Dielectric Film Influence on Stress-Migration
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`A.lsobe, K Okamura, S.0gura and 0.Mizuno
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`NEC Corporation
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`ll2Z Shimokuzawa, Sagamihara, Kanagawa 229,
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`Japan
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`The
`this work is to clarify the relation between dielectric
`purpose of
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`film characteristics and stress-migration(SM).
`It has been considered
`that
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`caused
`temperature
`the dielectrics deposition
`induced
`stress,
`by
`the
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`difference of
`the expansion coefficients to Al,
`is
`the main factor for SM.
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`that
`the
`authors
`found
`diffusion
`into dielectrics,
`However,
`Al
`Al
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`recrystalization and dielectrics flexibility are also significant
`for SM.
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`or Al-Si wirings
`of dielectric films were deposited on Al
`kinds
`3%
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`oxidized
`Si wafers.
`Especially,
`sputter-SiO2, whose
`formed
`on
`film
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`charactaristics are not
`influenced by deposition temperature, was deposited
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`with following ways -
`(A)RT depo.,
`(B)l$flC depo.,
`(C)2EfiC depo., and (D)RT
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`depo.
`3BZC
`anneal.
`To evaluate the material
`dependence,
`(E)SiO,
`after
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`(F)Si0N and (G)SiN were depositted by PECVD under
`the same conditions except
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`process gas.
`These wafers were annealed at 403C for
`lflmin,
`held
`then
`at
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`hours
`l75C(N2)
`for
`evaluate
`the
`SM.
`The
`sample
`preparation
`Tflflfl
`to
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`conditions and results are shown in the tables.
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`the
`and
`Samp|e(A)
`(B)
`show more open failures than (C).
`in spite of
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`the
`same
`deposition temperature as (A),
`(D)
`shows no failure.
`In case of
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`(E)
`shows many,
`(F)
`shows
`few and (6)
`PECVD samples,
`shows no failure. All
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`the other samples show no failure.
`of
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`(B) and (C) can be
`the results of sample(A),
`The differences between
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`the
`explained
`Al atom diffusion into dielectricsfll‘ and dielectrics
`by
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`flexibility.
`in case of
`(A) or
`(B), high tensile stress is generated by the
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`Al diffusion into dielectrics during the annealing after the
`deposition. On
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`the contrary,
`in case of
`(C), as the diffusion occurs during deposition,
`the
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`stress is
`lower
`than that of
`(A),
`because the dielectrics is flexible until
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`it becomes a certain thickness.
`No failure in sample(D) can be explained as
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`follows. When Al
`film is heated up,
`the Al stress becomes compressive but,
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`over ZUEC,
`is reluxed by hillock formation and Al recrystalization.
`If
`the
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`reluxation
`wirings
`is
`covered with dielectrics,
`this
`stress
`(only
`by
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`recrystalization) causes the high tensile stress after cooled down. However,
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`the tensile stress is lower
`than (A),
`because the Al
`case
`in
`of
`(D),
`is
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`The
`already
`recrystalized
`the
`annealing
`before
`the
`deposition.
`by
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`differences between the results of
`(F) and (G) can be also explained by
`(E),
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`the Al diffusivity.
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`in conclusion,
`
`”depositting
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`reluxation.“
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`the best way of dielectrics formation against SM is,
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`low AI diffusivity dielectrics at
`low temperature after stress
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`(Reference)
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`[I] A.Tanikawa and H.0kabayashi,"AEM Observation of passivation films for Al
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`Metallization", Ext. abst. of The Jap. Soc. of Appl. Phys. Autumn 1989
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`P628
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`June 12-13, 1990 VMIC Conference
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`TH-0325-1/90/0000-0363 $01.00 C 1990 IEEE
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`MICRON ET AL EXHIBIT 1048
`Page 1 of 2
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`Dielectric Film Influence on Stress-Migration
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`A.lsobe, K.Ukamura, S.0gura and 0.mizuno
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`Tables
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`Typical data of dielectrics deposition conditions and
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`open failures after 7000H held in 1751? (NZ).
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`I-
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`Experimental® Pure Al
`(l'l=0.8um)
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`In
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`- In
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`-In
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`-wjjln
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`n
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`an ammun-
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`*1:Annealed by furnace
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`*2:T is for tensile stress, others are compressive
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`jwI
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`Experimentaléfi Al-1%Si
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`(W=U.8L£n1)
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`(%§I
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`<T1me>
`<T1me>
`EMPa)
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`31
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`-311
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`-11
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`!E—Wu
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`—EK
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`%—E
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`jflflj
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`*3:The same deposition conditions as (A)
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`*42No bias
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`*5!Set
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`EfE
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`is RT but wafer
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`temp.
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`temp. becomes 300*v350Y3 during depo.
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`No failure in polyimide and (no bias) S-Si02 can be explained by film flexi-
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`bility.
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`364
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`MICRON ET AL EXHIBIT 1048
`Page 2 of 2