Light sensor

Abstract

The invention discloses a light sensor which comprises a light-emitting element and a light-receiving element. The light-emitting element is used for emitting a light signal. The light receiving element comprises a light sensing layer and an intermediary layer, and the intermediary layer is arranged on the light sensing layer along a vertical direction. A plurality of microstructures are arranged on the surface, facing the interposer, of the light sensing layer. Wherein the part, reflected by an object, of the light signal enters the light receiving element, and is received by the light sensing layer after penetrating through the intermediate layer. Therefore, the light sensor can reduce the phenomenon of non-uniform light penetration rate so as to reduce the production cost of the light sensor.

Description

Technical Field

[0001] The present invention relates to a light sensor, and in particular to a light sensor comprising a light emitting element and a light receiving element. Background Art

[0002] Light sensors realized by light sensing technology are widely used in many applications. For example, proximity sensors can be used to detect the distance between an object and an electronic device (e.g., a smart phone, a wireless Bluetooth headset, etc.). Thus, when the proximity sensor is close to the user's face, the mobile phone can correspondingly turn off the display screen and the touch function to prevent the user's face from accidentally touching the display screen during a call and interrupting the conversation; or, when the proximity sensor is far away from the user's ear, the headset can also correspondingly turn off the audio playback function to save energy.

[0003] Please refer to Figure 1 As shown, generally speaking, the existing optical sensor 9 used as a distance sensor is usually equipped with a light emitting diode or a laser diode as a light emitting element 91 to emit light, and then when the light is directed to the approaching object A, the reflected light intensity is sensed by the light receiving element 92 to determine the distance to the object. It should be noted that when the light reflected by the object A enters the light receiving element 92 at different incident angles, a phenomenon of transmittance ripple will occur.

[0004] For details, please refer to Figure 2 As shown in FIG. 1 , it is the transmittance of a sample of the light sensor 9 when sensing light with different incident angles, that is, the efficiency of light entering the light sensor 9 from the air and being sensed by a light sensing layer 921. If the incident angles of the two light beams L1 and L2 are θ1 and θ2, respectively, which are 10° and 20°, it can be seen from the figure that there is a very large difference in the transmittance between the two, which is the transmittance fluctuation as described above.

[0005] Although it is possible to try to deal with the uneven transmittance of light at different incident angles through circuit compensation, the practical difficulty is that each light sensor 9 may exhibit a different transmittance distribution due to process variation during mass production. For example, please refer to Figure 3 As shown, for the two samples S1 and S2 of the optical sensor 9, two completely different transmittance distributions can be formed. The transmittance of one sample S1 is at the peak of the jump when the incident angle is 0°; however, the transmittance of the other sample S2 is at the trough of the jump when the incident angle is also 0°. This will lead to a very large difference in optical performance between individual mass-produced products, which will lead to problems such as difficulty in product calibration or poor yield, and seriously increase the production cost of optical sensors.

[0006] In view of this, there is indeed a need to improve the existing optical sensors so that electronic devices can achieve more accurate or diverse control functions at a lower cost. Summary of the invention

[0007] One of the purposes of the present invention is to provide a light sensor and a control method thereof, which changes the direction of light when passing through each layer of the light-emitting element by setting a plurality of microstructures in the light-sensing layer of the light-receiving element to avoid constructive interference or destructive interference. In this way, when the light-emitting element emits light and the light reflected by the object enters the light-receiving element at different incident angles, the phenomenon of light transmittance fluctuation can be reduced, thereby effectively limiting the optical performance differences between individual light sensor products, solving the problem of difficult product calibration or poor yield, and significantly reducing the production cost of the light sensor.

[0008] The present invention relates to a light sensor, which includes a light emitting element and a light receiving element. The light emitting element is used to emit a light signal. The light receiving element includes a light sensing layer and an intermediate layer, and the intermediate layer is arranged on the light sensing layer along a vertical direction. The light sensing layer is provided with a plurality of microstructures on the surface facing the intermediate layer. The part of the light signal reflected by an object enters the light receiving element, and is received by the light sensing layer after passing through the intermediate layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 :It is a structural schematic diagram of an existing optical sensor; Figure 2 : It is a schematic diagram of the transmittance of a sample of the light sensor when sensing light with different incident angles; Figure 3 :It is a schematic diagram of the transmittance distribution of two samples of existing optical sensors; Figure 4 : It is a schematic diagram of the structure of the optical sensor of the first embodiment of the present invention; Figure 5A : It is an enlarged schematic diagram of the rectangular cross-section microstructure of the optical sensor of the first embodiment of the present invention; Figure 5B : It is an enlarged schematic diagram of the arc-shaped cross-section microstructure of the optical sensor of the first embodiment of the present invention; Figure 5C : It is an enlarged schematic diagram of the triangular cross-section microstructure of the optical sensor of the first embodiment of the present invention; Figure 5D : It is an enlarged schematic diagram of the trapezoidal cross-section microstructure of the optical sensor of the first embodiment of the present invention; Figure 5E : It is an enlarged schematic diagram of a light sensor having more than two microstructures according to the first embodiment of the present invention; Figure 6: It is a schematic diagram of the transmittance distribution of two samples of the optical sensor of the first embodiment; Figure 7 : It is a schematic diagram of the structure of the light sensor according to the second embodiment of the present invention; Figure 8 : It is a schematic diagram of the structure of the light sensor according to the third embodiment of the present invention.

Figure number comparison

[0010] In order to further understand and appreciate the structural features and effects of the present invention, a preferred embodiment and detailed description are provided as follows:

[0011] To assist in explaining the improvements made by the present invention, please continue to refer to Figure 1According to the inventor's research, the non-uniform transmittance of light entering the light receiving element 92 at different incident angles is mainly due to the difference in refractive index between the light sensing layer 921 of the light receiving element 92 and an adjacent intermediate layer 922; in addition, the required thickness of the intermediate layer 922 in practical applications is also large (usually >6um), which is sufficient to meet the conditions for forming constructive interference or destructive interference, thereby causing the transmittance of light at different incident angles to fluctuate.

[0012] To resolve this issue, see Figure 4 , which is a schematic diagram of the structure of the optical sensor 1 of the first embodiment of the present invention, which includes a light emitting element 11 and a light receiving element 12. The light emitting element 11 is usually made of a light emitting diode or a laser diode, for example, it can be a solid-state light source element such as an edge emitting laser (EEL) or a vertical cavity surface emitting laser (VCSEL) for emitting a light signal.

[0013] The light receiving element 12 can be integrated on an integrated circuit chip (hereinafter referred to as chip), and the chip can also be provided with a control circuit to control the operation of the light emitting element 11 or the light receiving element 12, and to perform calculations on the signals generated by them. However, in other embodiments, an external control circuit can also be used to control and process the signals of the light emitting element 11 or the light receiving element 12. In this case, the control unit can be set in an external system (such as a mobile communication device or a wearable device, etc.). The present invention is not limited to this, so only the light receiving element 12 is shown in the figure as a part of the light receiving surface.

[0014] The light-receiving element 12 can be made of a photodiode as a part of the light-receiving surface, and includes a photosensitive layer 121 and an intermediate layer 122. The material of the photosensitive layer 121 can be silicon or silicon-germanium (SiGe), etc. The intermediate layer 122 is disposed adjacent to the photosensitive layer 121 along a vertical direction on the drawing. The intermediate layer 122 can have a thickness T greater than 6um in the vertical direction, and the material of the intermediate layer 122 can be a material with a refractive index different from that of the photosensitive layer 121. Generally speaking, the intermediate layer 122 can be an interlayer dielectric layer (ILD), and its material is usually selected from oxides or nitrides, such as silicon dioxide, silicon nitride or silicon oxynitride, etc., to provide insulation and structural support effects.

[0015] As mentioned above, due to the difference in refractive index between the photosensitive layer 121 and the intermediate layer 122 of the light receiving element 12, and the fact that the thickness of the intermediate layer 122 is required to be large in current applications (for example, about 8um), in order to avoid constructive interference or destructive interference when light passes through the photosensitive layer 121 and the intermediate layer 122, the optical sensor 1 of the first embodiment of the present invention is provided with several microstructures 121a on the surface of the photosensitive layer 121 facing the intermediate layer 122. According to the current mainstream semiconductor process for making photodiodes, these microstructures 121a can preferably be manufactured by photolithography and etching technology. However, if other processes suitable for making microstructures on the photosensitive layer 121 are available in the future, users can choose according to their needs. Please refer to Figure 5A As shown, in this embodiment, the microstructures 121a are grooves with a rectangular cross section. However, in practice, the first embodiment of the present invention is not limited thereto.

[0016] For details, please refer to Figure 5B As shown, in other implementations of the first embodiment of the present invention, the plurality of microstructures 121b disposed on the surface of the light sensing layer 121 may be grooves with arc-shaped cross sections. Figure 5C As shown, in other implementations of the first embodiment of the present invention, the plurality of microstructures 121c disposed on the surface of the light sensing layer 121 may be grooves with a triangular cross section. Figure 5D As shown, in other implementations of the first embodiment of the present invention, the plurality of microstructures 121d disposed on the surface of the light sensing layer 121 may be grooves with a trapezoidal cross section. In fact, the groove shapes listed in the above implementations are only used as examples, and other microstructure shapes that can achieve the same effect are also within the scope of protection claimed by the present invention.

[0017] On the other hand, compared to the aforementioned embodiments in which the plurality of microstructures are almost identical and repeatedly arranged grooves, please refer to Figure 5E As shown, in another embodiment of the first embodiment of the present invention, two or more microstructures 121e and 121f may be provided on the surface of the photosensitive layer 121. The two microstructures 121e and 121f may be grooves with triangular cross-sections but different sizes as shown in the figure. Of course, the two microstructures 121e and 121f may also be grooves with two different cross-section shapes.

[0018] Furthermore, the above-mentioned lithography and etching technology has its process variation, so there may be slight differences in the cross-sectional shapes of each microstructure; or the groove originally designed to be rectangular in cross section may have a cross section similar to an arc in the finished product, and the groove originally designed to be triangular in cross section may have a cross section similar to a trapezoid in the finished product, etc. As long as the optical properties measured in the end meet the requirements, they are still within the scope of the protection requested by the present invention. On the other hand, the light sensing layer 121 may have a width on a plane perpendicular to the aforementioned vertical direction, and the width is preferably greater than 20um to ensure that there is enough space for the aforementioned several microstructures 121a to 121f to be arranged.

[0019] The optical sensor 1 of the first embodiment of the present invention is provided with a plurality of microstructures 121a-121f on the surface of the optical sensing layer 121 facing the intermediate layer 122. The microstructures 121a-121f can change the direction of light passing through the intermediate layer 122 and the optical sensing layer 121 to avoid constructive interference or destructive interference. Thus, compared with the prior art in which the interface between the optical sensing layer 921 and the intermediate layer 922 is a roughly flat surface, the optical sensing layer 121 and the intermediate layer 122 of the first embodiment of the present invention have the microstructures 121a-121f, so that the optical sensor 1 can reduce the phenomenon of light transmittance fluctuation when the light emitting element 11 emits light and the light reflected by the object A enters the light receiving element 12 at different incident angles.

[0020] exist Figure 3 In the figure, the two samples S1 and S2 of the existing optical sensor 9 are actually samples in which the intermediate layer 922 is about 7.3um and about 7.9um respectively. It is noted that if the design target thickness of the intermediate layers 922 and 122 is 8um, various intermediate layer thicknesses close to 8um will inevitably be produced due to process variation during mass production, thus forming products in which the thicknesses of the intermediate layers 922 and 122 are close to about 7.3um and about 7.9um. In order to highlight the effect achieved by the optical sensor 1 of the first embodiment of the present invention, two samples S1' and S2' in which the intermediate layers 122 are about 7.3um and about 7.9um respectively (and several microstructures are arranged on the surface of the light sensing layer 121 facing the intermediate layer 122) are also taken for optical simulation measurement, and the result is Figure 6 First, it is noted that the transmittance of the sample S1' with the intermediate layer 122 of about 7.3um is at the trough of the jump when the incident angle is 0°; however, the transmittance of the sample S2' with the intermediate layer 122 of about 7.9um is at the peak of the jump when the incident angle is also 0°, which is similar to Figure 3 Therefore, the optical sensor 1 of the first embodiment of the present invention can indeed change the distribution of light transmittance at different incident angles by disposing a plurality of microstructures on the surface of the optical sensing layer 121 facing the intermediate layer 122 .

[0021] More importantly, compared to Figure 3 In terms of the simulation measurement results of the prior art, the difference in transmittance between the two samples S1' and S2' has been greatly reduced. In other words, the optical sensor 1 of the first embodiment of the present invention can effectively limit the optical performance differences between individual optical sensor products by setting a plurality of microstructures on the surface of the optical sensing layer 121 facing the intermediate layer 122, thereby solving the problem of difficult product calibration or poor yield, and significantly reducing the production cost of the optical sensor.

[0022] It should be noted that the optical sensor 1 of the first embodiment of the present invention avoids the uneven transmittance of light at different incident angles by avoiding the conditions for the light sensing layer 121 and the intermediate layer 122 of the light receiving element 12 to form constructive interference or destructive interference. To achieve this effect, the user needs to appropriately adjust the design of the several microstructures set in the light sensing layer 121 according to the optical environment used. Among them, the conditions for the interference of light of different wavelengths due to the influence of the refractive index of the medium will be different. Therefore, in order to facilitate the simulation measurement and complete the design of the several microstructures of the light sensing layer 121, the optical sensor 1 of the first embodiment of the present invention is particularly suitable for the case where the light emitting element 11 is a single-wavelength light emitter, which refers to a light emitter with the highest intensity at a specific wavelength (or a specific wavelength range). For example, the operating wavelength range of the distance sensor used in mobile phones usually falls between 750 and 1600 nm, and the light emitting element 11 can be selected as a single-wavelength light emitting diode or laser diode with the highest intensity at a wavelength of 940 nm (or a wavelength range of 850 to 1000 nm). In this way, the user only needs to design several microstructures of the light sensing layer 121 for light with a wavelength of 940 nm (or a wavelength range of 850-1000 nm).

[0023] It is worth noting that Figure 4 As shown, the light receiving element 12 may be provided with other layer structures in addition to the light sensing layer 121 and the intermediate layer 122. For example, the light receiving element 12 may also include a covering layer 123 above the intermediate layer 122 in the vertical direction. The covering layer 123 may be a passivation layer and may be made of silicon nitride or silicon oxide to provide protection and blocking effects. In this embodiment, if the intermediate layer 122 is silicon dioxide and the covering layer 123 is silicon nitride, the difference in the refractive index of different materials may cause the light receiving element 12 to need more microstructures of the light sensing layer 121 to avoid the formation of constructive interference or destructive interference conditions.

[0024] Alternatively, the cover layer 123 may also include a filter structure, which can generally be a dielectric film, a metal film, a photoresist, or a multilayer coating formed by any combination of the above three, and its main purpose is to suppress noise outside the non-working wavelength range. For example, when the working wavelength of the light-emitting element 11 is 940nm (or the working wavelength range is 850-1000nm), the optical signal that is too different from 940nm can be regarded as noise and can be filtered out using a filter structure. Similarly, when the intermediate layer 122 is silicon dioxide and the cover layer 123 is a single-layer multilayer coating, the difference in the refractive index of different materials is superimposed, which may cause the light-receiving element 12 to require several microstructures of the light-sensing layer 121 to avoid the formation of constructive interference or destructive interference conditions.

[0025] In addition, generally speaking, the light receiving element 12 is also covered by a packaging layer 124, which can seal the light receiving element 12 and is generally made of transparent film plastic. Similarly, due to the superposition of the difference in refractive index of different materials, the light receiving element 12 may require more microstructures of the light sensing layer 121 to avoid the formation of constructive interference or destructive interference conditions.

[0026] In addition to the aforementioned light-sensing layer 121, the intermediate layer 122, the covering layer 123, and the packaging layer 124, the light-receiving element 12 may also have other layer structures that cannot be listed one by one. For example, the light-receiving element 12 may also include a lens to change the incident angle distribution of the light or the field of view (FOV) of the light-receiving element 12. In addition, there may be an ink layer, a light-guiding layer, etc. above the light-receiving element 12, all of which may form a superposition of the refractive index differences of different materials, thereby causing the light-receiving element 12 to rely more on the several microstructures of the light-sensing layer 121 to avoid the formation of constructive interference or destructive interference conditions.

[0027] Please refer to Figure 7 , which is a schematic diagram of the structure of the optical sensor 1 of the second embodiment of the present invention. Although in the first embodiment, the light emitting element 11 and the light receiving element 12 of the optical sensor 1 can be respectively arranged in the external system. However, in practice, as shown in the second embodiment, the difference from the first embodiment is that the optical sensor 1 is usually integrated and packaged into one element, wherein the light emitting element 11 and the light receiving element 12 can be arranged together on a substrate 13, and a packaging layer 14 can seal the light emitting element 11 and the light receiving element 12, and the packaging layer 14 is generally made of transparent film plastic material.

[0028] Please refer to Figure 8, which is a schematic diagram of the structure of the light sensor 1 of the third embodiment of the present invention. Although in the first embodiment, it has been described that in order to facilitate the design of several microstructures of the light sensing layer 121, the light emitting element 11 preferably uses a single-wavelength light emitter with the highest intensity at a specific wavelength (or a specific wavelength range), but in practice it is difficult to obtain or manufacture a single-wavelength light emitter whose optical properties fully meet the requirements. Therefore, as shown in the third embodiment, the difference from the first embodiment is that an optical filter 111 can be set above the light emitting element 11 in the vertical direction, and the optical filter 111 covers the light emitting area of ​​the light emitting element 11. The optical filter 111 can filter the light signal emitted by the light emitting element 11 so that it has the highest intensity at a specific wavelength (or a specific wavelength range).

[0029] Note that when the cover layer 123 includes a filter structure, the filter structure can preferably be designed in conjunction with the optical filter 111, so that the light emitting element 11 can emit light of a specific wavelength (or a specific wavelength range) as much as possible, and only allow the light of the specific wavelength (or a specific wavelength range) to enter the light receiving element 12. In this way, it can be ensured that when the light receiving element 12 senses the light reflected by the object A, the uneven light transmittance at different incident angles is avoided to the greatest extent.

[0030] In summary, the optical sensor embodiments of the present invention change the direction of light passing through the various layers of the light-emitting element by setting a number of microstructures on the light-sensing layer of the light-receiving element to avoid constructive interference or destructive interference. In this way, when the light-emitting element emits light and the light reflected by the object enters the light-receiving element at different incident angles, the phenomenon of light transmittance fluctuation can be reduced, thereby effectively limiting the optical performance differences between individual optical sensor products, solving the problem of difficult product calibration or poor yield, and significantly reducing the production cost of optical sensors.

[0031] The order of execution of each step in the above embodiment does not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present application.

[0032] The above is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. All equivalent changes and modifications to the shape, structure, characteristics and spirit described in the claims of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A light sensor, characterized in that: It contains: a light emitting element for emitting a light signal; and A light collecting element comprises a light sensing layer and an intermediate layer, wherein the intermediate layer is arranged on the light sensing layer along a vertical direction, and a plurality of microstructures are arranged on a surface of the light sensing layer facing the intermediate layer; The part of the light signal reflected by an object enters the light receiving element, passes through the intermediate layer and is received by the light sensing layer.

2. The optical sensor according to claim 1, wherein in, The material of the intermediate layer and the material of the light sensing layer have different refractive indices.

3. The optical sensor according to claim 1, wherein: in, A thickness of the intermediary layer in the vertical direction is greater than 6 um.

4. The optical sensor according to claim 1, wherein in, The light emitting element is a light emitter whose light intensity has the highest intensity in a specific wavelength range.

5. The optical sensor according to claim 4, wherein: in, An optical filter is arranged above the light emitting element in the vertical direction. The optical filter filters the light signal emitted by the light emitting element so that the light signal has the highest intensity in a certain specific wavelength range.

6. The optical sensor according to claim 1, wherein: in, The light collecting element further includes a covering layer on the intermediate layer in the vertical direction.

7. The optical sensor according to claim 6, wherein: in, The cover layer is a passivation layer, and the material of the intermediate layer and the material of the passivation layer have different refractive indices.

8. The optical sensor according to claim 6, wherein: in, The cover layer contains the filtering structure.

9. The optical sensor according to claim 1, wherein: in, The light receiving element is covered by a packaging layer made of transparent film plastic material.

10. The optical sensor according to claim 1, wherein in, The device further comprises a substrate, on which the light emitting element and the light receiving element are disposed together.

11. The optical sensor according to claim 10, wherein in, The light emitting element and the light receiving element are covered by a packaging layer made of transparent film plastic material.

12. The optical sensor according to claim 1, wherein in, The plurality of microstructures are grooves with rectangular, arc-shaped, triangular or trapezoidal cross sections.

13. The optical sensor according to claim 1, wherein in, The plurality of microstructures include grooves with two different cross-sectional sizes.

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