PHOTOELECTRIC CONVERSION ELEMENT, LIGHT RECEIVING DEVICE, LIGHT RECEIVING SYSTEM, AND DISTANCE MEASURING DEVICE

• US 20120200842A1
• Filed: 10/01/2010
• Published: 08/09/2012
• Est. Priority Date: 10/07/2009
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Kamiyama, Tomoyuki, Korekado, Keisuke
• Granted Patent: US 8,947,645 B2
• Time in Patent Office: Days
• US Class Current: 356/5.03
• CPC Class Codes: G01B 11/026 by measuring distance between sensor and object G01B11/0608 takes precedence
• CPC Class Codes: G01S 17/894 3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar
• CPC Class Codes: G01S 7/4863 Detector arrays, e.g. charge-transfer gates

Abstract

A first photoelectric conversion element, which detects light and converts the light into photoelectrons has: one MOS diode having an electrode formed on a semiconductor base body with an insulator therebetween; and a plurality of embedded photodiodes formed in the semiconductor base body. The electrode of the MOS diode has, when viewed from the upper surface, a comb-like shape wherein a plurality of branch portions are branched from one electrode portion. Each of the embedded photodiodes is disposed to nest between the branch portions of the electrode when viewed from the upper surface.

Claims

1. A photoelectric conversion element for detecting light and converting the light into photoelectrons, comprising:

one MOS diode having an electrode formed on a semiconductor substrate with an insulator therebetween; and

plural embedded photodiodes formed in the semiconductor substrate,

wherein the electrode of the MOS diode has a comb-like shape when viewed from an upper surface thereof, in which plural branch portions are branched from one electrode portion, and

the plural embedded photodiodes are nested, respectively, between the branch portions of the electrode when viewed from the upper surface thereof.

2. The photoelectric conversion element according to claim 1, wherein the potential under the electrode of the MOS diode is controlled, such that the photoelectrons generated by photoelectric conversion at the embedded photodiodes migrate toward the MOS diode.

3. The photoelectric conversion element according to claim 1, wherein within the MOS diode, a portion corresponding to a base of the one electrode portion of the electrode is constituted as a charge accumulating unit.

4. The photoelectric conversion element according to claim 1, wherein the plural branch portions of the electrode in the MOS diode are rectangular shaped respectively.

5. The photoelectric conversion element according to claim 1, wherein each of the plural branch portions of the electrode in the MOS diode are shaped so as to become gradually greater in width toward the one electrode portion as viewed from the upper surface thereof.

6. The photoelectric conversion element according to claim 1, wherein power supply terminals of each of the plural branch portions of the electrode in the MOS diode (Ware formed at positions maximally separated from the charge accumulating unit as viewed from the upper surface thereof.

7. The photoelectric conversion element according to claim 1, further comprising:

one first MOS diode having a first electrode formed on the semiconductor substrate with the insulator therebetween; and

plural second MOS diodes having respective second electrodes formed on the semiconductor substrate with the insulator therebetween,

wherein the second electrodes of the plural second MOS diodes are separated respectively from the first electrode, and are nested respectively between the plural branch portions of the first electrode when viewed from an upper surface thereof, and

the embedded photodiodes are formed between the first MOS diode and the second MOS diodes.

8. A light receiving device that acquires luminance information of incident light, comprising:

a photoelectric conversion element, which detects and converts the incident light into photoelectrons;

a charge accumulating unit for accumulating photoelectrons generated by the photoelectric conversion element;

a capacitor that stores the photoelectrons at a fixed time period;

a charge discharging unit that discharges the photoelectrons;

a first MOS-type switching element disposed between the charge accumulating unit and the capacitor for causing the photoelectrons accumulated in the charge accumulating unit to migrate toward the capacitor; and

a second MOS-type switching element disposed between the charge accumulating unit and the charge discharging unit for controlling discharge of the photoelectrons from the charge accumulating unit to the charge discharging unit,

wherein the photoelectric conversion element comprises;

one MOS diode having an electrode formed on a semiconductor substrate with an insulator therebetween; and

plural embedded photodiodes formed in the semiconductor substrate,

wherein the electrode of the MOS diode has a comb-like shape when viewed from an upper surface thereof, in which plural branch portions are branched from one electrode portion,

the plural embedded photodiodes are nested, respectively, between the plural branch portions of the electrode when viewed from the upper surface thereof, and

the photoelectrons from the photoelectric conversion element are transferred to the capacitor by selectively controlling opening/closing of the first switching element and the second switching element, whereby luminance information of incident light is acquired based on an amount (charge amount) of the photoelectrons transferred to the capacitor.

9. The light receiving device according to claim 8, wherein:

the charge accumulating unit is connected to the photoelectric conversion element; and

the charge discharging unit is disposed to confront the capacitor while sandwiching the charge accumulating unit therebetween.

10. The light receiving device according to claim 8, wherein the capacitor comprises one of a MIM capacitor, a MOS capacitor, an embedded photodiode structure, or a pn junction parasitic capacitance.

11. The light receiving device according to claim 8, wherein at least the charge accumulating unit, the first switching element, the second switching element, and the capacitor are formed in a light shielded region.

12. A light receiving device that acquires luminance information of incident light, comprising:

a photoelectric conversion element, which detects and converts the incident light into photoelectrons;

a charge accumulating unit for accumulating photoelectrons generated by the photoelectric conversion element;

a first capacitor and a second capacitor that store the photoelectrons at a fixed time period;

a charge discharging unit that discharges the photoelectrons;

a first MOS-type switching element disposed between the charge accumulating unit and the first capacitor for allocating the photoelectrons accumulated in the charge accumulating unit selectively to the first capacitor; and

a second MOS-type switching element disposed between the charge accumulating unit and the second capacitor for allocating the photoelectrons accumulated in the charge accumulating unit selectively to the second capacitor; and

a third MOS-type switching element for controlling discharge of the photoelectrons from the charge accumulating unit to the charge discharging unit,

wherein the photoelectric conversion element comprises;

one MOS diode having an electrode formed on a semiconductor substrate with an insulator therebetween; and

plural embedded photodiodes formed in the semiconductor substrate,

wherein the electrode of the MOS diode has a comb-like shape when viewed from an upper surface thereof, in which plural branch portions are branched from one electrode portion,

the plural embedded photodiodes are nested, respectively, between the plural branch portions of the electrode when viewed from the upper surface thereof, and

the photoelectrons from the photoelectric conversion element are transferred to the first capacitor and the second capacitor by selectively controlling ON/OFF states of the first through third switching elements, whereby luminance information of incident light is acquired based on an amount (charge amount) of the photoelectrons transferred to the first capacitor and the second capacitor.

13. The light receiving device according to claim 12, wherein:

the charge accumulating unit is connected to the photoelectric conversion element;

the charge discharging unit is disposed to confront the photoelectric conversion element while sandwiching the charge accumulating unit therebetween; and

the first capacitor and the second capacitor are disposed to mutually confront one another while sandwiching the charge accumulating unit therebetween.

14. The light receiving device according to claim 12, wherein the first capacitor and the second capacitor comprise one of a MIM capacitor, a MOS capacitor, an embedded photodiode structure, or a pn junction parasitic capacitance.

15. The light receiving device according to claim 12, wherein at least the charge accumulating unit, the first through third switching elements, the first capacitor, and the second capacitor are formed in a light shielded region.

16. A light receiving system comprising:

a light emitting device that irradiates pulsed light with respect to an object;

a light receiving device that receives reflected light of the pulsed light and carries out an output responsive to a received light amount; and

a controller that controls the light emitting device and the light receiving device,

wherein the light receiving device comprises;

a photoelectric conversion element, which detects and converts the reflected light into photoelectrons;

a charge accumulating unit for accumulating photoelectrons generated by the photoelectric conversion element;

a pair of capacitors that store the photoelectrons at a fixed time period;

a charge discharging unit that discharges the photoelectrons;

a pair of MOS-type switching elements disposed between the charge accumulating unit and the pair of capacitors for selectively allocating the photoelectrons accumulated in the charge accumulating unit to the pair of capacitors in synchronism with driving of the light emitting device; and

a third MOS-type switching element for controlling discharge of the photoelectrons from the charge accumulating unit to the charge discharging unit in synchronism with driving of the light emitting device,

wherein the photoelectric conversion element comprises;

one MOS diode having an electrode formed on a semiconductor substrate with an insulator therebetween; and

plural embedded photodiodes formed in the semiconductor substrate,

wherein the electrode of the MOS diode has a comb-like shape when viewed from an upper surface thereof, in which plural branch portions are branched from one electrode portion,

the plural embedded photodiodes are nested, respectively, between the plural branch portions of the electrode when viewed from the upper surface thereof, and

the controller;

turns ON a first switching element from among the pair of switching elements and transfers the photoelectrons from the photoelectric conversion element to a first capacitor from among the pair of capacitors, in a first period that resides within a period in which the pulsed light from the light emitting device is not irradiated,

turns ON a second switching element from among the pair of switching elements and transfers the photoelectrons from the photoelectric conversion element to a second capacitor from among the pair of capacitors, in a second period that resides within a period in which the pulsed light from the light emitting device is irradiated,

turns ON the third switching element and controls the charge discharging unit to discharge the photoelectrons from the photoelectric conversion element, within a period outside of the first period and the second period, and

acquires luminance information of the reflected light based on an amount (charge amount) of the photoelectrons transferred to the first capacitor and an amount (charge amount) of the photoelectrons transferred to the second capacitor.

17. The light receiving system according to claim 16, further comprising a power source and a MOS-type first reset switch and a MOS-type second reset switch for setting potentials of the first capacitor and the second capacitor to initial potentials.

18. The light receiving system according to claim 16, further comprising a first amplifier and a second amplifier for converting respectively to electric signals of a level corresponding to potentials based on the amount of photoelectrons stored in the first capacitor and the second capacitor.

19. The light receiving system according to claim 16, further comprising:

a first charge holding unit and a second charge holding unit constituted by a MOS capacitor or an embedded photodiode structured parasitic capacitance, for temporarily storing the photoelectrons transferred by the first switching element and the second switching element; and

a first charge transfer unit and a second charge transfer unit constituted by MOS-type switching elements for transferring the photoelectrons, which are temporarily stored respectively in the first charge holding unit and the second charge holding unit, to the first capacitor and the second capacitor.

24. The light receiving system according to claim 16, wherein a structural element of the light receiving device is constituted by a structural element of one pixel portion of a line sensor array or a two dimensional image sensor array in which a plurality of pixels are provided.

20. A light receiving system comprising:

a light emitting device that irradiates pulsed light with respect to an object;

a light receiving device that receives reflected light of the pulsed light and carries out an output responsive to a received light amount; and

a controller that controls the light emitting device and the light receiving device,

wherein the light receiving device comprises;

a photoelectric conversion element, which detects and converts the reflected light into photoelectrons;

a charge accumulating unit for accumulating photoelectrons generated by the photoelectric conversion element;

first through fourth capacitors that store the photoelectrons at a fixed time period;

a charge discharging unit that discharges the photoelectrons;

first through fourth MOS-type switching elements disposed between the charge accumulating unit and the first through fourth capacitors for allocating the photoelectrons to the first through fourth capacitors in synchronism with irradiation of the pulsed light; and

a fifth MOS-type switching element disposed between the charge accumulating unit and the charge discharging unit for controlling supply of the photoelectrons from the charge accumulating unit to the charge discharging unit

wherein the photoelectric conversion element comprises;

one MOS diode having an electrode formed on a semiconductor substrate with an insulator therebetween; and

plural embedded photodiodes formed in the semiconductor substrate,

wherein the electrode of the MOS diode has a comb-like shape when viewed from an upper surface thereof, in which plural branch portions are branched from one electrode portion,

the plural embedded photodiodes are nested, respectively, between the plural branch portions of the electrode when viewed from the upper surface thereof, and

the controller;

controls irradiation of the pulsed light by the light emitting device, and ON/OFF switching of the first through fourth switching elements,

turns ON the fifth switching element and discharges the photoelectrons to the charge discharging unit at a time when all of the first through fourth switching elements are OFF, and

acquires luminance information of the reflected light based on an amount (charge amount) of the photoelectrons transferred to the first through fourth switching elements.

21. The light receiving system according to claim 20, further comprising a power source and first through fourth MOS-type first to fourth reset switches for setting potentials of the first through fourth capacitors to initial potentials.

22. The light receiving system according to claim 20, further comprising first through fourth amplifiers for converting respectively to electric signals of levels corresponding to potentials based on the amount of photoelectrons stored in the first through fourth capacitors.

23. The light receiving system according to claim 20, further comprising:

first through fourth charge holding units constituted by a MOS capacitor or an embedded photodiode structured parasitic capacitance, for temporarily storing the photoelectrons transferred by the first through fourth switching elements; and

first through fourth charge transfer units constituted by MOS-type switching elements for transferring the photoelectrons, which are temporarily stored respectively in the first through fourth charge holding units, respectively to the first through fourth capacitors.

25. A distance measuring device comprising:

a light emitting device that irradiates pulsed light with respect to an object;

a light receiving device that receives reflected light of the pulsed light and carries out an output responsive to a received light amount;

a controller that controls the light emitting device and the light receiving device; and

an arithmetic processor for calculating a distance to the object by a time-of-flight method using the output of the light receiving device,

wherein the light receiving device comprises;

a photoelectric conversion element, which detects and converts the reflected light into photoelectrons;

a charge accumulating unit for accumulating photoelectrons generated by the photoelectric conversion element;

first through fourth capacitors that store the photoelectrons at a fixed time period;

a charge discharging unit that discharges the photoelectrons;

first through fourth MOS-type switching elements disposed between the charge accumulating unit and the first through fourth capacitors for allocating the photoelectrons to the first through fourth capacitors in synchronism with irradiation of the pulsed light; and

a fifth MOS-type switching element disposed between the charge accumulating unit and the charge discharging unit for controlling supply of the photoelectrons from the charge accumulating unit to the charge discharging unit,

wherein the photoelectric conversion element comprises;

one MOS diode having an electrode formed on a semiconductor substrate with an insulator therebetween; and

plural embedded photodiodes formed in the semiconductor substrate,

wherein the electrode of the MOS diode has a comb-like shape when viewed from an upper surface thereof, in which plural branch portions are branched from one electrode portion, and

the plural embedded photodiodes are nested, respectively, between the plural branch portions of the electrode when viewed from the upper surface thereof, and

wherein assuming that;

an irradiation start time of the pulsed light is taken as time Teu,

an irradiation end time of the pulsed light is taken as time Ted,

an incidence end time of the reflected light with respect to the photoelectric conversion element is taken as time Trd,

ON times of the first through fourth switching elements are taken as times Tg1u, Tg2u, Tg3u, Tg4u,

OFF times of the first through fourth switching elements are taken as times Tg1d, Tg2d, Tg3d, Tg4d,

a time period from the time Tg1u to the time Tg1d is taken as P1,

a time period from the time Tg2u to the time Tg2d is taken as P2,

a time period from the time Tg3u to the time Tg3d is taken as P3,

a time period from the time Tg4u to the time Tg4d is taken as P4,

a time period from the time Tg4u to the time Trd is taken as Psr,

an amount of the photoelectrons stored in the first capacitor within the time period P1 is taken as a charge amount Q1,

an amount of the photoelectrons stored in the second capacitor within the time period P2 is taken as a charge amount Q2,

an amount of the photoelectrons stored in the third capacitor within the time period P3 is taken as a charge amount Q3,

an amount of the photoelectrons stored in the fourth capacitor within the time period P4 is taken as a charge amount Q4,

a time period from irradiation of the pulsed light to reflection of the pulsed light by the object and until the reflected light returns is taken as a round-trip time period Δ

P, and the distance between the object and the light emitting device and the light receiving device is taken as a distance D,

then the controller;

controls irradiation of the pulsed light from the light emitting device, and ON/OFF switching of the first through fourth switching elements, such that

(1) P1=P3,

(2) P2=P4, and

(3) Tg1u<

Tg1d≦

Tg2u<

Tg2d≦

Teu<

Tg3u<

Tg3d≦

Tg4u≦

Ted<

Tg4d, or, Teu<

Tg3u<

Tg3d≦

Tg4u≦

Ted<

Tg4d<

Tg1u<

Tg1d≦

Tg2u<

Tg2d, and

turns ON the fifth switching element and discharges the photoelectrons to the charge discharging unit at a time when all of the first through fourth switching elements are OFF, and

the arithmetic processor;

acquires luminance information of the reflected light in the time period P3 based on a difference between the charge amount Q3 that is stored in the third capacitor, which corresponds to ambient light and the reflected light, and the charge amount Q1 that is stored in the first capacitor, which corresponds to the ambient light,

acquires luminance information of the reflected light in the time period Psr based on a difference between the charge amount Q4 that is stored in the fourth capacitor, which corresponds to the ambient light and the reflected light, and the charge amount Q2 that is stored in the second capacitor, which corresponds to the ambient light,

determines a ratio between the luminance information of the reflected light in the time period P3 and the luminance information of the reflected light in the time period Psr, and calculates the round-trip time period Δ

P based on the ratio between the time period P3 and the time period Psr, and

measures the distance D based on the round-trip time period Δ

P.

26. The distance measuring device according to claim 25, wherein the round-trip time period Δ

P is calculated based on the following equation (1), when the time Ted and the time Tg4u are equal,

Δ

P={(Q4−

Q2)/(Q3−

Q1)}×

P3 

 

(1)

and the round-trip time period Δ

P is calculated based on the following equation (2), when the time Ted is later than the time Tg4u,

Δ

P=[(Q4−

Q2)/(Q3−

Q1)]×

P3−

(Ted−

Tg4u) 

 

(2)

27. The distance measuring device according to claim 25, wherein:

the controller irradiates the pulsed light multiple times to the light emitting device in each of respective measurement cycles; and

the arithmetic processor calculates the round-trip time period Δ

P using the charge amounts Q1 to Q4 after the photoelectrons have been stored multiple times respectively in the first through fourth capacitors.