CYCLOTENE Advanced Electronics Resins (Photo BCB) Processing Procedures for 20µm Photo-BCB Layers Using XUS35078 type 3

Transcription

1 Processing Procedures CYCLOTENE Advanced Electronics Resins (Photo BCB) Processing Procedures for 20µm Photo-BCB Layers Using XUS35078 type 3 Regional Product Availability Introduction Spin Curves North America Europe, Middle East and Africa Latin America Asia-Pacific XUS35078 type 3 is a photosensitive CYCLOTENE Product based on the commercial formulation CYCLOTENE Resin, but with a higher solids content to achieve thicker layers. The following is a summary of the processing characteristics of this product, with an emphasis on its differences from the other products. For more general photo-bcb processing information, please refer to the processing guides, both puddle develop and immersion develop, which can be found on our web site ( Photo-BCB resin XUS35078 type 3 is formulated to a viscosity of approximately 2300 cst. Spin curves of this high viscosity product are shown in Figure 1, using both open and closed coaters. The thicknesses shown in this chart are after hot plate soft bake. The thickness after cure will depend on exposure dose and develop procedure. For a 20µm thick film after cure, a thickness of about 24µm after coat and bake will be needed. Spin curve data was generated on 4 wafers. Thickness measurements were made on a Foothill Instruments KT-22; the thickness reported is the average of 52 points. Soft Bake Exposure Dose The recommended hot plate soft bake temp-erature for a 24µm thick film is 110 C 120 C, for 90 seconds. All of the following data is for exposure on a Suss broad band aligner, and this is the recommended lithography tool. No attempt has been made to expose films in this thickness range on steppers. The exposure of films with a thickness of 24µm after soft bake requires an exposure dose greater than 1000 mj/cm 2, preferably in the range of mj/cm 2. Lower doses will lead to larger film losses during develop, as well as poorer resolution. Lowering the exposure dose below the recommended range also increases the risk of film wrinkling due to swelling. Page 1 of 5 CYCLOTENE Advanced Electronics Resins / Growth Technologies 09/2012, Rev. 0

2 Develop Conditions Two solvent developers are available from Dow: DS3000 and DS2100. DS3000 is designed for a batch immersion process; DS2100 is designed for a puddle process. These developers or processes cannot be interchanged. a) DS3000 develop The developer temperature should be about 38 C 40 C for films of this thickness. The develop time at this temperature will be approximately 10 minutes. Develop time is subject to several variables, so this estimated time may vary. For more details on the immersion develop process, please refer to our immersion develop processing guide. Immersion develop with DS3000 is the preferred method for thick photo-bcb films because of the wider processing latitude. We have not yet optimized the pre-develop bake process for films of this thickness, so develop end point monitors are needed open cover, 120 C bake closed cover, 150 C bake open cover, 110 C bake film thickness (µm) spin speed (rpm) Figure 1. Spin curves for XUS35078 type 3. Thicknesses are after coat and bake. b) DS2100 develop DS2100 developer can be used to produce patterned 20um films, but the process window is smaller than with DS3000. This developer is more aggressive, and can lead to film swelling and wrinkling unless high exposure doses are used, which will affect throughput. For the thicknesses described here, a dose of mj/cm 2 is recommended. Throughput will also be adversely affected in the develop step, as the develop time per wafer can be as much as 4-5 minutes. Cure The recommended cure oven profile is independent of film thickness. The standard 60 minutes at 250 C under inert atmosphere (<100ppm O 2) can be used for a full cure. For lower layers in a multilayer build, a partial cure at 210 C for 40 minutes is recommended. Film thickness after cure is given in Table 1 for different process conditions. As expected, the final film thickness increases as exposure dose increases and decreases as the extent of overdevelop is increased. Page 2 of 5 CYCLOTENE Advanced Electronics Resins / Growth Technologies 09/2012, Rev. 0

3 Descum Resolution A plasma descum after cure is needed to remove polymer residue remaining after the develop step. O2/CF4 or O2/SF6 plasmas are commonly used for this. The residual scum associated with these thick films may be thicker than that usually seen with thinner photosensitive CYCLOTENE Films, so the plasma time may need to be increased. We have been able to open 75µm vias in a 22µm thick film when the exposure was done at a 25µm proximity gap, and we have opened 50µm vias in a 20µm thick film when the exposure gap was 10µm. The feature sizes given above are the mask dimensions. Resolution tends to improve as the exposure dose is increased from 1000 to 2000 mj/cm 2, as is shown in Figure 2. A cross section SEM of a via in a 21µm thick film is shown in Figure 3. Figure 4 shows the coverage and planarization of 8µm high metal lines with 16µm thick photo-bcb. A closed cover coater was used to achieve this degree of planarization. Figure 5 shows an optical micrograph of a patterned via in a 20µm thick photo-bcb film. Table 1. Film thickness after cure. Cured film thickness exposure dose (mj/cm 2 ) initial thickness 26.9µm (a) 50% overdevelop 100% over develop initial thickness 24.2µm (b) 60% overdevelop 80% overdevelop 100% overdevelop (a) soft bake 100 C / 120 seconds (b) soft bake 110 C / 90 seconds Via Opening vs Exposure Dose 20µm Film Thickness, 100% Overdevelop 50um vias 75um vias via opening (µm) exposure dose (mj/cm2) Figure 2. Via resolution (size of via opening at bottom) as a function of exposure dose. Films were exposed on a Suss aligner at a 10µm gap, and developed in DS3000 developer. Page 3 of 5 CYCLOTENE Advanced Electronics Resins / Growth Technologies 09/2012, Rev. 0

4 Figure 3. Cross section of a via. The BCB thickness is 21µm; the via size (mask dimension) is 125µm. Figure 4. Planarization of 8µm high metal lines with 16µm thick photo-bcb. Figure 5. Via in 20µm thick photo-bcb film. The mask dimension was 77µm, and the via opening at the bottom was 50µm for the DS3000 develop. Page 4 of 5 CYCLOTENE Advanced Electronics Resins / Growth Technologies 09/2012, Rev. 0

5 Handling Precautions Before using this product, associated generic chemicals, or the analytical reagents required for its control, consult the supplier's Material Safety Data Sheet (MSDS)/Safety Data Sheet (SDS) for details on material hazards, recommended handling precautions and product storage. CAUTION! Keep combustible and/or flammable products and their vapors away from heat, sparks, flames and other sources of ignition including static discharge. Processing or operating at temperatures near or above product flashpoint may pose a fire hazard. Use appropriate grounding and bonding techniques to manage static discharge hazards. CAUTION! Failure to maintain proper volume level when using immersion heaters can expose tank and solution to excessive heat resulting in a possible combustion hazard, particularly when plastic tanks are used. Storage Disposal Considerations Store products in tightly closed original containers at temperatures recommended on the product label. Dispose in accordance with all local, state (provincial) and federal regulations. Empty containers may contain hazardous residues. This material and its container must be disposed in a safe and legal manner. It is the user's responsibility to verify that treatment and disposal procedures comply with local, state (provincial) and federal regulations. Contact your Dow Electronic Materials Technical Representative for more information. Product Stewardship Customer Notice Dow has a fundamental concern for all who make, distribute, and use its products, and for the environment in which we live. This concern is the basis for our product stewardship philosophy by which we assess the safety, health, and environmental information on our products and then take appropriate steps to protect employee and public health and our environment. The success of our product stewardship program rests with each and every individual involved with Dow products - from the initial concept and research, to manufacture, use, sale, disposal, and recycle of each product. Dow strongly encourages its customers to review both their manufacturing processes and their applications of Dow products from the standpoint of human health and environmental quality to ensure that Dow products are not used in ways for which they are not intended or tested. Dow personnel are available to answer your questions and to provide reasonable technical support. Dow product literature, including safety data sheets, should be consulted prior to use of Dow products. Current safety data sheets are available from Dow. For Industrial Use Only. This information is based on our experience and is, to the best of our knowledge, true and accurate. However, since conditions for use and handling of products are beyond our control, we make no guarantee or warranty, expressed or implied, regarding the information, the use, handling, storage or possession of the products, or the applications of any process described herein or the results sought to be obtained. Nothing herein shall be construed as a recommendation to use any product in violation of any patent rights. Contact: North America: Japan: (+81) Asia: (+852) Europe: (+41) NOTICE: No freedom from infringement of any patent owned by Dow or others is to be inferred. Because use conditions and applicable laws may differ from one location to another and may change with time, Customer is responsible for determining whether products and the information in this document are appropriate for Customer's use and for ensuring that Customer's workplace and disposal practices are in compliance with applicable laws and other government enactments. The product shown in this literature may not be available for sale and/or available in all geographies where Dow is represented. The claims made may not have been approved for use in all countries. Dow assumes no obligation or liability for the information in this document. References to Dow or the Company mean the Dow legal entity selling the products to Customer unless otherwise expressly noted. NO WARRANTIES ARE GIVEN; ALL IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED. Page 5 of 5 CYCLOTENE Advanced Electronics Resins / Growth Technologies 09/2012, Rev. 0