PROCESSING GUIDELINES FOR:
SU-8 2100 and SU-8 2150
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SU-8 2000is a high contrast, epoxy bad photoresist designed for micromachining and other microelectronic applications, where a thick, chemically and thermally stable image is desired. SU-8 2000 is an improved formulation of SU-8, which has been widely ud by MEMS producers for many years. The u of a faster drying, more polar solvent system results in improved coating quality and increas process throughput. SU-8 2000 is available in twelve standard viscosities. Film thickness of 0.5 to >200 microns can be achieved with a single coat process. The expod and subquently thermally cross-linked portions of the film are rendered insoluble to liquid developers. SU-8 2000 has excellent imaging characteristics and is capable of producing very high aspect ratio structures. SU-8 2000 has very high optical transmission above 360 nm, which makes it ideally suited for imaging near vertical sidewalls in very thick films. SU-8 2000 is best suited for permanent applications where it is imaged, cured and left on the device.
Processing Guidelines
SU-8 2000 photoresist is most commonly expod with conventional UV (350-400 nm) radiation, although i-line (365 nm) is the recommended wavelength. SU-8 2000 may also be expod with e-beam or x-ray radiation. Upon exposure, cross-linking proceeds in two steps (1) formation of a strong acid during the exposure step, followed by (2) acid-catalyzed, thermally driven epoxy cross-lin
king during the post exposure bake (PEB) step. A normal process is: spin coat, soft bake, expo, PEB, followed by develop. A controlled hard bake is recommended to further cross-link the imaged SU-8 2000 structures when they will remain as part of the device. The entire process should be optimized for the specific application.The baline information prented here is meant to be ud as a starting point for determining a process.
SU-8 2000 Features
•High aspect ratio imaging
•0.5 to > 200 μm film thickness in a single coat •Improved coating properties
•Faster drying for incread throughput •Near UV (350-400 nm) processing •Vertical sidewalls
10 um features, 50 um SU-8 2000 coating
Substrate Pretreat
Hard Bake (cure)
optional Removal optional
Process Flow
Coat
Expo
Edge Bead Removal (EBR)
Soft Bake
Develop
Post Exposure Bake (PEB)
Rin and Dry
THICKNESS
SOFT BAKE TIMES (65o C)*(95o C)
microns
minutes
minutes
100 -150
20 -30160 -225530 -45230 -270 5 -745 -60280 -550760 -120
7 -10
Substrate Preparation
To obtain maximum process reliability, substrates should be clean and dry prior to applying SU-8 2000 resist. For best results, substrates should be cleaned with a piranha wet etch (using H 2SO 4& H 2O 2) followed by a de-ionized water rin. Substrates may also be cleaned using reactive ion etching (RIE) or any barrel asher supplied with oxygen. Adhesion promoters are typically not required. For applications that include electroplating, a pre-treatment of the substrate with MCC Primer 80/20 (HMDS) is recommended.
Coat
SU-8 2000 resists are available in twelve standard viscosities. This processing guideline document address two products: SU-8 2100 and SU-8 2150. Figure 1. provides the information required to lect the appropriate SU-8 2000 resist and spin conditions to achieve the desired film thickness.
Recommended Program
1.) Dispen 1ml of resist for each inch (25mm) of substrate diameter.
三年级作文2.) Spin at 500 rpm for 5-10 conds with acceleration of 100 rpm/cond.
3.) Spin at 2000 rpm for 30 conds with acceleration of 300 rpm/cond.
Soft Bake
A level hotplate with good thermal control and uniformity is recommended for u during the Soft Bake step of the process. Convection ovens are not recommended. During convection oven baking, a skin may form on the resist. This skin can inhibit the evolution of solvent, resulting in incomplete drying of the film and/or extended bake times. Table 2. shows the recommended Soft Bake temperatures and times for the various SU-8 2000 products at lected film thickness.
Note: To optimize the baking times/conditions, remove the wafer from the hotplate after the prescribed time and allow it to cool to room temperature. Then, return the wafer to the hotplate. If the film ‘wrinkles’, leave the wafer on the hotplate for a few more minutes. Repeat the cool-down and heat-up cycle until ‘wrinkles’are no longer en in the film.
Table 2. Soft Bake Times
烤箱预热多长时间Table 1. SU-8 2000 Viscosity
SU-8 2000 % Solids Viscosity (cSt) Density (g/ml)2100 75.00 45000 1.2372150 76.75 80000 1.238
Edge Bead Removal (EBR)
During the spin coat process step, a build up of photoresist may occur on the edge of the substrate. In order to minimize contamination of the hotplate, this thick bead should be removed. This can be accomplished by using a small stream of solvent (MicroChem’s EBR PG) at the edge of the wafer either at the top or from the bottom. Most automated spin coaters now have this feature and can be programmed to do this automatically.
By removing any edge bead, the photomask can be placed into clo contact with the wafer, resultin
g in improved resolution and aspect ratio.
Figure 1. SU-8 2000 Spin Speed versus Thickness
050100150200250300350400450500550600650700750800500
1000
1500
2000
2500
3000
3500
Spin Speed (rpm)
F i l m T h i c k n e s s (u m )
SU-8 2150
SU-8 2100n 1.566n 0.00796n 0.00014
SU-8 Cauchy
Coefficients (uncured)
Optical Parameters出月
The dispersion curve and Cauchy coefficients are shown in Figure 3. This information is uful for film thickness measurements bad on ellipsomety and other optical measurements.
站英文孕妇能吃秋葵吗Figure 3. Cauchy Coefficients
Table 3. Exposure Do
Table 4. Exposure Dos for Various Substrates
Post Exposure Bake (PEB)
PEB should take place directly after exposure. Table 5. shows the recommended times and temperatures
Note: After 1 minute of PEB at 95°C, an image of the mask should be visible in the SU-8 2000 photoresist coating. If no visible latent image is en during or after PEB this means that there was insufficient exposure, heating or both.
Table 5. Post Exposure Bake Times
Exposure
To obtain vertical sidewalls in the SU-8 2000 resist, we recommend the u of a long pass filter to eliminate UV radiation below 350 nm. With the recommended filter (PL-360-LP) from Omega Optical ( ) or
Asahi Technoglass filters V-42 plus UV-D35 (jp), an increa in exposure time of approximately 40% is required to reach the optimum exposure do.
Note: With optimal exposure, a visible latent image will be en in the film within 5-15 conds after being placed on the PEB hotplate and not before. An exposure matrix experiment should be performed to determine the optimum dosage.
Development
SU-8 2000 photoresist has been designed for u in immersion, spray or spray-puddle process with MicroChem’s SU-8 developer. Other solvent bad developers such as ethyl lactate and diacetone alcohol may also be ud. Strong agitation is
recommended when developing high aspect ratio and/or thick film structures. The recommended development times for immersion process are given in Table 6. The development times are approximate, since actual dissolution rates can vary widely as a function of agitation
Note: The u of an ultrasonic or megasonic bath may be helpful when developing out via or hole patterns or structures with tight pitch.
Table 6. Development Times for SU-8 Developer
Rin and Dry
When using SU-8 developer, spray and wash the developed image with fresh solution for approximately 10 conds, followed by a cond spray/wash with Isopropyl Alcohol (IPA) for another 10 conds. Air dry with filtered, pressurized air or nitrogen.
Note: A white film produced during IPA rin is an indication of underdevelopment of the unexpod photoresist. Simply immer or spray the substrate with additional SU-8 developer to remove the white film and complete the development process. Repeat the rin step.
The u of an ultrasonic or megasonic bath will energize the solvent and allow for more effective development of the unexpod resist.
Table 7. Physical Propeties
Figure 4. Optical Transmittance
10
2030405060708090100320360400440480520560600640680720760800
Wavelength (nm)
T r a n s m i t t a n c e (%)
Process conditions for Figure 4.Softbake: 5 minutes at 95°C Exposure: 180 mJ/cm 2
Hardbake: 30 minutes at 300°C
Physical Properties
(Approximate values)
Optical Properties
Note:The hard bake step is also uful for annealing any surface cracks that may be evident after development. The recommended step is to bake at 150°C for a couple of minutes. This applies to all film thickness.
Hard Bake (cure )
SU-8 2000 has good mechanical properties. However, for applications where the imaged resist is to be left as part of the final device, a hard bake can be incorporated into the process. This is generally only required if the final device or part is to be subject to thermal processing during regular operation. A hard bake or final cure step is added to ensure that SU-8 2000 properties do not change in actual u. SU-8 2000 is a thermal resin and as such its properties can continue to change when expod to a higher temperature than previously encountered. We recommend using a final bake temperature 10°C higher than the maximum expected device operating temperature. Depending on the degree of cure required, a bake temperature in the range of 150°C to 250°C and for a time between 5 and 30 minutes is typically ud.
Removal
SU-8 2000 has been designed as a permanent, highly cross-linked epoxy material and it is extremely difficult to remove it with conventional solvent bad resist strippers. MicroChem’s Remover PG will swell and lift off minimally cross-linked SU-8 2000. However, if OmniCoat (30-100 nm) has been applied, immersion in Remover PG can effect a clean and thorough Lift-Off of the SU-
8 2000 material. Fully cured or hard baked SU-8 2000 cannot be removed without the u of OmniCoat. To remove minimally cross-linked SU-8 2000, or when using Omnicoat: Heat the Remover PG bath to 50-80°C and immer the substrates for 30-90 minutes. Actual strip time will depend on resist thickness and cross-link density For more information on MicroChem Omnicoat and Remover PG plea e the relevant product data sheets.
To re-work fully cross-linked SU-8 2000: Wafers can be stripped using oxidizing acid solutions such as piranha etch, plasma ash, RIE, lar ablation and pyrolysis.
Plasma Removal
RIE 200W, 80 sccm O2, 8 sccm CF4, 100mTorr, 10°C
Storage
Store SU-8 2000 resists upright and in tightly clod containers in a cool, dry environment away from direct sunlight at a temperature of 40-70°F (4-21°C). Store away from light, acids, heat and sources of ignition. Shelf life is twelve months from date of manufacture.
Disposal
SU-8 2000 resists may be included with other waste containing similar organic solvents to be discarded for destruction or reclaim in accordance with local state and federal regulations. It is the responsibility of the customer to ensure the disposal of SU-8 2000 resists and residues made in obrvance all federal, state, and local environmental regulations.
Environmental, Health and Safety
Consult the product Material Safety Data Sheet before working with SU-8 2000 resists. Handle with care. Wear chemical goggles, chemical gloves and suitable protective clothing when handling SU-8 2000 resists. Do not get into eyes, or onto skin or clothing. U with adequate ventilation to avoid breathing vapors or mist. In ca of contact with skin, wash affected area with soap and water. In ca of contact with eyes, rin immediately with water and flush for 15 minutes lifting eyelids frequently. Get emergency medical assistance.
The information is bad on our experience and is, we believe to be reliable, but may not be complete. We make no guarantee or warranty, expresd or implied, regarding the information, u, handling, storage, or posssion of the products, or the application of any process described herein or the results desired, since the conditions of u and handling of the products are beyond our control.
Disclaimer
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All information contained in any MicroChem product literature reflects MicroChem’s current knowledge on the subject and is, we believe, reliable. It is offered solely to provide possible suggestions for customer’s own experiments and is not a substitute for any testing by customer to determine the suitability of any of MicroChem products for any particular purpo. This information may be subject to revision as new knowledge and experience becomes available, but MicroChem assumes no obligation to update or revi any data previously furnished to a customer; and if currency of data becomes an issue, customer should contact MicroChem requesting updates. Since MicroChem cannot anticipate all variations in actual end us or in actual end-u conditions, it makes no claims, reprentations or warranties, express or implied including, without limitation any warranty of merchantability or fitness for a particular purpo;and customer waives all of the same. MicroChem expressly disclaims any responsibility or liability and assumes no responsibility or liability in connection with any u of this information including, without limitation, any u, handling, storage or posssion of any MicroChem products, or the application of any process described herein or the
results desired or anything relating to the design of the customer’s products. Nothing in this publication is to be considered as a licen to operate under or a recommendation to infringe any
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Caution
This product is not designed or manufactured for, nor is it intended for u in any medical device or for any other medical application. Do not u this product in any medical applications [including, without limitation, any permanent implantation in the human body or any animals (other than laboratory animals ud for experimental purpos), or contact with internal body fluids or tissues] unless otherwi expressly and specifically provided for in a written contract between MCC and the customer. The complete MicroChem Medical Disclaimer Statement is available upon request or on the MicroChem website at
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