Patent Application
20250210399
Substrates with electronically active components distributed over the extent of the substrate are used in a variety of electronic systems, for example, in flat-panel display components such as flat-panel liquid crystal or organic light emitting diode (OLED) displays, in imaging sensors, and in flat-panel solar cells. The electronically active components are typically either assembled on the substrate, for example using individually packaged surface-mount integrated-circuit components and pick-and-place tools, or by coating a layer of semiconductor material on the substrate and then photolithographically processing the semiconductor material to form thin-film circuits on the substrate. Individually packaged integrated-circuit components typically have smaller transistors with higher performance than thin-film circuits but the packages are larger than can be desired for highly integrated systems.
Methods for transferring small, active components from one substrate to another are described in U.S. Pat. Nos. 7,943,491, 8,039,847, and 7,622,367. In some such approaches, small integrated circuits are formed on a native semiconductor source wafer. The small, unpackaged integrated circuits, or chiplets, are released from their native source wafer by pattern-wise etching portions of a sacrificial layer located beneath the chiplets, leaving each chiplet suspended over an etched sacrificial layer portion by a tether physically connecting the chiplet to an anchor separating the etched sacrificial layer portions. A viscoelastic stamp is pressed against the process side of the chiplets on the native source wafer, adhering each chiplet to an individual stamp post. The stamp with the adhered chiplets is removed from the native source wafer. The chiplets on the stamp posts are then pressed against a non-native target substrate or backplane with the stamp and adhered to the target substrate.
In another example, U.S. Pat. No. 8,722,458 entitled Optical Systems Fabricated by Printing-Based Assembly teaches transferring light-emitting, light-sensing, or light-collecting semiconductor elements from a source wafer substrate to a destination substrate or backplane. Such micro-transferred components can provide the high performance of crystalline semiconductor components together with the small size of unpackaged dies.
Micro-transfer printing stamps are an important part of any micro-transfer printing system and method. Typically, each stamp comprises an array of individual stamp posts and each stamp post contacts a chiplet during printing. The structure of the stamp post can affect the chiplet pickup from a source wafer and the chiplet printing to a target substrate. In some designs, the distal end of each individual stamp post is flat. In other designs, the distal end of each individual stamp post is structured. For example, U.S. Pat. No. 9,412,727 discloses a stamp with micro-tips in a three-dimensional relief pattern. There is an ongoing need, therefore, for stamp structures that are highly reliable, provide excellent pick-up-and-print yields, and are easy-to-use for a variety of component micro-transfer printing processes.
The present disclosure provides, inter alia, devices, structures, systems, and construction methods for micro-assembling micro-components, such as micro-electronic components, micro-optical components, silicon components, and compound semiconductor components using a stamp-based micro-transfer printing process. Such micro-assembled micro-components and systems and structures comprising them are widely useful in electronic and photonic systems.
According to embodiments of the present disclosure, a method of micro-transfer printing can comprise providing a stamp (e.g., a visco-elastic stamp comprising PDMS), providing a micro-component source wafer comprising a micro-component disposed over a cavity in a surface of the micro-component source wafer and connected to the micro-component source wafer with a tether, contacting the stamp to the micro-component to adhere the micro-component to the stamp, and detaching the micro-component from the micro-component source wafer by moving the stamp at least in a horizontal direction parallel to the surface, and optionally in a vertical direction orthogonal to the surface (e.g., orthogonal to the horizontal direction), thereby fracturing or separating the tether. Detaching the micro-component from the anchor and from the micro-component source wafer can comprise fracturing (e.g., breaking) the tether or separating the tether from the micro-component or from the anchor and micro-component source wafer. Once detached (e.g., the tether is fractured or separated), the micro-component can be removed from the micro-component source wafer using any combination of vertical and horizontal movements of the stamp. The stamp can be controlled by a computer-controlled motion-control platform with optical or mechanical (or both) alignment capabilities.
Some embodiments comprise also moving the stamp in a vertical direction orthogonal to the surface to detach the micro-component from the anchor and micro-component source wafer. Some embodiments comprise moving the stamp in the vertical direction at the same time as moving the stamp in the horizontal direction. Some embodiments comprise moving the stamp in the vertical direction after moving the stamp in the horizontal direction.
In some embodiments, a movement of the stamp in the vertical direction to detach the micro-component is a movement toward the surface. In some embodiments, a movement of the stamp in the vertical direction to detach the micro-component is a movement toward the surface. In some embodiments, the movement of the stamp in the vertical direction to detach the micro-component is an alternation in movements toward and away from the surface (e.g., an oscillation or vibration).
In some embodiments, a movement of the stamp in the horizontal direction comprises a rotation of the stamp about a vertical axis extending in the vertical direction orthogonal to the surface and orthogonal to the horizontal direction.
In some embodiments, the tether extends horizontally in a horizontal tether direction away from an anchor portion of the micro-component source wafer toward the micro-component and moving the stamp comprises moving the stamp in the horizontal direction parallel to the surface and in the tether direction to stretch the tether. In some embodiments, the tether extends horizontally in a horizontal tether direction away from an anchor portion of the micro-component source wafer toward the micro-component and the horizontal direction parallel to the surface is orthogonal to the tether direction. Moving the stamp in the horizontal direction can comprise moving the stamp parallel to the surface and orthogonal to the tether direction. In some embodiments, the tether extends in a tether direction away from an anchor portion of the micro-component source wafer toward the micro-component and the direction parallel to the micro-component source wafer is orthogonal to the tether direction and moving the stamp comprises a rotation about a vertical axis extending in the vertical direction orthogonal to the surface that stretches (places under tension) a leading edge of the tether moving in the orthogonal direction and compresses the trailing edge of the tether.
In some embodiments, the horizontal direction is a combination of a rotation about a vertical axis extending in the vertical direction orthogonal to the surface and a translation (e.g., movement) of the micro-component over the surface in a horizontal direction.
In some embodiments of the present disclosure, the tether extends laterally from an edge of the micro-component to an anchor portion of the micro-component source wafer. In some embodiments of the present disclosure, the tether extends from a bottom of the micro-component to the micro-component source wafer.
In some embodiments, the stamp comprises a rigid back, a stamp post extends away from the rigid substrate, and a distal end of the stamp post contacts the micro-component. In some embodiments, the stamp comprises a pedestal disposed on the rigid substrate and a proximal end of the post is in contact with the pedestal or bulk layer.
According to embodiments of the present disclosure, a structure for micro-transfer printing can comprise a micro-component source wafer comprising a micro-component disposed over a cavity in a surface of the micro-component source wafer and connected to an anchor portion of the micro-component source wafer with a tether that extends from the anchor to the micro-component, and a stamp disposed in contact with the micro-component that adheres the micro-component to the stamp. The stamp provides force to (e.g., provides pressure to or pushes or pulls) the micro-component in a horizontal direction parallel to the surface. In some embodiments, the stamp also provides force to (e.g., provides pressure to or pushes or pulls) the micro-component in a vertical direction orthogonal to the surface.
In some embodiments, the force provided by the stamp places at least a portion of the tether under tension in the horizontal direction. In some embodiments, the force in the horizontal direction is a rotation. The force in the horizontal direction can be in a direction in which the tether extends from the anchor to the micro-component. The force in the horizontal direction can be orthogonal to a direction from the anchor to the micro-component. The force in the horizontal direction can be in a direction from the anchor to the micro-component and orthogonal to a direction from the anchor to the micro-component. The force in the horizontal direction can be one or more or any combination of (i) a force in a direction orthogonal to a direction from the anchor to the micro-component, (ii) a force in a direction from the anchor to the micro-component, and (iii) a rotational force about a vertical axis extending in the vertical direction.
According to embodiments of the present disclosure, a method of micro-transfer printing comprises providing a micro-component source wafer comprising a micro-component disposed over a cavity in a surface of the micro-component source wafer and connected to the micro-component source wafer and detaching the micro-component from the micro-component source wafer by moving the micro-component at least in a horizontal direction parallel to the surface. In embodiments, the micro-component is connected to the micro component source wafer with a tether and detaching the micro-component from the micro-component source wafer fractures or separates the tether.
Embodiments of the present disclosure provide improvements in picking printing micro-components from micro-component source wafers to micro-transfer print the micro-components.
Drawings are presented herein for illustration purposes, not for limitation. Drawings are not necessarily drawn to scale. The foregoing and other objects, aspects, features, and advantages of the disclosure will become more apparent and may be better understood by referring to the following description taken in conjunction with the accompanying drawings, in which:
Certain embodiments of the present disclosure provide, inter alia, devices, structures, systems, and construction methods for micro-assembling micro-components, such as micro-electronic components, micro-optical components, micro-photonic components, micro-silicon components, and micro-compound semiconductor components using a stamp-based micro-transfer printing process. Such micro-assembled micro-components and systems and structures comprising them are widely useful in electronic and photonic systems.
According to embodiments of the present disclosure and as illustrated in
Micro-component source wafer 10 can be any substrate or wafer on which the structure of
A shown in
Stamp 30 can be controlled by a micro-transfer printer comprising a motion-control platform with optical alignment capabilities. As shown in
In both
As shown in the cross sections of
According to embodiments of the present disclosure, in addition to moving stamp 30 and adhered micro-component 20 away from micro-component source wafer 10 in vertical direction Z with a motion-control platform, as shown in
In some embodiments, the horizontal motion of stamp 30 occurs at the same time as vertical motion in direction Z. In some embodiments, the horizontal motion of stamp 30 occurs before vertical motion in direction Z. In some embodiments, the horizontal motion of stamp 30 occurs after vertical motion in direction Z. In some embodiments, stamp 30 is moved in one or more and in any order or combination of vertical and horizontal movements at the same or alternating times. The vertical direction Z can be toward micro-component source wafer 10 or away from micro-component source wafer 10. Micro-component 20 can be detached (e.g., tether 22 can be fractured or separated) from micro-component source wafer 10 with any one or combination of horizontal and vertical movements by stamp 30, including moving stamp 30 in only a horizontal direction. By moving stamp 30 with the motion-control platform, stamp 20 presses (e.g., forces or pushes or pulls) micro-component 20 adhered to stamp post 34, causing micro-component 20 to move, thereby fracturing or separating tether 22 and detaching micro-component 20 from anchor 12 and micro-component source wafer 10. Micro-component 20 is then removed from micro-component source wafer 10 with a stamp 30 vertical motion away from micro-component source wafer 10 and can move horizontally to a target substrate to print micro-component 20 on the target substrate.
In embodiments of the present disclosure, the horizontal movement of stamp 30 can be any one or combination of movements in directions X, Y, and R and can result in stress to tether 22 to more readily fracture tether 22 and enable micro-component 20 removal from micro-component source wafer 10. The stress can be additional to any stress provided by a simultaneous movement in vertical direction Z. As shown in
In all of
As shown further in
Micro-component 20 can, for example, have a thickness no greater than 250 μm (e.g., no greater than 200 μm, no greater than 150 μm, no greater than 100 μm, no greater than 75 μm, no greater than 50 μm, no greater than 25 μm, no greater than 10 μm, no greater than 5 μm, no greater than 3 μm, or no greater than 2 μm). Similarly, micro-component 20 can have an area no greater than 100,000 μm2 (e.g., no greater than 62,500 μm2, less than 62,500 μm2, no greater than 40,000 μm2, less than 40,000 μm2, no greater than 20,000 μm2, no greater than 10,000 μm2, no greater than 2,500 μm2, no greater than 400 μm2, no greater than 100 μm2, no greater than 50 μm2, or no greater than 20 μm2). Micro-component 20 can have a width of no greater than 100 μm, 50 μm, 20 μm, or 10 μm and a length of no greater than 10 μm, 20 μm, 50 μm, 100 μm, 200 μm, 250 μm, or 500 μm. Micro-component 10 can have a width and a length both no greater than 500 μm, 250 μm, 100 μm, 50 μm, 20 μm, 10 μm, or 5 μm. Micro-component 20 can be substantially square or rectangular or can have a large aspect ratio (length to width), for example no less than 2:1, no less than 4:1, no less than 5:1, no less than 8:1, or no less than 10:1.
In some embodiments, micro-component 20 is attached to micro-component source wafer 10 with multiple tethers 22, each tether 22 connected to an anchor 12.
As used herein, a device (e.g., micro-component 20) native to a substrate (e.g., micro-component source wafer 10) is formed on the substrate, for example by photolithographically processing and patterning layers of material that were directly deposited on the substrate, for example by sputtering or vapor deposition. A device (e.g., micro-component 20) formed on a native substrate (e.g., micro-component source wafer 10) and then transferred to a second substrate (e.g., a target substrate) is non-native to the second substrate.
Examples of micro-transfer printing processes suitable for printing components onto target substrates are described in U.S. Pat. No. 8,722,458 entitled Optical Systems Fabricated by Printing-Based Assembly, U.S. Pat. No. 9,362,113 entitled Engineered Substrates for Semiconductor Epitaxy and Methods of Fabricating the Same, U.S. Pat. No. 9,358,775 entitled Apparatus and Methods for Micro-Transfer-Printing, U.S. patent application Ser. No. 14/822,868, filed on Aug. 10, 2015, entitled Compound Micro-Assembly Strategies and Devices, and U.S. Pat. No. 9,704,821 entitled Stamp with Structured Posts, each of which is hereby incorporated by reference herein in its entirety.
The terms horizontal and vertical are arbitrary labels and can be exchanged. Similarly, the terms x direction, y direction, and z direction are arbitrarily labeled and can be exchanged. A horizontal direction X can be exchanged with a horizontal direction Y.
It is contemplated that systems, devices, methods, and processes of the disclosure encompass variations and adaptations developed using information from the embodiments described herein. Adaptation and/or modification of the systems, devices, methods, and processes described herein may be performed by those of ordinary skill in the relevant art.
Throughout the description, where articles, devices, and systems are described as having, including, or comprising specific components, or where processes and methods are described as having, including, or comprising specific steps, it is contemplated that, additionally, there are articles, devices, and systems according to certain embodiments of the present disclosure that consist essentially of, or consist of, the recited components, and that there are processes and methods according to certain embodiments of the present disclosure that consist essentially of, or consist of, the recited processing steps.
It should be understood that the order of steps or order for performing certain actions is immaterial so long as operability is not lost. Moreover, two or more steps or actions may be conducted simultaneously.
Certain embodiments of the present disclosure were described above. It is, however, expressly noted that the present disclosure is not limited to those embodiments, but rather the intention is that additions and modifications to what was expressly described in the present disclosure are also included within the scope of the disclosure. Moreover, it is to be understood that the features of the various embodiments described in the present disclosure were not mutually exclusive and can exist in various combinations and permutations, even if such combinations or permutations were not made express, without departing from the spirit and scope of the disclosure. Having described certain implementations of heterogeneous wafer structures, heterogeneous semiconductor structures, methods of their fabrication, and methods of their use, it will now become apparent to one of skill in the art that other implementations incorporating the concepts of the disclosure may be used. Therefore, the disclosure should not be limited to certain implementations, but rather should be limited only by the spirit and scope of the following claims.
