Processing Variables and Parameters

In general, there are three modes of IBAD. Several examples of the material systems that are deposited using each of the modes are given in Table 1. Mode 1 of this table identifies a simple type of ion assist, in which inert heavy ions, such as argon, are used to improve the properties of an elemental film or a compound film that undergoes congruent evaporation. In this case, it is important to minimize the amount of argon incorporated into the film, which increases with the arrival ratio, R, and the beam energy. Therefore, the lowest R value possible, consistent with obtaining the desired film properties, should be used. This mode also includes materials such as cerium oxide, which is typically slightly substoichiometric when simply deposited by evaporation. An ion assist with argon ions can be used for densification only, or oxygen ions can be used for densification and to restore stoichiometry.

Table 1 Three modes of film formation for ion-beam-assisted deposition (IBAD)

Vapor

Ion or ion/gas

Film

Mode 1: IBAD

Ge

Ar

Ge

Ag

Ar

Ag

CeO2

O

CeO2

Ta2O3

O

Ta2O5

Mode 2: IBAD (Compound synthesis)

Si

N

S4N4

B

N

BN

Si

CH4

SiC

Cu

O

Cu2O

Mode 3: Reactive IBAD

Ti

N/N

TiN

Ti

Ar/N

TiN

Nb

N/N

NbN

Al

O/O

Al2O3

Ge, germanium; Ar, argon; Si, silicon; N, nitrogen; Si3N4, silicon nitride; TiN, titanium nitride; Ag, silver; B, boron; CeO2, cerium oxide; O, oxygen; CH4, methane; SiC, silicon carbide; Nb, niobium; Ta2O3, tantalum oxide; Ta2O5, tantalum pentoxide; Cu, copper; Cu2O, copper oxide; Al, aluminum; Al2O3, aluminum oxide

Mode 2 in Table 1 identifies an ion assist and compound synthesis group, in which there is little reaction probability of the ambient gas with the evaporant. All of the material that forms the compound in this deposition mode comes from the evaporation source, as well as directly from the ion beam.

Mode 3 in Table 1 covers compound synthesis that is possible only for very reactive materials. It can occur either with the gas associated with the ion beam (e.g., N2 for titanium nitride) or when inert ions such as argon are used in conjunction with a secondary (background) gas supply of N2. In the latter case, the purpose of the ions is to activate and control surface chemical reactions.

Table 2 is a selected compilation of materials that have been grown using IBAD processes. For application to metals, the oxides and pure metals are often used as corrosion-resistant coatings, whereas nitrides and some oxides are used as wear-resistant and corrosion-resistant coatings. The widespread application of these coatings for nonelectronic purposes is still new, but there is some evidence that the appropriate thickness for hard coatings for sliding wear resistance is 0.2 to 2 pm (8 to 80 pin.), and that for pin-hole-free corrosion-resistant coatings, a minimum thickness of 2 pm (80 pin.) is required. For abrasion-resistant coatings, very thick and hard coats can be deposited, although this has not been emphasized in the initial development of the technique. Optical coatings up to 15 pm (215 pin.) thick also have been deposited. Typical process parameters are shown in Table 3.

Table 2 Deposition and synthesis of inorganic compounds by ion-beam-assisted deposition (IBAD)

Material

Method

Evaporant

Ion

Energy, eV

R

Gas

Temperature

Comments

Ref

°C

°F

ZrO2

IBAD

ZrO2

Ar+

600

0.82

20, 300

70, 570

15

ZrO2

IBAD

ZrO2

Ar+/ O2+

600/1200

0.33

O2

20, 300

70, 570

Best films w/ O2+ cubic and monoclinic

16

ZrO2

IBAD

ZrO2

O2+ /O+

600/1200

0-10

25

75

17

ZrO2

Reactive IBAD

ZrO2

o+

1200

O2

275

525

18

TiO2

Reactive IBAD

TiO, TiO2

o+

0-100

0.30.6

O2

50300

120570

19, 20

TiO2

Reactive IBAD

TiO

O-

O2

25

75

21

TiO2

Reactive IBAD

Ti2O3

o2+

Amorphous

21

TiO2

Reactive

TiO

O+, o2+

30, 500

0-0.8

O2

50-

120-

22

Material

Method

Evaporant

Ion

Energy, eV

R

Gas

Temperature

Comments

Ref

°C

°F

IBAD

100

210

TiO2

Reactive IBAD

TiO, TiO2

o2+

30, 500

0-1.3

O2

50100

120210

23, 24

TiO2

Reactive IBAD

TiO

o2+

600

0.30.9

O2

25

75

25

TiO2

Reactive IBAD

TiO2

o2+

300

0.10.4

O2

175

345

Optimum R = 0.2

26

SiO2

Reactive IBAD

SiO

O-

O2

290

555

21

SiO2

Reactive IBAD

SiO

Ar+

600

0.03

O2

25

75

25

SiO2

Reactive IBAD

SiO

O+, O+

300, 500

0.251.7

O2

50100, 275

120210, 525

Not sensitive to IBAD conditions

18, 22

Al2O3

Reactive IBAD

Al2O3

O+

300-1000

0.080.8

O2

275

525

Optimum R = 0.2 at 1000 eV

18

Al2O3

Reactive IBAD

Al2O3

O+

300

1.33

O2

125

255

27

Al2O3

Reactive IBAD

Al2O3

O+

1200

0.6

O2

20, 300

70, 570

28

Al2O3

Reactive IBAD

Al

O+

500

0.16

O2

25

75

29

CeO2

Reactive IBAD

CeO2

O+

300, 600, 1200

1.9

O2

20, 300

70, 570

30

CeO2

Reactive IBAD

CeO2

O+

1200

0.84

O2

20, 300

70, 570

31

HfO2

Reactive IBAD

HfO2

O+

300

0.25

O2

300

570

32

Ta2O5

Reactive

Ta2O5

O+

1200

2.6

O2

300

570

31

Material

Method

Evaporant

Ion

Energy, eV

R

Gas

Temperature

Comments

Ref

°C

°F

IBAD

Ta2O5

Reactive IBAD

Ta2O5

02

300-1000

0.081.4

O2

275

525

Optimum R = 0.6 at 300 eV

18

Ta2O5

Reactive IBAD

Ta2O5

02

300

2.8

O2

125

255

27

VO2

IBAD

V

02

600

800600

1751110

32

MgF2

IBAD

MgF2

Ar+

125-1000

0.04

25

75

High ^-preferential sputtering of F

33

MgF2

Reactive IBAD

(C2F6)

80-1400

0.050.1

C2F6

25

75

Low E best

34, 35

MgF2

IBAD

MgF2

02

350-750

0.120.25

O2

20, 300

70, 570

Crystalline

36

MgF2

IBAD

MgF2

Ar+, 02

300

0.30.34

25

75

37

LaF3

IBAD

LaF3

Ar+, 02

300, 500

0.220.57

25

75

R = 0.05, 0+ optimum

37, 38

Cryolite

IBAD

Na3AlF6

Ar+, 02

200, 300

0.250.75

25

75

R = 0.75 at 300 eV 02 optimum

37

ThF4

IBAD

ThF4

Ar+

300

0.050.35

25

75

39

beam sputter

Si

N+, n+

680

2.05

n2

<200

<390

Partially amorphous

40, 41

Si3N4

Reactive IBAD

Si

N+

60, 100

2.1

n2

25

75

42

Si3N4

IBAD

Si

N+

500

01.33

25

75

Corrosion protection, optical properties

43, 44

Material

Method

Evaporant

Ion

Energy, eV

R

Gas

Temperature

Comments

Ref

°C

°F

S13N4

IBAD

S1

N+

20,000100,000

0-1

<200

<390

Ox1dat1on protection

45

S13N4

IBAD

S1

N+

100

0-1.3

<100

<210

Multilayer x-ray mirrors

46

S13N4

IBAD

S1

N

500-1000

0-1.4

n2

<100

<210

Process characterization

4, 5

S1(i-x)Nx

Reactive IBAD

S1

n+

1000

0-1.3

n2

<70

<160

Amorphous f1lms

47

S1ON

IBAD

S1

o2+, n2+

3000

300

570

41

SiNH

IBAD

S1

nh3

500

0-1.4

nh3

<100

<210

Optical f1lms

48

beam sputter

Al

n+

100-500

0-2.6

n2

25

75

AlN at R = 1

6

AlN

IBAD

Al

n+

200-1000

0.5

N

100

210

Oriented f1lms

49

AlN

Reactive IBAD

Al

n+

250-1000

0.52.7

n2

100

210

50

AlN

IBAD

Al

3.4

25

75

29

AlON

Reactive IBAD

Al

n+

750

0.71.0

o2

100

210

51

AlON

IBAD

AlN

o2+, N2+

300

300

570

41

T1N

Reactive IBAD

T1

T1+, N+

30/40,000

0.0010.6

n2

25700

751290

52

T1N

Reactive IBAD

T1

N

12,000

n2

Structure

53

T1N

Reactive IBAD

T1

n+

5000

0-1

n2

54

Material

Method

Evaporant

Ion

Energy, eV

R

Gas

Temperature

Comments

Ref

°C

°F

TiN

Reactive IBAD

Ti

N+

1000

0.010.03

n2

55

TiN

Reactive IBAD

Ti

N+

10-30,000

1.0

n2

300

570

56

TiN

Reactive IBAD

Ti

N+, N 2+

20,000

1.0

n2

35

95

57

TiN

Bias magnetron

Ti

Ar+ + n2+

2-200

0.41.0

n2

300600

5701110

51

beam sputter

Ti

n+

200

0.25

n2

400

750

Ti3N4 forms with excess N

58

TiN

IBAD

Ti

n+

30,000

0.120.77

100300

210570

59

TiN

Reactive IBAD

Ti

500

0-1.1

n2

25

75

Process parameters

44

TiN

Reactive IBAD

Ti

Ar+

12,000

1

n2

<250

<480

Comparison with other techniques

60, 61

TiN

Ion plating

Ti

N+ + N+

200

n2

<100

<210

Batch processing of sheet metal

14

TiN

IBAD

Ti

N+

20,000

0.371.1

62

TiN

IBAD

Ti

N+ + n+

20,000

1.0

200300

390570

Extensive data

63

TiN

Reactive IBAD

Ti

N+

40,000

0-0.3

n2

<100

<210

Oriented films

64

TiN

Reactive bias magnetron

Ti

N+

300-500

4.1

550850

10201560

Single crystal, epitaxial

65

CrN

IBAD

Cr

N+

20,000

0.5-2

n2

Oriented films

66

Material

Method

Evaporant

Ion

Energy, eV

R

Gas

Temperature

Comments

Ref

°C

°F

CrN

IBAD

Cr

N+

12,000

10--4-0.1

25

75

High hardness

9

BN

Reactive IBAD

B

N+

25-40,000

0.7

n2

200

390

Some cubic BN

67

BN

IBAD

B

N+

120,000

300

570

Ion-beam mixing

68

BN

IBAD

B

N2+ + N+

200-1000

1.0

69

BN

IBAD

B

N+

80-500

1.02.0

280300

535570

70

BN

IBAD

B

N+

500

2.55

200

390

71

BN

IBAD

B

N+

200

1

300

570

Cubic BN

72

BN

IBAD

B

N+

250-2000

0-1.5

25

75

Hardness, stress

73

BN

IBAD

B

N+

200020,000

n2

Cubic BN

74

TiC

IBAD

Ti, C

Ar+

100,000

0.01

25

75

^=Ar/Ti ratio

75

TiC

Ion plating

TiC

Ar+

200

<100

<210

Batch processing of sheet metal

14

beam sputter

Zr

n+

200

0.25

400

750

58

ZrN

Reactive IBAD

Zr

n+

200-700

n2

25

75

Coated shaver screens

76

ZrN

Reactive IBAD

Zr

N+

30,000

1

n2

<300

<570

Chemistry, microstructure

77

beam sputter

Hf

N+

200

0.25

400

750

Hf3N4 also formed

58

Material

Method

Evaporant

Ion

Energy, eV

R

Gas

Temperature

Comments

Ref

°C

°F

MoN

Reactive IBAD

Mo

N+, n+

40,000

1.0

n2

25500

75930

B1 structure for 25 °C (77 °F)

78

MoN

IBAD

Mo

N+

500-1000

0-1.2

n2

<100

<210

Pure phases

79

beam sputter

Nb

N+ +CH4

50-100

n2+ch4

<60

<140

80

InSnO

Reactive IBAD

In2O3-9SnO2

o+

100

1.0

O2

25400

75750

Amorphous <100

81

InSnO

Reactive IBAD

InSnO

O+

1200

0.71.0

O2

50150

120300

82

WSi2

IBAD

W, Si

Ar+

100-400

0.050.25

25500

75930

Amorphous at room temperature

83

CuO

IBAD

Cu

o2+

<200

0.010.1

O2

25

75

Formed Cu2O, CuO, Cu5O4

84

YBaCuO

Reactive IBAD

YBa2Cu4Ox

Ar+ + 2O2+

50

O2

560640

10401180

85

YBaCuO

IBAD

BaF2, Cu, Y

O+, o2+

50

600

1110

Single-crystal epitaxial films

86

beam sputter

MoS2

Ar+

1000

0.010.1

25

75

Low friction

87

DLC

IBAD

C

Ar+, Ne+

200-1000

0.050.7

<100

<210

88

DLC

Ion-beam sputter

C

Ar

1200

H2

25

75

Few diamond crystals in amorphous C

89

DLC

Ion-beam deposition

C+

10-175

<400

<750

90, 91

DLC

Ion-beam deposition

CH4

100-1200

CH4

25

75

Deposition rates microstructure

92

Material

Method

Evaporant

Ion

Energy, eV

R

Gas

Temperature

Comments

Ref

°C

°F

DLC

Ion-beam deposition

CH4

500-1000

CH4

25

75

Composition, applications

93

B

IBAD

B

Ar+

6000

25

75

Low stress

94

B

IBAD

B

Ar+

6000

10-40.1

25

75

Corrosion protection, adhesion

9

B

IBAD

B

Ar+

300015,000

0-0.1

Stress control

95

C

Ion-beam deposition

C+

5-200

25

75

X-ray mirrors

96

C

IBAD

C

Ar+

Densification

97

Al

IBAD

Al

He, Ne, Ar, Kr, Xe

20020,000

0-0.3

Thorough study

98

Al

IBAD

Al

Ar+

50-2000

0.0010.1

25

75

Oriented films

99

Si

Ion-beam deposition

Si+

5-200

25

75

X-ray mirrors

96

Cr

IBAD

Cr

Ar+

300015,000

0-0.1

Stress control

95

Cr

IBAD

Cr

N+

60,000

0.1

Turbine blade coatings

100

Cr

IBAD

Cr

Ar+

11,500

25

75

Low stress

8

Cr

IBAD

Cr

Ar+

6000

25

75

Low stress

94

Cr

IBAD

Cr

Ar+

60-800

0-1.5

25

75

Stress, resistivity

101, 102

Fe

IBAD

Fe

Ar+

60-800

0-1.5

25

75

Stress, resistivity

101, 102

Material

Method

Evaporant

Ion

Energy, eV

R

Gas

Temperature

Comments

Ref

°C

°F

Permalloy

IBAD

Fe-Ni

Ar+

300

Low stress

103

Co

IBAD

Co

Ar+

60-800

0-1.5

25

75

Stress, resistivity

101, 102

Ni

IBAD

Ni

Ar+

60-800

0-1.5

25

75

Stress, resistivity

101, 102

Ni

Ion-beam deposition

Ni+

5-200

30

85

X-ray mirrors

96

Cu

IBAD

Cu

Ar+

60-800

0-1.5

25

75

Stress, resistivity

101, 102

Cu

IBAD

Cu

Ar+

On polytetrafluoroethylene

104

Cu

IBAD

Cu

Ar+

105

Nb

IBAD

Nb

Ar+

60-800

0-1.5

25

75

Stress, resistivity

101, 102

Ag

IBAD

Ag

Ar+

On polytetrafluoroethylene

104

Ag

IBAD

Ag

Ar+

106

Ta

IBAD

Ta

Ar+

60-800

0-1.5

25

75

Stress, resistivity

101, 102

W

Ion-beam deposition

W+

5-200

25

75

X-ray mirrors

96

W

IBAD

W

Ar+

60-800

0-1.5

25

75

Stress, resistivity

101, 102

Au

IBAD

Au

Ar+

On polytetrafluoroethylene

104

Au

IBAD

Au

Ar+

On glass

107

Material

Method

Evaporant

Ion

Energy, eV

R

Gas

Temperature

Comments

Ref

°C

°F

Au

IBAD

Au

Ar+

On glass

94

Au

IBAD

Au

Ar+

300

0-1

25250

77480

Good adhesion

Table 3 Typical values of ion-beam-assisted deposition process variables

Source: Ref 1

Table 3 Typical values of ion-beam-assisted deposition process variables

Variable

Value

Vapor deposition rate, ^m/h (^in./h)

1-40 (40-1600)

Chamber base pressure, Pa (torr)

226 x 10-7 (2 x 10-7)

Operating pressure, Pa (torr) (with backfill gas), Pa (torr)

0.003 to 0.03 (2 x 10-5 to 2 x 10-4) 0.007 to 0.03 (5 x 10-5 to 2 x 10-4)

Fraction-exchange neutralized

0.1-2 (0.6-13) 0.05-0.40

Arrival ratio

0.1-1.5

Substrate temperature, °C (°F)

<100 (<210)

0 0

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