JP2014120628A - Photoelectric conversion device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a junction structure of a chalcopyrite compound semiconductor, capable of independently controlling the particle diameter of a chalcopyrite compound semiconductor regardless of film forming conditions of the semiconductor, and to provide a photoelectric conversion device having the junction structure.SOLUTION: A photoelectric conversion device 1 includes: a substrate 2; a plurality of lower electrode layers 10 disposed on the substrate 2; a compound semiconductor layer 13 of a chalcopyrite structure which is disposed on the lower electrode layers 10 so as to collectively cover the lower electrode layers 10 and is partitioned into a plurality of pixel cells 3; and a transparent electrode layer 4 disposed on the compound semiconductor layer 13. Fine uneven structures 5 are formed on surfaces 101 of the lower electrode layers 10 and an exposed surface 191(A) of an interlayer film 19.

Description

  The present invention relates to a bonded structure of a compound semiconductor layer having a chalcopyrite structure, a photoelectric conversion device employing the same, and a method for manufacturing the photoelectric conversion device.

  A solid-state imaging device using a chalcopyrite type semiconductor is known. For example, Patent Document 1 discloses a photoelectric conversion device that senses light from the ultraviolet light band to the visible light band, and further to the near infrared band.

JP 2011-151271 A

  With respect to a structure using a chalcopyrite compound semiconductor as in Patent Document 1, the characteristics of the structure change depending on the particle size of the chalcopyrite. For example, taking the photoelectric conversion device of Patent Document 1 as an example, the particle size of the chalcopyrite type compound semiconductor layer on the lower electrode layer is preferably as large as possible. This is because the dark current generated in the photoelectric conversion device can be reduced as the particle size increases. In order to change the particle size of a chalcopyrite type compound semiconductor, it has been conventionally necessary to adjust the film forming conditions of the compound semiconductor. For example, it is necessary to change the temperature of the substrate and the composition ratio of atoms constituting the compound semiconductor.

However, when the film forming conditions are changed, the film structure changes at all locations on the substrate. Therefore, it is difficult to selectively change only the particle size at a specific position on the substrate.
Therefore, an object of the present invention is to provide a junction structure of a chalcopyrite type compound semiconductor that can independently control the grain size of the chalcopyrite type compound semiconductor regardless of the film forming conditions of the chalcopyrite type compound semiconductor.

Another object of the present invention is to provide a photoelectric conversion device capable of independently controlling the particle size of the chalcopyrite type compound semiconductor, and a method for manufacturing the photoelectric conversion device. .
Another object of the present invention is to provide a photoelectric conversion device capable of reducing dark current and a manufacturing method thereof.

  Another object of the present invention is to provide a photoelectric conversion device capable of achieving both reduction in dark current and reduction in boundary variation between pixel cells, and a method for manufacturing the photoelectric conversion device.

  To achieve the above object, the invention according to claim 1 is disposed on the substrate so as to cover the substrate, the lower electrode layer disposed on the surface of the substrate, and the surface of the lower electrode layer. It is a photoelectric conversion device including a compound semiconductor layer having a chalcopyrite structure, a transparent electrode layer disposed on the compound semiconductor layer, and a fine concavo-convex structure formed on at least the surface of the lower electrode layer.

  According to this configuration, the particle diameter of the compound semiconductor having a chalcopyrite structure can be changed in accordance with the shape (pitch, depth, etc.) of the fine concavo-convex structure. Therefore, it is possible to control the particle size at the portion where the fine concavo-convex structure is formed independently from the film forming conditions of the compound semiconductor layer. In this photoelectric conversion device, since a fine concavo-convex structure is formed at least on the lower electrode layer, the quantum efficiency can be improved and the dark current can be reduced by controlling the particle size as large as possible.

According to a second aspect of the present invention, a plurality of the lower electrode layers are arranged at intervals, and the fine uneven structure is selectively formed in a region between the lower electrode layers on the surface of the substrate. It is the photoelectric conversion apparatus of Claim 1 currently formed.
According to this configuration, since the fine concavo-convex structure is formed in the region between the lower electrode layers, that is, the region between adjacent pixel cells, by controlling the particle size as small as possible, The amount of deviation of the boundary can be reduced. Therefore, the variation in the boundary between pixel cells can be reduced.

As in the invention described in claim 3, it is preferable that the pitch of the fine concavo-convex structure is 1000 nm or less.
Specifically, as in the invention described in claim 4, when the lower electrode layer is made of W, the pitch of the fine uneven structure is preferably 500 nm or more. As a result, a chalcopyrite compound semiconductor having a relatively large particle size can be formed on the lower electrode layer. It is preferable as defined in claim 5, if the surface of the substrate is made of SiO _2, it is preferable that the pitch of the fine uneven structure is 500nm or less. Thereby, a chalcopyrite type compound semiconductor having a relatively small particle diameter can be formed in a region between the lower electrode layers.

The compound semiconductor layer is made of a CIGS semiconductor represented by Cu _y (In _x Ga _1-x ) Se ₂ (0 ≦ y ≦ 1, 0 ≦ x ≦ 1). It is preferable.
According to a seventh aspect of the invention, the photoelectric conversion device preferably includes a circuit portion provided on the substrate. By laminating the circuit portion and the compound semiconductor layer, most of the region on the substrate can be effectively used as a light detection surface. Therefore, a photoelectric conversion device that can sufficiently secure a detection area can be designed, so that the sensitivity of the element can be improved.

As in the eighth aspect of the present invention, the circuit section may include a CMOS field effect transistor. In this case, as in the invention described in claim 9, the CMOS field effect transistor is disposed between the source layer and the drain layer selectively formed on the substrate, and between the source layer and the drain layer. And a gate electrode.
As in the invention described in claim 10, the transparent electrode layer may be made of ZnO or ITO.

As in the invention described in claim 11, the photoelectric conversion device may include a buffer layer disposed between the compound semiconductor layer and the transparent electrode layer. In this case, as in the invention of claim 12, wherein the buffer layer is made CdS, _ZnS, ZnO, from _{(Zn z Mg 1-z)} O (0 ≦ z ≦ 1), ZnSe or _{an In} 2 _{S 3} It may be.
The invention according to claim 13 is formed in a region where a base layer, a compound semiconductor layer having a chalcopyrite structure disposed on a surface of the base layer, and the compound semiconductor layer on the surface of the base layer are disposed. A chalcopyrite compound semiconductor junction structure including a fine concavo-convex structure.

According to this configuration, the particle diameter of the compound semiconductor having a chalcopyrite structure can be changed in accordance with the shape (pitch, depth, etc.) of the fine concavo-convex structure. Therefore, it is possible to control the particle size at the portion where the fine concavo-convex structure is formed independently from the film forming conditions of the compound semiconductor layer.
As in the invention described in claim 14, it is preferable that the pitch of the fine concavo-convex structure is 1000 nm or less.

  The invention according to claim 15 includes a step of forming a lower electrode layer on the surface of the substrate, and a predetermined surface treatment from the surface side of the substrate, whereby at least the surface of the lower electrode layer has a fine concavo-convex structure. Forming a chalcopyrite structure compound semiconductor layer so as to cover the surface of the lower electrode layer after forming the fine concavo-convex structure, and forming a transparent electrode layer on the compound semiconductor layer A process for manufacturing a photoelectric conversion device.

  According to this method, the particle size of the compound semiconductor having a chalcopyrite structure can be changed in accordance with the shape (pitch, depth, etc.) of the fine uneven structure. Therefore, it is possible to control the particle size at the portion where the fine concavo-convex structure is formed independently from the film forming conditions of the compound semiconductor layer. In this photoelectric conversion device, since a fine concavo-convex structure is formed at least in the lower electrode layer, the quantum efficiency can be improved and the dark current can be reduced by controlling the particle size as large as possible.

When the step of forming the lower electrode layer includes the step of forming a plurality of lower electrode layers spaced apart from each other as in the invention described in claim 16, the step of forming the fine uneven structure includes It is preferable to include a step of forming the fine irregularities simultaneously with the surface of the lower electrode layer in a region between the lower electrode layers on the surface of the substrate.
According to this method, since the fine concavo-convex structure is formed in the region between the lower electrode layers, that is, the region between the pixel cells adjacent to each other, the boundary between the pixel cells is controlled by controlling the particle size as small as possible. The amount of deviation can be reduced. Therefore, the variation in the boundary between pixel cells can be reduced.

  Preferably, the predetermined surface treatment is an etching process or a lift-off process. Further, as in the invention described in claim 18, when the etching process is employed, it is preferable to perform etching using a mask patterned by photolithography, electron beam drawing or nanoimprint. Thereby, a fine concavo-convex structure can be easily formed.

FIG. 1 is a schematic plan view of the photoelectric conversion device according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along section line II-II in FIG. FIG. 3 is a cross-sectional view for explaining a main part of the photoelectric conversion device. FIG. 4 is a diagram for explaining an example of the shape of a fine structure. FIG. 5A is a diagram illustrating a part of the manufacturing process of the photoelectric conversion device of the first embodiment. FIG. 5B is a diagram showing a step subsequent to FIG. 5A. FIG. 5C is a diagram showing a step subsequent to FIG. 5B. FIG. 5D is a diagram showing a step subsequent to FIG. 5C. FIG. 5E is a diagram showing a step subsequent to that in FIG. 5D. FIG. 5F is a diagram showing a step subsequent to that in FIG. 5E. FIG. 6 is a diagram for demonstrating that the CIGS particle size can be controlled by the fine concavo-convex structure. FIG. 7 is a diagram for explaining that the variation in the boundary between the pixel cells can be reduced by the fine concavo-convex structure. FIG. 8 is a cross-sectional view for explaining a main part of the photoelectric conversion device according to the second embodiment of the present invention. FIG. 9 is a cross-sectional view for explaining the main part of the photoelectric conversion device according to the third embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic plan view of the photoelectric conversion device according to the first embodiment of the present invention.
The photoelectric conversion device 1 is an image sensor that detects incident light and converts light energy into an electrical signal.
The photoelectric conversion device 1 may be used as a line image sensor by arranging a plurality of one-dimensionally, or may be used as an area image sensor by arranging a plurality of two-dimensionally. In addition, the photoelectric conversion device 1 performs personal authentication with a security camera (a camera that senses visible light during the day and a near-infrared light at night) and a personal authentication camera (a near-infrared light that is not affected by outside light). Camera) or in-vehicle cameras (cameras mounted in cars for night vision assistance or securing a far field of view), medical image sensors for detecting near-infrared light, and a wide range The present invention can be applied to a photodetector in the wavelength band (photodetector), an avalanche photodiode, and the like. Furthermore, you may apply the photoelectric conversion apparatus 1 to a solar cell.

The photoelectric conversion device 1 includes a substrate 2, a plurality of pixel cells 3, a transparent electrode layer 4, a metal electrode layer 6, and a plurality of pads 7.
The substrate 2 is made of, for example, silicon (Si). The substrate 2 has a size of 5 mm to 10 mm square, for example. A light receiving region 8 is formed at the center of the substrate 2 and a peripheral region 9 is formed so as to surround the light receiving region 8. The substrate 2 has a thickness of 400 μm to 1000 μm, for example. Moreover, when applying the photoelectric conversion apparatus 1 to a solar cell, the board | substrate 2 may consist of a blue plate glass (SLG). In that case, the substrate 2 preferably has a size of 50 cm × 100 cm square and a thickness of 2 mm.

  In this embodiment, the plurality of pixel cells 3 are arranged in a matrix (matrix) in the light receiving region 8, and a boundary 31 is set between adjacent pixel cells 3. In each pixel cell 3, one lower electrode layer 10 is disposed. Then, the transparent electrode layer 4 is disposed on the pixel cell 3 so as to cover the matrix-like pixel cell 3 collectively. A plurality of lower electrode layers 10 may be provided in each pixel cell 3.

The metal electrode layer 6 is made of, for example, aluminum (Al). The metal electrode layer 6 is formed in an annular shape surrounding the transparent electrode layer 4 in the peripheral region 9 and covers the peripheral edge 41 of the transparent electrode layer 4. Thereby, the metal electrode layer 6 is connected to the peripheral edge portion 41 of the transparent electrode layer 4.
The plurality of pads 7 are arranged at intervals from each other in a region spaced from the metal electrode layer 6. In this embodiment, the plurality of pads 7 are arranged linearly along each side of the substrate 2. Some (or one or more) of the plurality of pads 7 may be connected to the metal electrode layer 6 through a pad connection portion 11 formed integrally with the metal electrode layer 6. Has been. The pad connection portion 11 is formed across the pad 7 and the metal electrode layer 6.

Next, a cross-sectional structure of the photoelectric conversion device 1 will be described. FIG. 2 is a cross-sectional view taken along section line II-II in FIG.
The photoelectric conversion device 1 includes a lower electrode layer 10, a compound semiconductor layer 13, a buffer layer 14, a transparent electrode layer 4, a metal electrode layer 6, and a surface protective film 15 that are sequentially stacked on a substrate 2.
The substrate 2 has a circuit unit 12. The circuit unit 12 includes, for example, a CMOS field effect transistor. In FIG. 2, the circuit unit 12 shows a plurality of n-channel MOS transistors that constitute a part of the CMOS field effect transistor. The n-channel MOS transistor includes a source layer 16 and a drain layer 17 selectively formed on the surface of the substrate 2, a gate electrode 18 disposed between the source layer 16 and the drain layer 17, and a substrate 2. An interlayer film 19 (for example, SiO ₂ film) formed so as to cover the gate electrode 18 and a via electrode 20 penetrating the interlayer film 19 are included. A gate insulating film 21 is disposed between the gate electrode 18 and the substrate 2.

  Some of the via electrodes 20 (one or plural) may connect the lower electrode layer 10 and the gate electrode 18. Since the lower electrode layer 10 (anode) is connected to the gate electrode 18, the optical information (electric signal) detected by the compound semiconductor layer 13 is amplified by the n-channel MOS transistor. The remaining via electrode 20 (one or plural) may connect the pad 7 and the gate electrode 18. Thereby, the metal electrode layer 6 is electrically connected to the circuit unit 12 in the peripheral region 9. The configuration of the circuit unit 12 illustrated in FIG. 2 is merely an example. For example, the circuit unit 12 may be a thin film transistor having a CMOS structure formed on a thin film on a glass substrate.

  A plurality of lower electrode layers 10 are arranged in a matrix on the interlayer film 19. The thickness of each lower electrode layer 10 is, for example, about 1000 mm. The lower electrode layer 10 is made of, for example, molybdenum (Mo), niobium (Nb), tantalum (Ta), or tungsten (W). Of these, tungsten (W) is preferred. Since tungsten (W) has a higher reflectance than other materials, not only the light incident on the compound semiconductor layer 13 but also the light reflected by the lower electrode layer 10 can be detected by the compound semiconductor layer 13. Further, since tungsten (W) can be easily processed using LSI manufacturing technology, the size of the lower electrode layer 10 can be easily controlled.

  The compound semiconductor layer 13 is partitioned into a plurality of pixel cells 3 by boundaries 31. The compound semiconductor layer 13 preferably has a thickness of 0.1 μm to 2 μm, and specifically has a thickness of about 1.2 μm. Moreover, when applying the photoelectric conversion apparatus 1 to a solar cell, it is preferable that the compound semiconductor layer 13 has a thickness of about 1.8 μm.

The compound semiconductor layer 13 is made of a compound semiconductor having a chalcopyrite structure. A compound semiconductor having a chalcopyrite structure has the same crystal structure as chalcopyrite, and is represented by, for example, composition formulas I-III-VI ₂ and II-IV-V ₂ . However, the Roman numeral in the composition formula indicates the group number of the periodic table. For example, the Roman numeral I is a group IB element and II is a group IIB element. In the composition formula, group IB elements include, for example, Cu, Ag, and the like, group IIIB elements include, for example, Al, Ga, In, and the like, and group VIB elements include, for example, S, Se, Te, and the like. The group IIB element includes, for example, Zn, Cd, etc., the group IVB element includes, for example, Si, Ge, Sn, and the like, and the group VB element includes, for example, P, As, Sb, and the like. In particular, the compound semiconductor having a chalcopyrite structure preferably has an I-III-VI ₂ type chalcopyrite structure, and Cu _y (In _x Ga _1-x ) Se ₂ (0 ≦ y ≦ 1, 0 ≦ x ≦ 1) The CIGS type semiconductor shown by is more preferable. CIGS semiconductors have good light from the near ultraviolet band (wavelength range: about 300 nm to 380 nm) through the visible light band (wavelength range: about 380 nm to 780 nm) to the near infrared band (wavelength range: about 780 nm to about 1300 nm). Can be absorbed into.

The buffer layer 14 is formed so as to cover almost the entire upper surface of the compound semiconductor layer 13. The peripheral edge 131 of the compound semiconductor layer 13 is not covered with the buffer layer 14, and is drawn from the buffer layer 14 in the lateral direction along the surface of the substrate 2. An insulating film 22 is formed so as to cover the peripheral portion 131 (upper surface and side surface) of the compound semiconductor layer 13 and the upper surface of the surrounding interlayer film 19. The buffer layer 14 has a thickness of 100 to 10,000 mm, for example. Buffer layer 14, CdS, ZnS, _ZnO, be made of _{(Zn z Mg 1-z)} O (0 ≦ z ≦ 1), ZnSe or _{an In} 2 _{S 3} preferred.

The transparent electrode layer 4 is formed so as to cover the entire upper surface of the buffer layer 14. The transparent electrode layer 4 has a thickness of 100 to 10,000 mm, for example.
The transparent electrode layer 4 has a thickness of 100 to 10,000 mm, for example.
The metal electrode layer 6 is formed on the laminated structure of the compound semiconductor layer 13, the buffer layer 14, and the transparent electrode layer 4, and the top portion covers the peripheral edge portion 41 (upper surface and side surface) of the transparent electrode layer 4. The metal electrode layer 6 and the compound semiconductor layer 13 and the buffer layer 14 are insulated from each other by the insulating film 22. The lower part of the metal electrode layer 6 is disposed on the interlayer film 19 in the lateral direction along the surface of the substrate 2 and is connected to the pad 7 via the pad connection part 11.

The surface protective film 15 is made of an insulating material such as silicon nitride (Si ₃ N ₄ ), for example. The surface protective film 15 is formed so as to cover the metal electrode layer 6, the pad connection portion 11, and the pad 7. The metal electrode layer 6 is completely covered with the surface protective film 15 so as not to be exposed. Further, a part of the pad 7 is selectively exposed from the opening formed in the surface protective film 15.
Next, the main part of the photoelectric conversion apparatus 1 will be described. FIG. 3 is a cross-sectional view for explaining a main part of the photoelectric conversion device 1.

  In the first embodiment, a fine concavo-convex structure 5 is formed on at least the surface 101 of the lower electrode layer 10. In this embodiment, the fine concavo-convex structure 5 is selectively formed on an exposed surface parallel to the main surface of the substrate 2. That is, the fine concavo-convex structure 5 is the surface of the substrate 2 in the region along the boundary 31 between the surface 101 of the lower electrode layer 10 and the end face 102 of the lower electrode layer 10 (specifically, the surface 191 of the interlayer film 19). ) And selectively formed. On the other hand, a surface that intersects the main surface of the substrate 2 (for example, the end surface 102 of the lower electrode layer 10) or a surface that is covered even with the parallel surface (for example, the interlayer film 19 covered with the lower electrode layer 10). The surface 191) is a smooth surface on which the fine uneven structure 5 is not formed.

  The fine concavo-convex structure 5 is formed, for example, by arranging fine convex portions and concave portions alternately. The arrangement pattern of the convex portions and the concave portions may be, for example, a stripe pattern or a dot pattern. In addition, when a certain plane has an exposed surface and a coated surface, and the fine uneven structure 5 is selectively formed on the exposed surface, the fine uneven structure 5 It is formed so as to be in the same plane as the covering surface. Specifically, as shown in FIG. 3, the surface 191 of the interlayer film 19 includes an exposed surface 191 (A) exposed between the lower electrode layers 10 and a covered surface 191 (B) covered with the lower electrode layer 10. ) Are located on the same plane as the covering surface 191 (B).

Further, the shape of the fine concavo-convex structure 5 may be, for example, a triangular shape, a trapezoidal shape, a quadrangular shape, or a semi-elliptical shape as viewed from the left in FIG. Note that the shape shown in FIG. 4 is only an example of the shape of the fine concavo-convex structure 5, and may be another shape such as a circular cross-sectional view.
The “fine” of the fine concavo-convex structure 5 is, for example, fine enough not to affect the surface state of the layer formed thereon. Therefore, in this embodiment, the surface 131 of the compound semiconductor layer 13 laminated on the lower electrode layer 10 and the interlayer film 19 on which the fine concavo-convex structure 5 is formed is smooth without inheriting the concavo-convex pattern of the fine concavo-convex structure 5. It is a surface.

Specifically, the pitch P ₁ of the fine concavo-convex structure 5 (the step pitch between the convex part and the concave part) is preferably 1000 nm or less. When the lower electrode layer 10 is made of tungsten, the pitch P ₁ of the fine concavo-convex structure 5 is preferably 500 nm to 1000 nm. As a result, a chalcopyrite compound semiconductor having a relatively large particle size can be formed on the lower electrode layer 10. On the other hand, when the surface of the substrate 2 is made of SiO ₂ as in this embodiment, the pitch P ₁ of the fine concavo-convex structure 5 is preferably 500 nm or less (for example, 100 nm to 500 nm). Thereby, a chalcopyrite compound semiconductor having a relatively small particle diameter can be formed in a region between the lower electrode layers 10. Therefore, when the lower electrode layer 10 is made of tungsten and the surface of the substrate 2 is made of SiO ₂ , the pitch P ₁ is preferably 375 nm to 750 nm, for example. Within this range, the particle size on the interlayer film 19 can be controlled to be small while the particle size on the lower electrode layer 10 is controlled to be large. The depth _{D 1} of the fine uneven structure 5 (depth of the concave portion), for example, is preferably 30Nm～120nm.

  The transparent electrode layer 4 is electrically connected to the compound semiconductor layer 13 through the buffer layer 14. The transparent electrode layer 4 is preferably made of zinc oxide (ZnO). For example, in this embodiment, a non-doped ZnO film (i-ZnO film 42) and an n-type ZnO are sequentially formed from the side closer to the compound semiconductor layer 13. A film (n-ZnO film 43) is laminated. For example, the i-ZnO film 42 is preferably about 1500 mm thick, and the n-ZnO film 43 is preferably about 3000 mm thick. The transparent electrode layer 4 may be indium tin oxide (ITO).

5A to 5F are diagrams illustrating a part of the manufacturing process of the photoelectric conversion device according to the first embodiment in the order of processes.
In the manufacturing process of the photoelectric conversion device 1, first, as shown in FIG. 5A, a via electrode 20 reaching the gate electrode 18 is formed so as to penetrate the interlayer film 19 of the substrate 2 on which the CMOS field effect transistor is formed. .

Next, as shown in FIG. 5B, tungsten (W) is deposited on the interlayer film 19 by, for example, sputtering, and then the tungsten is patterned (etched), whereby the plurality of lower electrode layers 10 are formed. It is formed in a matrix.
Next, a surface treatment process for providing the fine concavo-convex structure 5 is performed from the surface 191 side of the interlayer film 19. The surface treatment step can be performed by, for example, an etching process or a lift-off process. In the etching process, for example, a mask patterned by photolithography, electron beam lithography, or nanoimprint may be used. By this surface treatment, the fine concavo-convex structure 5 is selectively formed on the surface 101 of the lower electrode layer 10 and the exposed surface 191 (A) of the interlayer film 19 which are exposed surfaces parallel to the main surface of the substrate 2. The

Next, as shown in FIG. 5C, a compound semiconductor layer 13 that covers the plurality of lower electrode layers 10 at once is stacked on the interlayer film 19 by, for example, MBE (Molecular Beam Epitaxy). At this time, the surface 131 of the compound semiconductor layer 13 is formed as a smooth surface without inheriting the uneven pattern of the fine uneven structure 5.
Next, as shown in FIG. 5D, the buffer layer 14 is stacked on the compound semiconductor layer 13 by, for example, a CBD (Chemical Bath Deposition) method.

Next, for example, by sputtering, the i-ZnO film 42 is stacked on the buffer layer 14 as shown in FIG. 5E, and the n-ZnO film 43 is stacked on the i-ZnO film 42 as shown in FIG. 5F. The Thereby, the transparent electrode layer 4 is formed. Thereafter, the metal electrode layer 6 and the surface protective film 15 are formed, whereby the photoelectric conversion device 1 of FIGS. 1 to 3 is obtained.
As described above, according to this embodiment, the particle size of the chalcopyrite structure compound semiconductor in the portion where the fine uneven structure 5 of the photoelectric conversion device 1 is formed is changed to the shape of the fine uneven structure 5 (FIG. 4). The pitch P ₁ , the depth D _1, etc.) can be changed. That is, the particle size in the portion where the fine uneven structure 5 is formed can be controlled independently from the film forming conditions of the compound semiconductor layer 13 (in this embodiment, MBE conditions). Such an effect can be demonstrated with reference to FIG.

FIG. 6 is a diagram for demonstrating that the CIGS grain size can be controlled by the fine concavo-convex structure 5. In this example, first, a fine concavo-convex structure 5 having a depth D ₁ = 60 nm and a quadrangular shape in cross section has a pitch P ₁ (step pitch) = 0 nm (that is, no fine concavo-convex structure), 1000 nm, 500 nm, 250 nm and Samples formed on tungsten (W) and SiO ₂ were prepared by changing the thickness to 100 nm. Next, a CIGS semiconductor was grown on each sample, and the particle size was measured.

  From FIG. 6, the grain size of the CIGS-based semiconductor on tungsten has a fine step structure in the range of 1000 nm to 500 nm (the number of steps increases), and there is no fine uneven structure 5 (grain size = about 200 nm). It turned out to be bigger. For example, it has been found that the maximum control is possible up to about 3 times 600 nm. On the other hand, it was also found that the size was smaller in the range of 500 nm to 250 nm than in the case without the fine concavo-convex structure 5, and at 250 nm or less, it was flat with a smaller particle size than in the case without the fine concavo-convex structure 5.

The particle size of the CIGS-based semiconductor on SiO ₂ is smaller than 1000 nm (the particle size = about 800 nm) as the step pitch becomes smaller (steps increase) and the fine uneven structure 5 does not exist (particle size = about 800 nm). all right. For example, it has been found that the control can be as small as about 0.25 times to about 200 nm. On the other hand, it was found that the thickness is larger than 1000 nm than when there is no fine uneven structure 5.

  From the result of FIG. 6, it can be seen that in this embodiment, the grain size of the CIGS semiconductor on the lower electrode layer 10 can be controlled as large as possible by designing the step pitch of the fine concavo-convex structure 5 to 500 nm to 1000 nm. . On the other hand, by designing the step pitch of the fine concavo-convex structure 5 to be less than 1000 nm (more specifically, 100 nm to 500 nm), the grain size of the CIGS semiconductor on the exposed surface 191 (A) of the interlayer film 19 can be made. It can be seen that the control can be as small as possible. Therefore, in order to control the particle size on the interlayer film 19 to be small while controlling the particle size on the lower electrode layer 10 to be large, for example, it is preferable to be 375 nm to 750 nm.

For example, FIG. 7 shows a comparison between the case where there is no fine uneven structure 5 (step pitch = 0 nm) and the case where the fine uneven structure 5 having a step pitch of 500 nm is formed. In FIG. 7, the larger the squares partitioned in the compound semiconductor layer 13, the larger the particle size of the CIGS semiconductor in that portion.
That is, the grain size of the CIGS semiconductor on the lower electrode layer 10 is several times larger in the example of the step pitch 500 nm in FIG. 7B than in the example of the step pitch 0 nm in FIG. . Thereby, compared with the case of Fig.7 (a), while being able to improve quantum efficiency, dark current can be reduced.

On the other hand, the particle size of the CIGS semiconductor on the exposed surface 191 (A) of the interlayer film 19 is a fraction of that of the example of the step pitch of 0 nm in FIG. Thereby, even if the boundary 31 (part) of the original pixel cell 3 indicated by the solid line in FIG. 7B is shifted to the adjacent pixel cell 3 side as indicated by the broken line or the alternate long and short dash line, the shift amount G _1, can be smaller than the deviation amount _{G 2} in FIG. 7 (a). As a result, the variation in the boundary 31 between the pixel cells 3 can be reduced.

Therefore, when the step pitch of the fine structure 5 is 500 nm, it is possible to achieve both reduction of dark current and reduction in boundary variation between the pixel cells 3. As described above, the embodiments of the present invention have been described. Can also be implemented in other forms.
For example, in the above-described embodiment, the compound semiconductor layer 13 is formed so as to cover the plurality of lower electrode layers 10 at once. However, like the photoelectric conversion device 81 of FIG. A plurality of them may be arranged one by one. In this case, an interlayer film 23 made of an insulating material may be formed between the compound semiconductor layers 13 adjacent to each other.

  In the above-described embodiment, the configuration in which the lower electrode layer 10 is formed on the interlayer film 19 is shown. However, the lower electrode layer 10 may be embedded in the interlayer film 19. In this case, like the photoelectric conversion device 91 of FIG. 9, the lower electrode layer 10 may be completely embedded so that the upper surface thereof is flush with the surface of the interlayer film 19, or a part of the lower electrode layer 10 may be interlayer. The surface of the film 19 may protrude upward.

  Further, for example, various circuit elements such as a capacitor and a resistor may be formed on the substrate 2 in addition to the CMOS field effect transistor. In addition, these circuit elements enable integrated circuits such as SSI (Small Scale Integration), MSI (Medium Scale Integration), LSI (Large Scale Integration), VLSI (Very Large Scale Integration), ULSI (Ultra-Very Large Scale Integration), etc. May be configured.

  The fine concavo-convex structure of the present invention is not limited to the photoelectric conversion device shown in the above-described embodiment, but can be applied to various applications including a junction structure in which a compound semiconductor layer having a chalcopyrite structure is stacked on a base substrate. be able to. For example, it can be applied to applications that require control of electric conduction, heat conduction, and surface area. Specifically, in a catalyst in which a compound semiconductor layer having a chalcopyrite structure is used, by forming a fine concavo-convex structure with an appropriate step pitch at the contact portion with the reactant, a chalcopyrite structure having a diameter as small as possible is possible. Compound semiconductors can be grown. Thereby, the surface area of a catalyst can be enlarged and reaction efficiency can be improved.

  In addition, various design changes can be made within the scope of matters described in the claims.

DESCRIPTION OF SYMBOLS 1 Photoelectric conversion apparatus 2 Board | substrate 4 Transparent electrode layer 5 Fine uneven structure 10 Lower electrode layer 12 Circuit part 13 Compound semiconductor layer 14 Buffer layer 16 Source layer 17 Drain layer 18 Gate electrode 23 Groove 42 i-ZnO film 43 n-ZnO film 81 Photoelectric conversion device 91 Photoelectric conversion device 101 Surface (of lower electrode layer) 191 (A) Exposed surface (of interlayer film)

Claims (18)

A substrate,
A lower electrode layer disposed on a surface of the substrate;
A compound semiconductor layer having a chalcopyrite structure disposed on the substrate so as to cover the surface of the lower electrode layer;
A transparent electrode layer disposed on the compound semiconductor layer;
A photoelectric conversion device including at least a fine concavo-convex structure formed on the surface of the lower electrode layer. A plurality of the lower electrode layers are arranged spaced apart from each other;
The photoelectric conversion device according to claim 1, wherein the fine concavo-convex structure is selectively formed in a region between the lower electrode layers on the surface of the substrate.   The photoelectric conversion device according to claim 1 or 2, wherein a pitch of the fine concavo-convex structure is 1000 nm or less.   The photoelectric conversion device according to claim 3, wherein the lower electrode layer is made of W, and a pitch of the fine concavo-convex structure is 500 nm or more. 5. The photoelectric conversion device according to claim 3, wherein the surface of the substrate is made of SiO ₂ , and a pitch of the fine concavo-convex structure is 500 nm or less. The compound semiconductor layer _is made of a CIGS semiconductor represented by _{Cu y (In x Ga 1-} x) Se 2 (0 ≦ y ≦ 1,0 ≦ x ≦ 1), any one of claims 1 to 5 The photoelectric conversion device described in 1.   The said photoelectric conversion apparatus is a photoelectric conversion apparatus as described in any one of Claims 1-6 containing the circuit part provided in the said board | substrate.   The photoelectric conversion device according to claim 7, wherein the circuit unit includes a CMOS field effect transistor.   9. The photoelectric field effect transistor according to claim 8, wherein the CMOS field effect transistor includes a source layer and a drain layer selectively formed on the substrate, and a gate electrode disposed between the source layer and the drain layer. Conversion device.   The photoelectric conversion device according to claim 1, wherein the transparent electrode layer is made of ZnO or ITO.   The said photoelectric conversion apparatus is a photoelectric conversion apparatus as described in any one of Claims 1-10 containing the buffer layer arrange | positioned between the said compound semiconductor layer and the said transparent electrode layer. The buffer _{layer, CdS, ZnS, ZnO, (} Zn z Mg 1-z) O (0 ≦ z ≦ 1), made of ZnSe or _In 2 _{S 3,} the photoelectric conversion device according to claim 11. The base layer,
A compound semiconductor layer having a chalcopyrite structure disposed on the surface of the base layer;
A chalcopyrite type compound semiconductor junction structure including a fine concavo-convex structure formed in a region where the compound semiconductor layer is disposed on the surface of the base layer.   The joint structure of a chalcopyrite type compound semiconductor according to claim 13, wherein the pitch of the fine concavo-convex structure is 1000 nm or less. Forming a lower electrode layer on the surface of the substrate;
Forming a fine concavo-convex structure on at least the surface of the lower electrode layer by applying a predetermined surface treatment from the surface side of the substrate;
Forming a chalcopyrite structure compound semiconductor layer so as to cover the surface of the lower electrode layer after the formation of the fine concavo-convex structure;
Forming a transparent electrode layer on the compound semiconductor layer. The step of forming the lower electrode layer includes a step of forming a plurality of lower electrode layers spaced apart from each other,
The step of forming the fine uneven structure includes the step of forming the fine unevenness simultaneously with the surface of the lower electrode layer in a region between the lower electrode layers on the surface of the substrate. The manufacturing method of the photoelectric conversion apparatus of description.   The method for manufacturing a photoelectric conversion device according to claim 15, wherein the predetermined surface treatment is an etching process or a lift-off process.   The method for manufacturing a photoelectric conversion device according to claim 17, wherein the etching process is performed using a mask patterned by photolithography, electron beam lithography, or nanoimprint.

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