Chemical vapor deposition in the systems silicon-carbon and silicon-carbon-nitrogen

Journal of fhe Le.ss-Cormon Metals, 37 ( 1974) 317.-329 I’ Elsevier Sequoia S.A.. Lausanne Printed in The Netherlands

CHEMICAL VAPOR DEPOSITION AND SILICON-CARBON-NITROGEN*

JULIUS

J. NICKL

and CHRISTINE

IN THE

317

SYSTEMS

VON BRAUNMfrHL

Forschur~~sluhoratorium fiir Frstkiirprrclwmie urn Institut ,ftir Arwy)unischr Miirdwr~, Miincherr (Bundesrepuhlik Deutschlnd) (Received

February

SILICON-CARBON

Chmie**

der Unirersitiit

19. 1974)

SUMMARY

This report relates to the chemical vapor deposition and morphology of the systems Si + P-Sic, Si + SiJN,, and Si + /?-Sic + Si,N,, which were produced from the following mixtures at temperatures ranging from 1100 to 1300’C: SiC14 + Ccl, + Hz, SiCl, + N2 + Hz, and SiC14 + Ccl, + N, + HZ. The solid phases form an unoriented, extremely fine-grained but dense mixture. These solid phases do not reveal any coherent or semicoherent intergrowth. The unoriented growth is a consequence of the permanent carbidization or nitridation of the free silicon surface and covering of the resultant crystals of silicon carbide and/or silicon nitride. At < 1200’C Si,N4 becomes amorphous and at 3 1300°C a-Si,N, is deposited in addition. In the neighbourhood of 13OOC /$Si,N, formation cannot be excluded with certainty. As the Ccl4 concentration in the vapor phase increases. the nitridation IS suppressed by the carbidization. ZUSAMMENFASSUNG

Es wird iiber die Gasphasenabscheidung und Morphologie der Systeme Si+B-Sic. Si + Si3N4 und Si+p-Sic + Si3N4 berichtet, die mit den folgenden Gasgemischen abgeschieden wurden: SiC14 +CCl, + HZ, SiC14 + Nz + H2 und SiCL, + Ccl4 + Nz + Hz. Die festen Phasen bilden ein unorientiertes. extrem feinteiliges jedoch dichtes Gemenge das keine koharente oder semikoharente Verwachsung erkennen lasst. Das unorientierte Wachstum ist eine Folge der permanenten Carbidierung bzw. Nitridierung der Oberfllche des freien Siliciums und Abdeckung der gebildeten Sic-Kristalle bzw. SiJN4-Breiche. Bei < 12OO’C wird Si3N4 rontgenamorph und bei 2 1300°C zusatzlich als M-Si3NS abgeschieden. Im Bereich von 1300°C kann /%Si3N4 nicht mit Sicherheit ausgeschlossen werden. Bei steigendem CC14-Gehalt in der Gasphase wird die Nitridierung zurtickgedrangt.

* Presented in part at the “Second May 21-25. 1972. Jerusalem, Israel. ** Lehrstuhl Prof. Dr. Armin Weiss.

International

Conference

on Vapor

Growth

and

Epitaxy”.

318

J. J. NICKL,

C. VON BRAUNMtiHL

1. INTRODUCTION

This report is concerned with the heterogeneous phase systems: Si+ P-Sic (I), Si3N4 (II) and Si + B-Sic + Si3N4 (III), prepared by chemical vapor deposition. The previous investigation with the reaction mixture Si +

SiCl,(g) + CClb( g) + H2,ex has shown that the product in System I is deposited as a dense and very linegrained structure. It may be assumed that this kind of structure is due to silicon carbide being formed by carbidization of the silicon surface’. This assumption is supported by investigation of the crystal structure and morphology. These investigations seemed to indicate that the work should be extended to include Systems II and III in order to establish that the tine-grained structure is an inherent property not restricted to System I. 2. EXPERIMENTAL

2.1. Conditions of deposition In order to be able to compare the present with the former results the same TABLE

I

CONDITIONS

OF DEPOSITION*

(a) Constant conditions P total pressure F substrate surface (see also ref. 1) of tetrachloride NT throughput No

( = nsicu or nsici4 + nccu) throughput of gases (Hf+Ar) or (HZ+N2)

715 k 15 Torr. w 56 cm’. 0.22 + 0.03 mole h- i

3001 h-i.

(b) Variable conditions Xi,g mole fraction of the components in the reaction mixture (see (c)**) Gg = nsici4/(nsici4 + kc,,) xc,, = 1 - xsi,, XA~.~ = nk/(u,k + au) XN.8 =nN/(nN fan) &I,, =l-XA,,, or(=l-&.s) substrate temperature Ts (c) Reaction I. SiCL(g) 2. SiCl,(g) 3. SiCl,(g) 4. Sir&(g) 5. SiClh(g)

0.5 < xsi,B < 1.0 o< xc,,< 0.5. O< XAl.s < 0.67. o< XQ < 0.83. lloo”<

G<

1300°C.

mixtures and deposited systems +Si( s) + p-SiC( s) +CCL(g) +H2(g) +CCl,(g) + H,(g) + Ar(g) -+Si(s) +/I-Sic(s) +Si(s)+SiJNb(s) + H,(g) + N,(g) +CCl,(g) + H,(g) + N,(g) +Si(s) + b-Sic(s) +Si(s) (IV) + HZ(g) + Ar(g)

The deposition rates of the components or compounds deposition rate by Rx (g h-l) (see Table II).

(I) (I) (II) +SiaNb(s)

are determined

(III)

by RI (mmole

* For abbreviations, see ref. 1. * For this investigation only those reaction mixtures are of interest which addition to Sic and/or Si,N,. i.e., SiCl, in a relatively high concentration.

l

h-i)

produce

and the total

free silicon

in

CHEMICAL VAPOR DEPOSITION IN THE Si-C AND Si-C-N SYSTEMS

319

deposition apparatus was used, with directly-heated graphite rods as substrates’. The same applies to the constant conditions (see Table I) and to the purity of the Si&. Ccl4 and HZ. High-purity nitrogen (99.997: min.) and high-purity argon (99.997; min.) were used. 2.2. Phase analysis Silicon &ride was estimated indirectly from the nitrogen content in the deposition products. For this purpose the pulverized deposition product was fused with LiOH and the ammonia liberated was determined titrimetrically*; boron nitride (BN) was used as a reference compound (relative error & 27Q. Silicon carbide was weighed as a residue after the dissolution of the free silicon (System I) and silicon nitride (System III). For this dissolution, a nitric acid-hydrofluoric acid mixture* was used in diluted or undiluted form. The dissolution was carried out until a constant weight was attained, in order to insure complete removal of the silicon nitride. Free silicor~ was determined from the loss in weight after dissolution with the above-mentioned acid mixture. In addition, free silicon and silicon carbide were identified by a Guinier X-ray technique. With reference to the difficulties arising in connection with silicon nitride, which primarily existed in the amorphous form, see Sections 3.2 and 3.3. The morphology was further investigated by means of a scanning etectron microscope (Figs. l-3,5,6). For this purpose the specimens were etched slightly with CP4** (ref. 3) and coated with a thin film of gold. 3. RESULTS AND DISCUSSION

of Si+/?-Sic 3.1.1 Structure and morphology

3.1 Deposition

Both phases are deposited as a dense and fine-grained mixture. Silicon carbide is formed in thin and small layers and is irregular within the silicon matrix. The figures show this result in more detail. Figure l(a) shows the fracture surface of a deposition layer (-0.4 mm) consisting of free silicon (Si) and 8.86 wt.% /&Sic coating a graphite rod (diam.= 3 mm). This layer was deposited from the reaction mixture SiC14+CC14(Xc.,=0.1)+H2 over four hours at 1200°C (Table II, No. 2). Figure l(b) shows the slightly-etched deposition surface (marked with x in Fig. l(a)). A silicon grain with a silicon carbide coating can be recognized. The enveloping carbide layer shows a hole, probably due to the etching of silicon. This form of deposition reveals that silicon carbide is formed on the silicon grains. Furthermore, it is obvious that the coating of silicon carbide inhibits and blocks the growth of silicon crystals to a great extent. If the inhibition of free silicon is reduced, e.g., by less carbon supply, the silicon crystals achieve a larger volume * 1 part HN03 (50 wt.“;,)+ t part HF (40 wt.?,) t* 3 partsCP4+ f part HzO.

II

116 112 93 113 Ex 110 111 32 82 II 78 19 16 65

1 2 3 4 5 6 I 8 9 10 11 12 13 14

1100 1200 1300 1200 1200 1200 1200 1300 1300 1300 1300 1300 1300 1300

0.47 0.47 0.47 0.47 0.17 0.33

1 1 0.73 1 0.67 0.67 0.67

XH.57

XSi.,

0.99 0.90 0.95 1 1 1 0.90 1 1 1 0.95 0.83 0.95 0.50

qf

Corlditiorls deposirion

(7sC,

0.53

0.33

0.67

X,4,.,

0.53 0.53 0.53 0.83 0.67

0.33 0.33

XNN.g

* For constant conditions see Table I( a) ** Free carbon is not deposited; &. free =0 and Rsir = &. *** Silicon carbide was formed as very fine particles and therefore the Guinier pattern. CI-,/J-Si3N4 found by X-ray powder diffraction.

Esperiment no.

No.

EXPERIMENTS*

TABLE

< 0.5 3.3 3.8

251 48.8 21.3 68.4 62 46.0 33.8 61.0 37.1 26.5 26.2 2.4

as a residue

0.8 11.2 6.4 24.4

2.0

SIC

Si (.free)

could not be found

-51.5 52.1 25.1 68.4 62 49.2 37.8 61.0 37.1 29.6 29.0 14.6 7.4 26.6

ZSi

Ri (mmole h-l)**

after

dissolution.

1.0 0.70 - 0.32 0.32 0.62

1.08 -0.4

Si3N4

15 8.6

the value

-8

16.4 11.3

10.5 -5

f wt.“,)

Forms

a. W) (0

z

x B

2. 5 r. 6

1 3

2***

(Figs.)

SiaN4,

of Rsic was estimated

1.44 1.50 0.75 1.92 1.74 1.44 1.08 1.70 1.04 0.89 0.86 0.56 0.30 1.01

RZ fg h-‘)

Si3N4

from

qf

321

Fig. 1. Micrograph of deposit containing free silicon and about 9 wt.?,, of silicon carbide (P-Sic). The system was deposited on a graphite rod (0 3 mm) by the gas mixture Sitl,+CCI, (Xc,, =O.lO) +H, over four hours at 12OO’C (see Table II, No. 2). (a) Surface of fracture. ground surface and surface of deposit (x IOO). (b) Surface of deposit ( xZO@O, marked with x in Fig. l(a)). (c) Change of deposition by decreasing carbidi~tion for about three minutes ( x2000). (d) x lO.OO@.(e) marked with a square in Fig. I(a).

322

J. J. NICKL,

C. VON BRAUNMHL

in the reaction product. This situation is apparent in Fig. l(c) (magnification x 2000): the deposition zone* which was produced by a reduced carbon supply for approx. three minutes (Xcs< 0.1) contains larger silicon crystals than the areas to the left and right of the zone. The area in question is marked with a circle in Fig. l(b). A deposition region with an uninterrupted CCL supply during a limited period of time (Xc., = 0.1) is shown in Fig. l(d) at a magnification of x 2000 and in Fig. l(e) at a magnification of approx. x 10,000; the corresponding area is framed by a square in Fig. l(a). Both Fig. l(d) and l(e) show the irregular SIC layers of thickness 500-2000 A. There seems to be a justification for the assumption that the growth of Si crystals ends after approx. l&40 s at a volume of 0.5-5 ,um3**. The coating of silicon grains can be observed distinctly at a relatively low carbon supply (XcB< 0.05) and low deposition temperatures ( Ts = 1100°C: see Table II, No. l), as is shown in Fig. 2. In the center of Fig. 2(a) an etched silicon crystal can be recognized, which is covered on its base by an Sic layer. The separation of three silicon grains by Sic layers is illustrated in Fig. 2(b). At a high carbon concentration (Xc,, >O.l) and/or at high temperatures ( > 1200°C) the growth of thick layers or ribbons of silicon carbide ( >2000 A) is observed (Fig. 2). 3.1.2 Deposition model The unoriented form of silicon carbide in the matrix of free silicon can be explained as shown in Fig. 4. The reduction of SiCL under the specified conditions of temperature, pressure, and concentrations according to SiCL(g) +Hz(g) = Si(s) +4HCl(g)

(1)

causes the deposited silicon to grow on the graphite substrate [l] in the form of randomly oriented crystals [2] (Fig. 4(a)). If SiCl, is partly replaced by Ccl, in reaction (1) (0 < Xc D< 0.5), the reduction of Ccl4 also takes place according to CCL(g) +4Hz(g) = CHb(g) +4HCl(g).

(2)

This reduction is almost complete, as is indicated by the log K, values: log Kp1400 = 16.0 and log Kpi6,,,, = 14.3 (ref. 4). It may be assumed that a chemisorption of methane takes place on the active zones which are continuously formed on the Si surface. The methane can then react with silicon to form silicon carbide with the evolution of hydrogen: Si(s) +CH4(g) = /?-Sic(s) +2Hz(g);

AG1600 = - 35.1 kcal (ref. 4)

(3) This kind of SIC formationsP7 must result in a lateral habit of silicon carbide because the subsequent covering with silicon does not allow the formation of silicon carbide grains with a smaller surface area. This mode of deposition is shown in Fig. 4(b). The live silicon crystals first formed (Fig. 4(a)) are partly carbidized on their surface, i.e., partly covered by S-Sic [4] (see Figs. 1(b) and (c) and especially * Extending diagonally from the top left-hand side to the bottom right-hand side. ** A linear velocity of crystal growth (0.4 mm/4 h--280 A s-l) of the layer is assumed.

CHEMICAL

VAPOR

DEPOSITION

IN THE Si-C AND Si-C-N

SYSTEMS

323

Fig. 2. Etched deposit containing free silicon and 1 wt.:,, silicon carbide (/?-SK’). The system was deposited by the gas mixture SKI4 (Xc,, = 0.01) + Hz at 1 100 ‘C (see Table II. No, 1). (a) Surface of fracture ( x 6200). (b) Surface of deposit ( x 11,400).

2(b)). The continuous reduction of silicon tetrachloride, eqn. (l), causes the deposition of new crystals 131, which are caught up by the carbidi~tion and blocked in their growth. If the silicon -grains are etched deeply enough, the original Sic layers

324

J. J. NICKL,

C. VON BRAUHWHL

1 Fig. 3. Etched carbide (P-Sic).

surface of fracture of a deposit containing free silicon For deposition see Table II, No. 3. ( x 11.500)

and

about

20 wt.%

silicon

Fig. 4. Schematic representation of inhibition of crystal growth at silicon and silicon carbide (silicon nitride). The figures show a section perpendicular to the surface of the substrate (1). (a) Growing crystals of silicon (2) on the substrate (1). (b) Partial carbidization (P-Sic) or nitridation (Si,N,) (4) and simultaneous deposition of silicon (3). (c) Layers of silicon carbide or silicon nitride after the dissolution of free silicon (see Figs. l-5).

(Fig. 4(c)) remain as a framework, revealing the front of the silicon crystal growth (cf. also Figs. l-3). 3.1.3. Comparison with similar systems The unoriented deposition of silicon and silicon carbide invites a comparison with other systems also based on SiC14 and CC14. In this connection the simultaneous deposition of TisSiCz and TIC by means of the reaction SiCL(g) +CCl,(g)+TiClk(g)+H,,

ex

is of interest. The essential observation is that both phases (Ti3SiCz +TiC) grow together as lamellae. They are oriented vertically on the substrate surface and the different lamellae are intergrown coherently, but in a few cases also simi-coherently (Table III). This uninterrupted and uni-directional deposition was explained by the diffusion ofthe components (Ti, Si, C) and their sub-compounds in the surface layer’. Thus, we have found that the simultaneous deposition of two phases can take place either with or almost without considerable inhibition of reciprocal growth. Table III shows some examples of both possibilities. It is remarkable that /&Sic does not intergrow coherently or semicoherently with phases which are simultaneously deposited (Table III Nos. 2, 5, 7, 8).

CHEMICAL TABLE

VAPOR

DEPOSITION

IN THE Si-C AND Si-C

325

N SYSTEMS

III

EXAMPLES

OF SIMULTANEOUS

DEPOSITION

OF TWO

OR MORE

SOLID

PHASES

No.

1* ?*

Ti3SiC2( = T,)+TiC r, + TiC + /&Sic

[loo]~,~[lTO]:(OO1)l.,~~(lll)TIc (T, +TiC) as no. I; no oriented intergrowth with /j-Sic. which forms relatively large polycrystalline aggregates.

3* 4* 5* fJ**

Ti5Si3C, ( = Tz)+ T, T, + TiSi2 r1 + TiSiz + B-Sic graphite (Gr) +TiC

wlT,,l/[~m, ; ( lol)T,ii(~~)TI

It 8’

P-Sic + Si /&Sic + graphite

K-lamina

oriented

embedded in TiSi2 single crystals see no. 2 lamellar texture or [OOlbr// [001)c;J/1111)TiC, [I 10ITic with (OO1)G,~/( I II )T,C;graphite controls the growth of TiC unoriented intergrowth presumably lamellar texture

(T, +TiSi2) as no. 4

* Reaction mixture SiCla(g) + CCld(g) +TiCla(g) + HJ, ex. * Reaction mixture Tic],(g) +CCl,(g) + H2 el;. *** Nos. l-5 see ref. 8; No. 6 see ref. 9; Nos. 7 and 8 see ref. 1. ’ Reaction mixture Sic&(g) + Ccl,(g) + H,,,. l

whereas coherent

titanium-containing compounds (TIC, Ti$iCz, TiSSiJCx, TiSiz) prefer intergrowth (Table III, Nos. l-5). It may be that there is in the system Si-C-Cl-H no surface layer in which the components have sufftcient mobility to reach a phase separation by means of the diffusion of the components. This would be understandable because the sub-compounds SiClz and C,H, are extremely volatile. In the case of SiiCTi-Cl-H the subcompounds TiClz and TiCl are, however, not volatile and therefore they can produce a quasi-liquid deposited boundary layer in which the components Si and C have sufficient mobility. This interpretation corresponds to the separation of phases including SIC. However, this does not explain why, in Systems 2 and 5 (Table III), P-Sic is completely separated, but does not grow in an oriented manner in the titanium-containing phases. Extending the discussion to include reaction mixtures which supply pure /?-Sic (mixture 1 in Table I with Xc.g- 0.5). one can state that there must be sufficient mobility of the components because part of the Sic-crystals grow separately and have wellformed surfaces with low indices”iO. Moreover. in the case of halogen-free reaction mixtures such as SiH4 + C3He, the components must be assumed to possess sufficient mobility because this system allows single, crystalline layers to be formed at 3 1600°C’ ‘. Finally, we even think it probable that the mobility of the components is sufficient for a phase separation, if Si+p-Sic is deposited (see above). In the present case, however, the mobility of the components is too small as compared with the continuous Si deposition. This is the reason why Sic, which has just been formed. is covered by free silicon and thus a phase separation into crystals of silicon and silicon carbide with parallel growth is prevented.

326

J. J. NICKL,

C. VON BRAUNMtjHL

3.2 Deposition of Si+Si3N4 3.2.1 Morphology and structure

The deposition was produced by means of the mixture SiCl,+(H,+N,). If nitrogen is used instead of carbon, a structure similar to that of Si+p-Sic can be expected because the nitrogen can inhibit the growth of Si crystallites by superficial nitridation, forming silicon nitride: 3Si(s)+2Nz(g)

= Si,N,(s);

G,,,,

= -83.0 kca14.

(4

Conversely, the deposition of free silicon inhibits the growth of silicon nitride. The

Fig. 5. Etched deposit containing free silicon and 10.5 wt.% silicon nitride (Si,N,). For deposition conditions see Table II. No. 6. (a) Surface of fracture perpendicular to the substrate surface ( x 2200). (b) Detail from Fig. 5(a) framed with a square ( x 11,000). (c) Surface of deposit ( x 9000).

CHEMICAL

VAPOR

DEPOSITION

IN THE SiGC AND SikC-N SYSTEMS

327

experimental results correspond to our assumption. Figure 5(a) and (b) shows the etched fracture of a deposit containing free silicon and 10.5 wt.% of amorphous silicon nitride (Table II, No. 6) which was deposited at 1200°C and 100 lN, h-l. Both figures show that the deposition is completely unoriented. This is the consequence of the crystallites (see Fig. 5(b)) being enveloped by Si,N, and the continuous process of covering of the Si,N, by free silicon. In the presence of nitrogen, the silicon crystallites grow on the deposition surface, preferably in a stalky shape as shown in Fig. 5(c). They are enveloped by Si3N4 and, in Fig. 5(b), can be recognized as broken tubes which have been etched. The structure corresponds substantially to that of Si+b-Sic. and it should be noted that some individual silicon crystallites grow to form larger agglomerates before they are completely inhibited in their growth (Fig. 5(a), left). The deposition model discussed in 3.1.2 can be applied in the same sense to the nitridation (Fig. 4). Unlike carbidization, nitridation is less effective. Even if 537; of the hydrogen is replaced by nitrogen (X, =0.53; Table II, No. 10) only one tenth of the total deposited silicon is nitridated. This is due to the fact that at 1300°C nitrogen is relatively inactive*. Due to the envelopment of the silicon crystallites, a continuous nucleation of silicon on the Si,N4 is necessary. A fall in the silicon deposition rates (R,si) can be expected for this reason. Rzsi decreases at 1200°C due to nitridation by approx. 20”/, (Table II, Nos. 5, 6) as compared to deposition in H2 + Ar (X,, = 0.33). It falls by the same percentage at 1300°C and at higher concentrations of nitrogen (X, =0.53; Table II, Nos. 9, 10). Comparable values of R,i in pure hydrogen are shown in Nos. 4 or 8, with 68.4 and 61.0 mmole h- ‘, respectively. 3.2.2 X-Ray investigations Whilst carbidization always results in crystalline silicon carbide (/?-Sic) showing sharp X-ray diffraction lines, nitridation leads to amorphous silicon nitride. At low temperatures (< 12OOC) silicon nitride could only be identified as c+Si3N4 by means of the Guinier method after the free silicon had been etched off. When the temperature (2 1300°C) and the concentration of nitrogen in the gas phase (X, 20.6) are increased, the amorphous character of Si3N4 is decreased. It can be identified as c+Si3N4 in the unetched deposition product by the above-mentioned method. In some deposits produced at 1300°C some diffraction lines are observed which may be attributed to b-Si3N4. The observation that Si3N4 appears chiefly in the amorphous state at temperatures d 1200°C corresponds with numerous investigations on the vapor deposition of insulating layers consisting of amorphous silicon nitride in the production of semiconductor devices*2P14. 3.3 Deposition qf Si+SiC +Si3N4 This deposition was effected by means of the mixture SiC14(g)+CCL(g)+(H2+N2). *

ForN2=2Nat1600KislogKp=-16.

328

J. J.

NICKL,

C. VON BRAUNMUHL

Simultaneously with the deposition of free silicon, the carbidization and nitridation of the silicon may be assumed to take place. Therefore, no essential difference in the morphology of the deposition products can be expected. This is confirmed by Fig. 6. The layers which inhibit the growth of the silicon crystallites consist mainly of line, crystalline silicon carbide (-83 mole%) and amorphous silicon nitride. The fact that carbidization suppresses nitridation is of great importance. For instance, the concentration of Si,N, in the deposition product drops by 5 wt.% if 5 mole% Ccl, are added to the SiCl,+H,+N, mixture, the other conditions remaining constant (Xsi,, = 0.95; see Section 2.1) as shown by Table II, Nos. 10 and 11. When the Ccl4 concentration had risen to Xcp =0.17, Xsi.B=0.83, the concentration of nitrogen had dropped to 8 wt.% (cJ No. 12 in Table II and also Nos. 12 and 13). If the ratio of Si: C is 1: 1 (Xc,, =OS) and the concentration of nitrogen amounts to 75% (X, = 0.75) the mole ratio C : N in the deposition product was approx. 13 : 1 (Table II, No. 14). This inhibition of nitridation is a consequence of the low reactivity of nitrogen as compared with that of carbon.

Fig. 6. Etched surface of ground deposit containing free silicon, 7.4 wt.% silicon carbide (B-Sic) about 5 wt.% silicon nitride (cf. Table II, No. 7) at a magnification of 2000 (a) and 20,000 (b).

and

In the three-phase deposition mixture the major portion of silicon nitride appears to be amorphous; a-Si,N, can only be identified if the free silicon has been etched off. As a rule, silicon carbide is deposited as crystalline P-Sic with small amounts of Cc-Sic. REFERENCES 1 J. J. Nick1 and Christine von Braunmlihl, J. Less-Common Metals, 25 (1971) 303. 2 S. V. Syavtsillo, A. M. Nikol’skaya and T. M. Mashko, Vysokotemp. Neorg. Soedin., (1965) 395-396; see also C/tern. Abstr., 64 (1966) 14955b. 3 P. J. Holmes, Proc. Inst. Elec. Eng., B 106 (Suppl. 17) (1959) 861. 4 JANAF Thermochemical Tables PB 168 370. 1965, and PB 168 370-2, 1967, Dow Chemical Co., Midland, Michigan, USA. 5 J. Gram and E. Wagner, Appl.,Phys. Letters. 21 (1972) 67-69. 6 P. Rai-Choudhury and N. P. Formigoni, J. Electrochem. SOL, 116 (1969) 1440-1443. 7 H. Nakashima, T. Sugano and H. Yanai, Japan J. A&. Phys., 5 (1966) 874-878. 8 J. J. Nickl, K. K. Schweitzer and P. Luxenberg, J. Less-Common Metals, 26 (1972) 335-353. 9 J. J. Nick1 and R. Vesper, J. Less-Common Metals, 25 (1971) 275. 10 W. F. Knippenberg, Theses, Univ. Leiden, 1963.

CHEMICAL

VAPOR

11 W. Spielmann.

DEPOSITION

IN THE Si-C AND Si-C-N

SYSTEMS

2. Angew. Phys.. I9 (1965) 93. 12 T. Arizumi. T. Nishinaga and H. Ogawa. Japan. J. Appl. Phys.. 7 ( 1968) 1023-1027. 13 E. A. Taft. J. ~lecfroe~en~ Sot., I18 fi97I) 1341-1346. 14 R. G. Frieser, J. Efectrochrm. Sot., 115 (1968) 1092-1094.

329