Oozing phenomena suppression in an optical component

Abstract

The present disclosure relates to a method (300) of forming an optical component (350), the method (300) including: providing (310) a plurality of optical elements (302) on a first surface (304a) of a substrate (306); for each optical element (302) of the plurality of optical elements (302): providing (320) a respective solid adhesive element (308) on a second surface (304b) of the substrate (306) in correspondence of the respective optical element (302), wherein the second surface (304b) is opposite to the first surface (304a), wherein the adhesive element (308) corresponding to the optical element (302) has a lateral extension (318) in a plane parallel to the surface (304a, 304b) of the substrate (306) less than a lateral extension (316) of the optical element (302) in the plane; and carrying out a singulation process (330) to separate the plurality of optical elements (302) into individual optical components (350).

Description

OOZING PHENOMENA SUPPRESSION IN AN OPTICAL COMPONENTTechnical Field

[0001] The present disclosure relates generally to an optical component including an ooze-free adhesive element, and to methods thereof (e.g., a method of forming an optical component without causing oozing of an adhesive element).Background

[0002] In general, optical components to manipulate light are a key part in various types of optoelectronic devices such as sensors, cameras, light sources, light projectors, and the like. For example, optical modules including a stack of lenses allow shaping a light beam according to a desired application, e.g. to focus the light beam towards a particular direction, to collimate a light beam for uniform light emission, etc. Optical components for use in small footprint optoelectronic devices (e.g., light emitters, light sensors, etc.), are generally fabricated in parallel by forming hundreds or thousands of lens elements on a substrate, and then carrying out a singulation process to separate the optical components into individual units. However, at the singulation stage a so-called “oozing phenomenon” may occur, causing an adhesive layer present in the optical component to undergo an elastic deformation and leaving an excess of adhesive to protrude from the borders of the substrate. There is thus a general need for improved strategies for the fabrication of optical components for use in small footprint optoelectronic devices, e.g. to mitigate or suppress the oozing phenomenon.Brief Description of the Drawings

[0003] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various aspects of the invention are described with reference to the following drawings, in which:FIG.1A shows an optoelectronic device in a schematic representation, according to various aspects;FIG. IB shows an imaging device in a schematic representation, according to various aspects;FIG.2A to FIG.2D show a fabrication of an optical component in which oozing of an adhesive element occurs, according to various aspects;FIG.3A shows a schematic flow diagram of a method of forming an optical component, according to various aspects;FIG.3B to FIG.3D show an illustrative representation of steps of the method of forming an optical component, according to various aspects;FIG.3E shows an optical component fabricated according to the method of FIG.3A to FIG.3D in a schematic representation, according to various aspects; andFIG.4A to FIG.4C show an optical component including an ooze-free adhesive element in a schematic representation, according to various aspects.Description

[0004] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and aspects in which the invention may be practiced. These aspects are described in sufficient detail to enable those skilled in the art to practice the invention. Other aspects may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the invention. The various aspects are not necessarily mutually exclusive, as some aspects may be combined with one or more other aspects to form new aspects. Various aspects are described in connection with methods and various aspects are described in connection with devices (e.g., an optical component, an optoelectronic device). However, it is understood that aspects described in connection with methods may similarly apply to the devices, and vice versa.

[0005] Optoelectronics is at the intersection between optics and electronics, and deals with devices capable of emitting, detecting, and / or otherwise controlling light. Optoelectronic devices are used in a wide range of application areas. For example, in the current market, there is a growing trend towards three-dimensional (3D) sensing, for example for face authentication, movement-tracking, eye-tracking, and the like. For this type of application, optoelectronic illuminators may flood the targets with light, or optoelectronic projectors may project light dots onto the targets, and the light impinging onto the targets is imaged and measured via an optoelectronic camera.

[0006] Tracking sensors for augmented reality and / or virtual reality may be camera-based visual sensors operating in the visible spectral bandwidth and / or near infrared (NIR) spectral bandwidth, in view of the human sense of sight. An imaging device for such applications may usually include a compact camera module (CCM) for sensing light and generating corresponding sensing data. A camera-based tracking sensor may usually include a CMOS image sensor (CIS), where CMOS stands for Complementary Metal-Oxide Semiconductor. Acamera-based tracking sensor may further include an optical lens module to collect light from the field of view of the sensor and direct the collected light to the image sensor (e.g., the CMOS image sensor). With the advancements of new generations of imaging devices, there is a constant demand for a miniaturization of their mechanical, optical, and electrical components.

[0007] In the context of small-footprint optical systems, wafer-level optics is a technique for fabricating miniaturized optical components, such as optical components including wafer-level lenses. The general aspects related to wafer-level optics and corresponding fabrication techniques are well known in the art. A brief description is provided herein to introduce aspects relevant for the present disclosure.

[0008] Wafer-level optics may be based on processes typical of semiconductor manufacturing, such as thin film deposition, lithography, etching, molding, imprinting, and the like. For example, in wafer-level optics, lens elements may be fabricated using molds, thus enabling mass production. As an abridged overview, wafer-level optics may include imprinting to fabricate optical components at the wafer-level, and then a layer-by-layer stacking of the individual optical components to assemble the final product. The resulting optical module may finally be coupled, e.g. bonded, with an optoelectronic device (e.g., an image sensor, a light emitter) at the wafer-level. Wafer-level optics may thus allow producing optical modules with a reduced footprint compared to other fabrication techniques.

[0009] Wafer-level optics may thus refer to the mass production of micro-optical components on a wafer level. Wafer-level optics offers the capabilities to produce small and precise optical components, including lenses. In general, WLO lenses may be particularly useful for applications in which space constraints play an important role, such as in smartphones, wearables, and other portable electronic devices. WLO lenses may be manufactured with a very small form factor, making them ideal for these types of applications. Furthermore, the scalability of WLO lens fabrication allows for high volume production, which can help reduce the cost per unit and increase the overall efficiency.

[0010] In general, the placement of an optical component in an optoelectronic device (e.g., on a sensor) may be carried out using various possible methods. A commonly used approach is based on the use of an optically clear adhesive (OCA) for bonding the optical component to a housing of the optoelectronic device. As generally known in the art, an optically clear adhesive is a highly transparent adhesive that allows a robust bonding on a wide range of substrates. Various possible configurations exist for an optically clear adhesive, e.g. as liquid, resin, epoxy, and the like. In a possible configuration an optically clear adhesive may be a solid and softadhesive placed between the optical component and the optoelectronic component, with a specific refractive index to avoid transmission issue.

[0011] In wafer-level optics technology several optical components are produced together in the same wafer / foil, providing a cost-efficient process. In this type of fabrication, the solid OCA may be laminated below the substrate on which the lens elements are formed, and later a process of singulation may be carried out to separate every single unit. During the singulation process (e.g., performed using a die cutting tool) the OCA material is singulated together with the optical component. However, the elastic properties of the OCA do not allow a straight cut, and the elastic deformation of the OCA results in an excess material outside of the substrate of the optical component, thus causing a cosmetic defect and contamination on the tool. This phenomenon may be commonly referred to as “oozing”. Illustratively, after the singulation the layer of OCA protrudes from the borders of the optical component, thus resulting in an inconvenient excess of material that may complicate the subsequent use of the optical component, e.g. its integration in an optoelectronic device.

[0012] The present disclosure may be based on the realization that a pre-processing of the adhesive element before coupling with the substrate of the corresponding optical component allows to precisely define the extension of the adhesive element, thus effectively suppressing the oozing phenomenon. Illustratively, the present disclosure may be based on the realization that the adhesive element may be structured prior to coupling with the substrate on which the optical element (e.g., lens element) is formed / disposed, thus defining a lateral extension for the adhesive element that prevents the contact with the cutting tool and avoids the elastic deformation at the singulation stage.

[0013] According to the fabrication method proposed herein, the adhesive element is structured to have a lateral extension (e.g., a diameter) less than the optical element of the corresponding optical component. This ensures that during the singulation process the adhesive element is not affected by the singulation tool, and does not suffer any elastic deformation. Illustratively, the reduced lateral extension ensures that the singulation tool contacts the substrate far away from the edges of the adhesive element, thus ensuring a straight cut of the substrate without a deformation of the adhesive.

[0014] According to various aspects a method of forming an optical component may include: providing a plurality of optical elements on a first (main) surface of a substrate; for each optical element of the plurality of optical elements: forming a respective solid adhesive element, structuring the solid adhesive element to define for the solid adhesive element a lateral extension in a plane parallel to the first surface of the substrate less than a lateral extension ofthe optical element in the plane, disposing the (structured) solid adhesive element on a second (main) surface of the substrate in correspondence of the respective optical element (e.g., aligned with the optical element), wherein the second surface is opposite to the first surface; and carrying out a singulation process to separate the plurality of optical elements from one another to provide individual optical components.

[0015] In the present disclosure the term “optical element” is used to describe an element that is part of an optical component and that is configured to implement a predefined optical function. An optical element may thus be configured to manipulate light passing through the optical element according to the corresponding optical function for which the optical element is designed. An optical element may illustratively be an optical surface configured (e.g., shaped) to define a predefined manipulation of the light. For example an optical element (or surface) may be a lens element configured to implement a predefined lens function. For example, the predefined optical function (e.g., the predefined lens function) may include focusing light, diffracting light, collimating light, diverging light, projecting a light pattern, etc. The term “optical component” may describe a component including an optical element, and further including additional elements such as a substrate, an adhesive, and the like. Aspects discussed in relation to an optical component may apply in a corresponding manner to the respective optical element, and vice versa.

[0016] According to various aspects an optical component may include: a substrate configured to be transparent for light in an operating wavelength range of the optical component; an optical element disposed on a first (main) surface of the substrate, wherein the optical element is configured to provide a predefined optical function; and a solid adhesive element disposed on a second (main) surface of the substrate in correspondence of the optical element (e.g., aligned with the optical element), wherein the second surface is opposite to the first surface, wherein the solid adhesive element has a lateral extension in a plane parallel to the first surface of the substrate less than a lateral extension of the optical element in the plane.

[0017] The present disclosure may thus be related to a novel approach for forming optical components that allows using solid adhesive elements without incurring in the undesired oozing phenomenon. A solid adhesive element, such as an optically clear adhesive, may simplify the processing compared to liquid adhesives, thus contributing to an overall more straightforward fabrication process. In particular, the proposed fabrication strategy may be relevant for geometries of the optical component that do not allow the use of a blade for the singulation step. Illustratively, if the resulting optical component has a profile with straight edges, e.g. a square profile or a rectangular profile, the singulation may be carried out using a dicing bladethat may be suitable to define straight edges also for the adhesive element. However, for more complex profiles, e.g. including a rounded edge (e.g., a circular profile), other singulation tools are used, e.g. a punching tool, which could cause the oozing phenomenon mentioned above.

[0018] Thus, in the present disclosure particular reference may be made to an optical component having a profile with at least one edge that is not straight, e.g. an optical component having a circular profile. It is however understood that the proposed approach may also be applied in principle to any suitable profile of an optical component, e.g. a profile consisting of straight edges, a profile with rounded edges, etc. For example, the profile of an optical component may correspond to the profile of the substrate of the optical component on which the optical element is formed or disposed.

[0019] Although not limited thereto, the proposed approach may be of particular relevance in the context of wafer-level optics, and may overcome the limitations mentioned above. In a preferred configuration, the fabrication of the optical component may thus include wafer-level optics techniques, e.g. the optical component and optical element(s) may be fabricated via wafer-level optics manufacturing. As mentioned above, wafer-level optics techniques allow fabricating optical components with a reduced footprint, which is of particular relevance in nowadays devices (e.g., sensors for AR / VR, smartphones, tablets, etc.). It is however understood that, in principle, the aspects described herein may also apply in a corresponding manner to an optical component or optical element(s) fabricated via other types of techniques known in the art.

[0020] In the context of the present disclosure particular reference may be made to applications of an optical component configured as described herein for light detection purposes. Illustratively, particular reference may be made to a use of the optical component for receiving light and focusing light onto an image sensor (e.g., a CMOS sensor). This application may be a relevant use case for the proposed optical component, e.g. in the context of AR- or VR- applications. It is however understood that in principle an optical component configured as described herein may also be used at the emitter-side of an optical system, e.g. to manipulate the emitted light.

[0021] An optoelectronic device including the optical component may be integrated in a host device that exploits the imaging device to implement one or more functionalities (e.g., telecommunications, distance measurements, object tracking, and the like). Exemplary host devices for the optoelectronic device may include a mobile communication device (e.g., a smartphone, a tablet, a laptop), a vehicle (e.g., a car), an automated machine (e.g., a drone, arobot), and the like. An optoelectronic device including the optical component may be for use in the consumer market, robotics market, automotive market, and / or industrial market.

[0022] FIG.1A shows an optoelectronic device 100 in a schematic representation, according to various aspects. The optoelectronic device 100 may be an exemplary configuration of a device including an optical component configured as proposed herein, which will be described in detail in relation to FIG.3 A to FIG.4C. In general, the optoelectronic device 100 may include an active optoelectronic component 102 configured for emitting or detecting light, an optical component 104 to direct light towards a field of illumination or to direct light towards a light-detecting optoelectronic component, and a processing circuit 106 to control an operation of the optoelectronic device 100. It is understood that the optoelectronic device 100 may also include more than one active optoelectronic component 102, e.g. each associated with a corresponding optical component 104. For the sake of brevity the “active” optoelectronic component 102 may also be referred simply as optoelectronic component 102. In general, the optoelectronic device 100 may have compact dimensions, e.g. a small footprint size. For example, the optoelectronic device 100 may be a chip-scale packaged light emitter, or a chip-scale packaged image sensor.

[0023] In this regard, the term “active” in relation to the optoelectronic component 102 may be used to indicate that the optoelectronic component 102 may implement an active function, e.g. may actively emit light upon receiving a corresponding signal (e.g., a driving current) or may actively detect light by generating a corresponding detection signal (e.g., a photo current). The term “active” may thus be used to distinguish the optoelectronic component 102 from other types of components that operate in a passive manner. The geometry (e.g., the shape and lateral dimensions) of the optoelectronic component 102 may be adapted according to the system requirements, e.g. according to an overall dimension of the optoelectronic device 100, according to fabrication constraints, etc. The optoelectronic component 102 may thus have any suitable shape, such as a circular shape, a rectangular shape, a square shape, or even asymmetric shapes.

[0024] In general, the optical element of the optical component 104 may be optically coupled with the optoelectronic component 102 and may be configured to define a field of illumination (for light emission) or a field of view (for light detection) of the active optoelectronic component 102. Illustratively, for light emission, the optical component 104 may receive light from the optoelectronic component 102 and direct the light towards the field of illumination, e.g. causing a collimation, a focusing, a projection of a pattern, and the like, depending on the intended application. For light detection, the optical component 104 may collect light from thefield of view and direct the collected light towards the optoelectronic component 102, e.g. causing a collimation, a focusing, and the like, depending on the intended application.

[0025] In a preferred configuration, the active optoelectronic component 102 may be configured to detect light. The optoelectronic component 102 may be configured as an image sensor or light sensor, and may be configured to be sensitive for light in a predefined wavelength range. In a preferred configuration, the optoelectronic component 102 may be sensitive for light in the infrared range (e.g., in the range from about 800 nm to about 5000 nm, for example in the range from about 820 nm to about 1200 nm, for example at 940 nm or around 940 nm), which is a relevant wavelength range for tracking applications, distance measurements, etc. It is however understood that in principle the optoelectronic component 102 may be sensitive for light in other wavelength ranges, e.g. the visible range (e.g., from about 380 nm to about 800 nm) and / or ultraviolet range (e.g., from about 100 nm to about 400 nm). Illustratively, the optoelectronic component 102 may be configured to convert light energy (illustratively, photons) of light impinging onto the optoelectronic component 102 in electrical energy (e.g., in a current, illustratively a photo current).

[0026] According to various aspects, the optoelectronic component 102 may be configured according to CMOS-technology, e.g. the optoelectronic device 100 may be a CMOS image sensor. In this configuration, the optoelectronic component 102 may include a plurality of CMOS pixels, each including a photodetector that accumulates an electrical charge based on the amount of light impinging onto the photodetector. As another exemplary configuration, the optoelectronic component 102 may be configured according to Charged Coupled Device (CCD) technology, e.g. the optoelectronic device 100 may be a CCD image sensor. In this configuration, the optoelectronic component 102 may include a plurality of CCD pixels with a photoactive region and a transmission region. As other examples, the optoelectronic component 102 as image / light sensor may include at least one of a PIN photo diode, an avalanche photo diode (APD), a single-photon avalanche photo diode (SPAD), or a silicon photomultiplier (SiPM).

[0027] In other aspects, the active optoelectronic component 102 may be configured to emit light, e.g. the optoelectronic device 100 may be a light emitter or light projector. The optoelectronic component 102 may be configured as a light source, and may be configured to emit light in a predefined wavelength range. In this scenario, the optoelectronic component 102 may include a solid-state light emitting element, e.g. a semiconductor-based light emitting element. In a preferred configuration for light emission, the optoelectronic component 102 may include a VCSEL, e.g. a plurality of VCSELs. For example, the optoelectronic component 102may include a single VCSEL or an array of VCSELs (e.g., a one-dimensional array or a two-dimensional array). A VCSEL may be the preferred type of light source in view of its advantageous properties such as high electro-optical conversion efficiency, low divergence of the emitted light, and overall compact dimensions. It is however understood that the optoelectronic component 102 may include also other types of solid-state light emitting elements (e.g., as single light emitting element or plurality of light emitting elements), such as an edge-emitting laser, a Vertical-Extemal-Cavity-Surface-Emitting Laser (VECSEL), a light emitting diode (LED), a Micro-LED, a superluminescent LED, and the like. In various aspects, the optoelectronic component 102 may include a plurality of emitter pixels. For example, the plurality of emitter pixels may be or may include a plurality of laser diodes (e.g., VCSELs).

[0028] The optoelectronic component 102 as light source may be configured to emit light having a predefined wavelength, for example in the visible range (e.g., from about 380 nm to about 700 nm), infrared and / or near infrared range (e.g., in the range from about 700 nm to about 5000 nm, for example in the range from about 860 nm to about 1600 nm, or for example at 905 nm or 1550 nm), or ultraviolet range (e.g., from about 100 nm to about 400 nm). A preferred configuration may include the optoelectronic component 102 being configured to emit light in the infrared range, e.g. at 940 nm, which is the relevant range for widespread applications such as face recognition, distance measurements, and the like.

[0029] The processing circuit 106 may be configured to process information to / from the optoelectronic component 102. For example, for light detection, the processing circuit 106 may be configured to receive a detection signal from the optoelectronic component 102 (e.g., a current) and may be configured to generate a digital signal representative of the detection signal. The processing circuit 106 may be further configured to deliver the digital signal as output for further processing, e.g. by an external processing circuit (see also FIG. IB). As another example, for light emission, the processing circuit 106 may be configured to drive the optoelectronic component 102 to emit light. In this scenario, the processing circuit 106 may be configured to generate a driving signal (e.g., a driving current) and deliver the driving signal to the optoelectronic component 102 for causing or triggering a corresponding emission of light.

[0030] According to various aspects, the optoelectronic device 100 may further include a substrate 108, and the optoelectronic component 102 and processing circuit 106 may be integrated onto the substrate 108. For example, the substrate 108 may be a printed circuit board. The optoelectronic device 100 may further include a housing 110. The housing 110 may enclose the optical component 104 and the optoelectronic component 102. The housing 110 may provide mechanical support to the optical component 104, e.g. the housing 110 may be preparedfor placement of the optical component 104 (e.g., the housing may include a recess or a slot to accommodate the optical component 104). As examples, the housing 110 may be a plastic spacer, a ceramic substrate, an organic substrate, or a leadframe. The housing 110 may also be referred to as package element.

[0031] It is understood that the representation of the optoelectronic device 100 in FIG.1 A may be simplified for the purpose of illustration, and that the optoelectronic device 100 may include additional components with respect to those shown.

[0032] FIG. IB shows an imaging device 120 including a (first) optoelectronic device 100a configured to emit light 122 and a (second) optoelectronic device 100b configured to detect light. The (first) optoelectronic device 100a may be configured as the optoelectronic device 100 for light emission, and the (second) optoelectronic device 100b may be configured as the optoelectronic device 100 for light detection. The imaging device 120 may further include a processing circuit 126 configured to control an operation of the device 120, e.g. the processing circuit 126 may be configured to control a light emission by the first optoelectronic device 100a and may be configured to process data related to light detection by the second optoelectronic device 100b. The imaging device 120 may also be referred to herein as light-based sensing device.

[0033] The imaging device 120 may be an exemplary device that includes one or more optoelectronic devices 100a, 100b for light emission and / or light detection. It is understood, that the imaging device 120 provides an exemplary and simplified configuration of a possible application of an optoelectronic device including an optical component as described herein. In general, the imaging device 120 may be configured for any desired application. In an exemplary configuration, which may represent a relevant use case for an optical component as described herein, the imaging device 120 may be configured as a three-dimensional sensor, illustratively as a depth sensor. As other examples, the imaging device 120 may be configured as a time-of- flight sensor, a proximity sensor, a stereo vision sensor, and the like.

[0034] The imaging device 120 may be configured to carry out light-based sensing (or light-based detection) in a field of view 130. In this regard, the processing circuit 126 may be configured to instruct the light-emitting optoelectronic device 100a to emit light, e.g. the processing circuit may trigger or initiate a light emission by the first optoelectronic device 100a. The first optoelectronic device 100a may emit light 122 towards a field of illumination of the first optoelectronic device 100a. The field of illumination may at least partially overlap with the field of view 130 of the device 120, e.g. with the field of view of the light-detecting optoelectronic device 100b. In some aspects, the field of illumination of the first optoelectronicdevice 100a may correspond to the field of view of the second optoelectronic device 100b (illustratively, the field of illumination may coincide with the field of view 130).

[0035] The first optoelectronic device 100a may be configured or controlled to emit light according to any suitable emission scheme, depending on the type of sensing / detection to be implemented. As an example, the first optoelectronic device 100a may be configured to emit light according to a predefined light pattern, e.g. a grid of light dots or a grid of lines. This configuration may be provided, for example, for face-recognition applications, in which the distortion of the emitted pattern is associated to the profile of an object (e.g., a person) in the field of view 130 of the device 120. As another example, the first optoelectronic device 100a may be configured to emit a light pulse, or a sequence of light pulses. This configuration may be provided, for example, for time-of-flight measurements, in which the round-trip time of the emitted light pulses is calculated to map the presence of objects in the field of view 130, and their properties such as distance from the device 120, speed, direction of motion, and the like.

[0036] The second optoelectronic device 100b may be configured to detect light 124. Illustratively, the second optoelectronic device 100b may be configured to receive light from the field of view 130, e.g. a back-reflection of the emitted light 122, and deliver a signal representative of the received light. As an example, the second optoelectronic device 100b may deliver a signal representative of a (distorted) pattern of the detected light 124. In this scenario, the processing circuit 126 may be configured to determine properties of the object that back- reflected the emitted pattern by analyzing the distortion (e.g., a phase variation between light dots in the emitted pattern and in the detected pattern). For example, the processing circuit 126 may be configured to reconstruct a shape of the object (e.g., a face) based on the distorted pattern. As another example, the second optoelectronic device 100b may deliver a signal representative of an arrival time of a light pulse at the second optoelectronic device 100b. In this scenario, the processing circuit 126 may be configured to determine a time-of-flight of the light by using the emission time of the emitted light 122 and the arrival time of the reflected light 124, as known in the art. As another example, the processing circuit 126 may be configured to carry out a tracking of an element in the field of view 130. Illustratively, the processor 126 may be configured to follow an evolution of a spatial position of the element over time, e.g. to associate two-dimensional coordinates or three-dimensional coordinates corresponding to a position of the element to a respective time point. The tracked element may be any suitable feature or object of interest, such as the hand of a user, the eyes of a user, a vehicle, an animal, etc.

[0037] According to various aspects, the processing circuit 126 may include or may be coupled with a memory (not shown). For example, the memory may be part of the imaging device 120. As another example, the memory may be external to the imaging device 120 and the processing circuit 126 may be communicatively coupled with the memory (e.g., with the cloud). The memory may store software and coded instructions for the processing circuit 126.

[0038] It is understood that the representation in FIG. IB may be simplified for the purpose of illustration, and that the imaging device 120 may include additional components with respect to those show. For example, the device 120 may include one or more amplifiers to enhance the light emission and / or light detection, one or more filters to select a wavelength bandwidth to reduce the impact of ambient light, transmitter optics, receiver optics, scanning elements (e.g., a MEMS mirror) to scan the field of illumination, analog-to-digital converters, and the like.

[0039] In general, a common strategy for coupling an optical component to an optoelectronic device, e.g. for securing the optical component to the housing of the device, involves the use of adhesives. In particular, solid adhesive elements, such as a solid layer of optically clear adhesive, facilitate the delivery of optical components that may then be simply integrated into an optoelectronic device at the customer side. Illustratively, the optical component may be fabricated including a solid adhesive element that allows the customer to simply install the optical component for the desired application. Compared to liquid-based adhesives, the use of solid adhesive elements reduces the processing at the customer side, e.g. eliminating dispensing steps, curing steps, and the like. A solid adhesive, such as a solid layer of OCA, facilitates a “pick and place” approach, saving time and costs for the customer.

[0040] However, as shown in FIG.2A to FIG.2D, the use of solid adhesive elements presents challenges at the fabrication side, due to the so-called oozing phenomenon. Considering a method 200 for parallel fabrication of optical components, optical elements 202 (e.g., lens elements) may be formed on a substrate 204 (e.g., a plastic foil), as shown in step 210 in FIG.2A. After forming the optical elements 202 a layer of adhesive 206 may be provided (e.g., laminated, for example via a rolling process) on the bottom of the substrate 204 to allow the subsequent bonding of the resulting optical component, as shown in step 220 in FIG.2B. For example, the adhesive may be an OCA layer. After providing the adhesive 206 the method 200 may include, in step 230 in FIG.2C, a singulation step in which a die cutting tool 208, e.g. a punching tool, is used to cut through the substrate 204 and separate the individual optical components. The die cut tool cuts the substrate, optical element 202, and the adhesive 206 according with the desired dimension.

[0041] FIG.2D shows a resulting optical component 250 in a side view 250a and a top view 250b. As visible, the cutting process causes an elastic deformation of the adhesive layer, which results in a leftover of excess material around the edges of the substrate 204 of the optical component 250. Illustratively, a oozing portion 212 remains due to the elasticity of the adhesive layer 206 that prevents a straight cut through the adhesive layer 206. The die cutting tool 208 pulls part of the adhesive layer 206 that is thus not cut but remains and protrudes around the perimeter of the optical component 250. After the separation from the tool 208, the single optical component 250 presents a protrusion of adhesive 206 on the outer perimeter. The protrusion is also visible from the top. Such behavior is undesired because the oozing portion results in cosmetic defects, could potentially contaminate the processing tools, and could complicate the bonding of the optical component 250 with an optoelectronic device (e.g., in case of very limited tolerances for the placement of the optical component 250).

[0042] The present disclosure is related to an adapted fabrication method for providing an optical component having a solid adhesive element that suppresses the oozing phenomenon, thus resulting in a “clean cut” profile for the adhesive element, without any excess material around the perimeter of the optical component. The proposed method may thus eliminate the risk of contamination of the processing tools, may provide an optical component without cosmetic defects, and may facilitate the subsequent integration of the optical component into an optoelectronic device.

[0043] The adapted process flow discussed in the present disclosure allows a larger tolerance control, while suppressing a critical cosmetic issue. Furthermore, the proposed approach may provide a process improvement by allowing more freedom on the design tool. Overall, the optical performances may be improved by facilitating the coupling of the resulting optical components for the end application.

[0044] FIG.3A shows a schematic flow diagram of a method 300 of forming an optical component, according to various aspects. The method 300 is adapted to suppress the oozing phenomenon discussed in relation to FIG.2A to FIG.2D. To assist the explanation of the method 300 reference will be made to FIG.3B to FIG.3D, which provide an illustrative representation of the various steps of the method 300. The method 300 will be described in relation to the parallel fabrication of a plurality of optical components, because this type of fabrication may be the most relevant scenario in the context of small footprint systems. It is however understood that in principle the aspects discussed in relation to the method 300 may apply in a corresponding manner to the fabrication of a single optical component. FIG.3E shows an optical component 350 resulting from the fabrication method 300.

[0045] With reference to FIG.3A and 3B, the method 300 may include, in 310, providing a plurality of optical elements 302 on a first surface 304a of a substrate 306. In the exemplary configuration in FIG.3B three optical elements 302 are shown, but the method 300 may include providing any suitable number of optical elements 302, e.g. two, three, four, five, ten, one hundred, one thousand, or more than one thousand optical elements 302. In a preferred configuration the method 300 may include providing a plurality of lens elements configured to implement a predefined lens function. For example, the method 300 may include providing a plurality of microlens arrays. It is however understood that in principle the aspects proposed herein may apply to any suitable optical element 302 configured to implement any suitable optical function for manipulating light passing through the optical element 302.

[0046] In a preferred configuration, e.g. in the context of WLO fabrication, providing 310 the plurality of optical elements 302 may include forming the plurality of optical elements 302 on the first surface 304a of the substrate 306. Stated in a different fashion, the method 300 may include forming a plurality of optical surfaces 302 on the surface 304a of the substrate 306. In particular, the method 300 may include carrying out a replication process to form the plurality of optical elements 302 on the first surface 304a of the substrate 306. For example, the method 300 may include disposing a material for forming the optical elements 302 in a replication tool. The replication tool may be shaped according to a target profile for the optical elements 302. For example, the replication tool may have a plurality of replication sites shaped as the “negative” of the target profile for the optical elements 302 (e.g., for a convex optical element the replication site may have a concave shape, for a concave optical element the replication site may have a convex shape, etc.). Providing 310 the optical elements 302 may further include disposing a material of the optical elements 302 in the replication sites, and bringing the material in contact with the substrate 306, such that the material distributes on the substrate 306 according to the shape of the replication sites. Providing 310 the optical elements 302 may further include causing a hardening of the material to form the optical elements 302. For example, providing 310 the optical elements 302 may include curing the material (e.g., via UV irradiation, or via heating), to form the optical elements 302 on the first surface 304a of the substrate 306.

[0047] It is understood that providing 310 the optical elements 302 may alternatively be carried out in a different manner, e.g. according to techniques other than WLO fabrication. As another example, providing 310 the optical elements 302 may include disposing preformed optical elements 302 on the surface 304a of the substrate 306. Illustratively, in this scenario the method300 may include forming the optical elements 302 (according to any suitable technique) and disposing the formed optical elements 302 on the substrate 306.

[0048] In general, an optical element 302 may be configured to provide a predefined optical function, e.g. an optical element 302 may be configured as a lens element to provide a predefined lens function. Illustratively, an optical element 302 may be configured to refract light passing through the optical element 302, and the type of refraction may vary depending on the type of configuration of the optical element. Stated in a different fashion, an optical element 302 may be configured to receive input light at an input side and provide output light at an output side, wherein the output light is modified according to the optical function of the optical element 302, e.g. the output light may be collimated, focused, and the like.

[0049] In a simple configuration, the optical elements 302 may all have the same configuration. Illustratively, all the optical elements 302 may be configured according to the same type (e.g., lens type) to implement the same optical function. In other aspects, different optical elements 302 may have different configurations. For example, a first optical element may be of a first type (e.g., a concave lens) and configured to implement a first optical function, a second optical element may be of a second type (e.g., a convex lens) and configured to implement a second optical function, a third optical element may be of a third type and configured to implement a third optical function, etc.

[0050] As possible types, at least one optical element 302 (e.g., each optical element 302) may be configured as a plano-convex lens, as a plano-concave lens, as a positive meniscus lens (a convex-concave lens thicker at the center than at the edges), as a negative meniscus lens (a convex-concave lens thicker at the edges than at the center), as a biconvex lens, or as a biconcave lens.

[0051] In a preferred configuration, at least one optical element 302 (e.g., each optical element 302) may be a microlens array (MLA). A microlens array may include a plurality of lenslets arranged in a one-dimensional or two-dimensional fashion. The number and dimensions of the lenslets, and the pitch of the array, may be freely adapted depending on the intended application and overall dimensions of the corresponding optical component 350 (and optoelectronic device). For example, considering a MLA, the field of view or illumination may be defined by the lens profile of each lenslet. A MLA may be a particularly relevant component for small footprint optoelectronic devices. It is however understood that also other types of optical elements / lens elements may be provided, as discussed above. As a further example, an optical element 302 may include a stack of lenses, illustratively a plurality of lens elements stacked on top of one another.

[0052] In general, considering the presence of the substrate 306, an optical element 302 disposed on the substrate 306 may have at least one planar surface, illustratively a flat surface. The planar surface may be in contact with the substrate 306, while the other surface of the optical element 302 may be a curved surface, e.g. with a convex shape or a concave shape, or a plurality of curved surfaces in case of a MLA.

[0053] The material of the optical elements 302 may be freely adapted, e.g. depending on the type of fabrication process used. In general, an optical element 302 may include or may be made of a material that allows transmission of light in the predefined wavelength range in which the optical component 350 should operate (e.g., visible, near-infrared, etc.). As a numerical example, an optical element 302 may include or may be made of a material configured to have a transmission greater than 90% in the wavelength ranges discussed in relation to the optoelectronic device 100 in FIG.1 A and FIG. IB, for example a transmission greater than 94%.

[0054] An example of particular relevance in the WLO context, at least one optical elements 302 (e.g., each optical element 302) may include or consist of an epoxy material. Epoxy may enable a scalable and reproducible fabrication of optical elements 302, e.g. in the context of wafer-level optics techniques, while also providing suitable optical properties. Furthermore, in the context of wafer-level processing, epoxy materials may be precisely disposed and patterned using well-established techniques. As other suitable examples, at least one optical elements 302 (e.g., each optical element 302) may include or may be made of glass, a thermal plastic material (acrylate or polycarbonate based), or an optical polymer material, e.g. an UV-curable polymer such as an acrylate resin, and the like. In general, all optical elements 302 may include or consist of the same material, but in principle a configuration in which different optical elements 302 include different materials may also be provided.

[0055] The dimensions of the optical elements 302 may be adapted according to the dimensions of the corresponding optoelectronic device. As an example, at least one optical elements 302 (e.g., each optical element 302) may have an extension 314 in a direction perpendicular to the surface 304a of the substrate 306 in the range from 1 pm to 100 pm, for example in the range from 5 pm to 50 pm, for example in the range from 10 pm to 30 pm. The extension 314 in the direction perpendicular to the surface 304a may be referred to as thickness or height of the optical element 302. The direction perpendicular to the surface 304a may be for example parallel to the optical axis of the optical element 302. The extension 314 may be defined, for example, in correspondence of the thickest portion of an optical element 302.

[0056] As another example, at least one optical element 302 (e.g., each optical element 302) may have a lateral extension 316 in a direction parallel to the surface 304a of the substrate 306in the range from 100 gm to 10 mm, for example in the range from 500 gm to 1 mm. Such lateral extension 316 may illustratively be in a plane defined by the surface 304a of the substrate 306, e.g. a plane parallel to the surface 304a of the substrate 306. Such lateral extension 316 may be referred to as width, or diameter.

[0057] It is however understood that the fabrication strategy proposed herein may apply in a corresponding manner to optical elements 302 having other dimensions (e.g., larger dimensions).

[0058] Turning now to the substrate 306, the substrate 306 may be any suitable type of substrate for the fabrication proposed herein. In general, the substrate 306 may be configured to be transparent for light in the wavelength range in which the resulting optical components (and corresponding optoelectronic devices) should operate. As a numerical example, the substrate 306 may include or may be made of a material configured to have a transmission greater than 90% in the wavelength ranges discussed in relation to the optoelectronic device 100 in FIG.1A and FIG. IB, for example a transmission greater than 94%. In some aspects, the substrate 306 may be configured to filter out light with wavelength outside the predefined wavelength range. For example, the material of the substrate 306 may be transmissive only in the desired wavelength range. As another example, the substrate 306 may have a coating configured to block light with wavelength outside the predefined wavelength range.

[0059] Considering the parallel fabrication, the material of the substrate 306 may be configured to allow cutting through the substrate 306 to singulate the optical components. In particular the material of the substrate 306 may be configured to allow using a punching tool to punch through the substrate 306 to singulate the optical components, as discussed in further detail below. As an example of particular relevance for a cost-efficient fabrication, the substrate 306 may include or may consist of a plastic material, e.g. the substrate 306 may be a plastic foil (or a plastic wafer). As another example, the substrate 306 may include or may consist of a polymer material, e.g. a transparent polymer. As another example, the substrate 306 may include or may consist of an epoxy material, e.g. the substrate 306 may be an epoxy foil (or epoxy wafer). As another example, the substrate 306 may include or may consist of a metal material, e.g. a transparent metal.

[0060] The dimensions of the substrate 306 may be adapted according to the dimensions of the corresponding optoelectronic device. As an example, the substrate 306 may have a dimension in the direction perpendicular to the surface 304a (a thickness of the substrate 306) in the range from 50 pm to 500 pm, e.g. in the range from 100 pm to 200 pm.

[0061] With reference to FIG.3A and 3C, the method 300 may further include, in 320, providing a respective solid adhesive element 308 for each optical element 302 of the plurality of optical elements 302. A solid adhesive element 308 may be provided on a second surface 304b of the substrate 306 such that the adhesive element 308 and the optical element 302 are in correspondence with one another, e.g. the adhesive element 308 may be provided in correspondence of the respective optical element 302. For example, an adhesive element 308 may be aligned with the respective optical element 302, e.g. a geometric center of the adhesive element 308 may be aligned with a geometric center of the respective optical element 302. The second surface 304b may be opposite to the first surface 304a. Illustratively, the first surface 304a may be a first main processing surface of the substrate 306, and the second surface 304b may be a second main processing surface of the substrate 306. The first surface 304a and the second surface 304b may face in opposite directions. For the sake of brevity a “solid” adhesive element 308 may also be referred to herein as adhesive element 308.

[0062] According to the approach proposed herein, a solid adhesive element 308 may have a lateral extension 318 less than the lateral extension 316 of the corresponding optical element 302. Illustratively, considering the lateral extension 318 in the direction parallel to the surface 304a, 304b of the substrate 306, the lateral extension 318 of each solid adhesive element 308 may be smaller than the lateral extension 316 of the corresponding optical element 302. The dimension of an adhesive element in the plane parallel to the surface 304a, 304b of the substrate 306 may thus be less than the dimension of the corresponding optical element 302. Considering a circular profile, a diameter of an adhesive element 308 may be less than the diameter of the corresponding optical element 302.

[0063] Compared to a conventional technique, the strategy proposed herein may thus be based on providing pre- structured adhesive elements 308 having a dimension that prevents the oozing phenomenon during singulation. Rather than laminating a layer of adhesive on the entire surface of the substrate (as in FIG.2B), the adapted method 300 includes instead an assembly of a pre- structured adhesive element 308 with a corresponding optical element 302, and the suitable dimensioning of the adhesive element 308 avoids the elastic deformation caused by the die cutting tool.

[0064] Providing 320 the adhesive elements 308 may include, for example, forming a layer of adhesive material, e.g. a sheet or foil of adhesive material, and structuring the layer of adhesive material to define the adhesive elements 308. For example, the method 300 may include cutting the layer of adhesive material to form the individual adhesive elements 308. In a preferred configuration the method 300 may include punching through the layer of adhesive materialusing a punching tool (e.g., a wafer punching machine) to form the individual adhesive elements 308. As will be discussed in further detail below, punching may be the preferred approach to define a rounded profile for the adhesive elements 308 (and the resulting optical component), e.g. a circular profile, which may be a preferred shape for the intended applications.

[0065] After the structuring to form the individual adhesive elements 308, the method 300 may include disposing the adhesive elements 308 on the second surface 304b of the substrate 306, each in correspondence of a respective optical element 302. For example, the adhesive elements 308 may be initially disposed on a carrier substrate or sacrificial substrate, and the substrate 306 may include alignment marks to allow aligning the adhesive elements 308 on the carrier substrate with the optical elements 302 on the substrate 302. The method 300 may include attaching the adhesive elements 308 on the second surface 304b of the substrate 306. Illustratively, the surface of the adhesive elements 308 facing towards the substrate 306 may be adhesive, and may allow bonding the adhesive elements 308 to the substrate 306.

[0066] It is understood that the sequence illustrated in FIG.3C may be a preferred configuration, in which the adhesive elements 308 are provided on the substrate 306 after the optical elements 302 have been provided / formed on the first surface 304a of the substrate 306. It is however understood that in principle also the opposite configuration may be provided, in which the adhesive elements 308 are structured and disposed on the substrate 306 prior to forming / disposing the optical elements on the first surface 304a of the substrate 306. In this scenario, the method 300 may include providing each optical element 302 in correspondence of the respective adhesive element 308, e.g. forming (replicating) each optical element 302 aligned with the respective adhesive element 308.

[0067] The dimensions of the adhesive elements 308 may be freely adapted, while ensuring the reduced extension compared to the respective optical element 302. An adhesive element 308 may be structured and disposed with respect to the corresponding optical element 302 such that a gap is formed between the edge of the adhesive element 308 and the projection of the edge of the optical element 302 on the second surface 304b. Illustratively, the smaller dimension may define an empty region between the border of the adhesive element 308 and the projection of the border of the optical element 302 on the second surface 304b. Considering a top view, e.g. from the standpoint of the optical axis of the optical element 302, the optical element 302 may fully overlap the adhesive element 308 and, in addition, a border portion of the optical element 302 may overlap with a region free of adhesive element 308. The extension of the border region in which the optical element 302 and the adhesive element 308 do not overlap may be adaptedconsidering the subsequent singulation process to ensure sufficient space for the singulation tool to cut through the substrate 306 without deforming the adhesive elements 308.

[0068] As a numerical example, the lateral extension 318 of an adhesive element 308 in the direction parallel to the surface 304a, 304b of the substrate 306 may be at least 10% less of the lateral extension 316 of the corresponding optical element 302, for example at least 20% less, for example at least 30% less. As another numerical example, the lateral extension 318 of an adhesive element 308 may be in a range from 30% of the lateral extension 316 of the corresponding optical element 302 to 90% of the lateral extension 316 of the corresponding optical element 302, e.g. in a range from 50% of the lateral extension 316 of the corresponding optical element 302 to 75% of the lateral extension 316 of the corresponding optical element 302.

[0069] As a further example, at least one adhesive element 308 (e.g., each adhesive element 308) may have an extension in a direction perpendicular to the surface 304b of the substrate 306 in the range from 1 pm to 100 pm, for example in the range from 5 pm to 50 pm, for example in the range from 10 pm to 30 pm. The extension in the direction perpendicular to the surface 304b may be referred to as thickness or height of the adhesive element 308.

[0070] In general, an adhesive element 308 may be structured to have any suitable profile for its perimeter. In a preferred configuration, at least one adhesive element 308 (e.g., each adhesive element 308) may have a circular profile. Illustratively, an adhesive element 308 may be formed having a cylinder shape, with a face of the cylinder disposed on the substrate 306. The projection of the perimeter of the adhesive element 308 on the substrate 306 may thus have a circular profile. It is however understood that an adhesive element 308 may have in principle any suitable profile, adapted according to the geometry of the device in which the optical component should be installed. As other examples, an adhesive element 308 may have an elliptical profile, a square profile, a rectangular profile, or any suitable polygonal profile.

[0071] Turning now to the choice of material, an adhesive element 308 may include or consist of any suitable adhesive material that may be provided in solid form. Illustratively, the material of an adhesive element 308 may be configured such that the surface 324 of the adhesive element 308 facing away from the substrate 306 is or remains adhesive with the adhesive element 308 being solid. Illustratively, each adhesive element 308 may have an adhesive surface 324 facing away from the substrate 306. The adhesive surface 324 may then allow coupling the optical component with a corresponding optoelectronic device. The material of the adhesive element 308 may further be transmissive for light in the operating wavelength range of the corresponding optical component. Illustratively, an adhesive element 308 may be transparentfor light in the operating wavelength range of the corresponding optical element 302. An adhesive element 308 may be for example understood as a double-sided adhesive solid layer, double-sided adhesive tape, double-sided adhesive sheet, or double-sided adhesive foil.

[0072] An adhesive element 308 is thus in solid form when the singulation occurs. It is however understood that the initial forming of the adhesive elements 308 may involve the use of liquid reagents. For example, the layer of adhesive may be formed by dispensing a liquid material and then causing a hardening of the liquid material to form the layer of adhesive, e.g. via UV irradiation, temperature, and the like.

[0073] In some aspects, the material of the adhesive elements 308 may be soft, to facilitate the subsequent bonding with the optoelectronic device. The term “soft” may describe that the adhesive element 308 is configured to deform upon application of a force (e.g., a compressive force). Stated differently, the adhesive elements 308 being “soft” may indicate that the adhesive element 308 may be configured to allow for a deformation of its shape (e.g., its thickness) upon application of a force onto the adhesive element 308. By way of illustration, an adhesive element 308 may have for example a “jelly-like” consistency that provides sufficient structure for the fabrication process and sufficient softness for the subsequent bonding step.

[0074] In a preferred configuration, an adhesive element 308 may be elastically deformable, e.g., may be configured to deform upon application of a force and to return to a non-deformed state when the force is no longer applied. By way of illustration, an adhesive element 308 may have a first shape when no force (e.g., no compressive force) is applied to the adhesive element 308, and may further have a second shape when a force (e.g., a compressive force) is applied to the adhesive element 308. The second shape may illustratively be a deformed shape in which the adhesive element 308 has a shape different from the original shape. In case of elastic deformation, the adhesive element 308 may be configured to return to the first (non-deformed) shape when the force is no longer applied.

[0075] In a preferred configuration, at least one adhesive element (e.g., each adhesive element 308) may include or may consist of an optically clear adhesive (OCA). Illustratively, an adhesive element 308 may be a solid OCA element, e.g. an OCA layer. As generally known in the art, OCA may be a transparent optical double-sided adhesive with light transmittance above 90% and capable of robust bonding. An OCA adhesive element may have a multi-layer structure including a light release film layer, a heavy release film layer, and an OCA optical adhesive layer sandwiched between the light release film layer and heavy release film layer. As exemplary material, an OCA adhesive element may include or may be made of an acrylate. Asanother exemplary material, an OCA adhesive element may include or may be made of polyamide.

[0076] It is however understood that an adhesive element 308 may in principle include or consist of another type of material, e.g. an epoxy, an adhesive polymer, and the like.

[0077] In some aspects, the method 300 may further include providing (e.g., forming, disposing) a protective layer on the adhesive surface 324 of the adhesive elements 308 that faces away from the substrate 306. The protective layer may be a removable layer that prevents contamination or damages to the adhesive surface 324 before the bonding with the optoelectronic device is to be carried out. In other aspects, the adhesive surface 324 of the adhesive elements 308 that faces away from the substrate 306 may be a free surface, i.e. not coupled to any other element or layer (prior to the bonding with the optoelectronic device).

[0078] With reference to FIG.3 A and 3D, the method 300 may further include, in 330, carrying out a singulation process to separate the plurality of optical elements 302 into individual optical components 350 (see also FIG.3E). Illustratively, the method 300 may include cutting through the substrate 306 to separate the optical elements 302 from one another and define single optical components 350 (each including a respective optical element 302, part of the substrate 306, and adhesive element 308). The singulation process may include using a die cutting tool 312 (also referred to herein as singulation tool) to cut through the substrate 306 between the optical elements 302 belonging to different optical components, so as to provide diced individual optical components 350.

[0079] According to the approach proposed herein, the adhesive elements 308 may be configured (e.g., structured) such that the adhesive elements 308 do not undergo an elastic deformation (at the border region) during the singulation process. Illustratively, the lateral extension 318 of an adhesive element 308 may be selected such that the die cutting tool 312 may cut through the substrate 306 without cutting through the adhesive element 308. Stated in a different fashion, the lateral extension 318 of an adhesive element 308 may be such that a gap is formed between the edge(s) of the adhesive element 308 and the die cutting tool 312 when the die cutting tool 312 cuts through the substrate 306. The gap ensures that the adhesive element 308 remains untouched, thus preventing the oozing phenomenon.

[0080] The die cutting tool 312 may in principle have any suitable configuration to cut through the substrate 306. For example the die cutting tool 312 may include one or more blades, e.g. one for each optical element 302. As another example, the die cutting tool 312 may include a single blade and a mechanical system to vary the relative position of the blade with respect to the substrate 306 for cutting along different directions.

[0081] In a preferred configuration, the singulation process 330 may include punching through the substrate 306 in correspondence of each optical element 302 to separate the optical elements into individual optical components 350. In this scenario, the die cutting tool 312 may be a punching tool, e.g. a die punching machine, capable of providing a cut through the substrate 306 with a rounded cross section, e.g. a circular cross section. The use of a punching tool allows obtaining optical elements 350 having a rounded profile (when seen in a top view), which is a relevant geometry for typical end applications.

[0082] In this scenario, the die cutting tool 312 (punching tool) may include a plurality of punching sites to punch through the substrate 306 in correspondence of each optical element 302, each shaped according to the desired cross-section of the cut. For example, at least one punching site (e.g., each punching site) may have a cross-section with a rounded edge, e.g. a circular cross-section, such that a cut having a circular cross section is provided by punching through the substrate 306. The pre-structuring of the adhesive elements 308 before the punching ensures a gap between the perimeter of the punching site and the perimeter of the adhesive elements 308. It is understood that also other shapes / profiles may be provided, e.g. elliptical, square, rectangular, any suitable polygonal shape, etc.

[0083] It is understood that the use of a die cutting tool 312 is an example that provides a cost- and resource-efficient fabrication process, but in principle the singulation may be carried out via other methods, e.g. using via laser cutting, pressurized water cutting, and the like.

[0084] The resulting optical components 350 (see FIG.3E) may thus include a substrate 306 shaped according to the cut defined by the die cutting tool 312. In a preferred configuration, the substrate 306 of the optical element 350 may have at least one rounded edge, e.g. the substrate 306 may have a circular profile (e.g., in a top view along the direction of the optical axis of the optical component 350).

[0085] According to various aspects, as shown in FIG.3D, the singulation process 330 may include cutting through the optical elements 302 in addition to cutting through the substrate 306. This may ensure a compact dimension for the resulting optical component 350, in which the optical element 302 fully occupies the surface of the substrate 306, without having an empty border region of substrate 306 around the optical element 302. For example, considering a die cutting tool 312 configured as punching tool, the punching sites may be dimensioned with a lateral extension (e.g., a diameter) smaller than the lateral extension 316 of the optical elements 302 (and greater than the lateral extension 318 of the adhesive elements 308), such that upon punching through the substrate 306 the punching tool also punches through the optical element(s) 302.

[0086] By cutting (e.g., punching) through the optical elements 302 the profile of the optical elements 302 may be precisely defined. In the preferred configuration, in the resulting optical component 350, the optical element 302 may have the same dimensions as the substrate 306 (e.g., the same diameter), and may have the same profile as the substrate 306, e.g. a profile with at least one rounded edge, e.g. a circular profile. Such configuration may be seen in FIG.3E that shows a side view 350a and a bottom view 350b of an optical component 350 obtained via the method 300. In such configuration, the optical element 302 may fully overlap with the substrate 306, e.g. the optical element 302 may fully cover the (first) surface of the substrate 306. It is however understood that in principle a border region may be left by cutting the substrate 306 at a distance from the border of the optical element 302.

[0087] As shown in FIG.3E, in the resulting optical component(s) 350, a gap 322 is formed between the border of the adhesive element 308 and the border of the optical element 302 (and of the substrate 306). Illustratively, a portion of the second surface of the substrate 306 on which the adhesive element 308 is disposed remains free of adhesive element 308. The border of the substrate 306 around the adhesive element 308 may thus be not covered by the adhesive element 308 in view of the adopted fabrication process. As shown in FIG.3E, in the preferred configuration, the adhesive element 308 may have the same profile as the optical element 302 and the substrate 306, with a reduced dimension, e.g. a circular profile.

[0088] In the resulting optical component 350 the adhesive element 308 does not protrude from the border of the substrate 306, e.g. in a top view along the direction of the optical axis of the optical component 350. Stated in a different fashion, the substrate 306 includes a perimeter region or border region extending beyond the perimeter / border of the adhesive element 308.

[0089] The method 300 adapted as proposed herein may thus include an assembly of a pre- structured (e.g., pre-punched) adhesive, such as an OCA, that is disposed (e.g., attached) in correspondence of each optical element 302, for example using alignment marks. Instead of the lamination on the entire substrate, the pre- structured adhesive elements 308 are smaller than the die cutting tool used for singulation, and remain thus unaffected by the singulation process. Considering the proposed process flow and design, the resulting optical component 350 has a smaller dimension on the adhesive element 308 (e.g., OCA) with respect to the optical element 302. This adapted process steps and the use of a suitable die cutting tool provide a good tolerance control between the optical element 302 and the adhesive element 308. The proposed process eliminates the oozing issue.

[0090] As discussed in relation to FIG.2A to FIG.2D, the conventional approach based on the lamination of the adhesive is not capable of eliminating the oozing issue. The lamination andcutting process deform the adhesive, e.g. the OCA. The lamination of the adhesive on the optical component at foil level cannot remove the oozing once the optical component is cut. On the contrary, the method proposed herein is adapted to eliminate the oozing phenomena on the adhesive during the cutting process of optical elements. The proposed approach eliminates the protrusion of the adhesive from the perimeter of the optical component. The proposed approach results in the absence of extra adhesive material left after the die cut.

[0091] By way of illustration, the proposed approach modifies the process flow from “adhesive lamination” to “pre-cut adhesive assembly” having an impact on final product design. The adhesive (e.g., OCA) is pre-cut in a separate step and attached to the optical component, e.g. using an alignment tool. The adhesive dimension is smaller compared to the final footprint of the optical element, thus solving two main issues, namely the oozing and the cosmetic crosscontamination. During the final die cut, the tool will be in contact only with the substrate (and optical element) producing a straight cut. Furthermore, the process will be cleaner without any adhesive residue on the tool blade.

[0092] According to various aspects, the method 300 may further include coupling an optical component 350 (e.g., each optical component) with an optoelectronic device, e.g. a device configured as the optoelectronic device 100 in FIG.1A. The method 300 may further include bonding the optical component 350 to the optoelectronic device using the adhesive element 308, illustratively using the adhesive surface 324 of the adhesive element 308 facing away from the substrate 306. For example, the method 300 may include bonding the optical component 350 to the housing of the optoelectronic device. The coupling / bonding may include optically coupling the optical element 302 of the optical component 350 with an active optoelectronic component of the device, e.g. to define a field of view for a light detecting optoelectronic component or a field of illumination for a light emitting optoelectronic component. For example, considering an MLA as optical element 302, the method 300 may include coupling / bonding the optical component to provide a light projector.

[0093] In the configuration in FIG.3A to FIG.3E the optical element(s) 302 and adhesive element(s) 308 are shown in direct physical contact with the substrate 306. Illustratively, in the method 300 the optical elements 302 may be disposed / formed directly on the first surface 304a of the substrate 306, and the adhesive elements 308 may be disposed / attached directly on the second surface 304b of the substrate 306. This configuration may represent the preferred scenario, in which the resulting optical component 350 consists of the relevant elements, i.e. optical element 302, substrate 306, and adhesive element 308. It is however understood that in principle an optical component 350 may include additional elements to implement variousoptical functionalities, and the method 300 may include corresponding steps to deposit / form the additional elements.

[0094] As an example, the optical component 350 may include an aperture element configured to define an aperture (in other words, an opening) for the optical component 350 to, during an operation of the optical component 350, partially block light and partially allow light to pass through the aperture. The aperture element may include a material that is non-transmissive for the wavelength range in which the optical component 350 operates, and may include an area free of the non-transmissive material to define the opening. The opening may illustratively be a clear aperture through which light may propagate. The aperture element may contribute to the suppression of stray light, e.g. in the context of light detection. As exemplary materials, the aperture element may include a metal, such as chrome, e.g. black chrome.

[0095] For example, the aperture element may be disposed on the first surface 304a of the substrate 306, e.g. between the substrate 306 and the optical element 302. For example, the method 300 may include forming the aperture elements before providing the optical elements 302, e.g. via deposition and structuring of a non-transmissive layer. As another example, the aperture element may be disposed on the second surface 304b of the substrate 306, e.g. between the substrate 306 and the adhesive element 308. For example, the method 300 may include forming the aperture elements before providing the adhesive element 308, e.g. via deposition and structuring of a non-transmissive layer. The aperture may be aligned with the respective optical element 302, e.g. the center of the aperture may correspond to the center of the optical element 302.

[0096] As another exemplary configuration, additionally or alternatively, the optical component 350 may include a spectral filter. The spectral filter may be configured to filter light, e.g. to block light with wavelength outside a predefined wavelength range. For example, the spectral filter may enhance the signal to noise ratio of imaging carried out using the optical component 350. The spectral filter may be configured to block light with wavelength outside any suitable wavelength range according to the desired application of the optical component 350 (and corresponding optoelectronic device). As an example, the spectral filter may block light with wavelength outside of the visible range. As another example, the spectral filter may block light with wavelength outside of the near-infrared range. In a preferred configuration, the spectral filter may block light with wavelength outside of (only) part of the near-infrared range, illustratively a limited bandwidth within the near-infrared range. In this regard, the spectral width of the predefined wavelength range may be adapted according to a desired balance between the selectivity of the filter and the necessity to allow sufficient light to reach the imagesensor. In a corresponding manner, as an alternative configuration, the spectral filter may be configured to allow to pass light with wavelength in a predefined wavelength range, e.g. the spectral filter may be configured as a bandpass filter (e.g., a near infrared bandpass filter).

[0097] The spectral filter may be disposed at any suitable location within the optical component 350. For example, the spectral filter may be disposed on the first surface 304a of the substrate 306, e.g. between the substrate 306 and the optical element 302. For example, the method 300 may include forming the spectral filters before providing the optical elements 302, e.g. via deposition and structuring of a filter layer. As another example, the spectral filter may be disposed on the second surface 304b of the substrate 306, e.g. between the substrate 306 and the adhesive element 308. For example, the method 300 may include forming the spectral filters before providing the adhesive element 308, e.g. via deposition and structuring of a filter layer.

[0098] As a further exemplary configuration, additionally or alternatively, the optical component 350 may include one or more anti -reflective features, e.g. anti -reflective nanostructures. For example, at least one optical element 302 (e.g., each optical element 302) may have a structured surface that provides anti -reflective properties. A nanostructured surface may be configured in any suitable manner to provide anti -reflective properties. In general, a nanostructured surface may include an array of nanostructures, e.g. nano-pillars, nanopyramids, stochastic cloudlets, sponge-like nanostructures, and / or the like. The array of nanostructures forming the nanostructured surface may have a sub -wavelength pitch, illustratively a sub -wavelength center to center distance between neighboring nanostructures. The design of the nanostructured surface may thus be adapted according to the intended application of the optical component 350. The method 300 may thus include providing anti-reflective structures on the surface of at least one optical element 302 (e.g., each optical element 302).

[0099] FIG.4A to FIG.4C show different views of an exemplary optical component 400 in a schematic representation, according to various aspects. The optical component 400 may be an exemplary realization of an optical component 350, and may include an optical element 402 (e.g., a microlens array), a substrate 406 (e.g., a plastic foil), and an adhesive element 408 (e.g., an OCA tape). As visible in the exploded view 400a, top view 400b, and bottom view 400c, the adhesive element 408 does not cover the entire (second) surface of the substrate 406, leaving a free border region resulting from the pre-structuring of the adhesive element 408 before singulation. In the configuration in FIG.4A to FIG.4C, the microlens array may fully cover the (first) surface of the substrate 406, thus providing a compact arrangement for integration in a miniaturized device.

[0100] The word “on” or “over”, used herein to describe forming a feature, e.g. a layer “on” or “over” a surface (e.g., on / over another layer), may be used to mean that the feature, e.g., the layer, may be formed “directly on”, e.g. in direct contact with, the implied surface. The word “on” or “over”, used herein to describe forming a feature, e.g. a layer “on” or “over” a surface, may be used to mean that the feature, e.g. the layer, may be formed “indirectly on” the implied surface with one or more additional layers being arranged between the implied side or surface and the formed layer.

[0101] The term “thickness” used with regards to a “thickness” of a layer may be used herein to mean the dimension (in other words an extent) of the layer perpendicular to the surface of the support (the material or material structure) on which the layer is formed (e.g., deposited or grown). If a surface of the support is parallel to the surface of the carrier (e.g. parallel to the main processing surface) the “thickness” of the layer formed on the surface of the support may be the same as the height of the layer.

[0102] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

[0103] The phrase “at least one” and “one or more” may be understood to include a numerical quantity greater than or equal to one (e.g., one, two, three, four, [...], etc.). The phrase “at least one of’ with regard to a group of elements may be used herein to mean at least one element from the group consisting of the elements. For example, the phrase “at least one of’ with regard to a group of elements may be used herein to mean a selection of: one of the listed elements, a plurality of one of the listed elements, a plurality of individual listed elements, or a plurality of a multiple of individual listed elements.

[0104] The term “epoxy” may be used herein as commonly understood in the art to describe a thermosetting polymer that includes epoxide groups. The term “epoxy” may be used herein to refer both to the “uncured” state (or non-hardened state) and the “cured” state (or hardened state, or cross-linked state) of the material. In some aspects, the term “epoxy resin” may be used to refer to the material in its “uncured” state. The epoxy may go from the “uncured” state to the “cured” state by means of a treatment that causes a cross-linking of the polymer chains. Illustratively, an epoxy resin may harden via chemical reactions that may be induced in any suitable manner (e.g., via a heat treatment or via irradiation with ultraviolet light), or by combining the epoxy resin with other components (illustratively, with a “hardener”). The term “epoxy lens” may be used herein to describe an optical element that substantially consists of epoxy material, e.g. an optical element made of epoxy material by more than 50% by volume,or by more than 70% by volume, or by more than 90% by volume, or by more than 99% by volume. An “epoxy lens” may include a single epoxy material or a combination (a mixture) of epoxy materials.

[0105] All acronyms defined in the above description additionally hold in all claims included herein.

[0106] While the invention has been particularly shown and described with reference to specific aspects, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes, which come within the meaning and range of equivalency of the claims, are therefore intended to be embraced.List of reference signs100 Optoelectronic device 316 Lateral extension100a Light-emitting device 318 Lateral extension100b Light sensing device 320 Method step102 Optoelectronic component 322 Gap portion104 Optical component 324 Adhesive surface106 Processing circuit 330 Method step108 Substrate 350 Optical component110 Housing 350a Side view120 Imaging device 350b Bottom view122 Emitted light 400 Optical component124 Received light 400a Exploded view126 Processing circuit 400b Top view130 Field of view 400c Bottom view200 Method 402 Optical element202 Optical element 406 Substrate204 Substrate 408 Adhesive element206 Adhesive layer208 Die cutting tool210 Method step212 Oozing portion220 Method step230 Method step250 Optical component250a Side view250b Top view300 Method302 Optical element304a First surface306 Substrate308 Adhesive element310 Method step314 Thickness

Claims

Claims1. A method (300) of forming an optical component (350), the method (300) comprising: providing (310) a plurality of optical elements (302) on a first surface (304a) of a substrate (306); for each optical element (302) of the plurality of optical elements (302): providing (320) a respective solid adhesive element (308) on a second surface (304b) of the substrate (306) in correspondence of the respective optical element (302), wherein the second surface (304b) is opposite to the first surface (304a), wherein the adhesive element (308) corresponding to the optical element (302) has a lateral extension (318) in a plane parallel to the surface (304a, 304b) of the substrate (306) less than a lateral extension (316) of the optical element (302) in the plane; and carrying out a singulation process (330) to separate the plurality of optical elements (302) into individual optical components (350).

2. The method (300) according to claim 1, wherein carrying out a singulation process (330) comprises using a die cutting tool (312) to cut through the substrate (306) to separate the plurality of optical elements (302), wherein the lateral extension (318) of the adhesive elements (308) defines a gap between the respective border of each adhesive element (308) and the die cutting tool (312) when the die cutting tool (312) cuts through the substrate (306).

3. The method (300) according to claim 2, wherein the die cutting tool (312) is configured as a punching tool to punch through the substrate (306) to separate the plurality of optical elements (302).

4. The method (300) according to claim 3, wherein the punching tool has a plurality of punching sites to punch through the substrate (306) in correspondence of each optical element (302), wherein at least one punching site has a cross-section having at least one rounded edge to define a profile with at least one rounded edge for the respective optical component (350).

5. The method (300) according to any one of claims 2 to 4, wherein carrying out a singulation process (330) comprises using the die cutting tool (312) to cut through the optical elements (302) in addition to cutting through the substrate (306) to provide the individual optical components (350).

6. The method (300) according to claim 5, wherein the die cutting tool (312) is configured as a punching tool with a plurality of punching sites, wherein each punching site has a lateral extension smaller than the lateral extension (316) of the respective optical elements (302) and greater than the lateral extension (318) of the respective adhesive elements (308).

7. The method (300) according to any one of claims 1 to 6, wherein providing (310) the plurality of optical elements (302) comprises carrying out a replication process to form the plurality of optical elements (302) on the first surface (304a) of the substrate (306).

8. The method (300) according to any one of claims 1 to 7, wherein at least one optical element (302) is configured as a microlens array.

9. The method (300) according to any one of claims 1 to 8,wherein the substrate (306) is or comprises a plastic foil configured to be transparent for light with wavelength in an operating wavelength range of the optical components (350).

10. The method (300) according to any one of claims 1 to 9, wherein providing (320) a respective solid adhesive element (308) for each optical element (302) comprises: forming a layer of adhesive material; structuring the layer of adhesive material to define the individual solid adhesive elements (308); and disposing each solid adhesive element (308) on the second surface (304b) of the substrate (306) in correspondence of the respective optical element (302).

11. The method (300) according to any one of claims 1 to 10, wherein at least one adhesive element (308) comprises or consists of an optically clear adhesive.

12. The method (300) according to any one of claims 1 to 11, further comprising: bonding an optical component (350) with an optoelectronic device (100) using an adhesive surface of the respective adhesive element (308), wherein the optoelectronic device (100) comprises an active optoelectronic component (102) configured to emit light or detect light, and wherein the bonding comprises optically coupling the optical element (302) of the optical component (350) with the active optoelectronic component (102).

13. An optical component (350) comprising: a substrate (306) configured to be transparent for light in an operating wavelength range of the optical component (350);an optical element (302) disposed on a first surface (304a) of the substrate (306), wherein the optical element (302) is configured to provide a predefined optical function; and a solid adhesive element (308) disposed on a second surface (304b) of the substrate (306) in correspondence of the optical element (302), wherein the second surface (304b) is opposite to the first surface (304a), wherein the solid adhesive element (308) has a lateral extension (318) in a plane parallel to the surface (304a, 304b) of the substrate (306) less than a lateral extension (316) of the optical element (302) in the plane.

14. The optical component (350) according to claim 13, wherein the optical element (302), the substrate (306), and the solid adhesive element (308) have a profile with at least one rounded edge.

15. The optical component (350) according to claim 13 or 14, wherein the optical element (302) is configured as a microlens array, and wherein the solid adhesive element (308) comprises or consists of an optically clear adhesive.

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