Abstract:
Fluid within a reflection optical switch system is purified. Gettering structures are placed within a chamber within the reflection optical switch system. The gettering structures includes heating components which when actuated attract impurities. The heating components within the gettering structures are turned on to getter out impurities from fluid within the chamber.

Description:
BACKGROUND 
     The present invention concerns fluid systems and pertains particularly to clean and test for fluid within a reflection optical switch system. 
     Optical fibers provide significantly higher data rates than electronic paths. However, effective utilization of the greater bandwidth inherent in optical signal paths requires optical cross-connect switches. 
     One type of optical cross-connect utilizes total internal reflection (TIR) switching elements. A TIR element consists of a waveguide with a switchable boundary. Light strikes the boundary at an angle. In the first state, the boundary separates two regions having substantially different indices of refraction. In this state the light is reflected off of the boundary and thus changes direction. In the second state, the two regions separated by the boundary have the same index of refraction and the light continues in a straight line through the boundary. The magnitude of the change of direction depends on the difference in the index of refraction of the two regions. To obtain a large change in direction, the region behind the boundary must be switchable between an index of refraction equal to that of the waveguide and an index of refraction that differs markedly from that of the waveguide. 
     One type of TIR element is taught in U.S. Pat. No. 5,699,462 which is hereby incorporated by reference. The TIR taught in this patent utilizes thermal activation to displace liquid from a gap at the intersection of a first optical waveguide and a second optical waveguide. In this type of TIR, a trench is cut through a waveguide. The trench is filled with an index-matching liquid. A bubble is generated at the cross-point by heating the index matching liquid with a localized heater. The bubble must be removed from the crosspoint to switch the cross-point from the reflecting to the transmitting state and thus change the direction of the output optical signal. Purity of the liquid and near absolute cleanliness within the assembled package is necessary for optimal performance and longevity of the TIR elements. 
     SUMMARY OF THE INVENTION 
     In accordance with the preferred embodiment, fluid within a reflection optical switch system is purified. Gettering structures are placed within a chamber within the reflection optical switch system. The gettering structures include heating components which when actuated attract impurities. The heating components within the gettering structures are turned on to getter out impurities from the fluid within the chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified illustration of an optical switch system in accordance with a preferred embodiment of the present invention. 
         FIG. 2  shows sample heating structures used to heat and purify liquid within the optical switch system shown in  FIG. 1  in accordance with a preferred embodiment of the present invention. 
         FIG. 3  shows coupon structures of various sizes used to test the purity of liquid within the optical switch system shown in  FIG. 1  in accordance with a preferred embodiment of the present invention. 
         FIG. 4  shows biasing structures used to purify liquid within the optical switch system shown in  FIG. 1  in accordance with a preferred embodiment of the present invention. 
         FIG. 5  shows the positioning of heating structures placed around filaments and used to purify liquid within the optical switch system shown in  FIG. 1  in accordance with a preferred embodiment of the present invention. 
         FIG. 6  shows the positioning of heating structures placed around filaments and used to purify liquid within the optical switch system shown in  FIG. 1  in accordance with another preferred embodiment of the present invention. 
         FIG. 7  show pillars of silicon suspending resistors within a filament in accordance with another preferred embodiment of the present invention. 
         FIG. 8  and  FIG. 9  show a bridge structure suspended over a filament hole in accordance with another preferred embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is a simplified cross section of an optical switch system, not to scale. On package  16  is connected a silicon wafer  17 . For example package  16  is composed of molybdenum, silicon or some other material. A cap  20  a waveguide  23  and a cladding layer  24  are attached to package  16  via solder areas  18 . Cap  20  is composed of, for example, oxide or quartz. Trenches  22  are representative of one or thousands of trenches used for optical switching. The trenches penetrate through cladding layer  24  through waveguide area  23  and into cap  20 . 
     A reservoir  12  stores liquid used for optical switching. Fluid is transferred through a conduit  19  to a chamber  11 . The fluid enters chamber  11  through filaments  21  in silicon wafer  17 . There may be hundreds or thousands of filaments placed as needed throughout silicon wafer  17 . 
     Fluid in the form of vapor and liquid is transported, with the use of heat, between reservoir  12 , chamber  11  and trenches  22  used for optical switching. Arrows  13 , arrows  14  and arrows  15  represent the application and removal of heat at various locations to facilitate transport of fluid in the system. 
     Heat is added to reservoir  12  so that vapor will be transported from reservoir  12  through conduit  19  to chamber  11 . After the vapor enters chamber  11  through the filaments, the vapor begins to condense. Various structures within chamber  11  are used to achieve gettering of impurities in the system. 
       FIG. 2  shows sample heating structures used to heat and thus getter impurities. Structure  31  and structure  35  are essentially long resistors that function as heaters. Structure  31  is a frame composed of resistive material  34  placed between an electrode  32  and an electrode  33 . For example, resistive material  34  is composed of aluminum (Al), tantalum aluminum (TaAl), platinum (Pt), tungsten (W) or molybdenum (Mo) or other materials. Likewise, structure  35  is a resistive element composed of, for example, doped single crystal silicon material  38  placed between an electrode  36  and an electrode  37 . 
     Structures such as structure  31  and structure  35  can be placed, for example, below or otherwise close to solder areas  18 . Structures such as structure  31  and structure  35  are used to warm liquid within chamber  11  and to burn out the liquid and contaminants. Structures such as structure  31  and structure  35  can also be used to assist in the solder process when forming solder areas  18 . 
       FIG. 3  shows coupon structures of various sizes used to test the purity of liquid within the optical switch system shown in  FIG. 1 . Shown in  FIG. 3  is a coupon structure  42 , a coupon structure  43  and a coupon structure  44 . Coupon structures  42  through  44  are representative of thousands of coupon structures of different sizes, different coating materials and different surface roughness, etc. used within chamber  11  (shown in  FIG. 1 ). Example materials out which the coupon structures are composed include Pt, Chrome, Ti, Ta, W, Si or gold (Au). The materials are placed over resistors which, when actuated, heat the coupon structures and cause targeted impurities to adhere to the surface. Strategic selection of material, size, placement and activation of coupon structures allows detection, determination of concentration levels and other analysis of contaminants present within chamber  11 . 
     In  FIG. 3 , coupon structures  42  through  44  are shown connected serially with increasing or decreasing sizes. Alternatively, for example, coupon structures can be connected in parallel or in some combination of serial and parallel with increasing, decreasing or otherwise mixed sizes for the coupon structures. 
     For example, coupon structures are placed on the surface of silicon wafer  17  shown in  FIG. 1 . Oxide  20  is formed so as to be transparent and allow optical access to the coupon structures for Raman analysis. If destructive analysis is used, the coupon structures are designed with sufficient area to allow for spectroscopy techniques such as Time of Flight Secondary Ion mass spectrometry (TOF-SIMS), X-ray Photoelectron Spectroscopy (XPS) analysis or Rutherford Back Scattering (RBS) analysis. 
       FIG. 4  shows structures designed to be turned on periodically to monitor change in impurity levels during operation of the optical switch system shown in  FIG. 1 . Shown in  FIG. 4  are a conductor  50  and a conductor  54  in parallel. Conductor  50  consists of conductive material  53  between an electrode  51  and an electrode  52 . Conductive material  53  is formed of, for example, Mo, W, or Ta. These materials have high melting points and a relatively long life for electrical and oxidation stresses. Conductor  54  consists of conductive material  56  between an electrode  55  and an electrode  57 . Conductive material  56  is formed of, for example, Mo, W, or Ta, rhenium (Re), rhodium (Rh), iridium (Ir), Pt and other alloys thereof. A gap  58  between conductor  50  and conductor  54  can vary, for example from 2 to 50 micrometers. For example, when activated, voltage across conductor  50  and conductor  54  can be stepped up in ultra high precision voltage increments noting fAmp and pVolt conductivity changes. The resulting current drawn can be measured by rheotstats, bridge networks or an inline current limiting resistor. Each of these field effect devices can be coated with different dielectrics to prevent hards, shorts and to aid in creating enhanced chemical and surface physics reactions. Examples of these coatings include carbon, Teos, Si3N4, SiC, SiO2, Al2O3, pyrolyne, polyimides, Teflon, SrTaO3. 
     Also shown in  FIG. 4  are a conductor  60  and a conductor  64  in parallel. Conductor  60  consists of conductive material  62 , an electrode  61  and an electrode  63 . Conductive material  63  is formed of, for example, Mo, W, or Ta, Re, Rh, Ir, Pt and other alloys thereof. Conductor  64  consists of conductive material  66 , an electrode  65  and an electrode  67 . Conductive material  66  is formed of, for example, Mo, W, or Ta, Re, Rh, Ir, Pt and other alloys thereof. A gap  68  between conductor  60  and conductor  64  can vary, for example from 2 to 50 micrometers. For example, when activated, voltage across conductor  60  and conductor  64  can be stepped up in ultra high precision voltage increments noting fAmp and pVolt conductivity changes. 
       FIG. 5  shows the positioning of heating structures placed around the filaments represented in  FIG. 1  by dashes  21 . As shown in  FIG. 5 , a filament hole  71 , a filament hole  72  and a filament hole  73  are surrounded by a heating element  74 , a heating element  75 , a heating element  76  and a heating element  77 . Filament holes  71  through  73  and heating elements  74  through  77  are merely representative, because, as noted above, there may be hundreds or thousands of filaments positioned as needed throughout silicon wafer  17 . 
     Heating element  74  consists of resistive material  79  placed over and between electrodes  78 . Heating element  75  consists of resistive material  80  placed over and between electrodes  81 . Heating element  76  consists of resistive material  83  placed over and between electrodes  82 . Heating element  77  consists of resistive material  85  placed over and between electrodes  84 . For example, resistive materials  79 ,  81 ,  83  and  85  include a layer of Platinum (Pt) placed over a layer of titanium (Ti). Alternatively, resistive materials  79 ,  81 ,  83  and  85  include a layer of (Platinum) placed between two layers of titanium (Ti). Ti/Pt coated resistors are designed to getter hydrocarbons. Ti/Pt/Ti coated resistors are designed to getter oxygen and water vapor. Straight or optional resistor shapes can be used instead of the bow tie shapes. While shown with an octagon shape, filament holes  71  through  73  can be different shapes. 
       FIG. 6  shows an alternative embodiment of heating structures surrounding a filament hole. A filament hole  91  is surrounded by a heating element  92  and a heating element  93 . For example, heating element  92  consists of resistive material composed of a layer of Pt placed over a layer of Ti. For example, heating element  93  consists of resistive material composed of a layer of Pt placed between two layers of Ti. Ti/Pt resistors are designed to getter hydrocarbons. Ti/Pt/Ti covered resistors are designed to getter oxygen and water vapor. 
       FIG. 7  illustrates suspended pillars of silicon suspending resistors within filaments, such as filaments  21  shown in  FIG. 1 . Looking down through a filament hole  121  are seen a silicon pillar  122 , a silicon pillar  123  and a silicon pillar  124 . Each of silicon pillars  122  through  124  is used to suspend a resistor within the filament hole  121 . For example, each of silicon pillars  122  through  124  is covered with a layer of Pt placed over a layer of Ti or is covered with a layer of Pt placed between two layers of Ti. Ti/Pt resistors are designed to getter hydrocarbons. Ti/Pt/Ti covered resistors are designed to getter oxygen and water vapor. 
       FIG. 8  shows a bridge  222  suspended over a filament hole  221 . For example, bridge  222  is composed of silicon covered with a layer of Pt placed over a layer of Ti or covered with a layer of Pt placed between two layers of Ti. Ti/Pt resistors are designed to getter hydrocarbons. Ti/Pt/Ti covered resistors are designed to getter oxygen and water vapor. Bridge  222  is placed on an electrode  223  and an electrode  224  on the surface of a substrate. 
       FIG. 8  also shows a bridge  227  suspended over a filament hole  226 . For example, bridge  226  is composed of silicon covered with a layer of Pt placed over a layer of Ti or covered with a layer of Pt placed between two layers of Ti. Ti/Pt resistors are designed to getter hydrocarbons. Ti/Pt/Ti covered resistors are designed to getter oxygen and water vapor. Bridge  227  is placed on an electrode  228  and an electrode  228  on the surface of a substrate. 
     Bridge  222  and bridge  227  are illustrative of bridges that may be placed through chamber  11  (shown in  FIG. 1 ). The bridges can be placed over filament holes and also at locations where there are not filament holes. 
       FIG. 9  is a side view of bridge  222 . For example, bridge  222  is placed on a silicon substrate  17  through which filament hole  221  has been formed. 
     For example, the various structures described above are used for gettering and testing as follows. When transporting vapor into chamber  11  shown in  FIG. 1 , maximum temperature is maintained within the chamber and available heating and gettering structures such as structure  31  and structure  35  shown in  FIG. 2  are turned on. Also turned on are heaters around filament holes such as heating elements  74  through  77  shown in  FIG. 5  and/or heating elements  92  and  93  shown in  FIG. 6 . 
     Once liquid condenses within chamber  11 , testing structures such as coupon structures  42  through  43  are turned on and deposits monitored. This is done, for example, until no further deposits are being made or oxide growth occurs at rates outside of the formulated and preferred levels. For example, Raman analysis is used to optically evaluate test structures placed, for example on silicon wafer  17  (shown in  FIG. 1 ) by optically accessing the testing structures through the package to determine the contamination level and composition. Destructive analysis such as XPS, TOF-SIMS and RBS analysis can also be used. 
     Once initial cleaning of the device has been performed and initial testing has been passed, test structures such as those formed by conductors  50  and  54 , and conductors  60  and  64  can be used for periodic monitoring. For example, periodic monitoring is performed to detect any change over time in the impurity level of fluid in chamber  11 . If, during the performance of periodic monitoring, deposits are detected, bubbles form at too low of voltage, or bubbles persist after voltage is removed, the initial cleaning and testing can be performed again. 
     The foregoing discussion discloses and describes merely exemplary methods and embodiments of the present invention. As will be understood by those familiar with the art, the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the disclosure of the present invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.