh Nguyen
Gary Spinner
Other helpful cleanroom staff
Dr. Greg Book
Rochelle Hamby and Jaclyn Murray (2007 RETs)