Mask Contribution to In tra-Field Wafer OverlayThe previou s that a much and reduce t h on critical...

Mask Contribution to Intra-Field Wafer Overlay

William Chou1, Hsien-Min Chang1, Chao Yin Chen1, M. Wagner4, K.-D. Roeth2, S. Czerkas2, M.

Ferber2, M. Daneshpanah3, F. Laske2, R. Chiang5 , S. Klein3

1 UMC, Tainan Science Park, Taiwan 2 KLA-Tencor GmbH, Germany

3 KLA-Tencor Corp., USA 4 KLA-Tencor Israel

5 KLA-Tencor Taiwan

ABSTRACT

Shrinking wafer overlay budgets raise the importance of careful characterization and control of the contributing components, a trend accelerated by multi-patterning immersion lithography [1]. Traditionally, the mask contribution to wafer overlay has been estimated from measurement of a relatively small number of standard targets. There are a number of studies on test masks and standard targets of the impact of mask registration on wafer overlay [2],[3]. In this paper, we show the value of a more comprehensive characterization of mask registration on a product mask, across a wide range of spatial frequencies and patterns. The mask measurements will be used to obtain an accurate model to predict mask contribution to wafer overlay and correct for it. Keywords: Mask registration, pattern placement, intra-field wafer overlay, multi-patterning lithography, optical lithography extension, overlay process control

1. INTRODUCTION

Reducing total wafer overlay error is one key factor to achieve and maintain high yields in wafer production when shrinking design rules. In addition to the various error contributions from the wafer scanner, the reticles used for the lithographic process contribute errors as well. Accurate placement of the features on reticles with a registration error below 4nm is mandatory to keep overall photomask contributions to overlay of sub 20nm logic within the allowed error budget.

Overlay control is achieved by defining one set of process correction parameters per exposure field that must account for all contributors. Typically the corrections are calculated in some type of feedback loop independently of their origin. We have developed a new approach for overlay process control that provide a finer tuning of process correction by separating the contributors that exist outside of lithography process, such as mask error. When characterized individually, the total process correction is more stable and allows for a tighter overlay budget.

With a comprehensive characterization of the mask set, it is now possible to predict the error contribution from a given mask set separately for various types of features located throughout the imaging area. This type of analysis can then be used to improve further wafer yield by means of feed forward control mechanism already adopted in wafer process control to correct for after develop to after etch difference.

Previous investigations [4] demonstrated that conventional mask metrology on registration targets does not provide sufficient information on total mask registration error. In addition to the low order global signature which can be observed with standard registration metrology on targets, higher order global and local signatures as well as a pattern dependent systematic component could be identified on various customer test masks [4]. However, any previous generation mask registration metrology tool could not measure accurately on unlimited feature shapes. This gap prevented obtaining accurate results on various in-die features (figure 1, left) and especially prevented from accurately evaluating displacement of actual device features versus overlay and registration targets.

Metrology, Inspection, and Process Control for Microlithography XXVIII, edited by Jason P. Cain, Martha I. Sanchez, Proc. of SPIE Vol. 9050, 90501Q · © 2014 SPIE · CCC code: 0277-786X/14/$18 · doi: 10.1117/12.2049000

Proc. of SPIE Vol. 9050 90501Q-1

Downloaded From: http://proceedings.spiedigitallibrary.org/ on 04/07/2014 Terms of Use: http://spiedl.org/terms

The previousthat a much and reduce thon critical lay

For above mintra-field ovoverlay, it wademonstratedperformed in

Fig. 1: Formmask metro

The registratreticle with treticles are measurementgeneration maddition to thcorrects for aeffects from

Actual devicscribe line ofline. For intr2 displays th

Initial data evsoftware LMsoftware pacadvanced wacontribution intra-field ov

s evaluations olarger amounhe risk of misyer production

mentioned reasverlay data. Tas assumed thd [4], this assun a joint projec

mer gaps in masology tool solve

tion error wasthe top mark the poly lay

ts were perfomask metrolog

he standard rany residual erneighboring f

e patterns werf the multi-di

ra-field evaluae feature type

valuation on tMS DEVA. Mckage K-T Aafer process to wafer over

verlay.

on KLA-Tencnt of measuremsqualificationn reticles of m

son, there waTherefore, as hat the mask cumption may oct.

sk registration qes mask metrolo

s investigated of the same

yer and the ormed on eacgy tool. This megistration anrror contributifeatures on the

re evaluated ine reticles. In

ation, the sames measured. T

the reticle dataMore comprehAnalyzer™ wh

control (APCrlay taking int

cor’s newest gments is requi. These result

mask contribut

as no measurelong as thereontribution wor may not be

qualification (leogy dilemma an

2. EXPE

for two reticloverlay targecontact laye

ch reticle. Thmetrology toond overlay maion from the me mask.

n addition to saddition, twoe 30 logic and

The metrology

a sets was perhensive data hich enables C). This softwto account IPR

generation masired to improvts obtained ontion to intra-fi

ement system was no indic

was within the e true on produ

eft). New modend enables accu

ERIMENTA

les (one with et) of a logic er. For this ihe measureml has the capa

arks or simplemetrology too

standard regis types of propd 30 SRAM cy layout of the

rformed by KLanalysis was full wafer ov

ware packageRO data and t

sk metrology ve the qualityn various testield wafer ove

available whcation on anyaccepted errouction reticles

el-based algoriturate in-die mea

AL SETUP

the bottom mdevice alread

in-depth analments were pe

ability to accue in-die patterol optics or illu

stration and ovprietary test pcells were meae reticles is sho

LA-Tencor’s pthen perform

verlay analyse enables the thus simulates

tool [4] led toy of the registr

masks triggererlay.

hich can provy mask relatedor budget. As ts and more det

hm on KLA-Teasurement on di

P

mark of an ovedy in high volysis more th

erformed on Kurately measurrn. The new mumination and

verlay (combipatterns were asured in eachown in figure

proprietary LMmed by KLAsis and feed f

analysis of s the impact o

o the overall coration metrolored further ev

vide productiod impact on ithe previous etailed evaluati

encor’s next genifferent features

erlay target, tholume produchan 1000 reKLA-Tencor’re any patternmodel-based ad account for p

ned AIM) mameasured in t

h of the 15 die3.

MS IPRO dataA-Tencor’s co

forward capamask-to-mask

of the reticles

onclusion ogy result valuations

on worthy intra-field evaluation ions were

neration s (right)

he second ction. The egistration ’s newest n in-die in algorithm proximity

arks in the the scribe es. Figure

a analysis ommercial ability for k overlay on wafer



-4500(0 -30000 -15000 0 15000 330000 4500060000

.. l

45000

30000

5000

-15000

-30000

-45000

-60000

Fig. 2: Regis

3.1. Mask Registration the registratibecause of in

Knowing thalinear modelthe individua>1000 sites o

stration perform

Fig. 3: Regist

performanperformance on and AIM t

ntellectual pro

at production w, all following

al mask registron the contact

mance was evalu

tration metrolog

nce analysiswas evaluatedtargets on pol

operty reason s

wafers are geng mask data iration perform mask (right).

uated on severaline. All dime

gy performed o

3. EVAL

s by LMS Dd for each maly (blue) and since both ma

nerally procesin this study wmance based o

al types of intra-ensions are at re

on more than 10

LUATION R

DEVA ask individualcontact mask

asks are actual

ssed on the scwere processeon the metrolo

-field cell pattereticle scale

000 locations di

RESULTS

lly by LMS Ds (red). The inl product mask

canner with a ed and first orogy targets (le

rn besides stand

istributed over t

S

DEVA. Figure n-die feature ks.

process correrder errors remft and center)

dard targets in t

the reticle

4 shows the layout is not

ection generatemoved. Figure, as well as ov

the scribe

design of displayed

ed from a e 5 shows ver all the



Fig. 4: Metr

Fig. 5: Reg

(ri 3.2 Mask Most of the and overlay.

From the inscanner corrregistration treticles.

During expofirst order (6wafer overlay

In order to mof each masreduction ratand provide benefit as a f

Finally we cprocess correbudget whenmarks. For th

rology target la

gistration perforight) of individ

contributiopatterns preseBelow only th

ndividual masrection strategtargets, overla

osure, the scan6 terms) or a hy.

minimize the csk is loaded itio, orientationthe lithograph

function of com

compare the pection from o

n overlay conthe product use

ayout per reticle

rmance (range/2dual masks as ev

on to waferent on the polhe x data are r

k registrationgies. Several ay targets (co

nner recipe gehigh order mo

contribution ointo K-T Anan and rotationhy engineer wmplexity.

process correcone set of featrol is done oned in that stud

e. Actual device

2 in [nm]) versuvaluated by LM

r overlay ly mask are vreported.

n data, the msubsets of m

ombined AIM

enerally calls odel (3rd, 15 te

f the mask setalyzer and aun. K-T Analywith multiple

ctions from eatures onto ann the poly/condy, yield is m

e design is not d

us design data oMS DEVA softw

vertical lines, t

mask-to-mask mask registratiM), features in

for a correctierms) to remo

t error to the utomatically tzer is then usprocess corre

ach group of nother set of ntact mask paore sensitive t

displayed becau

on overlay targeware (first order

therefore the

overlay is evion data were

n logic areas a

ion on the retove (or reduce

overall overlatranslated intosed to analyzeections based

f patterns indifeature. Fig.7

air based soleto an increase

use of intellectu

ets (left and cenr systematic err

study was foc

valuated takine created for and features i

ticle stage usine) the systema

ay budget, theo wafer scalee the data usinon different

ividually and 7 shows the ly on 1 type o

e in overlay er

ual property rest

nter) and of all fors removed)

cused on x re

ng into accouthis purpose

in SRAM are

ng a linear matic error on i

e raw registrate, with the apng pre-definemodels, to di

the impact oimpact on thof feature, e.grror on SRAM

trictions

features

egistration

unt wafer , such as

eas of the

model or a intra-field

tion result ppropriate ed models isplay the

of using a e overlay g. overlay

M features



(right) compcorrection pa

Fig. 7: Conto

Fig. 8 displabetween the p

To assess thefeatures on wfeatures (figu

ared to logic farameters to fa

our plot of rema

ays the linear process correc

e final impactwafer for two ure 9).

features (centavor SRAM fe

aining overlay w(left), logic cel

terms (in x-dction sets is th

t on overlay bcases, first u

Fig. 8: Linea

ter). Knowing features.

when process cll (center) and S

direction) calche x-offset (0th

budget, we casing only info

r terms of proce

that, the litho

orrection generSRAM cell (righ

culated for feah order).

lculate and coormation base

ess correction f

ography engin

rated from overht) in arbitrary

ature subsets.

ompare the pred on overlay

for each feature

neer can choos

rlay marks are aunits (a.u.)

It appears th

redicted overlmarks and se

e set (a.u.)

se to adjust th

applied to overl

hat the main d

ay error on thecond based o

he process

ay marks

difference

he SRAM on SRAM



Fig. 9: Compa

With a compgiven mask scan then be been adopted

As the restrvarious in-diNow, the acimportant ev

It could be vwas offset inLogic area m

This systemacorrected by

There are now

1. Theman

2. The

In both caseswith the new

arison of mask c

prehensive chaset separatelyused to furthe

d in wafer pro

ricted capabilie features, it ccurate modelaluation.

verified on a ln mask-to-ma

mask-to-mask o

atic displacemthe standard o

w two potenti

e actual intra-nufacturing ine lithography e

s, measuremew generation of

contribution on

4.

aracterization y for various ter improve wcess control to

lity of previowas not possil-based algori

logic device mask overlay veoverlay did re

ment on the roverlay target

ial solutions fo

-field mask m order to writeengineer can c

ents must be bf registration m

n SRAM featuregenerated o

SUMMAR

of the mask types of featur

wafer yield by o correct for a

ous generatioible to investiithm of the n

mask pair (polersus the “comeveal a much s

reticles contrits.

or this intra-fi

metrology dae better maskschoose to adju

based on accumetrology too

es using a linearn SRAM measu

RY AND C

set, it is now res located thmeans of fee

after develop t

ns mask metrigate the masknew mask me

ly and contactmbined AIM”smaller offset

ibutes to the

ield overlay pr

ata can be fes. (Figure 10)ust the process

urate in-die mol.

r model generaurement

CONCLUSIO

possible to phroughout the ed forward coto after etch d

rology tools pk contributionetrology syste

t layer) that in” overlay test .

wafer overla

roblem:

d back to th

s correction pa

mask registratio

ted on overlay

ON

redict the erroimaging area

ontrol mechanifference.

prevented accn to intra-fieldem from KLA

ntra-field pattpattern and t

ay, since it ca

he e-beam wr

arameters to f

on data which

marks and a lin

or contributioa. This type ofnism which ha

curate measurd wafer overlaA-Tencor ena

tern of the SRthe registratio

annot be dete

riting system

favor SRAM f

h can now be

near model

n from a f analysis as already

rement of ay before. ables this

RAM area on targets.

ected and

in mask

features.

e obtained



Fig. 10: Full in order to m

[1] ITRS: Inthttp://ww

[2] G.T. Hua2011

[3] K. Bubke011004 (J

[4] K-D. Roe

mask characterake better mask

ternational Teww.itrs.net/Linang et al: Mask

e: Mask chara(Jan-Mar 2009eth et al, “In-d

rization enabledks. In addition,

potentially

echnology Roanks/2012ITRSk registration

cterization for9) die mask regis

d with new masthe mask data c

y to generate a m

RE

admap For SeS/Home2012.himpact on intr

r double patte

stration for mu

k metrology toocan be forwardemodified scann

EFERENC

emiconductorshtm rafield on-wa

rning lithogra

ultipatterning,

ol from KLA-Ted to the wafer

ner alignment sc

CES

s Update 2012

fer overlay pe

aphy, J.Micro/

” Proc. SPIE

Tencor can be fefab for K-T An

cheme.

2 Tables,

erformance, P

/Nanolith. ME

8880-79, 201

ed back to e-beanalyzer investig

Proc. SPIE

EMS/MOEMS

3

am writer gation and

7971-5,

8(1),



Mask Contribution to In tra-Field Wafer OverlayThe previou s that a much and reduce t h on critical...

Documents

Transcript of Mask Contribution to In tra-Field Wafer OverlayThe previou s that a much and reduce t h on critical...