Manufacturing process for a spectroscopic sensor

Abstract

A manufacturing method of a spectroscopic sensor (1) comprising an interference filter unit (20, 20A, 20B) having a cavity layer (21) and first and second mirror layers (22, 23) opposite each other across the cavity layer (21); for selectively transmitting light in a predetermined wavelength range according to a respective incident position; and a light-transmitting substrate (3) for transmitting light incident on the interference filter unit (20, 20A, 20B); and a light-detecting substrate (4) for detecting the light transmitted through the interference filter unit (20, 20A, 20B); the method comprising: Forming a silicon oxide film (52) by thermal oxidation on one of main sides (51a, 51b) of the support substrate (51) made of silicon, the silicon oxide film (52) being used as a surface layer (53); Forming a cavity layer (21) by etching the surface layer (53) arranged on a carrier substrate (51); Forming a first mirror layer (22) on the cavity layer (21) after forming the cavity layer (21); Bonding the light-transmitting substrate (3) to the first mirror layer (22) after forming the first mirror layer (22); Removing the carrier substrate (51) from the cavity layer (21) after bonding the light-transmitting substrate (3); Forming the second mirror layer (23) on the cavity layer (21) which is free from the carrier substrate (51) after removing the carrier substrate (51); and Bonding the light-detecting substrate (4) to the second mirror layer (23) after forming the second mirror layer (23).

Description

Technical area

[0001] The present invention is a method for manufacturing a spectroscopic sensor. State of the art

[0002] A conventional spectroscopic sensor is known that includes an interference filter unit for transmitting light having a predetermined wavelength according to a light incidence position, a light-transmitting substrate for transmitting the light incident on the interference filter unit, and a light-detecting substrate for detecting the light transmitted through the interference filter unit. A pair of mirror layers may be opposed to each other via a cavity layer to form the interference filter unit as a Fabry-Perot type.

[0003] As a method for manufacturing such a spectroscopic sensor, the following method is disclosed in Patent Literature 1. First, a mirror layer is formed on a light-detecting substrate, and then a cavity layer is formed on the mirror layer by a nano-imprint process. Subsequently, another mirror layer is formed on the cavity layer, and finally, a light-transmitting substrate is bonded to the resulting mirror layer. Patent literature list Patent Literature 1: International Publication No. WO 2008 / 017 490 A2 Patent literature 2: US 2010 / 0 053 755 A1 Patent Literature 2 describes a plasmonic Fabry-Perot filter comprising a first partial mirror and a second partial mirror separated from the first partial mirror by a gap. At least one of the first partial mirror or the second partial mirror comprises an integrated plasmonic optical filter array. Summary of the inventionTechnical problem

[0004] However, the method for manufacturing a spectroscopic sensor disclosed in Patent Literature 1 is associated with the risk that the manufactured spectroscopic sensor will have reduced reliability. The reasons for this are as follows. Since irregularities caused by the formation of a light-receiving unit, a wiring layer, and the like exist on the surface of the light-detecting substrate, there is a high risk of achieving a cavity layer with high precision (for example, on the order of nm) when the cavity layer is formed by a nano-imprint process on the mirror layer formed on such a surface.Moreover, since the mirror layers and the cavity layer are formed to be stacked on the light-detecting substrate, any process is likely to damage the light-detecting substrate.

[0005] It is therefore an object of the present invention to provide a method for manufacturing a spectroscopic sensor which results in a highly reliable spectroscopic sensor. Solution to the problem

[0006] The method for manufacturing a spectroscopic sensor according to one aspect of the present invention is a method for manufacturing a spectroscopic sensor comprising an interference filter unit having a cavity layer and first and second mirror layers opposite each other across the cavity layer for selectively transmitting light in a predetermined wavelength range according to an incident position thereof; a light-transmitting substrate for transmitting light incident on the interference filter unit; and a light-detecting substrate for detecting the light transmitted through the interference filter unit; the method comprising: a first step of forming the cavity layer by etching a surface layer disposed on a support substrate; a second step of forming the first mirror layer on the cavity layer after the first step;a third step of bonding the light-transmitting substrate to the first mirror layer after the second step; a fourth step of removing the support substrate from the cavity layer after the third step; a fifth step of forming the second mirror layer on the cavity layer free from the support substrate after the fourth step; and a sixth step of bonding the light-detecting substrate to the second mirror layer after the fifth step.

[0007] The manufacturing method for a spectroscopic sensor forms a cavity layer by etching a surface layer disposed on a support substrate. Forming the cavity layer using the support substrate in this way can provide the cavity layer with high precision. After forming the cavity layer and the first and second mirror layers on the side of the light-transmitting substrate, the light-detecting substrate is bonded. This can prevent the light-detecting substrate from being damaged during the processes of forming the cavity layer and the mirror layers. This manufacturing method for a spectroscopic sensor can thus produce a highly reliable spectroscopic sensor.

[0008] Here, before the first step, a silicon oxide film can be formed on one of the main surfaces of the silicon support substrate, and the silicon oxide film can be used as the surface layer. This can stably provide a high-quality cavity layer at a low cost.

[0009] Before the first step, both major surfaces of a silicon substrate are thermally oxidized to form silicon oxide films on both major surfaces of the silicon support substrate. The silicon oxide film formed on one of the major surfaces of the support substrate can be used as the surface layer. This inhibits warping of the support substrate, allowing the cavity layer to be obtained with higher precision.

[0010] An optical filter layer for transmitting light in the predetermined wavelength range may be formed on the light-transmitting substrate prior to the third step, and the light-transmitting substrate may be bonded to the first mirror layer in the third step so that the first mirror layer and the optical filter layer are opposite each other. This allows the light in the predetermined wavelength range to be efficiently incident on the interference filter unit. Advantageous effects of the invention

[0011] The present invention can produce a highly reliable spectroscopic sensor. Short description of the drawings Fig. 1 is a vertical cross-sectional view of a spectroscopic sensor manufactured by the manufacturing method of the spectroscopic sensor according to an embodiment of the present invention; Fig. Figure 2 is a plan view of a cavity layer in the spectroscopic sensor according to Fig. 1; Fig. 3 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. Fig. 4 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. 5 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. 6 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. Fig. 7 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. Fig. 8 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. 9 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. 10 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. 11 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. 12 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. 13 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. 14 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. 15 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. 16 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. 17 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. 18 is a vertical cross-sectional view for explaining a method of manufacturing the spectroscopic sensor according to Fig. 1; Fig. 19 is a profile diagram showing the relationship between a resist layer and the cavity layer; Fig. 20 is a plan view of a support substrate formed with the resist layer; Fig. 21 is a vertical cross-sectional view of a modified example of the spectroscopic sensor according to Fig. 1; and Fig. 22 is a plan view of the cavity layer in the spectroscopic sensor according to Fig. 20. Description of the embodiments

[0012] Preferred embodiments of the present invention will now be explained in detail with reference to the drawings. In the drawings, the same or equivalent elements are referred to by the same reference numerals, thereby avoiding repetitive description.

[0013] How Fig. 1, a spectroscopic sensor 1 comprises an interference filter unit 20 for selectively transmitting light in a predetermined wavelength range according to a respective incident position, a light-transmitting substrate 3 for transmitting the light incident on the interference filter unit 20, and a light-detecting substrate 4 for detecting the light transmitted through the interference filter unit 4. The spectroscopic sensor 1 is formed from a rectangular parallelepiped-like CSP (Chip Size Package), each side having a length of several hundred µm to several tens of mm.

[0014] The light-transmitting substrate 3 is made of glass or the like and formed into a rectangular plate having a thickness on the order of 0.2 to 2 mm. An optical filter layer 5 is formed on the back surface 3b of the light-transmitting substrate 3 to oppose the interference filter unit 20. The optical filter layer 5, which is a dielectric multilayer film or an organic color filter (color photoresist), is formed into a rectangular film having a thickness on the order of 0.1 to 10 μm. The optical filter layer 5 functions as a bandpass filter for transmitting light in the predetermined wavelength range therethrough to be incident on the opposing interference filter unit 20.

[0015] The light-detecting substrate 4, which is a photodiode array, is formed into a rectangular plate having a thickness on the order of 10 to 150 μm. The front surface 4a of the light-detecting substrate 4 is formed with a light-receiving unit 6 for receiving the light transmitted through the interference filter unit 2. The light-receiving unit 6 is formed by one-dimensionally arranged extended photodiodes along the longitudinal direction of the light-detecting substrate 4, each photodiode extending along a direction substantially perpendicular to the longitudinal direction of the light-detecting substrate 4. The light-detecting substrate 4 is further formed with leads 7 (front wiring, back wiring, through wiring, etc.) for outputting electrical signals photoelectrically converted by the light-receiving unit 6.The back surface 4b of the light-detecting substrate 4 is provided with surface-arranged bumps 8 that are electrically connected to the terminals or wires 7. The light-detecting substrate 4 is not limited to a photodiode array, but may also be one of other semiconductor light-detecting elements (C-MOS image sensors, CCD image sensors, and the like).

[0016] The interference filter unit 20 includes a cavity layer 21 and DBR (Distributed Bragg Reflector) layers 22, 23. In the interference filter unit 20, the DBR layers (first and second mirror layers) 22, 23 face each other via the cavity layer 21. That is, the cavity layer 21 maintains a distance between the opposing DBR layers 22, 23. Each of the DBR layers 22, 23 is a dielectric multilayer film made of SiO2, TiO2, Ta2O5, Nb2O5, Al2O3, MgF2, or the like, and is formed into a rectangular film with a thickness on the order of 0.1 to 10 µm.

[0017] The cavity layer 21 is a silicon oxide film (SiO2 film) formed by thermally oxidized silicon, with a thickness in the range of 100 nm to several µm. Fig. 1 and Fig. 2, the cavity layer 21 has a filter region 24, a surrounding region 25 and a connecting region 26 which are formed integrally.

[0018] The filter region 24 is formed in a rectangular film, each side of which has a length on the order of several mm, and is held between the DBR layers 22, 23. Specifically, the DBR layer 22 is formed on the front side 24a of the filter region 24, while the DBR layer 23 is formed on the back side 24b of the filter region 24. The back side 24b of the filter region 24 is substantially parallel to a plane perpendicular to the light incident direction (the direction in which the light-transmitting substrate 3 and the light-detecting substrate 4 face each other), while the front side 24a of the filter region 24 is inclined with respect to this plane. As a consequence, the filter region 24 gradually increases its thickness on the order of 100 nm to several µm toward a longitudinal end of the spectroscopic sensor 1.

[0019] The surrounding region 25 is formed in a rectangular annular shape, each outer side of which has a length on the order of several mm, and surrounds the filter region 24 with a predetermined distance d therefrom (e.g., on the order of several µm to 1 mm). The connecting region 26 is formed in a rectangular annular shape to be disposed between the filter region 24 and the surrounding region 25, and connects an end portion 24e of the filter region 24 on the light-detecting substrate 4 side and an end portion 25e of the surrounding region 25 on the light-detecting substrate 4 side. The filter region 24, surrounding region 25, and connecting region 26 form a groove G extending to surround the filter region 24 with a width d in the cavity layer 21.

[0020] How Fig. 1, the front side (end side on the light-transmitting substrate side) 25a of the surrounding region 25 has substantially the same height as a portion 24h located closest to the light-transmitting substrate 3 in the front side (first mirror layer forming surface) 24a of the filter region 24, or is positioned closer to the light-transmitting substrate 3 than this portion 24h. The front side (end side on the light-transmitting substrate side) 26a of the connecting portion 26 has substantially the same height as a portion 241 located closest to the light-detecting substrate 4 in the front side 24a of the filter region 24, or is positioned closer to the light-detecting substrate 4 than this portion 241.On the other hand, the back surface 24b of the filter region 24, the back surface 25b of the surrounding portion 25, and the back surface 26b of the connecting portion 26 are substantially flush with each other. A side surface 25c of the surrounding portion 25 is flush with a side surface 3c of the light-transmitting substrate 3 and a side surface 4c of the light-detecting substrate 4. However, a gap on the order of 0 to 100 µm may occur between the side surface 3c of the light-transmitting substrate 3 and the side surface 4c of the light-detecting substrate 4.

[0021] The light-transmitting substrate 3 is disposed on the DBR layer 22 side of the cavity layer 21 and is connected to the cavity layer 21 and DBR layer 22 via a coupling layer (first coupling layer) 11. The light-detecting substrate 4 is disposed on the DBR layer 23 side of the cavity layer 21 and is connected to the cavity layer 21 and DBR layer 23 via a coupling layer (second coupling layer) 12. Each of the coupling layers 11, 12 disposed between the interference filter unit 20 and the light-transmitting substrate 3 and the light-detecting substrate 4 is a silicon oxide film formed by a film-forming process using TEOS (Tetraethyl Orthosilicate, Tetraethoxysilane) as a material gas, and has a thickness on the order of several hundred nm to 10 µm.

[0022] In the spectroscopic sensor 1 thus configured, when light incident on the light-transmitting substrate 3 from the respective front side 3a passes through the substrate to reach the respective rear side 3b, only light in a predetermined wavelength range intended to be incident on the interference filter unit 20 is transmitted through the optical filter layer 5. Then, when the light transmitted through the optical filter layer 5 is incident on the interference filter unit 20, light in a predetermined wavelength range is selectively transmitted according to its incident position. That is, a wavelength of light entering each channel of the light-receiving unit 6 of the light-detecting substrate 4 is uniquely determined by the thickness and type of the DBR layers 22, 23 and the thickness of the cavity layer 21 at the incident position.As a consequence, light with a different wavelength is detected for each channel of the light receiving unit 6 in the light-detecting substrate 4.

[0023] In the spectroscopic sensor 1, as explained above, the cavity layer 21 is a silicon oxide film and can therefore stabilize its shape, light transmittance, refractive index, and the like more than if it were made of a resin material. The coupling layers 11, 12 are silicon oxide films and can therefore stabilize the transmittance characteristics of the light propagating from the light-transmitting substrate 3 to the interference filter unit 20 and that of the light propagating from the interference filter unit 20 to the light-detecting substrate 4 more than if they were made of a resin material. The fact that the cavity layer 21 and the coupling layers 11, 12 are silicon oxide films can also prevent their quality from deteriorating due to changes in temperature, high humidity, and the like in the environment in which they are used.In particular, the cavity layer 21 and the coupling layers 11, 12 can prevent moisture absorption, which can occur when they are made of resin materials, while suppressing thermal expansion and contraction to a greater extent, making them even more thermally stable than when they are made of resin materials. The spectroscopic sensor 1 therefore becomes extremely reliable.

[0024] The cavity layer 21 is a silicon oxide film formed by thermally oxidizing silicon. This results in a stable cavity layer 21 with high quality and low cost.

[0025] The coupling layers 11, 12 are silicon oxide films formed by a film-forming process using TEOS as a material gas. This allows the coupling layers 11, 12 to be formed at a low temperature and high speed with low stress, preventing damage to the cavity layer 21 and the DBR layers 22, 23, thereby obtaining high-quality cavity layers 21 and the DBR layers 22, 23.

[0026] The optical filter layer 5 is formed on the light-transmitting substrate 3 to oppose the DBR layer 22. This allows light of a predetermined wavelength to efficiently enter the interference filter unit 20.

[0027] In the spectroscopic sensor 11, the filter region 24 is further surrounded by the surrounding region 25 with a predetermined distance d therebetween in the cavity layer 21, while the end portion 24e of the filter region 24 and the end portion 25e of the surrounding region 25 are connected to each other by the connecting region 26. As a consequence, any external force acting in a direction perpendicular to the direction in which the light-transmitting substrate 3 and the light-detecting substrate 4 are opposed to each other is buffered by the surrounding region 25 and the connecting region 26, thereby preventing the filter region 24 from being damaged.

[0028] The front side 25a of the surrounding region 25 has substantially the same height as the portion 24h located closest to the light-transmitting substrate 3 in the front side 24a of the filter region 24, or closer to the light-transmitting substrate 3 than this portion 24h. As a consequence, any external force acting in a direction parallel to the direction in which the light-transmitting substrate 3 and the light-detecting substrate 4 face each other (e.g., an external force applied after direct bonding between coupling layers 11a, 11b or 12a, 12b, which will be explained later) can be absorbed by the surrounding layer 25 to prevent damage to the filter region 24.

[0029] The front surface 26a of the connecting portion 26 has substantially the same height as the portion 241 located closest to the light-detecting substrate 4 in the front surface 24a of the filter portion 24, or positioned closer to the light-detecting substrate 4 than this portion 241. As a consequence, any external force acting in a direction perpendicular to the direction in which the light-transmitting substrate 3 and the light-detecting substrate 4 face each other can be prevented from being directly applied to the front surface 24a of the filter portion 24, which is a surface for forming the DBR layer 22.

[0030] A method for manufacturing the above-mentioned spectroscopic sensor 1 will be explained below. First, how Fig. 3, one main side 50a of a silicon substrate 50 and the other main side 50b thereof are thermally oxidized to form silicon oxide films 52 on one main side 51a of a support substrate 51 made of silicon and the other main side 51b thereof. The silicon oxide film 52 formed on one main side 51a or the other main side 51b of the support substrate 51 is used as a surface layer 53. The silicon oxide film 52 formed on one main side 51a of the support substrate 51 is used as the surface layer 53. The surface layer 53 has a thickness of approximately 1000 nm.

[0031] As the Fig. 4 and Fig. 5, a photoresist layer 54 for etching to form a plurality of cavity layers 21 arranged in a matrix is ​​then formed on the surface layer 53. Using the photoresist layer 54 as a mask, the surface layer 53 provided on the support substrate 51 is then etched (etched back) to form a plurality of cavity layers 21 arranged in a matrix (first step).

[0032] Next, how Fig. 6, the DBR layer 22 is formed on the cavity layer 21 for each section corresponding to a spectroscopic sensor 1 (second step). To form the DBR layer 22, film formation is performed by ion plating, evaporation, sputtering, or the like, and patterning is performed by photoetching and lift-off or etching. Since a spectroscopic sensor 1 is provided here with a cavity layer 21, when the DBR layer 22 is formed, film formation can be performed on the entire surface to cover all the cavity layers 21, instead of patterning each section corresponding to a spectroscopic sensor 1. Subsequently, as Fig. 7, a silicon oxide film is formed on the cavity film 21 to cover the DBR layer 22 by a film-forming process using TEOS as a material gas, and its surface is smoothed by CMP (Chemical Mechanical Polishing), thereby forming the coupling layer 11a.

[0033] The film-forming process using TEOS as a material gas enables film formation at low temperatures (e.g., at a film-forming temperature of 200°C or lower) and at high speeds with low voltage by plasma CVD, LP-CVD, AP-CVD, or the like. In plasma CVD, TEOS is provided by bubbling with a He gas, heating with a heater, or the like, and causes a plasma-assisted degradation reaction to occur in a chamber to react with an O2 gas, thereby forming the silicon oxide film.

[0034] On the other hand, as in Fig. As shown in Fig. 8, a light-transmitting wafer 30 having a plurality of light-transmitting substrates 3 arranged in a matrix is ​​prepared, and the optical filter layer 5 is formed for each portion corresponding to the light-transmitting substrate 3 on the light-transmitting wafer 30 (i.e., on the light-transmitting substrate 3). When the optical filter layer 5 is formed from a dielectric multilayer film, film formation is performed by ion plating, evaporation, sputtering, or the like, and patterning is performed by photoetching and lift-off or etching. When the formation is performed from an organic color filter, the optical filter layer 5 is patterned by exposure and development or the like such as with a photoresist.Since a spectroscopic sensor 1 is provided here with an optical filter layer 5, when the optical filter layer 5 is formed, film formation can be performed on the entire surface to cover the entire light-transmitting wafer 30, instead of patterning each element corresponding to a spectroscopic sensor 1. Then, as . Fig. 9, a silicon oxide film is formed on the light-transmitting wafer 30 to cover the optical filter layer 5 by a film-forming process using TEOS as a material gas, and its surface is smoothed by CMP, thereby forming the coupling layer 11b.

[0035] Next, how the Fig. 10 and Fig. 11, causes the DBR layer 22 and the optical filter layer 5 to oppose each other for each section corresponding to a spectroscopic sensor 1, and the respective surfaces of the coupling layers 11a, 11b are directly bonded to each other (e.g., by surface-activated bonding), thereby bonding the support substrate 51 to the light-transmitting wafer 30. That is, the light-transmitting substrate 3 is bonded to the DBR layer 22 so that the DBR layer 22 and the optical filter layer 5 oppose each other via the coupling layer 11. If the optical filter layer 5 is not formed on the light-transmitting wafer 30, the coupling layer 11b as a smoothing layer is not required.

[0036] How Fig. 12, the silicon oxide film 52 formed on the other main side 51b of the support substrate 51 and a part of the support substrate 51 on the other main side 51b are then ground, so that the support substrate 51 becomes thinner. As Fig. 13, the support substrate 51 is then wet- or dry-etched to remove the support substrate 51 from the cavity layer 21 (fourth step). The silicon oxide film 52 formed on the other main surface 51b of the support substrate 51 and the support substrate 51 can be removed by wet- or dry-etching without grinding.

[0037] How Fig. Next, as shown in Figure 14, the DBR layer 23 is formed in the same manner as the DBR layer 22 on the cavity layer 21 exposed by removing the support substrate 51 (fifth step). As a result, the DBR layers 22, 23 are opposed to each other via the cavity layer 21 for each section corresponding to a spectroscopic sensor 1, thereby forming the interference filter unit 20. A section corresponding to a spectroscopic sensor 1 then becomes a spectroscopic filter substrate 9, producing a spectroscopic filter wafer 90 having a plurality of spectroscopic filter substrates 9 arranged in a matrix.Since a spectroscopic sensor 1 is provided here with a cavity layer 21, when the DBR layer 23 is formed, film formation can be performed on the entire surface to cover all the cavity layers 21, instead of patterning each portion corresponding to a spectroscopic sensor 1.

[0038] Afterwards, as Fig. 15, a silicon oxide film is formed on the cavity layer 21 to cover the DBR layer 23 by a film-forming process using TEOS as a material gas, and its surface is smoothed by CMP, thereby forming the coupling layer 12a. On the other hand, as Fig. 16, a light-detecting wafer 40 is prepared with a plurality of light-detecting substrates 4. A silicon oxide film is then formed on the light-detecting wafer 40 to cover the light-receiving units 6 by a film-forming process using TEOS as a material gas, and its surface is smoothed by CMP, thereby forming the coupling layer 12b.

[0039] As the Fig. 16 and Fig. 17, the DBR layer 23 and the light receiving unit 6 are subsequently caused to oppose each other for each section corresponding to a spectroscopic sensor 1, and the respective surfaces of the coupling layers 12a, 12b are directly bonded to each other, thereby bonding the spectroscopic filter wafer 90 and the light detecting wafer 40 (sixth step). That is, the light detecting substrate 4 is bonded onto the DBR layer 23 so that the DBR layer 23 and the light receiving unit 6 oppose each other through the coupling layer 12.

[0040] How Fig. 18, the back surface of the light-detecting wafer 40 is then ground, polished, etched, etc., so that the light-detecting wafer 40 is thinned to a thickness on the order of 10 to 150 µm. A through-hole is then formed by etching in a portion corresponding to a front wiring, and through-wiring, back wiring, and the like are formed to create the terminal 7 for each portion corresponding to a spectroscopic sensor 1. The bump 8 is formed on the back side of the light-detecting wafer 40, for each section corresponding to a spectroscopic sensor 1. The spectroscopic filter wafer 90 and the light-detecting wafer 40, which are bonded together, are finally divided into each section corresponding to a spectroscopic sensor 1 to produce a plurality of spectroscopic sensors 1.Block elements such as the front wiring and back wiring constituting the terminals or wires 7 may not only be embedded in the front and back surfaces of the light-detecting wafer 40 (ie, the light-detecting substrate 4), but may also be arranged thereon, for example, so as to protrude therefrom by their thickness.

[0041] As explained above, the method for manufacturing the spectroscopic sensor 1 forms the cavity layer 21 by etching the surface layer 53 disposed on the support substrate 51. By forming the cavity layer 21 by etching with the support substrate 51 in this way, the cavity layer 21 can be stably formed with high accuracy. After forming the cavity layer 21 and the DBR layers 22, 23 on the light-transmitting substrate 3 side, the light-detecting substrate 4 is bonded thereto. This can prevent the light-detecting substrate from being damaged in the process of forming the cavity layer 21 and the DBR layers 22, 23. This method for manufacturing the spectroscopic sensor 1 can thus produce a highly reliable spectroscopic sensor 1.

[0042] Since the spectroscopic filter wafer 90 and the light-detecting wafer 40 are bonded together after the performance of each spectroscopic filter substrate 9 in the spectroscopic filter wafer 90 is checked, the light-detecting wafer 40 can be prevented from being wasted due to a malfunction on the spectroscopic filter wafer 90 side.

[0043] Since the silicon oxide film 52 formed on a main surface 51a of the support substrate 51 made of silicon is used as the surface layer 53, the cavity layer 21 can be stably obtained at low cost and with high quality. Furthermore, since both main surfaces 50a, 50b of the silicon substrate 50 are thermally oxidized to form the silicon oxide films 52 on both main surfaces of the support substrate 51 made of silicon, warping is suppressed. The cavity layer 21 can thus be stably obtained with high precision.

[0044] The optical filter layer 5 is formed on the light-transmitting substrate 3, and the light-transmitting substrate 3 is then bonded to the DBR layer 22 such that the DBR layer 22 and the optical filter layer 5 are opposite each other. This allows light in a predetermined wavelength range to be efficiently incident on the interference filter unit 20.

[0045] When etching the surface layer 53 disposed on the support substrate 51 while using the resist layer 54 as a mask, a portion corresponding to the groove G in the resist layer 54 is removed in advance, so that a portion corresponding to the groove G in the surface layer 53 is exposed first. When the portion corresponding to the groove G in the surface layer 53 is exposed, oxygen is released from the surface layer 53, which is made of SiO2, to act as an etchant for the photoresist layer 54. Here, the portion corresponding to the groove G in the surface layer 53 surrounds the portion corresponding to the filter region 24 in the surface layer 53. Therefore, the entire portion corresponding to the filter region 24 in the surface layer 53 is stably supplied with oxygen, and as a result, is reliably etched.

[0046] Without such oxygen supply, the etchant density distribution is likely to be shifted due to a charge effect and the like (for example, the etchant is provided more or less in the peripheral or central portions of the support substrate 51), so the shape of the filter region 24 formed by etching may vary depending on positions in the support substrate 51. In particular, when the resist layer 54 is made of an organic material, the etching rate varies greatly depending on the state of oxygen supply as the etchant, making the above-mentioned oxygen supply very important.

[0047] When the spectroscopic filter wafer 90 and the light-detecting wafer 40 bonded to each other in each section corresponding to a spectroscopic sensor 1 are separated, the occurrence of fragmentation can be prevented because the spectroscopic filter wafer 90 and the light-detecting wafer 40 are firmly integrated with each other as a whole by direct bonding between the coupling layers 11a, 11b and between the coupling layers 12a, 12b.

[0048] The relationship between the photoresist layer 54 and the cavity layer 21 is explained below. Fig. 19, the photoresist layer 54 is on a flat surface (see a solid line in Fig. 19) of the cavity layer 21 before etching (i.e., the surface layer 53). The photoresist layer 54 has a three-dimensional shape corresponding to the shape of the cavity layer 21 to be formed (i.e., the cavity layer 21 after etching). Such a photoresist layer 54 can be formed using a photomask whose optical transmittance is adjusted according to positions, by photolithography or EB lithography whose dose amount is adjusted according to positions, as well as nano-imprinting and the like.

[0049] When etching back (ie, etching the entire surface) is performed based on the shape of the photoresist layer 54, the etching rate for the photoresist layer 54 and the cavity layer 21 can be adjusted depending on the etching conditions. This can produce different shapes of cavity layers 21 from the photoresist layer 54, which has a type of shape. In the Fig. 19, the etching rate for the photoresist layer 54 is approximately twice as fast as that for the cavity layer 21, so that the slope of the surface of the cavity layer 21 after etching (see dashed-dotted line in Fig. 19) is weaker or gentler than that of the surface of the photoresist layer 54 (see a dashed line in Fig. 19).

[0050] A monitoring pattern arranged on the carrier substrate 51 will be explained below. While the surface layer 53 is formed by a substantially constant thickness on the carrier substrate 51, as Fig. 4, not only the photoresist layer 54 for forming a plurality of cavity layers 21 by etching, but also photoresist layers 55 as a monitoring pattern are formed on the surface layer 53, as Fig. 20. The photoresist layers 54, 55 are integrally formed by using the photomask, photolithography or EB lithography, nano-imprinting and the like as explained above.

[0051] The photoresist layers 55 as a monitor pattern are grouped by a multiple number (9 here), and the resulting groups are arranged at a plurality of locations (four peripheral locations and one central location here) on the support substrate 51. Each of the grouped photoresist layers 55 is formed by a substantially constant thickness corresponding to its corresponding one of a plurality of portions of a photoresist layer 54. The grouped photoresist layers 55 include, for example, the thickness of a predetermined portion of the photoresist layer 54 corresponding to a predetermined portion of the filter region 24, the thickness of a predetermined portion of the photoresist layer 54 corresponding to a predetermined portion of the surrounding region 25, and the thickness of a predetermined portion of the photoresist layer 54 corresponding to a predetermined portion of the connecting region 26 (i.e., the bottom surface of the groove G).

[0052] As a consequence, measuring the thickness of the surface layer 53 in a portion from which the photoresist layer 55 has been removed as a monitoring pattern with an optical thickness gauge at a predetermined time, such as in the middle of etching the surface layer 53 or after its completion, can detect the thickness of a predetermined portion of the cavity layer 21 corresponding thereto. When the measurement time is in the middle of etching the surface layer 53, with the photoresist layer 54 remaining in a predetermined portion of the cavity layer 21, the thickness of the photoresist layer 54 remaining in that portion can be detected by the same method.

[0053] Such use of the photoresist layer 55 as a monitoring pattern is therefore very effective because each cavity layer 21 is small, while the surface 24a of the filter region 24 is inclined, making it difficult to directly measure the thickness of the cavity layer 21 with an optical thickness gauge. Furthermore, since the photoresist layers 55 are arranged as a monitoring pattern at a plurality of locations on the support substrate 51, it is possible to evaluate how the etching progresses in the entire surface layer 53 of the support substrate 51 (progress distribution).

[0054] The thickness of the cavity layer 21 corresponding to a predetermined portion of the filter region 24 can also be detected in the following manner. That is, the difference in level between the surface of the cavity layer 21 corresponding to the predetermined portion of the filter region 24 and the bottom surface of the notch G is measured by an AFM (Atomic Force Microscope), a probe-type stepper motor, or the like at a predetermined time, such as in the middle of etching the surface layer 53 or after its completion. On the other hand, in a portion from which the photoresist layer 55 has been removed as a monitoring pattern, corresponding to the bottom surface of the notch G, the thickness of the surface layer 53 is measured by an optical thickness gauge.The level between the surface of the cavity layer 21 and the bottom of the notch G is then added to the measured thickness of the surface layer 53 to calculate the thickness of the cavity layer 21 corresponding to the predetermined portion of the filter region 24. When the measurement time is in the middle of etching the surface layer 53, with the photoresist layer 54 remaining in a portion corresponding to the predetermined portion of the cavity layer 21, the thickness of the photoresist layer 54 remaining in this portion can be detected by the same method.

[0055] While one embodiment of the present invention has been explained above, the present invention is not limited thereto. For example, various materials and shapes can be used for the constituent elements of the spectroscopic sensor without being limited by those mentioned above.

[0056] The spectroscopic sensor may comprise a plurality of interference filter units for selectively transmitting light in a predetermined wavelength range according to a respective incident position. A spectroscopic sensor having a plurality of interference filter units is explained below. How Fig. 21, this spectroscopic sensor 1 comprises a plurality of interference filter units 20A, 20B. The interference filter units 20A, 20B are arranged in a longitudinal row of the spectroscopic sensor 1 between the light-transmitting substrate 3 and the light-detecting substrate 4.

[0057] In the cavity layer 21, as the Fig. 21 and Fig.22, filter regions 24 formed for the respective interference filter units 20A, 20B are juxtaposed, while each filter region 24 is held between DBR layers 22, 23. A surrounding region 25 surrounds the juxtaposed filter regions 24, 24 at a predetermined distance d therefrom, as viewed in the light incident direction. A connecting region 26 connects an end portion on the light-detecting substrate 4 side of the juxtaposed filter regions 24, 24 and an end portion on the light-detecting substrate 4 side of the surrounding region 25 to each other.

[0058] The respective DBR layers 22 for the interference filter units 20A, 20B differ from each other in type, and their boundaries may partially overlap with each other, may be in contact with each other without a gap therebetween, or may be separated from each other by a distance of, for example, approximately 5 µm. Examples of two DBR layers that differ from each other in type are films made of different materials and (single-layer or multi-layer) films made of the same material with different thicknesses. The respective optical filter layers 5 for the interference filter units 20A, 20B differ from each other in type, and their boundaries may partially overlap with each other, may be in contact with each other without a gap therebetween, or may be separated from each other by a distance of, for example, 5 µm.

[0059] In the spectroscopic sensor 1 thus configured, when light incident on the light-transmitting substrate 3 from the front side 3a thereof passes through the light-transmitting substrate 3 and reaches the rear side 3b thereof, only light in a predetermined wavelength range incident on the interference filter units 20A, 20B is transmitted through the optical filter layer 5. When the light transmitted through the optical filter layer 5 is incident on one of the interference filter units 20A, 20B, light in a predetermined wavelength range selectively passes therethrough according to its incident position. That is, a wavelength of light entering each channel of the light-receiving unit 6 of the light-detecting substrate 4 is uniquely determined by the thicknesses and types of the DBR layers 22, 23 and the thickness of the cavity layer 21 at the incident position.As a consequence, light with a different wavelength is detected for each channel of the light receiving unit 6 in the light-detecting substrate 4.

[0060] Colored glass or filter glass that transmits light within a predetermined wavelength range can also be used as the material for the light-transmitting substrate 3. Another optical filter layer can be formed on the front surface 3a of the light-transmitting substrate 3, in addition to or instead of the optical filter layer 5. The light-detecting substrate 4 is not limited to the one-dimensional sensor but can be a two-dimensional sensor. The thickness of the cavity layer 21 can be two-dimensional or stepwise. A reflective single-layer metal film made of Al, Au, Ag, or the like can be used as a mirror layer instead of the DBR layers 22, 23. The spectroscopic sensor can also be formed as an SMD (Surface Mount Device) instead of a CSP.

[0061] Any optical resin such as epoxy, silicone and acrylic, dielectrics such as TiO2, Ta2O5, Nb2O5, Al2O3 and MgF2, and semiconductors such as Si and Ge can also be used as a material for the cavity layer 21 (ie, a material for the surface layer 53 to be etched).

[0062] The coupling layers 11, 12 may also be silicon oxide films formed by plasma CVD using a silane gas, coating-type SOG (Spin On Glass), evaporation, sputtering, or the like. Bonding through an optical resin layer or at an outer edge portion of the spectroscopic sensor 1 may be employed instead of bonding through the coupling layers 11, 12 (i.e., direct bonding). Bonding through the optical resin layer may use any optical resin, such as organic materials based on epoxy, acrylic, and silicone, and hybrid materials composed of organic and inorganic substances, as a material for the optical resin layer. Bonding at the outer edge portion of the spectroscopic sensor 1 may be achieved by low-melting-point glass, solder, or the like, while maintaining a gap with a spacer.In this case, the area surrounding the connection can remain as an air gap or be filled with an optical resin.

[0063] A silicon oxide film can be formed on a main surface of the silicon support substrate by a film-forming process using TEOS as a material gas, by plasma CVD using a silane gas, by coating-type SOG, evaporation, sputtering, LP-CVD, or the like, and used as a surface layer. Silicon oxide films can be formed on both main surfaces of the silicon support substrate by LP-CVD instead of thermal oxidation, and the silicon oxide film formed on one of the main surfaces of the support substrate can be used as a surface layer. That is, the cavity layer, i.e., the silicon oxide film, is not limited to being formed by thermally oxidizing silicon.However, forming the silicon oxide film by thermal oxidation has an advantage in that the cavity layer becomes a denser film, has better uniformity in thickness, suffers from a smaller number of impurities, and has more stable optical properties such as optical transmittance and refractive index, compared with the case when they are formed by the above-mentioned other methods. Industrial applicability

[0064] The present invention can provide a highly reliable spectroscopic sensor. List of reference symbols

[0065] 1: spectroscopic sensor; 3: light-transmitting substrate; 4: light-detecting substrate; 5: optical filter layer; 20, 20A, 20B: interference filter unit; 21: cavity layer; 22: DBR layer (first mirror layer); 23: DBR layer (second mirror layer); 50: silicon substrate; 50a: one main side; 50b: other main side; 51: support substrate; 51a: one main side; 51b: other main side; 52: silicon oxide film; 53: surface layer

Claims

[1] A manufacturing method of a spectroscopic sensor (1) comprising an interference filter unit (20, 20A, 20B) having a cavity layer (21) and first and second mirror layers (22, 23) facing each other across the cavity layer (21); for selectively transmitting light in a predetermined wavelength range according to a respective incident position; and a light-transmitting substrate (3) for transmitting light incident on the interference filter unit (20, 20A, 20B); and a light-detecting substrate (4) for detecting the light transmitted through the interference filter unit (20, 20A, 20B); the method comprising: Forming a silicon oxide film (52) by thermal oxidation on one of main sides (51a, 51b) of the support substrate (51) made of silicon, the silicon oxide film (52) being used as a surface layer (53); Forming a cavity layer (21) by etching the surface layer (53) arranged on a carrier substrate (51); Forming a first mirror layer (22) on the cavity layer (21) after forming the cavity layer (21); Bonding the light-transmitting substrate (3) to the first mirror layer (22) after forming the first mirror layer (22); Removing the carrier substrate (51) from the cavity layer (21) after bonding the light-transmitting substrate (3); Forming the second mirror layer (23) on the cavity layer (21) which is free from the carrier substrate (51) after removing the carrier substrate (51); and Bonding the light-detecting substrate (4) to the second mirror layer (23) after forming the second mirror layer (23). [2] A manufacturing method of a spectroscopic sensor (1) according to claim 1, wherein, before forming the cavity layer (21), both main surfaces (51a, 51b) of a silicon substrate (50) are thermally oxidized to form silicon oxide films (51, 52) on both main surfaces (51a, 51b) of the silicon support substrate (51), and the silicon oxide film (52) formed on one of the main surfaces (51a, 51b) of the support substrate (51) is used as the surface layer (53). [3] A manufacturing method of a spectroscopic sensor (1) according to any one of claims 1 to 2, wherein an optical filter layer (5) for transmitting light in the predetermined wavelength range is formed on the light-transmitting substrate (3) before bonding the light-transmitting substrate (3); and wherein, in bonding the light-transmitting substrate (3), the light-transmitting substrate (3) is bonded to the first mirror layer (22) such that the first mirror layer (23) and the optical filter layer (5) are opposite to each other.

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