Image sensing device and method of

• US 7,498,621 B2
• Filed: 06/05/2003
• Issued: 03/03/2009
• Est. Priority Date: 06/20/2002
• Status: Expired due to Term

• Current Assignee: Ams Sensors Singapore Pte. Ltd. (Ams-Osram AG)
• Original Assignee: MESA IMAGING AG (Ams-Osram AG)
• Inventors: Seitz, Peter
• Primary Examiner(s): Sefer; A.
• Assistant Examiner(s): Rodela; Eduardo A
• Application Number:
  US10/518,963
• Publication Number:
  US 20060108611A1
• Time in Patent Office: 2,098 Days
• Field of Search: 257/222, 257/290, 257/364, 257/E31.054, 438/48, 438/284
• US Class Current: 257/222
• CPC Class Codes: G01J 9/00 Measuring optical phase difference devices or arrangements for controlling the phase of light beams G02F1/01; Determining degree of coherence; Measuring optical wavelength spectrometry G01J3/00
• 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: H01L 27/14601 Structural or functional details thereof
• CPC Class Codes: H01L 31/113 being of the conductor-insulator-semiconductor type, e.g. metal-insulator-semiconductor field-effect transistor

Abstract

A two-dimensional, temporally modulated electromagnetic wavefield, preferably in the ultraviolet, visible or infrared spectral range, can be locally detected and demodulated with one or more sensing elements. Each sensing element consists of a resistive, transparent electrode (E) on top of an insulated layer (O) that is produced over a semiconducting substrate whose surface is electrically kept in depletion. The electrode (E) is connected with two or more contacts (C1; C2) to a number of clock voltages that are operated synchronously with the frequency of the modulated wavefield. In the electrode and in the semiconducting substrate lateral electric fields are created that separate and transport photogenerated charge pairs in the semiconductor to respective diffusions (D1; D2) close to the contacts (C1; C2). By repetitively storing and accumulating photocharges in the diffusions (D1; D2), electrical signals are generated that are subsequently read out for the determination of local phase shift, amplitude and offset of the modulated wavefield.

Claims

1. An image sensor element comprising:

a semiconductor substrate,

a radiation transparent insulating layer formed on the semiconductor substrate,

an electrode formed as a layer of transparent resistive material on the insulating layer, the transparent resistive material extending across a photosensitive part of the image sensor element in which incident light is converted into photogenerated charges,

a first contact adjacent to a first edge of the resistive layer,

a first diffusion region in the semiconductor substrate of opposite conductivity to the semiconductor substrate located adjacent to the first contact and biased to a higher potential than that of the first contact,

a second contact adjacent to a second edge, opposite the first edge, of the resistive layer,

a second diffusion region is in the semiconductor substrate of opposite conductivity to the semiconductor substrate located adjacent to the second contact and biased to a higher potential than that of the second contact,

means for applying an electrical potential between the first and second contacts, and

means for reading out the charge on the first and/or second diffusion regions;

wherein the resistive layer is rectangular; and

in which the contacts are arranged one at each side.

2. The image sensor element as claimed in claim 1, comprising four contacts each having a diffusion region adjacent thereto.

3. The image sensor element as claimed in claim 2, in which the contacts are arranged one at each corner.

4. The image sensor element as claimed in claim 2, in which two contacts are arranged on each of two opposite sides.

5. The image sensor element as claimed in claim 1, in which the resistive layer is square.

6. The image sensor element as claimed in claim 1, in which the insulating layer is between 1 nanometer (nm) and 1 micrometer (μ

m) thick.

7. The image sensor element as claimed in claim 1, in which the electrode has a sheet resistivity of greater than 10 Ohms (Ω

)/square.

8. The image sensor element as claimed in claim 1, in which the photosensitive part of the element is implemented in a semiconducting layer at the surface of the substrate, the surface semiconducting layer being of opposite conductivity to the substrate, the element further comprising means for biasing the surface semiconducting layer so that it is fully depleted.

9. The image sensor element as claimed in claim 8, in which the readout means is implemented in the surface semiconductor layer, the surface semiconductor layer is arranged to be connected to ground potential, and the semiconductor substrate is arranged to be connected to a potential such as to produce a deep depletion layer in the semiconductor substrate.

10. The image sensor element as claimed in claim 1, in which the read out means is implemented as a source follower with a pixel select transistor.

11. The image sensor element as claimed in claim 1, in which the readout means is implemented as a resettable charge amplifier with a pixel select transistor.

12. The image sensor element as claimed in claim 1, in which the readout means is implemented as a transconductance amplifier, for measuring the photocurrent at the first or second diffusion regions, with a pixel select transistor.

13. A device for the detection and demodulation of a modulated wavefield, comprising:

an image sensor including a one or two dimensional array of image sensor elements formed on a semiconductor substrate, each image sensor element comprising;

a radiation transparent insulating layer formed on the semiconductor substrate,

an electrode formed as a layer of transparent resistive material on the insulating layer, the transparent resistive material extending across a photosensitive part of the image sensor element in which incident light is converted into photogenerated charges,

a first contact adjacent to one a first edge of the resistive layer,

a first diffusion region in the semiconductor substrate of opposite conductivity to the semiconductor substrate located adjacent to the first contact and biased to a higher potential than that of the first contact,

a second contact adjacent to a second edge, opposite the first edge, of the resistive layer, and

a second diffusion region is in the semiconductor substrate of opposite conductivity to the semiconductor substrate located adjacent to the second contact and biased to a higher potential than that of the second contact;

a signal generator for supplying time dependent voltage patterns to the contacts on each of the image sensor element electrodes in synchronism with the modulation frequency of the incident wavefield to transport photocharges laterally from the photosensitive part of each of the image sensor elements to the corresponding diffusions on which photocharges are accumulated; and

a readout circuit for reading out the charges on the diffusions for use in calculating the modulation parameters of the incident modulated wave field;

wherein the resistive layer is rectangular; and

in which the contacts are arranged one at each side.

14. The device as claimed in claim 13, in which photocharges are accumulated over a plurality of periods of the modulation frequency of the incident wavefield.

15. The device as claimed in claim 13, in which each period of the modulation frequency is divided into a number of time intervals;

wherein a separate contact and diffusion region is provided in each image sensor element for each time interval.

16. The device as claimed in claim 13, comprising an evaluation unit for calculating the modulation parameters of the incident wavefield from the charges readout from the diffusions.

17. The image sensor element as claimed in claim 13, in which the insulating layer is between 1 nanometer (nm) and 1 micrometer (μ

) thick.

18. The image sensor element as claimed in claim 13, in which the electrode has a sheet resistivity of greater than 10 Ohms (Ω

)/square.

19. A method of detecting and demodulating modulated wavefields comprising the steps of:

a) illuminating an array of image sensing elements with the modulated wavefield, wherein each of the image sensing elements comprises;

a radiation transparent insulating layer,

an electrode formed as a layer of transparent resistive material on the insulating layer, the transparent resistive material extending across a photosensitive part of the image sensor element in which incident light is converted into photogenerated charges,

a first contact adjacent to one a first edge of the resistive layer,

a first diffusion region located adjacent to the first contact,

a second contact adjacent to a second edge, opposite the first edge, of the resistive layer, and

a second diffusion region located adjacent to the second contact;

b) dividing each period of the modulation frequency into a number of intervals;

c) providing a separate contact and corresponding diffusion region for each time interval;

d) transporting photoregenerated charge from the photosensitive part to the corresponding diffusion regions during each time interval and storing them therein;

e) reading out the stored charges from the diffusion regions; and

f) calculating demodulation parameters from the charges readout from the diffusion regions.

20. The image sensor element as claim in claim 19, wherein the resistive layer is rectangular.

21. The image sensor element as claim in claim 19, in which the contacts are arranged one at each side.

22. The method as claimed in claim 19, in which charges are accumulated in the diffusion regions over more than one period of the modulation frequency.

23. The method as claimed in claim 19, in which the wavefield is directed onto the array by optical elements.

24. The image sensor element as claimed in claim 19, in which the insulating layer is between 1 nanometer (nm) and 1 micrometer (Ω

) thick.

25. The image sensor element as claimed in claim 19, in which the electrode has a sheet resistivity of greater than 10 Ohms (Ω

)/square.

26. A method of determining the three dimensional shape of a reflective object comprising the steps of:

a) illuminating the object with a modulated light source;

b) imaging light reflected from the object onto an array of image sensor elements to form a two dimensional intensity modulated wavefield whose local phase represents local distance from the object to the detection device, wherein each of the image sensing elements comprises;

a radiation transparent insulating layer,

an electrode formed as a layer of transparent resistive material on the insulating layer, the transparent resistive material extending across a photosensitive part of the image sensor element in which incident light is converted into photogenerated charges,

a first contact adjacent to one a first edge of the resistive layer,

a first diffusion region located adjacent to the first contact,

a second contact adjacent to a second edge, opposite the first edge, of the resistive layer, and

a second diffusion region located adjacent to the second contact;

c) dividing each period of the modulation frequency into a number of time intervals;

d) providing a separate contact and corresponding diffusion region for each time interval;

e) transporting photoregenerated charges to the corresponding diffusion regions by applying a potential across the first contact and the second contact during each time interval and storing them therein;

f) reading out the stored photogenerated charges from the diffusion regions;

g) calculating the local phase of the modulated wavefield incident on the array; and

h) using the local phase information to determine the three dimensional shape of the object.

27. The image sensor element as claimed in claim 26, in which the insulating layer is between 1 nanometer (nm) and 1 micrometer (Ω

) thick.

28. The image sensor element as claimed in claim 26, in which the electrode has a sheet resistivity of greater than 10 Ohms (Ω

)/square.

29. An image sensor element comprising:

a semiconductor substrate,

a radiation transparent insulating layer formed on the semiconductor substrate,

an electrode formed as a layer of transparent resistive material on the insulating layer, the transparent resistive material extending across a photosensitive part of the image sensor element in which incident light is converted into photogenerated charges,

a first contact adjacent to a first edge of the resistive layer,

a first diffusion region in the semiconductor substrate of opposite conductivity to the semiconductor substrate located adjacent to the first contact,

a second contact adjacent to a second edge, opposite the first edge, of the resistive layer,

a second diffusion region in the semiconductor substrate of opposite conductivity to the semiconductor substrate located adjacent to the second contact,

a voltage generator for applying an electrical potential between the first and second contacts, and

a read-out circuit for reading out the photogenerated charges on the first and/or second diffusion regions;

wherein the resistive layer is rectangular; and

in which the contacts are arranged one at each side.

30. The image sensor element as claimed in claim 29, comprising four contacts each having a diffusion region adjacent thereto.

31. The image sensor element as claimed in claim 30, in which the contacts are arranged one at each corner.

32. The image sensor element as claimed in claim 29, in which two contacts are arranged on each of two opposite sides.

33. The image sensor element as claimed in claim 29, in which the resistive layer is square.

34. The image sensor element as claimed in claim 29, in which the insulating layer is between 1 nanometer(nm) and 1 micrometer (Ω

) thick.

35. The image sensor element as claimed in claim 29, in which the electrode has a sheet resistivity of greater than 10 Ohms (Ω

)/square.

36. The image sensor element as claimed in claim 29, in which the photosensitive part of the element is implemented in a semiconducting layer at the surface of the substrate, the surface semiconducting layer being of opposite conductivity to the substrate, the element further being biased to deplete the surface semiconducting layer.