Patent Application
20080316608
This application claims the priority of Application No. 2007-165700, filed Jun. 23, 2007 in Japan, the subject matter of which is incorporated herein by reference.
The present invention relates to a micro-lens manufactured using a semiconductor substrate (silicon wafer). In particular, the present invention relates to a method of assessing to determine an error in an external shape in a manufacturing process of the micro-lens.
Optical communication using an optical fiber represented by Fiber To The Home (FTTH) has become widely used. So called an “optical module” configured by aligning a laser as a light source and an optical fiber or an optical fiber and an optical receiver with high accuracy has been proposed.
Patent Document 1 (Japan Patent Publication Number 3696802) disclosed a technology to manufacture a micro-lens with a size in an order of a few hundred micrometers using a lithography and etching technology, which is a semiconductor manufacturing technology. According to Patent Document 1, a semiconductor laser beam source, a micro-lens and an optical fiber are mounted on a common silicon substrate. Use of such a structure allows a beam emitted from a semiconductor laser effectively to couple with the optical fiber.
In Patent Document 1, a peripheral portion of the micro-lens is manufactured in the same diameter as the optical fiber. The peripheral portion of the micro-lens is thus mounted butting against a common V-groove to realize aligning the optical fiber with the optical axis of the micro-lens within the vertical plane.
Accordingly, mounting accuracy of a micro-lens is assured by butting the peripheral portion thereof, for example, against a V-groove so that there is a need to improve manufacturing accuracy of the micro-lens in order to increase mounting accuracy.
In order to satisfy the requirement for such high accuracy in manufacturing, Patent Document 2 (Japan Patent Publication Laid Open Number 2003-161811) disclosed a means of manufacturing a lens portion of a micro-lens in the photolithography and etching processes followed by similarly manufacturing the external wall portion of the micro-lens in the photolithography and etching processes while keeping alignment relatively with such a lens portion with high accuracy. The external wall portion of the micro-lens is required to be etched in a range of 100 μm (micro meters) deep, while the lens portion is etched only in a range of 1 μm (micro meters) deep. This makes very difficult manufacturing both portions with high accuracy in a single etching process.
When a micro-lens is manufactured in two etching processes as described above, an amount of an eccentric error in the optical axis of a completed lens is affected by both accuracy of aligning the peripheral pattern of a lens in a second process with the pattern of the lens portion in a first process and a manufacturing error in a diameter of the peripheral pattern. A scanning electron microscopy (SEM) equipment or microscope with several hundred magnifications is required to measure an error in a diameter of the peripheral pattern manufactured in a substrate as a batch with accuracy in a level of submicrons particularly in a micro-lens with the lens diameter of several hundred microns. There is also a problem such as a need for more manpower and higher cost for measurement (assessment).
Patent Document 1: Japan Patent Publication Number 3696802
Patent Document 2: Japan Patent Publication Laid Open Number 2003-161811
The present invention has been carried out under the conditions described above and has a first purpose to provide a method of enabling to assess in a simple and highly accurate manner an amount of misalignment with the optical axis caused by an error in a manufacturing process of a micro-lens.
Other purpose of the present invention is to provide a method of manufacturing a micro-lens, in which an amount of misalignment with the optical axis caused by an error in a manufacturing process of the micro-lens can be assessed in a simple and highly accurate manner.
A yet another purpose of the present invention is to provide a micro-lens, in which an amount of misalignment with the optical axis caused by an error in a manufacturing process of a micro-lens can be assessed in a simple and highly accurate manner.
Additional objects, advantages and novel features of the present invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
A first aspect of the present invention is applied to a micro-lens manufactured using a semiconductor substrate. A lens portion, a peripheral portion located outside the lens portion and a mark for assessment near the peripheral portion formed during a process to form the lens portion are provided.
A micro-lens of the present invention is preferably the micro-lens manufactured using a semiconductor substrate and applied to the micro-lens aligning to mount in a groove with a V-shaped cross-section formed on the semiconductor substrate for an optical module. The micro-lens according to the present invention is then provided with a lens portion, a peripheral portion located outside the lens portion and a mark for assessment near the location, where the peripheral portion contacts the groove during a process to form the lens portion.
According to the configuration of the present invention described above, a lens portion and a pattern of assessing an error are simultaneously manufactured in advance to form the peripheral portion of lens followed by visual inspection of the pattern appearance, thus allowing to easily assess whether an amount of misalignment with the optical axis is within a specification (permissible range (dimensional tolerance)). That is, an error in manufacturing the lens and the external shape of lens are not required to be measured in high accuracy.
Specifically, after a pattern mark (D-RIE TEG) to assess a dimensional error of the central portion of a lens with the external wall portion of a lens is manufactured simultaneously, the external wall portion of the lens is deeply etched and the surface of this lens is then inspected by an SEM equipment or microscope. On this occasion, for example, when a pattern mark of D-RIE TEG is deficient, this is determined as a dimension of the external wall portion of lens is manufactured smaller than the value in specification. Thus, instant determination becomes possible without fresh measurement of a lens diameter.
A second aspect of the present invention is applied to a method of assessing a micro-lens having a lens portion and a peripheral portion located outside said lens portion. In such a method, accuracy of manufacturing said micro-lens is assessed by forming a mark for assessment near said peripheral portion in the same process as formation of said lens portion when the lens portion is formed on a semiconductor substrate and observing a positional relation between the mark and the peripheral portion after completing formation of the peripheral portion.
The mark can be provided so as to contact said peripheral portion, when the peripheral portion is located inside (smaller than) or outside (larger than) the permissible range (dimensional tolerance).
The mark corresponds to the permissible range (dimensional tolerance) for the location of the peripheral portion and can be provided so that the peripheral portion contacts said mark when the peripheral portion is located inside the permissible range (dimensional tolerance).
The mark is composed of a pair of mark elements formed at a predetermined interval and the interval of a pair of such mark elements corresponds to the permissible range (dimensional tolerance) for the location of the peripheral portion, allowing to determine to be normal when the peripheral portion is located between a pair of the mark elements.
The mark can be formed at least in two locations near the peripheral portion.
The mark can be formed in a continuously elongated form along the peripheral portion.
The micro-lens can be aligned using part of the peripheral portion as a contact when mounted. In this occasion, the mark is preferably formed near a location of the contact.
The lens portion and the mark can be formed by a photolithography and etching technology using a same mask.
A third aspect of the present invention is applied to a method of assessing a micro-lens aligned to mount in a groove with a V-shaped cross-section formed on a semiconductor substrate. In this case, the micro-lens has a lens portion and a peripheral portion located outside said lens portion and contacted with the inclined inner wall of above groove. A mark for assessment is formed near the location, where the peripheral portion contacts with the groove according to the same process as formation of said lens portion, when forming the lens portion on a semiconductor substrate. After completing formation of the peripheral portion, a positional relation of the mark with the peripheral portion can be observed to assess manufacturing accuracy of said micro-lens.
The mark can be provided so as to contact the peripheral portion, when the peripheral portion is located inside (smaller than) or outside (larger than) the permissible range (dimensional tolerance).
The mark corresponds to the permissible range (dimensional tolerance) for the location of the peripheral portion and can be provided so that the peripheral portion contacts said mark, when said peripheral portion is located inside the permissible range (dimensional tolerance).
The mark is composed of a pair of mark elements formed at a predetermined interval and the interval of a pair of such mark elements corresponds to the permissible range (dimensional tolerance) for the location of the peripheral portion, allowing to determine to be normal when the peripheral portion is located between a pair of the mark elements.
The lens portion and the mark can be formed by a photolithography and etching technology using a same mask.
A fourth aspect of the present invention is applied to a method of manufacturing a micro-lens having a lens portion and a peripheral portion located outside said lens portion. In a such method, a lens portion is formed on a semiconductor substrate by a photolithography and etching technology, a mark for assessment is formed near an area, where the peripheral portion is formed in a process to form the lens portion and an external shape of the micro-lens is defined by forming the peripheral portion after forming the lens portion and the mark.
The mark can be provided so as to contact the peripheral portion, when said peripheral portion is located inside (smaller than) or outside (larger than) the permissible range (dimensional tolerance).
The mark corresponds to the permissible range (dimensional tolerance) for the location of the peripheral portion and can be provided so that the peripheral portion contacts said mark, when the peripheral portion is located inside the permissible range (dimensional tolerance).
The mark is composed of a pair of mark elements formed at a predetermined interval and the interval of a pair of such mark elements can be configured to correspond to the permissible range (dimensional tolerance) for the location of the peripheral portion. In this occasion, a pair of the mark elements is preferably provided to locate therebetween, when the peripheral portion is located inside the permissible range (dimensional tolerance).
The mark can be formed at least in two locations near the peripheral portion.
The mark can be formed in a continuously elongated form along the peripheral portion.
The micro-lens can be aligned using part of the peripheral portion as a contact when mounted. In this occasion, the mark is preferably formed near a location of the contact.
The lens portion and the mark can be formed by a photolithography and etching technology using a same mask.
A fifth aspect of the present invention is a micro-lens aligned to mount in a groove with a V-shaped cross-section formed on a semiconductor substrate and applied to a method of manufacturing the micro-lens having a lens portion and a peripheral portion located outside said lens portion and contacted with the inclined inner wall of the groove. In such a method, the lens portion is formed on a semiconductor substrate by a photolithography and etching technology, a mark for assessment is formed near the location, where the peripheral portion contacts the groove in a process to form the lens portion and an external shape of the micro-lens is defined by forming the peripheral portion after forming the lens portion and the mark.
The mark can be provided so as to contact the peripheral portion, when said peripheral portion is located inside (smaller than) or outside (larger than) the permissible range (dimensional tolerance) .
The mark corresponds to the permissible range (dimensional tolerance) for the location of the peripheral portion and can be provided so that the peripheral portion contacts said mark, when the peripheral portion is located inside the permissible range (dimensional tolerance).
The mark is composed of a pair of mark elements formed at a predetermined interval and the interval of a pair of such mark elements can be configured to correspond to the permissible range (dimensional tolerance) for the location of the peripheral portion. In this occasion, a pair of the mark elements is preferably located therebetween when the peripheral portion is located within the permissible range (dimensional tolerance).
In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific preferred embodiments in which the inventions may be practiced. These preferred embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other preferred embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit and scope of the present inventions. The following detailed description is, therefore, not to be taken in a limiting sense, and scope of the present inventions is defined only by the appended claims.
A method of two-way communication by the optical communication module shown in
The received light 120 emitted from the optical fiber 112 in receiving passes through a ball lens 114 and is then refracted by 90 degrees at a reflective coating of the wavelength filter 108 to reach the micro-lens 105 on receiving side. After the received light 120 is diffracted at the lens 105, it passes through an inside of the V-groove 102 on receiving side and is reflected at a reflection plane (not shown) formed at an end plane of the V-groove 102 to reach through the glass element 107 a light acceptance surface of PD 106 mounted on a top surface thereof.
In manufacturing of a micro-lens, a silicon dioxide film 132 is at first formed on a silicon substrate 130. The silicon dioxide film 132 serves as an etch stopper in a post-process. A device-forming layer 134 consisted of a silicon substrate (SOI substrate) is next formed on the oxide film 132. The device-forming layer 134 is the part serving as a lens element in a post-process. The device-forming layer 134 is formed in thickness substantially same as the lens element in the direction of the optical axis, which forms a final shape in the process described below.
As shown in
In a case shown in
In a case shown in
In the present embodiment, a lens portion 20 has a circular shape, and is composed of a diffraction optical element. The lens portion 20 can be formed with a computer-generated hologram (CGH) element, which is one of diffraction optical elements. As well known heretofore, in a CGH element, a photomask pattern required to obtain desired optical properties is obtained using a computer from a function of optical path difference for an optical element exhibiting desired optical properties, followed by an etching treatment at a desired location of an optical substrate using such a mask pattern to form a diffraction type optical element exhibiting desired optical properties. An etching treatment at a desired location of the optical substrate using a photomask pattern thus enables to form the lens portion 20 exhibiting desired diffraction optical properties.
A lens portion 20 is not limited to have a diffraction type lens surface described above, but may have a refraction type lens surface. The lens portion 20 is also not limited to have a circular shape described above, but may be formed in a desired planar shape.
As shown in
A device-forming layer 134 is formed in thickness substantially same as a lens element in a direction of the optical axis, which forms a final shape in the process described below. A crystalline substrate such as a crystalline silicon substrate can be used as a device-forming layer 134, when incident light is light with wavelength, for example, 1.3 μm (micro meters) or 1.5 μm (micro meters).
A lens portion 20 is formed in an n×m array at a regular interval (not shown) on a top surface of a device-forming layer 134 in a state of a wafer. The lens portion may be formed in a stepwise shape as a Fresnel lens. The Fresnel lens can be formed by repeating photolithography and etching several times. A method described in Japan Patent Publication Laid Open Number 2006-343461 can be used to form a stepwise shape in the lens portion 20.
In
It is important to form a mark 124 simultaneously in a step forming a lens portion 20. That is, a pattern for the mark 124 is formed on the same mask as a mask used in formation of the lens portion 20. When a plurality of processes to form the lens portion 20 is involved, a mark 124 is formed in any one of the processes. The mark 124 is formed simultaneously in a step forming the lens portion 20, so that a relation of relative position of the lens portion 20 with the mark 124 can be accurately defined. In the present embodiment, the mark 124 is now shaped concave by etching.
In this embodiment, a mark 124 is configured so as to contact a value of specified dimension for a peripheral portion 22. The mark 124 is provided so as to contact said peripheral portion 22 when the peripheral portion 22 is located inside (smaller than) the permissible range (dimensional tolerance) relative to a lens portion 20.
When an external shape of a micro-lens is manufactured, photolithography is next used to fabricate a pattern on a photoresist applied to a device-forming layer 134 into a shape of a lens element. This resist is used as an etching mask for dry etching to transfer the shape of this photoresist onto a device-forming layer 134, manufacturing an external shape of a peripheral portion 22 of a micro-lens. A reactive ion etching (RIE) method, an inductively coupled plasma (ICP)-Bosch method (silicon deep-etching process) and the like can be used as a drying etching technique used herein. In this time, the device-forming layer 134 fabricated to a pattern is an SOI substrate, which is etched deep enough to reach to an oxide film 132, for example, by the ICP-Bosch method.
As shown in
According to the present embodiment, both cases where an external shape of a lens is too large or too small can be detected as being dimensionally abnormal. A mark 224 in a normal state is detected smaller than a design value when observed by a microscope and the like. A lens is determined to be dimensionally abnormal when the mark 224 is observed as big as a design value (left from
In the present embodiment, a mark 324 for assessing an external shape of a lens is consisted of a pair of mark elements 324a and 324b formed at a predetermined interval as shown in
According to the present embodiment, both cases where an external shape of a lens is too large or too small can be detected as being dimensionally abnormal similar to the second preferred embodiment described above. Only a mark element 324a is detected in a normal state when observed by a microscope and the like as shown in a middle of
Two locations among five locations of the mark 424 are preferably near the contacts S1 and S2 with the V-grooves (101 and 102). This can realize effectively controlling dimensional accuracy of a lens.
A method of assessing an external shape of a micro-lens using a mark 524 can use any one used in the first to third preferred embodiments described above. The mark 524 in this figure is a single continuous form, but may use two marks parallel to each other as in the third preferred embodiment. In the present embodiment, the continuous mark 524 contains contacts S1 and S2 with the V-grooves (101 and 102), enabling to realize effectively controlling dimensional accuracy of a lens. For example, an area near contacts (S1 and S2) (encircled area) is preferably observed when the peripheral portion 22 is observed with a microscope and the like.
In the present embodiment, a cylindrical outer wall (22) of a micro-lens contacts an inner side surface of the V-grooves (101 and 102) at two locations (S1 and S2). Thus, it is good enough for a side wall (22) of a lens to satisfy a design specification only around said contacts (S1 and S2). In the present embodiment, a mark 624 for assessment is provided near the contacts (S1 and S2) between this external wall (22) of a lens and an inner side surface of the V-grooves (101 and 102) to realize effectively controlling dimensional accuracy of a lens. A configuration of the mark 624 itself can use any one of the configurations and methods in the first to third preferred embodiments described above.
An undersurface 700a of a support 700 contacts a surface of a semiconductor substrate 100 (
In the present embodiment, a support (handling portion) 700 having, for example, a length of 250 to 300 μm (micro meters), is integrally formed on one side of a circular lens portion 20. The support 700 is integrally formed on an edge of an lens portion 20 so as to surround an upper half of said edge at an intermediate section between both ends of the support. The support 700 extends linearly in lateral direction such that it is bilaterally symmetrical with respect to a hypothetical plane passing through an optical axis of a lens portion 20, that is, a vertical plane. The support is formed in a rectangular cross-sectional shape as a whole having a dimension in height H, for example, of 100 to 200 μm (micro meters) and a dimension in lateral direction, for example, of 100 to 200 μm (micro meters). An arced peripheral portion 22 along an outer edge of a lens portion 20 is integrally formed in an opposite side of the support 700 in the edge of said lens portion 20.
In the present embodiment, not only a mark on a lens section mounted on the V-grooves (101 and 102) but also a mark 724 for validating accuracy of manufacturing a support 700 are provided to enable improving accuracy of mounting a micro-lens as a whole. A configuration of the mark 724 itself may use any one of the configurations and methods in the first to third preferred embodiments described above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-165700 | Jun 2007 | JP | national |
