JP2006173330A - Light receiving element and its manufacturing method, optical module, and optical transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light receiving element easy in integration, and its manufacturing method. <P>SOLUTION: The light receiving element 100 comprises a substrate 101, a plurality of light receiving units 110, 150 superposed sequentially on the substrate 101, a separating layer 130 for separating electrically respective plurality of photo detectors 110, 150, and an optical member 170 formed above the uppermost photo detector unit 150 between the plurality of photo detectors 110, 150. Respective light receiving units 110, 150 comprise contact layers 112, 152, light absorption layers 114, 154 formed above the contact layers 112, 152, and the other contact layers 116, 156 formed above the light absorption layers 114, 154. The optical member 170 focuses the focuses of a plurality of lights λ1, λ2, having different wavelengths, at the inside of at least two layers of light absorption layers 114, 154 between respective light absorption layers 114, 154. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light receiving element, a method for manufacturing the same, an optical module, and an optical transmission device.

  An optical element used for wavelength division multiplexing (WDM) optical communication performs wavelength division using, for example, an optical waveguide (see, for example, JP-A-2001-57440). In this case, since an optical waveguide is used, integration may be difficult.

For example, in Japanese Patent Laid-Open No. 2000-252511, two photodiodes having different absorption wavelengths are individually manufactured, bonded and stacked using solder or the like (mounting process), and wavelength division is performed by upper and lower photodiodes. Technology is disclosed. In this case, for example, there may be a problem in the reproducibility of the mounting process and the reliability of the device after the mounting process.
JP 2001-57440 A JP 2000-252511 A

  An object of the present invention is to provide a light-receiving element that can be easily integrated and a method for manufacturing the same. Another object of the present invention is to provide an optical module including the light receiving element, and an optical transmission device having the optical module.

The light receiving element according to the present invention is:
A substrate,
Above the substrate, a plurality of light receiving units stacked in order,
A separation layer for electrically separating each of the plurality of light receiving parts;
An optical member formed above an uppermost light receiving part among the plurality of light receiving parts,
Each of the light receiving parts
A contact layer;
A light absorbing layer formed above the contact layer;
And another contact layer formed above the light absorption layer,
The optical member focuses a plurality of lights having different wavelengths within the light absorbing layers of at least two of the light absorbing layers.

  According to this light receiving element, since the plurality of light receiving portions are sequentially stacked via the separation layer, the device can be miniaturized. As a result, the light receiving elements can be easily integrated.

  In the present invention, other specific objects (hereinafter referred to as “B”) formed above a specific object (hereinafter referred to as “A”) are defined as B directly formed on A and A And B formed via the others on A. Further, in the present invention, forming B above A includes a case where B is formed directly on A and a case where B is formed on A via another on A.

In the light receiving element according to the present invention,
The optical member can adjust the same number of light focal points as the number of the light receiving portions to the inside of each light absorbing layer.

In the light receiving element according to the present invention,
At least two of the light absorbing layers may be made of the same material.

The light receiving element according to the present invention is:
A substrate,
A first light receiving portion, which is disposed from the substrate side above the substrate and includes a first contact layer, a first light absorption layer, and a second contact layer;
A separation layer formed above the second contact layer;
A second light-receiving portion disposed above the separation layer from the separation layer side and including a third contact layer, a second light absorption layer, and a fourth contact layer;
An optical member formed above the fourth contact layer,
The optical member focuses the light of the first wavelength in the first light absorption layer, and focuses the light of the second wavelength in the second light absorption layer.

In the light receiving element according to the present invention,
The first light absorption layer and the second light absorption layer may be made of the same material.

In the light receiving element according to the present invention,
The optical member may have a plurality of lens portions stacked integrally.

In the light receiving element according to the present invention,
The center of each lens part in plan view can be the same as or substantially the same as the center of the light incident on the optical member.

In the light receiving element according to the present invention,
At least two lens portions of the plurality of lens portions may have different refractive indexes.

In the light receiving element according to the present invention,
Outer edges of at least two of the plurality of lens units may have different radii of curvature.

An optoelectronic integrated device according to the present invention includes the above-described light receiving device,
TIA (Trans-Impedance Amplifier).

An optical module according to the present invention includes the above-described light receiving element,
A light emitting element.

  The light transmission device according to the present invention includes the above-described optical module.

The manufacturing method of the light receiving element according to the present invention is as follows:
A step of sequentially stacking and forming a plurality of light receiving portions above the substrate;
Forming a separation layer for electrically separating each of the plurality of light receiving parts;
Forming an optical member above an uppermost light receiving part among the plurality of light receiving parts,
The step of forming each of the light receiving portions includes:
Forming a contact layer;
Forming a light absorption layer above the contact layer;
Forming another contact layer above the light absorbing layer,
The optical member is formed so that a plurality of lights having different wavelengths are focused on at least two of the light absorption layers of the light absorption layers.

  According to this method for manufacturing a light receiving element, it is possible to manufacture the light receiving element with good reproducibility and provide a light receiving element with good reliability.

The manufacturing method of the light receiving element according to the present invention is as follows:
A semiconductor layer for forming at least a first contact layer, a first light absorption layer, a second contact layer, a separation layer, a third contact layer, a second light absorption layer, and a fourth contact layer above the substrate Sequentially stacking layers to form a semiconductor multilayer film,
Forming a first contact layer, a first light absorption layer, a second contact layer, a separation layer, a third contact layer, a second light absorption layer, and a fourth contact layer by patterning the semiconductor multilayer film; When,
Forming an optical member above the fourth contact layer,
The optical member is formed so that the first wavelength light is focused in the first light absorption layer, and the second wavelength light is focused in the second light absorption layer.

In the method for manufacturing a light receiving element according to the present invention,
The optical member can be formed by a droplet discharge method for discharging a droplet including the material of the optical member.

In the method for manufacturing a light receiving element according to the present invention,
Before the step of forming the optical member, a step of forming a blocking member for blocking the droplets can be included.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

1. 1. First embodiment 1-1. Structure of Light Receiving Element FIG. 1 is a cross-sectional view schematically showing a light receiving element 100 according to this embodiment. FIG. 2 is a plan view schematically showing the light receiving element 100 shown in FIG. 1 is a view showing a cross section taken along the line II of FIG.

  As shown in FIGS. 1 and 2, the light receiving element 100 according to the present embodiment includes a substrate 101, a first light receiving unit 110, a separation layer 130, a second light receiving unit 150, and an optical member 170. . In the present embodiment, a case where the first light receiving unit 110 and the second light receiving unit 150 function as a pin type photodiode will be described.

  As the substrate 101, for example, a GaAs substrate or an InP substrate can be used.

  The first light receiving unit 110 is provided on the substrate 101. The first light receiving unit 110 includes a first contact layer 112, a first light absorption layer 114, and a second contact layer 116. The first contact layer 112 is provided on the substrate 101, the first light absorption layer 114 is provided on the first contact layer 112, and the second contact layer 116 is provided on the first light absorption layer 114. The first contact layer 112 constitutes a columnar semiconductor deposited body. The planar shape of the first contact layer 112 can be, for example, a quadrangle or a circle. In the example shown in the figure, it is a quadrangle. The first light absorption layer 114 and the second contact layer 116 constitute an integrated columnar semiconductor deposit. The planar shapes of the first light absorption layer 114 and the second contact layer 116 can be, for example, a quadrangle or a circle. In the example shown in the figure, it is a quadrangle.

  When a GaAs substrate is used as the substrate 101, the first contact layer 112 is made of, for example, an n-type GaAs layer, the first light absorption layer 114 is made of, for example, an undoped GaInNAs layer, and the second contact layer 116 is made of, for example, a p-type. It can consist of a GaAs layer. When an InP substrate is used as the substrate 101, for example, the first contact layer 112 is made of, for example, an n-type InGaAs layer, the first light absorption layer 114 is made of, for example, an undoped InGaAs layer, and the second contact layer 116 is made of, for example, It can consist of a p-type InGaAs layer. Accordingly, the p-type second contact layer 116, the undoped first light absorption layer 114, and the n-type first contact layer 112 form a pin structure.

  A first electrode 113 is formed on the first contact layer 112 as shown in FIGS. 1 and 2. The planar shape of the first electrode 113 can be, for example, a quadrangle as in the illustrated example. The first electrode 113 is formed so as not to contact the first light absorption layer 114. A second electrode 117 is formed on the second contact layer 116. The planar shape of the second electrode 117 can be, for example, a quadrangle as in the illustrated example. The second electrode 117 can be formed so as not to contact the separation layer 130. The first electrode 113 and the second electrode 117 are used to drive the first light receiving unit 110.

  The separation layer 130 is provided on the first light receiving unit 110. More specifically, the separation layer 130 is provided on the second contact layer 116. The separation layer 130 constitutes a columnar semiconductor deposited body. The planar shape of the separation layer 130 can be a square or a circle, for example. In the example shown in the figure, it is a quadrangle.

The separation layer 130 electrically separates the first light receiving unit 110 and the second light receiving unit 150. More specifically, the separation layer 130 electrically separates the second contact layer 116 and a third contact layer 152 described later. That is, as the separation layer 130, an insulating or semi-insulating layer can be used. For example, as the separation layer 130, a layer obtained by oxidizing an InAlAs layer, a layer obtained by oxidizing an AlGaAs layer, a layer obtained by oxidizing an InGaAsP layer, an undoped GaAs layer, an undoped InGaAs layer, a SiN layer, a SiO ₂ layer, or the like may be used. it can.

  The second light receiving unit 150 is provided on the separation layer 130. The second light receiving unit 150 includes a third contact layer 152, a second light absorption layer 154, and a fourth contact layer 156. The third contact layer 152 is provided on the separation layer 130, the second light absorption layer 154 is provided on the third contact layer 152, and the fourth contact layer 156 is provided on the second light absorption layer 154. The third contact layer 152 constitutes a columnar semiconductor deposited body. The planar shape of the third contact layer 152 can be, for example, a quadrangle or a circle. In the example shown in the figure, it is a quadrangle. The second light absorption layer 154 and the fourth contact layer 156 constitute an integral columnar semiconductor deposit. The planar shape of the second light absorption layer 154 and the fourth contact layer 156 can be, for example, a quadrangle or a circle. In the illustrated example, it is circular.

  When a GaAs substrate, for example, is used as the substrate 101, the third contact layer 152 is made of, for example, an n-type GaAs layer, the second light absorption layer 154 is made of, for example, an undoped GaInNAs layer, and the fourth contact layer 156 is made of, for example, a p-type. It can consist of a GaAs layer. When an InP substrate, for example, is used as the substrate 101, the third contact layer 152 is made of, for example, an n-type InGaAs layer, the second light absorption layer 154 is made of, for example, an undoped InGaAs layer, and the fourth contact layer 156 is made of, for example, It can consist of a p-type InGaAs layer. Accordingly, the p-type fourth contact layer 156, the undoped second light absorption layer 154, and the n-type third contact layer 152 form a pin structure.

  Note that the first light absorption layer 114 and the second light absorption layer 154 can be made of the same material or different materials. Here, the different materials are compounds including the same constituent elements and include the case where the composition ratios of the respective elements are different. As will be described later, when the light receiving element 100 according to the present embodiment performs wavelength division in a narrow wavelength band, the same material is desirable. Conversely, when performing wavelength division of a wide range of wavelength bands with the light receiving element 100 according to the present embodiment, it is desirable that the materials be different. In addition, the first light absorption layer 114 and the second light absorption layer 154 can suppress the light absorbed by the first light absorption layer 114 from being absorbed by the second light absorption layer 154. The material can be selected.

  A third electrode 153 is formed on the third contact layer 152 as shown in FIGS. 1 and 2. The planar shape of the third electrode 153 can be, for example, a quadrangle as in the illustrated example. The third electrode 153 is formed so as not to contact the second light absorption layer 154. A fourth electrode 157 is formed on the fourth contact layer 156. The planar shape of the fourth electrode 157 can be, for example, a ring shape as illustrated. The fourth electrode 157 is provided with an opening 182, and a part of the upper surface of the fourth contact layer 156 is exposed through the opening 182. This exposed surface is the light incident surface 180 of the second light receiving unit 150. Accordingly, by appropriately setting the planar shape and size of the opening 182, the shape and size of the incident surface 180 can be appropriately set. In the illustrated example, the planar shape of the incident surface 180 is a circle. The third electrode 153 and the fourth electrode 157 are used to drive the second light receiving unit 150.

  A damming member 176 is provided on the fourth electrode 157. The dam member 176 can dam the optical member precursor 170a containing the material of the optical member 170 (see FIGS. 9 and 10). In other words, the shape of the optical member 170 can be controlled by controlling the shape of the blocking member 176. The planar shape of the damming member 176 can be, for example, a ring shape as illustrated. The cross-sectional shape of the damming member 176 can be a square or a triangle, for example. In the illustrated example, it is a rectangle. In the present embodiment, the position of the upper surface of the damming member 176 is 7.2 μm higher than the position of the incident surface 180. Note that the fourth electrode 157 can also be used as a blocking member. That is, the fourth electrode 157 can also dam the optical member precursor 170a.

  The optical member 170 includes a first lens part 172 and a second lens part 174. The first lens portion 172 is formed on a part of the fourth electrode 157 and the incident surface 180. The first lens portion 172 is formed so as to contact the inner side surface of the damming member 176 and not to contact the upper surface of the damming member 176. The second lens unit 174 is stacked on the first lens unit 172. That is, the first lens portion 172 and the second lens portion 174 are integrally formed. The second lens part 174 is formed on the first lens part 172 and the damming member 176. The second lens portion 174 is formed so as not to contact the outer side surface of the blocking member 176.

  The center of the first lens part 172 in plan view and the center of the second lens part 174 in plan view can be formed to be the same or substantially the same as the center of the light incident on the optical member 170.

  The shapes of the first lens portion 172 and the second lens portion 174 can be convex. More specifically, the shape of the first lens portion 172 and the second lens portion 174 can be, for example, a shape obtained by cutting out a part of one sphere as in the illustrated example.

  In the present embodiment, the case where the optical member 170 includes two lens portions (the first lens portion 172 and the second lens portion 174) has been described. However, the number of lens portions constituting the optical member 170 is as follows. It is not particularly limited, and can be one or more. For example, the number of lens parts constituting the optical member 170 is set to 2 or more, and each lens part has a different refractive index (the refractive index is decreased toward the outer side), whereby light can be efficiently refracted. it can.

  In the present embodiment, the case where the light receiving element 100 includes two light receiving units (the first light receiving unit 110 and the second light receiving unit 150) is described. However, the number of light receiving units included in the light receiving element 100 is as follows. If it is two or more, it will not specifically limit. The number of light receiving units included in the light receiving element 100 can be set as appropriate according to the number of light wavelengths divided by the light receiving element 100. The wavelength division performed by the light receiving element 100 will be described later.

  In the present embodiment, the case where the first light receiving unit 110 and the second light receiving unit 150 function as a pin type photodiode has been described. However, the present invention is also applicable to light receiving elements other than the pin type photodiode. Is possible. Note that examples of the light receiving element to which the present invention can be applied include a pn photodiode, an avalanche photodiode, and an MSM photodiode.

1-2. Operation of the light receiving element The operation of the light receiving element 100 of the present embodiment will be described below. The following method for driving the light receiving element 100 is an example, and various modifications can be made without departing from the spirit of the present invention.

  The light receiving element 100 has a function of converting a plurality of optical signals composed of a plurality of lights having different wavelengths into current signals corresponding to the respective optical signals. Specifically, it is as follows.

  First, a plurality of lights having different wavelengths emitted from the outside of the light receiving element 100 are incident on the light receiving element 100. More specifically, for example, first, a plurality of lights having different wavelengths are emitted from a light emitting element (not shown). The plurality of lights enter, for example, one end face of an optical waveguide (not shown), propagate in the optical waveguide, and exit from the other end face. The plurality of emitted light is incident on the second lens portion 174 of the light receiving element 100. Here, for convenience, light of wavelength λ1 (hereinafter referred to as “first wavelength light λ1”) and light of wavelength λ2 (hereinafter referred to as “second wavelength light λ2”) are the second lens unit 174. An example of incidence on the light will be described. A case where the wavelength λ1 is longer than the wavelength λ2 will be described. For example, the wavelength λ1 can be 1.55 μm, and the wavelength λ2 can be 1.31 μm. The paths of the first wavelength light λ1 and the second wavelength light λ2 are schematically indicated by arrows in FIG. For example, the angle θ formed between the first wavelength light λ1 and the second wavelength light λ2 incident on the second lens unit 174 and the horizontal plane may be 83.7 °. Further, for example, the first wavelength light λ1 and the second wavelength light λ2 incident on the second lens unit 174 have a spot radius of 20 μm on the incident surface 180 when the optical member 170 is not present. Aperture light can be used.

  The light λ <b> 1 having the first wavelength and the light λ <b> 2 having the second wavelength are refracted at the interface between the outside (for example, air) of the second lens unit 174 and the second lens unit 174. At this time, the light λ1 having the first wavelength and the light λ2 having the second wavelength have different wavelengths, and thus have different refraction angles. Specifically, the light λ1 having the first wavelength has a larger refraction angle than the light λ2 having the second wavelength. As a result, as shown in FIG. 1, the light λ2 having the second wavelength is more condensed than the light λ1 having the first wavelength.

  Next, the first wavelength light λ <b> 1 and the second wavelength light λ <b> 2 propagated in the second lens unit 174 are incident on the first lens unit 172. The light λ1 having the first wavelength and the light λ2 having the second wavelength are refracted at the interface between the second lens unit 174 and the first lens unit 172. At this time, as in the case of refraction at the interface between the outside of the second lens unit 174 and the second lens unit 174 described above, the light λ1 of the first wavelength has a larger refraction angle than the light λ2 of the second wavelength. . As a result, as shown in FIG. 1, the light λ2 having the second wavelength is more condensed than the light λ1 having the first wavelength.

  As shown in FIG. 1, the optical member 170 (the first lens unit 172 and the second lens unit 174) focuses the light λ2 having the second wavelength more concentrated than the light λ1 having the first wavelength as shown in FIG. In the second light absorption layer 154. As a result, the second wavelength light λ <b> 2 is mainly absorbed by the second light absorption layer 154. Specifically, first, the light λ <b> 2 having the second wavelength propagated through the first lens unit 172 is incident on the second light receiving unit 150 from the incident surface 180. Next, the light λ <b> 2 having the second wavelength passes through the fourth contact layer 156 and is mainly absorbed by the second light absorption layer 154.

  Similarly, the first wavelength light λ1 focused by the optical member 170 is focused in the first light absorption layer 114 as shown in FIG. As a result, the light λ1 having the first wavelength is mainly absorbed by the first light absorption layer 114. Specifically, first, the light λ <b> 1 having the first wavelength propagated through the first lens unit 172 is incident on the second light receiving unit 150 from the incident surface 180. Next, the light λ <b> 1 having the first wavelength propagates through the second light receiving unit 150 and the separation layer 130 and enters the first light receiving unit 110. Next, the light λ <b> 1 having the first wavelength is transmitted through the second contact layer 116 and is mainly absorbed by the first light absorption layer 114.

  As described above, the reason why light is mainly absorbed by the light absorption layer existing at the focal position is as follows.

  For example, as shown in FIG. 3, in a state where the light source 10 is fixed, the photodiode 12 is moved in the direction perpendicular to the light receiving surface 14 (the direction of the arrow M shown in FIG. 3), and the light receiving sensitivity is measured. It was. FIG. 3 is a diagram schematically showing a method for measuring light receiving sensitivity. In FIG. 3, the display of each layer (including each electrode) constituting the photodiode 12 is omitted. As the light source 10, light from a halogen lamp whose wavelength was controlled by a spectroscope was used. Further, the light a emitted from the light source 10 is stopped by the lens 16, and the spot diameter at the focal position is set to 50 μmφ. The diameter of the light receiving surface 14 of the photodiode 12 was 200 μmφ. Therefore, by setting the focal position to the position of the light receiving surface 14, all of the light a emitted from the light source 10 can be incident on the light receiving surface 14 of the photodiode 12. As the photodiode 12, a GaAs type was used. The distance from the light receiving surface 14 to the upper surface of the light absorbing layer was 0.1 μm. The film thickness of the light absorption layer was 3.5 μm.

  FIG. 4 is a diagram illustrating a measurement result of light receiving sensitivity with respect to the position of the light receiving surface 14. As for the light receiving sensitivity, only data of light having a wavelength of 850 nm is extracted. In FIG. 4, the position (focal position) at which the spot diameter is minimum on the light receiving surface 14 is defined as the origin (zero) on the horizontal axis. The negative direction on the horizontal axis is the direction in which the photodiode 12 and the light source 10 move away (−Z direction), and the positive direction on the horizontal axis is the direction in which the photodiode 12 and the light source 10 approach (+ Z direction). As shown in FIG. 4, it can be seen that when the position of the light receiving surface 14 is near the origin, the light receiving sensitivity is maximized. The order of the distance from the light receiving surface 14 to the upper surface of the light absorption layer is about two to three orders of magnitude with respect to the order of the movement distance of the photodiode 12. Therefore, in the result shown in FIG. 4, it can be considered that the position of the light receiving surface 14 is substantially equal to the position of the light absorption layer. That is, the result shown in FIG. 4 indicates that the light receiving sensitivity is maximized when the focal position is adjusted in the light absorption layer. This means that the light is mainly absorbed by the light absorption layer present at the focal position.

  Therefore, in the light receiving element 100 according to the present embodiment, the light λ1 having the first wavelength is mainly absorbed by the first light absorption layer 114. As a result, photoexcitation occurs in the first light absorption layer 114, and electrons and holes are generated. Arise. Then, due to the electric field applied between the first electrode 113 and the second electrode 117, electrons move to the first electrode 113 and holes move to the second electrode 117. As a result, a current (photocurrent) is generated in the direction from the first contact layer 112 to the second contact layer 116 in the first light receiving unit 110. That is, an optical signal composed of the light λ1 having the first wavelength can be converted into a current signal.

  Similarly, the light λ2 having the second wavelength is mainly absorbed by the second light absorption layer 154, and as a result, photoexcitation occurs in the second light absorption layer 154, and electrons and holes are generated. Then, due to the electric field applied between the third electrode 153 and the fourth electrode 157, electrons move to the third electrode 153 and holes move to the fourth electrode 157, respectively. As a result, in the second light receiving unit 150, a current (photocurrent) is generated in the direction from the third contact layer 152 to the fourth contact layer 156. That is, an optical signal composed of the light λ2 having the second wavelength can be converted into a current signal.

  In the present embodiment, for the sake of convenience, an example in which two lights having different wavelengths (light λ1 having the first wavelength and light λ2 having the second wavelength) are incident on the optical member 170 has been described. The number of light beams having different wavelengths incident on is not particularly limited as long as it is two or more. The number of lights having different wavelengths incident on the optical member 170 can be appropriately set according to the usage pattern of the light receiving element 100.

1-3. Next, an example of a method for manufacturing the light receiving element 100 according to the present embodiment will be described with reference to FIGS. 1, 2, and 5 to 10. 5 to 10 are cross-sectional views schematically showing one manufacturing process of the light receiving element 100 shown in FIGS. 1 and 2, and each correspond to the cross-sectional view shown in FIG.

  (1) First, the substrate 101 is prepared. Hereinafter, an example in which an InP substrate is used as the substrate 101 will be described.

Next, the semiconductor multilayer film 120 is formed by epitaxial growth on the surface 101a of the substrate 101 as shown in FIG. Here, the semiconductor multilayer film 120 includes, for example, a first contact layer 112 made of an n-type InGaAs layer, a first light absorption layer 114 made of an undoped InGaAs layer, a second contact layer 116 made of a p-type InGaAs layer, and an InAlAs layer. A layer (hereinafter referred to as “separation layer”) 130a, a third contact layer 152 made of an n-type InGaAs layer, a second light absorption layer 154 made of an undoped InGaAs layer, and a p-type InGaAs layer. A fourth contact layer 156 is formed. By laminating these layers on the substrate 101 in order, the semiconductor multilayer film 120 is formed. The composition of the material of each layer can be determined as appropriate. For example, the composition of the material of the first light absorption layer 114 and the first light absorption layer 114 can be suppressed so that the light absorbed by the first light absorption layer 114 can be suppressed by the second light absorption layer 154. The composition of the material of the two-light absorption layer 154 can be made different. Specifically, for example, the first light absorption layer 114 is made of an In _0.53 Ga _0.47 As layer, and the second light absorption layer 154 is made of an In _0.4 Ga _0.6 As layer. it can. Further, by increasing the Al composition of the InAlAs layer that is the layer 130a serving as the separation layer, the layer 130a serving as the separation layer can be easily oxidized in the subsequent oxidation step (see FIG. 6). In the present invention, the Al composition of the InAlAs layer is the composition of aluminum (Al) with respect to the group III element.

  As described above, the film thickness of each layer constituting the semiconductor multilayer film 120 is such that the first wavelength light λ1 is focused in the first light absorption layer 114, and the second wavelength light λ2 is focused in the second light absorption. The value can be appropriately set so as to fit in the layer 154. Further, the film thickness of each layer constituting the semiconductor multilayer film 120 can be set in consideration of the shift of the focal position due to the optical axis shift. For example, the thickness of each layer constituting the semiconductor multilayer film 120 is such that the thickness of the first contact layer 112 is 0.2 μm, the thickness of the first light absorption layer 114 is 0.3 μm, and the thickness of the second contact layer 116. Is 0.1 μm, the thickness of the separation layer 130 a is 0.2 μm, the thickness of the third contact layer 152 is 0.2 μm, the thickness of the second light absorption layer 154 is 0.3 μm, and the fourth contact layer The film thickness of 156 can be 0.1 μm or the like.

  The temperature at which the epitaxial growth is performed is appropriately determined depending on the growth method, the raw material, the type of the substrate 101, or the type, thickness, and carrier density of the semiconductor multilayer film 120 to be formed, but is generally 450 ° C. to 800 ° C. Is preferred. Further, the time required for performing the epitaxial growth is also appropriately determined in the same manner as the temperature. In addition, as a method for epitaxial growth, a metal-organic vapor phase epitaxy (MOVPE) method, an MBE (Molecular Beam Epitaxy) method, an LPE (Liquid Phase Epitaxy) method, or the like can be used.

  (2) Next, as shown in FIG. 6, the semiconductor multilayer film 120 is patterned to form a first contact layer 112, a first light absorption layer 114, a second contact layer 116, and a layer 130 a serving as a separation layer having a desired shape. The third contact layer 152, the second light absorption layer 154, and the fourth contact layer 156 are formed. Thereby, the 1st light-receiving part 110 and the 2nd light-receiving part 150 are formed. The patterning of the semiconductor multilayer film 120 can be performed by a known lithography technique and etching technique.

  Next, as shown in FIG. 6, for example, in a water vapor atmosphere at about 400 ° C., the substrate 101 on which the first light receiving unit 110 and the second light receiving unit 150 are formed by the above-described process is put into a separation layer. The separation layer 130 is formed by oxidizing the layer 130a from the side surface. The oxidation of the layer 130a serving as the separation layer is performed until the entire layer 130a serving as the separation layer is oxidized.

  Through the above steps, a stacked body of the first light receiving unit 110, the separation layer 130, and the second light receiving unit 150 is formed.

  (3) Next, as shown in FIG. 7, the first electrode 113 is formed on the first contact layer 112, the second electrode 117 is formed on the second contact layer 116, and on the third contact layer 152. A third electrode 153 is formed, and a fourth electrode 157 is formed on the fourth contact layer 156.

These electrodes can be formed using, for example, a known electrode forming technique (for example, a combination of a vacuum deposition method, a lift-off method, and an annealing process). Note that the fourth electrode 157 is formed to have an opening 182. Through the opening 182, a part of the upper surface of the fourth contact layer 156 is exposed. This exposed surface becomes the incident surface 180. As the first electrode 113 and the third electrode 153, for example, a laminated film of an alloy of gold (Au) and zinc (Zn) and gold (Au) can be used. As the second electrode 117 and the fourth electrode 157, for example, an alloy of gold (Au) and germanium (Ge), a stacked film of nickel (Ni), and gold (Au) can be used. In addition, as the first to fourth electrodes 113, 117, 153, and 157, for example, a metal (non-alloy metal) that can form an electrode without performing an annealing process can be used. Examples of non-alloy metal include tungsten silicide (WSi _x ).

  (4) Next, as shown in FIG. 8, a damming member 176 is formed on the fourth electrode 157. As the damming member 176, for example, a resin such as polyimide, a dielectric layer such as SiN, or the like can be used. The damming member 176 can be patterned using, for example, a known lithography technique and etching technique.

  (5) Next, as shown in FIG. 9, a first lens portion precursor 172a is formed. Specifically, a liquid material droplet 172b for forming the first lens part 172 is discharged onto the upper surface of the fourth contact layer 156 to form the first lens part precursor 172a. The droplet 172b is discharged until the first lens portion precursor 172a is formed so that the first lens portion 172 has a desired shape. At this time, the first lens portion precursor 172a is blocked by the inner side surface of the blocking member 176. The liquid material has a property of being curable by applying energy (light, heat, etc.). Examples of the liquid material include an ultraviolet curable resin and a thermosetting resin precursor. Examples of the ultraviolet curable resin include an ultraviolet curable acrylic resin and an epoxy resin. Examples of the thermosetting resin include a thermosetting polymer to which high refractive index metal oxide nanoparticles are added, a thermosetting polyimide resin, and the like.

  Examples of a method for discharging the droplet 172b include a dispenser method and a droplet discharge method. The dispenser method is a general method for discharging droplets, and is effective when the droplets 172b are discharged over a relatively wide area. The droplet discharge method is a method of discharging droplets using an inkjet head 192 for discharging droplets, and the position at which droplets are discharged can be controlled in units of μm. In addition, since the amount of droplets to be discharged can be controlled in units of picoliters, the first lens portion 172 having a fine structure can be manufactured.

  Examples of the droplet discharge method include (i) a method in which pressure is generated by changing the size of bubbles in the liquid by heat and a liquid is discharged from the ink jet nozzle 190, or (ii) a method in which a piezoelectric element is used. There is a method of discharging liquid from the inkjet nozzle 190 by pressure. From the viewpoint of controllability of pressure, the method (ii) is desirable.

  The alignment between the position of the inkjet nozzle 190 of the inkjet head 192 and the ejection position of the droplet 172b is performed using a known image recognition technique used in an exposure process or an inspection process in a general semiconductor integrated circuit manufacturing process. . For example, as shown in FIG. 9, alignment between the position of the inkjet nozzle 190 of the inkjet head 192 and the opening 182 of the fourth electrode 157 is performed by image recognition. After the alignment, the voltage applied to the inkjet head 192 is controlled, and then the droplet 172b is ejected.

  For example, when there is some variation in the discharge angle of the droplet 172b discharged from the inkjet nozzle 190, if the position where the droplet 172b landed is inside the opening 177 of the damming member 176, the damming member 176 The first lens portion precursor 172a spreads out in the region surrounded by, and the position is automatically corrected.

  (6) Next, as shown in FIG. 10, the first lens portion precursor 172 a is cured to form the first lens portion 172. Specifically, energy (light, heat, etc.) is applied to the first lens portion precursor 172a. When the first lens portion precursor 172a is cured, an appropriate method is used depending on the type of material of the first lens portion precursor 172a. Specifically, for example, addition of thermal energy or irradiation with light such as ultraviolet rays or laser light can be given.

  As described above, the structure and material of the first lens portion 172 are such that the first wavelength light λ1 is focused in the first light absorption layer 114, and the second wavelength light λ2 is focused in the second light absorption layer 154. It can be appropriately selected to fit inside. For example, the radius of curvature of the outer edge of the first lens unit 172 may be 25 μm, and the height of the first lens unit 172 from the incident surface 180 may be 32 μm. Further, for example, the material of the first lens portion 172 is a high refractive index metal oxide nanoparticle having a refractive index of 1.98 for the first wavelength light λ1 and a refractive index of 2.00 for the second wavelength light λ2. A thermosetting polymer to which is added can be used.

  Next, as shown in FIG. 10, a second lens portion precursor 174a is formed. Specifically, a liquid material droplet 174b for forming the second lens unit 174 is ejected onto the upper surface of the first lens unit 172 to form the second lens unit precursor 174a. At this time, the second lens portion precursor 174a is dammed by the corner portion 179 constituted by the upper surface of the damming member 176 and the outer side surface. Since the formation of the second lens portion precursor 174a can be performed in the same manner as the formation of the first lens portion precursor 172a described above, detailed description thereof is omitted.

  (7) Next, as shown in FIGS. 1 and 2, the second lens portion precursor 174 a is cured to form the second lens portion 174. Since the curing of the second lens portion precursor 174a can be performed in the same manner as the curing of the first lens portion precursor 172a described above, detailed description thereof is omitted.

  As described above, the structure and material of the second lens portion 174 are such that the first wavelength light λ1 is focused in the first light absorption layer 114, and the second wavelength light λ2 is focused in the second light absorption layer 154. It can be appropriately selected to fit inside. For example, the radius of curvature of the outer edge of the second lens unit 174 may be 40 μm, and the height of the second lens unit 174 from the highest incident surface 180 may be 67 μm. For example, the material of the second lens unit 174 may be an epoxy resin having a refractive index of 1.58 for the first wavelength light λ1 and a refractive index of 1.6 for the second wavelength light λ2. it can. Note that the first lens portion 172 and the second lens portion 174 can be made of the same material or different materials. For example, when the first lens unit 172 and the second lens unit 174 are made of different materials, the light can be refracted more greatly. In this case, the refractive index of the material of the first lens part 172 is preferably larger than the refractive index of the material of the second lens part 174. For example, the refractive index of vinyl acetate is 1.450 to 1.470, the refractive index of epoxy resin is 1.550 to 1.610, the refractive index of phenoxy resin is 1.598, and the refractive index of polyimide is 1.780, the refractive index of the thermosetting polymer to which the high refractive index metal oxide nanoparticles are added is about 2.0 (or more). Accordingly, these materials can be selected as appropriate so that the refractive index of the material of the first lens portion 172 is larger than the refractive index of the material of the second lens portion 174.

  Through the above steps, the light receiving element 100 of the present embodiment is obtained as shown in FIGS.

1-4. Action / Effect According to the light receiving element 100 according to the present embodiment, as described above, a plurality of optical signals composed of a plurality of lights having different wavelengths can be converted into current signals corresponding to the respective optical signals. Then, desired wavelength division can be performed by appropriately selecting at least one of the structure and material of the optical member 170. For example, wavelength division can be performed by converting a plurality of optical signals composed of a plurality of lights having very close wavelengths into current signals corresponding to the respective optical signals. Therefore, wavelength division in a narrow wavelength band can be performed. Of course, wavelength division of a wide range of wavelength bands can also be performed.

  Further, according to the light receiving element 100 according to the present embodiment, the optical member 170 is formed above the incident surface 180, so that an allowable range of optical axis deviation is widened. That is, according to the light receiving element 100 according to the present embodiment, the optical axis tolerance is improved.

  In addition, according to the light receiving element 100 according to the present embodiment, the first light receiving unit 110 and the second light receiving unit 150 are stacked via only the separation layer 130, so that the device can be miniaturized. . As a result, the light receiving element 100 can be easily integrated.

  In addition, according to the method for manufacturing the light receiving element 100 according to the present embodiment, first, on the substrate 101, a layer to be the first light receiving unit 110, a layer to be the separation layer 130, and a layer to be the second light receiving unit 150. Are stacked to form the semiconductor multilayer film 120, and then the semiconductor multilayer film 120 is patterned to form the first light receiving unit 110, the separation layer 130, and the second light receiving unit 150. Therefore, for example, according to the method for manufacturing the light receiving element 100 according to this embodiment, the first light receiving unit 110 and the second light receiving unit 150 are bonded and stacked using solder or the like. It is possible to provide the light receiving element 100 that can manufacture the element 100 with good reproducibility and has high reliability.

2. Second Embodiment Next, an optoelectronic integrated device 300 and an optical module 700 to which the light receiving device 100 according to the first embodiment is applied will be described with reference to FIG. FIG. 11 is a cross-sectional view schematically showing the optoelectronic integrated device 300 and the optical module 700 according to this embodiment.

  As shown in FIG. 11, the optoelectronic integrated device 300 includes a light receiving device 100 and a TIA (Trans-Impedance Amplifier) 350. The TIA 350 is configured by, for example, a heterojunction bipolar transistor. The light receiving element 100 and the TIA 350 are formed on the submount substrate 406.

  The optical module 700 includes a receiving unit 400, a transmitting unit 500, and an electronic circuit unit 600. The electronic circuit unit 600 includes an amplifier circuit unit 610 and a drive circuit unit 620.

  The receiving unit 400 includes a submount substrate 406, an optoelectronic integrated device 300, a housing unit 402, and a glass unit 404.

  The transmission unit 500 includes a submount substrate 508, a light emitting element 510, a monitor photodiode 512, an oblique glass unit 504, and a housing unit 502. The light emitting element 510 and the monitor photodiode 512 are formed on the submount substrate 508.

  The casing unit 402 is formed of a resin material, and is formed integrally with a sleeve 420 and a condensing unit 405 described later. Similarly, the housing portion 502 is formed of a resin material and is formed integrally with a sleeve 520 described later. As the resin material, a material that can transmit light is selected. For example, polymethyl methacrylate (PMMA), epoxy resin, phenol resin, diallyl phthalate, phenyl methacrylate, fluorine resin used for plastic optical fiber (POF). A polymer or the like can be employed.

  The sleeves 420 and 520 are formed in a shape in which a light guide member (not shown) such as an optical fiber can be fitted from the outside, and constitute a part of the peripheral wall of the accommodation spaces 422 and 522. The condensing part 405 condenses and sends out the optical signal from the light guide member. Thereby, the loss of light from the light guide member can be reduced, and the light coupling efficiency between the light receiving element 100 and the light guide member can be improved.

  The oblique glass portion 504 is provided in the accommodation space 522 and between the sleeve 520 and the light emitting element 510. The oblique glass portion 504 reflects and transmits light from the light emitting element 510. The monitor photodiode 512 receives the light reflected by the oblique glass portion 504. The drive circuit unit 620 adjusts the amount of light emitted by the light emitting element 510 in accordance with the amount of light received by the monitor photodiode 512. The light transmitted through the oblique glass portion 504 is sent out to a light guide member fitted in the sleeve 520 of the transmission unit 500.

  The light emitting element 510 converts an electrical signal input from the outside into an optical signal and outputs the optical signal to the outside through the light guide member. The light receiving element 100 receives an optical signal through the light guide member, converts this into a current, and sends the converted current to the TIA 350. The TIA 350 converts the received current into a voltage output, amplifies it, and sends it to the electronic circuit unit 600. The amplifier circuit unit 610 performs control so that the voltage output does not exceed a certain level, and outputs the voltage output to the outside. In addition, description of external terminals, such as an output terminal and input terminal of an electrical signal, is omitted.

  As described above, the light receiving element 100 is used in the optoelectronic integrated element 300 and the optical module 700.

3. Third Embodiment FIG. 12 is a diagram schematically showing a light transmission device 90 according to a third embodiment to which the present invention is applied. The light transmission device 90 connects electronic devices 92 such as a computer, a display, a storage device, and a printer to each other. The electronic device 92 may be an information communication device. The light transmission device 90 may be one in which plugs 96 are provided at both ends of the cable 94. The cable 94 can include a light guide member (for example, an optical fiber). The plug 96 includes the optical module 700 according to the second embodiment. Since the light guide member is built in the cable 94 and the optical module 700 is built in the plug 96, it is not shown. The relationship between the light guide member and the optical module 700 is as described in the second embodiment.

  The optical modules 700 according to the second embodiment are provided at both ends of the light guide member. As shown in FIGS. 11 and 12, the light receiving element 100 installed at one end of the light guide member converts an optical signal into an electrical signal, and then transmits the electrical signal via the TIA 350 and the electronic circuit unit 600. To the electronic device 92. A light emitting element 510 is installed at the other end of the light guide member. That is, in the light emitting element 510, the electrical signal output from the electronic device 92 is converted into an optical signal. This optical signal travels through the light guide member and is input to the light receiving element 100.

  As described above, according to the optical transmission device 90 of the present embodiment, information transmission between the electronic devices 92 can be performed by an optical signal.

4). Fourth Embodiment FIG. 13 is a diagram schematically showing a usage pattern of a light transmission device 90 according to a fourth embodiment to which the present invention is applied. The light transmission device 90 is connected between the electronic devices 80. As the electronic device 80, a liquid crystal display monitor or a digital CRT (may be used in the fields of finance, mail order, medical care, education, etc.), liquid crystal projector, plasma display panel (PDP), digital TV, retail store Cash register (POS for Point of Sale Scanning), video, tuner, game device, printer, and the like.

  As described above, the embodiments of the present invention have been described in detail. However, those skilled in the art can easily understand that many modifications can be made without departing from the novel matters and effects of the present invention. . Accordingly, all such modifications are intended to be included in the scope of the present invention.

  For example, a plurality of light receiving elements 100 can be arrayed. Further, for example, in the above-described embodiment, even if the p-type and the n-type in each semiconductor layer are switched, it does not depart from the spirit of the present invention. In the light receiving element 100 of the above-described embodiment, the InGaAs type and the GaInNAs type have been described. However, other material systems such as Si type, Ge type, and GaAs type are used according to the wavelength of incident light. It is also possible to use semiconductor materials such as InGaAsP and HgCdTe.

FIG. 3 is a cross-sectional view schematically showing the light receiving element according to the first embodiment. The top view which shows typically the light receiving element which concerns on 1st Embodiment. The figure which shows typically the measuring method of light reception sensitivity. The figure which shows the measurement result of the light reception sensitivity with respect to the position of a light-receiving surface. Sectional drawing which shows typically the manufacturing method of the light receiving element which concerns on 1st Embodiment. Sectional drawing which shows typically the manufacturing method of the light receiving element which concerns on 1st Embodiment. Sectional drawing which shows typically the manufacturing method of the light receiving element which concerns on 1st Embodiment. Sectional drawing which shows typically the manufacturing method of the light receiving element which concerns on 1st Embodiment. Sectional drawing which shows typically the manufacturing method of the light receiving element which concerns on 1st Embodiment. Sectional drawing which shows typically the manufacturing method of the light receiving element which concerns on 1st Embodiment. The figure which shows typically the optical module which concerns on 2nd Embodiment. The figure which shows typically the light transmission apparatus which concerns on 3rd Embodiment. The figure which shows typically the usage type of the optical transmission apparatus which concerns on 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light source, 12 Photodiode, 14 Light-receiving surface, 16 Lens, 80 Electronic device, 90 Light transmission apparatus, 92 Electronic device, 94 Cable, 96 Plug, 100 Light receiving element, 101 Board | substrate, 110 1st light-receiving part, 112 1st contact Layer, 113 first electrode, 114 first light absorption layer, 116 second contact layer, 117 second electrode, 120 semiconductor multilayer film, 130 separation layer, 150 second light receiving portion, 152 third contact layer, 153 third electrode 154 Second light absorption layer, 156 Fourth contact layer, 157 Fourth electrode, 170 Optical member, 172 First lens portion, 174 Second lens portion, 176 Damping member, 177 Opening portion, 179 Corner portion, 180 Incident Surface, 182 opening, 190 inkjet nozzle, 192 inkjet head, 300 light Child integrated device, 350 TIA, 400 receiving unit, 402 housing unit, 404 glass unit, 405 light collecting unit, 406 submount substrate, 420 sleeve, 422 accommodating space, 500 transmitting unit, 502 housing unit, 504 glass unit, 508 Submount substrate, 510 light emitting element, 512 monitor photodiode, 520 sleeve, 522 accommodation space, 600 electronic circuit section, 610 amplification circuit section, 620 drive circuit section, 700 optical module

Claims (16)

A substrate,
Above the substrate, a plurality of light receiving units stacked in order,
A separation layer for electrically separating each of the plurality of light receiving parts;
An optical member formed above an uppermost light receiving part among the plurality of light receiving parts,
Each of the light receiving parts
A contact layer;
A light absorbing layer formed above the contact layer;
And another contact layer formed above the light absorption layer,
The optical member is a light receiving element that focuses a plurality of lights having different wavelengths within the light absorbing layers of at least two of the light absorbing layers. In claim 1,
The optical member is a light-receiving element in which the same number of light focal points as the number of the light-receiving portions are aligned with the inside of each light-absorbing layer. In claim 1 or 2,
A light receiving element, wherein at least two of the light absorbing layers are made of the same material. A substrate,
A first light receiving portion, which is disposed from the substrate side above the substrate and includes a first contact layer, a first light absorption layer, and a second contact layer;
A separation layer formed above the second contact layer;
A second light-receiving portion disposed above the separation layer from the separation layer side and including a third contact layer, a second light absorption layer, and a fourth contact layer;
An optical member formed above the fourth contact layer,
The optical member is a light receiving element in which a light beam having a first wavelength is focused in the first light absorption layer, and a light beam having a second wavelength is focused in the second light absorption layer. In claim 4,
The first light absorption layer and the second light absorption layer are light receiving elements made of the same material. In any one of Claims 1-5,
The optical member is a light receiving element having a plurality of lens portions stacked integrally. In claim 6,
The center of each lens unit in plan view is the same or substantially the same as the center of light incident on the optical member. In claim 6 or 7,
A light receiving element in which at least two lens portions of the plurality of lens portions have different refractive indexes. In any one of Claims 6-8,
An outer edge of at least two of the plurality of lens units has a different radius of curvature. The light receiving element according to any one of claims 1 to 9,
An optoelectronic integrated device including TIA (Trans-Impedance Amplifier). The light receiving element according to any one of claims 1 to 9,
An optical module comprising a light emitting element.   An optical transmission device comprising the optical module according to claim 11. A step of sequentially stacking and forming a plurality of light receiving portions above the substrate;
Forming a separation layer for electrically separating each of the plurality of light receiving parts;
Forming an optical member above an uppermost light receiving part among the plurality of light receiving parts,
The step of forming each of the light receiving portions includes:
Forming a contact layer;
Forming a light absorption layer above the contact layer;
Forming another contact layer above the light absorbing layer,
The method of manufacturing a light receiving element, wherein the optical member is formed so that a plurality of light beams having different wavelengths are focused on the inside of at least two of the light absorption layers. A semiconductor layer for forming at least a first contact layer, a first light absorption layer, a second contact layer, a separation layer, a third contact layer, a second light absorption layer, and a fourth contact layer above the substrate Sequentially stacking layers to form a semiconductor multilayer film,
Forming a first contact layer, a first light absorption layer, a second contact layer, a separation layer, a third contact layer, a second light absorption layer, and a fourth contact layer by patterning the semiconductor multilayer film; When,
Forming an optical member above the fourth contact layer,
The optical member is formed so that the light of the first wavelength is focused in the first light absorption layer and the light of the second wavelength is focused in the second light absorption layer. Manufacturing method. In claim 13 or 14,
The method for manufacturing a light receiving element, wherein the optical member is formed by a droplet discharge method of discharging a droplet including a material of the optical member. In claim 15,
A method for manufacturing a light receiving element, including a step of forming a damming member for damming the droplet before the step of forming the optical member.

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