5.12 The Process viewer

L1 Phenomenon

Thirty steps take a powder charge to a fibered thin-film LN modulator: crystal, wafer, LNOI, then one of two device routes and the back end. Play it forward or backward, step, or scrub; the cross-section follows, and the HUD lists each step's parameters with reported, derived, or template status. Analog marks a value taken from a paper other than the route's anchor, or from LiTaO₃.

Process viewer: x-cut TFLN Mach-Zehnder modulator, charge to fibered chip01/23

t 0.00

#	STEP	TOOL	T_PROC	STATUS MIX
01	Weigh and react Li2CO3 + Nb2O5 to a congruent charge	crucible charge	n/a	1r 3d 0t 1n a1
02	Melt the charge	Cz puller	n/a	1r 0d 1t 1n a1
03	Czochralski growth (seed, neck, shoulder, body, tail)	Cz puller	55–110 h	5r 2d 2t 0n a5
04	Anneal and pole the boule to a single domain	poling furnace	n/a	1r 0d 1t 2n a1
05	Orient, flat, and slice into x-cut wafers	wire saw	n/a	2r 0d 1t 2n a1
06	Lap and polish (optical grade)	CMP polisher	n/a	0r 0d 0t 1n
07	Prepare the handle wafer (Si with thermal SiO2)	oxidation furnace	n/a	2r 0d 0t 1n
08	He+ implantation into the LN donor	ion implanter	n/a	6r 0d 1t 1n a6
09	Clean, plasma-activate, flip, and bond donor to handle at room temperature	wafer bonder	n/a	4r 0d 0t 0n a4
10	Strengthening anneal, then split at the implanted plane	anneal oven	n/a	4r 1d 0t 0n a4
11	Edge removal and CMP of the split surface to target thickness	CMP polisher	n/a	3r 1d 2t 0n a2
12	Recovery anneal of the film (wafer supplier step)	anneal oven	n/a	0r 0d 0t 1n
13	PECVD SiO2 hard mask	PECVD	n/a	1r 0d 0t 1n
14	Spin ARC and DUV photoresist	spin coater	n/a	2r 0d 0t 1n
15	DUV stepper exposure, step-and-repeat	stepper	< 1 min	4r 1d 0t 0n
16	Develop; etch ARC (Ar/O2) and SiO2 (C3F8)	RIE	n/a	2r 0d 0t 0n
17	Ar ICP-RIE of LN (ridge)	ICP RIE	12.5 min	6r 0d 1t 0n a2
18	Strip resist and SiO2 hard mask in HF	wet bench	n/a	1r 0d 0t 1n
19	PECVD SiO2 cladding	PECVD	n/a	1r 0d 0t 0n
20	Au traveling-wave electrodes by lift-off	e-beam evaporator	n/a	4r 0d 0t 1n a4
21	Dice and polish facets	dicing saw	n/a	0r 0d 1t 1n
22	Align and attach fibers to edge couplers	fiber aligner	n/a	1r 0d 0t 1n a1
23	RF probe or wire bond to the electrode pads	RF probe	n/a	0r 0d 0t 1n

Weigh and react Li2CO3 + Nb2O5 to a congruent charge

                                                
                                                
                                                
                                                
                                                
                                                
                                                
                                                
                                                
                                                
                                                
                                                
                                                
                                                
                                                
                                                
                                                
                                                
U                                              U
U                                              U
U                                              U
U                                              U
U::::::::::::::::::::::::::::::::::::::::::::::U
UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU

boule scale: crystal 153 mm × 110 mm to scale; 1 row = 10 mm

U crucible: powder charge

Step	01/23
Route	Ridge, DUV + SiO2 mask (Luke 2020)
Equipment	crucible charge: crucible with powder charge
Process time	n/a not reported	n/a
composition Li₂O	48.45 mol%	reportedanalog
Li₂CO₃ per kg LN	0.25 kg/kg	derived
Nb₂O₅ per kg LN	0.899 kg/kg	derived
CO₂ released per kg LN	0.149 kg/kg	derived
calcination temperature	n/a	n/a

No time profile for this step.

Badges: reported (anchor or analog paper at the locator), derived (computed from other step values), template (not reported; illustrative), n/a (not reported, not drawn). Playback: 6 s per step at 1x; real process time in the HUD. Stepper fields per 100 mm wafer: 6 (derived).

01/23Crystal

Weigh and react Li2CO3 + Nb2O5 to a congruent charge

2D cross-section; no 3D model for this step

cruciblepowder charge

boule scale: crystal 153 mm × 110 mm to scale; 1 row = 10 mm.

Badges: reported anchor or analog paper at the locator, derived computed from other step values, template not reported, illustrative; n/a: not reported, not drawn. Status mix: reported, derived, template, n/a, and analog count. Playback 6 s per step at 1×; real process time in the HUD. Stepper fields per 100 mm wafer: 6 (derived). Keys with the viewer focused: space, arrows, shift+arrows, [ ].

L2 Routes and provenance

30 steps, 2 routes

Device routes and anchor papers

Route	Anchor	Why this anchor	Filled by analog or template
Ridge, DUV + SiO2 mask	Luke et al. 2020 P	one paper reports the full wafer-scale patterning and cladding sequence (DUV, SiO₂ hard mask, Ar ICP-RIE, HF strip, PECVD cladding) on 4- and 6-inch x-cut LNOI	electrodes from Kharel et al. 2021 P, same group; facets template
Strip, DUV + DLC mask	Li et al. 2023 P	one paper reports DUV, DLC hard mask, Ar IBE, SC-1 redeposition clean, Ti/Au lift-off and etched facets	no cladding stated (drawn uncladded); Si₃N₄ and DLC stack thicknesses from a LiTaO₃ paper P
Shared front end	none	both anchor papers used commercial LNOI, so crystal growth and LNOI formation are composite	every front-end value is an analog or template

Parameter status counts

Route	Steps	Reported	of which analog	Derived	Template	n/a	Total
Ridge, DUV + SiO2 mask	23	52	32	10	10	37	109
Strip, DUV + DLC mask	21	49	26	9	8	36	102

Counts include each step's process time. n/a: not reported and not drawn. reported derived template

Materials

Quantity	Value	Source; status	Note
LN display index	2.21	S	n_o at 1550 nm; single display index of the 3D material
LN edge reflectance F₀	0.142	derived	((n − 1)/(n + 1))² with n = 2.21
LN tint	pale straw	template	not sourced
DLC	a-C:H, up to 5% sp³	P	Raman D 1312.4, G 1541.0 cm⁻¹

L3 Engine and models

deterministic f(route, step, t)

Every view is a pure function of route, step and t in [0, 1]: reverse play, stepping and scrubbing are evaluations at other (step, t), so forward and backward runs give identical frames.
Each step plays for 6 s at 1× (0.5× to 4×); the HUD shows the real process time where the flow reports or derives one, otherwise n/a.
Illustrative z-map, frozen per step: Si handle 4 rows, oxide 3 rows, donor bulk 8 rows, films at 1 row = 0.15 µm, so untouched bodies keep their height while thinned bodies shrink. True scale: one linear scale; a 600 nm film on 4.7 µm SiO₂ on 500 µm Si is 0.12% of the stack and falls below one row.
Crystal axes: x-cut film with X normal and Z lateral; after the bond the donor's +X points down into the bond and +Z reverses on screen.
3D (VISUAL): the scene covers LNOI formation (steps 7 to 12) and the first lithography steps (hard mask, coat, exposure); the camera keeps the reader's orbit and re-targets only at flip, split and scale changes. CMP is drawn face-up so the film stays visible; production CMP holds the wafer face-down. Other steps show the 2D cross-section.
Keys with the viewer focused: space play or pause, left/right move t, shift+left/right step, [ and ] speed. The address bar keeps route, step and t, so a link reopens the viewer at the same point.

Physical models per step

Step	Model	Status of inputs
3 pull	L(t) = v t at the 1.5 mm/h midpoint; rotation at the rate midpoint	reported (analog, review table); seed orientation and cone angles template
8 implant	He plane at the reported 0.68 µm peak; width template	centre reported (analog); no range table, width template
9 bond	rigid flip about the donor's in-plane Y axis; contact wave from the centre pin	method reported (analog); wave speed template
10 split	T(t) ramp to about 230 °C; residual donor lifts	temperatures reported (analog); time axis template
11 CMP	Preston dz/dt = K_p P v from 680 to 600 nm; 8 mm rim	K_p template; edge exclusion reported (analog)
15 expose	serpentine step-and-repeat of 22 × 22 mm fields; field count derived	reported (anchor) and derived
17 / 16 etch	depth(t) = R t; sidewall from mask recession, drawn at the reported angle	depth, angle, selectivity reported; rate analog or n/a; redeposition template
electrodes	line-of-sight deposition and lift-off	thickness reported

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