JP2014103347A - Light receiving element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light receiving element which can reduce sensitivity variation, can be designed easily and can simultaneously detect multiple colors with high sensitivity and high resolution.SOLUTION: A light receiving element includes: a second conductive type first diffusion layer (2) which is formed on a first conductive type substrate (1) and forms first junction (JN1) on an interface between the substrate (1) and the first diffusion layer (2); a first conductive type second diffusion layer (3) which is formed on the first diffusion layer (2) and forms second junction (JN2) on an interface between the first diffusion layer (2) and the second diffusion layer (3); and a second conductive type third diffusion layer (4) which is formed on the second diffusion layer (3) and forms third junction (JN3) on an interface between the second diffusion layer (3) and the third diffusion layer (4). The first junction (JN1), the second junction (JN2) and the third junction (JN3) are respectively formed in the preset depth in a substrate depth direction so as to detect light having the preset wavelength. An impurity concentration peak is formed in the preset depth in the substrate depth direction on the second diffusion layer (3) on the front surface side of the substrate (1) of the second junction (JN2) and the third diffusion layer (4) on the front surface side of the substrate (1) of the third junction (JN3).

Description

  The present invention relates to a light receiving element.

  In recent years, with the spread of digital still cameras, devices such as CCDs (Charge Coupled Devices) are often used as image input devices. These have a role of converting an image obtained from an optical system into an electric signal by placing a photoelectric conversion device such as a CCD at a position where a film of a conventional film camera is located.

  In recent years, mobile phone devices are also required to reduce power consumption for image display devices such as television devices in consideration of environmental problems such as global warming. For this reason, by installing a single-pixel color sensor, the backlight is adjusted more delicately due to differences in lighting such as LED (Light Emitting Diode) lighting and light bulbs, and the beauty and current consumption of the screen are reduced. Movements that contribute to the reduction are emerging. Furthermore, the number of portable devices equipped with a television function or the like is increasing, and such portable devices are further required to reduce power consumption because they are driven by batteries. For this reason, the use of a proximity sensor (ranging sensor) to automatically turn off the screen display when no one is present is also being studied.

  A device to be a photoelectric conversion device is composed of a plurality of light receiving elements. The light receiving element itself cannot identify the color and can only detect the intensity (light quantity) of light. Therefore, when converting an image into an electrical signal, in order to identify the color, a color filter is put on each light receiving element, and the light amounts of the three primary colors of light, green, red, and blue, are detected by each light receiving element. Thus, the color signal of the light receiving element is obtained. A device that obtains a color signal from such a plurality of light receiving elements generally uses green, red, and blue color filters arranged in a mosaic shape called a Bayer array. In the Bayer array, the green color filter is most densely arranged according to the luminance information and the sensitivity characteristic of the human eye, and two pixels are arranged in a block of four pixels. Blue and red color filters are arranged for each remaining pixel. A color signal of an image is detected using a CCD having a color filter having such a structure.

  When the mosaic color filter is used, it is popular because only one CCD light receiving element is required because of its high cost. However, in this method, a color filter must be formed after the normal CCD / CMOS imager process, and furthermore, since the infrared light cannot be cut with the color filter, an expensive infrared light cut glass is formed. There was a need.

  In addition, as the actual color information of the pixels, when the red, green, and blue color filters are used, only 1/3 of the total number of pixels can be obtained, and color reproducibility, generation of false colors, edge There was a problem in the reproducibility of the part. In addition, in order to distinguish between people and things, technology to obtain near-infrared light is advancing, but if you increase the number of color filter types to obtain various color information in addition to red, blue and green, Accordingly, the number of pixels assigned to each color is reduced and the resolution is sacrificed, so that there is a problem that the arrangement of color filters of three or more colors is not realistic.

  In order to solve the above problem, the light absorption layer is divided from the element surface in the substrate depth direction, so that the absorption length differs depending on the wavelength of light without using a color filter like a CCD or CMOS imager. A light receiving element for detecting a color is known (see, for example, JP-T-2002-513145 (Patent Document 1)).

  With such a light receiving element that divides the light absorption layer from the element surface in the substrate depth direction, color division is performed in the substrate depth direction, so there is no need to consider the reduction in resolution due to the number of colors as described above. A light receiving element that does not have the above-described problems can be realized.

  In the conventional light receiving element that divides the light absorption layer from the surface of the element in the substrate depth direction, N-type semiconductors and P-type semiconductors are alternately stacked on a P-type substrate, and three junctions having different depths are formed. By forming the light, for example, light of three colors of blue, green, and red having different penetration lengths in the order of shallow junctions are absorbed and converted into electrical signals at the three junctions, respectively.

  The light receiving element will be described with reference to FIG. An N-type well region (N-type diffusion layer 302) is formed on the P-type silicon substrate 301 at a depth of about 2.0 μm from the surface, and about 0. 0 inside the N-type well region (N-type diffusion layer 302). A P-type well region (P-type diffusion layer 303) is formed at a depth of 6 μm. An N-type diffusion layer 304 is formed at a depth of 0.2 μm inside the P-type well region (P-type diffusion layer 303). And between the P-type silicon substrate 301 and the N-type well region (N-type diffusion layer 302), between the N-type well region (N-type diffusion layer 302) and the P-type well region (P-type diffusion layer 303), Photocurrent sensors S301, S302, and S303 are provided between the P-type well region (P-type diffusion layer 303) and the N-type diffusion layer 304, respectively, and the first junction JN301 collects red photons. The second junction JN302 collects green photons, and the third junction JN303 collects blue photons.

  Here, a method of generating a photocurrent will be considered more specifically. For example, some of the optical carriers generated in the P-type silicon substrate 301 by incident light do not reach the junction and disappear due to recombination, but most of them are collected by the first junction JN301.

  In addition, among the optical carriers generated in the N-type well region (N-type diffusion layer 302), the optical carriers generated near the first junction JN301 are collected by the first junction JN301 and generated near the second junction JN302. Optical carriers are collected at the second junction JN302.

  Also, the optical carriers generated in the P-type well region (P-type diffusion layer 303) are the same as those in the N-type well region, and the optical carriers generated near the second junction JN302 are collected by the second junction JN302, and the remaining Optical carriers are collected at the third junction JN303.

  Furthermore, some of the optical carriers generated in the N-type diffusion layer 304 disappear due to surface recombination, but most of them are collected in the third junction JN303.

  Here, the longer the wavelength of incident light on the P-type silicon substrate 301, the deeper the light enters the silicon before being absorbed. Most of the blue light having a wavelength of 400 to 490 nm is absorbed by the P-type silicon substrate 301 at a depth of about 0.2 to 0.5 μm. Most of the green light having a wavelength of 490 to 575 nm is absorbed by the P-type silicon substrate 301 at a depth of about 0.5 to 1.5 microns. Red light having a wavelength of 575 to 700 nm is absorbed by silicon at a depth of about 1.5 to 3.0 microns. Utilizing this difference in penetration length, red, green, and blue light are mainly extracted by the photocurrent sensors S301, S302, and S303. The photocurrents output from the photocurrent sensors S301, S302, and S303 have characteristics as shown in FIG.

JP-T-2002-513145

  A method for manufacturing a light receiving element in which the light absorption layer is divided in the substrate depth direction from the element surface will be described with reference to FIGS. The manufacturing methods of the photocurrent sensors S301, S302, S303 and the wiring layer follow a process similar to a CMOS (Complementary Metal-Oxide Semiconductor) process.

First, as shown in FIG. 6, an N-type is used at a predetermined position on the upper surface of a P-type silicon substrate 301 having a relatively low impurity concentration (for example, about 1 × 10 ¹⁵ cm ⁻³ ). Phosphorus ions are introduced into the vicinity of the surface by ion implantation on a region to be a well region (N-type diffusion layer 302), and are diffused to a depth of about 2.0 μm by heat treatment.

  Subsequently, similarly, using photolithography technology or the like, boron ions are introduced by ion implantation near the surface on the region to be the P-type well region (P-type diffusion layer 303), and a depth of 0.6 μm is obtained by heat treatment. Let it diffuse.

  Further, phosphorus ions are introduced into a region to be an N + layer (N-type diffusion layer 304) by a similar method using a photolithography technique or the like, and activated by heat treatment. By the above method, a triple diffusion layer is formed on the P-type silicon substrate. Here, the manufacturing method of the contact, wiring, and circuit portion is omitted.

  FIG. 8 shows an impurity concentration profile in the X2-Y2 cross section shown in FIG. 6 according to this manufacturing method. As shown in FIG. 8, in a general laminated light receiving element, the impurity concentration decreases as the depth increases from the substrate surface toward the substrate depth direction. As a result, optical carriers generated in the N-type well region (N-type diffusion layer 302) reach the first and second junctions JN301 and JN302 only according to the electric field applied to the first and second junctions JN301 and JN302. Instead, the built-in electric field from the surface toward the substrate due to this impurity concentration gradient tends to move (drop) toward the first junction JN301. The same applies to the P-type well region (P-type diffusion layer 304), and the built-in electric field due to the concentration gradient makes it easier to move to the second junction JN302 side of the second and third junctions JN302 and JN303.

  Such conventional light receiving elements as described above have the following problems (i) to (iii).

  (i) The first problem is that the optical carrier moving to each junction varies due to the variation in the impurity concentration gradient, and as a result, the sensitivity varies easily.

  (ii) The second problem is that the optical carrier tends to move to the substrate side due to the impurity concentration gradient, so that the sensitivity of the junction close to the surface tends to be low.

  (iii) The third problem is that it is difficult to predict which junction will move to which junction due to the impurity concentration gradient, and it is difficult to predict sensitivity when designing a device.

  The photocurrent output from each diffusion layer in the conventional light receiving element structure is extracted as a positive current in the N type and as a negative current in the P type. It is desirable that the circuits for calculating the intensity of the photocurrent output from each layer have exactly the same circuit configuration in order to minimize the circuit error. At this time, the direction of the current extracted from the diffusion layer is as described above. If they are different, the circuit configuration must be changed according to the direction of the extracted current.

  The present invention has been made in view of these problems, and it is an object of the present invention to provide a light receiving element that can reduce sensitivity variation, can be easily designed, and can simultaneously detect multiple colors with high sensitivity and high resolution. To do.

In order to solve the above problems, the light receiving element of the present invention is:
A first conductivity type substrate;
A first diffusion layer of a second conductivity type formed on the substrate and forming a first junction at an interface with the substrate;
A second diffusion layer of a first conductivity type formed on the first diffusion layer and forming a second junction at the interface with the first diffusion layer;
A third diffusion layer of a second conductivity type formed on the second diffusion layer and forming a third junction at the interface with the second diffusion layer;
The first junction, the second junction, and the third junction are each formed at a preset depth in the substrate depth direction in order to detect light having a preset wavelength,
In the diffusion layer on the substrate surface side that forms one of the first junction, the second junction, and the third junction, an impurity concentration peak has a depth set in advance in the substrate depth direction. It is formed.

In the light receiving element of one embodiment,
The impurity concentration peak is formed at a depth in the substrate depth direction corresponding to a penetration depth in the substrate with respect to light having a preset wavelength.

In the light receiving element of one embodiment,
A fourth diffusion layer of the first conductivity type is formed on the third diffusion layer and forms a fourth junction at the interface with the third diffusion layer.

In the light receiving element of one embodiment,
Among the diffusion layers, the impurity concentration profile of the diffusion layer formed on the most surface side decreases as the depth from the surface of the substrate increases in the substrate depth direction.

In the light receiving element of the present invention,
A first conductivity type substrate;
A first diffusion layer of a second conductivity type formed on the substrate and forming a first junction at an interface with the substrate;
A second diffusion layer of a first conductivity type formed on the first diffusion layer and forming a second junction at the interface with the first diffusion layer;
A third diffusion layer of a second conductivity type formed on the second diffusion layer and forming a third junction at the interface with the second diffusion layer;
A second diffusion layer of a second conductivity type formed on the substrate apart from the first diffusion layer and forming a fourth junction at the interface with the substrate;
A fifth diffusion layer of a first conductivity type formed on the fourth diffusion layer and forming a fifth junction at an interface with the fourth diffusion layer;
A sixth diffusion layer of a second conductivity type formed on the fifth diffusion layer and forming a sixth junction at an interface with the fifth diffusion layer;
A second conductivity type seventh diffusion layer formed on the sixth diffusion layer and forming a seventh junction at an interface with the sixth diffusion layer;
The depth in the substrate depth direction of the first bond and the fifth bond is the same, and
The depth of the second junction and the sixth junction in the substrate depth direction is the same, and
The depth in the substrate depth direction of the third junction and the seventh junction is the same,
An impurity concentration peak is formed at a predetermined depth in the substrate depth direction in the diffusion layer on the substrate surface side of any one of the first junction, the second junction, and the third junction. And
In the diffusion layer on the substrate surface side of any one of the fifth junction, the sixth junction, and the seventh junction, an impurity concentration peak is formed at a depth set in advance in the substrate depth direction. It is characterized by.

  As apparent from the above, according to the present invention, it is possible to realize a light receiving element that can reduce sensitivity variation and that can be easily designed and can detect multiple colors simultaneously with high sensitivity and high resolution.

FIG. 1 is a sectional view of a light receiving element according to a first embodiment of the present invention. FIG. 2 is a diagram showing an impurity concentration profile in the X1-Y1 cross section of the light receiving element. FIG. 3 is a diagram for explaining the peak range Rp when ion species are implanted. FIG. 4A is a diagram showing the result of calculating the spectral sensitivity by the arithmetic circuit in the light receiving element of the first embodiment. FIG. 4B is a diagram illustrating a result of calculating the spectral sensitivity of the blue photocurrent by the above calculation circuit. FIG. 5 is a sectional view of a light receiving element according to a second embodiment of the present invention. FIG. 6 is a sectional view of a conventional light receiving element. FIG. 7 is a diagram showing the relationship of the photocurrent with respect to the wavelength of incident light of the conventional light receiving element. FIG. 8 is a diagram showing an impurity concentration profile in the X2-Y2 cross section of the conventional light receiving element. FIG. 9 is a diagram for explaining the peak range Rp when a conventional ion species is implanted.

  Hereinafter, the light receiving element of the present invention will be described in detail with reference to the illustrated embodiments.

[First Embodiment]
FIG. 1 is a sectional view of a light receiving element according to a first embodiment of the present invention. The light receiving element 10 according to the first embodiment has a function as a color sensor.

As shown in FIG. 1, the light receiving element 10 includes a plurality of first to fourth elements on a P-type silicon substrate 1 into which a P-type impurity is introduced at a relatively low concentration (for example, 1 × 10 ¹⁵ cm ⁻³ ). The diffusion layers 2 to 5 are formed. The plurality of first to fourth diffusion layers 2 to 5 are each formed so as to form a junction at a predetermined depth in the substrate depth direction. For example, the depth of the first junction JN1 at the interface between the P-type silicon substrate 1 and the first diffusion layer 2 is 7.0 nm, and the first interface at the interface between the first diffusion layer 2 and the second diffusion layer 3 has a depth of 7.0 nm. The depth of the second junction JN2 is 3.0 nm, the depth of the third junction JN3 at the interface between the second diffusion layer 3 and the third diffusion layer 4 is 1.0 nm, and the third junction JN2 has a depth of 3.0 nm. The depth of the fourth junction JN4 at the interface between the diffusion layer 4 and the fourth diffusion layer 5 is 0.2 nm. The first junction JN1 collects infrared (wavelength 750 nm or more) optical carriers. The second junction JN2 collects red (wavelength 650 nm) optical carriers. The third junction JN3 collects green (wavelength 550 nm) optical carriers. The fourth junction JN4 collects blue (wavelength 450 nm) optical carriers.

The first concentration peak of the second diffusion layer 3 is formed at a position of 0.5 nm, and the position of the second concentration peak of the third diffusion layer 4 is formed at a position of 1.5 nm. Here, in general, considering the light absorption coefficient of silicon into blue light (450 nm) of 25000 cm ⁻¹ , the light penetration length (the depth at which light attenuates to 1 / e) is about 0.5 nm. Can be considered. Similarly, green light (550 nm) is considered to have a light penetration length of about 1.5 nm in consideration of the light absorption coefficient of 6500 cm ⁻¹ . Further, red light (650 nm) is preferably formed to a depth of 4.0 nm if the penetration depth is about 4.0 nm and a concentration peak is formed in consideration of the light absorption coefficient of 2500 cm ⁻¹ . This time, the quadruple diffusion layer is devised so that an IR cut filter is not required by removing infrared light from the red spectrum. In the conventional triple diffusion, infrared light is mixed in the red spectrum, and it is necessary to attach an IR cut filter separately, which increases the cost. The IR cut filter is composed of an interference film filter made of niobium oxide or the like, and was expensive to manufacture by laminating 40 or more layers. I can go down.

  The light receiving element includes an N-type diffusion layer 2 (first diffusion layer) formed in the P-type silicon substrate 1 and a P-type diffusion layer 3 (second diffusion layer) formed inside the N-type diffusion layer 2. Layer), an N-type diffusion layer 4 (third diffusion layer) formed inside the P-type diffusion layer 3, and a P-type diffusion layer 5 (fourth diffusion layer) formed inside the N-type diffusion layer 4. Layer) and a silicon oxide film 6 covering the entire surface of the P-type silicon substrate 1. The overlap amount of the N-type diffusion layer 2, the P-type diffusion layer 3, the N-type diffusion layer 4, and the P-type diffusion layer 5 is sufficient to prevent breakdown even when reverse bias is applied to each diffusion as a light receiving element. It is necessary to wrap.

  As a specific structure of the light receiving element 10, an N-type well region (N-type diffusion layer 2) is formed in a predetermined region on the surface side of the P-type silicon substrate 1. Ion implantation is performed on a region to be an N-type well region (N-type diffusion layer 2) using a photolithography technique or the like, phosphorus ions are introduced to a predetermined depth, and are diffused to a depth of about 7.0 nm by heat treatment. To form.

The P-type well region (P-type diffusion layer 3) changes the implantation energy of the ion implanter at a predetermined position on the region to be the N-type well region (N-type diffusion layer 2) by using a photolithography technique. Then, boron, which is a P-type impurity, is selectively introduced. For example, ion implantation is performed in multiple stages, such as 2000 keV, 1500 keV, 1000 keV, 650 keV, 500 keV, 250 keV, and 100 keV, thereby giving an impurity concentration peak at a predetermined depth. For this reason, for example, by implanting while increasing the implantation amount at an energy of 1500 keV and decreasing in order, the impurity concentration peak (region 11) is given to a predetermined depth (about 2.0 nm from the surface). A P-type well region (P-type diffusion layer 3) is formed. The impurity concentration peak of the P-type well region (P-type diffusion layer 3) is, for example, about 1 × 10 ¹⁶ to 1 × 10 ¹⁸ cm ⁻³ . This is because the P-type well region (P-type diffusion layer 3) is generally formed with a concentration of about 1 × 10 ¹⁵ to 1 × 10 ¹⁶ cm ⁻³ , but at least one digit higher than that concentration. This is because the optical carrier will overcome the potential barrier if there is no difference. In addition, when the concentration is too high and approaches 1 × 10 ¹⁹ cm ⁻³ , the sensitivity is reduced due to recombination in the high concentration region. Therefore, the impurity concentration of about 1 × 10 ¹⁶ to 1 × 10 ¹⁸ cm ⁻³ is desirable.

  An N-type well region (N-type diffusion layer 4) is formed on the surface side of the P-type well region (P-type diffusion layer 3). In the N-type well region (N-type diffusion layer 4), boron, which is an N-type impurity, is continuously introduced from the surface side by changing the implantation energy of the ion implanter. At this time, an N-type well region (N-type diffusion layer) is provided so as to have an impurity concentration peak (region 12) at a predetermined depth (about 0.5 nm from the surface) by increasing the amount of implantation at a predetermined energy. 4) is formed.

  On the surface side of the N-type well region (N-type diffusion layer 4), a P-type well region (P-type diffusion layer 5) is introduced in the vicinity of the surface by selective ion implantation using a photolithography technique. It is formed to a depth of about 0.2 nm.

  In the light receiving element 10 according to the first embodiment, the P-type silicon substrate 1 is used as the substrate. However, using the N-type silicon substrate, the P-type diffusion layer and the N-type diffusion layer are alternately arranged in order from the P-type diffusion layer. You may laminate. The substrate is not limited to silicon, but may be other semiconductors such as germanium.

  Next, the effect of the impurity concentration peak in the light receiving element 10 will be described with reference to FIG. FIG. 2 is an impurity concentration profile in the X1-Y1 cross section of the structure of the light receiving element 10 shown in FIG. In FIG. 2, the horizontal axis represents the depth in the substrate depth direction [arbitrary scale], and the vertical axis represents the impurity concentration [arbitrary scale].

  As shown in FIG. 2, by forming the first impurity concentration peak P1 to a depth of 1.5 nm, the built-in electric field due to the impurity concentration in the P-type well region (P-type diffusion layer 3) is applied to the third junction JN3. Therefore, the sensitivity of the third junction JN3 that collects green (wavelength 550 nm) optical carriers can be improved, and the optical carriers are second before and after the peak at a depth of 1.5 nm. Since it is distributed to the junction JN2 and the third junction JN3, it is not necessary to consider the concentration gradient variation as before, and the sensitivity variation can be reduced. The same applies to the second impurity concentration peak P2 in the N-type well region (N-type diffusion layer 4). These impurity concentration peaks P1 and P2 are designed according to the wavelength of light mainly absorbed by the second and third junctions JN2 and JN3, respectively.

The P-type diffusion layer 5 ion-implanted with a predetermined impurity concentration from the surface of the P-type silicon substrate 1 is also formed by introducing impurities by ion implantation from the surface side. At this time, before the ion implantation, an implantation oxide film (silicon oxide film 6) having a predetermined thickness, for example, about 28 nm is formed on the silicon surface, and as shown in FIG. The energy is adjusted so that the peak range Rp of the impurity is in the oxide film having a thickness of 28 nm. In FIG. 3, the horizontal axis represents the depth [nm] in the substrate depth direction, and the vertical axis represents the impurity concentration [cm ⁻³ ].

  As shown in FIG. 9, the conventional peak range Rp is set to be larger than the oxide film thickness of 28 nm and is designed so that a concentration peak exists in Si. As a result, when a concentration peak is formed in the Si substrate, the charge distributed to the oxide film interface increases, and the sensitivity is lowered due to surface recombination. In FIG. 9, the peak range Rp is the average range of ions, and ΔRp is the average distribution of ions.

  In order to prevent this, the P-type diffusion layer 5 is designed to have a peak range Rp of impurities in the silicon oxide film 6 so that the concentration is uniformly reduced from the silicon surface in the substrate depth direction. The optical carriers generated by the light having a relatively short wavelength of about 300 to 450 nm absorbed in the vicinity of the surface are uniformly diffused to the deep side of the P-type silicon substrate 1 and diffused to the surface side. It can be prevented from disappearing due to recombination and a decrease in sensitivity.

  1 functions only as a color sensor, but it can also be used as an image sensor of a laminated light receiving element by arranging a plurality of light receiving elements 10 in a grid pattern.

  In the first embodiment, the photocurrent generated at each junction is detected by the photocurrent sensors S1 to S4, and these photocurrent signals are signal-processed by the arithmetic circuit 20 (shown in FIG. 1), so that the spectral sensitivity is increased. Calculated.

  The light receiving element 10 and the arithmetic circuit 20 constitute a light receiving device.

  FIG. 4A shows the result of calculating the spectral sensitivity by the arithmetic circuit 20 in the light receiving element 10 of the first embodiment of the present invention. In FIG. 4A, the horizontal axis represents wavelength [nm], and the vertical axis represents spectral sensitivity. From this calculation result, it was confirmed that the optical signal absorbed at the junction of each depth is output as an RGB (red, green, blue) signal.

  Here, in the normal diffusion method (FIG. 8), the behavior of the optical carrier is influenced by the built-in electric field based on the impurity concentration profile, and thus the sensitivity variation is the impurity concentration due to a plurality of parameters such as ion implantation energy and concentration and subsequent heat treatment. Sensitivity variation was large due to profile variation. In contrast, the light receiving element of the present invention has an impurity concentration peak, so that the sensitivity variation is uniformly determined only by the depth of the impurity concentration peak due to the ion implantation energy, and the parameters affecting the concentration distribution variation are reduced. As a result, variation in photosensitivity could be reduced.

  Further, by providing an impurity concentration peak at a predetermined position in the substrate depth direction, light can be collected at a necessary spectral junction such as blue or green, and sensitivity can be improved.

  In addition, by adopting a structure in which the concentration of the P-type diffusion layer 5 on the outermost surface decreases uniformly from the surface toward the substrate depth direction, the peak sensitivity of the blue spectrum can be shifted to the shorter wavelength side. it can.

  Also, by adding a quadruple diffusion that cuts infrared light, it is not necessary to cut infrared light by an IR cut filter or complicated calculation, and infrared light can be cut by a simple method. .

  In the first embodiment, the light receiving element by quadruple diffusion has been described. However, the number of diffusion superpositions is not limited to four, and the invention is applied to a light receiving element in which the number of diffusion superpositions is three or five or more. May be applied, and also in this case, there is an effect of reducing sensitivity variation.

  According to the light receiving element 10 having the above configuration, the impurity concentration peaks P1 and P2 (shown in FIG. 2) are formed at predetermined depths in the P-type diffusion layer 3 and the N-type diffusion layer 4, respectively. The impurity concentration peaks P1 and P2 suppress the flow of optical carriers from the second junction JN2 and the third junction JN3 to the P-type silicon substrate 1 side, thereby contributing to an improvement in sensitivity on the surface side than the impurity concentration peaks P1 and P2. At the same time, since the sensitivity is determined by the positions of the impurity concentration peaks P1 and P2, it is not necessary to consider the sensitivity variation due to the concentration gradient variation. Therefore, it is possible to realize a light receiving element that can reduce variation in sensitivity and that can be easily designed and can detect multiple colors at the same time with high sensitivity and high resolution.

  The impurity concentration peaks P1 and P2 are formed at a depth in the substrate depth direction corresponding to the penetration depth in the silicon with respect to light having a preset wavelength. The sensitivity of a desired wavelength can be enhanced by ignoring the effect of the optical carrier flowing from the junction to the substrate side.

  In addition, a P-type fourth diffusion layer (P) that forms a fourth junction JN4 at the interface with the third diffusion layer (N-type diffusion layer 4) in the third diffusion layer (N-type diffusion layer 4). By forming the mold diffusion layer 5), multi-color output can be achieved without lowering the resolution even when output of infrared light or the like is required in addition to general red, blue, and green.

  Further, since the impurity concentration peak is formed by performing the ion implantation in multiple stages, it is possible to make the impurity concentration peak at a predetermined depth.

  Further, since the impurity concentration profile of the fourth diffusion layer (P-type diffusion layer 5) formed on the most surface side becomes deeper in the substrate depth direction from the surface of the P-type silicon substrate 1, the impurity concentration decreases. The optical carriers generated in the vicinity do not move to the interface of the silicon oxide film 6 formed on the surface side, and a decrease in sensitivity of short wavelength light due to surface recombination can be suppressed.

  Further, it is possible to obtain color screen information by arranging a plurality of light receiving elements 10 capable of detecting multiple colors at the same time with high sensitivity and high resolution to obtain a plurality of color information.

  A light receiving device in which the light receiving elements 10 that function alone as a color sensor are arranged in a plurality of grids can be used as an image sensor.

  Further, by calculating the light intensity for each predetermined wavelength of the incident light incident on the light receiving element 10 by the arithmetic circuit 20, it is possible to reduce sensitivity variations and to simultaneously increase the sensitivity with high resolution and high resolution that can be easily designed. A light receiving device capable of detecting the light intensity of the color can be realized.

According to the arithmetic circuit 20, for example, by performing the following calculation, it is possible to reduce the half-value width of the spectral intensity of each color and improve the resolution.
Red photocurrent − Green photocurrent × K1 (constant)
Green photocurrent-Red photocurrent x K2 (constant)

In addition, in the light receiving element of the configuration of quadruple diffusion, infrared photocurrent is detected,
Red photocurrent-infrared photocurrent x K3 (constant)
By performing the calculation, the half-value width of the red spectrum can be reduced and the resolution can be improved.

  Further, in the light receiving element that performs the spectrum in the substrate depth direction, the long wavelength tail of the spectral intensity waveform of each color continues, and the wavelength resolution (half-value width of spectral intensity) does not become long. Therefore, in order to reduce the long-wavelength tail of the spectral intensity waveform, for example, as shown in FIG. 4B, the arithmetic circuit 20 multiplies the green photocurrent by X in the spectral intensity waveform of the blue photocurrent. The green light current spectral intensity waveform (shown by the alternate long and short dash line in FIG. 4B) is approximately aligned with the long wavelength tail (tail) of the blue photocurrent and then multiplied by X times. The resolution can be improved by subtracting the current from the blue photocurrent to reduce the component on the long wavelength side to obtain the spectral intensity waveform of the blue photocurrent indicated by the dotted line in FIG. 4B.

[Second Embodiment]
According to the light receiving element of the first embodiment, the light intensity output is calculated by the difference between the outputs from the respective diffusion layers sandwiching the junction. However, in order to obtain digital output, for example, according to some arithmetic circuits such as when using a ΔΣ circuit for AD conversion, in order to prevent variation due to calculation in the circuit of the photocurrent output at each junction, A technique is used in which the arithmetic circuit and the circuit layout are completely identical, and for example, three circuits for red, green, and blue are not fixed but are used interchangeably to prevent circuit variations. Since the photodiode is used with a reverse bias applied, the outputs from the N-type well region (N-type diffusion layer 4) and the N-type well region (N-type diffusion layer 2) in FIG. It becomes possible to obtain a positive output photocurrent, but the output from the P-type diffusion layer 5 and the P-type well region (P-type diffusion layer 3) becomes an output from the P-type semiconductor, and is a negative output. It becomes a photocurrent, and each signal processing circuit cannot be replaced and operated.

  A light-receiving device including the light-receiving element according to the second embodiment that solves such a problem will be described below with reference to FIG.

  In the light receiving device of the second embodiment, as shown in FIG. 5, the depth of each diffusion layer is the same as that of the first light receiving element 100 as in the first embodiment, but the polarity of each diffusion layer is the same. It is composed of two light receiving elements of the opposite second light receiving element 200.

  The first light receiving element 100 includes an N type diffusion layer 102 (first diffusion layer) formed in a P type silicon substrate 101 and a P type diffusion layer 103 (inside the N type diffusion layer 102). A second diffusion layer), an N-type diffusion layer 104 (third diffusion layer) formed inside the P-type diffusion layer 103, and a silicon oxide film 105 covering the entire surface of the P-type silicon substrate 101. The N-type diffusion layer 102 is formed so as to have an impurity concentration peak (region 111) at a predetermined depth. The P-type diffusion layer 103 is formed to have an impurity concentration peak (region 112) at a predetermined depth.

  The second light receiving element 200 includes an N type diffusion layer 202 (fourth diffusion layer) formed in the P type silicon substrate 101 and spaced from the first light receiving element 100, and an N type diffusion layer 202. P-type diffusion layer 203 (fifth diffusion layer) formed on the inner side, N-type diffusion layer 204 (sixth diffusion layer) formed on the inner side of the P-type diffusion layer 203, and N-type diffusion layer 204 And a P-type diffusion layer 205 (seventh diffusion layer) formed inside. The N-type diffusion layer 202 is formed to have an impurity concentration peak (region 211) at a predetermined depth. The P-type diffusion layer 203 is formed so as to have an impurity concentration peak (region 212) at a predetermined depth. The N-type diffusion layer 204 is formed to have an impurity concentration peak (region 213) at a predetermined depth.

  Thereby, the output terminal T1 and output terminal T3 of the light receiving element 100 of the second embodiment and the output terminal T2 in the light receiving element 200 are used, and the photocurrent can be extracted as a positive current output from the N-type diffusion layer. it can. As a result, red, green and blue photocurrent outputs can all be obtained with positive photocurrent output from the N-type semiconductor. Thus, as described above, in order to reduce the circuit error, the circuit for processing each signal can be used while being exchanged to reduce the circuit variation, which is effective in further reducing the sensitivity variation.

  According to the light receiving element of the second embodiment, although the polarities are different, the first junction JN101 and the fifth junction JN202 have the same depth in the substrate depth direction, and the second junction JN102 and the sixth junction JN203. And the third junction JN103 and the seventh junction JN204 have the same depth in the substrate depth direction, and the output terminals T1, T2, By detecting the photocurrent from the N-type semiconductor of T3, a positive photocurrent can be extracted from all the outputs of blue, green, and red.

  According to the light receiving element having the above-described configuration, it is possible to realize a light receiving element that can reduce sensitivity variation and can detect multiple colors at the same time with high sensitivity and high resolution that can be easily designed.

  Further, since the photocurrent output can be obtained from all N-type diffusion layers (or all P-type diffusion layers), any photocurrent output can obtain all plus (or all minus) currents, Since the arithmetic circuit provided in can be designed in exactly the same manner, it is not necessary to consider that each photocurrent output varies due to the circuit difference.

  In the light receiving device including the light receiving elements 100 and 200 according to the second embodiment, the light intensity may be calculated by an arithmetic circuit as in the first embodiment.

  In the second embodiment, the light receiving device including the first and second light receiving elements 100 and 200 has been described. However, the present invention may be applied to a light receiving device including three or more light receiving elements.

  Although specific embodiments of the present invention have been described, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present invention.

The light receiving element of this invention is
A substrate 1 of a first conductivity type,
A first diffusion layer 2 of a second conductivity type formed on the substrate 1 and forming a first junction at the interface with the substrate 1;
A second diffusion layer 3 of a first conductivity type formed on the first diffusion layer 2 and forming a second junction at the interface with the first diffusion layer 2;
A second diffusion layer 4 of a second conductivity type formed on the second diffusion layer 3 and forming a third junction at the interface with the second diffusion layer 3;
The first junction JN1, the second junction JN2, and the third junction JN3 are each formed at a depth set in advance in the substrate depth direction in order to detect light having a preset wavelength.
In the diffusion layer on the surface side of the substrate 1 of any one of the first junction JN1, the second junction JN2, and the third junction JN3, the impurity concentration is set to a depth set in advance in the substrate depth direction. A peak is formed.

  According to the above configuration, the impurity concentration peak is formed at a predetermined depth in the diffusion layer on the surface side of the substrate 1 of any one of the first junction JN1, the second junction JN2, and the third junction JN3. As a result, it is possible to suppress the optical carrier from flowing down from the junction to the substrate 1 side by this impurity concentration peak, contribute to the improvement of sensitivity on the surface side than the impurity concentration peak, and the sensitivity is determined by the position of the impurity concentration peak. There is no need to consider sensitivity variations due to concentration gradient variations. Therefore, it is possible to realize a light receiving element that can reduce variation in sensitivity and that can be easily designed and can detect multiple colors at the same time with high sensitivity and high resolution.

In the light receiving element of one embodiment,
The impurity concentration peak is formed at a depth in the substrate depth direction corresponding to a penetration depth in the substrate 1 with respect to light having a preset wavelength.

  According to the above embodiment, the impurity concentration peak is formed at a depth in the substrate depth direction corresponding to the penetration depth in the substrate 1 with respect to light having a preset wavelength. The sensitivity of a desired wavelength can be increased by ignoring the effect of the optical carrier flowing from the junction to the substrate 1 side due to the gradient.

In the light receiving element of one embodiment,
A fourth diffusion layer 5 of the first conductivity type formed on the third diffusion layer 4 and forming a fourth junction at the interface with the third diffusion layer 4 is provided.

  According to the above-described embodiment, multi-color output can be performed without reducing the resolution even when output of infrared light or the like is required in addition to general red, blue, and green.

In the light receiving element of one embodiment,
The impurity concentration peak was formed by performing ion implantation in multiple stages.

  According to the above embodiment, the impurity concentration peak is formed by performing ion implantation in multiple stages, so that the impurity concentration peak can be formed at a predetermined depth.

In the light receiving element of one embodiment,
The impurity concentration profile of the diffusion layer 5 formed on the most surface side of each of the diffusion layers 2, 3, 4, 5 decreases as the depth from the surface of the substrate 1 increases in the substrate depth direction.

According to the above embodiment, the impurity concentration profile of the diffusion layer 5 formed on the most surface side of each diffusion layer 2, 3, 4, 5 becomes deeper in the substrate depth direction from the surface of the substrate 1. Therefore, optical carriers generated near the surface do not move to, for example, the SiO ₂ interface formed on the surface side, and it is possible to suppress a decrease in sensitivity of short wavelength light due to surface recombination.

In the light receiving element of the present invention,
A first conductive type substrate 101;
A first diffusion layer 102 of a second conductivity type formed on the substrate 101 and forming a first junction JN101 at the interface with the substrate 101;
A first conductivity type second diffusion layer 103 formed on the first diffusion layer 102 and forming a second junction JN102 at the interface with the first diffusion layer 102;
A second conductivity type third diffusion layer 104 formed on the second diffusion layer 103 and forming a third junction JN103 at the interface with the second diffusion layer 103;
A second conductivity type fourth diffusion layer 202 formed on the substrate 101 to be separated from the first diffusion layer 102 and forming a fourth junction JN201 at the interface with the substrate 101;
A fifth diffusion layer 203 of a first conductivity type formed on the fourth diffusion layer 202 and forming a fifth junction JN202 at the interface with the fourth diffusion layer 202;
A second conductivity type sixth diffusion layer 204 formed on the fifth diffusion layer 203 and forming a sixth junction JN 203 at the interface with the fifth diffusion layer 203;
A second conductivity type seventh diffusion layer 205 formed on the sixth diffusion layer 204 and forming a seventh junction JN 204 at the interface with the sixth diffusion layer 204;
The first junction JN101 and the fifth junction JN202 have the same depth in the substrate depth direction, and
The second junction JN102 and the sixth junction JN203 have the same depth in the substrate depth direction, and
The depth of the third junction JN103 and the seventh junction JN204 in the substrate depth direction is the same,
In the diffusion layer on the surface side of the substrate 101 of any one of the first junction JN101, the second junction JN102, and the third junction JN103, the impurity concentration is set to a depth set in advance in the substrate depth direction. A peak is formed,
In the diffusion layer on the surface side of the substrate 101 of any one of the fifth junction JN202, the sixth junction JN203, and the seventh junction JN204, the impurity concentration is set to a depth set in advance in the substrate depth direction. A peak is formed.

  According to the above configuration, it is possible to realize the light receiving elements 100 and 200 that can reduce sensitivity variations and can easily detect multiple colors at the same time with high sensitivity and high resolution. Furthermore, since all the N-type diffusion layers (or all P-type diffusion layers) can obtain photocurrent output, any photocurrent output can obtain all plus (or all minus) current, Since the arithmetic circuit provided in the subsequent stage can be designed in exactly the same manner, it is not necessary to consider that each photocurrent output varies due to the difference in the circuit.

In the light receiving device of the present invention,
A plurality of the light receiving elements 10 described above are arranged.

  According to the above configuration, color screen information can be obtained by arranging a plurality of light receiving elements 10 capable of simultaneously detecting multiple colors with high sensitivity and high resolution that can reduce sensitivity variation and can be easily designed, thereby obtaining a plurality of color information. Can be obtained.

In the light receiving device of one embodiment,
The plurality of light receiving elements 10 are arranged in a grid pattern.

  According to the embodiment described above, the light receiving elements 10 that function alone as a color sensor can be used as an image sensor by arranging them in a plurality of grids.

In the light receiving device of the present invention,
Any one of the light receiving elements described above;
Based on at least photocurrents from the first to third diffusion layers 102 to 104 obtained by incident light incident on the plurality of light receiving elements 10, the light intensity for the predetermined wavelength of the incident light is determined. And an arithmetic circuit 20 for calculating.

  According to the above configuration, the light intensity for each predetermined wavelength of the incident light incident on the light receiving element 10 is calculated by the arithmetic circuit 20, whereby sensitivity variation can be reduced, design is easy, high sensitivity, and high sensitivity. It is possible to realize a light receiving device capable of detecting multiple colors at the same time with resolution.

DESCRIPTION OF SYMBOLS 1 ... P-type silicon substrate 2 ... N-type diffusion layer 3 ... P-type diffusion layer 4 ... N-type diffusion layer 5 ... P-type diffusion layer 6 ... Silicon oxide film 10 ... Light receiving element 20 ... Arithmetic circuit 100 ... First light receiving element DESCRIPTION OF SYMBOLS 101 ... P type silicon substrate 102 ... N type diffusion layer 103 ... P type diffusion layer 104 ... N type diffusion layer 105 ... Silicon oxide film 200 ... Second light receiving element 202 ... N type diffusion layer 203 ... P type diffusion layer 204 ... N-type diffusion layer 205 ... P-type diffusion layer JN1, JN101 ... First junction JN2, JN102 ... Second junction JN3, JN103 ... Third junction JN4 ... Fourth junction JN201 ... Fourth junction JN202 ... Fifth junction JN203 ... Sixth Junction JN204 ... seventh junction S1-S4 ... photocurrent sensor

Claims (5)

A first conductivity type substrate;
A first diffusion layer of a second conductivity type formed on the substrate and forming a first junction at an interface with the substrate;
A second diffusion layer of a first conductivity type formed on the first diffusion layer and forming a second junction at the interface with the first diffusion layer;
A third diffusion layer of a second conductivity type formed on the second diffusion layer and forming a third junction at the interface with the second diffusion layer;
The first junction, the second junction, and the third junction are each formed at a preset depth in the substrate depth direction in order to detect light having a preset wavelength,
An impurity concentration peak is formed at a predetermined depth in the substrate depth direction in the diffusion layer on the substrate surface side of any one of the first junction, the second junction, and the third junction. A light receiving element characterized by comprising: The light receiving element according to claim 1,
The light-receiving element, wherein the impurity concentration peak is formed at a depth in a substrate depth direction corresponding to a penetration depth in the substrate with respect to light having a preset wavelength. In the light receiving element according to claim 1 or 2,
A light receiving element comprising: a fourth diffusion layer of a first conductivity type formed on the third diffusion layer and forming a fourth junction at an interface with the third diffusion layer. In the light receiving element according to any one of claims 1 to 3,
The light receiving element, wherein the impurity concentration profile of the diffusion layer formed on the most surface side among the diffusion layers is such that the impurity concentration decreases as the depth from the surface of the substrate increases in the substrate depth direction. A first conductivity type substrate;
A first diffusion layer of a second conductivity type formed on the substrate and forming a first junction at an interface with the substrate;
A second diffusion layer of a first conductivity type formed on the first diffusion layer and forming a second junction at the interface with the first diffusion layer;
A third diffusion layer of a second conductivity type formed on the second diffusion layer and forming a third junction at the interface with the second diffusion layer;
A second diffusion layer of a second conductivity type formed on the substrate apart from the first diffusion layer and forming a fourth junction at the interface with the substrate;
A fifth diffusion layer of a first conductivity type formed on the fourth diffusion layer and forming a fifth junction at an interface with the fourth diffusion layer;
A sixth diffusion layer of a second conductivity type formed on the fifth diffusion layer and forming a sixth junction at an interface with the fifth diffusion layer;
A second conductivity type seventh diffusion layer formed on the sixth diffusion layer and forming a seventh junction at an interface with the sixth diffusion layer;
The depth in the substrate depth direction of the first bond and the fifth bond is the same, and
The depth of the second junction and the sixth junction in the substrate depth direction is the same, and
The depth in the substrate depth direction of the third junction and the seventh junction is the same,
An impurity concentration peak is formed at a predetermined depth in the substrate depth direction in the diffusion layer on the substrate surface side of any one of the first junction, the second junction, and the third junction. And
In the diffusion layer on the substrate surface side of any one of the fifth junction, the sixth junction, and the seventh junction, an impurity concentration peak is formed at a depth set in advance in the substrate depth direction. A light receiving element characterized by comprising:

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