non-contact sheet resistance for determining polish ......superior repeatability: 0.3% ncrs vs. 4pp...

Non-contact Sheet Resistance for Determining Polish RatesDetermining Polish Rates

KLA-TencorWalter Johnson, HaiJing Peng

Outline

• Abstract

• Technology• Technology

• Typical Performance• Repeatability

• Effects of frequency change

• Use Case• ECP Copper monitors• ECP Copper monitors

• Polish Rate on monitors

• ECP Copper on pattern wafers

9/16/20102 confidential

Abstract

Wi h h l f i fWith the move to larger wafers, monitor wafers are getting more expensive. The introduction of non-contact Rs measurements to replace traditional contact Four point Probe measurements saves money throughFour-point Probe measurements saves money through measuring directly on pattern wafers. There are also advantages when determining, polishing rates with a non-contact method in that 4PP generated particles ornon contact method, in that 4PP generated particles or pits are avoided allowing the same wafer to be used for both particle inspection and thickness. Eliminating these particles or pits can also prevent their affect on p p psubsequent polishing steps.


Non-contact Sheet Resistance (NCRs) capability for thick metal films

Technology : Technology : Conductive layer close to the coil modifies the

coil impedance

Benefits: Better repeatability performance on thick-metal layers with low resistivity (Cu)

Unaffected by surface oxidation Unaffected by surface oxidation

Superior Repeatability: 0.3% NCRs vs. 4PP at 0.5%

Product wafer capability – Rs measurement on complete Copper process (Barrier/seed, pre/post Cu CMP) No mechanical damage to the film or underlying structures

‘Real’ Rs for process monitoring of thick-metal layers

Reduces monitor wafer usage, low COO

9/16/20104 confidential4 confidential

Correlation between 4PP and NCRs

4PP & EC correlation16

NC

y = 0.9954xR2 = 1

12

14

16

8

10

s (O

hm/s

q)4PP & EC correlation

y = 0.9986xR2 = 0.99990.25

0.34

6EC

Rs

Result Spec.Correlation R=0.9999 R>0.99

0.1

0.15

0.2

EC R

s (O

hm/s

q)

0

2

0 2 4 6 8 10 12 14 16


0

0.05

0 0.05 0.1 0.15 0.2 0.25 0.34PP Rs (Ohm/sq)

4pp Rs (Ohm/sq)

Long Term NCRs Repeatability

10 Day Repeatability KT spec= 5 day <0.5%, Beta agreement 10 day < 0.5%

1.00

e

12.7 K Cu 12K Cu 11.5K Cu

9K Cu 3.5K Cu 1.5KCu

0.10

eet R

esis

tanc

e

0.01AM AM PM AM PM AM PM PM AM PM PM AM PM AM AM PM AM

She

AM AM PM AM PM AM PM PM AM PM PM AM PM AM AM PM AM

9/2 9/3 9/3 9/4 9/4 9/5 9/5 9/6 9/8 9/8 9/9 9/10 9/10 9/11 9/11 9/11 9/12Re pea t

NCRs 12 7 K Cu 12K Cu 11 5K Cu 9K Cu 3 5K Cu 1 5KCu


NCRs 12.7 K Cu 12K Cu 11.5K Cu 9K Cu 3.5K Cu 1.5KCuRepeatability 0.23% 0.19% 0.18% 0.15% 0.21% 0.35%

10MHz Long Term Repeatability (2)10MHz Long Term Repeatability (2)

Total 11 wafers(200mm), Rs : 0.003~6/, different film thickness/ material

Test conditions: 49 sites/test, 5 tests/day, 6days

1 is calculated based on Rs of each individual site

1 of individual site

(R, )

ThicknessMaterial

R (/ )


Rs(/ )

2MHz Dynamic RepeatabilityReduced 1 at extremely low Rs2MHz Dynamic RepeatabilityReduced 1 at extremely low Rs

Total 4 wafers(200mm), Rs : 0.003~0.02/, different film thickness/ material

Test conditions: 49 sites/test, 18 repeats, with load/unload

1 is calculated based on average Rs of each test

1 of 49 sites averageg

Reduced 1 by using low frequency

ThicknessMaterial

Rs(/ )


Rs(/ )

Measurement Range

NCRs is complementary to 4PP measurement, towards extremely low sheet resistance

1

1.2

4PP

Material Ratio

Cu 1.00

10µm 1µm .1µm 10nm 1nm 1A .1ACu= 1.7µ.cm .01A

0 6

0.8

1

(%)

NC 10MHzNC 2MHz

Al 1.64

Mo 3.02

W 3.22

Pt 6 09

0.4

0.6

1Sig

ma Under developmentPt 6.09

Ta 7.60

Ti 24.8

TiSi2 9.30

0

0.2

0.001 0.01 0.1 1 10 100 1000 10000 100000

TiN 12.8

TaN 130

Ag 0.94

Ni 4 20


Rs (Ohms/sq)Ni 4.20

Co 3.85

NCRs Edge Exclusion

Edge Exclusion (EE) Calculation:

EE = (Measured Gap - Physical Gap) / 2


NC Probe used in EE test: SN37817, w/ shield

Cross Wafer Uniformity Pre & Post Polish

Pre and Post Polish Diameter Scans With RS300 4PP and RS300 NCRs

16,000

17,000

18,000

14,000

15,000

,

Fil T

hick

ness

(Å)

Rs200 4PP 1585B PRE Rs200 E.C. 1585B PRE

Rs200 4PP 1585B PST Rs200 E.C. 1585B PST

11 000

12,000

13,000

Cop

per

10,000

11,000

1 9 17 25 33 41 49

Position across wafer (L-R)


Good correlation between 4PP and NCRs from the same tool

Copper Removal on 10 Wafers (EC vs 4PP)

Sequential Diameter Scans Across 10 Wafers (plotted on one chart)

Tool Comparison of Pre-Post Polish Measurement

12 000

14,000Wafer 1 Wafer 4Wafer 3 Wafer 5 Wafer 6 Wafer 7 Wafer 8 Wafer 9 Wafer Wafer 2

8,000

10,000

12,000

Rem

oval

(Å

Rs200 4PP Rs200 E.C.

2,000

4,000

6,000

Cu

R

01 51 101 151 201 251 301 351 401 451

Position across slots 1-12


Removal Rate Correlation

Removal Rate correlation

y = 0.9805x + 8.7746R2 = 1.000010,000

12,000

14,000

Removal is in total thicknessWith units in

4 000

6,000

8,000

,

RS2

00 E

C

With units in Angstroms (Å)

0

2,000

4,000

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000

RS200 4PP

P f t C l t l ti b t 4PP d NCR


Perfect Cu removal rate correlation between 4PP and NCRs

18 Month Operation (without re-cal)


NCRs Throughput

Throughput Tests

80

50

60

70

t

20

30

40

Thro

ughp

ut

0

10

20

0 10 20 30 40 50 60 70 80 90

Sites Spec Measured

5 40 59

Number of sites in pattern


49 15 17

81 6 7

Particle TestsBaseline

Slot # 1 2 3 4 5 6 7 8 9 10 Original Defects 373 251 232 329 204 284 234 283 286 289Defects Added 54 42 53 70 66 70 89 57 24 149 AvgTested Wafers 54 53 66 89 24 57.2Control Wafers 42 70 70 57 149 59.75

Slot 10 (a control) was the top wafer and was removed from

the calculations

Average of -2 PWP indicate

the calculations

there is no particles added


Pattern ECP Cu Demo Information

Demo purpose: Demonstrate the ability to measure sheet resistance of ECP pattern waferDemonstrate the ability to measure sheet resistance of ECP pattern wafer

with non-contact Eddy Current method on RS 300 platform, including: EC Rs correlation with Cu thickness

Dynamic repeatability without pattern recognition to show positioningDynamic repeatability without pattern recognition to show positioning accuracy and impact to measurement result

Wafers: ECP pattern wafer with ~ 1 µm electroplated Cu ECP pattern wafer with ~ 1 µm electroplated Cu

Diameter: 300 mm

Edge: ~2 mm edge clearance


Pattern Structure

Step x: 18.36 mm

Step y: 14 17 mm Step y: 14.17 mm

Upper Left Corner: (-6 mm, 0 mm)

-6 0-6,0

14 17mm

18 36mm

14.17mm


18.36mm

Small-Area Map

Map scan (2mm square) in a circular area of 80 mm diameter near the center

Scribe line

near the center Periodical RS pattern aligned with

dies and scribe line features Step X: 18 36 mm Step X: 18.36 mm

Step Y: 14.16 mm

View Notch

Scribe lineDie

View Notch

Die

9/16/201019 confidential Notch

Diameter Scan Across Whole Wafer

3 Line scans with step size 400 µm, 1 for x direction and 2 for y direction X scan at Y = 0 (diameter scan across COW)

Y scan at X = 0 (diameter scan across COW)

Y scan at X = -6 mm (scribe line)

0 021

0.022

0.023

Ohm

/sq)

X Scan at Y=0

Y Scan at X=0

Y Scan at X=-6mm

0.019

0.02

0.021Rs

(O

0.017

0.0182.5mm film

edge exclusion2.5mm film

edge exclusion


-150 -100 -50 0 50 100 150

X or Y (mm)

Diameter Scan Converted to Thickness

A typical copper resistivity of 1.85 µΩ-cm was used for this conversion. Lines scans at two X values are used for comparison.

1

1.05

0.95

1

ess(

um)

0.9Thic

kne

Y Scan at X=0

0.8

0.85Y Scan at X=-6mm


-150 -100 -50 0 50 100 150X or Y (mm)

Overall Map

Dense map with 1209 sites (square array, up to R = 145.5 mm) Some internal feature of the dies visible

Overall non-uniformity of Rs

150

100

150

0

50

-150 -100 -50 0 50 100 150

(ohm

s/sq

)

-100

-50 Rs


-150

Map at Scribe Line Crossing

Rs mapped at 262 scribe line crossing sites up to R = 145.9 mm No feature of die visible

Overall non-uniformity of Rs

X(mm) = -6.0 + column × 18.36

Y(mm) = +0 0 + row x 14 16

100

150Y(mm) = +0.0 + row x 14.16

0

50

-150 -100 -50 0 50 100 150 q)

-100

-50

Rs

(ohm

s/sq


-150

Short Term Repeatability Map on Die Center

Dynamic repeatability shows current system is well below the standard Rs system spec of 0.5% 254 dies, 20 load/unload repeats

0.025 0.5%Rs Avg

Average Rs and 1 sigma based on each die

Each line representsEach point

0 021

0.023

q) 0 3%

0.4%

%)

Rs Avg

Stdev(%)

Each line represents a row of diesrepresents the

mean of 20 repeats

0.019

0.021

Rs(

Ohm

/sq

0.2%

0.3%

1 Si

gma(

%

0.015

0.017

-150 -100 -50 0 50 100 1500.0%

0.1%Each point represents 1 of 20 repeats


150 100 50 0 50 100 150

Y(mm)

RS 300 (RS200 w/NCRs) is Complementary to 4PP

BENEFIT NCRs 4PP

Improved thick metal Rs measurement

No probing damage to films; inert to surface oxidation; better

repeatability

Performance subject to native surface oxide and probe metal

contamination

Blanket film on-product-wafer Rs measurement capability

Metal Rs capability on Cu ECP process. Measurement of

barrier/seed/Cu films on product wafer

Probing damage to patterned structures underneath metal films

wafer

No metal cross contamination Non-contact Residue metal on probe causes cross contamination

Lower CoO No consumables Probes are a consumable item

9/16/201025 confidentialSingle platform advantage Cover entire sheet resisitivity application space; on-tool calibration for

Eddy current; customers do not need to justify a stand-alone tool

Summary

Non-contact Rs (NCRs) or thickness shown for thick metal filmsfilms

NCRs can eliminate issues resulting from 4PP marks on monitors which could effect polishing, particle tests or p g preclaim

Huge cost savings

Product or pattern wafers can be used instead of monitor wafers in many cases (using die intersection values)

Potential valuable on-product information relating to over die or pattern values


non-contact sheet resistance for determining polish ......superior repeatability: 0.3% ncrs vs. 4pp...

Documents