CLEANROOM WIPER AND METHOD FOR MAKING SAME

Abstract

A pre-saturated wiper for use in a cleanroom environment, or other similarly controlled environment, that includes a woven fabric comprised of two separate and distinct microfiber materials which incorporates a unique weave pattern with sealed edges that is saturated with only Ultrapure water (UPW).

Claims

1. A cleanroom wiper comprising a woven fabric having a first microfiber material comprising a nylon/polyester conjugate woven with a second separate and distinct microfiber material comprising a polyester wherein the woven fabric is pre-saturated with only ultrapure water which immediately and evenly wets into the wiper.

2. The cleanroom wiper of claim 1 wherein the woven fabric comprises sealed edges.

3. The cleanroom wiper of claim 1 wherein the first and second microfiber materials are woven using a repeating pattern having six warp threads and eighteen weft threads.

4. The cleanroom wiper of claim 1 wherein the wiper has an absorptive capacity of greater than 300 mL/m.sup.2 and an absorptive rate of less than 0.6 seconds.

5. The cleanroom wiper of claim 1 wherein the first microfiber material comprising a nylon/polyester conjugate comprises 25-30% nylon and 70-75% polyester.

6. The cleanroom wiper of claim 5 wherein the woven fabric comprises sealed edges.

7. The cleanroom wiper of claim 5 wherein the first and second microfiber materials are woven using a repeating pattern having six warp threads and eighteen weft threads.

8. The cleanroom wiper of claim 5 wherein the wiper has an absorptive capacity of greater than 300 mL/m.sup.2 and an absorptive rate of less than 0.6 seconds.

9. A method for making a pre-saturated cleanroom wiper saturated with only ultra pure water comprising the steps of: weaving a first microfiber material comprising a nylon/polyester conjugate with a second separate and distinct microfiber material comprising a polyester to create a woven fabric; processing the woven fabric with high temperature, high pressure, and at least one surfactant; cleaning the woven fabric with aseptic ultra pure water; drying the woven fabric; cutting the woven fabric and sealing the edges of the woven fabric to create individual wipers; and packaging and pre-saturating the wipers with only ultra pure water.

10. The method of claim 9 wherein the step of weaving comprises weaving the first and second microfiber materials using a repeating pattern having six warp threads and eighteen weft threads.

11. The method of claim 9 wherein the step of cleaning the woven fabric comprises washing the woven fabric with a detergent followed by repeated rinsing of the woven fabric with aseptic pure water.

12. The method of claim 9 wherein the step of cutting and sealing the edges of the woven fabric comprises simultaneous cutting and sealing.

13. The method of claim 9 further comprising the step of sterilizing the packaged pre-saturated wipers.

14. The method of claim 9 further comprising the step of relaxing the microfibers of the woven fabric before the step of processing the woven fabric.

15. A method for making a pre-saturated cleanroom wiper saturated with only ultra pure water comprising the steps of: weaving a first microfiber material comprising a nylon/polyester conjugate comprising 25-30% nylon and 70-95% polyester and a second separate and distinct microfiber material comprising a polyester to create a woven fabric; processing the woven fabric with high temperature, high pressure, and at least one surfactant; cleaning the woven fabric with aseptic ultra pure water; drying the woven fabric; cutting the woven fabric and sealing the edges of the woven fabric to create individual wipers; and packaging and pre-saturating the wipers with only ultra pure water.

16. The method of claim 15 wherein the step of weaving comprises weaving the first and second microfiber materials using a repeating pattern having six warp threads and eighteen weft threads.

17. The method of claim 15 wherein the step of cleaning the woven fabric comprises washing the woven fabric with a detergent followed by repeated rinsing of the woven fabric with aseptic pure water.

18. The method of claim 15 wherein the step of cutting and sealing the edges of the woven fabric comprises simultaneous cutting and sealing.

19. The method of claim 15 further comprising the step of sterilizing the packaged pre-saturated wipers.

20. The method of claim 15 further comprising the step of relaxing the microfibers of the woven fabric before the step of processing the woven fabric.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a flow chart showing steps in an exemplary method for making the UPW pre-saturated cleanroom wiper of the present invention;

[0015] FIG. 2 is a photo of a first microfiber that is used to make the woven fabric that is used to make one exemplary embodiment of the wiper of the present invention;

[0016] FIG. 3 is a photo of a second microfiber that is used to make the woven fabric that is used to make the exemplary embodiment of the wiper of the present invention referred to in FIG. 2;

[0017] FIG. 4 is a photo of a modified woven fabric having fast water wet out that was made using the microfibers shown in FIGS. 2 and 3;

[0018] FIG. 5 is a drawing showing the weaving pattern that was used to make the modified woven fabric having fast water wet out shown in FIG. 4; and

[0019] FIG. 6 is a magnified drawing of relaxed fibers that make up the modified woven fabric having fast water wet out shown in FIG. 4.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0020] Currently used cleanroom wipers pre-saturated with IPA are comprised of polyester. Polyester wipers need to fully wet a surface to be cleaned in order to get any kind of cleaning efficiency. One hundred percent polyester fabrics do not leave surfaces dry. Leaving a cleaned surface in a cleanroom wet with IPA is not a concern because all of the IPA will quickly evaporate. However, the downside to using IPA is that the IPA fumes are hazardous, flammable, and a source of pollution. In addition, 100% polyester easily sheds particles due to its lower resistance to abrasion.

[0021] Despite the issues and drawbacks associated with IPA pre-saturated polyester wipers, semiconductor fabrication plants would never consider using water with wipers because many tools in the semiconductor manufacturing process must operate at 104 to 107 atmospheres and leaving water in the tool will extend pump down times by three to five times or by many hours. Plants will not allow these pump down times because the tools are valued at over $10,000 dollars/hr. However, if a wiper for use with water could be manufactured such that it would function like a wiper used with IPA, i.e. function so that it cleans but does not leave a cleaned surface wet, then semiconductor fabrication plants may readily elect to use them since they do not possess the safety and health risks associated with IPA.

[0022] The present invention is directed to just such a wiper. The present invention includes a pre-saturated wiper that is saturated exclusively with Ultrapure water (UPW) and that is constructed in such a way that the UPW immediately and evenly wets into the wiper and is capable of cleaning critical surfaces without leaving water on the critical surface. The present invention also includes a method for making the UPW pre-saturated wiper of the present invention.

[0023] FIG. 1 is a flow chart showing steps in an exemplary method 10 for making the UPW pre-saturated cleanroom wiper of the present invention. First, in step 12, fibers are selected for creating a woven fabric that will be used to make the wipers. The fibers include a first microfiber that is a nylon/polyester conjugate and a second fiber that is a polyester. A photo of a first microfiber that can be used to make the woven fabric that is used to make one exemplary embodiment of the wiper of the present invention is shown in FIG. 2. The first microfiber material is soft, shiny, and very bulky. It also provides for excellent moisture penetration and air ventilation. The nylon/polyester conjugate may be made of 25-30% nylon and 70-75% polyester. In one particular exemplary embodiment, the nylon/polyester conjugate may comprise 72% polyester and 28% nylon. A photo of a second microfiber that can be used to make the woven fabric that is used to make the exemplary embodiment of the wiper of the present invention is shown in FIG. 3. The second microfiber material is soft, high density, waterproof, permeable to moisture, and has a high tensile strength.

[0024] In step 14, the first and second microfibers are woven using a specific weaving pattern like that shown in FIG. 5 which assists in enabling the woven fabric to be Fast Water Wet Out, meaning that water can immediately and evenly wet into the woven fabric. The weaving pattern shown in FIG. 5 is one repeating unit that includes 6 warp threads and 18 weft threads. Each box shows the interlocking point of the weave. “X” means the warp yarn/microfiber is above the weft yarn/microfiber on this interlocking point. The first microfiber material described above is used as the weft thread and the second microfiber material described above is used as the warp thread. The first and second microfibers are woven to create a roll of woven fabric that is used to make the wipers. In one exemplary method, the rolls of woven fabric may comprise 61-inch-wide rolls of woven fabric.

[0025] The woven fabric is processed in step 16 with high temperature and high pressure and one or more agents such as a surfactant that lowers the interfacial tension between UPW and the woven fabric thereby acting as a wetting agent. This processing further assists in enabling the woven fabric to be Fast Water Wet Out. After processing, a special arrangement on the loom used to weave the microfibers into the woven fabric is used to relax the woven fibers as shown in FIG. 6. A resulting starfish type cross section of the Fast Water Wet Out processed woven fabric is shown in FIG. 4.

[0026] In step 18, the processed roll of woven fabric is then clean processed with aseptic ultra pure water. More specifically, the roll of processed woven fabric is washed with detergent for 10 minutes and then rinsed for 36 minutes by performing nine rinses for 4 minutes each. Water is extracted from the roll by spinning it for 5 minutes at 300 rpm and then for 5 minutes at 600 rpm. The roll is then dried in the dryer at 85 degrees Celsius for 2 hours.

[0027] Wipers are then formed from the roll of processed woven fabric in step 20. The roll of processed woven fabric is further processed into thinner rolls of fabric and finally to sheets. Smaller rolls and sheets of processed woven fabric are simultaneously cut and sealed with an ultrasonic tool that has a PVD coating on top of the stainless steel to minimize metal contamination transferring to the wiper from the tooling. The fabric is cut and sealed along the length to form sealed edges and then it is processed on another machine to be cut and sealed across the web to create an individual wiper.

[0028] In step 22, the individual sealed edge wipers are packaged and pre-saturated with UPW. The wipers are flat stacked on top of each other with 10 or 20 wipers per package. Rolling, ironing, and cutting of the roll of processed woven fabric to form wipers is done in a clean room. Packing and pre-saturation of the wipers is also done in a clean room. The packaged pre-saturated wipers are then sterilized using gamma radiation in step 24. Gamma irradiation is a standard sterilization procedure in which gamma irradiators are powered by Cobalt-60 to effectively kill microorganisms throughout the product and its packaging with very little temperature effect and no residues. Finally, lots of packaged, sterilized products are tested in step 26 to certify cleanliness.

[0029] The UPW pre-saturated cleanroom wipers of the present invention work like IPA pre-saturated cleanroom wipers without the safety, environmental, and health issues that are associated with IPA. The UPW pre-saturated cleanroom wipers are clean, smooth and capable of effective cleaning without leaving water behind on the cleaned surface. The woven fabric that comprises the pre-saturated wipers is designed so that the cleaning surface dries very quickly, as it does with IPA pre-saturated wipers.

[0030] Process benefits from using the UPW pre-saturated cleanroom wipers of the present invention include, but are not limited to, 1) protecting VOC sensitive fab modules such as lithography, metrology, and CVD from solvent fumes, 2) reducing the risk of fiber and particle excursions associated with fab wipers, 3) improved contamination pickup leading to faster preventative maintenance and improved equipment uptime, 4) even, consistent wetting of wipers which enables excellent first pass cleaning results and reduced cleaning time, and 5) a wiper optimized for use in the most advanced wafer fabs. In addition, using the UPW pre-saturated cleanroom wipers of the present invention enables reduced cost of ownership by reducing wiper usage resulting in a reduction of waste removal cost, greatly reducing VOC process exposure and fugitive emissions costs by eliminating IPA wipes, reducing the cost of Test Wafers by improving 1.sup.st Pass quality, reducing costs associated with tool downtime by improving particle control, and reducing mean time to clean.

[0031] Environmental health and safety benefits experienced with the use of the UPW pre-saturated cleanroom wipers of the present invention include, but are not limited to, 1) eliminating fire risk during cleanroom wipe downs by reducing flammable chemical storage and solvent squirt bottles, 2) eliminating fugitive VOC emissions and air permit implications associated with solvent wiping, and 3) eliminating personnel exposure to isopropyl alcohol during cleanroom wipe downs.

[0032] Initial evaluations of performance and contamination characteristics of the UPW pre-saturated cleanroom wipers of the present invention show improvements over existing IPA pre-saturated wipers. Some initial data showing these characteristics for the UPW pre-saturated cleanroom wipers of the present invention are set forth in Table 1 below. The data in Table 1 represents typical analyses of the wipers after seven days of saturation (in dry state). The unit of measurement refers to the standard unit used in standard test method IEST-RP-CC004.3.

TABLE-US-00001 TABLE 1 Property Typical Value Performance Characteristics Basis Weight 160 g/m.sup.2 Absorbency Sorptive Capacity 330 mL/m.sup.2 Sorptive Rate 0.5 seconds Contamination Characteristics LPC ≥ 0.5 um 700 particles/cm.sup.2 Fiber ≥ 100 um 250 fibers/m.sup.2 Non-Volatile Residue IPA extractant 0.15 g/m.sup.2 DI Water extractant 0.05 g/m.sup.2 Ions Chloride 0.10 ppm Sodium 0.20 ppm Potassium 0.20 ppm Organic with FTIR Silicone Not detected Amide Not detected DOP Not detected VOC 0 ppb

[0033] The drawings and description of exemplary embodiments of the invention herein shows various exemplary embodiments of the invention. These exemplary embodiments and modes are described in sufficient detail to enable those skilled in the art to practice the invention and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the following disclosure is intended to teach both the implementation of the exemplary embodiments and modes and any equivalent modes or embodiments that are known or obvious to those reasonably skilled in the art. Additionally, all included examples are non-limiting illustrations of the exemplary embodiments and modes, which similarly avail themselves to any equivalent modes or embodiments that are known or obvious to those reasonably skilled in the art.

[0034] Other combinations and/or modifications of structures, arrangements, applications, proportions, elements, materials, or components used in the practice of the instant invention, in addition to those not specifically recited, can be varied or otherwise particularly adapted to specific environments, manufacturing specifications, design parameters, or other operating requirements without departing from the scope of the instant invention and are intended to be included in this disclosure.

[0035] Unless specifically noted, it is the Applicant's intent that the words and phrases in the specification and the claims be given the commonly accepted generic meaning or an ordinary and accustomed meaning used by those of ordinary skill in the applicable arts. In the instance where these meanings differ, the words and phrases in the specification and the claims should be given the broadest possible, generic meaning. If any other special meaning is intended for any word or phrase, the specification will clearly state and define the special meaning.