Spin Coater Dispense Systems and Accessories

Manual or automated dispense

The simplest way to coat is by hand, with a pipette or syringe through the opening in the lid, and plenty of labs start there for trial runs and small volumes. Automated dispense takes the operator out of the timing. The recipe triggers each dispense at a set point in the spin, the valve cuts off cleanly with suckback, and every wafer gets the same volume in the same place. Apogee tools can run several automated dispenses at once, each driven from a dispense control box and supplied with nitrogen or clean dry air at 70 psi (482 kPa).

Disposable syringe dispense (DSD)

The DSD suits research work with expensive or experimental materials, where every millilitre counts and changeovers are frequent. The syringe hub mounts on the lid, and the whole fluid path is disposable, so a change of material takes only a new barrel and needle. It handles viscosities from 1 to 6,000 cP, or up to 12,000 cP with a larger-bore needle, at up to 90 psi, from 30 ml or 55 ml barrels. Suckback is automatic, and an optional piston removes air and cuts waste. Typical materials include SU-8, polyimide, PMMA, S1800 and the AZ series resists. The hub adds about 8″ (20 cm) to the height of the spin coater.

Cartridge dispense

Cartridge dispense sits between the syringe and the pressure can, for R&D and production runs of 74 ml to 946 ml (2.5 oz to 32 oz). A PTFE valve gives adjustable flow rate and suckback, and pistons are available to keep fluid and air apart. The standard valve takes 1 to 3,000 cP at up to 29 psi, and an upgraded valve raises that to 5,000 cP and 90 psi. Solvents, DUV BARCs and most photoresists run well on it, and an in-line filter is an option.

Pressure can dispense

For larger volumes, a stainless steel pressure can feeds the dispense valve from a 1, 2, 3, 5 or 10 gallon reservoir. The wetted parts are PFA and PTFE, the can is passivated 304/316 stainless steel, and there’s a PTFE-lined or PFA-coated version for aggressive chemistry. An empty sensor warns before the can runs dry, and an oversized opening makes refilling straightforward. The standard valve handles 1 to 3,000 cP, and a gravity-fed set-up with an upgraded valve takes up to 10,000 cP. Allow at least 12″ (30 cm) above the can to open the lid.

AccuScan moving-arm dispense

AccuScan puts the dispense nozzles on a programmable arm, so the recipe controls where material lands as well as when. The arm positions to 0.1 mm across a 106 mm working range at speeds up to 50 mm/s. On a spin coater it carries up to three dispenses and handles materials up to 5,000 cP. On a developer it carries two dispenses and an N2 blow-off, for fluids up to 100 cP.

The arm can flush the nozzle in its drip-free park position before each wafer, dispense at the centre or offset from it, scan from centre to edge while dispensing, or move to the edge to strip the edge bead. On a developer, high-pressure spray from the arm helps shift stubborn residues and metal lift-off layers. It’s programmed through DataStream alongside the spin recipe, and it adds 2″ to the top and 9″ to the rear of the process module.

Edge bead removal (EBR)

Spinning leaves a raised bead of resist at the edge of the wafer, which can contaminate handling tools and spoil contact during exposure. EBR applies a solvent such as acetone, IPA, PGME or PGMEA to the edge of the spinning wafer through a manually adjustable nozzle in the bowl, clearing the resist from the perimeter. It runs from a 1 to 10 gallon pressure can, and with AccuScan the arm can place the solvent instead.

Backside rinse (BSR)

Material can wrap round the edge and onto the back of the wafer, where it contaminates chucks and hotplates further down the line. A backside rinse nozzle in the bowl sprays solvent or DI water onto the underside while the wafer spins, clearing resist and developer residue. It takes the same range of solvents as EBR, plus NMP and DI water.

Spray and stream dispense for developing

On a spin developer, developer and DI water go on by spray or by stream. Flat spray nozzles at 110° or 40° give even coverage and faster throughput than immersion or puddle developing, and the nozzles mount directly over the substrate or at 45° from outside its edge. Stream dispense lays developer onto the wafer much like a coating dispense, for puddle processes. Common chemistries include TMAH, MIF developers, DMSO, NMP and DI water. Top and backside DI rinses can run from a pressure can or from house DI water, which needs to be below 30 psi if it’s hard plumbed.

N2 blow-off

Spinning alone doesn’t always dry the centre of a wafer. An N2 blow-off nozzle aims a jet of nitrogen at the centre at the end of the recipe, so the substrate dries evenly and moves on sooner. It’s used mostly on developers and cleaners, and it can ride on the AccuScan arm.