Manufacturing Process of a Micromachined Filter

Step No. General Step Input Detailed Step Material Temp./ºC Time Pressure Other Data/Comments Result/Output

Wafer 1: Microstrip Lines and Slots

1-1 Piranha Etch plain wafer 1 etch bath H₂O₂:H₂SO₄ (1:1) 120 10 min cleaned wafer 1

1-2 rinse H₂O ~15 min

1-3 dry N₂

1-4 Ground Plane on Bottom of Wafer 1 cleaned wafer 1 evaporation Ti 500 Å
Au 4000 Å <1*10^-6 Torr wafer 1 w/ metallized bottom

1-5 electroplating Au ? ? current: ? mA
thickness: 4.5 µm
area: ? cm²
spin bar: ? rpm

1-6 rinse H₂O

1-7 dry N₂

1-8 Opening of vias wafer 1 w/ metallized bottom PECVD deposition of Si₃N₄ as masking layer SiH₄ - 100 sccm
He - 990 sccm
NH₃ - 10 sccm
N₂ -900 sccm 400 ~6.5 min thickness: 1000 Å
power: 100 W
rate: ~150Å/min
thickness: ~1000 Å wafer 1 w/ opened vias

1-9 adhesion promoter HMDS 30 s 3500 rpm

1-10 wait 10 s

1-11 negative PR AZ 5214 30 s 3500 rpm
thickness: ~1.5 µm

1-12 softbake 105 1 min softbake on hotplate

1-13 mask alignment mask: standard 4" chromium mask

1-14 exposure 4.5 s

1-15 hardbake 130 1 min hardbake on hotplate

1-16 flood expose 90 s expose w/o mask

1-17 development MF 327 20-40 s

1-18 rinse H₂O

1-19 dry N₂

1-20 descum plasma etcher w/ O₂ 1 min 250 mT power: 100 W

1-21 Si₃N₄ etch plasma etcher w/ CF₄ - 25 sccm
O₂ - 0.5 sccm 5 min 250 mT power: 100 W

1-22 removal of PR ACE
IPA 30 s
30 s

1-23 dry N₂

1-24 descum plasma etcher w/ O₂ 1 min 250 mT power: 100 W

1-25 Si etch KOH:DI H₂O (300 g:600 ml) 65 17.5 h etch all way through wafer
rate: 3.5 h/100 µm

1-26 rinse H₂O

1-27 dry N₂

1-28 remove PR ACE
IPA 30 s
30 s

1-29 dry N₂

1-30 Lithography I: Microstrip Lines on Top of Wafer 1 wafer1 w/ opened vias evaporation Ti 500 Å
Al 2000 Å
Ti 500 Å <1*10-6 Torr wafer 1 w/ patterned PR for microstrip lines

1-31 adhesion promoter HMDS 30 s 3500 rpm

1-32 wait 10 s

1-33 positive PR 1813 30 s 3500 rpm
thickness: ~1.5 µm

1-34 softbake 105 1 min softbake on hotplate

1-35 mask alignment

1-36 exposure 6 s

1-37 development MP 351:DI H₂O (1:5) 17 s

1-38 rinse H₂O

1-39 dry N₂

1-40 hardbake 130 1 min hardbake on hotplate

1-41 Installation of Microstrip Lines wafer 1 w/ patterned PR formicrostrip lines etch Ti HF:DI H₂O (1:10) 5 s wafer 1 w/ microstriplines on top

1-42 rinse H₂O

1-43 dry N₂

1-44 electroplating Au ? ? current: ? mA
thickness: 4.5 µm
area: ? cm²
spin bar: ? rpm

1-45 rinse H₂O

1-46 dry N₂

1-47 remove PR ACE
IPA 30 s
30 s

1-48 dry N₂

1-49 descum plasma etcher w/ O₂ 1 min 250 mT power: 100 W

1-50 remove Ti HF:DI H₂O (1:10) 5 s

1-51 rinse H₂O

1-52 dry N₂

1-53 remove Au (2000 Å) ? 2 min

1-54 rinse H₂O

1-55 dry N₂

1-56 remove Ti HF:DI H₂O (1:10) 5 s

1-57 rinse H₂O

1-58 dry N₂

1-59 Lithography II: Definition of Slots on Bottom of Wafer 1 wafer 1 w/ metallized bottom adhesion promoter HMDS 30 s 3500 rpm wafer 1 w/patterned PR for slots on bottom

1-60 wait 10 s

1-61 positive PR 1813 30 s 3500 rpm
thickness: ~1.5 µm

1-62 softbake 105 1 min softbake on hotplate

1-63 mask alignment

1-64 exposure 6 s

1-65 development MP 351:DI H₂O (1:5) 17 s

1-66 rinse H₂O

1-67 dry N₂

1-68 hardbake 130 1 min hardbake on hotplate

1-69 Opening of Slots on Bottom of Wafer 1 wafer 1 w/ patterned PR for slots on bottom etch Au ? ? wafer 1 w/ microstrip lines and slots

1-70 rinse H₂O

1-71 dry N₂

1-72 etch Ti HF:DI H₂O (1:10) 5 s

1-73 rinse H₂O

1-74 dry N₂

1-75 remove PR ACE
IPA 30 s
30 s

1-76 dry N₂

1-77 descum plasma etcher w/ O₂ 1 min 250 mT power: 100 W

Wafer 2: Cavity Wafer

2-1 Piranha Etch plain wafer 2 etch bath H₂O₂:H₂SO₄ (1:1) 120 10 min cleaned wafer 2

2-2 rinse H₂O ~15 min

2-3 dry N₂

2-4 Lithography I: Cavity cleaned wafer 2 adhesion promoter HMDS 30s 3500 rpm wafer 2 w/ PR patterned for cavity

2-5 wait 10 s

2-6 positive PR 1827 30 s 3500 rpm
thickness: ~3 µm

2-7 softbake 105 1 min softbake on hotplate

2-8 mask alignment

2-9 exposure 6 s

2-10 development MP 351:DI H₂O (1:5) 25 s

2-11 rinse H₂O

2-12 dry N₂

2-13 hardbake 130 1 min hardbake on hotplate

2-14 Opening of Cavity wafer 2 w/ PR patterned for cavity SiO₂ etch BHF 8 min rate: 1000 Å/min wafer 2 w/ opened cavity

2-15 rinse H₂O

2-16 dry N₂

2-17 remove PR ACE
IPA 30 s
30 s

2-18 dry N₂

2-19 Si etch TMAH/H₂O (22wt%) 90 ~ 8.3 h rate: 1 µm/min
etch all way through wafer

2-20 rinse H₂O

2-21 dry N₂

2-22 Metallization wafer 2 w/ opened cavity evaporation Ti 500 Å
Al 15000 Å
Ti 500 Å
Au 3000 Å <1*10^-6 Torr wafer 2 w/ metallized cavity

Wafer 3: Bottom Covering

3-1 Piranha Etch plain wafer 3 etch bath H₂O₂:H₂SO₄ (1:1) 120 10 min cleaned wafer 3

3-2 rinse H₂O ~15 min

3-3 dry N₂

3-4 Metallization cleaned wafer 3 evaporation Ti 500 Å
Al 15000Å
Ti 500 Å
Au 3000 Å <1*10^-6 Torr wafer 3 w/ metallized top side

Sandwich 1: Wafers 2 & 3 Bonded Together

4-1 Bonding a) wafer 2 w/ metallized cavity
b) wafer 3 w/ metallized top side bonding layer silver epoxy applied to backside of wafer 2 wafers 2 & 3 bonded

4-2 bonding layer silver epoxy applied to top of wafer 3

4-3 place wafer 2 on top of wafer 3

4-4 place both between glass slides

4-5 place glass slides w/ wafers on hotplate

4-6 apply weights on top of glass plates

4-7 bonding 130 15 min

4-8 cool down to rm. temp.

4-9 Sealing wafers 2 & 3 bonded rinse ACE
IPA sandwich 1

4-10 dry N₂

4-11 place on hotplate

4-12 bake 130 1 min until completely dry

4-13 protect alignment marks by covering w/ small pieces of Si adhered to wafer w/ PR

4-14 evaporation Al 4000 Å
Au 5000 Å <1*10^-6 Torr

4-15 remove covering of alignment marks ACE
IPA 30 s
30 s

4-16

Sandwich 2: Wafer 1 & Sandwich 1 Bonded Together

5-1 Bonding a) wafer 1 w/ microstrip lines and slots
b) sandwich 1 bonding layer silver epoxy applied to bottom of wafer 1 and around cavity on sandwich 1 filter (final product)

5-2 fix wafer 1 on vacuum chuck of electrostatic bonding machine

5-3 place sandwich 1 on hotplate beneath chuck

5-4 alignment

5-5 lower chuck w/ wafer 1 on sandwich

5-6 bonding 150 10 min

5-7 cool down to rm. temp.

Step No.	General Step	Input	Detailed Step	Material	Temp./ºC	Time	Pressure	Other Data/Comments	Result/Output
Wafer 1: Microstrip Lines and Slots
1-1	Piranha Etch	plain wafer 1	etch bath	H₂O₂:H₂SO₄ (1:1)	120	10 min			cleaned wafer 1
1-2			rinse	H₂O		~15 min
1-3			dry	N₂
1-4	Ground Plane on Bottom of Wafer 1	cleaned wafer 1	evaporation	Ti 500 Å Au 4000 Å			<1*10^-6 Torr		wafer 1 w/ metallized bottom
1-5			electroplating	Au	?	?		current: ? mA thickness: 4.5 µm area: ? cm² spin bar: ? rpm
1-6			rinse	H₂O
1-7			dry	N₂
1-8	Opening of vias	wafer 1 w/ metallized bottom	PECVD deposition of Si₃N₄ as masking layer	SiH₄ - 100 sccm He - 990 sccm NH₃ - 10 sccm N₂ -900 sccm	400	~6.5 min		thickness: 1000 Å power: 100 W rate: ~150Å/min thickness: ~1000 Å	wafer 1 w/ opened vias
1-9			adhesion promoter	HMDS		30 s		3500 rpm
1-10			wait			10 s
1-11			negative PR	AZ 5214		30 s		3500 rpm thickness: ~1.5 µm
1-12			softbake		105	1 min		softbake on hotplate
1-13			mask alignment					mask: standard 4" chromium mask
1-14			exposure			4.5 s
1-15			hardbake		130	1 min		hardbake on hotplate
1-16			flood expose			90 s		expose w/o mask
1-17			development	MF 327		20-40 s
1-18			rinse	H₂O
1-19			dry	N₂
1-20			descum	plasma etcher w/ O₂		1 min	250 mT	power: 100 W
1-21			Si₃N₄ etch	plasma etcher w/ CF₄ - 25 sccm O₂ - 0.5 sccm		5 min	250 mT	power: 100 W
1-22			removal of PR	ACE IPA		30 s 30 s
1-23			dry	N₂
1-24			descum	plasma etcher w/ O₂		1 min	250 mT	power: 100 W
1-25			Si etch	KOH:DI H₂O (300 g:600 ml)	65	17.5 h		etch all way through wafer rate: 3.5 h/100 µm
1-26			rinse	H₂O
1-27			dry	N₂
1-28			remove PR	ACE IPA		30 s 30 s
1-29			dry	N₂
1-30	Lithography I: Microstrip Lines on Top of Wafer 1	wafer1 w/ opened vias	evaporation	Ti 500 Å Al 2000 Å Ti 500 Å			<1*10-6 Torr		wafer 1 w/ patterned PR for microstrip lines
1-31			adhesion promoter	HMDS		30 s		3500 rpm
1-32			wait			10 s
1-33			positive PR	1813		30 s		3500 rpm thickness: ~1.5 µm
1-34			softbake		105	1 min		softbake on hotplate
1-35			mask alignment
1-36			exposure			6 s
1-37			development	MP 351:DI H₂O (1:5)		17 s
1-38			rinse	H₂O
1-39			dry	N₂
1-40			hardbake		130	1 min		hardbake on hotplate
1-41	Installation of Microstrip Lines	wafer 1 w/ patterned PR formicrostrip lines	etch Ti	HF:DI H₂O (1:10)		5 s			wafer 1 w/ microstriplines on top
1-42			rinse	H₂O
1-43			dry	N₂
1-44			electroplating	Au	?	?		current: ? mA thickness: 4.5 µm area: ? cm² spin bar: ? rpm
1-45			rinse	H₂O
1-46			dry	N₂
1-47			remove PR	ACE IPA		30 s 30 s
1-48			dry	N₂
1-49			descum	plasma etcher w/ O₂		1 min	250 mT	power: 100 W
1-50			remove Ti	HF:DI H₂O (1:10)		5 s
1-51			rinse	H₂O
1-52			dry	N₂
1-53			remove Au (2000 Å)	?		2 min
1-54			rinse	H₂O
1-55			dry	N₂
1-56			remove Ti	HF:DI H₂O (1:10)		5 s
1-57			rinse	H₂O
1-58			dry	N₂
1-59	Lithography II: Definition of Slots on Bottom of Wafer 1	wafer 1 w/ metallized bottom	adhesion promoter	HMDS		30 s		3500 rpm	wafer 1 w/patterned PR for slots on bottom
1-60			wait			10 s
1-61			positive PR	1813		30 s		3500 rpm thickness: ~1.5 µm
1-62			softbake		105	1 min		softbake on hotplate
1-63			mask alignment
1-64			exposure			6 s
1-65			development	MP 351:DI H₂O (1:5)		17 s
1-66			rinse	H₂O
1-67			dry	N₂
1-68			hardbake		130	1 min		hardbake on hotplate
1-69	Opening of Slots on Bottom of Wafer 1	wafer 1 w/ patterned PR for slots on bottom	etch Au	?		?			wafer 1 w/ microstrip lines and slots
1-70			rinse	H₂O
1-71			dry	N₂
1-72			etch Ti	HF:DI H₂O (1:10)		5 s
1-73			rinse	H₂O
1-74			dry	N₂
1-75			remove PR	ACE IPA		30 s 30 s
1-76			dry	N₂
1-77			descum	plasma etcher w/ O₂		1 min	250 mT	power: 100 W
Wafer 2: Cavity Wafer
2-1	Piranha Etch	plain wafer 2	etch bath	H₂O₂:H₂SO₄ (1:1)	120	10 min			cleaned wafer 2
2-2			rinse	H₂O		~15 min
2-3			dry	N₂
2-4	Lithography I: Cavity	cleaned wafer 2	adhesion promoter	HMDS		30s		3500 rpm	wafer 2 w/ PR patterned for cavity
2-5			wait			10 s
2-6			positive PR	1827		30 s		3500 rpm thickness: ~3 µm
2-7			softbake		105	1 min		softbake on hotplate
2-8			mask alignment
2-9			exposure			6 s
2-10			development	MP 351:DI H₂O (1:5)		25 s
2-11			rinse	H₂O
2-12			dry	N₂
2-13			hardbake		130	1 min		hardbake on hotplate
2-14	Opening of Cavity	wafer 2 w/ PR patterned for cavity	SiO₂ etch	BHF		8 min		rate: 1000 Å/min	wafer 2 w/ opened cavity
2-15			rinse	H₂O
2-16			dry	N₂
2-17			remove PR	ACE IPA		30 s 30 s
2-18			dry	N₂
2-19			Si etch	TMAH/H₂O (22wt%)	90	~ 8.3 h		rate: 1 µm/min etch all way through wafer
2-20			rinse	H₂O
2-21			dry	N₂
2-22	Metallization	wafer 2 w/ opened cavity	evaporation	Ti 500 Å Al 15000 Å Ti 500 Å Au 3000 Å			<1*10^-6 Torr		wafer 2 w/ metallized cavity
Wafer 3: Bottom Covering
3-1	Piranha Etch	plain wafer 3	etch bath	H₂O₂:H₂SO₄ (1:1)	120	10 min			cleaned wafer 3
3-2			rinse	H₂O		~15 min
3-3			dry	N₂
3-4	Metallization	cleaned wafer 3	evaporation	Ti 500 Å Al 15000Å Ti 500 Å Au 3000 Å			<1*10^-6 Torr		wafer 3 w/ metallized top side
Sandwich 1: Wafers 2 & 3 Bonded Together
4-1	Bonding	a) wafer 2 w/ metallized cavity b) wafer 3 w/ metallized top side	bonding layer	silver epoxy				applied to backside of wafer 2	wafers 2 & 3 bonded
4-2			bonding layer	silver epoxy				applied to top of wafer 3
4-3			place wafer 2 on top of wafer 3
4-4			place both between glass slides
4-5			place glass slides w/ wafers on hotplate
4-6			apply weights on top of glass plates
4-7			bonding		130	15 min
4-8			cool down		to rm. temp.
4-9	Sealing	wafers 2 & 3 bonded	rinse	ACE IPA					sandwich 1
4-10			dry	N₂
4-11			place on hotplate
4-12			bake		130	1 min		until completely dry
4-13			protect alignment marks					by covering w/ small pieces of Si adhered to wafer w/ PR
4-14			evaporation	Al 4000 Å Au 5000 Å			<1*10^-6 Torr
4-15			remove covering of alignment marks	ACE IPA		30 s 30 s
4-16
Sandwich 2: Wafer 1 & Sandwich 1 Bonded Together
5-1	Bonding	a) wafer 1 w/ microstrip lines and slots b) sandwich 1	bonding layer	silver epoxy				applied to bottom of wafer 1 and around cavity on sandwich 1	filter (final product)
5-2			fix wafer 1 on vacuum chuck of electrostatic bonding machine
5-3			place sandwich 1 on hotplate beneath chuck
5-4			alignment
5-5			lower chuck w/ wafer 1 on sandwich
5-6			bonding		150	10 min
5-7			cool down		to rm. temp.