WO2002044763A2

WO2002044763A2 - Formation of a smooth surface on an optical component

Info

Publication number: WO2002044763A2
Application number: PCT/US2001/030565
Authority: WO
Inventors: Chi Wu; Xiaoming Yin; James R. Velebir Jr.
Original assignee: Lightcross, Inc.
Priority date: 2000-11-28
Filing date: 2001-09-27
Publication date: 2002-06-06
Also published as: AU2001296420A1; WO2002044763A3

Abstract

A method for smoothing one or more surfaces on an optical component is disclosed. The method includes obtaining an optical component having one or more surfaces and performing a smoothing etch so as to smooth the one or more surfaces.

Description

FORMATION OF A SMOOTH SURFACE ON AN OPTICAL COMPONENT

RELATED APPLICATIONS This application is a continuation-in-part of U.S. Patent Application serial number 09/724,177; entitled "Formation of a Smooth Surface on an Optical Component"; filed on November 28, 2000 and incorporated herein in its entirety and of U.S. Patent Application serial number 09/896,127; entitled "Optical Component"; filed on June 29, 2001 and incorporated herein in its entirety.

BACKGROUND

1. Field of the Invention

The invention relates to one or more optical networking components. In particular, the invention relates to methods of smoothing one or more surfaces on optical networking components.

2. Background of the Invention

A variety of the components used in optical networking include one or more surfaces that reflect or transmit light. The smoothness of these surfaces can affect the performance of the optical component and/or the optical network. For instance, many optical components include a facet through which light signals enter or exit the optical component. The amount of reflection and scattering that occurs at the facet increases as the roughness of the facet increases. As a result, increasing the roughness of the surface increases the amount of optical loss associated with the optical component.

For the above reasons, there is a need for a method of smoothing surfaces on optical components.

SUMMARY OF THE INVENTION

The invention relates to a method for smoothing one or more surfaces on an optical component. The method includes obtaining an optical component having one or more surfaces and performing a smoothing etch so as to smooth the one or more surfaces.

The one or more surfaces can be the surfaces of a light transmitting medium configured to carry light signals. The one or more surfaces can be surfaces through which the light signals are transmitted or surfaces at which light signals are reflected.

In one embodiment of the method, the one or more surfaces have a roughness of greater than 220 nm and performing the smoothing etch provides the one or more surfaces with a smoothness less than 220 nm, 100 nm, 50 nm, 20 nm or 8 nm.

One embodiment of the smoothing etch includes applying an etchant and a passivant to the component. A suitable etchant is HCL and a suitable passivant is H₂. In some instances, the etchant and the passivant are applied in an isotropic dry etch such as a gas phase etch or a plasma etch. Another embodiment of the smoothing etch includes applying a first medium to the one or more surfaces of the optical component so as to convert a material that defines the one or more surfaces of the optical component to a second material. The method also includes applying a second medium to the one or more surfaces of the optical component so as to remove at least a portion of the second material from the one or more surfaces of the optical component.

Yet another embodiment of the smoothing etch includes obtaining an optical component having a material defining one or more surfaces. The method also includes applying an oxidant to the one or more surfaces such that an oxide of the material is formed on the one or more surfaces. In some instances, the oxide is isotropically formed on the one or more surfaces. The method further includes applying an oxide remover to the one or more surfaces so as to remove the oxide from the one or more surfaces.

The oxidant and the oxide remover can be included in a solvent liquid. The solvent can include acetic acid. The solvent can exclude water. In some instances the oxidant includes HN0₃ and the oxide remover includes HF. The molar ratio of oxidant to oxide remover can fall within a range of 1 : 1 to 1 : 20 or 1:4 to 1:8. Some embodiments of the above methods include performing one or more foreign substance removal operations before performing the smoothing etch. The one or more foreign substance removal operations are configured to remove foreign substances from the one or more surfaces to be smoothed by the smoothing etch. Examples of foreign substance removal operations include an oxygen plasma clean, a polymer residue clean and silica removal.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 A illustrates a portion of a component having a plurality of light signal reflecting surfaces and a light signal transmission surface.

Figure IB illustrates a portion of a component having a light signal reflecting surface positioned at the intersection of two waveguides.

Figure 2A through Figure 2D illustrate a method of forming an optical component having a surface to be smoothed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention relates to a method of smoothing one or more surfaces on an optical component. The method includes obtaining an optical component having one or more surfaces that have an undesirable level of roughness. The surfaces can be surfaces where light signals are reflected and/or surfaces where light signals are transmitted. The method also includes performing a smoothing etch so as to smooth the one or more surfaces. In some instances, the component is cleaned before the smoothing etch is performed.

A suitable smoothing etch includes applying a first medium and a second medium to the one or more surfaces. The first medium is selected to convert the material that defines the one or more surfaces to a second material. For instance, the first medium can be an oxidant selected to convert the material that defines the one or more surfaces to an oxide of the material that defines the one or more surfaces. In some instances, the first medium isotropically converts the material. The second medium is selected to remove the second material from the one or more surfaces. For instance, the second medium can be selected to remove the oxide from the one or more surfaces. The roughness of the one or more surfaces results from the presence of bumps on the one or more surfaces. The first medium can be selected to convert the material at the tops of bumps to the second material faster than it converts the material in the valleys between the bumps to the second material. As a result, the second medium removes material from the tops and sides of the bumps faster than the second medium removes materials from between the bumps. Removing material from the tops of the bumps faster than from between the bumps causes the bumps to be smoothed.

The first medium and the second medium can be applied to the one or more surfaces in a wet etch. A suitable wet etch solution employs HN0₃ as the first medium and HF as the second medium. When silicon defines the one or more surfaces, this wet etch solution can be used at room temperature and pressure to provide the one or more surfaces with a roughness less than 1 nm depending on the duration, original roughness of the one or more surfaces and conditions of the smoothing etch. The ability to perform the smoothing etch at room temperature and pressure reduces the costs and complexity associated with fabrication of the optical components.

Another embodiment of the smoothing etch includes applying a passivant and an etchant to the one or more surfaces. A suitable etchant is HC1 and a suitable passivant is H₂. The passivant can react with the material that defines the surfaces to provide a substance that evaporates. Because the passivant reacts with the tops of bumps on the surface faster than the valleys between the bumps, the evaporation of the substance causes the tops of the bumps to be smoothed. As a result, the passivant enhances the action of the etchant. Further, the smoothing etch can be performed under conditions that cause the material defining the surface to reflow. The reflow further enhances the surface smoothness. When the method is performed with HC1 as the etchant and H₂ as the passivant, surfaces with a roughness less than 1 nm can be achieved depending on the duration and conditions of the smoothing etch as well as the material being etched. Figure 1 A illustrates an edge of a component 10 having a waveguide 14 ending in a light transmitting surface 12 known as a facet 16. The component 10 includes a light transmitting medium 18 positioned adjacent to a light barrier 20. The light barrier 20 is positioned adjacent to a substrate 22. The light transmitting medium 18 includes a ridge 23 extending from a side 24 of the component 10. The ridge 23 defines a portion of a light signal carrying region 26 where light signals are constrained. The light barrier 20 includes a material that causes light traveling through the light signal carrying region 26 to be reflected back into the light signal carrying region 26. Accordingly, the light barrier 20 defines another portion of the light signal carrying region 26. A profile of a light signal traveling along the light signal carrying region 26 is illustrated by the arrow labeled A.

Suitable substrates 22 include, but are not limited to, silicon. Suitable light transmitting media include, but are not limited to, silicon and polysilicon. The light barrier 20 can include a material having reflective properties such as metals. Alternatively, the light barrier 20 can have a lower index of refraction than the light transmitting medium 18. For instance, the light barrier 20 can be silica or air when the light transmitting medium 18 is silicon. The change in the index of refraction causes reflection of a portion of the light signals incident on the light barrier 20.

The component 10 includes a facet 16 through which light signals enter and/or exit the component 10. The facet 16 is often connected to an optical fiber in communication with an optical network. Light signals from the network can enter the optical component 10 through the facet 16 and/or light signals from the component 10 can exit the component 10 through the facet 16. The rougher the surface 12, the larger the amount of reflection and scattering that will occur at the facet 16. Accordingly, a rough facet 16 can be associated with increased optical loss. The ridge 23 includes a top side 28 between two lateral sides 30. The light signals are reflected off these sides 28, 30 as the light signal travels along the light signal carrying region 26. The amount of reflection and scattering that occurs as the light signal travels along the waveguide 14 increases as the roughness of these sides 28, 30 increases. Accordingly, rough sides can increase the optical losses associated with the waveguide 14.

Figure IB illustrates a portion of an optical component 10 having another embodiment of a reflecting surface 12. The reflecting surface 12 is positioned at the intersection of two waveguides 14. The surface 12 can be positioned at an angle that reflects light from one of the waveguides 14 into the other waveguide 14. For instance, the surface 12 can be positioned so as to provide total internal reflection. Total internal reflection is encouraged by increasing the angle between the intersecting waveguides 14. The surface 12 can extend through the light transmitting medium 18 to the light barrier 20. As shown in Figure 1A, the light signals travel through the light transmitting medium 18 in the ridge 23 and below the ridge 23. Accordingly, extending the surface 12 through the light transmitting medium 18 increases the percentage of the light signal that is reflected by the surface 12. As noted above, roughness increases the amount of scattering and reflection at the surface 12. Accordingly, smoothing this surface 12 can increase the performance of the component 10.

The components 10 and waveguides 14 illustrated in Figure 1 A and Figure IB are only an example of the types and forms of components 10 that can be employed in conjunction with the present invention. For instance, U.S. Patent Application serial number 09/686733; entitled "Waveguide Having a Light Drain"; filed on October 10, 2000 and U.S. Patent Application serial number 09/724175; entitled "A Compact Integrated Optics Based Arrayed Waveguide Demultiplexer"; filed November 28, 2000 teach a variety of different component 10 constructions and are each incorporated herein in their entirety.

Figures 2A through Figure 2D illustrate one method that can be used to form optical components 10 illustrated in Figure 1A and/or Figure IB. Figure 2 A illustrates an example of a silicon on insulator wafer 32. The silicon on insulator wafer 32 includes a first silicon layer 34, a silica layer 36 and a second silicon layer 38. A mask 40 is formed over the regions of the second silicon layer 38 where the ridges 22 are to be formed as shown in Figure 2B. A surface formation etch is performed so as to etch the exposed regions of the second silicon layer 38. The surface formation etch results in formation of the lateral sides 30 of the ridge 23 as shown in Figure 2C. Accordingly, the surface formation etch is performed until the lateral sides 30 the ridge 23 have the desired height as shown in Figure 2C. The ridge 23 typically extends about 1-9 μm above the side 24 of the component 10. In the case of constant lx mask printing, the sides of the mask 40 are typically formed, with about 50- 100 nm of roughness due to the limitation of mask 40 formation technologies. This roughness of the mask 40 results in a roughness of about 50-100 nm extending along the length of the ridge 23. The smoothness moving along a line extending vertically along the height of the ridge 23 results from the choice of surface formation etch used to form the ridge 23. Because the roughness along the length of the ridge 23 is caused by a different mechanism than the roughness along the height of the ridge 23, a different level of roughness can occur in different directions. A smoothing etch according to the present invention can provide smoothing in each of these directions.

After formation of a ridge 23 having the desired height, the mask 40 is removed to provide the component 10 illustrated in Figure 2D.

Reflecting surfaces 12 such as the reflecting surface 12 illustrated in Figure IB can be formed by employing various combinations of masking 40 and surface formation etches. An example of a method for forming the reflecting surface is taught in U.S. Patent application number 09/723757, filed on November 28, 2000; entitled "Formation of a Reflecting Surface on an Optical Component" and incorporated herein in its entirety.

Facets 16 can be formed on the optical component using a surface formation etch. For instance, U.S. Patent application number 09/690959, filed on October 16, 2000 and entitled "Formation of a Smooth Vertical Surface on a Optical Component" teaches employing a surface formation etch to form a facet 16. Facets 16 positioned at the edge of the component 10 can be formed by mechanical methods such as milling or laser cutting. Further, the facets 16 are often polished so as to have a roughness greater than 100 nm. Polishing techniques are difficult to apply to surfaces 12 that are not positioned at an edge of a component 10. Accordingly, polishing techniques are difficult to apply to the top and/or lateral sides 30 of the ridge 23 and are largely limited to polishing of facets 16 at the edge of the component 10. The surface formation etch is often performed with the Bosch process where application of an etch is alternated with application of a passivant. The Bosch process typically provides a surface 12 with a roughness of greater than 220 nm. In some instances, the Bosch process provides a roughness of greater than 270 nm. In other instances, the Bosch process provides a roughness of greater than 330 nm. U.S. Patent application number 09/690959, filed on October 16, 2000 and entitled "Formation of a Smooth Vertical Surface on a Optical Component" teaches a method of forming a surface 12 having a roughness greater than 20 nm and is incorporated herein in its entirety. Another suitable surface formation etch is taught in U.S. Patent application number 09/690959, filed on April 27, 2001, entitled "Formation of an Optical Component having Smooth Sidewalls" and incorporated herein in its entirety. Accordingly, surface formation etches can be performed so as to achieve surfaces 12 having a roughness greater than 20 nm, 50 nm, 100 nm, 150 nm, 170 nm, 190 nm, 220 nm, 270 nm or 330 nm.

The present method can be employed to smooth reflecting and/or transmitting surfaces 12. The method includes obtaining an optical component 10 having one or more surfaces 12 to be smoothed. Obtaining the component 10 can include fabricating the component 10 or receiving the component 10 from a supplier. The method also includes performing a smoothing etch so as to reduce the roughness of one or more surfaces 12 on the component 10. The smoothing etch can be a wet etch or a dry etch such as a gas phase etch or a plasma etch. After the smoothing etch, the component 10 can be cleaned with deionized water. A suitable smoothing etch includes applying a first medium and a second medium to the one or more surfaces 12. The first medium can be selected to convert the material that defines the one or more surfaces 12 to a second material. As shown above, the light transmitting medium 18 can be the material that defines the one or more surfaces 12. Conversion of the material to the second material can include changing the material, injecting a substance into the material and/or changing the structure of the material. An example of changing the structure of the material includes changing a crystalline structure of the material into another material. The second medium is selected to remove the second material from the one or more surfaces 12.

A suitable first medium can be an oxidant selected to convert the material that defines the one or more surfaces 12 to an oxide of the material that defines the one or more surfaces 12. In some instances, the first medium is selected to isotroptically convert the material that defines the one or more surfaces 12 to an oxide of the material that defines the one or more surfaces 12. Suitable first media include, but are not limited to, HN0₃, H₂0₂, and HF. The oxide of the material that defines the one or more surfaces 12 serves as the second material. A suitable second medium can be selected to remove the oxide from the one or more surfaces 12. Suitable oxide removers include, but are not limited to, HF and BOE (buffered oxide etch, HF with ammonium fluoride NH4F 1 :6 or 1 : 10 standard pre- mix solution). The smoothing etch can be a wet etch employing a solution that contains the first medium and the second medium. When the first medium is an oxidant such as HN0₃ and the second medium is an oxide remover such as HF, suitable molar ratios for the oxide remover to the oxidant include, but are not limited to, a range from 1 :4 to 1 :20, a range from 1 :2 to 1 : 10, a range from 1 :4 to 1 :8 and a range from 1 :5 to 1 :7. Increasing the amount of oxidant increases the etch rate. Suitable solvents or buffering agents include, but are not limited to, acetic acid (CH3COOH), and H₂O. The presence of water in the solution can reduce the oxidation power of the oxidant. Accordingly, the solvent can exclude water in some instances. For example, the solvent can be galacial acetic acid. Suitable molar ratios of oxidant to solvent include, but are not limited to, a range from 1 :5 to 1:100, 1:20 to 1:80 and 1:30 to 1:50.

When the light transmitting medium 18 is silicon and the first medium is HN0₃, the HN0₃ reacts with the silicon to form Si0 . When the second medium is HF, the HF reacts with the SiO₂ to form H₂SiF₆, which enters the solution and is accordingly removed from the component 10. When the solvent is acetic acid, the smoothing etch can be performed at room temperature and room pressure. As a result, there is no need for elevated temperatures and/or pressures. In some instances, the solution components are selected to provide an etching rate of about 20 nm/min. The smoothing etch is performed until the desired level of smoothness is achieved. When the light transmitting medium 18 is silicon, the first medium is HN0 , the second medium is HF and the solvent is acetic acid, the smoothing etch can generally provide smoothing of the optical component 10 to a smoothness of less than 5 nm in a period of 1 to 10 minutes depending on the initial roughness of the surface 12 to be smoothed.

The smoothness that can be achieved with a smoothing etch that includes applying an oxidant and an oxide depends on the duration of the smoothing etch. For instance, a longer smoothing etch generally provides a smoother surface. The time that is required to achieve the desired level of smoothness depends on the conditions of the smoothing etch as well as the material being etched. In some instances, the surface has a roughness greater than 330 nm, 270 nm or 220 and the smoothing etch is performed for a duration that provides a surface having a roughness less than 330 nm, less than 270 nm, less than 220 nm, less than 170 nm, less than 100 nm, less than 40 nm, less than 20 nm, less than 15 nm, less than 10 nm, less than 4 nm or less than 1 nm. When the light transmitting medium is silicon, a smoothing etch that includes applying a solvent having HNO₃ and HF can provide smoothness on the order of 1 nm.

Another embodiment of the smoothing etch includes applying an etchant and/or applying a passivant to the component. Application of the etchant can be alternated with application of the passivant or the etchant and passivant can be applied concurrently. The passivant can react with the material that defines the surfaces 12 to provide a substance that evaporates. Because the passivant reacts with the tops of bumps that are responsible for the roughness of the surface 12 faster than the valleys between the bumps, the evaporation of the substance causes the tops of the bumps to be smoothed. As a result, the passivant enhances smoothing action of the etchant.

A suitable etchant includes, but is not limited to, HCL and a suitable passivant includes, but is not limited to, H₂. In some instances, the etchant and passivant are included in the etching medium of a dry etch such as a gas phase etch or a plasma etch. The dry etch can be an isotropic etch or an anisotropic etch. The etching medium can be about 0 - 100% volume % etchant, .2 - 80% volume % etchant, .4 - 40 volume % etchant, 1 - 20 volume % etchant or 3 - 5 volume % etchant. The portion that is etchant can be increased with increasing roughness of the surface 12 to be etched. Additionally, the ratio of etchant to passivant can be dynamic in that the portion that is etchant can be reduced as the smoothing etch progresses and the surface 12 becomes smoother. Alternatively, the portion that is etchant can be periodically increased and reduced in order to periodically increase and reduce the effects of the passivant. The etching medium can be formed before being delivered into the etching chamber or components that make up the etching medium can be independently delivered into the etching chamber.

The etching medium can be applied at about 900 - 1400 C, 1050 - 1200 C or 1050 - 1150 C at .05 - 100 SLM, .05 - 10.0 SLM, .1 -3 SLM or .2 - .8 SLM. At atmospheric pressure, temperatures above 1050 cause the surface 12 to reflow while temperatures above 1200 C can cause damage to crystal structures. Because reflow can enhance the surface 12 smoothness, temperatures in this range are preferred when the smoothing etch is performed at atmospheric pressure. However, the desired temperature range can change as the pressure is altered. Higher pressures can be employed when a surface 12 to be smoothed is near another surface 12. An example of where this can occur is between the adjacent waveguides 14 of an arrayed waveguide 14 grating. The proximity of the lateral sides 30 on adjacent waveguides 14 can prevent the desired amount of etching medium to penetrate between these waveguides 14. However, the pressure can be increased to facilitate penetration of the etching medium between the waveguides 14.

When the etchant is HCL and the passivant is H₂, the smoothing etch can be a dry etch such as a gas phase etch or a plasma etch. When the light transmitting medium is silicon, performing a dry etch under the conditions set out above can provide an etch rate of about 5 - 70 nm/min. Surface formation etches often provide an etch rates of about .5 -20 μm/min. Accordingly, the smoothing etch is typically slower than surface formation etches.

The smoothing etch can include application of the passivant alone. As noted above, the passivant can react with the material that defines the surfaces 12 to provide a substance that evaporates. Because the passivant reacts with the tops of bumps on the surface 12 faster than the valleys between the bumps, the evaporation of the substance causes the tops of the bumps to be smoothed. Accordingly, when the surfaces 12 are formed with a very low roughness, the passivant alone can provide the desired degree of smoothing.

The smoothness that can be achieved with a smoothing etch that includes applying an etchant and a passivant depends on the duration of the etch. For instance, a longer smoothing etch generally provides a smoother surface. The time that is required to achieve the desired level of smoothness depends on the conditions of the smoothing etch as well as the material being etched. In some instances, the surface has a roughness greater than 330 nm, 270 nm or 220 and the smoothing etch is performed for a duration that provides a surface having a roughness less than 330 nm, less than 270 nm, less than 220 nm, less than 170 nm, less than 100 nm, less than 40 nm, less than 20 nm, less than 15 nm, less than 10 nm, less than 4 nm or less than 1 nm. When the light transmitting medium is silicon, a smoothing etch that includes applying an etching medium including HCL and H₂ can provide smoothness on the order of 1 nm.

During a smoothing etch, one or more masks can be employed to protect regions of the component 10 where smoothing is not desired. The one or more masks are formed such that the regions of the component 10 where smoothing is desired remain exposed during the smoothing etch. When more than one surface 12 is to be smoothed, the level of smoothing desired on each of the surfaces 12 may be different. A smoothing etch can be performed until each surface 12 has the desired level of smoothness. Alternatively, one surface 12 can be masked and a smoothing etch can be performed on the exposed surface(s) 12 until the level of smoothness desired for those surfaces 12 is achieved. The mask can be removed and another mask formed so as to leave regions of the component 10 where additional smoothing is required exposed. A second smoothing etch can then be performed to achieve the desired level of smoothness desired for those surfaces 12 is achieved. This technique can provide surfaces 12 having different degrees of smoothness. In some instances, the effect of the smoothing etch on the dimensions of the light transmitting medium 18 should be taken into consideration. For instance, when the smoothing etch is performed such that .02 μm of light transmitting medium 18 are removed and a ridge with a width of 7 μm is desired, the component 10 should be fabricated such that the ridge has a width of 7.04 μm before the smoothing etch is performed. The excess width of the ridge compensates for the effects of the smoothing etch. The method of the present invention can also include performing one or more foreign substance removal operations before performing the smoothing etch. The foreign substance removal operations remove foreign substances from the surface(s) to be smoothed by the smoothing etch. Foreign substances include substances other than the material that defines the surface 12. Many of these foreign substances can act like a mask during the smoothing etch. Because the portion of the light transmitting medium 18 under a foreign substance that acts as a mask are not smoothed, these foreign substances can cause the surface(s) to have an increased roughness. Removing these foreign substances before performing the smoothing etch prevents the foreign substances from increasing the surface roughness.

Examples of foreign substances include, but are not limited to, mask left on the surface 12 from incomplete mask removal, polymer formed on the surface 12 during the surface formation etch and air born contaminants such as are often found in clean rooms. Another example of a foreign substance includes a portion of the surface that has converted from the material that defines the surface to another material. For instance, the one or more surfaces 12 can be defined by silicon. Exposure of the component 10 to air can cause the silicon to convert to silica. When this silica is not desired on the surface 12, the silica can serve as a foreign substance that acts as a mask during the smoothing etch. A suitable foreign substance removal operation includes an oxygen plasma cleaning. When a mask is constructed of photoresist, organic polymer or wax, the oxygen plasma cleaning can remove any mask left on the optical component 10. A suitable oxygen plasma cleaning step is performed with a 100% 02 plasma at 200 W of plasma power. Another suitable foreign substance removal operation includes a polymer residue cleaning. A polymer residue cleaning can remove polymers formed during a surface formation etch. A suitable polymer residue cleaning operation includes a wet etch performed in a solution of H₂S0 and H₂0₂. When the solution has a H₂S0₄:H₂0₂ molar ratio of about 17:1, the wet etch can be performed for about 15 minutes at about 90 °C. The wet etch can be followed by a deionized water rinse. Another suitable foreign substance removal operation includes a silica removal operation for removing silica formed on a silicon. An example of a silica removal operation includes a wet etch in a 2% solution of HF or a standard BOE solution.

Another suitable silica removal operation can include applying an etchant and/or applying a passivant to the component. Application of the etchant can be alternated with application of the passivant. In one embodiment, the silica removal operation includes applying an etchant and a passivant to the component in a gas phase. In some instances, the etchant and the passivant are applied concurrently. A suitable etchant for use with the silica removal operation includes, but is not limited to, HF and a suitable passivant for use with the silica removal operation includes, but is not limited to, H₂.

The passivant and/or the etchant can be applied in an etching medium having about 1-100 volume % etchant, 2-50% etchant or 5-10% etchant. The silica removal operation can be performed at about atmospheric pressure and temperatures from 0 - 100 C. In some instances, the silica removal operation is performed at room temperature. When the silica removal operation and the smoothing etch are dry etches, both etches can be performed in the same chamber. The etching medium can be applied at about .05 - 100 SLM, .05 - 10 SLM, .1 - 3 SLM or about .2 - .8 SLM.

When the component 10 is moved from performing the surface formation etch into the chamber for the smoothing etch without enough time for a foreign substance such as silica to form, the silica removal operation need not performed. Alternatively, if the surface formation etch and the smoothing etch are performed in the same chamber with little delay between etches, the silica removal operation need not be performed. Further, the silica removal operation need not be performed when the foreign substance does not affect the component performance or when the material that defines the one or more surfaces 12 is not subject to a tendency to convert to silica. Additionally, certain embodiments of the smoothing etch will remove silica. In instances, where the smoothing etch removes silica, the silica removal operation may not be necessary.

Although the component 10 and methods disclosed above are disclosed in conjunction with a ridge waveguide, the invention can be used with other types of optical components and other waveguide types. For instance, the invention can be used with components having channel waveguides. Additionally, the invention can be used to smooth surfaces 12 other than facets and sides of waveguides. For instance, the invention can be used to smooth the surfaces 12 of star couplers and Rowland circles. The components disclosed above are typically used in the 1550 nm wavelength range although the method disclosed above can be employed with optical components using much different wavelength ranges.

Other embodiments, combinations and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. Therefore, this invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings.

Claims

1. A method for smoothing a surface on an optical component, comprising: obtaining an optical component having one or more surfaces; and performing an etch so as to smooth the or more surfaces.

2. The method of claim 1 , wherein the one or more surfaces are include in a light transmitting medium positioned adjacent to a substrate.

3. The method of claim 1, wherein the one or more surfaces includes a facet through which light signals are transmitted.

4. The method of claim 1 , wherein the one or more surfaces includes a side of a ridge extending from a side of the component.

5. The method of claim 1 , wherein obtaining an optical component having one or more surfaces includes performing a surface formation etch so as to form the one or more surfaces.

6. The method of claim 5, wherein the surface formation etch is performed so as to be faster etch than the smoothing etch.

7. The method of claim 5, wherein the smoothing etch is a dry etch and the surface formation etch is a dry etch.

8. The method of claim 1 , further comprising: performing one or more foreign substance removal operations before performing the smoothing etch, the foreign substance removal operations being configured to remove foreign substances from the one or more surfaces to be smoothed by the smoothing etch.

9. The method of claim 8, wherein the one or more foreign substance removal operations includes at least one operation selected from a group consisting of an oxygen plasma clean, a polymer residue clean and a silica removal.

10. The method of claim 8, wherein the one or more foreign substance removal operations includes applying an etchant and a passivant to the optical component.

11. The method of claim 10, wherein the etchant is HF and the passivant is H₂.

12. The method of claim 1 , wherein the smoothing etch is an isotropic etch.

13. The method of claim 1 , wherein the smoothing etch is a gas etch.

14. The method of claim 1, wherein the smoothing etch is a wet etch.

15. The method of claim 1 , wherein performing the smoothing etch includes applying an etching medium having an etchant and a passivant to the component.

16. The method of claim 15, wherein the etchant includes HCL and the passivant includes H₂.

17. The method of claim 15, wherein the etching medium is .4 - 40 volume % etchant.

18. The method of claim 15, wherein the etching medium is 1 - 20 volume % etchant.

19. The method of claim 1 , wherein the smoothing etch is performed by applying an etching medium to the component, the etching medium having 3 - 5 volume % etchant.

20. The method of claim 1 , wherein the smoothing etch is performed at 900 - 1400 C.

21. The method of claim 1 , wherein performing the smoothing etch includes concurrently applying an oxidant and an oxide remover to the component.

22. The method of claim 21 , wherein the oxidant is HN0₃ and the oxide remover is HF.

23. The method of claim 21 , wherein a molar ratio of oxidant to oxide remover is within a range of 1 :1 to 1 :20.

24. The method of claim 21 , wherein a molar ratio of oxidant to oxide remover is within a range of 1 :4 to 1:8.

25. The method of claim 21 , wherein the oxidant and the oxide remover are ' included in a solution having a solvent that excludes water.

26. The method of claim 25, wherein the solvent includes acetic acid.

27. The method of claim 1, wherein the one or more surfaces have a roughness of greater than 220 nm before the smoothing etch and performing the smoothing etch provides the one or more surfaces with a smoothness less than 220 nm.

28. The method of claim 1, wherein the one or more surfaces have a roughness of greater than 150 nm before performing the smoothing etch and performing the smoothing etch provides the one or more surfaces with a smoothness less than 50 nm.

29. The method of claim 1, wherein obtaining an optical component having one or more surfaces includes receiving the optical component from a supplier.

30. A method for smoothing a surface on an optical component, comprising: obtaining an optical component having a material defining one or more surfaces; applying an oxidant to the one or more surfaces such that an oxide of the material is formed on the one or more surfaces; and applying an oxide remover to the one or more surfaces so as to remove the oxide from the one or more surfaces.

31. The method of claim 30, wherein the oxide remover is applied to the one or more surfaces concurrently with the oxidant.

32. The method of claim 30, wherein the one or more surfaces includes at least one surface selected from a group consisting of a surface through which light signals are transmitted and a surface at which light signals are reflected.

33. The method of claim 30, wherein the oxidant and the oxide remover are applied in a wet etch.

34. The method of claim 30, wherein the oxidant includes HN0₃ and the oxide remover includes HF.

35. The method of claim 30, wherein the oxidant and oxide remover are applied at a molar ratio of oxidant to oxide remover within a range of 1 : 1 to 1 : 20.

36. The method of claim 30, wherein the oxidant and oxide remover are applied at a molar ratio of oxidant to oxide remover within a range of 1 :4 to 1:8.

37. The method of claim 30, wherein the oxidant and the oxide remover are applied in a solution that excludes water.

38. The method of claim 30, wherein the solution includes acetic acid as a solvent.

39. The method of claim 30, further comprising: performing one or more foreign substance removal operations before applying the oxidant, the foreign substance removal operations being configured to remove foreign substances from the one or more surfaces to be smoothed.

40. The method of claim 30, wherein obtaining an optical component having one or more surfaces includes performing a surface formation etch so as to form the one or more surfaces.

41. The method of claim 30, wherein the oxidant is applied to the one or more surfaces such that the oxide is isotropically formed.

42. A method for smoothing one or more surfaces on an optical component, comprising: applying a first medium to the one or more surfaces of the optical component so as to converting a material that defines the one or more surfaces of the optical component to a second material; and applying a second medium to the one or more surfaces of the optical component so as to removing at least a portion of the second material from the one or more surfaces of the optical component.

43. The method of claim 42, wherein the second medium is applied concurrently with the first medium.

44. The method of claim 42, wherein the first medium is an oxidant that oxidizes the first material.

45. The method of claim 42, wherein the oxidant is HN0₃.

46. The method of claim 42, wherein second medium includes HF.

47. The method of claim 42, wherein the first medium and the second medium are applied to the one or more surfaces in a wet etch solution.

48. The method of claim 42, wherein the first medium is applied to the one or more surfaces of the optical component so as to isotropically convert the material that defines the one or more surfaces of the optical component to the second material.