development of a porous low-k precursor...

DEVELOPMENT OF A POROUS LOW-K PRECURSOR TO PROVIDE ENHANCED MECHANICAL PROPERTIES WITHOUT SACRIFICING CARBON CONTENT

William R. Entley; Jennifer L. Achtyl; Raymond N. Vrtis, Jianheng Li and Robert G. Ridgeway

SEMICON Taiwan 2016

9 September 2016

Versum Materials Company Confidential

2 Versum Materials Company Confidential

PRESENTATION AGENDA • Versum Materials PECVD Processing Capabilities

• Evolution of low-k offerings

• Introduction of pore former AP-LTO® 288

• Development of Structure Former AP-LTO® 878

– Development of BKM for various k values

– Resistance to plasma induced damage

• Summary of AP-LTO® 288/AP-LTO® 878 Development

VERSUM MATERIALS PECVD PROCESS TOOL CAPABILITIES

• 200 mm Applied Materials P-5000® - 4 chambers: 3 Deposition chambers & 1 UV cure chamber

• 300 mm Producer® SE Depositions - ULK (PDEMS®) thin film deposition - UV curing of low-k films - Silicon oxide and nitride deposition

• New Material Development - Development of new precursors - Direct Liquid Injector test stand

• New Process Development - Low Temperature PECVD thin films for emerging technologies

(e.g., TSV) - Flowable CVD (FCVD) for bottom up, seamless gap fill


EVOLUTION OF LOW-K PRECURSOR DEVELOPMENT


OSG Structure Formers

DEMS® Currently in HVM

AP-LTO® 878 New precursor that enhances modulus without sacrificing Carbon content.

Porogens

ATRP Currently in HVM

AP-LTO® 288

New Porogen that increases mechanical strength of DEMS® and AP-LTO® 878 films. Extends DEMS® application to 22nm and beyond where higher mechanical properties are required

BCHD Currently in HVM

Development of AP-LTO® 878 to bridge the carbon content gap between DEMS® -ATRP and DEMS® -AP-LTO® 288 while maintaining mechanical properties

Commercialized R&D

DEMS® + AP-LTO®288

DEMS® + ATRP

DEMS® + BCHD

Increasing Carbon Content

Incr

eas

ing

Mo

du

lus

AP-LTO ® 878 + AP-LTO®288

AP-LTO® 288 – MECHANICAL PROPERTY ENHANCEMENT

• Relative mechanical strength decrease faster than k as porosity increases and carbon is added to the film • For a given k value, AP-LTO® 288 provides films with significantly higher modulus than ATRP and BCHD based

films • AP-LTO® 288 strengthens the Si-O network, allowing for higher porosity and thus lower k values to be achieved • For integration schemes at 22nm and beyond requiring high mechanical strength, pore former AP-LTO® 288

combined with DEMS® yields films with enhanced mechanical properties


DEMS®/AP-LTO® 288

DEMS® / ATRP

AP-LTO® 288 BKM PROCESS DEVELOPED ON VERSUM 300mm TOOL

6 6 Versum Materials Confidential

k Mod. (GPa)

AD NU1 (%)

Cured NU1 (%)

Shrinkage (%)

%C2 %Si2 %O2

2.6 10.4 1.6 2.1 11 13 37 50

DEMS®/AP-LTO®288 BKM

DEMS®/ATRP Baseline

Parameter DEMS/AP-LTO 288

Pressure (Torr) 7.5

RF Power (W) 930

DEMS (mg/min) 880

AP-LTO 288 (mg/min) 3520

O2 (sccm) 125

Deposition Rate (nm/min) 309

> 40% Increase in Elastic Modulus for DEMS/AP-LTO® 288 Obtained for BKM

relative to DEMS®/ATRP

Film Targets • K = 2.6 • Modulus > 9 Gpa • Maximum %C • Minimum StDev NU %

k Mod. (GPa)

AD NU1 (%)

Cured NU1 (%)

Shrinkage (%)

%C2 %Si2 %O2

2.5 7.2 1.0 1.1 15 15 34 51

RESISTANCE TO PLASMA INDUCED DAMAGE (PID)

• PID caused by stripping of carbon from film (-CH3) during integration

• The Depth of Damage (DoD) determined by how deep reactive radicals can penetrate into the film - Lower k and higher porosity will increase

DoD - Higher C density will reduce DoD by

providing more reactive sites near films surface

• Damaged films are converted to Si-OH resulting in k loss and higher wet etch rates

• AP-LTO® 878 reduces DoD thru incorporation of increased carbon density


Etch/ash Chemical wet clean

DEVELOPMENT OF AP-LTO® 878 STRUCTURE FORMER FOR NEXT GENERATION LOW-K APPLICATIONS • Precursor when combined with pore former AP-LTO® 288 designed to add carbon while

maintaining mechanical properties thru formation of methylene and ethylene bridging as determined by 13C NMR

• Precursor selected had vapor pressure comparable to current low-k precursor for ease of HVM adoption


Deconvolution of the Solid State 13C NMR Spectrum k = 2.3 AP-LTO® 878/AP-LTO® 288 BKM

VP Curves comparison for DEMS® , ATRP, AP-LTO® 878 and AP-LTO® 288

Si-CH2-Si

AP-LTO® 878 BKM DEVELOPMENT

• Several BKM films developed for AP-LTO® 878 - k 2.3, k 2.4, k 2.6 and k 2.8 (single precursor) - Targeted higher modulus relative to DEMS® /ATRP - Targeted higher carbon content relative to DEMS® /AP-

LTO® 878 - Experimental design approach on Producer® SE used to

optimize for film properties - Plasma Induced Damage (PID) using industry standard model


EXPERIMENTAL STRATEGY FACE CENTERED CENTRAL COMPOSITE DOE


Experimental Run

Power (Watts)

O2

(sccm) TFR

(mg/min) AD NU

(%) Modulus

(GPa) k %C

Dep Rate (nm/min)

Hardness (GPa)

Density (g/cc)

1 750 88 4250 1.8 6.0 2.33 19 149 1.07 1.15

2 750 88 4250 1.8 6.0 2.32 18 149 1.06 1.12

3 600 50 3500 2.2 74 2.40 15 101 1.33 1.19

4 600 125 5000 1.4 8.6 2.53 15 93 1.55 1.25

5 900 50 5000 2.0 6.5 2.41 16 207 1.18 1.17 6 900 125 3500 1.7 3.2 2.27 35 232 0.54 1.09

7 900 50 3500 2.2 4.1 2.38 44 236 0.74 1.12

8 750 125 4250 1.9 5.5 2.31 19 149 0.99 1.12

9 750 87.5 3500 2.1 4.3 2.28 25 164 0.75 1.08

10 750 87.5 5000 1.8 8.0 2.44 15 143 1.44 1.21

11 750 50 4250 2.1 6.6 2.37 20 150 1.18 1.15

12 600 87.5 4250 1.9 8.1 2.48 15 96 1.50 1.22

13 900 87.5 4250 2.0 4.5 2.30 28 218 0.77 1.09

14 900 125 5000 1.7 5.6 2.34 21 205 0.99 1.13

15 750 87.5 4250 1.9 6.0 2.34 18 150 1.03 1.14

16 600 50 5000 1.8 11 2.61 15 90 1.91 1.30

17 600 125 3500 1.9 5.6 2.37 18 105 1.00 1.12

Parameter Value

%Porogen in AP-LTO® 878/AP-LTO® 288 87.5%

Pressure (Torr) 8.0

He_c_AP-LTO® 288 (sccm) 500

He_c_AP-LTO® 878 (sccm) 500

Temperature (deg C) 280

Spacing (mils) 300

AP-LTO® 878/AP-LTO® 288 Fixed Parameters

Film Targets • K = 2.3 • Maximum elastic

modulus • AD Stdev NU <3%

Parameter Lower Limit Upper Limit

Power (Watts) 600 900

O2 (sccm) 50 125

Total Flow Rate : AP-LTO® 878 + AP-LTO® 288 (mg/min)

3500 5000

k 2.3 – 2.6

Mod 3.2 – 11 GPa

%C (Atomic, XPS) 15 – 44

NU 1.7 – 2.2 %

Range of Results

2 3 4 5 6 7 8 9 10 11 122

3

4

5

6

7

8

9

10

11

12

Obse

rved

Ela

stic M

od

ulu

s (

GP

a)

Predicted Elastic Modulus (GPa)

10 15 20 25 30 35 40 45 5010

15

20

25

30

35

40

45

50

Obse

rved

XP

S C

arb

on (

%)

Predicted XPS Carbon (%)

10 15 20 25 30 35 40 45 5010

15

20

25

30

35

40

45

50

Obse

rved

XP

S C

arb

on (

%)

Predicted XPS Carbon (%)

PREDICTED VS. ACTUAL RESULTS FOR K, EM AND % C AP-LTO 878/AP-LTO 288


Excellent agreement was observed between the experimental results and the results predicted by the statistical model. The statistical model is an important tool for understanding the parameter space explored and for predicting deposition conditions that result in targeted film properties.

Elastic Modulus (GPa) Carbon, Atomic % by XPS Dielectric Constant, K

RESPONSE SURFACE MODELS FOR k, ELASTIC MODULUS AND % C AT FIXED O2 FLOW (50 sccm)


Dielectric constant and modulus exhibit similar trends: lower dielectric constants and lower moduli are favored by higher power and lower total flow rates. The same operating conditions favor higher

carbon incorporation into to the film.

Dielectric Constant Modulus %C, XPS

*Total Flow (mg/min) = AP-LTO 878+ AP-LTO 288 (mg/min)

AP-LTO® 878/AP-LTO® 288 BKM DEVELOPMENT SUMMARY


Precursor(s) K EM (GPa)

% C Si(CH3)/SiOx (x100)

Porosity (%)

AP-LTO®878/AP-LTO®288 2.3 5.6 23 1.7 32

AP-LTO®878/AP-LTO®288 2.4 8.1 17 1.9 27

AP-LTO®878 2.8 12.1 22 2.3 11

AP-LTO®878/AP-LTO®288 2.6 11.6 18 1.7 23

DEMS®/AP-LTO®288 2.6 10.4 13 1.5 23

Comparative DEMS® data included for k 2.6 films

DETERMINATION OF PID: METHODOLOGY

• Deposit film on 300mm wafer - Collect 29pt reflectometer map

• UV Cure Film - Collect 29pt reflectometer map - Measure k

• Break wafer into 35 pieces - Measure thickness of individual pieces

• Expose the films to NH3 plasma stripping conditions to damage the films:

• Measure thickness of individual pieces post damage and measure k

• Quantify the depth of damage (DoD) via - Thickness loss following exposure to a 1:300 HF/H2O

solution (wet etch rate or WER). - Measurement of thickness of individual pieces after

HF etch


NH3 Plasma NH3 200 sccm; 4.5 Torr 300 Watts; 300 ⁰C; 15

secs

Si Wafer Undamaged low-k film

Damaged, carbon-depleted low-k film

1. Ryan, E. T. et. al. “Property Modifications of Nanoporous pSiCOH Dielectrics to Enhance Resistance to Plasma-Induced Damage” J. Appl. Phys. 2008, 104, 094109-1 – 094109-7.

0 100 200 300 400 500 600 700 8000

10

20

30

40

50

60

70

80

90

100

R2=0.93

R2=0.98

R2=0.93

R2=0.93

R2=0.85

R2=0.95

R2=0.86

k=2.5 DEMS/ATRP

k=2.4 DEMS/AP-LTO 288

k=2.4 AP-LTO 878/AP-LTO 288

k=2.8 AP-LTO 878 (BKM2), Post UV

Thic

kn

ess L

oss (

nm

)

Exposure Time to Dilute HF (sec)

R2=0.93

1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.420

25

30

35

40

45

50

55

De

pth

of

Da

ma

ge

by W

ER

(n

m)

Si(CH3)

x/SiO

x*100

R2=0.94

DoD FOR PLASMA DAMAGED k 2.4 & k 2.8 FILMS


k

Elastic Modulus

(GPa)

DoD WER (nm)

Porosity (%)

% C (XPS)

Si(CH3)x/SiOx *100

DEMS

/AP-LTO

288 2.4 9.4 ~ 52 27 13 1.6

AP-LTO

878/AP-LTO

288 2.4 8.1 ~ 32 27 17 1.9

DEMS

/ATRP 2.5 7.2 ~ 25 23 15 2.3

AP-LTO

878 (BKM2); Post UV 2.8 12.4 ~ 13 ~ 9 24 2.4

Depth of PID by Wet Etch Rate Si(CH3) Density vs Depth of PID

Trend valid for films with similar k values.

Lower Limit for depth of PID

k=2

.5

DEM

S/A

TRP

k=2.4 AP-LTO 878/ AP-LTO 288

k=2

.4

DEM

S/A

P-L

TO

288

Thic

knes

s Lo

ss (

nm

)

Exposure Time to Dilute HF (sec)

De

pth

of

Dam

age

by

WER

(n

m)

Si(CH3)x/SiOx*100

Film Damage: 15 second exposure to a low power NH3 plasma

Thickness Loss Graph • Initial steep rise in thickness

loss; damaged portion of film. • Leveling out of thickness loss

at longer HF exposure time; undamaged portion of film.

• Knee of the curve defines thickness of damaged region.

PORE DENSITY AND SIZE DISTRIBUTION


0.0 0.5 1.0 1.5 2.0 2.5 3.00.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Mic

rop

oro

us P

ore

Siz

e D

istr

ibu

tio

n

Diameter (nm)




k=2.8 AP-LTO 878 (BKM1)

0.0 0.2 0.4 0.6 0.8 1.0

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Volu

me F

raction

Poro

sity

P/Po



k=2.5 DEMS/ATRP

k=2.8 AP-LTO 878 (BKM1)

k

Elastic Modulus (GPa)

Porosity (%)

% C (XPS)

Si(CH3)x/SiOx *100

DEMS

/AP-LTO

288 2.4 9.4 27 13 1.6

AP-LTO

878/AP-LTO

288 2.4 8.1 27 17 1.9

DEMS

/ATRP 2.5 7.2 23 15 2.3

AP-LTO

878 (BKM1) 2.8 10.9 9 14 2.7

Film Porosity Pore Size Distribution

k=2.4; 27%

k=2.5; 23%

k=2.8; 9%

Smaller pores observed for “dense” single precursor-based film

Vo

lum

e F

ract

ion

Po

rosi

ty

P/Po

Mic

rop

oro

us

Po

re S

ize

Dis

trib

uti

on

Diameter (nm)

Data generated using Ellipsometric Porosimetry

AP-LTO®878/AP-LTO®288 SUMMARY

• AP-LTO® 878/AP-LTO® 288 allows users to introduce bridging carbon in dielectric film - Easy to implement in existing process - Enhances modulus without sacrificing carbon content - Improves damage resistance of film relative to DEMS® structure former when

coupled with pore former AP-LTO® 288

• Industry standard based Depth of Damage studies have demonstrated the improved performance of AP-LTO® 878/AP-LTO® 288

• Versum has developed BKM for films with dielectric constants of 2.3, 2.4, 2.6 and 2.8 - BKM development on an industry standard tool allowing for ease of transfer - Use of statistical modeling approach allows for changes in process parameters to

meet specific customer targets


THANK YOU


development of a porous low-k precursor...

Documents