evaluating baseline deposition and etch recipes for silicon dioxide and silicon nitride using pecvd...

Evaluating Baseline Deposition and Etch

Recipes for Silicon Dioxide and Silicon Nitride using

PECVD and RIE Tools

Presented byAyesha K. Denny

NNIN RET GIFT FellowGa Tech MiRC Summer 2007

Research Objectives1. 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.

2. Evaluate deposition uniformity of the Plasma Therm PECVD.

3. 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

PECVD1. 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_OXStep 1 – Initial 250°CStep 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

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 49-53)

h) Load position 10.0% (actual 24.4%)

i) Tune position 62.0% (actual 59.8%)

Deposition

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 53-58)

g) Load position 3% (actual 14.7%)

h) Tune position 65% (actual 61.2% – 61.4%)

Process Recipes

DepositionPT PECVD STDOX.PRC (standard silicon

dioxide right chamber)250°C250°CStep 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)

DepositionPT PECVD STDNIT.PRC (standard silicon

nitride left chamber)250°C250°CStep 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 RecipesMeasuring 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 RecipesExposing 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.

ProfilingP15 Sampling rate at 50Hz Applied force of 0.5 mg

Alpha Step 500 AS5 recipe

Process RecipesEtching

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


b) Step 3 – Etching 40 mTorr CHF3 45.0 sccm


DEPOSITION AND ETCH MAPPING FOR WAFERS 1 - 12

Unaxis

PECVD

STS

PECVD

PT

PECVD

PT

RIE (right chamber)

1, 2, 19 5,6 9,10

Adv. Vac

RIE

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 right

Front rightFront left

Back left

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

88 Å/ min

19 Unaxis

After maintenance

SiN

20 min

2.1816% 100 Å/ min

93 Å/ min

4 Unaxis SiN 40 min 1.7464% 100 Å/ min 90 Å/ min

Con’t. Uniformity and Deposition Rate

Wafer Tool

Material and Time

DepositedUniformity

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)

471 Å/min

486 Å/min 494 Å/min

458 Å/min

ETCHRATE RESULTS

Step Height and Etch Rate DataWafer

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 500Wafer

and Material Etched

Etching

Tool and Time


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


without photoresist

Projected

Etch Rate

Actual

Etch Rate

4

SiN

Adv. Vac 2 min (SiO2 recipe) 200 Å ???

100 Å/min

5

SiO2

PT RIE

5 min 2000Å

400-500 Å/min 400 Å/min

6

SiO2

PT RIE5 min

1800 Å 400-500 Å/min 360 Å/min

7

SiN

Adv. Vac 5 min (SiO2 recipe) 425 Å

???

85 Å/min

9

SiO2

PT RIE 5 min 3800 Å 400-500 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

1045

1370.25

1695.5

2020.75

2346

2671.25

Mean = 2194.4Min = 1045.0Max = 2996.5Std Dev = 996.79Uniformity = 45.424 %

Oxide Thickness ÅThickness variation is 65.1%

Lowest thickness area

Highest thickness area

20 minute Silicon Dioxide Unaxis PECVD

11191

11279

11367

11455

11543

11631

Mean = 11469Min = 11191Max = 11719Std Dev = 201.33Uniformity = 1.7554 %



Highest Thickness area

20 minute Silicon Nitride before and after maintenance - Unaxis PECVD

1733.8

1742.73

1751.67

1760.6

1769.53

1778.47


Nitride Thickness Å

1794.8

1811.78

1828.77

1845.75

1862.73

1879.72


Nitride Thickness Å

Before manual cleaning After manual cleaning

Thickness variation is 3.0% Thickness variation is 5.4%


Highest thickness area Highest thickness area

Lowestthickness area

40 minute Silicon Nitride Unaxis PECVD

3533.1

3558.83

3584.57

3610.3

3636.03

3661.77


Nitride Thickness Å Thickness variation is 4.2%



5 minute Silicon DioxideSTS PECVD

3447.9

3506.15

3564.4

3622.65

3680.9

3739.15



Lowest thickness areaHighest thickness area

20 minute Silicon Dioxide STS PECVD

14294

14364.2

14434.3

14504.5

14574.7

14644.8


Oxide Thickness Å Thickness variation is 2.9%



20 minute Silicon NitrideSTS PECVD

7412.6

7459.88

7507.17

7554.45

7601.73

7649.02





40 minute Silicon NitrideSTS PECVD

18522

18653.3

18784.7

18916

19047.3

19178.7



Lowest thickness areas


5 minute Silicon DioxidePlasma Therm PECVD

2475.4

2507.9

2540.4

2572.9

2605.4

2637.9


Oxide Thickness ÅlThickness variation is 7.3%



20 minute Silicon DioxidePlasma Therm PECVD

10087

10243.5

10400

10556.5

10713

10869.5





20 minute Silicon NitridePlasma Therm PECVD

2993

3012.58

3032.17

3051.75

3071.33

3090.92



Highest thickness areaLowest thickness area

40 minute Silicon NitridePlasma Therm PECVD

5570.2

5594.52

5618.83

5643.15

5667.47

5691.78


Nitride Thickness ÅThickness variation is 2.6%



Uniformity Evaluation for a 20 minute Standard Silicon Dioxide Deposition using the

Plasma Therm PECVD

8818.3

9039.42

9260.53

9481.65

9702.77

9923.88

Mean = 9428.9Min = 8818.3Max = 10145Std Dev = 514.38Uniformity = 5.4553 %

Oxide Thickness Å

9340.1

9488.92

9637.73

9786.55

9935.37

10084.2


Oxide Thickness Å

9461.7

9596.42

9731.13

9865.85

10000.6

10135.3


Oxide Thickness Å

8728

8849.85

8971.7

9093.55

9215.4

9337.25


Oxide Thickness Å

Thickness variation is 7.3% Thickness variation is 13.1%

Thickness variation is 8.7%Thickness variation is 7.9%


Highest thickness area Highest thicknessarea


Lowest thicknessareas

Highest thicknessarea

Lowest thickness areas


Bar Graph Representations of Deposition Rates

SiO2 -- 5 minSiO2 -- 20 min

SiNx (pre-maintenance) -

- 20 min

SiNx (post-maintenance) -

- 20 min

SiNx -- 40 min

S1

439

573

88 93 90

0

100

200

300

400

500

600

700

Rate of Deposition

(A/min)

Materials and Deposition Time

Unaxis PECVD Deposition Rates

SiO2 -- 5 minSiO2 -- 20 min

SiNx -- 20 minSiNx -- 40 min

S1

710 721

377 473

0

100

200

300

400

500

600

700

800

900


Rate of Deposition (A/min)

STS PECVD Deposition Rates

SiO2 -- 5min

SiO2 --20 min

SiNx -- 20min

SiNx -- 40min

S1

517 527

154 142

0100200300400500600700


Rate of Deposition (A/min)

Plasma Therm PECVD Deposition Rates

SiO2rightback

SiO2rightfront

SiO2 leftfront

SiO2 leftback

S1

471486

494

458

440450460470480490500

Material and Position in Chamber

Rate of Deposition

Plasma Therm PECVD Uniformity Deposition Rates

Bar Graph Representations of

Etch Rates

SiO

2 -

1

SiO

2 - 5

SiO

2 - 9

SiO

2 - 1

5

SiO

2 - 1

7

S1390

425

400

360

760

420

435

420

400425

-100100300500700

900

Material and Wafer Number

Rate of Etch (A/min)

Etch Rates of 5 Minute Silicon Dioxide Processes using the Plasma Therm RIE

SiN -- 2min

SiN -- 2min

SiN -- 5min

S1

125100

85

020406080

100120140

Material Etched and Time

Rate of Etching (A/min)

Etch Rates of Silicon Nitride using the Advance Vac (Vision Oxide)

Conclusionso Silicon nitride deposition rates were more consistent than silicon dioxide depositions

using the Unaxis PECVD.o Silicon dioxide deposition rates were more consistent than silicon nitride depositions

using the STS PECVD.o Deposition rates for silicon dioxide and silicon nitride were more consistent using the

Plasma Therm PECVD.o Depositions rates are higher in the front of the chamber for the Plasma Therm

PECVD.o After maintenance (thorough cleansing) showed a 1% increase in uniformity.

o Etch rates for silicon dioxide using the Plasma Therm RIE varied but fell within the projected range most of the time.

o 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)

evaluating baseline deposition and etch recipes for silicon dioxide and silicon nitride using pecvd...

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