Relation Between Internal Stress and Surface Roughness of Titanium Nitride Films Deposited by HCD Ion Plating

Transcription

1 No.22,28 65 Relation Between Internal Stress and Surface Roughness of Titanium Nitride Films Deposited by HCD Ion Plating Itsuo Ishigami Ken-ichi Miura Hideaki Hoshino Tomoyuki Mizukoshi ( ) An experiment was made to elucidate variations in surface roughness of Ti-N films with process parameters: deposition temperature, deposition time, electron beam current, substrate bias voltage, total gas pressure, mixture ratio of nitrogen to argon, distance between the substrate and evaporation source, and inclination of a substrate. Furthermore, an attempt was made to find out factors controlling the roughness and to reveal the relation between the factors and the roughness. The Ti-N films were deposited onto SKH51 substrates. A main constituent in the films was TiN. A surface roughness tester is contact type, of which the stylus tip has a 5 μm radius. No accounting for changes in the roughness existed based on material characteristics such as phase, chemical composition, and grain size. Deposition in a lower temperature range brought about excess surface roughening due to flaking and the formation of cracks which might be given rise to compressive stress in the films. Comparison of smooth surfaces free from the above shape defects revealed that the film of a stronger (hkl) fiber structure possessed a smooth surface. The strain ε'33 normal to the film surface was measured using an X-ray diffraction technique, revealing that the ε'33 values depended on crystal orientations of the film surface planes. Changes in the surface roughness can be interpreted in terms of a difference in strain of columnar grains perpendicular to the substrate surface, for TiN films. HCD (PVD) PVD (HCD) 1 9) 9 13)

2 66 ( ) 14, 15) 16) 17 19) HCD (c) Plane (1) HCD SHP-4T Fig mm CA 14.5cm 3 SKH51 Table mm 718 HV.5 Rz nm Table 2 Ar vol% (2) (A) ( 713D) 5 μm (b) Side (a) Front Fig. 1 Schematic representation of an HCD type ion plating unit. Table 1 Chemical composition of SKH51 substrate used (mass%). C Si Mn Cr Mo V Co W mm/s4. mm.8 mm.2 μm Rz Ra Rz

3 No.22,28 67 Table 2 Deposition parameters and their ranges applied to titanium nitride depositing *1. Parameter Range Standard Deposition temperature, T (K) Deposition time, t (s) Electron beam current *2, I b(a) Substrate bias voltage, V B (V) 9 3 Total gas flow *3, F (cm 3 /s) Total gas pressure, P (Pa) ,.67 [N 2 /(Ar+N 2 )], R N 2 () 2.89 Pa Pa Distance *4, L (mm) Tilting angle *5, θ (rad) π *1 Depositions were carried out by varying one parameter; the others were fixed at the values in the right column. *2 Electron beam voltages applied were within the range of 2 to 25 V. *3 Volume in the standard state; total gas pressure changes according to total gas, Ar + N 2, flow. *4 Distance between a substrate and an evaporation source. *5 A substrate axis was tilted θ from the direction in which an evaporation source was located (see Fig. 1 (b)). (B) X sin2ψ 2) CuKα TiN θ sin2ψ σ E π 2θ = cot θ (1) 2 ( 1+ ν) 18 sin 2 ψ E ν X 2θ TiN E = 411 GPaν =.236 2θ = ) (C) (EPMA) ZAF 21, 22) 2, 3) (D) X 23) TiN111 k λ Gs = (2) BcosθB G s k *1 1) (.9 )λ X (CuKα )B θ B (E) ( VK-G3) 1/3 (F) X (SEM) (1) Fig. 2 Rz *1 95 % Fig K (Fig. 3 (a), (b)) 69 K 659 K 1 2 μm 77 K Fig. 3 (c) μm Fig. 2 Roughness, Rz (μm) Substrate Rz Deposition Temperature, T (K) Fig. 2 Changes in surface roughness Rz and internal stress σ with deposition temperature T Stress, (GPa)

4 68 (a) (b) (c) 1μm 2μm 1μm Fig. 3 Surface appearances of TiN films deposited at (a), (b) 33 K and (c) 77 K. 4 11) GPa (Fig. 3 (b))fig. 2 (2) Fig. 4 V (8.9 MPa) Fig. 5 Thornton 24) zone (Fig. 5 (a)) ((b) (d)) zone T Fig. 4 Fig. 5 (a) (b) Roughness, Rz (μm) Substrate Rz Fig. 4 Changes in surface roughness Rz and internal stress σ with substrate bias voltage V B. Substrate Bias Voltage, V B (V) Stress, (GPa) (c) (e) (g) 5nm (d) (f) Fig. 5 Typical SEM micrographs of fracture and surface of TiN films grown at various substrate bias voltages V B ; (a) V, (b) 1V, (c) 5V, (d) 15V, (e) 3V, (f) 6V, (g) 9V.

5 No.22,28 69 Fig. 5 (a) (c) Fig. 4 Fig. 4 5 μm 4. mm(.2 μm) Ra Fig. 4 (3) Fig. 6 Fig. 2 Fig. 4 Fig. 6 Fig. 2 Fig. 4 Fig. 6 Fig. 2 Fig. 4 Fig. 6 (4) Fig Pa α-ti Ti 2 N.67 Pa Ti 2 N TiN.67 Pa 1.6 Pa φ2 1 mm mm.147 rad.67 Pa Fig. 7 (5) Rz Table 3 σ Table 3 Rz K Roughness, Rz (μm) Substrate Rz Deposition Time, t (ks) Stress, (GPa) Roughness, Rz (μm) Substrate -Ti +Ti 2 N TiN+ Ti 2 N (little) Rz TiN Total Gas Pressure, P (Pa) Stress, (GPa) Fig. 6 Changes in surface roughness Rz and internal stress σ with deposition time t. Fig. 7 Changes in surface roughness Rz and internal stress σ with total gas pressure P.

6 7 Table 3 Changes in properties with an increase in process parameter *1. Parameters *2 Rz σ *3 Phase Composition Temperature Deposition Grain size hardness Substrate Deposition Evaporation [O] [N] / [Ti] rate (TiN) chamber chamber T TiN t TiN w w I b w TiN w w V B w TiN w w w P TiN Ti 2 N α-ti R N2 2.89Pa w TiN w w.67pa w TiN+Ti2 N *4 unmeasured L w TiN w θ TiN w w *1, increased, decreased, decreased after increasing, increased after decreasing w, varied weakly, not varied. *2 See Table 2. *3 Compressive stress except when substrate bias voltage was not applied. *4 There existed only a little Ti 2 N. Fig.8 X TiN111 TiN22 TiN111 TiN22 25) 5 cps T I h'k'l' h'k'l' = n TiN22 (1/ n) I ( I TiN111 TiN2 h'k'l' hkl TiN311 / I Fig. 8 X-ray diffraction patterns obtained from titanium nitride films deposited under various total gas pressures P. hkl ) TiN222 TiN42 TiN331 TiN4 TiN111 TiN22 TiN422 TiN Pa 1.6 Pa 1.24 Pa.67 Pa.45 Pa (3) 6.13 Pa 4.4 Pa 2.89 Pa h k l ( )I h k l I h k l T h k l 1 n Fig. 1 1 JPCDS (38-142) Fig. 9 T 111 T 22 Fig. 7 Texture Coefficient, T h'k'l' () T 22 T Total Gas Pressure, P (Pa) Fig. 9 Variations in texture coefficient T h k l with total gas pressure P for TiN films.

7 No.22, ) Fig. 7 Fig V Fig. 1 TiN 27) a a Pearson ([N] / [Ti] a) 28) EPMA [N] / [Ti] 1V 15 V 5.64 μm Fig. 1 ε μm 15 V Fig. 5(d) Fig. 1 ε 33 Fig. 4 Rz.18 μm Rz (2 (2) Diffraction Plane, hkl (A) ) Fig.11 Fig. 4 T 111 T 22 Fig. 11 V B = V 1 V (T 111 T 422 ) (T 111 T 311 ) (T 111 T 422 ) (T 111 T 511 ) 2.89 Pa.975 (T 111 T 422 ).67 Pa (T 111 T 22 ) ( K) Strain,, 33 (%) V B (V) Rz(μm) (GPa) excluded system error Texture Coefficient, T h'k'l' () T 111 lnt h'k'l' =a+bln(-v B ) T cos cot Fig. 1 Elastic strain ε ' 33 measured perpendicular to the substrate surface, for TiN films Substrate Bias Voltage, V B (V) Fig. 11 Variations in texture coefficient T h k l with substrate bias voltage V B for TiN films.

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