JP4502719B2 - Optical element and optical element manufacturing method - Google Patents

Description

  The present invention relates to an optical element and a method for manufacturing the optical element.

  Conventionally, a joining technique is known in which a main body and an induction member both made of a glass material are joined by direct glass joining. For example, an organic alkaline solution is interposed between the joint surfaces of the induction member and the main body, the joint surfaces of the induction member and the main body are combined, and a pressure of about 3 kP to 1 MP is applied to the joint surface for an appropriate time. A method of leaving the glass, a fusion method in which the temperature of the induction member and the main body is increased to a temperature above the annealing point of the glass and the bonding surfaces of the induction member and the main body are fused, and the high melting point glass is used at a fusion temperature of 550 ° C. or higher. A method of bonding the induction member and the main body, a method of bonding the induction member and the main body with a low melting point glass while heating at a relatively low temperature, an induction by applying a voltage to the borosilicate glass layer by providing a borosilicate glass layer on the bonding surface An anodic bonding method for bonding a member and a main body is known.

A compound-eye optical system is also known in which a lens array is used for the purpose of thinning the optical system and the focal length is shortened. When the diameter of each lens of the lens array is very small, the light enters the optical path (lens diameter) of the adjacent lens when the light incident angle is 10 degrees or more. For this reason, when obliquely incident light from adjacent lenses is mixed with parallel light, crosstalk of light occurs. As an optical system for preventing this crosstalk of light, an optical element in which a lens barrel is bonded to a lens array is known (for example, see Patent Document 1).
JP 2001-242419 A

  However, in the conventional optical element described above, when each lens diameter of the lens array is very small, a lens barrel having a thickness of several mm to 10 mm corresponding to the lens diameter is manufactured at low cost, and the lens array is It has been difficult to position and fix the lens barrel with high accuracy.

  The present invention is intended to solve such a problem, and an optical element capable of positioning and fixing an optical component with high accuracy with respect to a support and a manufacturing method of the optical element with reduced costs. The main purpose is to provide

One aspect of the present invention for achieving the above object includes an optical component formed of glass and a signal separation partition having a plurality of openings formed of silicon, and the signal separation partition includes: is joined with Oite the optical components in the one end face, there is the light receiving element is joined at the other end face are joined by glass bonding between the optical components and the signal separating partitions, the light incident on the optical component is emitted from the optical components, passes through the opening in each of said signal separating partitions, characterized in der Rukoto those incident on the light receiving elements corresponding to the opening It is an optical element.

  In this embodiment, the end face of the support composed of a layer containing silicon dioxide, silicate or glass is bonded to the optical component by direct glass bonding. This makes it possible to position and fix the optical component with respect to the support with high accuracy, and to further reduce the cost.

One embodiment of the present invention includes two optical components formed of glass and a signal separation partition having a plurality of openings formed of silicon, and the signal separation partition has one end surface. The optical component is bonded to one of the optical components, and the other end surface is bonded to the other of the optical component, and the optical component and the signal separating partition are bonded by glass bonding, The light incident on the optical component is emitted from the one optical component, passes through each opening in the signal separation partition, and enters the other optical component corresponding to the opening. There is an optical element. Thereby, the said support body and the said optical component are positioned easily and with high precision.

According to another aspect of the present invention, the optical component is a microlens array , and the microlens constituting the microlens array and the opening provided in the signal separation partition have a one-to-one correspondence. It is the optical element characterized by the above.

In one embodiment of the present invention , a joint surface with the signal separation partition wall in the microlens array is provided between each microlens constituting the microlens array, and the signal separation in the microlens array is performed. The optical element is characterized in that a fitting portion for the bonding is provided on a bonding surface with the partition wall and a bonding surface with the microlens array in the signal separation partition wall.

  Since the support is silicon, a surface that does not reflect light can be formed as a secondary on the processed wall of the support. That is, it is not necessary to perform a special surface treatment on the processed wall surface of the support, and the cost of the optical element can be reduced.

Another embodiment of the present invention is a method in which an optical component is formed of glass, a photoresist is applied to a silicon substrate, and exposure and development are performed using an exposure mask to form a resist pattern. The step of forming a signal separation partition having a plurality of openings by removing silicon in a region where the pattern is not formed by dry etching, and the optical component and one end face of the signal separation partition by glass bonding A method for manufacturing an optical element .

In order to achieve the above object, the related art of the present invention provides an optical element comprising: an optical component made of silicon or glass; and a support that supports the optical component. Silicon dioxide is provided on an end surface of the support, A layer forming step for forming a layer containing silicate or glass, and a bonding step for directly bonding the end surface of the support on which the layer is formed and the optical component made of glass by glass bonding. This is a method for manufacturing an optical element.

  In this embodiment, between the layer forming step and the joining step, the end surface of the support and the joining surface of the optical component are fitted, and the support and the optical component are Preferably, the method further includes a positioning step of positioning.

  ADVANTAGE OF THE INVENTION According to this invention, the optical component which can position and fix an optical component with respect to a support body with high precision, or the manufacturing method of an optical element which reduced the cost can be provided.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. The basic concept of the thin image input system TOMBO (Thin Observation Module by Bound Optics), the main hardware configuration, the operating principle, the basic control method, and the like are known to those skilled in the art, and detailed description thereof is omitted. To do.

FIG. 1 shows a thin image input system TOMBO which is an example of the optical element of the present invention. The optical element 4 of the thin image input system 2 shown in FIG. 1 includes an optical component 6 such as a microlens array composed of 121 (11 × 11) glass microlenses 6a, and silicon dioxide SiO ₂ on one end face. And one end face is bonded to the microlens array 6 and includes a signal separation partition wall 8 as a support for partitioning light from each microlens. A light receiving element array 10 such as a CMOS (Complementary Metal-Oxide Semiconductor) that receives light from each microlens 6 a is joined to the other end face of the signal separation partition 8. Here, the light receiving element array 10 is composed of two polysilicon layers and three metal layers. The pixel pitch of the light receiving element array 10 is 12.5 μm, and the number of arranged pixels is 320 × 240 = 76800 (pieces). Further, an oxide film SiO ₂ is formed on the substrate surface of the light receiving element array 10.

  One microlens 6a and 36 light receiving elements 10a make a pair and are partitioned by a signal separation partition wall 8 to constitute a so-called one unit. Therefore, the thin image input system 2 is composed of 121 units. In such a thin image input system 2, an image is inverted and formed on the light receiving element array 10 via the microlens array 6.

  A computer is connected to the light receiving element array 10 via an interface circuit. The light receiving element array 10 converts the received light into an electrical signal and transmits it to the interface circuit. The interface circuit performs processing such as analog / digital conversion on the received electrical signal, and transmits the electrical signal subjected to this processing to the computer. The computer performs image reconstruction processing by an image rearrangement method or the like based on the received electrical signal, and reproduces a high-resolution two-dimensional image or three-dimensional image. Here, the processing of the pixel rearrangement method is performed as follows. First, the computer estimates geometric parameters for images from each unit. The computer then maps the pixels on the unit image onto the virtual image based on the estimated geometric parameters and the placement of the optical system. In addition, the computer performs complement processing on the pixels on the mapped virtual image. Further, the computer performs a digital filtering process on the complemented virtual image, and uses the processed image as an output image. In the above process, if the process is performed in consideration of the difference in the incident angles of light incident on the plurality of microlenses 6a, a three-dimensional image can be reproduced.

  Next, a method for manufacturing the optical element 4 of the thin image input system 2 will be described.

  FIG. 2 is a cross-sectional view in the A-A ′ direction of the thin image input system 2 in FIG. 1 and shows a state in which the microlens array 6, the signal separation partition 8, and the light receiving element array 10 are joined. FIG. 2 is an enlarged view of the three units of the optical element 4.

The microlens array 6 is formed of Neoceram (Nippon Electric Glass Co., Ltd.), which is a low expansion glass. First, a semiconductor photosensitive material layer is formed on neo-serum, and a three-dimensional initial structure is formed by a photolithography process in which a concentration distribution mask composed of a plurality of masks is sequentially aligned and exposed to the formed semiconductor photosensitive material layer. Form the body. Thereafter, neoceram is etched according to the shape of the formed three-dimensional initial structure to form a microlens array 6 having a desired shape. Further, an antireflection film for visible light wavelengths is formed on the surface of the microlens array 6. The uppermost layer of the formed antireflection film is a layer containing silicon dioxide SiO ₂ .

  The density distribution mask is composed of a plurality of masks created for different exposure areas, and a light shielding pattern having a two-dimensional light intensity distribution is formed on the transparent substrate in each exposure area of each mask. Each exposure region is divided by a unit cell having an appropriate shape and size without a gap. The light shielding pattern in each unit cell of each mask is set so that the transmitted light amount or the light shielding amount becomes a value corresponding to the height of the corresponding position of the photosensitive material pattern.

The signal separation partition 8 is formed of a substrate made of a silicon material for semiconductor having a thickness of 240 μm polished on both sides. In addition, a thermal oxide film (silicon dioxide SiO ₂ ) having a thickness of 1 μm is formed on one side of the polished substrate by normal processing of the semiconductor. Thereby, it is possible to prevent He leakage during the substrate cooling step described later. Further, a photosensitive material is applied on the surface of the silicon substrate on the side where the thermal oxide film SiO ₂ is not formed, and the surface on which the photosensitive material is applied is pre-baked. Further, the prebaked surface is exposed using an exposure mask, and development and rinsing are performed in a normal process. The developed and rinsed substrate is set in an ICP (Inductively Coupled Plasma) dry etching apparatus (manufactured by STS) and etched by the following method.

As an etching method, (1) a silicon substrate is set in a dry etching apparatus, and the cooling temperature of the silicon substrate is cooled to 5 ° C. (2) Etching with SF ₆ gas, and then switching to C ₄ F ₈ gas to form a protective film on the processed wall of the silicon substrate. Etching with SF ₆ gas and formation of a protective film with C ₄ F ₈ gas are repeated alternately (Bosch process). By this step (2), 121 holes 8b etched in the thermal oxide film SiO ₂ are formed in the silicon substrate. In the step (2), the SF ₆ gas flow rate is 200 sccm, the pressure is 25 mTorr, the bias is 50 W, the upper power is 2.0 kW, the etching rate is 5 μm / min, and the processing time is 4.5 seconds. Also, the C ₄ F ₈ gas flow rate is 100 sccm, the pressure is 20 mTorr, the bias is 5 W, the upper power is 1.8 kW, and the processing time is 3 to 4 seconds.

Next, the thermal oxide film SiO ₂ formed on the silicon substrate is directed downward and bonded to the backing substrate. Thereafter, the etching gas species is changed to CF ₄ gas, and etching is performed on 121 holes 8b formed on the silicon substrate under the same conditions as the C ₄ F ₈ gas described above. Thereby, 121 through holes 8b penetrating through the thermal oxide film SiO ₂ formed in the silicon substrate can be formed. Further, the photosensitive material on the silicon substrate and the thermal oxide film SiO _{2 are} washed to remove the photosensitive material.

  By the above processing, the shape of the signal separation partition 8 is as follows: pattern pitch dimension B: 720 μm, lattice width dimension C: 30 μm, depth D: 240 μm, wave shape of the wall surface 8c (side wall surface roughness height dimension: about 40 nm). (FIG. 3). In addition, you may process so that the height dimension of the side wall surface roughness of the wall surface 8c of the signal separation partition 8 may be set to about 20-40 nm. Since the processed wall surface 8c of the signal separation partition wall 8 is a polished glass surface having a surface roughness of about 40 nm, it is a light shielding surface that does not reflect light. By using silicon as the substrate material, it is possible to form a wave-shaped structure that does not reflect light on the processed wall surface 8c of the signal separation partition wall 8 during the etching. As a result, no special surface treatment is required on the wall surface 8c of the signal separation partition wall 8, and the cost of the optical element 4 can be reduced.

  A convex portion is formed on each joint surface of the microlens array 6, and a concave portion is formed on each end surface of the signal separation partition 8. These convex portions and concave portions are secondarily designed under the same processing conditions so as to be fitted to each other.

The microlens array 6 and the signal separation partition 8 manufactured as described above are bonded directly by glass bonding. First, 1% hydrofluoric acid is thinly applied to the end surface of the signal separation partition 8 having the thermal oxide film (SiO ₂ ) 8a by a tampo method (a method of applying only to a necessary surface) and brought into contact with the microlens array 6. The microlens array 6 and the signal separation partition 8 are aligned by fitting the projection formed on the joint surface of the microlens array 6 and the recess formed on the end surface of the signal separation partition 8. Is called. This makes it possible to align the microlens array 6 with the signal separation partition wall 8 easily and with high accuracy without requiring alignment using an electron microscope or the like.

  Next, a pressure of about 1.0 MPa is applied to the joint surface between the microlens array 6 and the signal separation partition 8 in this contacted state, and this pressure is maintained and maintained at 60 ° C. for 6 hours. Hold. Thereafter, the microlens array 6 and the signal separation partition 8 are washed with an organic solvent and vacuum dried.

It should be noted that the microlens array 6 and the signal separation partition are formed by glass bonding with a high melting point glass, a metal magnetic thin film, a ferromagnetic amorphous amorphous metal alloy, a low melting point fused glass, water glass, an organic adhesive, or the like. 8 may be joined. Further, a metal layer made of Cr or Ti is formed on each joint surface between the microlens array 6 and the signal separation partition wall 8, and a metal layer made of Au is laminated on the metal layer, and the metal layer made of Au is laminated. Au may thermally diffuse at a low temperature (150 ° C. to 300 ° C.), and the microlens array 6 and the signal separation partition 8 may be joined. The water lens mixed with glass powder may be used as an adhesive and heated to 1000 to 1100 ° C. to join the microlens array 6 and the signal separation partition 8. As the water glass curing agent, metastable phase Al (PO ₃ ) ₃ , calcium sulfoaluminate composition powder, silicate glass, powdered or acid-treated or esterified borosilicate glass may be used.

Next, the light receiving element array 10 is joined to the signal separation partition 8 to which the microlens array 6 is joined. First, a target object for positioning is set, and the light receiving element array 10 is positioned while confirming an image of the target object from the light receiving element array 10. When the position of the light receiving element array 10 is determined, the signal separation partition 8 and the light receiving element array 10 are joined at this position by an adhesive such as a UV curable adhesive. The signal separation partition 8 and the light receiving element array 10 are bonded by an adhesive, but an oxide film SiO ₂ may be formed on the other end face of the signal separation partition 8 and bonded directly by glass bonding.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications and substitutions are made to the above-described embodiments without departing from the scope of the present invention. be able to.

  For example, although the microlens array 6 is used as an optical component, a diffractive optical element array may be used. The diffractive optical element array is a Fresnel optical element in which the central annular zone has the largest pitch and the pitch decreases toward the outer periphery. Further, the lens height is highest in the central annular zone and becomes lower toward the outer periphery. Specifically, the maximum lens height of the diffractive optical element array is 1.2 μm, and the number of annular zones is 75 annular zones.

The diffractive optical element array is made of a neo-ceram material that is a low expansion glass. First, a photosensitive material for electron beam (Electron Beam resist) is uniformly applied to a neo-serum material with a thickness of 2.0 μm, and the uniformly coated surface is pre-baked and then diffractive optical element by an electron beam drawing device. Mold into a three-dimensional design shape of the array. Next, the molded photosensitive material having the three-dimensional design shape is dry-etched to transfer the three-dimensional design shape to the neoceram material, and is molded into a desired diffractive optical element array shape. Further, an antireflection film for visible light wavelength is formed on the surface of the molded diffractive optical element array on the side to be joined with the signal separation partition 8. The thin film is designed so that the uppermost layer of the antireflection film is SiO ₂ .

  Although the microlens array 6 is bonded to one of the two end surfaces of the signal separation partition wall 8, the microlens array 6 may be bonded to the two end surfaces of the signal separation partition wall 8 as shown in FIG. . The optical element shown in FIG. 4 can form an image upright through two microlenses.

In the above embodiment, the optical element 4 according to the present invention is used in the thin image input system 2. However, the present invention is not limited to this, and may be used in a writing optical system of a digital camera or a copying machine. .
Furthermore, although the microlens array 6 is used as an optical component, a wavefront lens may be used.

  Here, the wave front lens is used in the Wavefront Cording System proposed by the US CDM Optics, and the optical lens, the image sensor (CCD), and the image processing software are designed and optimized when integrated. It is an optical lens.

  The image formed on the image sensor by the wave front lens does not need to be an image that can be recognized by humans. That is, in the above Wavefront Cording System, it is sufficient that a final image processed by the image processing software can be recognized by a human. Therefore, this image processing software performs image processing and image compression on an image dedicated to the image sensor. By using this Wavefront Cording System, the depth of field can be increased without reducing the F value, and both brightness and the depth of field limit can be achieved. In addition, various aberrations can be greatly reduced with a simple lens configuration, and the optical system can be made compact and inexpensive. Furthermore, a high-resolution image can be obtained.

  INDUSTRIAL APPLICABILITY The present invention can be used for a thin image input system employed in a personal information terminal having an image information input function.

It is a figure which shows the thin image input system which concerns on an example of the optical element of this invention. FIG. 2 is a cross-sectional view in the A-A ′ direction of the thin image input system 2 in FIG. 1, illustrating a state in which a microlens array, a signal separation partition, and a light receiving element array are joined. It is an enlarged view of the signal separation partition of an optical element. It is a figure which shows the state which joined the micro lens array to the two end surfaces of a signal separation partition.

Explanation of symbols

2 Thin Image Input System 4 Optical Element 6 Micro Lens Array 6a Micro Lens 8 Signal Separation Partition 8a Oxide Film SiO ₂
8b hole 8c wall surface 10 light receiving element array 10a light receiving element

Claims (5)

Optical components formed of glass;
A signal separating partition having a plurality of openings formed of silicon;
The a, the signal separating partitions is joined to Oite the optical components in the one end face, there is the light receiving element is joined at the other end face,
The optical component and the signal separation partition are bonded by glass bonding ,
The light incident on the optical component is emitted from the optical components, passes through the opening in each of said signal separating partitions, characterized in der Rukoto those incident on the light receiving elements corresponding to the opening An optical element. Two optical components formed of glass;
  A signal separating partition having a plurality of openings formed of silicon;
  The signal separation partition is bonded to one of the optical components at one end face, and is bonded to the other of the optical components at the other end face,
  The optical component and the signal separation partition are bonded by glass bonding,
  Light incident on the one optical component is emitted from the one optical component, passes through each opening in the signal separation partition, and enters the other optical component corresponding to the opening. An optical element characterized by being a thing. It said optical component is a microswitch lens array,
Wherein the microlenses constituting the microlens array, the signal from the opening provided in the separating partitions, optical element according to claim 1 and 2, characterized that you have a one-to-one correspondence. The joint surface with the signal separation partition in the microlens array is provided between each microlens constituting the microlens array,
And junction surface between the signal separating partitions in the microlens array, the junction surface between the micro lens array in the signal separating partition wall, said the fitting portion for said joining is al provided The optical element according to claim 3 . Forming optical components with glass;
Forming a signal separation partition wall by forming a plurality of openings penetrating the silicon substrate in the silicon substrate;
Bonding the optical component and one end face of the signal separation partition by glass bonding;
The method for manufacturing an optical element characterized Rukoto to have a.

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