Clean and test for fluid within a reflection optical switch system

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.

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.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1is a simplified cross section of an optical switch system, not to scale. On package16is connected a silicon wafer17. For example package16is composed of molybdenum, silicon or some other material. A cap20a waveguide23and a cladding layer24are attached to package16via solder areas18. Cap20is composed of, for example, oxide or quartz. Trenches22are representative of one or thousands of trenches used for optical switching. The trenches penetrate through cladding layer24through waveguide area23and into cap20.

A reservoir12stores liquid used for optical switching. Fluid is transferred through a conduit19to a chamber11. The fluid enters chamber11through filaments21in silicon wafer17. There may be hundreds or thousands of filaments placed as needed throughout silicon wafer17.

Fluid in the form of vapor and liquid is transported, with the use of heat, between reservoir12, chamber11and trenches22used for optical switching. Arrows13, arrows14and arrows15represent the application and removal of heat at various locations to facilitate transport of fluid in the system.

Heat is added to reservoir12so that vapor will be transported from reservoir12through conduit19to chamber11. After the vapor enters chamber11through the filaments, the vapor begins to condense. Various structures within chamber11are used to achieve gettering of impurities in the system.

FIG. 2shows sample heating structures used to heat and thus getter impurities. Structure31and structure35are essentially long resistors that function as heaters. Structure31is a frame composed of resistive material34placed between an electrode32and an electrode33. For example, resistive material34is composed of aluminum (Al), tantalum aluminum (TaAl), platinum (Pt), tungsten (W) or molybdenum (Mo) or other materials. Likewise, structure35is a resistive element composed of, for example, doped single crystal silicon material38placed between an electrode36and an electrode37.

Structures such as structure31and structure35can be placed, for example, below or otherwise close to solder areas18. Structures such as structure31and structure35are used to warm liquid within chamber11and to burn out the liquid and contaminants. Structures such as structure31and structure35can also be used to assist in the solder process when forming solder areas18.

FIG. 3shows coupon structures of various sizes used to test the purity of liquid within the optical switch system shown inFIG. 1. Shown inFIG. 3is a coupon structure42, a coupon structure43and a coupon structure44. Coupon structures42through44are representative of thousands of coupon structures of different sizes, different coating materials and different surface roughness, etc. used within chamber11(shown inFIG. 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 chamber11.

InFIG. 3, coupon structures42through44are 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 wafer17shown inFIG. 1. Oxide20is 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. 4shows structures designed to be turned on periodically to monitor change in impurity levels during operation of the optical switch system shown inFIG. 1. Shown inFIG. 4are a conductor50and a conductor54in parallel. Conductor50consists of conductive material53between an electrode51and an electrode52. Conductive material53is formed of, for example, Mo, W, or Ta. These materials have high melting points and a relatively long life for electrical and oxidation stresses. Conductor54consists of conductive material56between an electrode55and an electrode57. Conductive material56is formed of, for example, Mo, W, or Ta, rhenium (Re), rhodium (Rh), iridium (Ir), Pt and other alloys thereof. A gap58between conductor50and conductor54can vary, for example from 2 to 50 micrometers. For example, when activated, voltage across conductor50and conductor54can 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.

FIG. 5shows the positioning of heating structures placed around the filaments represented inFIG. 1by dashes21. As shown inFIG. 5, a filament hole71, a filament hole72and a filament hole73are surrounded by a heating element74, a heating element75, a heating element76and a heating element77. Filament holes71through73and heating elements74through77are merely representative, because, as noted above, there may be hundreds or thousands of filaments positioned as needed throughout silicon wafer17.

Heating element74consists of resistive material79placed over and between electrodes78. Heating element75consists of resistive material80placed over and between electrodes81. Heating element76consists of resistive material83placed over and between electrodes82. Heating element77consists of resistive material85placed over and between electrodes84. For example, resistive materials79,81,83and85include a layer of Platinum (Pt) placed over a layer of titanium (Ti). Alternatively, resistive materials79,81,83and85include 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 holes71through73can be different shapes.

FIG. 6shows an alternative embodiment of heating structures surrounding a filament hole. A filament hole91is surrounded by a heating element92and a heating element93. For example, heating element92consists of resistive material composed of a layer of Pt placed over a layer of Ti. For example, heating element93consists 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. 7illustrates suspended pillars of silicon suspending resistors within filaments, such as filaments21shown inFIG. 1. Looking down through a filament hole121are seen a silicon pillar122, a silicon pillar123and a silicon pillar124. Each of silicon pillars122through124is used to suspend a resistor within the filament hole121. For example, each of silicon pillars122through124is 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. 8shows a bridge222suspended over a filament hole221. For example, bridge222is 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. Bridge222is placed on an electrode223and an electrode224on the surface of a substrate.

FIG. 8also shows a bridge227suspended over a filament hole226. For example, bridge226is 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. Bridge227is placed on an electrode228and an electrode228on the surface of a substrate.

Bridge222and bridge227are illustrative of bridges that may be placed through chamber11(shown inFIG. 1). The bridges can be placed over filament holes and also at locations where there are not filament holes.

FIG. 9is a side view of bridge222. For example, bridge222is placed on a silicon substrate17through which filament hole221has been formed.

For example, the various structures described above are used for gettering and testing as follows. When transporting vapor into chamber11shown inFIG. 1, maximum temperature is maintained within the chamber and available heating and gettering structures such as structure31and structure35shown inFIG. 2are turned on. Also turned on are heaters around filament holes such as heating elements74through77shown inFIG. 5and/or heating elements92and93shown inFIG. 6.

Once liquid condenses within chamber11, testing structures such as coupon structures42through43are 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 wafer17(shown inFIG. 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 conductors50and54, and conductors60and64can be used for periodic monitoring. For example, periodic monitoring is performed to detect any change over time in the impurity level of fluid in chamber11. 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.