JP2007073864A - Line sensor and image information reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a line sensor capable of reading more optically-generated electric charges generated in a photodiode forming region. <P>SOLUTION: The line sensor 4 includes a plurality of light-receiving elements 21 linearly arranged apart at prescribed intervals. Each light-receiving element 21 includes the photodiode forming region PD, where the optically-generated electric charges corresponding to incident light are generated, and a detection transistor for detecting the electric charge amount of the optically-generated electric charges and arranged at the almost center in the photodiode forming region PD. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a line sensor and an image information reading apparatus.

  2. Description of the Related Art Conventionally, solid-state imaging devices include CCD (Charge coupled device) sensors, CMOS sensors, and the like, and line sensors that are solid-state imaging devices are widely used in scanners, copying machines, and the like. The solid-state imaging device has a photodiode that receives light and generates an electric charge, and functions as a photoelectric conversion element. For example, the amount of photogenerated charge generated in a photodiode is charged in a charge transfer unit such as a CCD provided adjacent to one side of a region where the photodiode is formed (hereinafter referred to as a photodiode formation region) via a transfer gate. Transferred. The charge transfer unit transfers the photogenerated charge, and the transferred photogenerated charge is read as an image signal by the reading unit.

Then, a solid-state imaging device for increasing the reading efficiency of photogenerated charges has been proposed (see, for example, Patent Document 1). In the solid-state imaging device according to the proposal, the potential gradient in the photodiode formation region is configured such that the closer to the transfer gate, the deeper the potential well. Since the potential well is deeper as it is closer to the transfer gate, the solid-state imaging device can read out charges in a shorter time, resulting in higher read efficiency.
JP 2002-231926 A

  However, since the readout gate is arranged adjacent to one end of the photodiode formation region, the charge near the end opposite to the end, that is, the charge far away from the transfer gate is transferred to the transfer gate. It takes a long time to reach, and charge that cannot reach the transfer gate is generated. For example, since a device such as a scanner equipped with a line sensor requires high-speed processing, the time until the charge moves to the transfer gate cannot be increased. Therefore, since such residual charges do not contribute to the image reading signal after all, there is a problem that the sensitivity of the line sensor cannot be improved.

  In addition, since the distance to the transfer gate is long, the charge that has not reached the transfer gate remains in the photodiode formation region, causing afterimages and output variations.

  Accordingly, the present invention has been made in view of the above problems, and an object thereof is to provide a line sensor that can read more photogenerated charges generated in a photodiode formation region. .

  A line sensor according to an embodiment of the present invention is a line sensor including a plurality of light receiving elements arranged linearly at a predetermined interval, and each light receiving element generates a photo-generated charge corresponding to incident light. And a detection transistor that detects a charge amount of the photogenerated charge, and the detection transistor is disposed substantially at the center of the photodiode formation region.

In the line sensor according to an embodiment of the present invention, the detection transistor includes a gate electrode, a source region, a drain region, and a storage region, the gate electrode has a ring shape, and the source region is formed of the gate electrode. The drain region is formed inside the gate electrode, the storage region is formed below the gate electrode, and stores the photogenerated charges.
According to such a configuration, it is possible to realize a line sensor that can read more photogenerated charges generated in the photodiode formation region.

In the line sensor according to an embodiment of the present invention, the detection transistor changes a threshold voltage according to the photogenerated charges accumulated in the accumulation region, and outputs a signal based on the threshold voltage.
According to such a configuration, it is possible to realize a line sensor that can read more photogenerated charges generated in the photodiode formation region in the threshold modulation type sensor.

In the line sensor according to an embodiment of the present invention, the photodiode formation region has a potential distribution, and the potential distribution has an impurity profile in which the photogenerated charges easily move toward the substantially center.
According to such a configuration, charges can be efficiently collected from the peripheral portion.

  A line sensor according to an embodiment of the present invention is a line sensor including a plurality of light receiving elements arranged linearly at a predetermined interval, and each light receiving element generates a photo-generated charge corresponding to incident light. A photodiode-forming region, a ring-shaped transfer gate disposed substantially in the center of the photodiode-forming region, and a floating diffusion region disposed inside the transfer gate, wherein the light is controlled by controlling the transfer gate. And a floating diffusion region to which the generated charge is transferred.

In the line sensor according to the embodiment of the present invention, the floating diffusion region outputs a potential based on the transfer amount of the photogenerated charges.
According to such a configuration, it is possible to realize a line sensor that can read more photogenerated charges generated in the photodiode formation region.

In the line sensor according to an embodiment of the present invention, the photodiode formation region has a potential distribution, and the potential distribution has an impurity profile in which the photogenerated charges easily move toward the substantially center.
According to such a configuration, charges can be efficiently collected from the peripheral portion.

An image information reading apparatus according to an embodiment of the present invention is an image information reading apparatus including the line sensor.
According to such a configuration, an image information reading apparatus that requires high-speed processing can be realized.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
First, based on FIG. 1, the structure of the image information reading apparatus which is an electronic device in which the line sensor according to the present embodiment is used will be described. FIG. 1 is a configuration diagram showing the configuration of the image information reading apparatus according to the present embodiment. FIG. 2 is a schematic sectional view for explaining a reading mechanism of the image information reading apparatus shown in FIG.

  As shown in FIG. 1, the image information reading device 1 has a line sensor unit 2. The line sensor unit 2 has a plurality of line sensor chips 4 arranged in a straight line in the longitudinal axis direction of the substrate 3 on an elongated plate-like substrate 3. Each of the plurality of line sensor chips 4 includes a plurality of light receiving elements, and when the plurality of line sensor chips 4 are arranged in a straight line, the plurality of light receiving elements are arranged in a straight line. Is placed on top. The line sensor unit 2 is provided with a plurality of lenses 5. The plurality of lenses 5 are arranged on the line sensor chip 4 so that each lens is located at a position corresponding to each light receiving element of the line sensor chip 4. The plurality of lenses 5 are, for example, a plurality of selfoc lens arrays. Further, the line sensor unit 2 is provided with an elongated lamp 6 as a light source device. An output circuit 7 is provided on the substrate 3 for sequentially outputting image signals from the plurality of line sensor chips 4 to an external image signal processing circuit (not shown).

  A conveyance device (not shown) is provided in the image information reading device 1, and the line sensor unit 2 can be moved in a direction L <b> 1 orthogonal to the longitudinal axis direction of the substrate 3 by the conveyance device. As the line sensor unit 2 moves, the reflection of image information placed on a transparent plate (not shown) such as a glass plate of the image information reading apparatus 1 from the surface of the paper 11 that is a medium to be read. A plurality of line sensor chips 4 arranged in a straight line receive light.

  As shown in FIG. 2, the light from the lamp 6 is reflected on the surface of the paper 11, and the line sensor unit 2 receives the reflected light from the paper 11 through the lens 5 and is received by the line sensor chip 4. It moves along a predetermined direction L1 while maintaining a predetermined distance with respect to the information recording surface. As a result, the line sensor unit 2 can read image information while scanning the paper 11.

  FIG. 3 is a schematic plan view for explaining the configuration of the line sensor chip 4. The line sensor chip 4 has a plurality of light receiving elements 21. The plurality of light receiving elements 21 are formed and arranged on the surface of the line sensor chip 4 in a line, that is, in a straight line, with a predetermined interval. Arranging in a straight line includes not only arranging the light receiving elements in a line but also arranging the light receiving elements in three lines. When the light receiving elements are arranged in three rows, white light is irradiated and read as an RGB sensor.

  Further, the line sensor chip 4 scans and reads out a pixel signal from each light receiving element 21, a timing generator (TG) 22 as a timing signal generating circuit, a drive circuit 23 for driving each light receiving element 21, and The circuit 24 and the amplifier 25 that amplifies and outputs the pixel signal from the scanning circuit 24 are provided. An output signal from the amplifier 25 is supplied to the output circuit 7 described above.

  Therefore, in the image information reading device 1, various control signals from a control unit (not shown) are supplied to the line sensor unit 2 and a transport device (not shown). The line sensor unit 2 that receives the various control signals internally generates a predetermined control signal, drives each line sensor chip 4, reads out and outputs an image signal. As a result, the image information reading apparatus 1 can read the image information on the paper 11.

  Next, the structure of each light receiving element of the line sensor chip 4 will be described. FIG. 4 is a plan view of one light receiving element 21 formed on the line sensor chip 4. FIG. 5 is a cross-sectional view of the light receiving element 21 taken along the line VV in FIG.

  The light receiving element 21 has a square shape formed so that the corners are rounded when viewed from the direction orthogonal to the substrate plane. That is, when viewed from vertically above, the planar shape of the light receiving element is a square shape, and the corners of the square shape are rounded.

  A detection element 31 is formed at a substantially central portion of the rectangular light receiving element 21. In the present embodiment, the detecting element 31 is a threshold modulation type modulation transistor Tm.

  A photodiode is formed in a ring (ring shape) around the modulation transistor formation region TM. In FIG. 4, the region where the photodiode is formed is shown as a photodiode formation region PD.

As shown in FIG. 5, each light receiving element 21 is formed on a P-type substrate 101 a of the substrate 101. In the photodiode formation region PD, an N ⁻ N type well 102 is formed on the P type substrate 101a at a deep position of the substrate. On the other hand, in the modulation transistor formation region TM, an N ⁻ N type well 103 is formed on a P type substrate 101a at a relatively shallow position of the substrate. In FIG. 5 and the description thereof, the subscripts-and + of N and P indicate the state from the lighter portion (subscript-) to the darker portion (subscript ++) depending on the number. . In the present embodiment, holes are used as photogenerated charges.

As shown in FIG. 5, a P-type impurity layer 104 is formed on the N-type well 102 in the photodiode formation region PD and the N-type well 103 in the modulation transistor formation region TM, and the P-type impurity layer 104 is accumulated. Functions as a well. An N ⁺ diffusion layer 105 is formed on the entire surface of the substrate. The N ⁺ diffusion layer 105 is in physical contact with and electrically connected to the N ⁻ N-type well 102.

The N ⁺ diffusion layer 105 is formed for each light receiving element and is separated from the adjacent light receiving elements 21. Specifically, as shown in FIG. 5, the adjacent light receiving elements 21 are separated by a P-type impurity layer of a P-type substrate 101a as the separation layer IS.

The photodiode has a function as a photoelectric conversion element. The photodiode formation region PD includes an N-type well 102 formed below the substrate 101 and a P-type impurity layer 104 formed above the N-type well 102. A depletion region is formed in the boundary region between the N-type well 102 and the P-type impurity layer 104. In this depletion region, photogenerated charges due to light incident through the opening region that receives light from the photodiode formation region PD are generated. Arise. The generated photogenerated charges are accumulated in the P-type impurity layer 104.
The detection element 31 that detects the voltage formed in the modulation transistor formation region TM is a modulation transistor Tm as an amplifying unit, and is, for example, an N-channel depletion MOS transistor. On the N-type well 103 in the modulation transistor formation region TM, a substantially ring-shaped (octagonal in FIG. 4) gate (hereinafter also referred to as a ring gate or simply a gate) 32 is formed on the surface of the substrate 101 via a gate insulating film 110. Is formed. Below the ring gate 32 is an N ⁺ diffusion layer 105 that forms the channel of the modulation transistor Tm.

An N ⁺⁺ diffusion layer is formed on the substrate surface at the center of the opening of the ring gate 32 to form a source region (hereinafter also simply referred to as a source). In the P-type impurity layer 104 on the N-type well 103 in the modulation transistor formation region TM, a ring-shaped floating diffusion region formed by the P ⁺ diffusion formed along the ring shape of the ring gate 32 is used. A carrier pocket 107 in the concentration impurity region is formed. The accumulation well including the P-type impurity layer 104 including the carrier pocket 107 functions as a modulation well. Further, the N ⁺ diffusion layer 105 around the ring gate 32 constitutes a drain region (hereinafter also simply referred to as a drain).

As described above, the modulation transistor Tm includes the ring gate 32, the source region in the center of the ring gate 32, and the drain region around the ring gate 32.
The P-type accumulation well serving as the modulation well controls the channel threshold voltage of the modulation transistor Tm, and the channel threshold voltage changes according to the charge accumulated in the carrier pocket 107.

As shown in FIG. 4, an N ⁺ layer gate contact region 33 is formed near the surface of the substrate 101 at a predetermined position of the ring gate 32. At a predetermined position of the source region, an N ⁺ layer source contact region 34 is formed in the vicinity of the surface of the substrate 101. An N ⁺ layer drain contact region 35 is formed in the vicinity of the surface of the substrate 101 at a predetermined position of the drain region. As shown in FIG. 5, the source contact region 34 is connected to the wiring layer 108, and the drain contact region 35 is connected to the wiring layer 109.

  The source potential of the modulation transistor formation region TM corresponds to the amount of charge transferred to the modulation well, that is, incident light to the photodiode formation region PD that functions as a photodiode.

  In particular, the P-type impurity layer 104 has a rectangular shape with rounded corners when viewed from a direction orthogonal to the surface of the substrate 101. As shown by a dotted line in FIG. Is formed so as to increase from the peripheral portion toward the central portion of the rectangular P-type impurity layer 104. Specifically, the concentration level of the P-type impurity is three levels, the central region 104a has a higher concentration than the peripheral region 104c, and the intermediate region 104b has a concentration of the central region 104a and the peripheral region 104c. Is a concentration between

  The P-type impurity layer 104 having such a concentration difference can be formed, for example, by performing impurity implantation by ion implantation in three times. In that case, the first ion implantation is performed on the whole including the outer peripheral region 104c, the second is performed on the inner side including the intermediate region 104c, and the third is performed only on the central region 104a. Against.

The density level is 3 levels in the present embodiment, but may be 2 levels or 4 levels or more. According to such a configuration, charges can be efficiently collected from the peripheral portion.
Therefore, the concentration gradient of the P-type impurity described above is concentric with the shape of the photodiode formation region PD and the shape of the ring gate 32 constituting the detection element.

Various wiring layers are formed on the substrate surface via an interlayer insulating film (not shown) and connected to the above-described wiring 108 and the like.
Furthermore, the concentration level may be one level, that is, the concentration may be the same from the peripheral portion of the P-type impurity layer 104 toward the central portion. Even if there is no concentration gradient in the P-type impurity layer 104, the carrier pocket 107 exists, so that a potential gradient exists toward the carrier pocket 107.

  FIG. 6 is a diagram for explaining the potential of the line sensor according to the present embodiment. FIG. 6 shows a cross section of the light receiving element 21 in the upper part and shows a potential diagram corresponding to the cross section in the lower part.

  As shown in FIG. 6, the potential decreases from the peripheral part of the P-type impurity layer 104 toward the central part according to the impurity concentration difference of the peripheral region 104c, the intermediate region 104b, and the central region 104a. The potential is lowest at the carrier pocket 107 in the impurity region. Since the photodiode formation region PD has such a potential gradient, it is easy to move the photogenerated charges to the carrier pocket 107.

An operation example of the light receiving element 21 according to such a configuration will be described.
First, in the light receiving element 21, a reset operation is performed by applying a high voltage to the ring gate 32 and sweeping out charges in the P-type impurity layer 104 as an accumulation well through the P-type substrate 101a.

  Immediately after the reset operation, since there is no charge in the storage well, the output voltage of the modulation transistor Tm when the storage well is empty is detected. This output voltage detection operation is a noise component detection operation.

  Next, if light hits the photodiode formation region PD of the light receiving element 21, photogenerated charges are generated in the P-type impurity layer 104. The generation of this charge is continued for a predetermined time, and this period becomes an accumulation period.

During the accumulation period, photogenerated charges corresponding to the amount of light are held in the P-type impurity layer 104. The modulation transistor Tm is equivalent to the change of the back gate bias by holding the charge in the P-type impurity layer 104, and the channel threshold voltage changes according to the amount of charge in the P-type impurity layer 104. . As a result, the output voltage of the modulation transistor Tm becomes a voltage corresponding to the amount of charge in the P-type impurity layer 104, that is, a voltage indicating the amount of light received by the photodiode formation region PD. This voltage detection operation is a signal component detection operation.
The voltage signal of the noise component and the voltage signal of the signal component are sampled and held by a sample hold circuit (not shown), stored in a capacitor, and compared. Therefore, a light receiving element of a line sensor having a so-called CDS function is realized.

  As described above, in the light receiving element 21 according to the present embodiment, the detection element is formed at the center of the photodiode formation region PD. Therefore, the distance of the photogenerated charge generated in the photodiode formation region PD to the detection element. Can be halved compared to the prior art.

  Therefore, according to the above-described line sensor, each detection element is provided in the center of each photodiode formation region, so that the photo-generated charges generated in the photodiode formation region are likely to gather in the detection element in the substantially center. Therefore, each detection element can read more photogenerated charges, and as a result, the sensitivity of the line sensor is improved.

(Second Embodiment)
In the first embodiment, the detection element detects the amount of received light by using a change in the threshold voltage of the channel of the modulation transistor Tm. In the second embodiment, the detection element is included in the impurity layer. The difference from the first embodiment is that a potential based on the accumulated charge amount is supplied to the gate of the amplification transistor. An example of a line sensor that uses the configuration according to the second embodiment is a CMOS sensor. Since the light receiving element according to the present embodiment can also be applied to the image information reading apparatus shown in FIGS. 1 and 2, the description of the image information reading apparatus is omitted.

  FIG. 7 is a plan view of one light receiving element 121 on the line sensor chip 4 and a detection circuit according to the present embodiment. FIG. 8 is a cross-sectional view of the light receiving element 121 along the line VIII-VIII in FIG.

  The light receiving element 121 has a square shape formed so that the corners are rounded when viewed from a direction orthogonal to the substrate plane. A floating diffusion region FD is formed at the center of the rectangular light receiving element 121. A photodiode formation region PD is formed in a ring shape around the floating diffusion region FD.

  A contact region 134 is provided at the center of the floating diffusion region FD, and the contact region 134 is connected to the source of the reset transistor TRS and the gate of the amplification transistor TA via the wiring layer 208 (FIG. 8). . The reset transistor TRS and the amplification transistor TA are formed outside the photodiode formation region PD.

As shown in FIG. 8, each light receiving element 121 is formed on a P-type substrate 201a. On the P-type substrate 201a in the photodiode formation region PD, an N ⁻ N-type impurity layer 204 is formed in a ring shape. On the other hand, an N ⁺ N-type impurity layer 203 serving as a floating diffusion is formed on the P-type substrate 201a in the floating diffusion formation region FD. In FIG. 8 and the description thereof, the subscripts-and + of N and P indicate the state from the lighter portion (subscript-) to the darker portion (subscript ++) depending on the number. . In the present embodiment, electrons are used as photogenerated charges.

As shown in FIG. 8, the substrate surface of the photodiode forming region PD of the N-type impurity layer 204, P ⁺ diffusion layer 205 is formed. The P ⁺ diffusion layer 205 is in physical contact with the P-type substrate 201a and is electrically connected.

The P ⁺ diffusion layer 205 is formed for each light receiving element, and is formed so as to separate the adjacent light receiving elements 121 from each other. Specifically, as shown in FIG. 8, adjacent light receiving elements 121 are separated from each other by a P-type impurity layer of a P-type substrate 201a serving as an isolation layer IS.

A depletion region is formed in the boundary region between the substrate 201a and the N-type impurity layer 204 below the photodiode formation region PD having the function of the photoelectric conversion element. In this depletion region, an opening for receiving light from the photodiode formation region PD is formed. Photogenerated charges are generated by light incident through the region. The generated photogenerated charge is accumulated in the N-type impurity layer 204.
When viewed from the direction orthogonal to the substrate surface, a substantially ring-shaped (octagonal in FIG. 7) gate (hereinafter referred to as a ring gate or simply a gate) is formed on the surface of the substrate 201a via the gate insulating film 210 so as to surround the floating diffusion region FD. 132) is also formed.

  The ring gate 132 functions as a transfer gate that transfers the photogenerated charges held in the N-type impurity layer 204 to the N-type impurity layer 203 on the substrate surface. Therefore, the floating diffusion region FD and the ring gate 132 constitute a detection element 131 that detects the potential of the floating diffusion region FD and supplies it to the gate of the amplification transistor TA. The detection element 131 is provided at the center of the photodiode formation region PD so as to be surrounded by the photodiode formation region PD.

Various wiring layers are formed on the substrate surface via an interlayer insulating film (not shown) and connected to the above-described wiring 208 and the like.
With such a configuration, a potential based on the amount of charge accumulated in the N-type impurity layer 204 can be supplied to the gate of the amplification transistor TA.

An example of the operation of the light receiving element 121 having such a configuration will be described.
First, the reset operation is performed by applying a predetermined voltage to the ring gate 132 and sweeping out the remaining charges in the N-type impurity layer 203. Immediately after the reset operation, the potential of the N-type impurity layer 203 is fixed to the reset voltage. Since the gate potential of the amplification transistor TA changes according to the floating diffusion region FD, the output VOUT of the amplification transistor TA is an output corresponding to the potential when there is no charge in the floating diffusion region FD, that is, an output corresponding to the noise component. Become. This output detection operation is a noise component detection operation.

  Next, if light hits the photodiode formation region PD of the light receiving element 121, photogenerated charges are generated in the N-type impurity layer 204. The generation of this charge is continued for a predetermined time, and this period becomes an accumulation period.

  During the accumulation period, photogenerated charges corresponding to the amount of light are held in the N-type impurity layer 204. The charges held in the N-type impurity layer 204 are transferred to the N-type impurity layer 203 by applying a high predetermined voltage to the ring gate 132. By this transfer operation, charges move in the N-type impurity layer 203. Since the gate potential of the amplifying transistor TA changes according to the amount of charge that has moved, the output VOUT of the amplifying transistor TA is an output that corresponds to the potential due to the amount of charge in the floating diffusion region FD, that is, the signal component. . This output detection operation is a signal component detection operation.

  The voltage signal of the noise component and the voltage signal of the signal component are sampled and held by a sample hold circuit (not shown), stored in a capacitor, and compared. Therefore, a light receiving element of a line sensor having a so-called CDS function is realized.

  As described above, according to the above-described line sensor, each detection element is provided in the approximate center of the respective photodiode formation region, so that the photo-generated charges generated in the photodiode formation region are substantially in the center of the detection element. Therefore, each detection element can read more photogenerated charges, and as a result, the sensitivity of the line sensor is improved.

  In the two embodiments described above, the detection element is provided in the central portion of the photodiode formation region. However, from the intent of the present invention, the detection element is not necessarily a complete central portion. What is necessary is just to be provided in the center part.

  The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the scope of the present invention.

1 is a configuration diagram showing a configuration of an image information reading apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic sectional view for explaining a reading mechanism of the image information reading apparatus shown in FIG. 1. FIG. 3 is a schematic plan view of the line sensor chip according to the first embodiment. FIG. 3 is a plan view of the light receiving element according to the first embodiment. Sectional drawing of the light receiving element along the VV line of FIG. The figure for demonstrating the potential of the line sensor which concerns on 1st Embodiment. FIG. 6 is a plan view of a light receiving element and a detection circuit according to a second embodiment of the present invention. Sectional drawing of the light receiving element along the VIII-VIII line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image reader, 2 Line sensor unit, 3 Substrate, 4 Line sensor chip, 5 Lens, 6 Lamp, 7 Output circuit, 11 Paper, 21, 121 Light receiving element, 22 Timing generator, 23 Drive circuit, 24 Scan circuit, 25 Amplifier, 31, 131 Detection element, 32, 132 Ring gate

Claims (8)

A line sensor including a plurality of light receiving elements arranged in a straight line at a predetermined interval,
Each light receiving element
A photodiode forming region for generating photogenerated charges in response to incident light;
A detection transistor for detecting a charge amount of the photogenerated charge, wherein the detection transistor is disposed substantially at the center of the photodiode formation region;
Including line sensor. The detection transistor has a gate electrode, a source region, a drain region, and a storage region,
The gate electrode has a ring shape;
The source region is formed inside the gate electrode;
The drain region is formed outside the gate electrode;
The line sensor according to claim 1, wherein the accumulation region is formed below the gate electrode and accumulates the photogenerated charges. The line sensor according to claim 1, wherein the detection transistor changes a threshold voltage according to the photogenerated charge accumulated in the accumulation region, and outputs a signal based on the threshold voltage. . The photodiode formation region has a potential distribution;
The line sensor according to any one of claims 1 to 3, wherein the potential distribution has an impurity profile in which the photogenerated charges easily move toward the substantially center. A line sensor including a plurality of light receiving elements arranged in a straight line at a predetermined interval,
Each light receiving element
A photodiode forming region for generating photogenerated charges in response to incident light;
A ring-shaped transfer gate disposed substantially in the center of the photodiode forming region;
A floating diffusion region disposed inside the transfer gate, wherein the photo-generated charge is transferred by control of the transfer gate;
Including line sensor.   The line sensor according to claim 5, wherein the floating diffusion region outputs a potential based on a transfer amount of the photogenerated charges. The photodiode formation region has a potential distribution;
The line sensor according to any one of claims 5 to 6, wherein the potential distribution has an impurity profile in which the photogenerated charges easily move toward the substantially center.   An image information reading apparatus including the line sensor according to claim 1.

Images