JP2015111728A - Photoelectric converter and imaging system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce mixing of electric charge into an electric charge retaining section.SOLUTION: In a photoelectric converter which has an electric charge retaining section and an element isolation region electrically separating the electric charge retaining section, the element isolation region includes an insulator portion. The lower end of the insulator portion is provided in a depth equal to the lower end of a semiconductor region constituting the electric charge retaining section or so as to be deeper than the lower end of the semiconductor region constituting the electric charge retaining section.

Description

  The present case relates to a configuration of a charge holding unit of a photoelectric conversion device having a charge holding unit.

  In recent years, CCD-type and MOS-type photoelectric conversion devices are used in many digital still cameras and digital camcorders. In a MOS type photoelectric conversion device, an element structure has been developed for realizing a global shutter function for keeping the accumulation time of photoelectric conversion elements constant. That is, the photoelectric conversion element has a charge holding portion. In the configuration having the charge holding portion, Patent Document 1 discloses a configuration in which a gate electrode is embedded in order to suppress smear reduction. Further, Patent Document 2 discloses a semiconductor having a conductivity type opposite to the charge holding portion below the charge holding portion in order to reduce the charge generated in the deep part of the semiconductor substrate from entering the charge holding portion (charge storing portion). A configuration for providing a region is disclosed.

JP 2007-294931 A JP 2008-004692 A

  However, in Patent Document 1, there is a possibility that charges generated deep in the semiconductor substrate or charges from other elements are mixed into the charge holding portion. Also in Patent Document 2, there is a possibility that charges from other elements and the like are mixed into the charge holding portion.

  In view of the above, an object of the present invention is to provide a photoelectric conversion device having a charge holding portion that reduces charge mixing.

  A photoelectric conversion device according to an embodiment of the present invention includes a semiconductor substrate, a first semiconductor region of a first conductivity type disposed on the semiconductor substrate and constituting a part of a photoelectric conversion element, and the semiconductor substrate. A first-conductivity-type second semiconductor region arranged to hold charges generated in the photoelectric conversion element, a first-conductivity-type third semiconductor region disposed on the semiconductor substrate, and the semiconductor substrate A photoelectric conversion device comprising: a first gate electrode which is disposed on the first gate electrode and transfers an electric charge of the second semiconductor region to the third semiconductor region; and an element isolation region including at least an insulator portion. A body portion is disposed so as to electrically isolate the second semiconductor region, and a lower end of the insulator portion has the same depth as a lower end of the second semiconductor region, or the second semiconductor region Be deeper The photoelectric conversion device according to claim.

  According to the present invention, it is possible to reduce the mixing of electric charges into the electric charge holding portion, and it is possible to provide a low-noise photoelectric conversion device.

Example of pixel circuit of photoelectric conversion device Plane layout diagram of a photoelectric conversion device for explaining the first embodiment 2A is a schematic cross-sectional view taken along line AB in FIG. 2, FIG. 2B is a schematic cross-sectional view taken along line CD in FIG. 2, FIG. 2C is a schematic cross-sectional view showing a modification, and FIG. Cross-sectional schematic diagram (A) Plane layout diagram of a photoelectric conversion device for explaining the second embodiment, (b) A schematic cross-sectional view taken along line CD in FIG. Planar layout diagram of photoelectric conversion device for explaining the third embodiment (A) Schematic cross-sectional view taken along line CD in FIG. 5, (b) Schematic cross-sectional view showing a modification. (A) A schematic cross-sectional view taken along the line AB of FIG. 2 for explaining the fourth embodiment, and (b) a schematic cross-sectional view showing a modification. (A) A schematic cross-sectional view taken along line AB in FIG. 2 for explaining the fifth embodiment, and (b) a schematic cross-sectional view taken along line CD in FIG. Block diagram explaining the imaging system

  The present invention includes an element isolation region that is in contact with a semiconductor region functioning as a charge holding unit directly or via a semiconductor region functioning as a channel stop in a photoelectric conversion device having a charge holding unit in an imaging region. This element isolation region has an insulator, and is provided to the same depth or deeper than the reference surface including the light receiving surface of the photoelectric conversion element, as compared with the semiconductor region of the charge holding portion. By having such a configuration, mixing of charges into the charge holding portion is reduced.

  Next, a circuit of a photoelectric conversion device having a charge holding portion will be described. In the embodiment, the signal charge is assumed to be electrons, and the MOS transistor is assumed to be N-type.

(Example of pixel circuit)
FIG. 1 shows an example of a pixel circuit to which the present invention can be applied. A pixel is a minimum repeating unit including one photoelectric conversion element, and is denoted by 100 in FIG. In the photoelectric conversion device, the pixels 100 are arranged one-dimensionally or two-dimensionally to form an imaging region. In FIG. 1, four pixels in two columns (m, m + 1) and two rows (n, n + 1) are arranged.

  The pixel 100 will be described. 101 is a photoelectric conversion element, 102 is a charge holding unit, and 103 is a floating diffusion unit. Reference numeral 104 denotes a first gate electrode, which transfers charges generated in the photoelectric conversion element 101 to the charge holding unit 102. Reference numeral 105 denotes a second gate electrode, which transfers the charge in the charge holding unit 102 to the floating diffusion unit 103. Reference numeral 106 denotes an amplifying MOS transistor, and the node of the gate electrode is connected to the floating diffusion portion 103. The amplification MOS transistor 106 outputs a signal corresponding to the potential of the floating diffusion portion 103 to the signal line OUT. Reference numeral 107 denotes a selection MOS transistor which controls the voltage supplied to the drain of the amplification MOS transistor 106 and controls the output of the signal. A reset MOS transistor 108 resets the node of the gate electrode of the amplification MOS transistor 106 to a specified potential (reset potential). Reference numeral 109 denotes a third gate electrode for controlling discharge of electric charges. The charge of the photoelectric conversion element 101 can be discharged to the node of the power supply line 110 by the third gate electrode. A portion including the third gate electrode 109 that performs such a discharge operation and the node of the power supply line is a discharge portion. Reference numeral 111 denotes a power supply line connected to the reset MOS transistor 108 or the like, and may be connected to the power supply line 110. RES, TX2, TX1, SEL and TX3 are control lines connected to the gate electrodes of the MOS transistors for supplying control pulses. RES is connected to the gate electrode of the reset MOS transistor, TX1 is connected to the first gate electrode, TX2 is connected to the second gate electrode, TX3 is connected to the third gate electrode, and SEL is connected to the gate electrode of the selection MOS transistor. .

  In such a circuit, the following operation is possible. First, charges generated in the plurality of photoelectric conversion elements 101 are transferred from the plurality of photoelectric conversion elements 101 to the charge holding unit 102 at the same timing, respectively. Then, a new charge generated in the photoelectric conversion element 101 is obtained while the charge holding unit 102 holds the charge.

  The following operation is also possible with such a circuit. The charge generated in the photoelectric conversion element 101 is simultaneously stored in the charge holding unit 102. Then, transfer is performed from the plurality of charge holding units 102 to the floating diffusion unit 103 at the same timing without going through a reset operation. In other words, one accumulation period is not determined by the first gate electrode 104 but is defined by, for example, the third gate electrode 109. Here, one accumulation period is determined in common by each photoelectric conversion unit when an image of one frame is taken, and can be rephrased as an exposure time of each frame. Specific configurations and operations for performing this operation include the following. First, the first gate electrode 104 between the photoelectric conversion element 101 and the charge holding unit 102 can operate as a switch, and the switch is turned on when charges are accumulated in the photoelectric conversion element and the charge holding unit. Is the action. Next, a so-called embedded channel is formed between the photoelectric conversion element 101 and the charge holding unit 102, and the photoelectric conversion element and the charge holding unit are electrically connected. Here, the buried channel is a buried channel transistor. For example, a semiconductor region having a lower potential with respect to signal charges is provided below the gate electrode, between the source region and the drain region and shallower than the source region and the drain region.

  In any case, the charge holding unit 102 has a period for holding charge during a period until the charge is read or during a period in which the charge is accumulated. In particular, when the latter charge accumulation is performed in the photoelectric conversion element 101 and the charge holding unit 102, the charge holding unit 102 holds the charge for a longer time than in the former case. It is desirable to apply the configuration of the charge holding portion.

  The pixel circuit is not limited to the one shown in FIG. 1, and a configuration in which a charge holding unit and a readout circuit are shared by a plurality of photoelectric conversion elements may be used.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
The configuration of this embodiment will be described with reference to FIGS. FIG. 2 is a plan layout view of four pixels 100 shown in FIG. Reference numeral 201 denotes a semiconductor region constituting the photoelectric conversion element 101, and the surface thereof serves as a light receiving surface. Reference numeral 202 denotes a second semiconductor region constituting the charge holding portion 102. Reference numeral 203 denotes a third semiconductor region constituting the floating diffusion portion 103. Reference numeral 204 denotes a first gate electrode which extends on the second semiconductor region 202. Reference numeral 205 denotes a second gate electrode. Reference numeral 206 denotes a contact for electrically connecting the third semiconductor region 203 and the amplification MOS transistor 106. An element isolation region 207 electrically isolates elements from each other and defines an active region. The element isolation region 207 includes an insulator such as STI. Reference numeral 208 denotes a first active region defined by the element isolation region 207, and a semiconductor region constituting the photoelectric conversion element 101 and the charge holding unit 102 is arranged. Reference numeral 209 denotes a light shield, which shields the charge holding unit 102 from light. Here, the other elements of the pixel 100 such as the amplification MOS transistor 106 are assumed to be disposed in the region 210 and the description thereof is omitted.

  FIG. 3 is a schematic cross-sectional view of the photoelectric conversion device. 3A is a schematic cross-sectional view taken along line AB in FIG. 2, and FIG. 3B is a schematic cross-sectional view taken along line CD. FIGS. 3C and 3D are drawings similar to FIG. 3B and show a modification.

  FIG. 3A will be described. Parts having the same functions as those in FIG. 2 are denoted by the same reference numerals and description thereof is omitted. Reference numeral 301 denotes a first semiconductor region of the first conductivity type (hereinafter n-type). Reference numeral 302 denotes a second conductivity type (hereinafter referred to as p-type) semiconductor region which is disposed on the surface of the first semiconductor region 301 and constitutes an embedded photoelectric conversion element. Reference numeral 303 denotes an n-type semiconductor region having a concentration lower than that of the first semiconductor region. These 301 to 303 constitute the photoelectric conversion element 201. The light receiving surface of the photoelectric conversion element 201 is 201a. Further, reference numeral 304 denotes a p-type fifth semiconductor region disposed under the second semiconductor region 202. Reference numerals 305 to 308 denote p-type semiconductor regions. Reference numeral 309 denotes an insulating film. Reference numeral 310 denotes a semiconductor region which is a base portion having the original characteristics of the semiconductor substrate, and has an n-type conductivity type. The p-type semiconductor region 307 has a function of electrically separating the n-type semiconductor region 310 from the photoelectric conversion element and the like. The p-type semiconductor region 308 is disposed below the element isolation region 207 and electrically isolates the pixel 100 from the adjacent pixel 100.

  Here, the semiconductor substrate is a semiconductor substrate that is a material substrate, and is a member in a state where one or a plurality of semiconductor regions are formed, a member in the middle of a series of manufacturing steps, or a member that has undergone a series of manufacturing steps. Including. A surface of the photoelectric conversion element 201, that is, an interface between a semiconductor region constituting the photoelectric conversion element 201 and an insulating film such as an oxide film is defined as a light receiving surface 201a. A surface including the light receiving surface 201 is a reference surface 311, a direction from the reference surface 311 toward the semiconductor region 310 is a downward direction, and a depth direction of the semiconductor substrate. The portion below the reference surface 311 can be said to be a semiconductor substrate here. Here, the upper part of the element isolation region 207 may exceed the reference plane 311. However, it can be said that the lower portion of the element isolation region 207 is disposed closer to the semiconductor substrate than the reference surface 311 and the element isolation region 207 is disposed on the semiconductor substrate.

  Next, FIG. 3B will be described. Parts having the same functions as those in FIG. 3A are denoted by the same reference numerals and description thereof is omitted. The insulating film 309 is omitted. Here, the second semiconductor region 202 is in contact with a part of the element isolation region 207 that defines the first active region in which the second semiconductor region 202 is disposed. A part of the element isolation region 207 in contact with the second semiconductor region 202 is far from the reference surface 311 compared to the second semiconductor region 202, in other words, deeply arranged toward the semiconductor region 310. Yes. With the structure in which the element isolation region 207 is deeper in the semiconductor substrate than the second semiconductor region 202, it is possible to reduce charge mixing from the lateral direction (the direction in which the element isolation region 207 is present). In addition, the configuration of the charge holding unit of the present embodiment is particularly effective when applied to the following cases. This is the case where the first gate electrode, the first semiconductor region, and the second semiconductor region are configured as a buried channel transistor. More specifically, below the first gate electrode, between the first semiconductor region 301 and the second semiconductor region and shallower than the first semiconductor region 301 and the second semiconductor region. An n-type semiconductor region having a lower concentration than the first semiconductor region 301 is provided. This n-type semiconductor region is defined as a sixth semiconductor region. Such a configuration is particularly effective because it takes a long time for the charges to be held in the charge holding portion 102. Note that here, even when the element isolation region 207 is provided to a depth equal to that of the second semiconductor region 202, it is possible to reduce mixing of charges in the lateral direction.

  Further, the fifth semiconductor region 304 is disposed below the second semiconductor region 202 in contact with the bottom surface of the element isolation region 207. That is, the second semiconductor region 202 is surrounded in this cross section. With such a configuration, it is possible to reduce the mixing of charges from the lateral direction or from the deep part of the semiconductor substrate.

  In addition, a light shield 209 is provided over the second semiconductor region 202. With such a configuration, it is possible to suppress the incidence of light on the charge holding unit 102. Furthermore, since the light shield 209 extends to the element isolation region 207, it is possible to further reduce the incidence of the light of the charge holding portion 102.

  Here, a gap is provided between the second semiconductor region 202 and the fifth semiconductor region 304. This interval is, for example, an n-type semiconductor region having a lower concentration than the second semiconductor region 202 or a p-type semiconductor region having a lower concentration than the fifth semiconductor region 304. Further, as shown in FIG. 3C, the fifth semiconductor region 304 may be disposed above the bottom surface of the element isolation region 207. Further, as shown in FIG. 3D, the fifth semiconductor region 304 may be disposed so as to form a PN junction interface with the second semiconductor region. With such a configuration, the capacity of the PN junction increases, so that the capacity value of the charge holding unit 102 can be increased. Here, as for the outer edge of each semiconductor region, when the surrounding semiconductor region is the same conductivity type as its own, the outer edge is a region where the impurity concentrations are substantially the same. Further, when the surrounding semiconductor region has a conductivity type opposite to its own conductivity type, a region where each net impurity concentration is substantially zero is defined as an outer edge and is defined as a PN junction interface. The net impurity concentration is a difference in concentration between the N-type impurity and the P-type impurity.

  Further, the p-type semiconductor regions 304 to 307 below the second semiconductor region 202 are configured such that the potential with respect to electric charges decreases so that the p-type impurity concentration decreases toward the deep part of the semiconductor substrate. It is desirable. This is because charges that are not desired to be taken into the second semiconductor region 202 can be quickly discharged to the semiconductor region 310. Note that even if there is a portion where the potential increases in the portions of the semiconductor regions 304 to 307, it is sufficient that the charge can be discharged to the semiconductor region 310.

(Second Embodiment)
In this embodiment, the arrangement of the element isolation regions 207 is different from that of the first embodiment, and the arrangement relationship between the second semiconductor region 202 and the element isolation regions 207 is different. This will be described with reference to FIG. 4A is a plan layout view, and FIG. 4B is a schematic cross-sectional view. 4A corresponds to FIG. 2, and FIG. 4B corresponds to FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In FIG. 4A and FIG. 4B, portions of the element isolation region 207 adjacent to the second semiconductor region are referred to as 207a and 207b for the sake of explanation. Since the element isolation region 207 defining the first active region 208 is different in shape and arrangement, the second semiconductor region 202 is not in contact with the element isolation region 207b. There is a region 401 between the second semiconductor region 202 and the element isolation region 207b. Even with such a structure, since the element isolation region 207a is in contact with at least a part of the second semiconductor region, it is possible to reduce the mixing of charges from the lateral direction.

  In the region 401, a p-type semiconductor region 308 is provided so as to extend. The p-type semiconductor region 308 may not be provided in the region 401 between the second semiconductor region 202 and the element isolation region 207b. However, the provision of the semiconductor region 308 in the region 401 can further reduce charge mixing.

  It is also possible to apply the configuration of FIG. 3C or FIG. 3D of the first embodiment to this embodiment.

(Third embodiment)
This embodiment is different from the first embodiment in the arrangement of the second semiconductor region 202 and the element isolation region 207. This will be described with reference to FIGS. FIG. 5 is a plan layout view, and FIG. 6 is a schematic cross-sectional view. 5 corresponds to FIG. 2, and FIG. 6 (a) corresponds to FIG. 3 (d). FIG. 6B is a diagram for explaining a modification of the present embodiment, and corresponds to FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 5, the second semiconductor region 202 is not disposed up to the first active region 208, and a region 501 exists between the element isolation region 207 and the second semiconductor region 202. doing. In FIG. 6A corresponding to the drawing, the region 501a and the region 501b exist between the second semiconductor region 202 and the element isolation regions 207a and 207b, and the second semiconductor region is equivalent to the region 501. 202 is arranged offset from the element isolation region 207. With such a configuration, dark current due to defects at the interface between the insulator in the element isolation region and the semiconductor region can be reduced. That is, the region 501 can be said to be a dark current reduction region. The region 501 is a p-type semiconductor region.

  FIG. 6B shows a modification in which a p-type fourth semiconductor region 502 is provided in the region 501. The fourth semiconductor region 502 is disposed on the side wall and the bottom surface of the element isolation region 207, and is preferably disposed so as to surround the element isolation region 207. The fourth semiconductor region 502 is a p-type semiconductor region having a higher concentration than the fifth semiconductor region 304, and can function as a dark current reduction region that reduces dark current from the element isolation region 207. The fourth semiconductor region may function as a channel stop. By including the fourth semiconductor region 502 as described above, it is possible to further reduce noise from the element isolation region 207 as compared with the configuration of FIG. In addition, since the second semiconductor region 202 and the high-concentration p-type fourth semiconductor region 502 have a PN junction interface, the capacitance of the second semiconductor region 202 can be increased.

  In the present embodiment, an example in which the fourth semiconductor region 502 is arranged in the offset region 501 is shown. However, the fourth semiconductor region 502 is a high-concentration p-type semiconductor region, and is arranged so as to cancel the second semiconductor region 202 in contact with the element isolation region 207 as in the first embodiment. There may be.

  Further, the configuration of the charge holding unit of the present embodiment may be applied to the following case. It has a sixth semiconductor region as described in the first embodiment, and includes a first gate electrode, a first semiconductor region, and a second semiconductor region, like a buried channel type transistor. This is a case where a simple configuration is made. More specifically, below the first gate electrode, between the first semiconductor region 301 and the second semiconductor region and shallower than the first semiconductor region 301 and the second semiconductor region. An n-type semiconductor region having a lower concentration than the first semiconductor region 301 is provided. Such a configuration is particularly effective because it takes a long time for the charges to be held in the charge holding portion 102.

  It is also possible to apply the arrangement of the fifth semiconductor region 304 of FIG. 3C or FIG. 3D of the first embodiment to this embodiment. Further, as in the second embodiment, a part of the element isolation region 207 may be separated from the second semiconductor region 202.

(Fourth embodiment)
This embodiment will be described with reference to FIG. This embodiment is different from the first embodiment in that there is no p-type semiconductor region 306 but a region 303a. FIG. 7A is a schematic cross-sectional view corresponding to FIG. Moreover, FIG.7 (b) is a cross-sectional schematic diagram which shows the modification of this embodiment corresponding to Fig.7 (a). The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  First, the configuration of FIG. 7A will be described. In the present embodiment, the p-type semiconductor region 306 existing in FIG. 3A is not present in the lower portion of the second semiconductor region 202 serving as the charge holding portion, but there is a region 303 a continuous with the semiconductor region 303. The region 303 a may extend from the semiconductor region 303 as long as it is electrically connected to the semiconductor region 303. With such a configuration, when obliquely incident light generates charges due to photoelectric conversion in the lower portion of the second semiconductor region 202, the charges are collected in the first semiconductor region 301 through the semiconductor region 303. It becomes easy. And an improvement in sensitivity can be expected. Further, the presence of the p-type semiconductor regions 304 and 305 makes it difficult for charges to move from the region 303 a to the second semiconductor region 202, so that charge mixing into the second semiconductor region 202 is prevented. It becomes possible to reduce.

  In FIG. 7B, the p-type semiconductor region 306 that is present in FIG. 3A is not present, and the p-type semiconductor region 307 is present in the vicinity of the p-type semiconductor region 305. With such a configuration, it is possible to discharge charges generated in the lower portion of the second semiconductor region 202 to the semiconductor region 310, and to reduce the entry of charges into the second semiconductor region 202. Become.

  Further, in the p-type semiconductor regions 304, 305, and 307 below the second semiconductor region 202, the potential with respect to the charge is lowered so that the p-type impurity concentration is lowered toward the deep part of the semiconductor substrate. It is desirable that This is because charges that are not desired to be taken into the second semiconductor region 202 can be discharged to the semiconductor region 310 with high probability. Note that even if there is a portion where the potential increases in the semiconductor regions 304, 305, and 307, it is only necessary that the charge can be discharged to the semiconductor region 310.

  The present embodiment can be applied by appropriately combining the configurations of the first to third embodiments.

(Fifth embodiment)
This embodiment will be described with reference to FIG. This embodiment is different from the first embodiment in that there is no p-type semiconductor region 308 and the p-type semiconductor regions 304 to 306 extend to the lower part of the element isolation region 207. 8A is a schematic cross-sectional view corresponding to FIG. 3A, and FIG. 8B is a schematic cross-sectional view corresponding to FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIGS. 8A and 8B, in this embodiment, the p-type semiconductor regions 304, 305, and 306 are arranged extending to the lower portion of the element isolation region 207. In other words, the p-type semiconductor regions 304, 305, and 306 are arranged over the entire surface of the semiconductor substrate except for the photoelectric conversion element 201. Such a configuration makes it possible to reduce the number of manufacturing steps. In addition, it is possible to reduce the possibility that the characteristics of the photoelectric conversion element 201 are changed due to variation in position during manufacturing.

  Here, as in the other embodiments, the p-type semiconductor regions 304 to 307 below the second semiconductor region 202 are charged against charges so that the p-type impurity concentration decreases toward the deep part of the semiconductor substrate. It is desirable for the potential to be lowered. This is because charges that are not desired to be taken into the second semiconductor region 202 can be discharged to the semiconductor region 310 with high probability. Note that even if there is a portion where the potential increases in the portions of the semiconductor regions 304 to 307, it is sufficient that the charge can be discharged to the semiconductor region 310.

  Further, the present embodiment can be applied by appropriately combining the configurations of the first to fourth embodiments.

(Application to imaging system)
In this embodiment, the case where the photoelectric conversion device described in the first to fifth embodiments is applied to an imaging system will be described with reference to FIG. The imaging system is a digital still camera, a digital video camera, or a digital camera for mobile phones.

  FIG. 9 is a block diagram of a digital still camera. An optical image of the subject is formed on the imaging surface of the photoelectric conversion device 804 by an optical system including the lens 802 and the like. On the outside of the lens 802, a barrier 801 serving both as a protection function of the lens 802 and a main switch can be provided. The lens 802 can be provided with a stop 803 for adjusting the amount of light emitted therefrom. The imaging signal output from the photoelectric conversion device 804 through a plurality of channels is subjected to various corrections, clamping, and the like by the imaging signal processing circuit 805. Imaging signals output from the imaging signal processing circuit 805 through a plurality of channels are analog-digital converted by an A / D converter 806. The image data output from the A / D converter 806 is subjected to various corrections, data compression, and the like by a signal processing unit (image processing unit) 807. The photoelectric conversion device 804, the imaging signal processing circuit 805, the A / D converter 806, and the signal processing unit 807 operate in accordance with the timing signal generated by the timing generation unit 808. Each block is controlled by an overall control / arithmetic unit 809. In addition, a memory unit 810 for temporarily storing image data and a recording medium control interface unit 811 for recording or reading an image on a recording medium are provided. The recording medium 812 includes a semiconductor memory or the like and can be attached and detached. Furthermore, an external interface (I / F) unit 813 for communicating with an external computer or the like may be provided. Here, 805 to 808 may be formed on the same chip as the photoelectric conversion device 804.

  Next, the operation of FIG. 9 will be described. When the barrier 801 is opened, the main power supply, the control system power supply, and the image pickup system circuit such as the A / D converter 806 are sequentially turned on. Thereafter, the overall control / arithmetic unit 809 opens the aperture 803 to control the exposure amount. A signal output from the photoelectric conversion device 804 passes through the imaging signal processing circuit 805 and is provided to the A / D converter 806. The A / D converter 806 A / D converts the signal and outputs it to the signal processing unit 807. The signal processing unit 807 processes the data and provides it to the overall control / calculation unit 809, and the overall control / calculation unit 809 performs computation to determine the exposure amount. The overall control / calculation unit 809 controls the aperture based on the determined exposure amount.

  Next, the overall control / calculation unit 809 extracts a high frequency component from the signal output from the photoelectric conversion device 804 and processed by the signal processing unit 807, and calculates the distance to the subject based on the high frequency component. Thereafter, the lens 802 is driven to determine whether or not it is in focus. If it is determined that the subject is not in focus, the lens 802 is driven again to calculate the distance.

  Then, after the in-focus state is confirmed, the main exposure starts. When the exposure is completed, the imaging signal output from the photoelectric conversion device 804 is corrected in the imaging signal processing circuit 805, A / D converted by the A / D converter 806, and processed by the signal processing unit 807. The image data processed by the signal processing unit 807 is accumulated in the memory unit 810 by the overall control / arithmetic unit 809. Thereafter, the image data stored in the memory unit 810 is recorded on the recording medium 812 via the recording medium control I / F unit under the control of the overall control / arithmetic unit 809. Further, the image data is provided to a computer or the like through the external I / F unit 813 and processed.

  Thus, the photoelectric conversion device of the present invention is applied to an imaging system. By using the photoelectric conversion device of the present invention, it is possible to reduce noise to the image signal due to the global shutter, and thus it is possible to obtain a higher quality image. Further, noise removal in the signal processing circuit or the like is facilitated.

  In the above, several embodiments of the present invention have been described. However, the present invention is not limited to each embodiment, and can be changed as appropriate. The configurations of the embodiments can be combined as appropriate. For example, the present invention is not limited to a configuration in which a discharge unit that discharges charges in the horizontal direction with respect to the semiconductor substrate shown in FIG. 1, but may have a configuration in which charges are discharged in the vertical direction of the semiconductor substrate.

  Further, the configuration of the first gate electrode 204 is not limited to the configuration described in this embodiment. For example, the first gate electrode 204 may control the potential between the first semiconductor region 301 and the second semiconductor region 202. In addition, the first gate electrode 204 does not need to extend over the second semiconductor region 202. In addition, the first gate electrode 204 may not extend to the second semiconductor region 202 but may have a separate gate electrode on the second semiconductor region 202. Further, an n-type sixth semiconductor region having a lower concentration than the first semiconductor region 301 may be provided below the first gate electrode 204. The first semiconductor region 301, the second semiconductor region 202, the gate electrode, and the fifth semiconductor region may form a buried channel transistor. Furthermore, the arrangement of the semiconductor regions is not limited to the form described above, and the semiconductor regions may be divided into a plurality of regions or formed into one region. In addition, the polarity of the charge, the polarity of the semiconductor region, and the polarity of the transistor can be changed as appropriate.

102 charge holding portion 202 first conductive type second semiconductor region 207 element isolation region 502 second conductive type fourth semiconductor region 304 second conductive type fifth semiconductor region 305, 306, 307, 308 second Conductive semiconductor region

A photoelectric conversion device according to an embodiment of the present invention is disposed on a semiconductor substrate, and is disposed on the semiconductor substrate, the first conductivity type first semiconductor region constituting a part of the photoelectric conversion element, and the photoelectric conversion device. A first conductivity type second semiconductor region in which charges generated in the conversion element are held; a first conductivity type third semiconductor region disposed on the semiconductor substrate; and a semiconductor substrate disposed on the semiconductor substrate, In the photoelectric conversion device having a first gate electrode that transfers the charge of the second semiconductor region to the third semiconductor region, and an element isolation region including at least an insulator portion, the insulator portion includes: In the first cross section along the first direction in which the first semiconductor region and the second semiconductor region are arranged, including the first portion, the second portion, and the third portion, the first portion Between the portion and the second semiconductor region, the first A semiconductor region is disposed, and in the first cross section, the first semiconductor region extends deeper in the semiconductor substrate than a lower end of the first portion, and intersects the first direction. In the second cross section along the second direction, the second semiconductor region is disposed between the second portion and the third portion, and in the second cross section, the second section The semiconductor region is arranged at a position shallower than the lower end of the second portion and the lower end of the third portion.
A photoelectric conversion device according to another embodiment of the present invention is disposed on a semiconductor substrate, and is disposed on the semiconductor substrate, the first conductivity type first semiconductor region constituting a part of the photoelectric conversion element, and the photoelectric conversion device. A first conductivity type second semiconductor region in which charges generated in the conversion element are held; a first conductivity type third semiconductor region disposed on the semiconductor substrate; and a semiconductor substrate disposed on the semiconductor substrate, In the photoelectric conversion device having a first gate electrode that transfers the charge of the second semiconductor region to the third semiconductor region, and an element isolation region including at least an insulator portion, the insulator portion includes: In the first cross section along the first direction in which the first semiconductor region and the second semiconductor region are arranged, including the first portion, the second portion, and the third portion, the first portion Between the portion and the second semiconductor region, the first A conductor region is disposed, and in the first cross section, the first semiconductor region extends deeper in the semiconductor substrate than a lower end of the first portion, and intersects the first direction. In the second cross section along the second direction, the second semiconductor region is disposed between the second portion and the third portion, and in the second cross section, the second section The lower end of this part and the lower end of the third part are arranged deeper than the second semiconductor region.

Claims (14)

A semiconductor substrate;
A first semiconductor region of a first conductivity type disposed on the semiconductor substrate and constituting a part of the photoelectric conversion element;
A second semiconductor region of a first conductivity type disposed on the semiconductor substrate and retaining a charge generated by the photoelectric conversion element;
A third semiconductor region of a first conductivity type disposed on the semiconductor substrate;
A first gate electrode disposed on the semiconductor substrate and transferring the charge of the second semiconductor region to the third semiconductor region;
In a photoelectric conversion device having an element isolation region including at least an insulator part,
The insulator portion is disposed to electrically isolate the second semiconductor region;
A photoelectric conversion device, wherein a lower end of the insulator portion is provided at the same depth as the lower end of the second semiconductor region or at a position deeper than the second semiconductor region. A fourth semiconductor region disposed on a side surface of the insulator portion for reducing dark current from the insulator portion;
The photoelectric conversion device according to claim 1, wherein the fourth semiconductor region is disposed between the second semiconductor region and the insulator portion.   The photoelectric conversion device according to claim 2, wherein the fourth semiconductor region is a second conductivity type opposite to the first conductivity type.   The photoelectric conversion device according to claim 1, wherein the second semiconductor region and the insulator portion are arranged so as to contact each other.   The lower end of the second semiconductor region is a PN junction surface between the second semiconductor region and a second conductivity type fifth semiconductor region disposed under the second semiconductor region. The photoelectric conversion device according to any one of claims 1 to 4.   The photoelectric conversion device according to claim 5, wherein a part of the fifth semiconductor region is disposed at a position shallower than a lower end of the insulator portion.   The photoelectric conversion device according to claim 5, wherein the fifth semiconductor region and the insulator portion are arranged in contact with each other so as to surround the second semiconductor region.   The photoelectric conversion device according to claim 1, wherein a light-shielding body is disposed on the second semiconductor region.   The photoelectric conversion device according to claim 8, wherein the light shielding body is arranged to extend on the insulator portion.   10. The semiconductor device according to claim 1, further comprising a second gate electrode disposed on a region between the first semiconductor region and the second semiconductor region. Photoelectric conversion device.   The photoelectric conversion device according to claim 10, wherein the second gate electrode extends above the second semiconductor region. A plurality of pixels including a first pixel and a second pixel;
Each of the plurality of pixels includes the first to third semiconductor regions and the first gate electrode,
The insulator portion is disposed between the second semiconductor region included in the first pixel and any of the first to third semiconductor regions included in the second pixel. The photoelectric conversion device according to claim 1, wherein: A pixel circuit;
The photoelectric conversion device according to claim 1, wherein the insulator portion is disposed between the second semiconductor region and a transistor included in the pixel circuit. The photoelectric conversion device according to any one of claims 1 to 13,
An image pickup system comprising: a signal processing circuit that processes a signal output from the photoelectric conversion device.

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