JP2015005699A - Imaging apparatus and imaging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sensitivity to light having a long wavelength.SOLUTION: An imaging device of an embodiment includes first and second semiconductor regions having a first conductivity type. Each of the first and second semiconductor regions collects or accumulates charges generated by photoelectric conversion. A first color filter allowing light in a first wavelength band to be transmitted therethrough is disposed corresponding to the first semiconductor region. A second color filter allowing light in a second wavelength band to be transmitted therethrough is disposed corresponding to the second semiconductor region. The second wavelength band includes a wavelength band on a shorter wavelength side than the first wavelength band. In the imaging device of an embodiment, charges generated by light transmitting through the first color filter are collected in the first semiconductor region. Charges generated by short wavelength light among light transmitting through the second color filter are collected in the second semiconductor region, and a part of charges generated by long wavelength light is collected in the first semiconductor region.

Description

  The present invention relates to an imaging device and an imaging system.

  The imaging device disclosed in Patent Document 1 is configured so that one pixel can detect light of a plurality of colors. Specifically, a plurality of photoelectric conversion units are stacked in one pixel. Since such a configuration eliminates the need for a color filter, it is said that a decrease in sensitivity due to the color filter can be reduced.

JP2003-298038

  In general, most of photoelectric conversion by light having a short wavelength occurs in a relatively shallow region of a semiconductor substrate. On the other hand, photoelectric conversion by light having a long wavelength can occur in a wide region extending from a position close to the surface of the semiconductor substrate to a certain depth.

  In the pixel structure described in Patent Document 1, most of the charges generated by light having a short wavelength are accumulated in a corresponding photoelectric conversion unit. On the other hand, part of the charge generated by light having a long wavelength may be accumulated in a photoelectric conversion unit corresponding to light having a short wavelength, which is disposed at a shallower position. Therefore, the sensitivity of light having a long wavelength may be relatively lowered with respect to the sensitivity of light having a short wavelength.

  In view of such a problem, the present inventor discloses a technique for improving sensitivity to light having a long wavelength in an imaging apparatus.

  An imaging apparatus according to an embodiment of one aspect of the present invention includes a semiconductor substrate, a first semiconductor region of a first conductivity type that is disposed on the semiconductor substrate and collects or accumulates charges generated by photoelectric conversion. A first conductive type second semiconductor region disposed on the semiconductor substrate for collecting or accumulating charges generated by photoelectric conversion; and a first wavelength band disposed on the first semiconductor region. A first color filter that transmits light of the first wavelength and the second semiconductor region, and transmits light of a second wavelength band including a wavelength band on a short wavelength side with respect to the first wavelength band A second color filter to be formed; a third semiconductor region of a second conductivity type disposed under the first semiconductor region; and the third semiconductor under the second semiconductor region. It is placed at a position shallower than the area, and the charge generated by photoelectric conversion Between the fourth semiconductor region of the second conductivity type functioning as a potential barrier, the first semiconductor region, and the second semiconductor region, and at a position shallower than the fourth semiconductor region. An isolation portion disposed, and by photoelectric conversion in at least a part of a region below the isolation portion and shallower than the third semiconductor region and deeper than the fourth semiconductor region. A potential for the generated charge is lower than that of the separation portion and the fourth semiconductor region.

  An imaging apparatus according to an embodiment of another aspect of the present invention includes a semiconductor substrate, a first semiconductor region of a first conductivity type that is disposed on the semiconductor substrate and collects or accumulates charges generated by photoelectric conversion. A first conductive type second semiconductor region disposed on the semiconductor substrate for collecting or accumulating charges generated by photoelectric conversion; and a first wavelength band disposed on the first semiconductor region. A first color filter that transmits light of the second wavelength region, a second color filter that is disposed with respect to the second semiconductor region and transmits light of a second wavelength band, and under the first semiconductor region A third semiconductor region of a second conductivity type disposed, and a potential barrier against charges generated by photoelectric conversion, disposed below the second semiconductor region and at a position shallower than the third semiconductor region. Second conductivity type that functions as A separation portion disposed between the fourth semiconductor region, the first semiconductor region, and the second semiconductor region and disposed at a shallower position than the fourth semiconductor region, and The first wavelength band includes a wavelength band on a long wavelength side with respect to the second wavelength band, is below the separation unit, and is shallower than the third semiconductor region, and the fourth wavelength band A potential for charges generated by photoelectric conversion in at least a part of a region deeper than the semiconductor region is lower than that of the separation portion and the fourth semiconductor region.

  According to the present invention, sensitivity to light having a long wavelength can be improved.

The figure which shows typically the planar structure of an imaging device. The figure which shows typically the cross-section of an imaging device. The figure which shows typically the planar structure of an imaging device. The figure which shows typically the planar structure of an imaging device. The figure which shows typically the planar structure of an imaging device. The figure which shows typically the cross-section of an imaging device. The figure which shows typically the cross-section of an imaging device. The block diagram of the Example of an imaging system. The figure which shows the characteristic of a color filter typically.

  One embodiment according to the present invention is an imaging apparatus. The imaging device includes first and second semiconductor regions of the first conductivity type. The first semiconductor region collects or accumulates charges generated by photoelectric conversion. The second semiconductor region collects or accumulates charges generated by photoelectric conversion.

  Corresponding to the first semiconductor region, a first color filter that transmits light in the first wavelength band is disposed. Corresponding to the second semiconductor region, a second color filter that transmits light in the second wavelength band is disposed.

  FIG. 9 schematically shows the relationship between the first wavelength band and the second wavelength band. In each of FIGS. 9A to 9D, the horizontal axis indicates the wavelength. The first color filter transmits light in the first wavelength band 901. The second color filter transmits light in the second wavelength band 902.

  In some embodiments, as shown in FIGS. 9A, 9 </ b> B, and 9 </ b> D, the second wavelength band 902 includes a wavelength band shorter than the first wavelength band 901. That is, the second color filter transmits light having a shorter wavelength than the first wavelength band 901. Alternatively, in some other embodiments, as illustrated in FIGS. 9A, 9 </ b> C, and 9 </ b> D, the first wavelength band 901 has a longer wavelength side than the second wavelength band 902. Includes wavelength band. That is, the first color filter transmits light having a wavelength longer than that of the second wavelength band 902.

  As shown in FIGS. 9B, 9C, and 9D, the first wavelength band 901 and the second wavelength band 902 may partially overlap. That is, when the first color filter transmits light in a certain wavelength band, the second color filter may transmit light in the same wavelength band.

  Here, the fact that the color filter transmits light of a certain wavelength means that an amount of light larger than a predetermined ratio among the light incident on the color filter passes through the color filter. It is not necessary for all incident light to pass through. The predetermined ratio can be set as appropriate according to the spectral characteristics of the imaging apparatus.

  An imaging device usually includes a plurality of pixels each including a photoelectric conversion unit. The first and second semiconductor regions are each included in one of the photoelectric conversion units. Therefore, in this specification, a pixel including the first semiconductor region in which the first color filter is arranged is referred to as a first pixel for convenience. A pixel including the second semiconductor region in which the second color filter is arranged is referred to as a second pixel for convenience.

  In the imaging device according to the present embodiment, charges generated by the light transmitted through the first color filter are collected or accumulated in the first semiconductor region. Then, among the light transmitted through the second color filter, the charges generated by the light having a short wavelength are collected or accumulated in the second semiconductor region, and at least the charges generated by the light having a longer wavelength than this are collected. A part is collected or accumulated in the first semiconductor region. Therefore, in the first semiconductor region, both the charge generated by the light transmitted through the first color filter and the charge generated by the light transmitted through the second color filter are collected or accumulated. . As described above, by distributing charges generated by light transmitted through one color filter to two or more semiconductor regions, sensitivity to light having a long wavelength can be improved.

  Several embodiments will be described below with reference to the drawings. In the following examples, the signal charge is an electron. Therefore, the first conductivity type is N type, and the second conductivity type is P type. However, the signal charge may be a hole. When the signal charge is a hole, the first conductivity type is P-type and the second conductivity type is N-type.

  In this specification, the expression “deep” or “shallow” is used when referring to the relationship between two semiconductor regions with respect to the distance along the direction perpendicular to the surface of the semiconductor substrate. . The expression “upper” or “lower” is used to imply that orthogonal projections of two semiconductor regions onto a plane parallel to the surface of the semiconductor substrate overlap. In other words, the expression “the first semiconductor region is on the second semiconductor region” means that the first semiconductor region is at a position shallower than the second semiconductor region, and the first and second This means that the orthogonal projections of the two semiconductor regions onto a plane parallel to the surface of the semiconductor substrate overlap each other. A position closer to the surface on the light incident side of the semiconductor substrate is defined as “shallow” or “upper”. The surface on the light incident side of the semiconductor substrate is an interface between the semiconductor substrate and the insulator disposed thereon at the position where the photoelectric conversion unit is disposed. In FIG. 2, the surface SR of the semiconductor substrate is illustrated.

  The imaging apparatus according to the first embodiment will be described with reference to FIGS. FIG. 1 schematically shows a planar structure of the imaging apparatus. FIG. 1 shows four pixels 1 to 4 arranged in 2 rows and 2 columns. In practice, the imaging device includes more pixels. FIG. 2 schematically shows a cross-sectional structure along the line AB in FIG. In FIG. 2, the same parts as those in FIG. In the present embodiment, the pixel 1 and the pixel 2 shown in FIG. 2 are the first pixel and the second pixel, respectively.

  As shown in FIG. 1, each pixel includes a charge accumulation region 5, a floating diffusion portion (hereinafter referred to as FD portion) 6, and a transfer gate electrode 7. In the pixel circuit region 8, transistors that constitute a pixel circuit are arranged. The pixel circuit region 8 may be provided with a contact region for supplying a predetermined voltage to the pixel well. The charge storage region 5 and the FD unit 6 of one pixel are electrically separated from the charge storage region 5 of another pixel, the FD unit 6 or the pixel circuit region by the separation unit 20. .

  In addition, in order to distinguish the member contained in a different pixel, the code | symbol which consists of a number and an alphabet is attached | subjected. The pixel 1 includes a charge accumulation region 5a, an FD portion 6a, and a transfer gate electrode 7a. The pixel 2 includes a charge storage region 5b, an FD portion 6b, and a transfer gate electrode 7b. When it is not necessary to distinguish these members for each pixel, the alphabet is omitted. The same applies to the subsequent drawings.

  Each of the four pixels 1 to 4 is provided with a color filter that transmits light of a predetermined wavelength band. Specifically, the pixel 1 and the pixel 4 are provided with a color filter that transmits light in the green wavelength band. The pixel 2 is provided with a color filter that transmits light in a blue wavelength band. The pixel 3 is provided with a color filter that transmits light in the red wavelength band.

  The blue wavelength band includes a wavelength band on a shorter wavelength side than the green wavelength band and the red wavelength band. In other words, the blue color filter sufficiently transmits light in a wavelength band shorter than the red or green wavelength band. On the other hand, the red and green color filters hardly transmit light in the wavelength band on the short wavelength side.

  Further, the green wavelength band includes a wavelength band on the shorter wavelength side than the red wavelength band. In other words, the green color filter sufficiently transmits light in a wavelength band shorter than the red wavelength band. On the other hand, the red color filter hardly transmits light in the wavelength band on the short wavelength side.

  As shown in FIG. 2, the imaging device includes an N-type semiconductor substrate 9. In FIG. 2, the surface SR of the semiconductor substrate is shown. A semiconductor region for forming a photoelectric conversion unit, a separation unit, a transistor, and the like is formed on the semiconductor substrate 9.

  The charge storage region 5a included in the first pixel 1 and the charge storage region 5b included in the second pixel 2 are both N-type semiconductor regions. The charge storage region 5a is included in the first photoelectric conversion unit 50a, and the charge storage region 5b is included in the second photoelectric conversion unit 50b. The photoelectric conversion unit 50 is, for example, a photodiode. Charges generated by photoelectric conversion are collected or accumulated in the charge accumulation regions 5a and 5b.

  The FD portion 6 is an N-type semiconductor region. The FD unit 6 is connected to the amplifying unit through a contact plug (not shown). Alternatively, the FD unit 6 may constitute an input node of the amplification unit. The amplifying unit outputs a signal corresponding to the potential of the FD unit 6. A transfer gate electrode 7 is disposed on the region between the charge storage region 5 and the FD portion 6 via an insulating film (not shown). The transfer gate electrode 7 transfers the charge in the charge storage region 5 to the FD unit 6. As shown in FIG. 2, a part of the charge storage region 5 may be disposed under the transfer gate electrode 7. In each pixel, the surface region 10 is disposed on the charge accumulation region 5. The surface region 10 is a P-type semiconductor region. The surface region 10 forms a PN junction with the charge storage region 5. The surface region 10 can suppress dark current generated at the interface SR of the semiconductor substrate 9.

  A separation unit 20 is disposed between the plurality of charge storage regions 5. The separation unit 20 electrically separates the plurality of charge accumulation regions 5 from each other. Separating portion 20 disposed between charge storage regions 5 a and 5 b includes insulator region 11 and P-type semiconductor region 16 disposed under insulator region 11. The separation unit 20 disposed between the charge accumulation region 5a of the first pixel 1 and the charge accumulation region of another pixel (not illustrated) includes an insulator region 11 and a plurality of portions disposed below the insulator region 11. P-type semiconductor regions 16-18. The separation unit 20 disposed between the charge accumulation region 5b of the second pixel 2 and the charge accumulation region of another pixel (not shown) includes an insulator region 11 and a plurality of portions disposed below the insulator region 11. P-type semiconductor regions 16 and 18. The insulator region 11 is LOCOS (LOCal Oxidation of Silicon) or STI (Shallow Trench Isolation). The insulator region 11 is provided as necessary and may be omitted. When the insulator region 11 is omitted, the separation unit 20 is configured by PN junction separation.

  A first color filter 30 a is disposed on the charge accumulation region 5 a of the first pixel 1. A second color filter 30b is disposed on the charge storage region 5b of the second pixel 2. The first color filter 30a transmits light in the first wavelength band. The second color filter 30b transmits light in the second wavelength band including the wavelength band shorter than the first wavelength band. In the present embodiment, the first color filter 30a transmits light in the green wavelength band. The second color filter 30b transmits light in the blue wavelength band. Usually, the blue wavelength band is shorter than the green wavelength band. Of course, a part of the blue wavelength band may overlap with the green wavelength band.

  A first buried layer 14 is disposed under the charge accumulation region 5 a of the first pixel 1. The first buried layer 14 is a P-type semiconductor region. The first buried layer 14 may function as a potential barrier against charges generated by photoelectric conversion. The first buried layer 14 extends to below the charge storage region 5b of the second pixel 2. A part of the first buried layer 14 may be included in the separation unit 20. In other words, the first buried layer 14 may extend under the insulator region 11 of the separation portion 20. In some other embodiments, the first buried layer 14 does not extend below the charge storage region 5 b of the second pixel 2.

  A second buried layer 15 is disposed under the charge accumulation region 5 b of the second pixel 2. The second buried layer 15 is a P-type semiconductor region. The second embedded layer 15 functions as a potential barrier against charges generated by photoelectric conversion. The second buried layer 15 is disposed at a position shallower than the first buried layer 14. When the first buried layer 14 extends to below the charge storage region 5b, the second buried layer 15 is disposed on a part of the first buried layer 14. . In addition, a part of the second buried layer 15 may be included in the separation unit 20. In other words, the second buried layer 15 may extend under the insulator region 11 of the separation portion 20. The second buried layer 15 is not disposed under at least a part of the charge storage region 5a.

  Note that the second buried layer 15 can be formed by the same process as the P-type semiconductor region 17 of the separation portion. For example, the second buried layer 15 and the P-type semiconductor region 17 can be formed by ion implantation. At this time, a mask having an opening corresponding to a position where the second buried layer 15 and the P-type semiconductor region 17 are to be disposed is used.

  A first photoelectric conversion region 12 is disposed between the charge storage region 5 a of the first pixel 1 and the first buried layer 14. In the present embodiment, the first photoelectric conversion region 12 is an N-type semiconductor region. In this case, the first photoelectric conversion region 12 and the first buried layer 14 constitute a PN junction. In addition, two portions of the N-type semiconductor regions that are continuously arranged and having different impurity concentrations are distinguished as the charge storage region 5a and the first photoelectric conversion region 12. For example, the impurity concentration of the first photoelectric conversion region 12 may be lower than the impurity concentration of the charge storage region 5a.

  Alternatively, in some other embodiments, the first photoelectric conversion region 12 is a P-type semiconductor region, and more impurity than the first and second buried layers 14 and 15. The concentration is low. In this case, the first photoelectric conversion region 12 and the charge storage region 5a constitute a PN junction.

  A second photoelectric conversion region 13 is disposed between the charge storage region 5 b of the second pixel 2 and the second buried layer 15. In the present embodiment, the second photoelectric conversion region 13 is an N-type semiconductor region. In this case, the second photoelectric conversion region 13 and the second buried layer 15 constitute a PN junction. In addition, two portions of the N-type semiconductor regions that are continuously arranged and having different impurity concentrations are distinguished from each other as the charge accumulation region 5 b and the second photoelectric conversion region 13. For example, the impurity concentration of the second photoelectric conversion region 13 may be lower than the impurity concentration of the charge storage region 5b.

  Alternatively, in some other embodiments, the second photoelectric conversion region 13 is a P-type semiconductor region and has an impurity concentration lower than that of the second buried layer 15. In this case, the second photoelectric conversion region 13 and the charge storage region 5b constitute a PN junction.

  The charges generated in the first and second photoelectric conversion regions 12 and 13 are collected or accumulated in the charge accumulation regions 5a and 5b, respectively. Therefore, the first and second photoelectric conversion regions 12 and 13 can read out charges generated at a deep position on the substrate as signal components. The first photoelectric conversion unit 50 a includes a part of the first photoelectric conversion region 12. The second photoelectric conversion unit 50 b includes a part of the second photoelectric conversion region and the second photoelectric conversion region 13.

  The structure of the separation part 20 arranged between the charge storage region 5a and the charge storage region 5b will be described. The separation unit 20 is disposed at a position shallower than the second buried layer 15. Specifically, the insulator region 11 and the P-type semiconductor region 16 are disposed at a position shallower than the second buried layer 15.

  Below the separation portion 20 disposed between the charge storage region 5a and the charge storage region 5b, at a position shallower than the first buried layer 14 and deeper than the second buried layer 15, One photoelectric conversion region 12 is arranged. The first photoelectric conversion region 12 is an N-type semiconductor region or a P-type semiconductor region having an impurity concentration lower than that of the second buried layer 15. When the first photoelectric conversion region 12 is a P-type semiconductor region, the impurity concentration of the P-type semiconductor region 16 is higher than the impurity concentration of the first photoelectric conversion region 12.

  Therefore, the potential of the first photoelectric conversion region 12 is lower than the potential of the P-type semiconductor region 16 and the potential of the second buried layer 15. The potential here is signal charge, that is, electrostatic energy for electrons.

  With such a configuration, among the charges generated by the light transmitted through the second color filter 30b, the charges generated in the region below the second buried layer 15 are transferred to the charge storage region 5a of the first pixel 1. Collected or accumulated. Of the light transmitted through the second color filter 30 b, light having a relatively long wavelength is likely to be photoelectrically converted in a region below the second buried layer 15. Therefore, charges generated by light having a relatively long wavelength can be collected or stored in the charge storage region 5a. As a result, the sensitivity to light having a long wavelength can be improved.

  When there is the potential relationship described above, the first photoelectric conversion region 12 may not extend below the charge accumulation region 5b. For example, the first photoelectric conversion region 12 is an N-type semiconductor region, and a P-type layer is interposed between a portion disposed under the charge storage region 5a and a portion disposed under the charge storage region 5b. The semiconductor region may be arranged. Since the impurity concentration of the P-type semiconductor region is lower than the impurity concentration of the second buried layer 15, the above-described sensitivity improvement effect can be obtained.

  As another aspect of the present embodiment, the first photoelectric conversion region 12 is a P-type semiconductor region and extends from the lower end of the charge storage region 5a to a region below the second buried layer 15. It extends to. In this case, the lower end of the charge storage region 5 a is a PN junction surface between the charge storage region 5 a and the first photoelectric conversion region 12.

  In still another aspect, the first photoelectric conversion region 12 is an N-type semiconductor region. An N-type semiconductor region continues from the charge storage region 5a to a region below the second buried layer 15. In this case, two portions of the continuous N-type semiconductor region having different impurity concentrations are distinguished as the charge storage region 5a and the first photoelectric conversion region 12.

  With such a configuration, among the charges generated by the light transmitted through the second color filter 30b, the charges generated in the region below the second buried layer 15 are transferred to the charge storage region 5a of the first pixel 1. Collected or accumulated. Of the light transmitted through the second color filter 30 b, light having a relatively long wavelength is likely to be photoelectrically converted in a region below the second buried layer 15. Therefore, charges generated by light having a relatively long wavelength can be collected or stored in the charge storage region 5a. As a result, the sensitivity to light having a long wavelength can be improved.

  The effect of the present embodiment will be described with specific numerical examples. In addition to the light in the blue wavelength band, the light in the green wavelength band also enters the photoelectric conversion unit 50b of the second pixel 2. This is because, for example, even if the color filter 30b disposed in the second pixel 2 is blue, part of the light in the green wavelength band is transmitted through the color filter 30b. Alternatively, the color filter 30b of the second pixel 2 may be a color that transmits light of cyan, that is, blue and green wavelength bands. Here, it is assumed that the depth of the second buried layer 15 is 1 micrometer. The light in the blue wavelength band incident on the second pixel 2 is mainly photoelectrically converted in the second photoelectric conversion region 13, and the generated charges are stored in the charge storage region 5b. On the other hand, about half of the light in the green wavelength band is photoelectrically converted in the first photoelectric conversion region 12. The charges generated in the first photoelectric conversion region 12 do not go to the charge storage region 5b but are stored in the charge storage region 5a of the first pixel 1 by the potential barrier formed by the second buried layer 15. In this way, the charge generated by the light in the green wavelength band in the second pixel 2 is accumulated in the charge accumulation region 5 a of the first pixel 1. Therefore, the sensitivity to light in the green wavelength band can be increased.

  In particular, when a cyan color filter is arranged on the second pixel 2, the sensitivity to light in the green wavelength band is about 1.5 times that in the case where there is no charge contribution from the second pixel 2. can do. In this case, since the signal of the second pixel 2 also includes a charge component generated by light in the green wavelength band, it may be corrected by signal processing.

  When a blue color filter is disposed on the second pixel 2, high color separation characteristics can be obtained without performing such correction. When a blue color filter is used for the second pixel 2, the blue color filter may be made thinner than the color filters of other colors in order to further improve the sensitivity to light in the green wavelength band. This is because if the blue color filter is thinned, light in the green wavelength band is easily transmitted.

  The numerical values given here are merely examples. The degree of the effect can vary depending on the spectral characteristics of the color filter and the depth of the second embedded layer 15.

  In the present embodiment, the potential of the second photoelectric conversion region 13 is lower than the potential of the second buried layer 15 and the potential of the P-type semiconductor region 16. According to such a configuration, among the charges generated by the light transmitted through the second color filter 30b, the charges generated in the region above the second buried layer 15 are efficiently collected in the charge storage region 5b. Or can be accumulated. That is, the sensitivity to light with a short wavelength can be improved. Further, as shown in FIG. 2, the insulator region 11, the P-type semiconductor region 16, and the second buried layer 15 are arranged so as to surround the charge storage region 5 b of the second pixel 2. Thus, the effect of improving the sensitivity to light having a short wavelength becomes more remarkable. Of course, the effect can be obtained even if the potential of the second photoelectric conversion region 13 is higher than the potential of the second buried layer 15 and the potential of the P-type semiconductor region 16.

  Note that the P-type semiconductor region 16 and the second buried layer 15 may be continuous. Alternatively, as shown in FIG. 2, the P-type semiconductor region 16 and the second buried layer 15 may be separated from each other. In this case, the region between the P-type semiconductor region 16 and the second buried layer 15 is preferably depleted.

  The plurality of P-type semiconductor regions 16 to 18 may be continuous along the depth direction of the semiconductor substrate. Alternatively, as shown in FIG. 2, the plurality of P-type semiconductor regions 16 to 18 may be separated from each other. The P-type semiconductor region 18 disposed at the deepest position may be continuous with the first buried layer 14.

  In this embodiment, the first pixel 1 is provided with a color filter that transmits light in the green wavelength band, and the second pixel 2 is provided with a color filter that transmits light in the blue wavelength band. However, the combination of the color filters arranged in the first pixel 1 and the second pixel 2 is not limited to the above example. The color filter of the second pixel 2 only needs to have a characteristic of transmitting light in the wavelength band on the short wavelength side with respect to the wavelength band mainly transmitted by the color filter of the first pixel 1. Alternatively, the wavelength band mainly transmitted by the color filter of the first pixel 1 only needs to include the wavelength band on the long wavelength side with respect to the wavelength band mainly transmitted by the color filter of the second pixel 2. .

  Some specific examples are shown below. For example, when a red color filter is disposed on the first pixel 1, color filters such as green, blue, cyan, magenta, and yellow can be disposed on the second pixel 2. When a green color filter is disposed on the first pixel 1, a color filter such as blue, cyan, magenta, or the like can be disposed on the second pixel 2. In the case where a magenta color filter is disposed on the first pixel 1, color filters such as green, blue, and cyan can be disposed on the second pixel 2. Further, when a cyan color filter is disposed on the first pixel 1, a blue color filter may be disposed on the second pixel 2. Also, a white color filter may be used for either the first pixel 1 or the second pixel 2. By designing the depth of the second buried layer 15 according to the spectral characteristics of the color filter, it is possible to obtain the effect of improving the sensitivity more remarkably.

  In this embodiment, part of the charge generated by the light transmitted through the second color filter 30b is collected or accumulated in the charge accumulation region 5a of the first pixel 1. When the color filters are arranged in a Bayer array, green color filters are arranged on the four pixels around the second pixel 2. Of these four pixels, two or more pixels may have a structure in which charges generated by light transmitted through the second color filter 30b are collected or accumulated.

  This embodiment is an APS (Active Pixel Sensor) type imaging apparatus. Another embodiment may be a CCD type imaging device. In that case, the FD section 6 of FIG. 2 is configured as a transfer channel of the vertical CCD.

  In the present embodiment, the first buried layer 14 is disposed under the charge accumulation region 5 a of the first pixel 1. In some other embodiments, the first buried layer 14 may be omitted, and the first photoelectric conversion region 12 may extend to a deep portion of the semiconductor substrate. Light having a long wavelength easily enters a deep position on the semiconductor substrate. Therefore, with such a configuration, the sensitivity to light with a long wavelength can be further improved. On the other hand, by providing the first buried layer 14, it is possible to reduce the charge generated in the deep part of the semiconductor substrate from being mixed into the charge storage region 5a. That is, crosstalk can be reduced.

  Another embodiment will be described. In the present embodiment, the arrangement of the first pixel and the second pixel is different from that in the first embodiment. Therefore, only differences from the first embodiment will be described, and description of the same parts as those of the first embodiment will be omitted.

  FIG. 3 schematically shows a planar structure of the imaging apparatus. In FIG. 3, the boundary between pixels is indicated by a dotted line. The pixel 1 and the pixel 4 are provided with a green color filter. The pixel 3 is provided with a red color filter. The pixel 2 is provided with a magenta color filter that transmits light in the blue and red wavelength bands. In this embodiment, the pixel 3 is a first pixel and the pixel 2 is a second pixel.

  In the present embodiment, the first buried layer 14 extends under the charge storage region 5 of all pixels. The second buried layer 15 is disposed under the charge accumulation region 5 b of the pixel 2. The insulator region 11 and the P-type semiconductor region 16 are arranged along the boundary line of the pixel. Therefore, as in the first embodiment, the charge storage region 5 b of the pixel 2 is surrounded by the insulator region 11, the P-type semiconductor region 16, and the second buried layer 15. Therefore, the charges generated by the light in the blue wavelength band incident on the pixel 2 are collected or accumulated in the charge accumulation region 5b.

  In FIG. 3, a P-type semiconductor region 18 included in the separation unit 20 is disposed in a hatched region. The P-type semiconductor region 18 is disposed deeper than the second buried layer 15. As shown in FIG. 3, the P-type semiconductor region 18 is disposed so as to surround the charge storage region 5a of the pixel 1 when viewed in plan. Further, the P-type semiconductor region 18 is disposed so as to surround the charge storage region 5d of the pixel 4 when viewed in plan.

  A P-type semiconductor region 18 is not disposed between the pixel 2 and the pixel 3. The first photoelectric conversion region 12 disposed below the charge accumulation region 5 c of the pixel 3 extends to a region below the second buried layer 15 of the pixel 2. Therefore, the charges generated by the light in the red wavelength band incident on the pixel 2 are collected or accumulated in the charge accumulation region 5b.

  A cross-sectional structure along A'-B 'in FIG. 3 is schematically shown in FIG. However, in FIG. 2, the portion indicated as the pixel 1 is a portion included in the pixel 3 in this embodiment. Therefore, as long as this embodiment is described, the letter a in FIG. 2 is replaced with letter c. For example, the color filter 30a in FIG. 2 is a red color filter 30c in the description of this embodiment.

  Thus, by changing the arrangement of the P-type semiconductor region 18 disposed deeper than the second buried layer 15, the first pixel (pixel 3 in this embodiment) and the second pixel The combination with (pixel 2 in this embodiment) can be changed.

  Another embodiment will be described. The difference from the first and second embodiments is that microlenses having different sizes are arranged for each pixel. Therefore, only differences from the first embodiment and the second embodiment will be described, and the description of the same parts as the first embodiment or the second embodiment will be omitted.

  FIG. 4 schematically shows a planar structure of the imaging device. Specifically, the layout of pixels and microlenses is shown. In FIG. 4, the boundary between pixels is indicated by a dotted line. In FIG. 4, the boundary between the microlenses is indicated by a solid line. However, since the boundary between the pixels is the same as that in FIG. 3, the portion where the boundary between the pixels and the boundary between the microlenses coincide is indicated by a solid line.

  The pixel 1 and the pixel 4 are provided with a color filter that transmits light in the green wavelength band. The pixel 3 is provided with a color filter that transmits light in the red wavelength band. The pixel 2 is provided with a magenta color filter that transmits light in the blue and red wavelength bands. In this embodiment, the pixel 3 is a first pixel and the pixel 2 is a second pixel.

  The microlenses 41 to 44 are disposed on the pixels 1 to 4, respectively. The area of the micro lens 42 is larger than the area of the micro lens 43. The area of the microlens 41 and the area of the microlens 44 are larger than the area of the microlens 42. Here, the area of the microlens is an area in which the microlens is orthogonally projected onto a plane parallel to the surface SR of the semiconductor substrate. As the area of the microlens is large, the amount of light incident on the semiconductor substrate can be increased.

  In this embodiment, the following effects can be obtained in addition to the effects of the first embodiment. In the present embodiment, microlenses having different sizes are arranged for each pixel. Therefore, it is possible to reduce the difference in sensitivity for each different pixel. For example, in the structure of the second embodiment, charges from the pixel 2 can be collected in the charge accumulation region 5 c of the pixel 3. Therefore, the micro lens 44 of the pixel 4 is made larger than the micro lens 43 of the pixel 3. As a result, the sensitivity to light in the red wavelength band and the sensitivity to light in the green wavelength band can be made equal to each other, or the difference between the two can be reduced. Thereby, the color balance can be maintained while improving the sensitivity of the photoelectric conversion device.

  In Example 1 and Example 2, a micro lens may be disposed on the color filter.

  Another embodiment will be described. This embodiment is different from the first to third embodiments in that both the light in the visible wavelength band and the light in the near-infrared wavelength band are detected. Therefore, only differences from the first to third embodiments will be described, and the description of the same parts as the first to third embodiments will be omitted.

  FIG. 5 schematically shows a planar structure of the imaging apparatus. In FIG. 5, the boundary between pixels is indicated by a dotted line. The pixel 1 is provided with a color filter that transmits light in the green wavelength band. The pixel 2 is provided with a color filter that transmits light in a blue wavelength band. The pixel 4 is provided with a color filter that transmits light in the red wavelength band. The pixel 3 is provided with a visible light cut filter. The visible light cut filter is an example of a color filter, which blocks light in the visible wavelength band and transmits light in the near-infrared wavelength band. In this embodiment, the pixel 3 is a first pixel, and the pixels 1, 2, and 4 are each a second pixel.

  In FIG. 5, the region where the second buried layer 15 is disposed is indicated by hatching. The second buried layer 15 is disposed under the charge accumulation regions 5a, 5b, and 5d included in the pixels 1, 2, and 4. On the other hand, it is not arranged under the charge accumulation region 5c of the pixel 3.

  6 and 7 schematically show a cross-sectional structure taken along the line EF in FIG. 5 and a cross-sectional structure taken along the line GH in FIG. 5, respectively. In FIG. 6 and FIG. 7, the same code | symbol is attached | subjected to the member similar to FIG.

  In FIG. 6, the second photoelectric conversion region 13 a is disposed between the charge storage region 5 a of the pixel 1 and the second buried layer 15. A second photoelectric conversion region 13 b is disposed between the charge storage region 5 b of the pixel 2 and the second buried layer 15. In FIG. 7, the second photoelectric conversion region 13 d is disposed between the charge accumulation region 5 d of the pixel 4 and the second buried layer 15. Each of the charge storage regions 5a, 5b, and 5d is electrically isolated by the insulator region 11, the P-type semiconductor region 16, and the second buried layer 15. In this embodiment, the second buried layer 15 is disposed at a depth that allows sufficient sensitivity to light in the red wavelength band. For example, more than half of the light in the red wavelength band is photoelectrically converted at a position shallower than the second buried layer 15.

  As shown in FIG. 7, a visible light cut filter 70 is disposed on the charge accumulation region 5 c of the pixel 3. Further, the first photoelectric conversion region 12 is disposed between the charge storage region 5 c of the pixel 3 and the first buried layer 14. The first photoelectric conversion region 12 extends from the lower end of the charge storage region 5 c to a region below the second buried layer 15.

  According to the configuration described above, it is possible to improve sensitivity to light in the near-infrared wavelength band. For example, when the second buried layer 15 is disposed at a depth of about 3 micrometers, most of the charges generated at a position deeper than the second buried layer 15 are due to light in the near-infrared wavelength band. is there. Even a visible color filter transmits a part of light in the near-infrared wavelength band. Therefore, according to the structure of this embodiment, charges generated by light in the near-infrared wavelength band incident on the pixels 1, 2, and 4 are collected or accumulated in the charge accumulation region 5 c of the pixel 3. In this way, it is possible to improve the sensitivity to light in the near-infrared wavelength band.

  Further, light in the near-infrared wavelength band easily enters a deep position of the semiconductor substrate. Therefore, the first buried layer 14 may be omitted, and the first photoelectric conversion region 12 may extend to the deep part of the semiconductor substrate. With such a configuration, the sensitivity to light in the near-infrared wavelength band can be further improved. On the other hand, by providing the first buried layer 14, it is possible to reduce the charge generated in the deep part of the semiconductor substrate from being mixed into the charge storage region 5c. That is, crosstalk can be reduced.

  An embodiment of an imaging system according to the present invention will be described. Examples of the imaging system include a digital still camera, a digital camcorder, a copying machine, a fax machine, a mobile phone, an in-vehicle camera, and an observation satellite. FIG. 8 shows a block diagram of a digital still camera as an example of the imaging system.

  In FIG. 8, reference numeral 1001 denotes a barrier for protecting the lens, reference numeral 1002 denotes a lens for forming an optical image of a subject on the image pickup apparatus 1004, and reference numeral 1003 denotes a stop for changing the amount of light passing through the lens 1002. Reference numeral 1004 denotes the image pickup apparatus described in each of the above embodiments, which converts an optical image formed by the lens 1002 as image data. Here, it is assumed that an AD conversion unit is formed on the semiconductor substrate of the imaging device 1004. Reference numeral 1007 denotes a signal processing unit that compresses various corrections and data into imaging data output from the imaging apparatus 1004. In FIG. 8, reference numeral 1008 denotes a timing generator that outputs various timing signals to the imaging apparatus 1004 and the signal processor 1007, and 1009 denotes an overall controller that controls the entire digital still camera. Reference numeral 1010 denotes a frame memory unit for temporarily storing image data, 1011 denotes an interface unit for recording or reading on a recording medium, and 1012 denotes a detachable semiconductor memory or the like for recording or reading imaging data. It is a recording medium. Reference numeral 1013 denotes an interface unit for communicating with an external computer or the like. Here, the timing signal or the like may be input from the outside of the imaging system, and the imaging system only needs to include at least the imaging device 1004 and the signal processing unit 1007 that processes the imaging signal output from the imaging device 1004.

  In this embodiment, the configuration in which the imaging device 1004 and the AD conversion unit are provided on different semiconductor substrates has been described. However, the imaging device 1004 and the AD conversion unit may be formed on the same semiconductor substrate. Further, the imaging device 1004 and the signal processing unit 1007 may be formed on the same semiconductor substrate.

  In the embodiment of the imaging system, the imaging device 1004 uses any of the imaging devices according to the first to fourth embodiments. As described above, the sensitivity to light having a long wavelength can be improved by applying the embodiment according to the present invention in the imaging system.

DESCRIPTION OF SYMBOLS 5 Charge storage area 12 1st photoelectric conversion area 13 2nd photoelectric conversion area 14 1st embedding layer 15 2nd embedding layer 20 Separation part 30 Color filter

Claims (18)

A semiconductor substrate;
A first semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or accumulating charges generated by photoelectric conversion;
A second semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or storing charges generated by photoelectric conversion;
A first color filter disposed with respect to the first semiconductor region and transmitting light of a first wavelength band;
A second color filter that is arranged with respect to the second semiconductor region and transmits light in a second wavelength band including a wavelength band on a short wavelength side with respect to the first wavelength band;
A third semiconductor region of a second conductivity type disposed under the first semiconductor region;
A fourth semiconductor region of a second conductivity type, which is disposed below the second semiconductor region and at a position shallower than the third semiconductor region, and functions as a potential barrier against charges generated by photoelectric conversion;
An isolation portion disposed between the first semiconductor region and the second semiconductor region and disposed at a position shallower than the fourth semiconductor region;
The potential for charges generated by photoelectric conversion in at least a part of the region below the separation portion and shallower than the third semiconductor region and deeper than the fourth semiconductor region is the separation portion. And an imaging device that is lower than the fourth semiconductor region. A semiconductor substrate;
A first semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or accumulating charges generated by photoelectric conversion;
A second semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or accumulating charges generated by photoelectric conversion;
A first color filter disposed with respect to the first semiconductor region and transmitting light of a first wavelength band;
A second color filter that is arranged with respect to the second semiconductor region and transmits light in a second wavelength band including a wavelength band on a short wavelength side with respect to the first wavelength band;
A third semiconductor region of a second conductivity type disposed under the first semiconductor region;
A second semiconductor region of a second conductivity type, which is disposed below the second semiconductor region and at a position shallower than the third semiconductor region;
A separation portion disposed between the first semiconductor region and the second semiconductor region;
A fifth semiconductor region of a first conductivity type disposed between the first semiconductor region and the third semiconductor region and collecting charges generated by photoelectric conversion into the first semiconductor region; ,
The imaging device, wherein the fifth semiconductor region extends from the first semiconductor region to a region below the fourth semiconductor region. A semiconductor substrate;
A first semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or accumulating charges generated by photoelectric conversion;
A second semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or accumulating charges generated by photoelectric conversion;
A first color filter disposed with respect to the first semiconductor region and transmitting light of a first wavelength band;
A second color filter that is arranged with respect to the second semiconductor region and transmits light in a second wavelength band including a wavelength band on a short wavelength side with respect to the first wavelength band;
A third semiconductor region of a second conductivity type disposed under the first semiconductor region;
A second semiconductor region of a second conductivity type, which is disposed below the second semiconductor region and at a position shallower than the third semiconductor region;
A separation portion disposed between the first semiconductor region and the second semiconductor region;
A first conductivity type second conductivity type fifth semiconductor disposed between the first semiconductor region and the third semiconductor region and collecting charges generated by photoelectric conversion into the first semiconductor region. An area, and
The fifth semiconductor region extends from a lower end of the first semiconductor region to a region below the fourth semiconductor region;
The imaging device, wherein the impurity concentration of the fifth semiconductor region is lower than both the impurity concentration of the third semiconductor region and the impurity concentration of the fourth semiconductor region. A semiconductor substrate;
A first semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or accumulating charges generated by photoelectric conversion;
A second semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or storing charges generated by photoelectric conversion;
A first color filter disposed with respect to the first semiconductor region and transmitting light of a first wavelength band;
A second color filter disposed with respect to the second semiconductor region and transmitting light of a second wavelength band;
A third semiconductor region of a second conductivity type disposed under the first semiconductor region;
A fourth semiconductor region of a second conductivity type, which is disposed below the second semiconductor region and at a position shallower than the third semiconductor region, and functions as a potential barrier against charges generated by photoelectric conversion;
An isolation portion disposed between the first semiconductor region and the second semiconductor region and disposed at a position shallower than the fourth semiconductor region;
The first wavelength band includes a wavelength band on a long wavelength side with respect to the second wavelength band,
The potential for charges generated by photoelectric conversion in at least a part of the region below the separation portion and shallower than the third semiconductor region and deeper than the fourth semiconductor region is the separation portion. And an imaging device that is lower than the fourth semiconductor region. A semiconductor substrate;
A first semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or accumulating charges generated by photoelectric conversion;
A second semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or accumulating charges generated by photoelectric conversion;
A first color filter disposed with respect to the first semiconductor region and transmitting light of a first wavelength band;
A second color filter disposed with respect to the second semiconductor region and transmitting light of a second wavelength band;
A third semiconductor region of a second conductivity type disposed under the first semiconductor region;
A second semiconductor region of a second conductivity type, which is disposed below the second semiconductor region and at a position shallower than the third semiconductor region;
A separation portion disposed between the first semiconductor region and the second semiconductor region;
A fifth semiconductor region of a first conductivity type disposed between the first semiconductor region and the third semiconductor region and collecting charges generated by photoelectric conversion into the first semiconductor region; ,
The first wavelength band includes a wavelength band on a long wavelength side with respect to the second wavelength band,
The imaging device, wherein the fifth semiconductor region extends from the first semiconductor region to a region below the fourth semiconductor region. A semiconductor substrate;
A first semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or accumulating charges generated by photoelectric conversion;
A second semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or accumulating charges generated by photoelectric conversion;
A first color filter disposed with respect to the first semiconductor region and transmitting light of a first wavelength band;
A second color filter disposed with respect to the second semiconductor region and transmitting light of a second wavelength band;
A third semiconductor region of a second conductivity type disposed under the first semiconductor region;
A second semiconductor region of a second conductivity type, which is disposed below the second semiconductor region and at a position shallower than the third semiconductor region;
A separation portion disposed between the first semiconductor region and the second semiconductor region;
A first conductivity type second conductivity type fifth semiconductor disposed between the first semiconductor region and the third semiconductor region and collecting charges generated by photoelectric conversion into the first semiconductor region. An area, and
The first wavelength band includes a wavelength band on a long wavelength side with respect to the second wavelength band,
The fifth semiconductor region extends from a lower end of the first semiconductor region to a region below the fourth semiconductor region;
The imaging device, wherein the impurity concentration of the fifth semiconductor region is lower than both the impurity concentration of the third semiconductor region and the impurity concentration of the fourth semiconductor region.   Corresponding to each of the first and second semiconductor regions, a floating diffusion part, a transfer gate electrode for transferring charges to the floating diffusion part, and a signal based on the potential of the floating diffusion part The imaging apparatus according to claim 1, further comprising: an amplifying unit that outputs the imaging unit. The isolation part includes an insulator region, a sixth semiconductor region of a second conductivity type, and a part of the fourth semiconductor region,
8. The sixth semiconductor region according to claim 1, wherein the sixth semiconductor region is arranged between the insulator region and a part of the fourth semiconductor region. 9. Imaging device.   The imaging device according to claim 8, wherein the insulator region, the sixth semiconductor region, and the fourth semiconductor region are arranged so as to surround the second semiconductor region.   10. The imaging device according to claim 1, wherein the third semiconductor region extends to a region below the second semiconductor region. 11.   11. The imaging apparatus according to claim 1, wherein the second color filter is thinner than the first color filter. A first lens disposed with respect to the first semiconductor region;
A second lens disposed with respect to the second semiconductor region,
The image pickup apparatus according to claim 1, wherein an area of the second lens is larger than an area of the first lens. The first color filter cuts light in a visible wavelength band and transmits light in a near-infrared wavelength band;
The imaging device according to any one of claims 1 to 12, wherein the second color filter transmits light in a visible wavelength band. The first wavelength band is red and the second wavelength band is any of green, blue, cyan, magenta, or yellow, or
The first wavelength band is green and the second wavelength band is either blue, cyan, or magenta, or
The first wavelength band is magenta and the second wavelength band is any of green, blue, or cyan, or
The imaging device according to any one of claims 1 to 12, wherein the first wavelength band is cyan and the second wavelength band is blue.   A region below the isolation portion and shallower than the third semiconductor region and deeper than the fourth semiconductor region is of a second conductivity type having a lower impurity concentration than the fourth semiconductor region. The imaging device according to claim 1, wherein the imaging device is a semiconductor region. An imaging device according to any one of claims 1 to 15,
An imaging system comprising: a signal processing device that processes a signal from the imaging device. A semiconductor substrate;
A first semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or accumulating charges generated by photoelectric conversion;
A second semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or storing charges generated by photoelectric conversion;
A first color filter disposed with respect to the first semiconductor region and transmitting light of a first wavelength band;
A second color filter that is arranged with respect to the second semiconductor region and transmits light in a second wavelength band including a wavelength band on a short wavelength side with respect to the first wavelength band;
A buried layer of a second conductivity type disposed under the second semiconductor region;
A separation portion disposed between the first semiconductor region and the second semiconductor region;
A photoelectric conversion region that extends from a lower end of the first semiconductor region to a region under the buried layer and collects generated charges in the first semiconductor region. Imaging device. A semiconductor substrate;
A first semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or accumulating charges generated by photoelectric conversion;
A second semiconductor region of a first conductivity type disposed on the semiconductor substrate and collecting or storing charges generated by photoelectric conversion;
A first color filter disposed with respect to the first semiconductor region and transmitting light of a first wavelength band;
A second color filter disposed with respect to the second semiconductor region and transmitting light of a second wavelength band;
A buried layer of a second conductivity type disposed under the second semiconductor region;
A separation portion disposed between the first semiconductor region and the second semiconductor region;
A photoelectric conversion region that extends from a lower end of the first semiconductor region to a region under the buried layer and collects generated charges in the first semiconductor region; and
The imaging apparatus, wherein the first wavelength band includes a wavelength band on a longer wavelength side than the second wavelength band.

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