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` This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP: 72.37.248.4
`On: Tue, 27 Jan 2015 22:40:19
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`Page 1 of 3
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`SAMSUNG EXHIBIT 1045
`
`

`

`GROWTH
`ltMPERAlURE
`und‘ c
`la];
`975
`
`BACK SIDE MASK
`SID2
`Si N
`Jo“
`a
`A
`
`ICONCAVI'I
`
`CHANGEINcunvnunino4m".
`
`mmmssormuwnsso,
`
`(X)
`
`FIG, 2. Sample curvature induced by stresses in thermal SiOz grown in wet
`02 on (I 1 l) and (I00) samples versus SiO, thickness. The line represents
`the curvature introduction expected for an SiOz stress level of 7 x 10 9
`dyn/cm 1.
`
`temperature (time = O) is caused by the differences in ther-
`mal expansion between Si and SiO2 . The Si3N4 back-mask
`sample in Fig. 1 has less curvature at room temperature and
`is curved in the opposite direction to that of the SiO2 back-
`mask samples because the SiaN4 on the back is thin and in
`tension while the SiO2 on the back of the other two samples
`is thick and in compression. As seen in Fig. 1, after entry into
`the furnace, the samples straighten up as they equilibrate
`with the furnace (which takes approximately 5—8 min). If
`there is stress in the growing oxide, the samples continue to
`bend as seen in the 900 °C data, which shows continual bend-
`ing for times greater than 10 min. Note that the 1000 °C data
`shows no bending during SiO2 growth (times greater than 10
`min, which leads to the conclusion that the SiO2 is growing
`stress free at this temperature.
`Data such as that in Fig. l were obtained at several
`temperatures around the viscous flow point of 965 °C. Re-
`sults were analyzed as follows to obtain a best estimate for
`4K0 , the value of curvature at growth temperature for zero
`SiO2 thickness, rm}. A plot of raw data such as in Fig. 1
`versus 75,02 exhibits an easily identified slope in the data for
`times after about 8 min. The intercept ofthis straight portion
`at zero rs“), is taken as AKO for that sample. The value of
`AK0 was generally different from zero (fiat) because of a
`constant stress in the back mask. The value for AKO was
`subtracted from the data taken after 8 min and the resulting
`data replotted versus Si02 thickness 15,01. Thickness 75,01 as
`a function of time was estimated by measuring the final oxide
`thickness and using published 75,02-vs-time plots for steam
`growth of SiO2 shifted to match the final thickness-time
`
`9
`
`Appl. Phys. Lett.. Vol. 35. No. 1, 1 July 1979
`
`data point (a typical run at 1000 °c grew 3200 A in 3 h).
`Results are shown in Fig. 2 for various growth temperatures.
`Note first of all in Fig. 2 that there is a dramatic differ-
`ence in going from 950 to 975 or 1000 °C for both the (111)
`and (100) samples. Also note that the results for either back-
`mask choice are essentially the same for a given growth tem-
`perature, thus assuring that the major effects are due to
`stress (or lack of stress) in the growing SiOz.
`The results for the Si3N, back-mask samples tended to
`level off as 75,0: exceeded 600 A. This is not understood at
`present, but the quality of our Si3N. films and their contin-
`ued masking ability is suspect because their etch rates in
`room-temperature HF are far too high (500 A/min) even
`though the index of refraction (1.97) is consistent with low-
`Oxygen-content material. The SiOz back-mask results at
`growth temperatures of950 °C and below show that the sam-
`ples continue to curve as long as SiO2 continues to grow.
`A line is included in Fig. 2 to indicate the level ol‘stress-
`es seen in the SiOz during growth. The curvature change AK
`is proportional to the integral of the stress through the oxide
`thickness. If we assume that the oxide stress is constant
`
`through 15,02, AK is proportional to 75,02 and is related to the
`stress in the SiO2 , 55,0), by
`
`AK =
`
`6Sssofl'smfl " Vs.)
`
`,
`
`Estéi
`
`(2)
`
`where 1'si is the sample thickness and Esi and vsi are
`Young’s modulus and Poisson‘s ratio, respectively. Letting ‘
`E5,(l — 115,) ‘ ‘ = 2.28X10'2 dny/cm 2, the line in Fig. 2 is
`plotted for 55,0) = 7 X 109 dyn/cm 2. This value of stress is
`large compared to the room-temperature stresses of 3 X 10 9
`dyn/cm 2 set up during cooldown 7 by the differences in ther-
`mal expansion for Si and SiO2 . Prediction of the existence of
`stress during growth by examination of the room-tempera-
`ture stresses in our samples after cooldown has been incon-
`clusive because there is apparently some occasional relief or
`compaction of the stressed films during cooldown. More
`work is needed here.
`
`Near discontinuities in the growing oxide, shear stress-
`es will exist in the SiO2 and Si near the Si/SiO2 interface.
`These shear stresses are ofthe order ofthe compressive stress
`in the oxide and are proportional to the integral over 15,02 of
`the oxide stress. Since the recently measured 6 critical stress
`for shear flow in Si at 1000 °C is 3.4x 107 dyn/cm 1, it is
`entirely plausible to see plastic deformation of Si beneath
`discontinuities in growing SiO2 layers (near the edges of
`windows, etc.). In other words, the present results show that
`high stresses can exist in our SiO2 at growth temperature
`where the Si is mechanically weak.
`The possibility of a tensile stress in the SiO2 growing at
`1030 ‘C is seen in Fig. 2. This result is tentative because the
`effect is small and has not been checked yet at higher
`temperature.
`Several runs using dry 02 were attempted. The much
`reduced growth rate of thermal SiO2 in dry 02 made the
`experiments more difficult. Preliminary results suggest that
`the stress levels are much reduced over those seen in Figs. 1
`
`E.P. EerNisse
`
`9
`
`SAMSUNG EXHIBIT 1045
`Page 2 of 3
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`SAMSUNG EXHIBIT 1045
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` This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP: 72.37.248.4
`On: Tue, 27 Jan 2015 22:40:19
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`Page 3 of 3
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`SAMSUNG EXHIBIT 1045
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