JP2012083214A - Distance sensor and distance image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distance sensor and a distance image sensor which achieve high sensitivity.SOLUTION: An electric charge generation region is arranged in a first region R1 which has a rectangular shape and extends in a first direction D1. Signal electric charge regions are provided in two respective sides R1a, R1b extending in a direction D1 in the first region R1 so as to oppose to each other in a direction orthogonal to the first direction D1, and are arranged such that at least a part of the signal electric charge region is included in a plurality of second regions R2 which overlaps with the first region R1. A transfer electrode is placed between the electric charge generation region and the signal electric charge region in the second region R2 and has a part extending along the periphery of the second region R2. The periphery of the electric charge generation region extends along the periphery of the second region R2.

Description

  The present invention relates to a distance sensor and a distance image sensor.

  A conventional active optical distance measuring sensor irradiates light from a light source for light projection such as an LED (Light Emitting Diode), and detects reflected light from the object with a light detection element. It is known to output a signal corresponding to the distance up to. A PSD (Position Sensitive Detector) is known as an optical triangulation type optical distance measuring sensor that can easily measure the distance to an object, but in recent years, in order to perform more precise distance measurement, The development of TOF (Time-Of-Flight) type optical ranging sensor is expected.

  Image sensors that can simultaneously acquire distance information and image information with the same chip are required for in-vehicle use, factory automatic manufacturing systems, and the like. If an image sensor is installed in front of the vehicle, it is expected to be used for detection / recognition of the vehicle ahead and detection / recognition of pedestrians. Apart from image information, an image sensor that acquires a distance image composed of a single distance information or a plurality of distance information is also expected. It is preferable to use the TOF method for such a distance measuring sensor.

  The TOF method emits pulsed light from a light source for projection toward an object, and detects the pulsed light reflected by the object with a light detection element, thereby making the time difference between the emission timing of the pulsed light and the detection timing. Is measuring. This time difference (Δt) is the time required for the pulsed light to fly at the speed of light (= c) twice as much as the distance d to the object (2 × d), so d = (c × Δt) / 2 is established. The time difference (Δt) can be rephrased as the phase difference between the emission pulse from the light source and the detection pulse. If this phase difference is detected, the distance d to the object can be obtained.

  The charge distribution type image sensor has attracted attention as a light detection element for performing distance measurement by the TOF method. That is, in the charge distribution type image sensor, for example, the charge generated in the image sensor in response to the incident detection pulse is distributed in one potential well during the ON period of the emission pulse, and OFF. Distribute to the other potential well during the period. In this case, the ratio of the amount of charge distributed to the left and right is proportional to the phase difference between the detection pulse and the emission pulse, that is, the time required for the pulsed light to fly at the speed of light over twice the distance to the object. It will be. Various methods can be considered as the charge distribution method.

  Patent Document 1 discloses a charge generation region in which charges are generated in response to incident light, a plurality of signal charge collection regions that are spatially separated and collect signal charges from the charge generation region, and signal charge collection There is disclosed a TOF type distance sensor (distance image sensor) provided with a transfer electrode provided in each region and provided with a charge transfer signal having a different phase.

JP 2009-8537 A

  In the distance sensor (distance image sensor) as described above, when the object is located at a long distance, the light reflected by the object is weak and the distance detection accuracy is lowered. In addition, regarding the distance detection of an object having a low reflectance, the light reflected by the object is weak, so that the distance detection accuracy is lowered. For this reason, in the TOF type distance sensor (distance image sensor), high sensitivity is desired in order to improve the distance detection accuracy.

  An object of this invention is to provide the distance sensor and distance image sensor which can achieve high sensitivity.

  The distance sensor according to the present invention includes a charge generation region in which charges are generated according to incident light, a plurality of signal charge collection regions that are spatially separated and collect signal charges from the charge generation region, and a signal And a transfer electrode provided to each of the charge collection regions and to which a charge transfer signal having a different phase is applied, and the charge generation region has a rectangular shape and is disposed in the first region extending in the first direction. The signal charge collection region is provided on each of the two sides extending in the first direction of the first region so as to face each other in a direction orthogonal to the first direction and overlaps with the first region. The transfer electrode is disposed so as to be at least partially included in the second region, and the transfer electrode is positioned between the charge generation region and the signal charge collection region in the second region, and at the edge of the second region. With a portion extending along the charge Raw region is characterized in that its edges are extended along the edge of the second region.

  In the distance sensor according to the present invention, since the transfer electrode is located between the charge generation region and the signal charge collection region in the second region, the transfer electrode is in the first region where the charge generation region is disposed. It will be arranged so as to enter. Further, the transfer electrode has a portion extending along the edge of the second region (the edge facing the charge generation region). For this reason, in the present invention, per unit length in the first direction, compared to a distance sensor that employs a configuration in which the transfer electrode is arranged outside the first region so as to extend along the first direction. The light utilization efficiency of Therefore, the area of the charge generation region can be increased and high sensitivity can be achieved.

  Since the transfer electrode has a portion extending along the edge of the second region, the distance sensor adopting a configuration in which the transfer electrode is arranged outside the first region so as to extend along the first direction. As compared with the case, the electrode length becomes longer and the electrode area becomes larger. For this reason, the charge generated in the charge generation region is easily moved, and the charge transfer efficiency is improved. Also from this, the sensitivity of the distance sensor can be increased.

By the way, the charge (Q) transferred to the signal charge collection region generates a voltage change (ΔV) represented by the following relational expression by the electrostatic capacity (Cfd) of the signal charge collection region.
ΔV = Q / Cfd
In the present invention, since the signal charge collection region is arranged so that at least a part thereof is included in the second region overlapping the first region, the edge of the signal charge collection region is a charge in plan view. It will be arranged so as to be surrounded by the generation area. For this reason, the area of the signal charge collection region is relatively reduced with respect to the area of the region where the charge can be transferred to the signal charge collection region in the charge generation region. When the area of the signal charge collection region is reduced, the capacitance of the signal charge collection region is also reduced, and the generated voltage change is increased. That is, the charge voltage conversion gain is increased. Also from this, the sensitivity of the distance sensor can be increased.

  The second region includes two sides whose edges extend in a direction intersecting the first direction, or an arc, and the signal charge collection region is along two sides whose edges are included in the edge of the second region. The transfer electrode includes two sides or arcs extending along the arc included in the edge of the second region, and the transfer electrode has a portion extending along the two sides or arc included in the edge of the second region. The charge generation region may include two sides whose edges extend along two sides included in the edge of the second region, or an arc that extends along an arc included in the edge of the second region. .

  The charge generation region may include a side whose edge extends in the first direction between the second regions adjacent to each other in the first direction. In this case, since the area where charges can be transferred to the signal charge collection area in the charge generation area is expanded, the area of the signal charge collection area is further reduced relative to the area of the area. Therefore, the capacitance of the signal charge collection region is reduced, and the generated voltage change is further increased. As a result, the sensitivity of the distance sensor can be further increased.

  The plurality of signal charge collection regions include first and second signal charge collection regions, and the first signal charge collection region is provided on the first side extending in the first direction of the first region. The second signal charge collection region may be disposed in the second region provided on the second side extending in the first direction of the first region.

  The plurality of signal charge collection regions include first and second signal charge collection regions, and the first and second signal charge collection regions are on the first side extending in the first direction of the first region. You may arrange | position to the different 2nd area | region provided.

  A plurality of unnecessary charge collection regions that are arranged spatially separated and collect unnecessary charges from the charge generation region, and selectively block and release the flow of unnecessary charges from the charge generation region to the unnecessary charge collection region. An unnecessary charge collection gate electrode, and the unnecessary charge collection region is at least partially included in the second region provided on the second side extending in the first direction of the first region. It may be arranged as follows. In this case, accumulation of unnecessary charges in each signal charge collection region is suppressed. For this reason, the distance detection accuracy in the distance sensor can be improved.

  The first and second signal charge collection regions may be arranged in different second regions provided on the second side extending in the first direction of the first region.

  A plurality of unnecessary charge collection regions that are arranged spatially separated and collect unnecessary charges from the charge generation region, and selectively block and release the flow of unnecessary charges from the charge generation region to the unnecessary charge collection region. An unnecessary charge collecting gate electrode, and the unnecessary charge collecting region is arranged so that at least a part is included in the second region provided on the first and second sides of the first region. May be. In this case, accumulation of unnecessary charges in each signal charge collection region is suppressed. For this reason, the distance detection accuracy in the distance sensor can be improved.

  The edge of the unnecessary charge collection region includes a side extending along the side included in the edge of the second region, and the unnecessary charge collection gate electrode is located between the charge generation region and the unnecessary charge collection region in the second region. And may extend along the edge of the second region. In this case, unnecessary charges can be efficiently discharged.

  A distance image sensor according to the present invention includes the distance sensor, a light source, a drive circuit that provides a pulse drive signal to the light source, and a control that applies charge transfer signals having different phases to the transfer electrode in synchronization with the pulse drive signal. A circuit and an arithmetic circuit for calculating a distance to the object from a signal read from the signal charge collection region are provided.

  Since the distance image sensor according to the present invention includes the distance sensor, high sensitivity can be achieved.

  ADVANTAGE OF THE INVENTION According to this invention, the distance sensor and distance image sensor which can achieve high sensitivity can be provided.

It is explanatory drawing which shows the structure of a distance measuring device. It is a figure for demonstrating the cross-sectional structure of a distance image sensor. It is a schematic plan view of a distance image sensor. It is a schematic diagram for demonstrating the structure of the pixel of a distance image sensor. It is a figure which shows the cross-sectional structure along the VV line in FIG. It is a figure which shows the cross-sectional structure along the VI-VI line in FIG. It is a figure which shows potential distribution in the surface vicinity of a semiconductor substrate. It is a figure which shows potential distribution in the surface vicinity of a semiconductor substrate. It is a schematic diagram for demonstrating the structure of a pixel. It is a schematic diagram for demonstrating the structure of the pixel of the distance image sensor as a comparative example. It is a schematic diagram for demonstrating the structure of the pixel of the distance image sensor as a comparative example. It is a schematic diagram for demonstrating the structure of the pixel of the distance image sensor which concerns on a 1st modification. It is a figure which shows the cross-sectional structure along the XIII-XIII line | wire in FIG. It is a schematic diagram for demonstrating the structure of the pixel of the distance image sensor which concerns on a 2nd modification. It is a schematic diagram for demonstrating the structure of the pixel of the distance image sensor which concerns on a 3rd modification. It is a figure which shows the cross-sectional structure along the XVI-XVI line | wire in FIG. It is a schematic diagram for demonstrating the structure of the pixel of the distance image sensor which concerns on a 4th modification. It is a schematic diagram for demonstrating the structure of the pixel of the distance image sensor which concerns on a 5th modification. It is a figure which shows the cross-sectional structure along the XIX-XIX line | wire in FIG. It is a figure which shows the cross-sectional structure along the XX-XX line in FIG. It is a figure which shows potential distribution in the surface vicinity of a semiconductor substrate. It is a figure which shows potential distribution in the surface vicinity of a semiconductor substrate. It is a timing chart of actual various signals. It is a timing chart which shows the modification of various signals. It is a schematic diagram for demonstrating the structure of the pixel of the distance image sensor which concerns on a 6th modification. It is a schematic diagram for demonstrating the structure of the pixel of the distance image sensor which concerns on a 7th modification. It is a schematic diagram for demonstrating the structure of the pixel of the distance image sensor which concerns on an 8th modification. It is a schematic diagram for demonstrating the structure of the pixel of the distance image sensor which concerns on a 9th modification. It is a figure which shows the cross-sectional structure along the XXIX-XXIX line | wire in FIG. It is a figure which shows the cross-sectional structure along the XXX-XXX line in FIG. It is a schematic diagram for demonstrating the structure of the pixel of the distance image sensor which concerns on a 10th modification. It is a schematic diagram for demonstrating the structure of the pixel of the distance image sensor which concerns on an 11th modification.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  FIG. 1 is an explanatory diagram showing the configuration of the distance measuring apparatus.

The distance measuring device, a distance image sensor 1, a light source 3 for emitting near-infrared light, a driving circuit 4 to be supplied to the light source 3 a pulse drive signal S _P, first included in each pixel of the range image sensor 1 and a second gate electrode (TX1, TX2: see FIG. 4), the pulsed driving signal _S and the control circuit 2 to provide a detection gate signals _S 1, _{S 2} in synchronization with the _P, the distance the first and second image sensors 1 An arithmetic circuit 5 is provided that calculates a distance from a signal d ′ (m, n) indicating distance information read from the semiconductor region (FD1, FD2: see FIG. 4) to an object H such as a pedestrian. . The distance in the horizontal direction D from the distance image sensor 1 to the object H is defined as d.

The control circuit 2 is input to the pulse drive signal S _P to the switch 4b of the driving circuit 4. A light projecting light source 3 comprising an LED or a laser diode is connected to a power source 4a via a switch 4b. Therefore, when the pulse drive signal S _P is input to the switch 4b, a drive current having the same waveform as the pulse drive signal S _P is supplied to the light source 3, the pulse light L _P as a probe light for distance measurement from the light source 3 Is output.

When the pulse light L _P is irradiated on the object H, the pulse light is reflected by the object H, the pulse light L _D, the distance is incident on the image sensor 1 outputs a pulse detection signal S _D.

  The distance image sensor 1 is fixed on the wiring board 10, and a signal d ′ (m, n) having distance information is output from each pixel via the wiring on the wiring board 10.

The waveform of the pulse drive signal S _P, a square wave of period T, the high level "1", when the low level is "0", the voltage V (t) is given by the following equation.
Pulse drive signal S _P :
V (t) = 1 (provided that 0 <t <(T / 2))
V (t) = 0 (provided that (T / 2) <t <T)
V (t + T) = V (t)

The waveforms of the detection gate signals S ₁ and S ₂ are square waves having a period T, and the voltage V (t) is given by the following equation.
Detection gate signal S ₁ :
V (t) = 1 (provided that 0 <t <(T / 2))
V (t) = 0 (provided that (T / 2) <t <T)
V (t + T) = V (t)
Detection gate signal S ₂ (= inversion of S ₁ ):
V (t) = 0 (provided that 0 <t <(T / 2))
V (t) = 1 (provided that (T / 2) <t <T)
V (t + T) = V (t)

The pulse signal _{S P, S 1, S 2} , S D , it is assumed that has all pulse period 2 × _{T P.} Detection gate signal S ₁ and the pulse detection signal S _D are both the amount of charge generated by the distance image sensor within 1 when "1" Q1, the detection gate signal S ₂ and the pulse detection signal S _D are both "1" In this case, the amount of charge generated in the distance image sensor 1 is Q2.

The phase difference between _one detection gate signal S ₁ and the pulse detection signal _{SD in} the distance image sensor 1 is the distance in the overlap period when the other detection gate signal S ₂ and the pulse detection signal _SD are “1”. It is proportional to the amount of charge Q2 generated in the image sensor 1. That is, the charge amount Q2 is the charge amount for the period logical product of the detection gate signal S ₂ and the pulse detection signal S _D is "1". The total charge quantity generated in one pixel is Q1 + Q2, when the pulse width of the half cycle of the drive signal _{S P} and _{T P, Δt = T P ×} Q2 / (Q1 + Q2) long enough, with respect to the drive signal _{S P} The pulse detection signal _SD is delayed. The flight time Δt of one pulsed light is given by Δt = 2d / c, where d is the distance to the object and c is the speed of light. Therefore, two charges are used as a signal d ′ having distance information from a specific pixel. If the amount (Q1, Q2) are output, the arithmetic circuit 5, a charge amount Q1, Q2 input, based on the half cycle pulse width T _P that is known in advance, the distance to the object H d = Calculate (c × Δt) / 2 = c × _TP × Q2 / (2 × (Q1 + Q2)).

  As described above, if the charge amounts Q1 and Q2 are read out separately, the arithmetic circuit 5 can calculate the distance d. The above-described pulse is repeatedly emitted, and the integrated value can be output as the respective charge amounts Q1 and Q2.

  The ratio of the charge amounts Q1 and Q2 to the total charge amount corresponds to the above-described phase difference, that is, the distance to the object H. The arithmetic circuit 5 calculates the distance to the object H according to this phase difference. As described above, when the time difference corresponding to the phase difference is Δt, the distance d is preferably given by d = (c × Δt) / 2, but an appropriate correction operation may be added to this. . For example, when the actual distance and the calculated distance d are different, a coefficient β for correcting the latter is obtained in advance, and the product after shipping is obtained by multiplying the calculated distance d by the coefficient β. The calculation distance d may be used. When the outside air temperature is measured and the light speed c varies depending on the outside air temperature, the distance calculation can be performed after performing the calculation for correcting the light speed c. The relationship between the signal input to the arithmetic circuit and the actual distance may be stored in advance in the memory, and the distance may be calculated by a lookup table method. The calculation method can also be changed depending on the sensor structure, and a conventionally known calculation method can be used for this.

  FIG. 2 is a diagram for explaining a cross-sectional configuration of the distance image sensor.

  The distance image sensor 1 includes a semiconductor substrate 1A. The semiconductor substrate 1A has a reinforcing frame portion F and a thin plate portion TF thinner than the frame portion F, and these are integrated. The thickness of the thin plate portion TF is 10 μm or more and 100 μm or less. The thickness of the frame portion F in this example is 200 μm or more and 1000 μm or less. The entire semiconductor substrate 1A may be thinned. The pulsed light LD is incident on the distance image sensor 1 from the light incident surface 1BK. A surface 1FT opposite to the light incident surface 1BK of the distance image sensor 1 is connected to the wiring substrate 10 via an adhesion region AD. The adhesion region AD is a region including an adhesion element such as a bump electrode, and has an insulating adhesive or filler as necessary.

  FIG. 3 is a schematic plan view of the distance image sensor.

  In the distance image sensor 1, the semiconductor substrate 1A has an imaging region 1B composed of a plurality of pixels P (m, n) arranged in a two-dimensional manner. From each pixel P (m, n), two charge amounts (Q1, Q2) are output as the signal d '(m, n) having the above-described distance information. Each pixel P (m, n) outputs a signal d '(m, n) corresponding to the distance to the object H as a minute distance measuring sensor. Therefore, if the reflected light from the object H is imaged on the imaging region 1B, a distance image of the object as a collection of distance information to each point on the object H can be obtained. One pixel P (m, n) functions as one distance sensor.

  FIG. 4 is a schematic diagram for explaining the configuration of the pixels of the distance image sensor. FIG. 5 is a diagram showing a cross-sectional configuration along the line VV in FIG. FIG. 6 is a diagram showing a cross-sectional configuration along the line VI-VI in FIG.

The distance image sensor 1 includes a photogate electrode PG and a plurality of first and second gate electrodes TX1 and TX2 (transfer electrodes) provided on the semiconductor substrate 1A in each pixel P (m, n), respectively. A plurality of first and second semiconductor regions FD1 and FD2 (signal charge collection regions). The semiconductor substrate 1A has a light incident surface 1BK and a surface 1FT opposite to the light incident surface 1BK. The photogate electrode PG is provided on the surface 1FT via the insulating layer 1E. The first and second gate electrodes TX1, TX2 are provided adjacent to the photogate electrode PG via the insulating layer 1E on the surface 1FT. The first and second semiconductor regions FD1 and FD2 accumulate charges that flow into regions immediately below the gate electrodes TX1 and TX2. The semiconductor substrate 1A of the present embodiment is made of Si, the insulating layer 1E is made of SiO _2. The semiconductor substrate 1A may be made of an epitaxial layer.

  The photogate electrode PG is disposed in the first region R1. The first region R1 has a rectangular shape and extends in the first direction D1. In the present embodiment, a region corresponding to the photogate electrode PG in the semiconductor substrate 1A (a region immediately below the photogate electrode PG) functions as a charge generation region (photosensitive region) in which charges are generated according to incident light. The photogate electrode PG is made of polysilicon, but other materials may be used.

  The first and second semiconductor regions FD1, FD2 are disposed in different second regions R2, respectively. A plurality of second regions R2 are provided on each of the two sides R1a and R1b extending in the first direction D1 of the first region R1. The second regions R2 disposed on the sides R1a and R1b of the first region R1 are arranged at a predetermined pitch in the first direction D1.

  The second region R2 provided on the side R1a side of the first region R1 and the second region R2 provided on the side R1b side of the first region R1 are perpendicular to the first direction D1. Are facing each other. That is, the second region R2 provided on the side R1a side of the first region R1 and the second region R2 provided on the side R1b side of the first region R1 are in the first direction D1. The positions are the same. Each second region R2 is located in the first region R1 and overlaps with the first region R1. In the present embodiment, the second region R2 has a rectangular shape.

  The photogate electrode PG includes a side PGa whose edge extends along the edge of the second region R2. That is, the photogate electrode PG is provided so as to avoid the second region R2. The second region R2 is surrounded by the photogate electrode PG in plan view. Specifically, the second region R2 is surrounded by the photogate electrode PG over three or two sides included in the edge of the second region R2. Two opposite sides among the three sides included in the edge of the second region R2 extend in a direction intersecting the first direction D1 (a direction orthogonal in the present embodiment).

  The first and second semiconductor regions FD1, FD2 are different second regions R2 provided on the side R1a side of the first region R1 and different second regions provided on the side R1b side of the first region R1. And the region R2. In the present embodiment, the entire first and second semiconductor regions FD1, FD2 are included in the corresponding second region R2.

  The first and second semiconductor regions FD1 and FD2 are spatially separated and alternately arranged along the first direction D1. The first and second semiconductor regions FD1, FD2 are also arranged so as to face each other in a direction orthogonal to the first direction D1. That is, the first semiconductor region FD1 and the second semiconductor region FD2 are arranged so as to sandwich the photogate electrode PG in a direction parallel to and perpendicular to the first direction D1.

  The first semiconductor region FD1 includes sides FD1a, FD1b, and FD1c whose edges extend along the edge of the second region R2 (the side included in the edge). The two sides FD1a and FD1b at the edge of the first semiconductor region FD1 extend in a direction intersecting the first direction D1 (a direction orthogonal in the present embodiment). In the present embodiment, the first semiconductor region FD1 has a rectangular shape.

  The second semiconductor region FD2 includes sides FD2a, FD2b, and FD2c whose edges extend along the edge of the second region R2 (the side included in the edge). The two sides FD2a and FD2b at the edge of the second semiconductor region FD2 extend in a direction intersecting the first direction D1 (a direction orthogonal in the present embodiment). In the present embodiment, the second semiconductor region FD2 has a rectangular shape.

  The first gate electrode TX1 is located between the photogate electrode PG and the first semiconductor region FD1 in the second region R2. For this reason, the first gate electrode TX1 is disposed so that the entirety thereof enters the first region R1. The first gate electrode TX1 includes a portion TX1a extending along the side FD1a of the first semiconductor region FD1, a portion TX1b extending along the side FD1b of the first semiconductor region FD1, and a side FD1c of the first semiconductor region FD1. And an extending portion TX1c. That is, the first gate electrode TX1 has portions TX1a, TX1b, TX1c extending along the three sides included in the edge of the second region R2. The first gate electrode TX1 located at both ends in the first direction D1 has either the part TX1a or the part TX1b and the part TX1c.

  The second gate electrode TX2 is located between the photogate electrode PG and the second semiconductor region FD2 in the second region R2. For this reason, the second gate electrode TX2 is arranged so that the entirety thereof enters the first region R1. The second gate electrode TX2 includes a portion TX2a extending along the side FD2a of the second semiconductor region FD2, a portion TX2b extending along the side FD2b of the second semiconductor region FD2, and a side FD2c of the second semiconductor region FD2. An extending portion TX2c. That is, the second gate electrode TX2 also has portions TX2a, TX2b, TX2c extending along the three sides included in the edge of the second region R2. The second gate electrode TX2 located at both ends in the first direction D1 has either the part TX2a or the part TX2b and the part TX2c.

  The electrode lengths and electrode areas of the first and second gate electrodes TX1, TX2 are set to be the same. The first and second gate electrodes TX1 and TX2 are made of polysilicon, but other materials may be used.

The semiconductor substrate 1A is a p-type semiconductor substrate having a low impurity concentration, and the first and second semiconductor regions FD1 and FD2 are floating diffusion regions made of an n-type semiconductor having a high impurity concentration. The thickness / impurity concentration of each semiconductor region is as follows.
Semiconductor substrate 1A: thickness 10 to 1000 μm / impurity concentration 1 × 10 ¹² to 10 ¹⁵ cm ⁻³
Semiconductor regions FD1 and FD2: thickness 0.1 to 1 μm / impurity concentration 1 × 10 ¹⁸ to 10 ²⁰ cm ⁻³

  The insulating layer 1E is provided with contact holes for exposing the surfaces of the first and second semiconductor regions FD1, FD2. A conductor 11 for connecting the first and second semiconductor regions FD1, FD2 to the outside is disposed in the contact hole. In FIG. 4, the conductor 11 is not shown.

Part of the first and second semiconductor regions FD1, FD2 is in contact with a region immediately below the gate electrodes TX1, TX2 in the semiconductor substrate 1A. An antireflection film 1D is provided on the light incident surface 1BK side of the semiconductor substrate 1A. The material of the antireflection film 1D is SiO ₂ or SiN.

  The wiring substrate 10 is electrically connected to the first and second semiconductor regions FD1 and FD2, the first and second gate electrodes TX1 and TX2, the photogate electrode PG, and the like through bump electrodes in the adhesion region AD. A through electrode (not shown) is provided. The through electrode of the wiring board 10 is exposed on the back surface of the wiring board 10. A light-shielding layer (not shown) is formed on the surface of the insulating substrate constituting the wiring substrate 10 on the interface side with the adhesion region AD, so that the light transmitted through the distance image sensor 1 is prevented from entering the wiring substrate 10. is doing. In this distance measuring device, when the distance image sensor 1 is mounted on the wiring board 10, the signal can be given to each electrode through each wiring, and the device is miniaturized.

  When a high level signal (positive potential) is applied to the first and second gate electrodes TX1, TX2, the potential below the first and second gate electrodes TX1, TX2 becomes higher than the potential below the photogate electrode PG. . As a result, negative charges (electrons) are drawn in the direction of the first and second gate electrodes TX1, TX2, and accumulated in the potential well formed by the first and second semiconductor regions FD1, FD2. An n-type semiconductor includes a positively ionized donor, has a positive potential, and attracts electrons. When a low level signal (ground potential) is applied to the first and second gate electrodes TX1 and TX2, the potential below the first and second gate electrodes TX1 and TX2 becomes lower than the potential below the photogate electrode PG. , A barrier is formed. Therefore, the charge generated in the semiconductor substrate 1A is not drawn into the first and second semiconductor regions FD1, FD2.

  In the distance image sensor 1, charges generated in the deep part of the semiconductor in response to the incidence of light for projection are drawn into a potential well provided in the vicinity of the charge generation position on the opposite side to the light incident surface 1BK, so that it is accurate at high speed. Ranging is possible.

The pulsed light LD from the object incident from the light incident surface (back surface) 1BK of the semiconductor substrate 1A reaches a region immediately below the photogate electrode PG provided on the front surface side of the semiconductor substrate 1A. The charges generated in the semiconductor substrate 1A with the incidence of the pulsed light are distributed from the region immediately below the photogate electrode PG to the region immediately below the first and second gate electrodes TX1 and TX2 adjacent thereto. That is, when the detection gate signals S ₁ and S ₂ synchronized with the drive signal SP of the light source are alternately applied to the first and second gate electrodes TX1 and TX2 via the wiring substrate 10, the region immediately below the photogate electrode PG. The charges generated in the first region flow into regions immediately below the first and second gate electrodes TX1 and TX2, respectively, and then flow into the first and second semiconductor regions FD1 and FD2.

  The ratio of the charge amounts Q1 and Q2 accumulated in the first semiconductor region FD1 or the second semiconductor region FD2 to the total charge amount (Q1 + Q2) is the same as the emission pulse light emitted by applying the drive signal SP to the light source and the target This corresponds to the phase difference of the detection pulse light returned by reflecting the outgoing pulse light by the object H.

Increasing the frequency of the drive signals (detection gate signals S ₁ and S ₂ ) to the first and second gate electrodes TX1 and TX2 makes it possible to receive near infrared light even if the charge distribution speed is increased. The generation area of the charges generated according to the above is closer to the surface 1FT on the opposite side than the light incident surface 1BK of the semiconductor substrate 1A, so that a large amount of charges from the area immediately below the photogate electrode PG from the first and second semiconductors. The stored charges Q1 and Q2 can be read out from the regions FD1 and FD2 through the wiring (not shown) of the wiring board 10 from these regions.

  Although not shown, the distance image sensor 1 includes a back gate semiconductor region for fixing the potential of the semiconductor substrate 1A to a reference potential. The back gate semiconductor region is a p-type semiconductor region containing a high concentration impurity. Instead of the back gate semiconductor region, a through electrode that has a p-type semiconductor layer such as a p-type diffusion region and is electrically connected may be provided.

  7 and 8 are diagrams showing a potential distribution in the vicinity of the surface 1FT of the semiconductor substrate 1A for explaining the signal charge accumulation operation. 7 and 8, the downward direction is the positive direction of the potential. 7 and 8, (a) shows the potential distribution along the transverse direction of the transverse section of FIG. 5, and (b) shows the potential distribution along the transverse direction of the transverse section of FIG. Indicates.

At the time of light incidence, the potential φPG in the region immediately below the photogate electrode _PG is set slightly higher than the substrate potential. Each figure shows a potential φ _{TX1 in} a region immediately below the first gate electrode TX1, a potential φ _{TX2 in} a region immediately below the second gate electrode TX2, a potential φ _FD1 in the first semiconductor region _FD1 , and a second semiconductor region FD2. The potential φ _FD2 is shown.

High potential of the detection gate signals S ₁ is inputted to the first gate electrode TX1, as shown in FIG. 7, the charges generated immediately below the photogate electrode PG, according to the potential gradient, the first gate Accumulation is performed in the potential well of the first semiconductor region FD1 via the region immediately below the electrode TX1. The charge amount Q1 is accumulated in the potential well of the first semiconductor region FD1.

Following the detection gate signal S _1, the high potential of the detection gate signal S ₂ is inputted to the second gate electrode TX2, as shown in FIG. 8, was generated immediately under the photo gate electrode PG charge Are accumulated in the potential well of the second semiconductor region FD2 via the region immediately below the second gate electrode TX2 in accordance with the potential gradient. The charge amount Q2 is accumulated in the potential well of the second semiconductor region FD2.

  FIG. 9 is a schematic diagram for explaining a configuration of a pixel.

The first gate electrode TX1, the detection gate signals _{S 1} supplied. The second gate electrode TX2, the detection gate signal _{S 2} is applied. That is, charge transfer signals having different phases are applied to the first gate electrode TX1 and the second gate electrode TX2.

Charge generated in the photosensitive region immediately below the photogate electrode PG, when the detection gate signals S ₁ at a high level to the first gate electrode TX1 is given, the potential formed by a first semiconductor region FD1 It flows into the well as signal charge. The signal charges accumulated in the first semiconductor region FD1 is read from the first semiconductor region FD1 as an output corresponding to the accumulated charge amount _{Q 1 (V out1).} Charge generated in the photosensitive region immediately below the photogate electrode PG, when the second gate electrode TX2 detection gate signal S ₂ of the high level is given, the potential formed by the second semiconductor region FD2 It flows into the well as signal charge. The signal charges accumulated in the second semiconductor region FD2 is read from the second semiconductor region FD2 as an output corresponding to the accumulated charge amount _{Q 2 (V out2).} These outputs (V _out1 , V _out2 ) correspond to the signal d ′ (m, n) described above.

  As described above, in the present embodiment, the first and second gate electrodes TX1 and TX2 are disposed so as to enter the first region R1 in which the photogate electrode PG is disposed. The first and second gate electrodes TX1 and TX2 have portions TX1a to TX1c and TX2a to TX2c extending along the edge of the second region R2 (edge facing the photogate electrode PG).

  Therefore, the distance image sensor including the pixel configuration shown in FIG. 10 in which the first and second gate electrodes 101 and 102 are disposed outside the first region R1 so as to extend along the first direction D1. As compared with the above, the light use efficiency per unit length in the first direction D1 is increased. That is, when the area of the photogate electrode PG is the same, the distance image sensor 1 has a higher aperture ratio than the distance image sensor shown in FIG. Therefore, in the distance image sensor 1, it is possible to increase the area of the region (charge generation region) immediately below the photogate electrode PG and achieve high sensitivity. In the distance image sensor shown in FIG. 10, the photogate electrode 100 has a rectangular shape with the first direction D1 as the long side direction.

  Since each of the first and second gate electrodes TX1 and TX2 includes the above-described portions TX1a to TX1c and TX2a to TX2c, the electrode length is longer than that of the distance image sensor shown in FIG. The electrode area increases. For this reason, the charge generated in the region immediately below the photogate electrode PG is easily moved, and the charge transfer efficiency is improved. Also from this, the sensitivity of the distance image sensor 1 can be increased. When the lengths of the gate electrodes 101 and 102 in the distance image sensor shown in FIG. 10 are set to be the same as the gate electrodes TX1 and TX2 in the distance image sensor 1, the lengths of the gate electrodes 101 and 102 are Since the length becomes longer in the first direction D1, the dead space DS increases as shown in FIG.

The charges (charge amounts Q1, Q2) transferred to and accumulated in the first and second semiconductor regions FD1, FD2 are expressed by the following relational expression according to the capacitances (Cfd) of the first and second semiconductor regions FD1, FD2. A voltage change (ΔV) indicated by
ΔV = Q1 / Cfd
ΔV = Q2 / Cfd
Since the first and second semiconductor regions FD1 and FD2 are arranged so as to be included in the second region R2 that overlaps the first region R1, the first and second semiconductor regions FD1 and FD2 are seen in a plan view. Thus, the edges (sides FD1a to FD1c, FD2a to FD2c) are arranged so as to be surrounded by the photogate electrode PG. For this reason, the area of the first and second semiconductor regions FD1, FD2 is smaller than the area of the region where charges can be transferred to the first and second semiconductor regions FD1, FD2 in the region (charge generation region) immediately below the photogate electrode PG. The area is relatively reduced. When the areas of the first and second semiconductor regions FD1 and FD2 are reduced, the capacitance (Cfd) of the first and second semiconductor regions FD1 and FD2 is also reduced, and the generated voltage change (ΔV) is increased. That is, the charge voltage conversion gain is increased. Also from this, the sensitivity of the distance image sensor 1 can be increased.

  Next, a first modification example regarding the configuration of the pixel P (m, n) of the distance image sensor 1 will be described with reference to FIGS. 12 and 13. FIG. 12 is a schematic diagram for explaining the configuration of the pixels of the distance image sensor according to the first modification. FIG. 13 is a diagram showing a cross-sectional configuration along the line XIII-XIII in FIG.

  The pixel P (m, n) of the distance image sensor 1 according to the first modification is different from the pixel P (m, n) shown in FIGS. 4 to 6 in the second region R2, the first and The second semiconductor regions FD1 and FD2 and the shapes of the first and second gate electrodes TX1 and TX2 are different. The distance image sensor 1 according to the first modification also includes a photogate electrode PG and a plurality of first and second gate electrodes TX1 and TX2 provided on the semiconductor substrate 1A in each pixel P (m, n). And a plurality of first and second semiconductor regions FD1 and FD2, respectively.

  The second region R2 has a triangular shape. The second region R2 is surrounded by the photogate electrode PG over two sides included in the edge of the second region R2. Two sides included in the edge of the second region R2 extend in a direction intersecting the first direction D1.

  The first and second semiconductor regions FD1 and FD2 are spatially separated and alternately arranged along the first direction D1. The first and second semiconductor regions FD1, FD2 are also arranged so as to face each other in a direction orthogonal to the first direction D1. That is, the first semiconductor region FD1 and the second semiconductor region FD2 are arranged so as to sandwich the photogate electrode PG in a direction parallel to and perpendicular to the first direction D1. The first and second semiconductor regions FD1, FD2 are arranged so that a part thereof is included in the corresponding second region R2.

  The first semiconductor region FD1 is disposed in a second region R2 provided on the side R1a side of the first region R1. The second semiconductor region FD2 is disposed in the second region R2 provided on the side R1b side of the first region R1. The first semiconductor region FD1 and the second semiconductor region FD2 face each other so as to sandwich the photogate electrode PG in the facing direction of the two sides R1a and R1b of the first region R1 (direction perpendicular to the first direction D1). Are arranged.

  The first semiconductor region FD1 includes sides FD1a and FD1b each having an edge extending along the edge of the second region R2 (the two sides included in the edge). Two sides FD1a and FD1b at the edge of the first semiconductor region FD1 extend in a direction intersecting the first direction D1. In the present embodiment, the first semiconductor region FD1 has a rectangular shape.

  The second semiconductor region FD2 includes sides FD2a and FD2b whose edges extend along the edge of the second region R2 (the two sides included in the edge). Two sides FD2a and FD2b at the edge of the second semiconductor region FD2 extend in a direction intersecting the first direction D1. In the present embodiment, the second semiconductor region FD2 has a rectangular shape.

  The first gate electrode TX1 has a portion TX1a extending along the side FD1a of the first semiconductor region FD1 and a portion TX1b extending along the side FD1b of the first semiconductor region FD1. That is, the first gate electrode TX1 has portions TX1a and TX1b extending along the two sides included in the edge of the second region R2. The first gate electrode TX1 has a substantially V shape in plan view.

  The second gate electrode TX2 has a portion TX2a extending along the side FD2a of the second semiconductor region FD2, and a portion TX2b extending along the side FD2b of the second semiconductor region FD2. That is, the second gate electrode TX2 has portions TX2a and TX2b extending along the two sides included in the edge of the second region R2. Similarly to the first gate electrode TX1, the second gate electrode TX2 has a V shape in plan view.

  Also in the first modified example, as described above, the sensitivity of the distance image sensor 1 can be increased.

  Next, a second modification example regarding the configuration of the pixel P (m, n) of the distance image sensor 1 will be described with reference to FIG. FIG. 14 is a schematic diagram for explaining a configuration of pixels of a distance image sensor according to a second modification.

  The pixel P (m, n) of the distance image sensor 1 according to the second modification example is different from the first modification example in the second region R2, the first and second semiconductor regions FD1, FD2, and the first region. The second gate electrodes TX1 and TX2 are different in shape. Similarly to the first modification, the distance image sensor 1 according to the second modification also includes a plurality of first photogate electrodes PG provided on the semiconductor substrate 1A in each pixel P (m, n). 1 and second gate electrodes TX1 and TX2, and a plurality of first and second semiconductor regions FD1 and FD2, respectively.

  The second region R2 has a trapezoidal shape. The first semiconductor region FD1 has a trapezoidal shape with the two sides FD1a and FD1b as oblique sides. Two sides FD1a and FD1b at the edge of the first semiconductor region FD1 extend in a direction intersecting the first direction D1. The second semiconductor region FD2 also has a trapezoidal shape with the two sides FD2a and FD2b as oblique sides. Two sides FD2a and FD2b at the edge of the second semiconductor region FD2 extend in a direction intersecting the first direction D1.

  The first gate electrode TX1 has two portions TX1a and TX1b and a portion TX1c connecting the two portions TX1a and TX1b. The second gate electrode TX2 also includes two portions TX2a and TX2b and a portion TX2c that connects the two portions TX2a and TX2b.

  Also in the second modified example, as described above, the sensitivity of the distance image sensor 1 can be increased.

  Subsequently, a third modification example regarding the configuration of the pixel P (m, n) of the distance image sensor 1 will be described with reference to FIGS. 15 and 16. FIG. 15 is a schematic diagram for explaining a configuration of pixels of a distance image sensor according to a third modification. FIG. 16 is a diagram showing a cross-sectional configuration along the line XVI-XVI in FIG.

  The pixel P (m, n) of the distance image sensor 1 according to the third modification example has a second region R2, a first semiconductor region FD1, a second semiconductor region FD2, and a second semiconductor region, compared to the first and second modification examples. In addition, the first and second gate electrodes TX1 and TX2 are different in shape. Similarly to the first and second modifications, the distance image sensor 1 according to the third modification also includes a photogate electrode PG provided on the semiconductor substrate 1A in each pixel P (m, n), respectively. A plurality of first and second gate electrodes TX1 and TX2, and a plurality of first and second semiconductor regions FD1 and FD2, respectively.

  The second region R2 has a fan shape. Therefore, 2nd area | region R2 contains the circular arc in the edge. Specifically, the second region R2 located at both ends in the first direction D1 includes a substantially ¼ arc at the edge, and the other second region R2 is approximately ½ at the edge. Contains an arc. The second region R2 is arranged so that the arc included in the edge faces the photogate electrode PG (charge generation region). The photogate electrode PG includes an arc PGb whose edge extends along the arc of the second region R2.

  The first semiconductor region FD1 includes an arc FD1d whose edge extends along the arc of the second region R2. Similarly to the first semiconductor region FD1, the second semiconductor region FD2 includes an arc FD2d whose edge extends along the arc of the second region R2. In the present embodiment, the first and second semiconductor regions FD1, FD2 have a circular shape.

  The first gate electrode TX1 has a portion TX1d extending along the arc FD1d of the first semiconductor region FD1, that is, the arc of the second region R2 (the arc PGb of the photogate electrode PG). The second gate electrode TX2 has a portion TX2d extending along the arc FD2d of the second semiconductor region FD2, that is, the arc of the second region R2 (the arc PGb of the photogate electrode PG). The first and second gate electrodes TX1, TX2 are substantially C-shaped in plan view.

  Also in the third modified example, as described above, the sensitivity of the distance image sensor 1 can be increased.

  Next, with reference to FIG. 17, a fourth modification example regarding the configuration of the pixel P (m, n) of the distance image sensor 1 will be described. FIG. 17 is a schematic diagram for explaining a configuration of a pixel of a distance image sensor according to a fourth modification.

  The pixel P (m, n) of the distance image sensor 1 according to the fourth modification example has a second region R2, first and second semiconductors with respect to the pixel P (m, n) shown in FIG. The regions FD1 and FD2 and the shapes of the first and second gate electrodes TX1 and TX2 are different. Similarly to the first and second modifications, the distance image sensor 1 according to the fourth modification also includes a photogate electrode PG provided on the semiconductor substrate 1A in each pixel P (m, n), respectively. A plurality of first and second gate electrodes TX1 and TX2, and a plurality of first and second semiconductor regions FD1 and FD2, respectively.

  The second region R2 has a fan shape. The first and second semiconductor regions FD1, FD2 include arcs FD1d, FD2d whose edges extend along the arc of the second region R2, respectively. The first and second gate electrodes TX1 and TX2 respectively have portions TX1d and TX2d extending along the arc of the second region R2 (the arc PGb of the photogate electrode PG).

  Also in the fourth modified example, as described above, the sensitivity of the distance image sensor 1 can be increased.

  Next, a fifth modification example regarding the configuration of the pixel P (m, n) of the distance image sensor 1 will be described with reference to FIGS. FIG. 18 is a schematic diagram for explaining a configuration of pixels of a distance image sensor according to a fifth modification. FIG. 19 is a view showing a cross-sectional configuration along the line XIX-XIX in FIG. 20 is a diagram showing a cross-sectional configuration along the line XX-XX in FIG.

  The pixel P (m, n) of the distance image sensor 1 according to the fifth modification is different from the first modification in that it includes an unnecessary charge collection region and an unnecessary charge collection gate electrode. To do. The distance image sensor 1 according to the fifth modification includes a photogate electrode PG and a plurality of first and second gate electrodes TX1 and TX2 provided on the semiconductor substrate 1A in each pixel P (m, n). A plurality of first and second semiconductor regions FD1 and FD2, a plurality of third semiconductor regions FD3 (unnecessary charge collection regions), and a plurality of third gate electrodes TX3 (unnecessary charge collection gate electrodes). ing.

  The third semiconductor region FD3 is disposed in a second region R2 different from the second region R2 in which the first and second semiconductor regions FD1, FD2 are disposed. The third semiconductor region FD3 is disposed spatially separated from the first and second semiconductor regions FD1, FD2. The third semiconductor region FD3 is arranged so that a part thereof is included in the corresponding second region R2.

The third semiconductor region FD3 includes sides FD3a and FD3b whose edges extend along the edges of the second region R2 (the two sides included in the edges). Two sides FD3a and FD3b at the edge of the third semiconductor region FD3 extend in a direction intersecting the first direction D1. In the present embodiment, the third semiconductor region FD3 has a rectangular shape. The third semiconductor region FD3 is a floating diffusion region made of an n-type semiconductor having a high impurity concentration, like the first and second semiconductor regions FD1 and FD2. The thickness / impurity concentration of the third semiconductor region FD3 is as follows.
Semiconductor region FD3: thickness 0.1 to 1 μm / impurity concentration 1 × 10 ¹⁸ to 10 ²⁰ cm ⁻³

The third gate electrode TX3 is located between the photogate electrode PG and the third semiconductor region FD3 in the second region R2. For this reason, the third gate electrode TX3 is arranged so that the entirety thereof enters the first region R1. The third gate electrode TX3 is
A portion TX3a extending along the side FD3a of the third semiconductor region FD3 and a portion TX3b extending along the side FD3b of the third semiconductor region FD3 are included. That is, the third gate electrode TX3 has portions TX3a and TX3b extending along the two sides included in the edge of the second region R2. The third gate electrode TX3 has a substantially V shape in plan view.

  The electrode lengths and electrode areas of the first to third gate electrodes TX1, TX2, TX3 are set to be the same. The third gate electrode TX3 is made of polysilicon like the first and second gate electrodes TX1 and TX2, but other materials may be used.

  In the second region R2 located at both ends in the first direction D1, only one side of the edge faces the side PGa of the photogate electrode PG. The area of the second region R2 located at both ends in the first direction D1 is substantially half of the area of the other second region R2. The first gate electrodes TX1 positioned at both ends in the first direction D1 have only one of the part TX1a and the part TX1a. The second gate electrodes TX2 located at both ends in the first direction D1 have only one of the part TX2a and the part TX2a.

  The insulating layer 1E is provided with a contact hole for exposing the surface of the third semiconductor region FD3. A conductor 11 for connecting the third semiconductor region FD3 to the outside is disposed in the contact hole. In FIG. 18, the conductor 11 is not shown.

  The third semiconductor region FD3 collects unnecessary charges generated in the region immediately below the photogate electrode PG in the semiconductor substrate 1A. A part of the charges generated in the region immediately below the photogate electrode PG is converted into unnecessary charges according to a potential gradient formed by a voltage applied to the photogate electrode PG and the third gate electrode TX3. It runs in the direction of the gate electrode TX3.

  When a high level signal (positive potential) is applied to the third gate electrode TX3, the potential under the gate of the third gate electrode TX3 becomes higher than the potential under the photogate electrode PG in the semiconductor substrate 1A. Thereby, negative charges (electrons) are drawn in the direction of the third gate electrode TX3 and accumulated in the potential well formed by the third semiconductor region FD3. When a low level signal (potential lower than the positive potential, eg, ground potential) is applied to the third gate electrode TX3, the potential under the gate of the third gate electrode TX3 is below the photogate electrode PG in the semiconductor substrate 1A. It becomes higher than the potential of this part, and a barrier is formed. Therefore, the charge generated in the semiconductor substrate 1A is not drawn into the third semiconductor region FD3.

  FIG. 21 is a diagram showing a potential distribution in the vicinity of the surface 1FT of the semiconductor substrate 1A for explaining the signal charge accumulation operation. FIG. 22 is a diagram showing a potential distribution in the vicinity of the surface 1FT of the semiconductor substrate 1A for explaining an unnecessary charge discharging operation. 21 and 22, the downward direction is the positive direction of the potential. 21, (a) and (b) show the potential distribution along the lateral direction of the lateral section of FIG. 19, and (c) shows the potential along the lateral direction of the lateral section of FIG. Show the distribution. 22A shows the potential distribution along the horizontal direction of the horizontal cross section of FIG. 19, and FIG. 22B shows the potential distribution along the horizontal direction of the horizontal cross section of FIG.

21 and FIG. 22, the potential φ _TX1 in the region immediately below the first gate electrode TX1, the potential φ _TX2 in the region immediately below the second gate electrode TX2, the potential φ _{TX3 in} the region immediately below the third gate electrode _TX3 , potential phi _PG in the region immediately below the photogate electrode PG, the first semiconductor region FD1 of the potential phi _FD1, potential phi _FD2 of the second semiconductor region FD2, potential phi _OFD of the third semiconductor region FD3 is shown.

The potential φ _PG in the region immediately below the photogate electrode _PG is obtained by using the potential (φ _TX1 , φ _TX2 , φ _TX3 ) in the region immediately below the adjacent first to third gate electrodes _{TX1 to TX3} at the time of no bias as a reference potential. Then, it is set higher than this reference potential. The potential φ _{PG in} the region immediately below the photogate electrode PG is higher than the potentials φ _TX1 , φ _TX2 , φ _TX3 , and the potential distribution in this region has a shape recessed downward in the drawing.

  The signal charge accumulation operation will be described with reference to FIG.

When the phase of the charge transfer signal applied to the first gate electrode TX1 is 0 degree, a positive potential is applied to the first gate electrode TX1, and an opposite phase potential, that is, the phase is applied to the second gate electrode TX2. A potential of 180 degrees (ground potential) is applied. In this case, as shown in FIG. 21 (a), the charges generated immediately below the photogate electrode PG, by the semiconductor potential phi _TX1 immediately below the first gate electrode TX1 is lowered, the first semiconductor region FD1 It flows into the potential well.

On the other hand, the semiconductor potential phi _TX2 immediately below the second gate electrode TX2 is not lowered, within the potential well of the second semiconductor region FD2, the charge does not flow into. As a result, signal charges are collected and accumulated in the potential well of the first semiconductor region FD1. In the first and second semiconductor regions FD1 and FD2, since the n-type impurity is added, the potential is recessed in the positive direction.

When the phase of the charge transfer signal applied to the second gate electrode TX2 is 0 degree, a positive potential is applied to the second gate electrode TX2, and a reverse phase potential, that is, the phase is applied to the first gate electrode TX1. A potential of 180 degrees (ground potential) is applied. In this case, as shown in FIG. 21 (b), the charges generated immediately below the photogate electrode PG, by the semiconductor potential phi _TX2 immediately below the second gate electrode TX2 is lowered, the second semiconductor region FD2 It flows into the potential well. On the other hand, the potential φ _{TX1 in} the region immediately below the first gate electrode TX1 does not drop, and no charge flows into the potential well of the first semiconductor region FD1. As a result, signal charges are collected and accumulated in the potential well of the second semiconductor region FD2.

While a charge transfer signal whose phase is shifted by 180 degrees is applied to the first and second gate electrodes TX1, TX2, a ground potential is applied to the third gate electrode TX3. Therefore, as shown in FIG. 21 (c), the semiconductor potential phi _TX3 immediately below the third gate electrode TX3 is not lowered, the third the potential well semiconductor region FD3, charge does not flow into.

  As described above, signal charges are collected and accumulated in the potential wells of the first and second semiconductor regions FD1, FD2. The signal charges accumulated in the potential wells of the first and second semiconductor regions FD1, FD2 are read out to the outside.

  With reference to FIG. 22, the discharge operation of unnecessary charges will be described.

A ground potential is applied to the first and second gate electrodes TX1, TX2. Therefore, as shown in FIG. 22A, the potentials φ _TX1 and φ _{TX2 in} the regions immediately below the first and second gate electrodes TX1 and _TX2 are not lowered, and the potentials of the first and second semiconductor regions FD1 and FD2 are not lowered. No charge flows into the well. On the other hand, a positive potential is applied to the third gate electrode TX3. In this case, as shown in FIG. 22 (b), the charges generated immediately below the photogate electrode PG, by the semiconductor potential phi _TX3 immediately below the third gate electrode TX3 is lowered, the third semiconductor region FD3 It flows into the potential well. Thus, unnecessary charges are collected in the potential well of the third semiconductor region FD3. Unnecessary charges collected in the potential well of the third semiconductor region FD3 are also discharged to the outside.

  FIG. 23 is a timing chart of actual various signals.

The one-frame period _TF includes a signal charge accumulation period (accumulation period) T _acc and a signal charge read period (readout period) _Tro . Focusing on one pixel, the accumulation period T _acc, the driving signal synchronized with the pulse drive signal S _P multiple pulses are applied to the light source, in synchronization with this, the detection gate signal S _1, S ₂ are opposite to each other The phase is applied to the first and second gate electrodes TX1, TX2. Prior to the distance measurement, the reset signal reset is applied to the first and second semiconductor regions FD1 and FD2, and the charges accumulated inside are discharged to the outside. In this example, after the reset signal reset is turned on for a moment and then turned off, a plurality of drive vibration pulses are sequentially applied, and further, charge transfer is sequentially performed in synchronization with the first and second semiconductors. Signal charges are accumulated and accumulated in the regions FD1 and FD2.

Then, in the readout period _{T ro,} the signal charge accumulated in the first and second semiconductor regions FD1, the FD2 is read. At this time, the charge transfer signal S ₃ applied to the third gate electrode TX3 is turned ON, a positive potential is applied to the third gate electrode TX3, unnecessary charges are collected in the potential well of the third semiconductor region FD3 .

  FIG. 24 is a timing chart showing modifications of various signals.

In the modification shown in FIG. 24, the duty ratio (ON ratio with respect to the unit period) is set to be smaller with respect to the drive signal _SD than in the above-described embodiment. As a result, the driving power when the light source is ON increases, and the S / N ratio is further improved. In this modification, each one pulse of the drive signal S _D, respectively to generate one pulse of the first to third gate electrodes TX1 to TX3. Thereby, even when the driving power of the light source is increased, unnecessary charges can be discharged and the distance detection accuracy can be improved.

  In the fifth modified example, unnecessary charges are prevented from being accumulated in the first and second semiconductor regions FD1, FD2. For this reason, the distance detection accuracy in the distance image sensor 1 can be improved. Of course, also in the fifth modification, as described above, the sensitivity of the distance image sensor 1 can be increased.

  In the fifth modification, the third semiconductor region FD3 includes two sides FD3a and FD3b each extending along the two sides included in the edge of the second region R2. The third gate electrode TX3 is located between the photogate electrode PG and the third semiconductor region FD3 in the second region R2, and has portions TX3a and TX3b extending along the two sides of the second region R2. is doing. Thereby, unnecessary charges can be discharged efficiently.

  Next, with reference to FIGS. 25 to 27, sixth to eighth modifications regarding the configuration of the pixel P (m, n) of the distance image sensor 1 will be described. FIG. 25 is a schematic diagram for explaining a configuration of pixels of a distance image sensor according to a sixth modification. FIG. 26 is a schematic diagram for explaining a configuration of pixels of a distance image sensor according to a seventh modification. FIG. 27 is a schematic diagram for explaining a configuration of pixels of a distance image sensor according to an eighth modification.

  The pixel P (m, n) of the distance image sensor 1 according to the sixth to eighth modifications is also provided with an unnecessary charge collection region and an unnecessary charge collection gate electrode, as compared with the first modification. It is different in point. The distance image sensor 1 according to the sixth to eighth modifications includes a photogate electrode PG and a plurality of first and second gate electrodes provided on the semiconductor substrate 1A in each pixel P (m, n). TX1, TX2, a plurality of first and second semiconductor regions FD1, FD2, a plurality of third semiconductor regions FD3 (unnecessary charge collection regions), and a plurality of third gate electrodes TX3 (unnecessary charge collection gate electrodes), It is equipped with.

  The third gate electrode TX3 located at the end in the first direction D1 has only one of the part TX3a and the part TX3a.

  Also in the sixth to eighth modifications, as described above, it is possible to increase the sensitivity of the distance image sensor 1 and improve the distance detection accuracy in the distance image sensor 1.

  Subsequently, a ninth modification example regarding the configuration of the pixel P (m, n) of the distance image sensor 1 will be described with reference to FIGS. 28 to 30. FIG. 28 is a schematic diagram for explaining a configuration of pixels of a distance image sensor according to a ninth modification. FIG. 29 is a diagram showing a cross-sectional configuration along the line XXIX-XXIX in FIG. FIG. 30 is a diagram showing a cross-sectional configuration along the line XXX-XXX in FIG.

  The pixel P (m, n) of the distance image sensor 1 according to the ninth modification includes the first to third semiconductor regions FD1, FD2, FD3 and the first to third gate electrodes compared to the fifth modification. The difference is in the positions of TX1, TX2, and TX3. The distance image sensor 1 according to the ninth modification also includes a photogate electrode PG and a plurality of first and second gate electrodes TX1 and TX2 provided on the semiconductor substrate 1A in each pixel P (m, n). And a plurality of first and second semiconductor regions FD1, FD2, a plurality of third semiconductor regions FD3, and a plurality of third gate electrodes TX3.

  The first to third semiconductor regions FD1, FD2, and FD3 are formed so as to overlap the p-type well region W and to be surrounded by the well region W on the side opposite to the first region R1 side. . The periphery of the first to third semiconductor regions FD1, FD2, and FD3 is surrounded by a well region W having a higher concentration than the impurity concentration immediately below the substrate 1A and the first and second gate electrodes TX1 and TX2. As a result, the spread of the depletion layer from each of the semiconductor regions FD1, FD2, and FD3 can be suppressed, the leakage current can be reduced, and trapping of unnecessary charges due to crosstalk and stray light can be reduced. The well region W suppresses the coupling between the depletion layer expanded by applying a voltage to the photogate electrode PG and the depletion layer extending from the first to third semiconductor regions FD1, FD2, and FD3.

The thickness / impurity concentration of the well region is as follows.
Well region W: thickness 0.5 to 5 μm / impurity concentration 1 × 10 ¹⁶ to 10 ¹⁸ cm ⁻³

  The first and second semiconductor regions FD1, FD2 are arranged in a second region R2 provided on the side R1b side of the first region R1. The first and second semiconductor regions FD1 and FD2 are spatially separated and alternately arranged along the first direction D1. The third semiconductor region FD3 is disposed in the second region R2 provided on the side R1a side of the first region R1.

  Also in the ninth modification, as described above, it is possible to increase the sensitivity of the distance image sensor 1 and improve the distance detection accuracy in the distance image sensor 1.

  When the first to third semiconductor regions FD1, FD2, FD3 and the well region W are formed, a mask for forming each region is a facing direction of the two sides R1a, R1b of the first region R1 (first When the position is shifted in a direction perpendicular to the direction D1, the width of the overlapping region of the first and second semiconductor regions FD1, FD2 and the well region W in the facing direction varies. For example, if the width of the region in which the first and second semiconductor regions FD1, FD2 and the well region W overlap in the above-described opposing direction is widened, a potential barrier is formed, which hinders the flow of charges. Arise.

  Since the first and second semiconductor regions FD1, FD2 are respectively disposed in the second region R2 provided on the side R1b side of the first region R1, the first semiconductor region FD1 and the well region W overlap. When the width of the region in the facing direction is narrowed, the width of the overlapping region of the second semiconductor region FD2 and the well region W in the facing direction is also narrowed. Conversely, when the width of the overlapping region between the first semiconductor region FD1 and the well region W in the facing direction is increased, the width in the facing direction of the overlapping region between the second semiconductor region FD2 and the well region W is also increased. Therefore, the potential gradient toward the first semiconductor region FD1 and the potential gradient toward the second semiconductor region FD2 are the same, and there is no problem in transferring charges to the first and second semiconductor regions FD1, FD2. . That is, even when a mask misalignment occurs when forming the first and second semiconductor regions FD1, FD2 and the well region W, the charge generated in the region immediately below the photogate electrode PG is transferred to the first semiconductor region. It is possible to appropriately distribute between the FD1 and the second semiconductor region FD2. As a result, it is possible to suppress an imbalance between the charge amount Q1 accumulated in the first semiconductor region FD1 and the charge amount Q2 accumulated in the second semiconductor region FD2 due to the displacement of the mask. it can. Therefore, according to the distance image sensor 1 which concerns on a 9th modification, it can suppress that the detection accuracy of distance falls.

  Subsequently, with reference to FIG. 31, a tenth modification example regarding the configuration of the pixel P (m, n) of the distance image sensor 1 will be described. FIG. 31 is a schematic diagram for explaining the configuration of the pixels of the distance image sensor according to the tenth modification. The pixel P (m, n) of the distance image sensor 1 according to the tenth modification is different from the first modification in the shape of the photogate electrode PG (charge generation region).

  The photogate electrode PG includes a side PGc extending in the first direction D1 between the second regions R2 whose edges are adjacent to each other in the first direction D1. Thereby, in the tenth modification, the distance between the first semiconductor regions FD1 and the distance between the second semiconductor regions FD2 in the first direction D1 are wider than in the first modification. Therefore, a region (hereinafter referred to as “transferable region”) in which charges can be transferred to the first and second semiconductor regions FD1 and FD2 in a region (charge generation region) immediately below the photogate electrode PG is enlarged. Become.

  By expanding the transferable region, the areas of the first and second semiconductor regions FD1, FD2 are further reduced relative to the area of the transferable region. Therefore, the capacitance (Cfd) of the first and second semiconductor regions FD1, FD2 is reduced, and the generated voltage change (ΔV) is further increased. As a result, the sensitivity of the distance image sensor 1 can be further increased.

  Next, with reference to FIG. 32, an eleventh modification regarding the configuration of the pixel P (m, n) of the distance image sensor 1 will be described. FIG. 32 is a schematic diagram for explaining a pixel configuration of a distance image sensor according to an eleventh modification. The pixel P (m, n) of the distance image sensor 1 according to the eleventh modification is different from the sixth modification in the shape of the photogate electrode PG (charge generation region).

  Similar to the tenth modification, the photogate electrode PG includes a side PGc whose edge extends in the first direction D1 between the second regions R2 adjacent in the first direction D1. As a result, the transferable region in the region (charge generation region) immediately below the photogate electrode PG is expanded, and the areas of the first and second semiconductor regions FD1, FD2 are further reduced relative to the area of the transferable region. To do. Therefore, as described above, the sensitivity of the distance image sensor 1 can be further increased.

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

  A charge generation region in which charge is generated in response to incident light may be configured by a photodiode (for example, an embedded photodiode). The number of the second regions R2 in the first direction D1 is not limited to the number shown in the above-described embodiment and each modification. The distance image sensor 1 may be a surface irradiation type distance image sensor.

  INDUSTRIAL APPLICABILITY The present invention can be used for a distance sensor and a distance image sensor mounted on a product monitor or a vehicle in a factory production line.

  DESCRIPTION OF SYMBOLS 1 ... Distance image sensor, 1A ... Semiconductor substrate, D1 ... 1st direction, FD1 ... 1st semiconductor region, FD1a, FD1b, FD1c ... Side, FD1d ... Arc, FD2 ... 2nd semiconductor region, FD2a, FD2b, FD2c ... Side, FD2d ... arc, FD3 ... third semiconductor region, FD3a, FD3b ... side, PG ... photogate electrode, PGa ... side, PGb ... arc, PGc ... side, R1 ... first region, R1a, R1b ... side, R2 ... second region, TX1 ... first gate electrode, TX1a, TX1b, TX1c, TX1d ... part, TX2 ... second gate electrode, TX2a, TX2b, TX2c, TX2d ... part, TX3 ... third gate electrode, TX3a, TX3b ... part.

Claims (10)

A charge generation region in which charge is generated in response to incident light;
A plurality of signal charge collection regions that are spaced apart from each other and collect signal charges from the charge generation region;
A transfer electrode provided in each of the signal charge collection regions, to which a charge transfer signal having a different phase is applied, and
The charge generation region is disposed in a first region having a rectangular shape and extending in a first direction,
The signal charge collection region is provided on each of two sides extending in the first direction of the first region so as to face each other in a direction orthogonal to the first direction, and overlaps the first region Arranged so as to be at least partially included in the plurality of second regions,
The transfer electrode is located between the charge generation region and the signal charge collection region in the second region, and has a portion extending along an edge of the second region,
The distance sensor, wherein an edge of the charge generation region extends along an edge of the second region. The second region includes two sides whose edges extend in a direction intersecting the first direction, or an arc.
The signal charge collection region has two edges extending along the two sides included in the edge of the second region or the arc included in the edge of the second region. Including arcs,
The transfer electrode has a portion extending along the two sides or the arc included in the edge of the second region,
The charge generation region has two edges extending along the two sides included in the edge of the second region, or an arc extending along the arc included in the edge of the second region. The distance sensor according to claim 1, comprising:   3. The charge generation region according to claim 1, wherein an edge of the charge generation region includes a side extending in the first direction between the second regions adjacent to each other in the first direction. Distance sensor. The plurality of signal charge collection regions include first and second signal charge collection regions;
The first signal charge collection region is disposed in the second region provided on the first side extending in the first direction of the first region;
The second signal charge collection region is disposed in the second region provided on the second side extending in the first direction of the first region. The distance sensor as described in any one of 1-3. The plurality of signal charge collection regions include first and second signal charge collection regions;
The first and second signal charge collection regions are arranged in different second regions provided on a first side extending in the first direction of the first region. The distance sensor according to any one of claims 1 to 3. A plurality of unnecessary charge collection regions that are spaced apart from each other and collect unnecessary charges from the charge generation region;
An unnecessary charge collection gate electrode that selectively blocks and releases the flow of unnecessary charges from the charge generation region to the unnecessary charge collection region, and
The unnecessary charge collection region is arranged so that at least a part is included in the second region provided on the second side extending in the first direction of the first region. The distance sensor according to claim 5.   The first and second signal charge collection regions are disposed in different second regions provided on a second side extending in the first direction of the first region. The distance sensor according to claim 5. A plurality of unnecessary charge collection regions that are spaced apart from each other and collect unnecessary charges from the charge generation region;
An unnecessary charge collection gate electrode that selectively blocks and releases the flow of unnecessary charges from the charge generation region to the unnecessary charge collection region, and
The unnecessary charge collection region is arranged so that at least a part thereof is included in the second region provided on the first and second sides of the first region. Item 8. The distance sensor according to Item 7. An edge of the unnecessary charge collection region includes a side extending along the side included in the edge of the second region;
The unnecessary charge collection gate electrode is located between the charge generation region and the unnecessary charge collection region in the second region, and extends along the edge of the second region. The distance sensor according to claim 6 or 8. The distance sensor according to any one of claims 1 to 9,
A light source;
A drive circuit for applying a pulse drive signal to the light source;
A control circuit for supplying the transfer electrodes with charge transfer signals having phases different from each other in synchronization with the pulse drive signal;
A distance image sensor comprising: an arithmetic circuit that calculates a distance to an object from a signal read from the signal charge collection region.

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