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General Process Information

Processing using Spin Coater: Gamma UV is divided into three parts:

HMDS priming
Spin coating
Soft baking

Features of Spin Coater: Gamma UV

Cassette-to-cassette wafer handling
In-line HMDS priming

HMDS priming

The process of HMDS priming on Spin Coater: Gamma UV consists of five steps:

Dehydration
HMDS injection
Reaction
Purging
Cooling

The top and bottom heaters of the VPO module are typically set to 120°C. The wafer is baked under a low vacuum (~0.35 bar) in order to heat and dehydrate the wafer before HMDS application. The HMDS is injected into the process chamber using nitrogen as a carrier gas. 10 liters per minute of dry nitrogen is bubbled through liquid HMDS before flowing into the chamber. The injection lasts until ambient pressuer is reached in the chamber. After the reaction time, the chamber is purged using nitrogen. Finally, the wafer is cooled on the cool plate.

The contact angle after HMDS priming is a function of the priming temperature, the priming time, and the surface condition of the wafer. The condition of the substrate surface is again a function of the substrate type, the substrate history, and the effectiveness of the dehydration step. Since the vapor pressure of water at the chamber temperature is much higher than the dehydration pressure, similarly the boiling point of water at the dehydration pressure is well below the chamber temperature, the dehydration can probably be considered to be quite effective. However, for thick oxides, transport effects may cause the 30s dehydration time to be insufficient to dehydrate the surface sufficiently.

Spin coating

The process of spin coating on Spin Coater: Gamma UV consists of a selection of the following steps:

Acceleration to a low spin speed if dynamic dispense is used
Resist dispense
Spin-off
Backside rinse using PGMEA

The wafer is first centered on the spindle chuck and held in place by vacuum. If static dispense is specified in the process, the spindle remains static during the ensuing resist dispense. In the case of dynamic dispense, the spindle is accelerated to a low spin speed before the resist is dispensed. 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. The resist is dispensed through the dispense arm, positioned over the center of the wafer. The resist pump administers a volume of resist which depends on the substrate size.

The spin-off cycle determines the thickness of the resist coating. 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.

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 soft bake 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 dissolves the resist and washes it away. After the rinse, a short spin dries the wafer before the soft bake. Backside rinse may be done as part of the spin-off step(s). During the backside rinse solvent inevitably creeps onto the front side of the wafer, and may remove the resist coating on the edge of the wafer. As an alternative to backside rinse, a wafer which is left dirty on the backside by the spin coat process may be soft baked in proximity in order to protect the hotplate from contamination. This leaves front side coating intact, but also leaves the backside dirty.

Soft baking

After spin coating, the solvent in the resist formulation must be evaporated in a baking step in order to solidify the resist. This soft bake 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. The hotplate temperatures of the baking modules of Spin Coater: Gamma UV are set at temperatures relevant to the resist used, typically 90-110°C. After baking, the wafer is cooled for 20 seconds on the cool plate.

Standard Processes

HMDS priming

The standard HMDS priming process has been developed to mimic the behavior of the IMTEC Star2000 HMDS oven, which produces a contact angle of 81-82° on an oxidized silicon surface. The fast HMDS priming has been developed to have a process time of approximately one minute, in order to match the process time of typical coating and softbaking processes. General information on HMDS priming can be found here.

Sequence names, process parameters, and test results (Sequence no. 0000-0999):

(0401) DCH 100mm HMDS Standard
(0601) DCH 150mm HMDS Standard

VPO temperature: 120°C
Process parameters: 30s vacuum bake @ -0.67 bar, HMDS injection, 90s reaction @ ambient, 20s cooling @ 21°C.

Test results:

Substrate	Contact angle	Test date	Tester initials	Comments
Si with native oxide	78±1°	28/5 2015	taran	average of three measurements on three samples from three different days
110 nm oxide			taran	average of nine measurements (three measurements on three different samples)
Borofloat (glass)			taran	average of three measurements on one sample

(0402) DCH 100mm HMDS Fast
(0602) DCH 150mm HMDS Fast

VPO temperature: 120°C
Process parameters: 30s vacuum bake @ -0.67 bar, HMDS injection, 15s reaction @ ambient, 20s cooling @ 21°C.

Test results:

Substrate	Contact angle	Test date	Tester initials	Comments
Si with native oxide	70±1°	28/5 2015	taran	average of three measurements on three samples from three different days
110 nm oxide			taran	average of nine measurements (three measurements on three different samples)
Borofloat (glass)			taran	average of three measurements on one sample

AZ MiR 701 (29cps) coating

Spin coating of standard thicknesses (1.3 - 2.5 µm) of AZ MiR 701 (29cps) on Spin Coater: Gamma UV is divided into two or three steps: HMDS priming (optional), spin coating, and soft baking. The HMDS priming is equal to the HMDS fast process. Spin coating uses dynamic dispense of resist at 800 rpm, using a volume of 3 ml for 100 mm substrates, and 5 ml for 150 mm substrates, respectively. The dispense is followed by spin-off at a thickness dependent spin speed for 30 seconds. The wafer is decelerated at 2000 rpm/s before stopping. Soft baking is done at 90°C for 60s. As MiR 701 has a tendency to produce "cotton candy" on the edges, soft baking is performed in 1 mm proximity.

In order to achieve thicker coatings of AZ MiR 701 (29cps) while minimizing edge bead problems, a method of waiting before spin-off is used on Spin Coater: Gamma UV. The spin coating process consists of three steps: dispense, waiting, and spin-off. The first step is dynamic dispense of resist at 800 rpm, using a volume of 3 ml for 100 mm substrates, and 5 ml for 150 mm substrates, respectively. In the waiting step the resist is "dried" at low spin speed without exhaust (in practice the exhaust is opened briefly every 15s in order to avoid triggering the exhaust alarm). The final spin-off step is short, but at relatively high spin speed, with backside rinse the first half of the time. Soft baking is done at 90°C for 90s. Contact baking is used since the backside is clean. The coating may be affected by the backside rinse at the very edge of the wafer, something which should be considered if the resist is used as an etch mask.

Sequence names, process parameters, and test results (Sequence no. 1000-1999):

(1410) DCH 100mm MiR 701 1.5um
(1411) DCH 100mm MiR 701 1.5um HMDS
(1610) DCH 150mm MiR 701 1.5um
(1611) DCH 150mm MiR 701 1.5um HMDS

Spin-off: 4600 rpm.

Substrate	Thickness	Uniformity (+/-)	Test date	Tester initials	Comments
Silicon with native oxide	1.513 µm	0.6%	26/3 2015	taran	4" wafer, no HMDS. 9 points on one wafer, exclusion zone 5mm
Silicon with native oxide	1.509 µm	0.3%	4/11 2015	taran	4" wafer, no HMDS. 9 points on one wafer, exclusion zone 5mm

(1420) DCH 100mm MiR 701 2um
(1421) DCH 100mm MiR 701 2um HMDS
(1620) DCH 150mm MiR 701 2um
(1621) DCH 150mm MiR 701 2um HMDS

Spin-off: 2600 rpm.

Substrate	Thickness	Uniformity (+/-)	Test date	Tester initials	Comments
Silicon with native oxide	2.019 µm	1.5%	26/3 2015	taran	4" wafer, no HMDS. 9 points on one wafer, exclusion zone 5mm
Silicon with native oxide	2.000 µm	0.5%	4/11 2015	taran	4" wafer, no HMDS. 9 points on one wafer, exclusion zone 5mm

(1440) DCH 100mm MiR 701 4um
(1441) DCH 100mm MiR 701 4um HMDS
(1640) DCH 150mm MiR 701 4um
(1641) DCH 150mm MiR 701 4um HMDS

Waiting: 75s @ 600 rpm. Spin-off: 10s @ 3000 rpm.

Substrate	Thickness	Uniformity (+/-)	Test date	Tester initials	Comments
Silicon with native oxide	3.992 µm	0.7%	26/3 2015	taran	4" wafer, no HMDS. 9 points on one wafer, exclusion zone 5mm
Silicon with native oxide	4.059 µm	0.7%	4/11 2015	taran	4" wafer, no HMDS. 9 points on one wafer, exclusion zone 5mm

AZ nLOF 2020 coating

Spin coating of standard thicknesses (1.5 - 3 µm) of AZ nLOF 2020 on Spin Coater: Gamma UV is divided into two or three steps: HMDS priming (optional), spin coating, and soft baking. The HMDS priming is equal to the HMDS fast process. Spin coating uses dynamic dispense of resist at 800 rpm, using a volume of 3 ml for 100 mm substrates, and 5 ml for 150 mm substrates, respectively. The dispense is followed by spin-off at a thickness dependent spin speed for 30 seconds. The wafer is decelerated at 2000 rpm/s before stopping. Soft baking is done at 110°C for 60s.

In order to achieve thicker coatings of AZ nLOF 2020 while minimizing edge bead problems, a method of waiting before spin-off is used on Spin Coater: Gamma UV. The spin coating process consists of three steps: dispense, waiting, and spin-off. The first step is dynamic dispense of resist at 800 rpm, using a volume of 3 ml for 100 mm substrates, and 5 ml for 150 mm substrates, respectively. In the waiting step the resist is "dried" at low spin speed without exhaust (in practice the exhaust is opened briefly every 15s in order to avoid triggering the exhaust alarm). The final spin-off step is short, but at relatively high spin speed, with backside rinse the first half of the time. Soft baking is done at 110°C for 120s. Contact baking is used since the backside has been cleaned. The coating may be affected by the backside rinse at the very edge of the wafer, something which should be considered if the resist is used as an etch mask.

Sequence names, process parameters, and test results (Sequence no. 2000-2999):

(2410) DCH 100mm nLOF 2020 1.5um
(2411) DCH 100mm nLOF 2020 1.5um HMDS
(2610) DCH 150mm nLOF 2020 1.5um
(2611) DCH 150mm nLOF 2020 1.5um HMDS

Spin-off: 6000 rpm.

Substrate	Thickness	Uniformity (+/-)	Test date	Tester initials	Comments
Silicon with native oxide	1.559 µm	0.4%	27/3 2015	taran	4" wafer, no HMDS. 9 points on one wafer, exclusion zone 5mm
Silicon with native oxide	1.572 µm	0.8%	4/11 2015	taran	4" wafer, with HMDS. 9 points on one wafer, exclusion zone 5mm

(2420) DCH 100mm nLOF 2020 2um
(2421) DCH 100mm nLOF 2020 2um HMDS
(2620) DCH 150mm nLOF 2020 2um
(2621) DCH 150mm nLOF 2020 2um HMDS

Spin-off: 3300 rpm.

Substrate	Thickness	Uniformity (+/-)	Test date	Tester initials	Comments
Silicon with native oxide	2.018 µm	0.5%	16/3 2015	taran	SAT results. 4" wafer, with HMDS. 5 wafers measured: thickness is average of all 5; uniformity is worst case. 9 points on each wafer, exclusion zone 5mm.
Silicon with native oxide	2.032 µm	0.8%	16/3 2015	taran	SAT results. 6" wafer, with HMDS. 5 wafers measured: thickness is average of all 5; uniformity is worst case. 13 points on each wafer, exclusion zone 5mm.
Silicon with native oxide	2.064 µm	0.8%	4/11 2015	taran	4" wafer, with HMDS. 9 points on one wafer, exclusion zone 5mm

(2440) DCH 100mm nLOF 2020 4um
(2441) DCH 100mm nLOF 2020 4um HMDS
(2640) DCH 150mm nLOF 2020 4um
(2641) DCH 150mm nLOF 2020 4um HMDS

Waiting: 45s @ 600 rpm. Spin-off: 10s @ 3500 rpm.

Substrate	Thickness	Uniformity (+/-)	Test date	Tester initials	Comments
Silicon with native oxide	4.076 µm	0.7%	27/3 2015	taran	4" wafer, no HMDS. 9 points on one wafer, exclusion zone 5mm
Silicon with native oxide	4.131 µm	0.5%	4/11 2015	taran	4" wafer, with HMDS. 9 points on one wafer, exclusion zone 5mm

AZ 5214E coating

Spin coating of standard thicknesses (1.5 - 3 µm) of AZ nLOF 2020 on Spin Coater: Gamma UV is divided into two or three steps: HMDS priming (optional), spin coating, and soft baking. The HMDS priming is equal to the HMDS fast process. Spin coating uses dynamic dispense of resist at 800 rpm, using a volume of 3 ml for 100 mm substrates, and 5 ml for 150 mm substrates, respectively. The dispense is followed by spin-off at a thickness dependent spin speed for 30 seconds. The wafer is decelerated at 2000 rpm/s before stopping. Soft baking is done at 90°C for 60s.

In order to achieve thicker coatings of AZ 5214E while minimizing edge bead problems, a method of waiting before spin-off is used on Spin Coater: Gamma UV. The spin coating process consists of three steps: dispense, waiting, and spin-off. The first step is dynamic dispense of resist at 800 rpm, using a volume of 3 ml for 100 mm substrates, and 5 ml for 150 mm substrates, respectively. In the waiting step the resist is "dried" at low spin speed without exhaust (in practice the exhaust is opened briefly every 15s in order to avoid triggering the exhaust alarm). The final spin-off step is short, but at relatively high spin speed, with backside rinse the first half of the time. Soft baking is done at 100°C for 90s in 1mm proximity. The coating may be affected by the backside rinse at the very edge of the wafer, something which should be considered if the resist is used as an etch mask.

Sequence names, process parameters, and test results (Sequence no. 3000-3999):

(3410) DCH 100mm 5214E 1.5um
(3411) DCH 100mm 5214E 1.5um HMDS
(3610) DCH 150mm 5214E 1.5um
(3611) DCH 150mm 5214E 1.5um HMDS

Spin-off: 4500 rpm.

Substrate	Thickness	Uniformity (+/-)	Test date	Tester initials	Comments
Silicon with native oxide	1.500 µm	0.6%	20/3 2015	taran	SAT results. 4" wafer, with HMDS. 5 wafers measured: thickness is average of all 5; uniformity is worst case. 9 points on each wafer, exclusion zone 5mm.
Silicon with native oxide	1.507 µm	1.0%	20/3 2015	taran	SAT results. 6" wafer, with HMDS. 5 wafers measured: thickness is average of all 5; uniformity is worst case. 13 points on each wafer, exclusion zone 5mm.

(3420) DCH 100mm 5214E 2.2um
(3421) DCH 100mm 5214E 2.2um HMDS
(3620) DCH 150mm 5214E 2.2um
(3621) DCH 150mm 5214E 2.2um HMDS

Spin-off: 2100 rpm.

Substrate	Thickness	Uniformity (+/-)	Test date	Tester initials	Comments
Silicon with native oxide	2.201	0.5%	20/3 2015	taran	4" wafer, no HMDS. 9 points on one wafer, exclusion zone 5mm

(3440) DCH 100mm 5214E 4.2um
(3441) DCH 100mm 5214E 4.2um HMDS
(3640) DCH 150mm 5214E 4.2um
(3641) DCH 150mm 5214E 4.2um HMDS

Waiting: 60s @ 600 rpm. Spin-off: 10s @ 3500 rpm.

Substrate	Thickness	Uniformity (+/-)	Test date	Tester initials	Comments
Silicon with native oxide	4.171 µm	0.7%	20/3 2015	taran	4" wafer, no HMDS. 9 points on one wafer, exclusion zone 5mm
Silicon with native oxide	4.194 µm	0.5%	20/3 2015	taran	6" wafer, no HMDS. 13 points on one wafer, exclusion zone 5mm

Syringe processes

AZ 4562 coating (syringe)

Spin coating of standard thicknesses (5 - 10 µm) of AZ 4562 dispensed from syringe on Spin Coater: Gamma UV is divided into two steps: Spin coating, and soft baking. The spin coating uses dynamic dispense of resist at 300 rpm, using a volume of 3 ml for 100 mm substrates, and 6 ml for 150 mm substrates, respectively. The dispense is followed by spin-off at a thickness dependent spin speed for 30 seconds with backside rinse. The wafer dried at 800 rpm for 15s before stopping. Soft baking is done at 100°C in 1 mm proximity for a thickness dependent time. The coating may be affected by the backside rinse at the very edge of the wafer, something which should be considered if the resist is used as an etch mask.

Sequence names, process parameters, and test results (Sequence no. 4000-4999):

(4462) DCH 100mm 4562 6.2um
(4662) DCH 150mm 4562 6.2um

Spin-off: 5165 rpm. Soft bake: 100s.

Substrate	Thickness	Uniformity (+/-)	Test date	Tester initials	Comments
Silicon with native oxide	6.209 µm	1.0%	19/3 2015	taran	SAT results. 4" wafer, no HMDS. 5 wafers measured: thickness is average of all 5; uniformity is worst case. 9 points on each wafer, exclusion zone 5mm.
Silicon with native oxide	6.224 µm	0.7%	19/3 2015	taran	SAT results. 6" wafer, no HMDS. 3 wafers measured: thickness is average of all 3; uniformity is worst case. 13 points on each wafer, exclusion zone 5mm.

(4410) DCH 100mm 4562 10um
(4610) DCH 150mm 4562 10um

Spin-off: 2000 rpm. Soft bake: 300s.

Substrate	Thickness	Uniformity (+/-)	Test date	Tester initials	Comments
Silicon with native oxide	9.982 µm	0.4%	20/3 2015	taran	4" wafer, no HMDS. 9 points on one wafer, exclusion zone 5mm.

AZ "5206E" coating (syringe)

!SECTION UNDER CONSTRUCTION!

Spin coating of AZ 5206E (AZ 5214E 1:1 by volume in PGMEA) dispensed from syringe on Spin Coater: Gamma UV is divided into three steps: HMDS priming, spin coating, and soft baking. The HMDS priming is equal to the HMDS fast process. The spin coating uses dynamic dispense of resist at 800? rpm, using a volume of 1.5 ml for 100 mm substrates. The dispense is followed by spin-off at a thickness dependent spin speed for 30 seconds. The thickness range is approximately 0.4-0.6µm. Soft baking is done at 90°C for 60s.

Sequence names, process parameters, and test results (Sequence no. 4000-4999):

(4405) 100mm 5206E 0,5um HMDS

Spin-off: 2200 rpm, but likely to change with each new mix of resist.

Substrate	Thickness	Uniformity (+/-)	Spin-off speed	Test date	Tester initials	Comments
Silicon with native oxide	0.49 µm	0.9%	2200 rpm	23/4 2018?	taran	4" wafer, no HMDS. 9 points measured, exclusion zone 5mm.
Silicon with native oxide	0.54	0.4%	2200? rpm	30/1 2019	taran	4" wafer, with HMDS. 9 points measured, exclusion zone 5mm.