DE102013109506A1 - Directionally sensitive photosensor for detecting the direction of incidence of light - Google Patents

Abstract

The invention relates to a direction-sensitive photosensor for detecting the direction of incidence of light. The sensor comprises a semiconductor substrate (01) in which a plurality of photosensitive sensor regions (04) are formed. At least two photosensitive sensor regions (04) are formed in surfaces (03) inclined to the main extension plane of the semiconductor substrate, whose surface normals (n1, n2) are not parallel to one another.

Description

The present invention relates to a direction-sensitive photosensor, which in particular serves to detect the direction of incidence of light incident on the sensor. The photosensor can also determine in known manner, the illuminance of the incident light, if desired. For this purpose, a plurality of light-sensitive sensor regions are formed in such a photosensor, for example as photodiodes.

In the context of the present invention, the term "light" is widely understood and, in addition to the visible to humans electromagnetic radiation and the adjacent wavelength ranges of infrared and ultraviolet radiation. The field of application of the photosensor is limited in this respect only by the spectral sensitivity of the respectively formed sensor areas.

Photosensors are known in many different embodiments and are used in the prior art for very different applications, which in the broadest sense is about the detection of electromagnetic radiation, in particular visible light. A special application case is the determination of the direction of incidence of light rays, as seen from the position of the photosensor. The knowledge of the direction of incidence of sunlight, for example, for the control of air conditioning and shading systems and the sun-related tracking of solar energy systems desirable, the corresponding systems are controlled not only in dependence on the illuminance but also taking into account the direction of incidence of sunlight. To determine the direction of incidence of light, different concepts are pursued in the construction of known photosensors.

The WO 2012/014236 A1 describes a quadrant photodetector with four photosensors, which are arranged in different quadrants and are covered by a partially opaque mask. Depending on the direction of incidence of the light to be detected, the opaque mask casts a narrow beam of light onto different areas in the quadrant arrangement so that the light incident direction can be deduced from the illuminance detected at the individual photosensors. The manufacture of such a multi-part quadrant photodetector is relatively expensive and requires either a high precision or at least subsequently a considerable calibration effort.

The DE 10 2010 064 140 A1 describes a radiation direction sensor and a method for determining the angle of incidence of a radiation source. In this sensor as well, a pattern formed on a mask is projected onto underlying sensors in order to calculate the direction of incidence of the light from the local illuminance on a sensor surface.

The WO 2011/126316 A2 follows a different concept and describes a sensor for detecting sunlight. The sensor uses a solid base body on which numerous mutually angularly arranged outer surfaces are provided. On these outer surfaces individual photosensors are mounted, which are irradiated differently depending on the direction of incidence of the sunlight. The production of this sensor is complicated and leads to an increased susceptibility to error of the entire sensor arrangement, if the individual photosensors are not accurately positioned on the outer surfaces.

A similar approach follows the DE 38 21 743 A1 , which describes a sensor for detecting the solar radiation in a passenger compartment of a motor vehicle. In this case, at least two optically separate photodiodes are arranged on a base body, to which the light irradiation of two mutually angled outer surfaces is supplied. Also, this sensor has a complicated structure, which leads to the disadvantages already mentioned above.

In the DE 44 23 778 A1 For example, a measuring system with four photosensitive components for determining the spatial angle of error of a point light source is described. For this purpose, four sensors are arranged, for example, concentrically on the surface of a hemisphere or on the outer surfaces of a truncated pyramid. The different illuminances measured at the sensors are used to calculate the angle of incidence. Although it is stated in this document that, in particular in a truncated pyramid base body high precision of mutually inclined directions of the mounted on the base body sensors is possible, but this also depends heavily on the manufacturing accuracy. If the sensors are not positioned exactly on the pyramid surfaces, this inevitably affects the measured illuminance. Due to the necessary mounting of the sensors on the truncated pyramid, today's miniaturization of such a sensor is also limited. Finally, measurement errors of the overall arrangement result from the inevitable scattering of the sensitivity of the individual sensors.

The object of the present invention, starting from the prior art is to provide an improved directionally sensitive photosensor, with the one hand, the direction of incidence of incident on the sensor light can be determined with high accuracy, on the other hand, however, is inexpensive to manufacture and opens up the possibility of extensive miniaturization ,

The above object is achieved by a direction-sensitive photosensor according to the appended claim 1.

The photosensor according to the invention is characterized in that at least two light-sensitive sensor regions are formed in surfaces inclined to the main extension plane of the semiconductor substrate, wherein the surface normals of these inclined surfaces do not run parallel to one another.

Unlike the known direction-sensitive photosensors therefore not individual photosensors are mechanically arranged on a common carrier, but there is a direct formation of the photosensitive sensor areas in the semiconductor carrier substrate, but on mutually angled surfaces which are inclined to the main extension plane or wafer surface of the semiconductor substrate respectively are. As a result of the integration of the photosensitive sensor regions into the semiconductor substrate, the otherwise usual assembly step is completely eliminated. Instead, the known manufacturing technologies of the semiconductor industry are used to form the photosensitive sensor regions directly in the substrate.

A significant advantage of the integration of a plurality of light-sensitive sensor regions in differently inclined surfaces of the semiconductor substrate is thus to be seen in the simplification of the production steps using known technologies. In this context, however, it also becomes clear that the solution according to the invention could only be found by exceeding the limits hitherto seen in the art. While the planar design of a single photosensor into a semiconductor carrier substrate was basically known, even the arrangement of any electronic component in a surface inclined to the main extension plane of the semiconductor substrate causes difficulties. Such difficulties have recently been overcome by corresponding photolithographic fabrication technologies. Thus, the production of a single photo sensor in a surface inclined to the semiconductor substrate is no longer a fundamental problem for the person skilled in the art, since the corresponding production technologies are available to him, so that a detailed description can be omitted here. However, until the invention, there were no solutions to form a plurality of inclined surfaces in the semiconductor substrate, which are again arranged at an angle to each other, and there to integrate each directly photosensitive sensor areas.

In a preferred embodiment of the present invention, the surface normals of the photosensitive sensor regions to the normal of the semiconductor substrate are at an angle between 5 ° to 85 °, preferably 30 ° to 60 °, more preferably 45 ° to 55 ° and especially 45 ° or 54.7 ° , At an angle of 45 °, a high sensitivity is assumed. An angle of 54.7 ° is desirable, as it can be generated relatively easily by anisotropic etching processes (eg, with potassium hydroxide (KOH)) on silicon surfaces with crystal orientation (100).

Particularly preferably, the inclined surfaces are arranged in the semiconductor substrate such that together they form an at least partially pyramidal depression whose light-open base lies in the main extension plane of the semiconductor substrate. Such a recess in pyramidal shape can be produced in the usual semiconductor substrates with known production technologies.

A particularly preferred embodiment is characterized in that the light-open base of the pyramid-shaped depression faces a preferably parallel extending top surface, so that a hollow truncated pyramid is formed. In this top surface, one or more openings are introduced in the ordinary manufacturing process, which completely penetrate the semiconductor substrate and in which through-contacts can be passed through in a subsequent process step. These plated-through holes allow the electrical contacting of the connection sites of the photosensitive sensor regions with interconnects that run on the back side of the semiconductor carrier substrate, that is to say opposite to the light-open base surface of the truncated pyramid.

In modified embodiments, a larger area of the semiconductor substrate is removed by semiconductor technology steps, so that an increase is formed over the remaining base area of the semiconductor substrate on which the inclined areas are arranged with the photosensitive sensor areas. Preferably, this increase also has a pyramidal shape, which in this case, however, is raised above the main extension plane of the semiconductor substrate. Such a design may be advantageous if the light to be detected in a very small angle to the plane of the semiconductor substrate impinges on the sensor and therefore could occur only reduced in a depression in the substrate. Due to the raised design of the photosensitive sensor regions, it is even possible to detect light components which occur parallel to the main extension plane of the semiconductor substrate. The other advantages, in particular the monolithic design of the entire sensor arrangement, still remain.

The photosensitive sensor regions are preferably designed as photodiodes. In a photosensitive sensor region, a single photodiode or an array of photodiodes can be arranged.

Further advantages, details and developments of the present invention will become apparent from the following description of preferred embodiments, with reference to the drawings. Show it:

1 a schematic sectional view of a direction-sensitive photosensor according to the invention with two photosensitive sensor areas;

2 a schematic representation of eight different embodiments of the directional photosensor with electrical connections;

3 a simplified perspective view of an embodiment of the photosensor with a truncated pyramidal elevation over the carrier substrate;

4 a perspective view of an embodiment of the photosensor with a pyramidal depression in the semiconductor substrate;

5 a perspective view of an embodiment of the photosensor with a recess in truncated pyramid and with through-hole.

1 shows in a simplified sectional view of the basic structure of the direction-sensitive photosensor according to the invention. Based on this representation, the corresponding angular relationships of the relevant surfaces and the mathematical relationships to be considered in the determination of the direction of incidence of light incident on the sensor are explained below.

The photosensor first comprises a semiconductor substrate 01 which forms the carrier of the sensor. The semiconductor substrate is preferably silicon and fabricated as part of a wafer. With the known semiconductor technologies, the substrate can be processed so that a plurality of corresponding photosensors can be produced in parallel on an ordinary wafer. By erosive methods, such as etching, is in the semiconductor substrate 01 a depression 02 introduced, so that the forming inner surfaces of the recess are inclined to the main extension plane of the semiconductor substrate. The inclination can be easily described by the corresponding surface normals, which in 1 were drawn. The surface normal of the semiconductor substrate 01 is marked with n, while the surface normals of the two inclined surfaces 03 are denoted by n ₁ and n _2, respectively.

In the in 1 illustrated simple embodiment is a wedge-shaped recess 02 shaped, the only two inclined surfaces 03 has. The inclination angle α of the inclined surfaces 03 spans between the surface normal n of the semiconductor substrate and the surface normal n ₁ , n _{2 of} the inclined surfaces. The depth of the depression 02 in the semiconductor substrate 01 is primarily determined by the required area for the photosensitive sensor areas to be formed.

In the inclined areas 03 become conventional photosensitive sensor areas by conventional semiconductor technology steps 04 formed, for example, photodiodes. The detection direction of the photosensitive sensor areas 04 is substantially parallel with the surface normal n ₁ , n _{2 of} the inclined surfaces.

By arrows 06 symbolized light is incident on the photosensor at an angle β (with respect to n). The two photosensitive sensor areas 04 In the case of normal incidence of light (ie, parallel to the respective surface normal n ₁ , n _{2 of} the inclined surfaces), the same maximum signal S _{max would} respectively be produced. As a first approximation, the photosensitive sensor areas provide 04 a signal reduced by the cosine of the angle of incidence of the light on its surface, such that S ₁ = S _max cos (D - E) S ₂ = S _max cos (D + E)

By forming the signal ratio S ₁ / S ₂ eliminates the dependence of S _max and the angle of incidence β, which corresponds to the desired angle of incidence of the light, is obtained by switching and series expansion of the above cosine terms. As a determining size remains in addition to the sensor signals S ₁ , S ₂ still dependent on the type of photo sensor inclination angle α of the inclined surfaces 03 opposite the main extension plane of the semiconductor substrate. If only small variations in the manufacturing processes occur, can on one Calibration of the photo sensor may be omitted, since only the signal ratios of the photosensitive sensor areas are significant. For the possibly necessary compensation of tolerances within the sensor, a one-time calibration after the manufacturing process can be performed.

2 shows simplified sectional views of eight exemplary embodiments of the directional photosensor. Due to the selected sectional view are always only two inclined surfaces 03 to see, which arise in the simplest case of a wedge-shaped depression. As will be explained in more detail below, modified shapes of the recess are possible, so that more than two inclined surfaces are available, each with light-sensitive sensor regions formed therein. As can further be seen, the photosensitive sensor areas must 04 via electrical connections 07 be contacted.

While at the in 2 variant I shown the inclined surfaces 03 converge at its inner end, so that there is a wedge-shaped cross section, in the variant II is a modified position of the inclined surfaces 03 chosen so that a cross section in the form of a parallelogram for the recess 02 is trained. This creates an inner cover surface 08 which is a translucent base 09 opposite. In the drawn variant III is in the area of the top surface 08 another light-sensitive sensor area is provided, which can be included in the signal evaluation. The variant IV is characterized by the fact that the top surface 08 a half-life substrate 01 piercing opening 11 owns, which in turn electrical connections 07 on the underside of the semiconductor substrate 01 are plated through.

Variants V, VI and VII of in 2 illustrated embodiments differ from the aforementioned designs basically in that the inclined surfaces 03 are not inclined into the semiconductor substrate, but rise above the surface of the semiconductor substrate. Again, be on the sloping surfaces 03 the photosensitive sensor areas 04 educated. Again, acute or blunt tapering forms of elevation are possible.

At light incidence angles greater than the angle of inclination of the inwardly directed sensor surfaces (β> α), the areas illuminated by the light are no longer directly illuminated. An evaluation of the light incidence angle from the sensor signals is difficult or impossible. In order to be able to carry out clear angles of incidence determination in such situations, if necessary, the sensor can be modified again. This shows the construction variant VIII of 2 , which is a combination of inward and outward inclined surfaces 03 used. The raised photosensitive surfaces outside the hollow pyramid are preferably aligned parallel to the side surfaces of the hollow pyramid, but are not (partially) shaded even in low light incidence. In the case of large angles of incidence (β> α), the angle of incidence can thus be determined from the signal ratios of the unshaded raised area and the partially shaded hollow pyramid area aligned parallel thereto. In this way, the evaluable light incidence angle range can be extended to almost 90 °. Variant VIII represents an extension of Variant I, but can also be easily transferred to other variants (eg II, III or IV).

3 shows a perspective view of a preferred embodiment of the photosensor according to the invention. In this embodiment, four inclined surfaces 03 to one over the carrier substrate 01 assembled uplifting pyramid. It should be remembered that the inclined surfaces are not to be produced by assembly processes, but arise within the framework of corresponding structuring processes of the semiconductor substrate. On each of the inclined surfaces 03 is at least one photosensitive sensor area 04 educated. The electrical contact is made via the electrical connections 07 , which are guided in a known manner on the surface of the semiconductor substrate.

4 shows a modified embodiment of the photosensor according to the invention, in which four inwardly inclined surfaces 03 in the semiconductor substrate 01 are formed. This creates an inwardly facing hollow pyramid, whereby here on each inwardly inclined surface 03 one or more photosensitive sensor areas 04 are arranged.

5 shows a further modified embodiment of the photosensor, which in turn inclined inwardly surfaces 03 used to form a hollow pyramid in the semiconductor substrate. The difference to the embodiment according to 4 is mainly seen in the fact that in the inner deck surface 08 the pyramidal shape the piercing opening 11 is provided, through which four vias for the electrical connection of the four sensor areas 04 are guided. The implementation of the electrical contacts on the back of the wafer has the particular advantage that no wires or similar protruding lines are required for the electrical connection of the sensor. This also applies to the substrate connection (ground contact), which can also be easily connected from the back. Correspondingly configured components can be used in the so-called "surface mounted device" method (SMD) are set directly on a printed circuit board.

The person skilled in the art will recognize that structural modifications of the described photosensor are easily possible. For special applications, it is also conceivable that the recesses formed in the semiconductor substrate are closed by a transparent material, in order to allow the incidence of light unhindered, however, to protect the sensitive areas from other environmental influences.

In addition, the angle measuring range and the angle sensitivity of the sensor can be influenced in a targeted manner and optimized for specific applications by means of a specifically set shape of the covering material. If the cover z. B. lens-shaped, light from larger incident angle ranges can be performed on the inclined photodiodes, whereby the measuring range can be extended.

LIST OF REFERENCE NUMBERS

01

Semiconductor substrate

02

deepening

03

inclined surfaces

04

photosensitive sensor areas

05

06

light

07

Electrical connections

08

cover surface

09

Floor space

10

11

piercing opening

n

Surface normal of the semiconductor substrate

n ₁ , n ₂

Surface normals of the inclined surfaces

α

 Inclination angle of the inclined surfaces

β

 Angle of incidence of the light

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2012/014236 A1 [0004]
• DE 102010064140 A1 [0005]
• WO 2011/126316 A2 [0006]
• DE 3821743 A1 [0007]
• DE 4423778 A1 [0008]

Claims (10)

Direction-sensitive photosensor for detecting the direction of incidence of light incident on the photosensor, comprising a semiconductor substrate ( 01 ), in which a plurality of photosensitive sensor areas ( 04 ), characterized in that at least two photosensitive sensor areas ( 04 ) in the main extension plane of the semiconductor substrate inclined surfaces ( 03 ), whose surface normals (n ₁ , n ₂ ) are not parallel to each other, are formed. Photosensor according to claim 1, characterized in that the photosensitive sensor areas ( 04 ) in four to the main extension plane of the semiconductor substrate ( 01 ) inclined surfaces ( 03 ) are formed, with adjacent surfaces ( 03 ) are each perpendicular to each other. Photosensor according to claim 1 or 2, characterized in that the surface normals (n ₁ , n ₂ ) of the inclined surfaces ( 03 ) with the photosensitive sensor areas ( 04 ) to the normal (s) of the semiconductor substrate ( 01 ) have an inclination angle α of 30 ° to 60 °. Photosensor according to one of claims 1 to 3, characterized in that in the semiconductor substrate ( 01 ) an at least partially pyramidal depression ( 02 ), the light-open surface ( 09 ) in the main extension plane of the semiconductor substrate ( 01 ) and in their inclined side surfaces ( 03 ) the photosensitive sensor areas ( 04 ) are formed. Photosensor according to claim 4, characterized in that the pyramidal recess ( 02 ) has the shape of a truncated pyramid whose light-open surface ( 09 ) opposite top surface ( 08 ) at least one of the semiconductor substrate ( 01 ) penetrating opening ( 11 ), through which one or more plated-through holes are guided, which are electrically connected to connection points of the light-sensitive sensor regions ( 04 ) are connected. Photosensor according to one of claims 1 to 3, characterized in that on the semiconductor substrate ( 01 ) an at least partially pyramidal elevation is formed, whose base area in the main extension plane of the semiconductor substrate ( 01 ) and in their outwardly inclined surfaces ( 03 ) the photosensitive sensor areas ( 04 ) are formed. Photosensor according to one of claims 1 to 6, characterized in that the semiconductor substrate is a silicon semiconductor. Photosensor according to one of claims 1 to 7, characterized in that the photosensitive sensor areas ( 04 ) are formed as photodiodes. Photosensor according to one of claims 1 to 8, characterized in that the to the main extension plane of the semiconductor substrate ( 01 ) inclined surfaces ( 03 ) are formed by semiconductor technology manufacturing steps, in particular etching processes. Photosensor according to one of claims 1 to 9, characterized in that it is constructed monolithically.

Images