研究所、永久材、MEMS专用GCM 3060

Gersteltec SU-8 series

深圳市芯泰科光电有限公司

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Gersteltec SU-8 series

GCM 3060(Conductive SU8-negative tone photo-epoxy For thin layers)

 General information

SU-8 is an epoxy based, chemically amplified resist system with excellent sensitivity high aspect ratios. The primary applications are Micro-fabricated mechanical structures (MEMS) other Microsystems needed non conductive properties. Adding metallic particles in the SU-8 photoresist results in an enhancement of its electrical conductivity. GCM 3060 offers an electrical conductivity of about 101-3 S.cm-2 

Datasheet parts… 

 1 、Schematics of the process 

 2 、Process description 

 3 、Processing GCM3060 – Overview 

 4 、Troubleshooting 

1 / Schematics of the process

2 / Process description

A typical process consists of 

 - Substrate preparation 

 -  Spin-coating 

 -  Relaxation time to improve the surface uniformity 

 -  Soft Bake 

 -  Exposure to initiate the cross-linking 

 -  Post Exposure bake (PEB), to cross link exposed regions. 

 -  Development 

 -  Rinse & dry 

 -  Hard Bake (or curing-optional) 

 -  Imaged material (optional: in case of moulding) 

 -  Remove (optional: in case of moulding)  

(in chronological order) 

 Put the substrate on a furnace / oven at a minimum of 130 °C for 20 minutes to remove adsorbed water the substrates surface. Alternatively use oxygen plasma for 7min at 500 Watts in a Microwave plasma reactor. This should increase the temperature inside the plasma chamber above 80°C after the 2 firsts minutes. 

 Spread the resist after cooling down the substrates, with a scrapper or by using screen printing method. 

 Softbake the coated substrate in two steps. All the temperature ramps should be about 2°C/min. Firstly increase the temperature room temperature up to 65°C. Then let the substrates at 65°C 5 to 15min (depend on the resist thickness). You can then increase up to 95°C you should let your wafers as much time as necessary that, when holding them with some tweezers there are not printed on the SU8 layer! Then you can switch off the power or decrease temperature until they reach the room temperature.

Expose the coated substrate with the mask in front side mode for very thin films (less than 5 μm). Back side mode is preferentially recommended with the use of an integrated mask between the substrate the conductive photoresist. 

 The exposure dose ranges between 400 600 mJ.cm-2, depending on the structure geometry thickness. More the dose is, more the lateral resolution will be affected. 

 Note: Exposure doses refer to i-line (365nm). A stard mask aligner with a 250W Hg light source has approx. 6-15 mW/cm2 i-line intensity, while in many cases 20-30 mW/cm2 are measured meeting the total (g-, h- i-line) intensity! 

 Ideally you should try some multiple exposure around the given exposure dose given in Exposure curve. In fact your results may not be exactly the same because of the UV lamp parameters. So they have to optimise this exposure dose parameter, simply because your mask aligner is probably not the same. 

 Post Exposure Bake (PEB): after the delay bake the coated substrate at the same temperature profile than for the Soft Bake. (Because this step is very temperature critical furnace baking is not recommended). This step accelerates the cross-linking of the exposed areas making them insoluble in the developer. 

 Develop in PGMEA. When the structure is through-developed (cleared), add another 10% of the time in a cleaned bath of the total development time to finalize the side wall profile. 

 Rinse with Isopropanol. Once there is not any more white traces the development is then finished. Unfortunately, if you add even more than a minute, you would increase the composite layer that should unstuck the substrate. 

 Dry the wafers just letting them at the ambient air, on a wet bench with an appropriate air flow (exhaust).

 Hard-bake: use the same temperature profile than for the Soft Bake, with a final temperature of 120 °C. The electrical conductivity will be enhanced by one decade. 

3 / Processing GCM3060 - Overview

4 / Troubleshooting

White traces after development: This is only because there is still some unexposed SU8 not totally developed. In fact unexposed SU8+Isopropanol makes a white complex that you can find on your wafers. 

 In the other side, just pay attention to not develop to much time. Otherwise you could unstuck the composite layer the substrate.