A measuring system for measuring a distance of a gap between a donor substrate and a target substrate, and a corresponding control system as well as related methods

Abstract

A measuring system arranged for measuring a distance of a gap between a donor substrate and a target substrate, the measuring system comprising a light source, the donor substrate comprising at least one interconnect material for mounting an electronic component on the target substrate, which is positioned next to the donor substrate such that the gap arises between the target substrate and the donor substrate, wherein the target substrate is arranged to at least partially reflect the light that partially transmitted the donor substrate towards the optical sensor, the optical sensor arranged for capturing the reflected light from the donor substrate and from the target substrate and arranged for measuring the distance of the gap between the donor substrate and the target substrate by determining the difference in focal distance of the light reflected from the donor substrate and light reflected from the target substrate.

Description

[0001] Title

[0002] A measuring system for measuring a distance of a gap between a donor substrate and a target substrate, and a corresponding control system as well as related methods.

[0003] Technical field

[0004] The present disclosure relates to the field of optical measurement techniques, specifically measuring a distance of a gap between a donor substrate having at carrying a depositable material and a target substrate, wherein material is to be deposited on said target substrate.

[0005] Background

[0006] Semiconductor manufacturing is a complex and highly precise process that involves the fabrication of integrated circuits, ICs, onto substrates such as silicon wafers. These ICs serve as the building blocks of electronic devices, ranging from smartphones and computers to automotive electronics and medical devices. The relentless demand for smaller, faster, and more efficient electronic components has driven the development of advanced manufacturing techniques, including laser- assisted IC transfer methods.

[0007] The process of mounting electronic components such as ICs onto a target substrate such as a printed circuit board, PCB, is a step in electronics assembly. Traditionally, ICs are soldered onto PCBs using techniques such as surface-mount technology, SMT, or through-hole technology, THT. SMT components are significantly smaller than through-hole components, making precise positioning crucial. Even a slight misalignment can lead to electrical connection issues or physical damage during assembly or operation.

[0008] The transfer of interconnect material from a plate containing the interconnect material to the PCB may be facilitated by a precision laser system, this transfer process is called LIFT (Laser-Induced Forward Transfer). This laser system may be capable of emitting focused beams of light with extremely high intensity and accuracy. During the transfer process, the plate containing the interconnect material may be aligned with the target locations on the PCB. The control offered by the laser allows for accurate deposition of the interconnect material with sub-micron precision, ensuring optimal electrical and mechanical connections.

[0009] One of the advantages of laser-assisted interconnect material transfer may be its precision of deposition of the material to the target substrate, other advantages include versatility to deposit a variety of materials onto PCB substrates.

[0010] One of the downsides related to the laser deposition of electronic components from the donor substrate to the target substrate is that the distance of the gap between the donor substrate and the target substrate may determine the successful deposition, which if not carefully managed, will impact the components functionality.

[0011] Summary

[0012] It would be advantageous to achieve a measuring system for measuring the distance of a gap between the donor substrate and the target substrate. It would further be advantages to achieve a corresponding control system and related methods.

[0013] In the first aspect of the present disclosure, there is provided a measuring system arranged for measuring a distance of a gap between a donor substrate and a target substrate, the measuring system comprising: a light source arranged for emitting light; the donor substrate comprising at least one interconnect material for mounting an electronic component on the target substrate and / or at least one electronic component, the donor substrate being arranged for receiving the emitted light and for partially reflecting the emitted light towards an optical sensor and for allowing light to partially transmit the donor substrate towards the target substrate; the target substrate, positioned next to the donor substrate such that the gap arises between the target substrate and the donor substrate, wherein the target substrate is arranged to at least partially reflect the light that partially transmitted the donor substrate towards the optical sensor; the optical sensor arranged for capturing the reflected light from the donor substrate and from the target substrate and arranged for measuring the distance of the gap between the donor substrate and the target substrate by determining the difference in focal distance of the light reflected from the donor substrate and light reflected from the target substrate.

[0014] The inventors have found that it may be beneficial to include a light source in combination with an optical sensor for measuring the distance of the gap between the donor substrate and the target substrate. Here, the donor substrate may be partially transparent such that at least some of the light, from the light source, is reflected towards the optical sensor and some of the light is allowed to pass through the donor substrate towards the target substrate. The light is then at least partially reflected from the target substrate to the optical sensor.

[0015] The above allows the optical sensor to determine the distance of the gap between the donor substrate and the target substrate. Using the differences in focal distance of the reflected light, a distance between the reflection points can be measured. This method can be employed to obtain the distance between a gap existing between the donor substrate and the target substrate

[0016] The donor substrate may be made of a transparent material such as glass, quartz, or plastic or the like. It may comprise a transparent region, used for receiving the light from the light source, and a region in which the at least one interconnect material for mounting an electronic component on the target substrate and / or at least one electronic component is present. This region may contain a light absorbing layer, which may absorb the light emitted from a laser to disconnect the at least one interconnect material for mounting an electronic component on the target substrate and / or at least one electronic component from the donor substrate and deposit it on the target substrate.

[0017] When light encounters an interface between two different materials, such as a transparent substrate, like glass or plastic, and air or vacuum or the like, several optical phenomena may occur, including reflection, refraction, and transmission.

[0018] Light may thus be emitted towards a transparent donor substrate and encounters the interface between the donor substrate and, for example, air, both reflection and refraction can occur.

[0019] Reflection may occur as some of the light that strikes the interface may be reflected back into the air. Refraction may occur as not all of the light may be reflected. Some of the light may penetrate into the transparent substrate. When light passes from one medium, such as air, into another, such as plastic, its speed changes, causing the light rays to bend. This bending of light is called refraction. The degree of bending depends on the refractive indices of the two materials and the angle at which the light strikes the interface.

[0020] When light is emitted towards a transparent substrate and encounters the interface between the substrate and, for example air, some of the light will be reflected back into the air, while the rest will be refracted (in case the light is received in an angle, i.e. not perpendicular) and may penetrate into the substrate.

[0021] In the present disclosure, the reflection from the donor substrate may be realized by a first interface, i.e. the interface defined by the light going from the light source into the donor substrate or may be realized by a second interface, i.e. the interface defined by the light going from the donor substrate to the gap, i.e. in the direction towards the target substrate.

[0022] In the present disclosure, the reflection from the target substrate is typically realized by a third interface, i.e. the interface between the gap and the target substrate but, alternatively, may be realized by a fourth interface, i.e. the interface between the target substrate and a subsequent medium.

[0023] The discrepancy of the reflected light by the second interface of the donor substrate and the reflected light by the first interface of the target substrate may be defined by the focal distance of the reflected light, which then corresponds to a distance between the location of the second interface of the donor substrate and the first interface of the target substrate. This distance may be the distance of the gap between the donor substrate and the target substrate. Alternatively, the distance of the first interface of the donor substrate and the first interface of the target substrate may be determined by the focal distance of the reflected light by the first interface of the donor substrate and the reflected light by the first interface of the target substrate.

[0024] This measurement method may use a light source and a optical sensor, which could be a confocal sensor, to emit and capture the light.

[0025] One of the advantages of using this measurement system is that it allows for remote sensing, as opposed to for example typical tactile based methods. An other advantage is that it only uses one sensor to measure the distance between the two plates, while other methods need additional sensors to determine the distance of the gap. Using only one sensor simplifies the design and decreases costs.

[0026] Using multiple sensors allows for detecting the parallelism of the donor substrate and the target substrate. Parallelism refers to the alignment of two or more optical surfaces so that they are parallel to each other. This alignment ensures that light rays passing through or reflecting off these surfaces maintain their relative positions and directions. Achieving parallelism involves adjusting the orientation of the optical components so that their surfaces are parallel to each other. This can be done by carefully adjusting the position and angle of each component relative to the optical axis of the system. The tip and tilt of the components is measured by using the multiple sensors mentioned above, these can be used in a controller, which may use a feedback loop, which may include feed forward, to achieve parallelism.

[0027] The measurement system can be adjusted to position the optical sensor at an angle with respect to the donor substrate. Using a mirror, the emitted light is directed at least substantially perpendicularly to the donor substrate and the target substrate. This allows for the usage of a different space to place the optical sensor and light source, which means greater flexibility in the positioning of the measurement system.

[0028] The measurement system can be used in a control system. The control system includes a moveable body, which influences the positioning of the donor substrate and can move it in the direction to and / or away from the target substrate. This movable body is clamped or mounted to the donor substrate, which may use vacuum suction which may be in the transparent region of the donor substrate. A controller is arranged for controlling the moveable based on the measured distance between the donor substrate and the target substrate. Following this, the controller is able to position the donor substrate such that the measured distance between the donor substrate and the target substrate is in between 10pm - 100pm.

[0029] The accuracy in this distance may be on the order of a micrometer when using this measurement method in combination with a controller. This allows for the accurate transfer of the interconnect material, for example interconnect dots or semiconductor die, to the target substrate. which allows for accurate laser transfer of interconnect dots and semiconductor die to the target substrate. The above and other aspects of the disclosure will be apparent from and elucidated with reference to the examples described hereinafter.

[0030] Brief description of the figures

[0031] Fig. 1 shows an example of the gap measurement system in accordance with the present disclosure.

[0032] Fig. 2 shows an alternative configuration of the confocal sensor using a mirror in accordance with the present disclosure;

[0033] Fig. 3 shows the use of multiple sensors to detect the gap, tip and tilt between the donor substrate and the target substrate in accordance with the present disclosure.

[0034] Detailed description

[0035] It is noted that in the description of the figures, same reference numerals refer to the same of similar components performing a same of essentially similar function.

[0036] A more detailed description is made with reference to particular examples, some of which are illustrated in the appended drawings, such that the features of the present disclosure may be understood in more detail. It is noted that the drawings only illustrate typical examples and are therefore not to be considered to limit the scope of the subject matter of the claims. The drawings are incorporated for facilitating an understanding of the disclosure and are thus not necessarily drawn to scale. Advantages of the subject matter as claimed will become apparent to those skilled in the art upon reading the description in conjunction with the accompanying drawings.

[0037] The ensuing description above provides preferred exemplary example(s) only, and is not intended to limit the scope, applicability, or configuration of the disclosure. Rather, the ensuing description of the preferred exemplary example(s) will provide those skilled in the art with an enabling description for implementing a preferred exemplary example of the disclosure, it being understood that various changes may be made in the function and arrangement of elements, including combinations of features from different examples, without departing from the scope of the disclosure.

[0038] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to." As used herein, the terms "connected," "coupled," or any variant thereof means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, electromagnetic, or a combination thereof. Additionally, the words "herein," "above," "below," and words of similar import, when used in this application, refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word "or" in reference to a list of two or more items, covers all the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.

[0039] These and other changes can be made to the technology considering the following detailed description. While the description describes certain examples of the technology, and describes the best mode contemplated, no matter how detailed the description appears, the technology can be practiced in many ways. Details of the system may vary considerably in its specific implementation, while still being encompassed by the technology disclosed herein.

[0040] As noted above, particular terminology used when describing certain features or aspects of the technology should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the technology with which that terminology is associated. In general, the terms used in the following claims should not be construed to limit the technology to the specific examples disclosed in the specification, unless the Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the technology encompasses not only the disclosed examples, but also all equivalent ways of practicing or implementing the technology under the claims. Fig. 1 shows a control system comprising a measurement system in accordance with the present disclosure. The measurement system uses a sensor 101 , for example a confocal sensor, equipped with an optical sensor 101 and a light source 101. In this particular example, the optical sensor and the light source are embedded in a single package. This light source emits light, which travels towards the donor substrate 103, and via the gap 104 to the target substrate 105. The donor substrate partially reflects and partially allows light to pass in a direction towards the target substrate. The target substrate at least partially reflects the emitted light.

[0041] A confocal sensor is a type of optical sensor used for precise measurement and inspection tasks. It operates based on the principle of confocal microscopy, which involves using a focused beam of light to probe a sample and collect the reflected or emitted light. In a confocal sensor, a focused light beam may be directed onto the surface of the sample being measured. The light that interacts with the sample may then be collected through a confocal aperture, which may be positioned at the focal plane of the illumination optics. This aperture allows only the light that originates from the focal point of the beam to pass through, while rejecting light that comes from other parts of the sample.

[0042] As a result, only light that is in focus with the measurement plane may be detected. By precisely controlling the position of the focal point and analyzing the intensity of the collected light, confocal sensors can accurately measure surface topography, thickness, roughness, and other characteristics of the sample. Using this method, a different sensor can be constructed to arrange light as a function of the focal distance.

[0043] The donor substrate may be a transparent substrate in which parts of the substrate may be equipped with a light absorbing layer 109, which causes the interconnect material that is present 110, when exposed to a laser beam, to be transferred from the donor substrate to the target substrate. The transparent material can be, but is not limited to, glass or plastic. The donor substrate may be a at least substantially flush surface at the transparent part of the substrate. The donor substrate may consist of a material cavity 108 suited for fitting in the interconnect material. This material cavity causes the donor to not be substantially flush in the laser processing area 106 after laser processing The donor substrate may be positioned at least substantially parallel to the target substrate. The light reflected by the donor substrate and the light reflected by the target substrate can be used to gain knowledge about the distance between the two plates, meaning the width or distance of the gap between the substrates or plates.

[0044] For laser processing, an absorbing release layer may be added to the donor plate in a laser processing area, by this laser processing, the interconnect materials may be deposited onto the target substrate.

[0045] The target substrate may refer to a substrate used to receive the interconnect material, or an electronic component as an alternative, from the donor substrate. This interconnect material is, for example, solder paste, flux, glue, epoxy or anything alike.

[0046] The distance between the two plates can be utilized in a feedback loop of a control system with suitable actuators to be able to control the distance with an measured distance between the donor substrate and the target substrate of between 10pm - 100pm. The control system uses a clamping system 107, for example vacuum clamping, to attach a moveable body 102, which may be able to be moved by actuators, to the donor substrate, which may be with an accuracy on the order of a micron.

[0047] In fig. 2 an alternative configuration of the measurement system is shown, a (folding) mirror 202 may be used to direct the emitted light from the light source 201 perpendicularly to the donor substrate and the target substrate. This alignment is needed for the determination of the distance between the two substrates. The mirror can be positioned at any angle with respect to the normal of the donor substrate and the target substrate to allow for alternative space usage and possibly a more confined measurement system. The light emitted by the light source may be reflected by the donor substrate and the target substrate towards the optical sensor 201 as explained above. Similarly, the light source and optical sensor are packaged in for example a confocal sensor 201

[0048] In fig. 3 the measurement system is expanded by using at least two more, i.e. three confocal sensors (301 ,302,303) to be able to determine the tip and tilt, as well as the already able to be determined distances of the gaps between the donor substrate 103 and the target substrate 105. The tip and tilt can subsequently be used in a control system to control the parallelism of the system, which allows for more accurate deposition of interconnect material from the interconnect material occupied area 304 of the donor substrate onto the target substrate. The advantage of using three optical sensors simultaneously may be that the parallelism can be continuously monitored and controlled, which leads to fewer needed measurements at other locations to check the distance between the donor and target substrate

[0049] Other variations to the disclosed examples can be understood and effected by those skilled in the art in practicing the claimed disclosure, from a study of the drawings, the disclosure, and the appended claims. The provided figures and descriptions of the examples of the disclosure are illustrative and explanatory to the heart of the disclosure and should not be seen as limiting the disclosure thereto. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope thereof.

Claims

CLAIMS1. A measuring system arranged for measuring a distance of a gap between a donor substrate and a target substrate, the measuring system comprising: a light source arranged for emitting light; the donor substrate comprising at least one interconnect material for mounting an electronic component on the target substrate and / or at least one electronic component, the donor substrate being arranged for receiving the emitted light and for partially reflecting the emitted light towards an optical sensor and for allowing light to partially transmit the donor substrate towards the target substrate; the target substrate, positioned next to the donor substrate such that the gap arises between the target substrate and the donor substrate, wherein the target substrate is arranged to at least partially reflect the light that partially transmitted the donor substrate towards the optical sensor; the optical sensor arranged for capturing the reflected light from the donor substrate and from the target substrate and arranged for measuring the distance of the gap between the donor substrate and the target substrate by determining the difference in focal distance of the light reflected from the donor substrate and light reflected from the target substrate.

2. The measuring system in accordance with claim 1 , further comprising a confocal sensor, wherein the confocal sensor includes the light source and the optical sensor.

3. The measuring system in accordance with any of the previous claims, further comprising at least three optical sensors, wherein the at least three optical sensors are distributed with respect to a surface of the donor substrate.

4. The measuring system in accordance with any of the previous claims, further comprising a mirror to reflect light from the light source towards the donor substrate and to reflect light from the donor substrate and light from the target substrate towards the optical sensor.

5. The measuring system in accordance with any of the previous claims, wherein the donor substrate comprises a light absorbing layer covering the at least one interconnect material for mounting an electronic component on the target substrate and / or the at least one electronic component.

6. The measuring system in accordance with any of the previous claims, wherein a side of the donor substrate facing the target substrate is flush such that the distance of the gap between said donor substrate and said target substrate is at least substantially uniform.

7. A control system comprising a measuring system in accordance with any of the previous claims, wherein the control system comprises: a moveable body arranged for moving the donor substrate in the direction to and / or away from the target substrate; a controller arranged for controlling the moveable body based on the measured distance of the gap between the donor substrate and the target substrate.

8. A control system in accordance with claim 7, comprising a clamping unit to clamp the donor substrate to the moveable body.

9. A control system in accordance with any of the claims 7 - 8, wherein the controller is arranged to control the moving body such that the measured distance of the gap between the donor substrate and the target substrate is between 10pm - 100pm.

10. A method of operating the measuring system in accordance with any of the claims 1-6, wherein the method comprises: measuring, by the optical sensor, the distance of the gap between the donor substrate and target substrate based on difference in focal distance of the light reflected from the donor substrate and the light reflected from the target substrate.

11. A method of operating the measuring system in accordance with claim 10, and dependent on claim 3, wherein the method further comprises the step of: measuring, by the at least three optical sensors, the distance of the gap between the donor substrate and target at multiple locations.

12. A method of operating the control system in accordance with any of the claims 7-9, wherein the method comprises: controlling, by the controller, the moveable body based on the measured distance of the gap between the donor substrate and the target substrate.

13. A method of operating the control system in accordance with claim 12, and dependent on claim 6, wherein the method comprises the step of: controlling, by the controller, the moveable body such that the measured distances, at multiple locations, of the gap between said donor substrate and the target substrate are at least substantially uniform.

14. A computer program product comprising a computer readable medium having instructions stored thereon which, when executed by a controller, cause the controller to implement a method in accordance with any of the claims 10 - 13.

Images