Alignment process for transfer settings
By using an electrical alignment process on a large-area substrate to measure and adjust the alignment value between the substrates, the problem of complex alignment process in the prior art is solved, and a more efficient and accurate alignment effect is achieved.
Patent Information
- Application Number
- CN202510047961.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2019-11-05
- Filing Date
- 2020-05-22
- Publication Date
- 2025-04-25
AI Technical Summary
When performing the alignment process on a large-area substrate, the prior art is difficult to effectively solve the problem that the technology used in small substrates cannot be directly transferred, resulting in the complexity of the alignment process.
Using an electrical alignment process, the alignment is achieved by measuring the alignment value between the alignment marks between the first substrate and the second substrate, and adjusting the substrate position to maximize, minimize, or equalize the alignment value.
This method can replace or enhance conventional optical alignment processes, improve the accuracy and efficiency of alignment, and is suitable for alignment tasks for large-area substrates.
Smart Images
Figure CN119890120A_ABST
Abstract
Description
[0001] This application is a divisional application of the invention patent application with application date of May 22, 2022, application number 202080036397.3, and invention name “Alignment process for transfer setting”.
[0002] CROSS REFERENCE TO RELATED APPLICATIONS
[0003] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62 / 930,982, filed on November 5, 2019, and U.S. Provisional Patent Application No. 62 / 851,189, filed on May 22, 2019, each of which is incorporated herein by reference in its entirety. Technical Field
[0004] The present invention relates to an alignment process between a first substrate and a second substrate. In particular, the present invention relates to an electrical alignment process combined with optical alignment between substrates. Background Art
[0005] Typically, many micro devices, including light emitting diodes (LEDs), organic LEDs (OLEDs), sensors, solid-state devices, integrated circuits, micro-electromechanical systems (MEMS), and other electronic components, are often fabricated in batches on flat substrates. To form an operational system, micro devices from at least one donor substrate need to be selectively aligned and bonded to a receiver substrate. Various alignment techniques, including optical alignment, can be employed for the wafer to be aligned.
[0006] The challenges of alignment on large area substrates are more complex because some of the techniques used in small substrates cannot be directly transferred to such applications. Summary of the invention
[0007] It is an object of the present invention to overcome the disadvantages of the prior art and to replace or enhance the conventional optical alignment process.
[0008] According to one embodiment, an electrical alignment process for aligning a first (or temporary) substrate with a second substrate may be provided. The method may include: positioning a first substrate having at least a first alignment mark in close proximity to a second substrate having at least a second alignment mark, measuring alignment values between the first alignment mark and the second alignment mark of both the first substrate and the second substrate; and adjusting the positions of the first substrate and the second substrate based on the measured alignment values.
[0009] In one case, the substrate may be a backplane, an intermediate substrate, a donor substrate, a mask, or other forms of substrates. In the present invention, for example, the first substrate may include a donor substrate and the second substrate may include a receiver substrate.
[0010] In one case, the alignment mark on the donor substrate and the alignment mark on the receiver substrate facilitate measurement of alignment values.The positions of the two substrates can be adjusted to maximize, minimize, or equalize the alignment value of each alignment mark.
[0011] In one embodiment, the alignment marks may be plates that form a capacitor when brought close together. In this case, the alignment value (or inductance) between the alignment plate on the donor substrate and the alignment plate on the receiver substrate is maximized. In another case, either substrate may be moved to maximize the capacitance (or other value) between the plates.
[0012] In another embodiment, the alignment marks may be charges trapped on the surface of one substrate and plates on the surface of another substrate.
[0013] In some embodiments, the alignment marks may be electrical signals on one surface of one substrate and receivers on the surface of another substrate.
[0014] In yet another embodiment, the alignment mark can be a shield plate on one substrate and a receiver plate on the other substrate. The shield plate blocks the signal from the source from reaching the receiver substrate. The shield plate acts as an alignment mark on one of the substrates, blocking between the source and the collector plate on the other substrate. In this case, the alignment value can be minimized to align the two substrates.
[0015] In another case, the values are equalized between several alignments of corresponding alignment marks between the donor substrate and the receiver substrate.
[0016] In one embodiment, the plate may be a conductive or charged layer. In another embodiment, there may be multiple plates forming alignment marks in different orientations.
[0017] In one embodiment, there may be multiple (e.g., four) plates on one substrate and at least one plate on another substrate. In one case, the values (e.g., capacitance or charge readings) of the multiple plates and the at least one plate on the other substrate are equalized by moving either substrate.
[0018] In another case, the values between multiple alignment marks (or different segments of a single alignment mark) are equalized.
[0019] In one embodiment, the electrical alignment mark may also be used as an initial optical alignment mark.
[0020] The foregoing and additional aspects and embodiments of the present invention will be apparent to those skilled in the art in view of the detailed description of various embodiments and / or aspects with reference to the drawings, a brief description of which is provided below. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The foregoing and other advantages of the present invention will become immediately apparent after reading the following detailed description and after referring to the accompanying drawings.
[0022] Figure 1A A series of steps are shown for a process of aligning two wafers according to an embodiment of the present invention.
[0023] Figure 1B A perspective view showing an exemplary alignment process according to an embodiment of the invention.
[0024] Figure 2A A perspective view showing an exemplary alignment process according to an embodiment of the invention.
[0025] Figure 2B A perspective view showing an exemplary alignment process according to an embodiment of the invention.
[0026] Figure 3A Shown are the detector and source signals on one substrate and the transfer medium on the other substrate.
[0027] Figure 3B Shown are two detectors and source signals on one substrate and a transfer medium on the other substrate.
[0028] The use of the same reference numbers in different drawings indicates similar or identical elements.
[0029] Although the present invention is susceptible to various modifications and alternative forms, specific embodiments or implementations have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the present invention is not intended to be limited to the particular form disclosed. Rather, the present invention encompasses all modifications, equivalent forms, and alternatives that fall within the spirit of the present invention as defined by the appended claims. DETAILED DESCRIPTION
[0030] Although the present teachings are described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to these embodiments. On the contrary, the present teachings encompass various alternatives and equivalent forms, as will be appreciated by those skilled in the art.
[0031] In LED display applications where the display pixel is a single device LED, each LED is bonded to a drive circuit that controls the current flowing into the LED device. Here, the drive circuit can be a thin film transistor (TFT) backplane, a system substrate, or a display wafer conventionally used in LCD or OLED display panels. Due to the typical pixel size (10μm to 50μm), bonding can be performed at the wafer level. In this scheme, the LED wafer consists of isolated individual LED devices that are transferred and aligned and bonded to a backplane or display wafer that is compatible with the LED wafer pixel size and pitch. Various alignment techniques, including conventional optical alignment, can be used for the wafer to be aligned.
[0032] The present invention provides an electrical alignment process to replace or enhance conventional optical alignment processes. The electrical alignment process measurement of the present invention is completed by measuring the alignment value between substrates. The alignment value may include a capacitance value, an inductance value, a charge value, or another electrical signal value between the substrates. In this case, alignment marks on the donor substrate and alignment marks on the receiver substrate can facilitate the measurement of the alignment value. The substrate can be a backplane, an intermediate substrate, a donor substrate, a mask, or other forms of substrates.
[0033] Figure 1A A series of steps of an alignment process between a first substrate and a second substrate according to an embodiment of the present invention are shown. In one example, the first substrate may be a display substrate / receiver substrate and the second substrate may include a cassette / donor wafer or mask. Method 100 includes steps that may be completed in any particular order to achieve a desired state. Here, a first substrate (e.g., a receiver substrate) and a second substrate (e.g., a donor substrate) may be provided. In step 102, in an initial step of aligning the substrates, an alignment means (e.g., optical) may be used to roughly align the donor substrate with the receiver substrate. In the next step 104, electrical or magnetic alignment using electrical signals / parameters (or magnetic signals) may be used for fine alignment. The alignment may be achieved by maximizing an alignment value (e.g., capacitance) that may be an electrical signal, or minimizing an electrical signal (e.g., by shielding a signal generated by a source) or balancing electrical signals (e.g., in the case where multiple detectors measure alignment signals associated with multiple alignment marks or different portions of an alignment mark). In another case, the alignment value may be a magnetic signal. Here, the alignment may be achieved by maximizing the magnetic signal (e.g., inductance) or minimizing the magnetic signal (e.g., by shielding the magnetic signal from the source) or balancing the magnetic signal (e.g., multiple magnetic sources or detectors). Thus, there may be different types of alignment marks, as follows
[0034] 1) Forming an alignment mark of an electric or magnetic component (such as a capacitor or inductor component). In this case, the absolute value of the signal at each moment is measured as an alignment value.
[0035] 2) Alignment marks for shielding electrical signals. In this case, the effect of the shielding at each moment is measured as an alignment value.
[0036] Multiples of each alignment mark may be used to enhance the alignment process.
[0037] Figure 1B A perspective view of an exemplary alignment process according to an embodiment of the present invention is shown. Here, a first substrate 120 and a second substrate 110 may be provided. There are alignment marks (110-a, 120-a) provided on the substrates. In this case, the first substrate has an alignment mark 120-a and the second substrate has an alignment mark 120-a, which facilitates the measurement of the alignment value.
[0038] Alignment process
[0039] For faster and more accurate alignment, several alignment marks (electrical / magnetic components or electric / magnetic shields) as described previously may be used across two substrates to more quickly obtain alignment values associated with these alignment marks. Alignment may be accomplished based on an absolute alignment value associated with each alignment mark or a rate of change of alignment value.
[0040] In one scenario, the substrates are moved relative to each other in different directions (e.g., up, down, left, right), and the effect of the movement on each alignment value associated with different alignment marks across the substrates is then measured. Based on this, the positions of the two substrates can be adjusted to maximize, minimize, or equalize the alignment value of each alignment mark based on the type of alignment mark. This process can be repeated to achieve an alignment value change that is less than a threshold.
[0041] In another case, the alignment value of each alignment mark can be extracted at the current position of the two substrates relative to each other. Based on the value, the misalignment is calculated, and the substrate is positioned based on the calculated misalignment value. This process can be repeated to achieve an alignment value change that is less than a threshold.
[0042] Alignment mark
[0043] In one embodiment, different alignment marks may be used in the above method.
[0044] In one case, the alignment marks on the donor and receiver substrates can be metal plates that form a capacitor when brought close together. Since the capacitance is dominated by the overlap area between the two plates, misalignment between the plates will affect the capacitance value that can be extracted as the alignment value.
[0045] In another case, the alignment mark may include trapped charges on the surface of one substrate (e.g., the donor substrate) or a magnetic material on one of the substrates. The charge (or magnetic field) may be read by an electrode on the other substrate. The electrode may be a plate on the surface of the other substrate (e.g., the receiver substrate). The effect of the charge on the electrode varies with the overlap area. Thus, the detected charge effect may be used as an alignment value. In this case, the alignment value between the alignment plate on the donor substrate and the alignment plate on the receiver substrate is maximized.
[0046] In one embodiment, the alignment marks may be electrical signals on one surface and receivers on the other surface.
[0047] In another embodiment, the alignment mark can be a shield plate on one substrate and a receiver plate on the other substrate. The shield plate blocks the signal from the source from reaching the receiver substrate. The shield plate acts as an alignment mark on one of the substrates, blocking between the source and the collector plate on the other substrate. In this case, the alignment value can be minimized to align the two substrates.
[0048] Figure 2A A perspective view of an exemplary alignment process for an LED transfer machine according to an embodiment of the invention is shown.Here, a donor substrate and a receiver substrate may be placed on a donor alignment plate 202 and a receiver alignment plate 204, respectively.
[0049] In one case, the plates 202, 204 may be metal plates. These metal plates may be brought close together to form a capacitor. These metal plates may be moved to maximize the capacitance (or other electrical value) between the two plates. Initially, the plates may be optically aligned. Since the capacitance is primarily governed by the overlap area between the two plates, misalignment between the plates will affect the capacitance value that can be extracted as an alignment value. In the case of low capacitance values, the position of the plates may be shifted to maximize the value.
[0050] In one embodiment, the plates 202, 204 may be conductive or charge layers. In another embodiment, there may be multiple plates with alignment marks formed in different orientations.
[0051] Figure 2B A perspective view showing an exemplary alignment process according to an embodiment of the invention.
[0052] In one embodiment, there may be multiple (e.g., four) plates (204-1, 204-2, 204-3, and 204-4) on one substrate and at least one plate 202-b on another substrate. In one case, the values (e.g., capacitance or charge readings) of the multiple plates and the at least one plate on the other substrate are equalized by moving either substrate.
[0053] According to one embodiment, a method of aligning a first substrate with a second substrate may be provided. The method may include: positioning a first substrate having at least a first alignment mark in close proximity to a second substrate having at least a second alignment mark, measuring an alignment value between the first alignment mark and the second alignment mark of both the first substrate and the second substrate; and adjusting the positions of the first substrate and the second substrate based on the measured alignment value.
[0054] According to another embodiment, measuring alignment values between alignment marks of both the first substrate and the second substrate may include: extracting alignment values at current positions of the substrates; and moving the substrates relative to each other in different directions to measure changes in alignment values.
[0055] According to some embodiments, the method may further include: comparing the alignment value with the change in the alignment value; and adjusting the positions of the first substrate and the second substrate based on the comparison. Adjusting the change in the alignment value may include one of the following: maximizing, minimizing, or equalizing the alignment value of each alignment mark.
[0056] According to yet another embodiment, at least one alignment mark on the first substrate and the second substrate may include a metal plate or a capacitive plate. The alignment value between the capacitive plates may be maximized. At least one alignment mark on the first substrate may include charges trapped on the surface of the first substrate, and at least one alignment mark on the second substrate may include a plate on the surface of the second substrate. At least one alignment mark on the first substrate may include a shielding plate on the surface of the first substrate, and at least one alignment mark on the second substrate may include a receiver plate on the second substrate. The alignment value between the shielding plate and the receiver plate may be minimized.
[0057] According to some further embodiments, the at least one alignment mark on the first substrate may include a plurality of plates on the first substrate, and the at least one alignment mark on the second substrate may include a metal plate on the second substrate, and alignment values of the plurality of plates and the metal plate may be equalized by moving one of the first substrate or the second substrate. The alignment value may include one of the following: a capacitance value, an inductance value, a charge value, or another electrical signal value between the substrates.
[0058] In one embodiment, the detector and the signal source are located on one substrate and the transfer medium is formed on another substrate. Here, the signal is transferred from the source to the detector through the transfer medium. If the source and the detector are aligned with the transfer medium, the signal detected by the detector will be maximized. Figure 3AOne implementation of such a method is shown. Here, a substrate 310 has both a signal source 310-b and a detector 310-a. The media 320a, 320b are on another substrate 320. The transfer media can be conductive traces. Here, the combination of the signal, detector, and transfer media can be in different orientations to assist with different misalignment signals, such as offset and rotation.
[0059] Figure 3B Another embodiment demonstrated in has one signal source 310b and two detectors 310a, 310c for each group and has transfer media 320a, 320b and 320c. Here, one group includes at least one signal source and at least one detector on one substrate and a transfer medium on another substrate. Here, the signal is transferred to the transfer medium and directed to the two detectors. The signals received by the two detectors are balanced and maximized. Therefore, each group can provide both offset and rotational misalignment. More groups in different orientations can assist in fine tuning the misalignment information. This information can be used to align the substrate. The size of the transfer medium and / or the detector and the signal can be used to define the alignment accuracy. For example, if the transfer medium is larger than the detector or the signal, it can be used for rough alignment. If the size is the same, it can be used for fine alignment.
[0060] The foregoing description of one or more embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. The scope of the present invention is not intended to be limited by this detailed description, but rather by the appended claims.
Claims
1. A method for aligning a first substrate with a second substrate, comprising: positioning the first substrate having at least a first alignment mark in close proximity to the second substrate having at least a second alignment mark, wherein one or more of the at least first alignment mark or the second alignment mark shields a signal to generate an alignment value; measuring an alignment value between the first alignment mark and the second alignment mark of both the first substrate and the second substrate; and The positions of the first substrate and the second substrate are adjusted based on the measured alignment values.
2. A method for aligning a first substrate with a second substrate, comprising: positioning the first substrate having at least a first alignment mark in close proximity to the second substrate having at least a second alignment mark; measuring an alignment value between the first alignment mark and the second alignment mark of both the first substrate and the second substrate; and adjusting positions of the first substrate and the second substrate based on the measured alignment value, Wherein the at least first alignment mark on the first substrate comprises a shielding plate on a surface of the first substrate, and the at least one alignment mark on the second substrate comprises a receiver plate on the second substrate. The method of claim 2 , wherein the alignment value between the shield plate and the receiver plate is minimized.
4. A method for aligning a first substrate with a second substrate, comprising: positioning the first substrate having at least a first alignment mark in close proximity to the second substrate having at least a second alignment mark; measuring an alignment value between the first alignment mark and the second alignment mark of both the first substrate and the second substrate; and adjusting positions of the first substrate and the second substrate based on the measured alignment value, Wherein the at least one alignment mark on the first substrate comprises a plurality of plates on the first substrate, and the at least second alignment mark on the second substrate comprises a metal plate on the second substrate. 5 . The method of claim 4 , wherein the alignment values of a plurality of plates and the metal plate are equalized by moving one of the first substrate or the second substrate. 6 . The method of claim 4 , wherein the alignment value comprises one of: a capacitance value, an inductance value, a charge value, or another electrical signal value between the substrates.