Specific Process Knowledge/Lithography/Coaters

Coater Comparison Table

Equipment		Spin Coater: Gamma UV	Spin Track 1 + 2	SSE Spinner DECOMMISSIONED!	Spin Coater: RCD8	Spin Coater: Manual All Resist	Spin Coater: Manual Standard Resists	Spin Coater: Manual All Purpose	Spray Coater
Purpose		In-line substrate HMDS priming Coating and baking of AZ MiR 701 (29cps) AZ nLOF 2020 AZ 5214E	In-line substrate HMDS priming Coating and baking of AZ MiR 701 (29cps) AZ nLOF 2020 Post-exposure baking at 110°C	Coating and baking of AZ5214E AZ4562 E-beam resist (for batches > 25 wafers)	Coating of SU-8 AZ 5214E AZ 4562 AZ MiR AZ nLOF	Coating of all resists	Coating of CSAR ZEP PMMA/MMA HSQ (FOx) AZ 5214E AZ 4562 AZ MiR AZ nLOF	Coating of ESPACER Experimental resists Coating on Experimental substrates	Spraying imprint resist Spraying photoresist Spraying of other solutions
Performance	Substrate handling	Cassette-to-cassette	Cassette-to-cassette	Cassette-to-cassette Edge handling chuck	Single substrate Non-vacuum chuck for fragile substrates	Single substrate Edge handling chuck		Single substrate	Can handle almost any sample size and shape
	Permanent media	AZ MiR 701 (29cps) resist AZ nLOF 2020 resist AZ 5214E resist PGMEA solvent for backside rinse and spinner bowl cleaning	AZ MiR 701 (29cps) resist AZ nLOF 2020 resist PGMEA for backside rinse and edge-bead removal PGMEA for spinner bowl cleaning and vapor tip bath	AZ5214E resist AZ4562 resist Acetone for chuck cleaning Acetone for drip pan	No permanent media	Only manual dispense			No permanent media
	Manual dispense option	syringe dispense	no	2 automatic syringes	yes pneumatic dispense for SU-8 resist				Two syringe pumps
Process parameter range	Spindle speed	10 - 6000 rpm	10 - 9990 rpm	100 - 5000 rpm	10 - 5000 rpm (3000 rpm with non-vacuum chuck)	100 - 5000 rpm	100 - 5000 rpm	100 - 7000 rpm
	Gyrset	no	no	optional	optional (max. speed 3000 rpm)	no	no	no
Substrates	Substrate size	50 mm wafers (tool change required) 100 mm wafers 150 mm wafers 200 mm wafers (tool change required)	100 mm wafers 150 mm wafers (tool change required)	50 mm wafers 100 mm wafers 150 mm wafers	100 mm wafer 150 mm wafer	50 mm wafers 100 mm wafers 150 mm wafers small pieces down to 10x10 mm2	50 mm wafers 100 mm wafers 150 mm wafer small pieces down to 10x10 mm2	50 mm wafers 100 mm wafers 150 mm wafer small pieces down to 3x3 mm2	Any sample(s) that fit inside machine
	Batch size	1 - 25	1 - 25	1 - 24	1	1	1	1	1
	Allowed materials	Silicon Glass	Silicon Glass	All cleanroom materials except III-V materials	All cleanroom materials except III-V materials	III-V materials Si, SiO2, SOI	All cleanroom materials	All cleanroom materials	All chemicals to be spray coated must be approved specifically for spray coating Any non-toxic, non-particulate and non-crosslinking material is likely to be approved

Spin coating

The process of spin coating consists of a selection of the following steps:

• Priming (typically HMDS)
• Acceleration to a low spin speed if dynamic dispense is used
• Resist dispense (static or dynamic)
• Resist spreading at low spin speed
• Spin-off
• Backside rinse (typically during spin-off)
• Edge-bead removal
• Softbake (contact or proximity)

After priming, the wafer is centered on the coater chuck and held in place by vacuum, or in some cases pins. If static dispense is used, the wafer remains static during the ensuing resist dispense. In the case of dynamic dispense, the wafer rotates at low spin speed during the dispense. Using too high spin speed during dispense can cause surface wetting issues, while a too low spin speed causes the resist to flow onto the backside of the wafer. After dispense, a short spin at low spin speed may be used in order to spread the resist over the wafer surface before spin-off.

Spin-off

The spin-off cycle determines the thickness of the resist coating. For a given resist, the thickness is primarily a function of the spin-off speed and the spin-off time, both following an inverse power-law (y=k*x^-a). The acceleration to the spin-off speed also influences the thickness, but the effect is dependent on previous steps. The spin-off is usually a simple spin at one speed, but it may be comprised of several steps at different spin speeds. After spin-off, the wafer is decelerated.

The coated thickness, t, as a function of the spin-off speed, w, follows an inverse power-law, t = k * w^-a. The constant, k, is a function of the resist viscosity and solid content, and the spin-off time. The exponent, a, is dependent on solvent evaporation, and is typically ~½ for UV resists. This means that from the thickness t₁ achieved at spin speed w₁, one can estimate the spin speed w₂ needed to achieve thickness t₂ using the relation:
t₁*w₁^½ = t₂*w₂^½ => w₂ = w₁ * t₁²/t₂².
For thick SU-8, however, a is observed to be ~1 (probably due to the low solvent content and/or the formation of skin). In this case, the relation simply becomes:
t₁*w₁ = t₂*w₂ => w₂ = w₁ * t₁/t₂.

Backside rinse

Dependent on the spin speeds used in the various steps of the spin coating, resist may creep over the edge of the wafer and onto the backside. Also, some resists tend to leave fine strings of resist protruding from the edge of the wafer, or folded onto the backside, an effect sometimes referred to as "cotton candy". This resist will contaminate the softbake hotplate, and thus subsequent wafers with resist. In a backside rinse step, solvent administered through a nozzle to the backside of the wafer while spinning at low or medium spin speed dissolves the resist and washes it away. After the rinse, a short spin at medium spin speed dries the wafer before the softbake. During the backside rinse solvent inevitably creeps onto the front side of the wafer. This effect may be used to dissolve and subsequently remove an edge-bead, but it may also leave the rim of the wafer exposed. As an alternative to backside rinse, a wafer which is left dirty on the backside by the spin coat process may be softbaked in proximity in order to protect the hotplate from contamination. This leaves front side coating intact, but also leaves the backside dirty.

Edge bead

During spin coating, resist builds up at the edge of the wafer due to the change in surface tension at the edge. This phenomenon is called an edge-bead. Dependent on spin coating parameters, the coating may be several times thicker at the edge than in the central area. In a subsequent hard contact exposure step, this edge-bead induces an undesired proximity gap which reduces the lateral resolution, and may even cause the wafer to stick to the mask.

In an edge-bead removal step, solvent administered through a nozzle positioned at the edge of the wafer while spinning at low or medium spin speed dissolves the resist and washes it away. After the removal, a short spin at medium spin speed dries the wafer before the softbake. Dependent on the viscosity (solvent content) of the resist at the point of edge-bead removal, this drying spin may cause the resist to re-flow and create a secondary edge-bead. In some cases, it may be necessary to (partially) softbake the resist before edge-bead removal.

Softbake

After spin coating, the solvent in the resist formulation must be evaporated in a baking step in order to solidify the resist. This softbake can be carried out as a contact bake or a proximity bake. In a contact bake, the wafer is held in close contact to the hotplate surface while resting on shallow bumps only 150µm above the hotplate. In a proximity bake, the wafer is first moved into proximity, e.g. 1mm, of the hotplate surface, then held there (on the lift pins) for the duration of the bake.

Spin coaters at Danchip

Spin Track 1 + 2

Spin Track 1 + 2 in C-1

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Coater comparison table

Spin Track 1 + 2 is an SVG 88 series track system from Rite Track. Each track consists of a HMDS priming module, a spin coating module, and a baking module. In fact, the only difference between the two tracks is the resist used in the spin coating module. Spin Track 1 + 2 is capable of handling 150 mm wafers, as well as 100 mm wafers, but is currently set up for 100 mm wafer processing.

The Spin Track 1 + 2 is controlled using the Recipe Manager software via the touchscreen on the arm attached to the lefthand end of the track. Recipes for the individual modules are developed by Danchip and combined into flows. The user selects a flow (specific to track 1 or 2), and the appropriate recipes will be downloaded and executed on the appropriate track. The other track runs an empty process (no wafers needed), and can unfortunately not be used by a second user while the first user is processing.

The user manual, user APV, and contact information can be found in LabManager

Process information

• General Spin Track 1 + 2 process information
• HMDS priming on Spin Track 1 and 2
• AZ MiR 701 (29cps) coating on Spin Track 1
• AZ nLOF 2020 coating on Spin Track 2
• Post-exposure baking on Spin Track 2

Equipment performance and process related parameters

Spin Track		1	2
Purpose		HMDS priming Spin coating and soft baking Priming, coating, and baking	HMDS priming Spin coating and soft baking Priming, coating, and baking Post-exposure baking
Resist		AZ MiR 701 (29cps) positive tone	AZ nLOF 2020 negative tone
Performance	Coating thickness	1 - 3 µm	1 - 4 µm
	HMDS contact angle	60° - 90°; standard recipe 82° (on SiO2)
Process parameters	Spin speed	10 - 9990 rpm
	Spin acceleration	1000 - 50000 rpm/s
	Hotplate temperature	90°C	110°C
	HMDS priming temperature	50°C
Substrates	Substrate size	100 mm wafers
	Allowed materials	Silicon and glass wafers Film or pattern of all types
	Batch	1 - 25

Spin Coater: Gamma UV

Spin Coater: Gamma UV in E-5

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Coater comparison table

Spin Coater: Gamma UV was installed at Danchip in March 2015. It is a Gamma 2M cluster from Süss MicroTec with spin coating, vapour priming, and baking modules. The system handles 4" and 6" wafers without size conversion, and can be set up to handle 2" or 8".

The coater is equipped with 3 different resists lines:

• AZ MiR 701
• AZ nLOF 2020
• AZ 5214E

and

• 1 syringe, which can be used for various resists.

The processes that are available on the system are developed by Danchip. Upon request, it is possible to establish new processes. Use of the syringe requires special training, and would as a starting point require batches in excess of 20 wafers.

Training video

The user manual, user APV, and contact information can be found in LabManager

Process information

Standard Processes:

• HMDS
• AZ MiR 701
• AZ nLOF 2020
• AZ 5214E

Equipment performance and process related parameters

Purpose		HMDS priming Spin coating of PGMEA based UV resists Spin coating of E-beam resists 1) Soft baking
Resist		AZ MiR 701 (29cps) AZ nLOF 2020 AZ 5214E 100cc syringe dispense
Performance	HMDS contact angle	60 - 80°
	Coating thickness	AZ MiR 701: 1.5-4 µm AZ nLOF 2020: 1.5-5 µm AZ 5214E: 1.5-5 µm AZ 4562: 5-15 µm
Process parameters	Priming temperature	120 °C
	Spin speed	10 - 6000 rpm
	Spin acceleration	10 - 10000 rpm/s
	Hotplate temperature	25 - 200 °C
	Cool plate temperature	21 °C
Substrates	Substrate size	50 mm wafers 1) 100 mm wafers 150 mm wafers 200 mm wafers 1)
	Allowed materials	Silicon and glass
	Batch	1 - 25

¹⁾ Requires tool change.

Spin Coater: RCD8

Spin coater: RCD8 is located in C-1

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Coater comparison table

Spin Coater: RCD8 is a model RCD8 T spin coater from Süss MicroTec with a motorized media arm and Gyrset functionality. It's primary purpose is spin coating of SU-8 resist. However, due to the possibility of using a non-vacuum chuck, the spin coater is also suitable for coating of substrates with e.g. textured backsides or membranes.

The user manual, user APV, and contact information can be found in LabManager

Process information

• Spin coating
• Automatic dispense
• Recipes and templates
• Processing results

Equipment performance and process related parameters

Purpose		Spin coating of SU-8 resists Spin coating of PGMEA based AZ resists Spin coating of wafers with structured backside Edge bead removal
Resist		manual dispense automatic dispense from syringe
Performance	Coating thickness	SU-8 resits: 0.1-200+ µm AZ 5214E: 1.5-3 µm AZ 4562: 8-15 µm AZ MiR 701: 1.5-3 µm AZ nLOF 2020: 2-3.5 µm
Process parameters	Spin speed	Vacuum chuck: 10 - 5000 rpm Non-vacuum chuck: Max. 3000 rpm
	Spin acceleration	10 - 3000 rpm/s Max. 1500 rpm/s with Gyrset
Substrates	Substrate size	100 mm wafers 150 mm wafers
	Allowed materials	All cleanroom materials ?
	Batch	1

Manual Spin Coaters

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Spin Coater: Manual All Resist	Spin Coater: Manual Standard Resists	Spin Coater: Manual All Purpose
Loacted in fumehood in A-5	Located in fumehood in E-5	Located in fumehood in C-1
LabSpin 6, Süss MicroTec	LabSpin 6, Süss MicroTec	WS-650, Laurell
LabManager	LabManager	LabManager

Training video: LabSpin6

Spin curves (LabSpin 6): AZ 5214E‎, AZ nLOF 2020, ZEP 520A‎, FOX-15, AZ 4562‎, CSAR 6200