Silicon-on-insulator by oxygen implantation: An advanced technology

Microelectronic Engineering 8 (1988) 149-161 North-Holland

149

Silicon-on-insulator by oxygen implantation: An advanced technology M. Bruel, J. Margail, C. Jaussaud, A. J. Auberton-Herv6 and J. Stoemenos* CEAI IRDI / D.LETI, Boite Postale 85X, 38041 Grenoble Cedex, France

Abstract. SIMOX has emerged as the leading SOI technology. This is due to the. excellent physical and electrical properties of this material and to the availability of industrial implanters. The formation of SIMOX structures requires two main steps: implantation and annealing. The implantation conditions determine the density of crystalline defects and high-temperature annealing allows a complete segregation of the oxygen toward the buried layer. A good control of these two steps allows to form material on which CMOS circuits of medium complexity have been produced, both with and without epitaxy. A 16 K SRAM memory has been processed on material used with an epitaxy and 29C101 CMOS processors have been fabricated.

Keywords. Silicon-on-insulator, SOI, SIMOX, ion implantation, CMOS devices.

1. Introduction Silicon-on-insulator f o r m e d by oxygen implantation ( S I M O X ) is a twentyyear old technique. E v e n t h o u g h it is difficult to accurately define a starting point, it is possible to point out some dates and events which have m a r k e d the history of S I M O X . T h e idea of forming dielectric layers by ion implantation was first prop o s e d by Smith [1] in 1956. B u t it was only in 1966 that W a t a n a b e and T o o i fabricated the first SiO2 layer by oxygen implantation at 60 k e V [2]. T h e c o n c e p t of using dielectric layers for device isolation was given by Dexter, Watelski and Picraux [3] in 1973. Four years later the first buried oxyde layer synthesized by ion implantation was reported by Badawi and A n a n d [4]. T h e year 1978 was a key one for microelectronics on silicon-on-insulator (SOI) substrates; the first electronic device, a 19-stage ring oscillator was published by Izumi et al. [5]. T h e name S I M O X was created b y Izumi for separation by *University of Thessaloniki, Thessaloniki, Greece. 0167-9317/88/$3.50 O 1988, Elsevier Science Publishers B.V. (North-Holland)

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implantation of oxygen and is now the name under which this technology is known. During the seventies extensive studies led to the formation of buried oxydes with properties very close to those of thermal oxydes (see for example [6, 7]. In 1981 Lam et al. [8] proposed to make the implantation at sufficiently high temperature, which gives rise to a self-annealing of the damage created by the implantation and thus allows the crystallinity of the upper silicon layer to be kept [8]. Since that data nearly all the SIMOX structures have been produced at high temperature by using beam heating. Between 1981 and 1985 basic studies were conducted all over the world especially on the physical characterization of the buried layer and the mechanism of its formation (see for example [-9-13]). However, most often the same temperature was unprecisely controlled and known and the implanted surface was very small due to the small available beam intensity. The year 1985 can be considered as a turning point in the history of SIMOX. During this period two major events occurred: * The first industrial oxygen implanter was fabricated as a result of a collaboration between NTT in Japan and Eaton in the U.S. A description of this implanter can be found in [14]. * The first very-high temperature annealing ( T > 1300°C) of SIMOX structures was performed at C E A / D . L E T I [15]. It demonstrates the total segregation of the oxygen towards the buried layer and the formation of SIMOX structures with an upper silicon layer completely free from SiO2 precipitates. Under these annealing conditions the Si/SiO2 interfaces are perfectly abrupt. The only defects left in these structures are threading dislocations in the upper silicon layer and silicon islands in the buried SiO2 layer. The same year Texas Instruments fabricated a 4 K SRAM on an epitaxial silicon layer grown on SIMOX [16]. During the last two years further improvements have been made on SIMOX material: very low dislocation densities (<105cm -2) in the upper silicon layer [17] and structures with both very low dislocation densities and SiO2 layers free from silicon islands [18] have been obtained. During the last two years high-complexity circuits have been fabricated both on epitaxial layers grown on SIMOX (16 K SRAM by Texas Instruments [19]) and on SIMOX material without silicon epitaxy (12000-transistor circuit by C E A / D . L E T I with 1.2 I~m design rules [10]). In this paper we discuss the formation conditions of low-defect density SIMOX structures and give some electrical results to show that they are compatible with the processing of VLSI circuits.

2. Experimental aspects There are two main steps in the fabrication of SIMOX structures: implantation and annealing. In order to obtain good-quality SIMOX structures these two steps must be carefully controlled.

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2.1. Implantation The implantation parameters having an influence on the final microstructure are: the total implanted dose, the energy, the temperature. The total implanted dose essentially determines the thickness of the SiO2 buried layer. The energy determines the depth at which the ions are implanted and so the thickness of the silicon over!ayer. The temperature is one of t h e most important factors for the final microstructure: if the implantation is done at a too low temperature, the accumulation of defects can amorphize the top silicon layer which during annealing will become polycrystalline. In order to avoid this the implantation must be done at high temperature. Because of the relatively high current densities used during the implantation of oxygen, beam heating can raise the wafer temperature to about 500°C which is sufficient to avoid amorphization. The sample can also be heated by an external source (lamps [17,21] or resistively heated wafer bearing [22]). 2.2. Annealing step The annealing conditions essentially determine the final repartition of oxygen in the SIMOX structure. If the annealing temperature is low, SiO2 precipitates are left and the Si/SiO2 interface is not abrupt. For higher temperatures (>1300°C) all the implanted oxygen segregates to the SiO2 buried layer and the Si/SiO2 interfaces are abrupt. A furnace specially designed for high, temperature annealing (HTA) of SIMOX wafers has been used at D . L E T I to anneal 100 mm wafers. It uses a polysilicon tube heated by SiC rods parallel to its axis. The maximum working temperature is 1375°C and the temperature gradient on the 200 mm long plateau is less than 2.5°C. Though no detailed measurement of the wafer distortion induced by the high-temperature anneal has been made, the many batches of circuits processed on H T A SIMOX show that no significant distortion is introduced by HTA. Contamination might also be introduced during H T A , but in practice no contamination related to it could be detected. More than two years experience in H T A of SIMOX structures allows us to conclude that this process is compatible with VLSI circuit processing.

3. Physical properties ot SIMOX stractares 3.1. Microstructure of the S I M O X samples

The general features of the as-implanted SIMOX samples microstructure are shown in Fig. l(a) (for this sample the implantation conditions were:

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M. Bruel et al. / SO1 by oxygen implantation

v , i**.l ~ t l H

t

annealed 1300 °C, 6 hours

[

annealed annealed 1185 °C, 6 hours 1150 °C, 2 hours

not annealed

Fig. I. XTEM micrographs of a sample implanted at 200 KeY, 700°C, dose 1.6 x 1[)~ O +cm 2. (a) As-implanted; (b) annealed at 1150°C, 2 hours; (c) annealed at 1185°C, 6 hours; (c) annealed at 1300°C, 6 hours.

e n e r g y 200 KeV, dose 1.6 x 10 TM O + cm z). T h r e e regions can be distinguished: a 420 nm thick top silicon layer containing a large density of SiO2 precipitates, the sizes of which increase from the surface to the Si/SiO2 interface [23, 24], a 180 n m thick SiO2 layer, and a heavily d a m a g e d silicon layer extending 450 nm into the silicon substrate. If the implantation is done at t e m p e r a t u r e s below 450°C, a zone of a m o r p h o u s silicon is f o r m e d at the Si/SiO2 interface. T h e evolution of the microstructure during annealing is shown in Figs. l(b), l(c), and l(d). It shows the progressive creation of a zone d e n u d e d of SiO2 precipitates which extends towards the buried SiO2 layer w h e n the annealing t e m p e r a t u r e is increased. A f t e r annealing at 1300°C the segregation of oxygen to the SiO2 buried layer is complete and both Si/SiO2 interfaces are abrupt. T h e only defects left are threading dislocations and silicon islands in the buried SiO2 layer. 3.2. Formation of low defect density S I M O X structures Processing VLSI circuits on S I M O X material requires it to contain a very low defect density. T w o types of defects are found in as-implanted S I M O X structures: SiO2 precipitates and crystalline defects such as dislocations and stacking faults. T h e means to r e d u c e the density of these defects or to eliminate them are quite different. While total elimination of the SiO2 precipitates and segregation of the implanted oxygen inside the SiO2 buried layer is possible by h i g h - t e m p e r a t u r e annealing, obtaining dislocation-free S I M O X is m u c h m o r e difficult and requires great care in the implantation conditions.

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3.2.1. Physical mechanism of Si02 precipitates dissolution The physical mechanism of SiO2 precipitates dissolution has been given by Stoemenos et al. [15] and described in detail by Jaussaud et al. [25]. It results from the phenomenon of coalescence. When a system containing precipitates of various sizes is annealed at high temperature, the number of precipitates decreases and their size increases: the bigger ones grow at the expense of the smaller ones. This process, known as coalescence [26], requires the dissolution of smaller precipitates and the diffusion of the solute from regions surrounding the small particles towards those surrounding bigger ones. As mentioned above, in SIMOX after implantation there is a gradient in the SiO2 precipitates sizes, which increase from the surface to the buried layer. Because of this gradient the precipitates which are closer to the surface dissolve first. And so for short-time or low-temperature annealing there is formation of a zone denuded from precipitates in the upper part of the silicon layer and growth of bigger precipitates in its lower part. This is accompanied by the migration of oxygen towards the buried layer. As the temperature or the duration of the annealing are increased, this mechanism leads to an extension of the denuded zone and formation of bigger precipitates near the buried layer. This mechanism will stop only when a single size of precipitate is present in the silicon matrix. In SIMOX there is formation, after implantation, of a continuous buried SiO2 layer. This layer acts as a precipitate of infinite radius and the coalescence mechanism leads to the complete dissolution of SiO2 precipitates and the segregation of oxygen inside this buried layer. This mechanism is thermally activated: complete dissolution of the SiO2 precipitates takes 30 minutes at 1405°C [27], and 4 hours at 1300°C [28]. 3.2.2. Dislocations 3.2.2.1. Origin. There is not a general agreement on the origin of dislocations in SIMOX structures. The dislocations observed after H T A can be formed either during the implantation or during the anneal. It has been shown [29] that the most important source of dislocations during implantation is the generation of point defects. Two sources of point defects have been identified. The first one is the defects created by the atomic collision cascade: Si ~

Sii + V,

where Sii is an interstitial silicon atom and V a vacancy. The second one is the internal oxidation of silicon. During this oxidation the formation of an SiO2 phase requires the creation of a free volume. This free volume can be created by absorption of a vacancy or by creation of an interstitial silicon atom. Consequently during the implantation a large amount of silicon interstitial atoms have to be eliminated. The only site where this elimination is possible is the silicon surface (the diffusion coefficient of Si in SiO2 is very small [30] and these atoms cannot migrate through the buried

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SiO2 layer, towards the bulk). If they cannot be eliminated they will agglomerate and lead to the formation of extended defects. The formation of dislocations during annealing has been suggested by Krause [24]. Nevertheless, it must be pointed out that SIMOX material with very low dislocation density can be formed by high-temperature annealing (1300°C), which means that annealing is not a major source of dislocations. Following the identification of the origin of these defects several methods to reduce their density in SIMOX structures have been suggested and tested [17,18,31]. 3.2.2.2. Solutions to form low defect density S I M O X structures. The conditions that allow the formation of low defect density SIMOX structures are those that lower the number of defects created during the implantation or their rate of creation and those that allow an easy migration of silicon interstitial atoms towards the surface. Based on these ideas several methods have been used to obtain low defect density SIMOX structures. Van O m m e n [17] uses implantations in a channeling direction and at a low dose rate to decrease the number of defects created and to allow the silicon interstitial atoms to migrate easily towards the surface. By this method he obtains SIMOX structures in which no defects can be revealed by TEM. Other groups [18,31] use a combination of implantation and anneal sequences. The principle of this method is the following. As mentioned above, the migration of silicon interstitial atoms is almost impossible through SiOz and the progressive accumulation of SiO2 precipitates during the implantation tends to block this migration and lead to the formation of extended defects. If these SiO2 precipitates are dissolved before they reach a too high concentration, this blocking does not occur and the density of dislocations is reduced. This is what happens when the SIMOX structure is formed by a series of implantation and anneal steps. Another interesting feature of SIMOX layers formed by this method is the absence of silicon islands in the buried SiO2 layer (Fig. 2). The reason why no

sul 500

nm

t s i : 170 nm

ts|o~: 3 8 0 nm

Fig. 2. XTEM micrograph of a sample implanted in 2 stages: implantation of 0.8 × 10TM O÷ cm 2 at 200 KeV, 600°C, annealing at 1300°C, 6 hours, second implantation of 0.8 x 10'80 +cm-2 at 200 KeV, 600°C, and second annealing at 1300°C, 6 hours. No dislocation could be found in this sample by planar TEM. Note also the absence of silicon islands in the buried SiO~ layer.

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silicon islands are found inside the SiO2 buried layer can be explained as follows: - The first implantation and anneal step creates an SiO2 buried layer which contains a large density of silicon islands [32]. - During the second implantation step, the impinging oxygen ions can oxidize these silicon islands. No extra silicon islands are formed near the lower Si/SiO2 interface because the implanted dose reaching this region is too low to form a banded structure (mixture of silicon and elongated SiO2 precipitates). It has been shown that it is the evolution of this banded structure during high-temperature annealing which leads to the formation of a chain of silicon islands [21]. A third method has been used by other authors [33]: they use implantation conditions under which cavities are formed in the silicon overlayer. These cavities act as a sink for the silicon interstitial atoms and allow them to be eliminated. T E M characterization of samples produced by these three methods indicates that they can produce SIMOX material with defect densities lower than the detection limit of this technique: 105 cm -2. The first method does not seem to be feasible on an industrial scale because it uses a low current density and implantation in a channeling direction. The second one causes no particular problem in an industrial context, but the complexity of the process is increased and the material cost will be increased. The third one requires implantation conditions that seem to be strict. But in practice these conditons are met on the industrial implanter available today. Detailed examination of samples implanted on an Eaton NV 200 machine have shown that in the as-implanted state the silicon overlayer contains small cavities. After annealing at 1300°C the samples contain a very small dislocation density [25]. Though we do not have at present enough results to be sure that this kind of material will be obtained reproducibly, this result indicates that the conditions required to form dislocation-free SIMOX structures can be met in an industrial context. The most directly applicable method is the third one. But the characterization method used (TEM) is not sensitive enough to allow the measurements of dislocation densities that one should like to achieve for VLSI substrate (10cm-2). Consequently more detailed studies will be necessary before knowing if the other two methods are of interest.

4. Electrical

properties

of SIMOX

structures

4.1. H a l l mobility The variation of the Hall mobility as a function of temperature [34] is given in Fig. 3 for a SIMOX sample annealed at 1300°C for 6 hours in an argon atmosphere. The maximum mobility (1800cmE/V/S) is obtained at a tern-

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2000 SIMOX 1500

~E 1000

700 ,.J _J

I

500

IT(K)

100

200

Fig. 3. Hall mobility versus temperature for a typical SIMOX sample annealed at 1300°C for 6 hours in an argon atmosphere.

perature of 100K and the general temperature behaviour of this mobility corresponds to that of bulk silicon. When the anneal is performed under nitrogen the mobility is lower and the maximum occurs at 180K. This difference has been attributed to the doping introduced by nitrogen in the SIMOX structure during the annealing [34]. 4.2. Devices MOS transistors have been fabricated on SIMOX material produced by implanting a dose of 1.6 × 10 TM O + cm -2 at 200 KeV in a substrate kept at a 2000

1500

channel~ o~

. ~E

1000

=>,

800

'R o E

700

r-

e

_¢ IJJ

50

2O

600

\5

500 4O0

3OO

250

T-l.ls 80 100 200 250 I

I

10

1

I

300

250

Temperature (K) Fig. 4. Electron mobility versus temperature for front- and back-inversion channels in SIMOX MO S F E Ts after annealing at 1340°C. The dotted curve shows with a modified scale the back channel mobility curve obtained by low-temperature annealing (1150°C).

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constant temperature of 600°C and annealed at 1300°C for 6 hours in an argon atmosphere [20]. The channel electron mobilities measured on similar devices processed on material annealed at 1340°C are shown in Fig. 4 and compared for the lower interface to those obtained on transistors processed on lowtemperature annealed (LTA) SIMOX material [34]. For H T A the temperature behaviour of the back interface is very similar to that of the front interface, dominated as in bulk silicon by carrier scattering on lattice vibrations. On the contrary, in L T A SIMOX this behaviour is completely different indicating a poor-quality material. In H T A material the back channel interface state density is 8 x 1011/cm2/eV and the field oxide charge density is 2 x1011/cm2 in the underlaying oxide. The threshold voltage dispersion is only 4.2% (at 3 sigma) higher than that of the corresponding bulk NMOS transistors and 10% for the PMOS. Short-channel effects appear only for channel length less than 0.6 Ixm for both N and PMOS transistors.

4.3. Circuits 4.3.1. Applicability of SIMOX for VLSI circuits Very advanced devices as well as large complex circuits have been achieved on SOI substrates made by oxygen implantation. The most significant

Number of transistors 10 s e-m

Xk J 10 4

i

•

h

Xg

X 103

f

X

d

• 10 2

c

x

I

A

0.1

b

a

1

10 Channel length (p.m)

Fig. 5. Complexity of the most significant CMOS circuits processed on SOI substrates versus channel length. (a) Tsaur [35]; (b) Omura [36]; (c) Colinge [37]; (d) Haond [38]; (e) Chen [19]; (f) Inoue [39]; (g) Sakashita [40]; (h) Izumi [41]; (i) Auberton-Herv6 [20]; (j) Chen [16]; (k) Yamazaki [43].

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ones, represented in Fig. 5, are characterized by their feature size (gate length on the X-axis, complexity (number of transistors) on the Y-axis), and nature of the substrate (SIMOX or recrystallized polysilicon). This diagram shows that more complex circuits have been processed on SIMOX than on recrystallized material. This is due to the advantages of SIMOX over other SOl materials: * SIMOX is naturally a full-sheet technology and no constraint due to seeds or defective areas is imposed. The designer is free to make a complete new design that will take full advantages of the SOl substrate or to use a circuit already designed for bulk silicon, with only minor modifications such as input/output protections. * The SIMOX technology has improved very significantly and can now yield a material with very low defect density. * The material is now commercially available. Consequently, with SIMOX, the natural advantages of SO1 (much shorter N*/P ÷ spacing, no well, no bulk or well contacts) have become directly available to semiconductor industrial companies. The largest circuits were achieved on SIMOX substrates on top of which an epitaxial layer was grown. This is due to the fact that before the introduction of high-temperature annealing (1985) the silicon overlayer was very defective and epitaxy was required to reduce the defect density. Today the availability of high-quality silicon overlayer makes it unnecessary to use an epitaxial layer for advanced CMOS circuits.

4.3.2. CMOS/SIMOX technology developed at C E A / D . L E T I The technology developed at C E A / D . L E T I is based on the use of highquality thin-film SIMOX substrates obtained by HTA. Not only no additional epitaxy is used, but on the contrary a thinning of the layer is used to get the optimum thickness, which is around 180 nm. The main characteristics of the process are: * N channel transistors: E n h a n c e m e n t type with LDD junctions. * P channel transistors: Compensated type. * Polycide gate (TaSi2/N ÷ polysilicon). * LOCOS structure for lateral isolation. * Gate oxide thickness: 25 nm. * Silicon film thickness: 180 nm. * Buried oxide thickness: 380 nm. * E f t e c t i v e channel length: 1 ~m. A schematic cross-section of the transistors is shown in Fig. 6. Medium-complexity circuits were achieved at C E A / D . L E T I with the technology described above. For example 28C101 CMOS processors specially designed for SOI substrates by C E A / D A M were fabricated to prove the feasibility of our technology and the capability of using directly the thin-film

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Fig. 6. Schematic cross-section of N and P transistors processed on SIMOX at D.LETI.

SOI substrate. T h e circuit complexity is about 10,000 transistors. Maximum clock frequency of 30 MHz was obtained.

5. Conclusion T h e SIMOX formation mechanisms are now better understood and formation conditions can now be defined that lead to a SIMOX material with very low defect densities. T h e mechanism of SiO~ precipitate dissolution by H T A is now well established and e n o u g h experience has been accumulated to say that this process is compatible with VLSI circuit technology T h e mechanisms leading to low dislocation density SIMOX structures are not so well established but the basic ideas have been given and SIMOX material with very low defect densities has been produced by various techniques. One of them is applicable to material produced on industrial implanters and one can reasonably think that dislocation-free SIMOX will soon be available. The feasibility of complex circuits has been demonstrated both on low-temperature annealed material associated with the growth of an epitaxial layer and on high-temperature annealed material without epitaxy.

References [1] M. L. Smith, Electromagnetically Enriched Isotopes and Mass Spectroscopy (Butterworth, London, 1956) 100. [2] M. Watanabe and A. Tooi, Formation of SiO2 films by oxygen-ion bombardment, J. Appl. Phys. 5 (1966) 737.

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[3] R. J. Dexter, S. B. Watelski and S. T. Picraux, Epitaxiai silicon layers growth on ion-implanted silicon nitride layers, Appl. Phys. Lett. 23 (1973) 455. [4] M. H. Badawi and K. V. Anand, A study of oxygen oxides prepared by oxygen implantation into silicon, J. Phys. I)10 (1977) 1931. [5] K. Izumi, M. Doken and H. Ariyoshi, CMOS devices fabricated on buried SiO2 layers by oxygen implantation into silicon, Electron. Lett. 14(18) (1978) 594. [6] J. Dylewski and M. C. Joshi, Formation of thin SiO: films by high dose oxygen implantation into silicon and their investigation by IR techniques, Thin Solid Films 35 (1976) 327. [7] K. I. Kirov, E. D. Atanova, S. P. Alexandrova, B. G. Amov and A. E. Diakov, Properties of SiO2 films formed by oxygen implantation into silicon, Thin Solid Films 48 (1978) 187. [8] H. W. Lam, R. F. Pinizotto, H. T. Yuan and D. W. Belavance, Characteristics of MOSFETS fabricated in silicon-on-insulator material formed by high-dose oxygen ion implantation, Electron. Lett. 17 (1981) 356. [9] P. L. F. Hemment, E. Maydell-Ondrush, K. G. Stephens, J. Butcher, D. loannou and J. Aldermann, Formation of buried insulating layers in silicon by the implantation of high doses of oxygen, Nucl. Inst. Meth. 209/210 (1983) 157. [10] H. W. Lam and R. F. Pinizzotto, Silicon-on-insulator by oxygen ion implantation, J. Crystal Growth 63 (1983) 554. [11] S. R. Wilson and D. Fathy, Characterization of buried SiO2 layers formed by ion implantation of oxygen, J. Elec. Mat. 13 (1984) 127. [12] C. G. Tuppen, M. R. Taylor, P. L. F. Hemment and R. P. Arrowsmith, Effects of implantation temperature on the properties of buried oxide layers formed by oxygen ion implantation, Appl. Phys. Lett. 45 (1984) 57. [ 13] S. S. Gill and I. H. Wilson, Formation of oxide layers by high dose implantation into silicon, Mater. Res. Soc. Proc. 27 (1984) 275. [14] J. P. Rutiel, D. H. Douglas-Hamilton, R. E. Kaim and K. Izumi, A high current, high voltage oxygen ion implanter, Nucl. Inst. Meth. B21 (1987) 229. [15] J. Stoemenos, C. Jaussaud, M. Bruel and J. Margail, New conditions for synthesizing SO1 structures by high dose oxygen implantation, J. Crystal Growth 73 (1985) 546. [16] C. E. Chen, T. G. Blake, L. R. Hite, S. D. S. Malhi, B. Y. Mao and H. W. Lam, S O I - C M O S 4K S R A M with high dose oxygen implanted substrate, IEDM Technical Digest (1984) 702. [17] A. H. Van Ommen, Structural studies of the formation of a buried oxide layer by oxygen implantation, in: A. G. Cullis and P. Augustus, eds., Microscopy of Semiconducting Materials, Institute of Physics Conference Series 87, Oxford (1987) 385. [18] J. Margail, J. Stoemenos, C. Jaussaud and M. Bruel, A new method for making improved SO1 structures, European SO1 Workshop, Grenoble, 1988. [19] C. E. Chen, M. Matloubian, B. Y. Mao, R. Sundaresan, C. Slawinski, H. W. Lam, T. G. Blake, L. R. Hite and R. K. Hester, A 1.25 p,m buried oxide SOI/CMOS process for 16K/64 SRAMS, IEEE Trans. Electron. Dev. ED-33 (1986) 1840. [20] A. J. Auberton-Herv6, M. Bruel, C. Jaussaud, J. Margail, W. D'Hespei, J. F. Pere, A. Vitez and A. Tissot, A CMOS-SOI 1.4/xm technology on 1300°C annealed SIMOX substrates without epitaxy, in: Proceedings 1988 Symposium on VLSI technology, San Diego, C A (1988). [21] M. Bruel, C. Jaussaud, J. Margail and J. Stoemenos, High temperature annealing of SIMOX layers, in: G. Bentini, ed., Dielectric Layers in Semiconductors: Novel Technologies and Devices, Proceedings European Material Research Society, Strasbourg (1986) 105. [22] O. W. Holland, T. P. Sjoreen, D. Fathy and J. Narayan, Influence of substrate temperature on the formation of buried oxide and surface crystallinity during high dose oxygen implantation into silicon, Appl. Phys. Lett. 45 (1984) 1081. [23] J. Stoemenos and J. Margail, Nucleation and growth of oxide precipitates in silicon implanted with oxygen, Thin Solid Films 135 (1986) 115.

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