Microdisplay device and method of manufacturing the same

Abstract

The present application relates to a kind of micro display device and its manufacturing method, is pre-embedded bonding metal pad on one of light-emitting chip or driving chip, and is connected between bonding metal pad to bonding surface by metal lead, after the bonding of light-emitting chip and driving chip, the material of the back of bonding metal pad is removed, so as to be exposed to the outside of chip, forms bonding pad.This kind of combination process can improve the integration of driving chip, reduce chip area, improve yield, reduce the effect of cost.

Description

Technical Field

[0001] This invention belongs to the field of micro-display technology, and specifically relates to a micro-display device and its manufacturing method. Background Technology

[0002] The rapid development of the VR / AR (Virtual Reality / Augmented Reality) industry has led to a period of rapid growth in displays suitable for VR / AR. Given that VR / AR systems are currently mostly implemented using head-mounted devices, the displays suitable for these devices must be microdisplay chips, typically with a diagonal size of less than 1 inch, mostly between 0.6 and 0.7 inches. Current microdisplay devices are primarily used to generate high-brightness miniature images, which are projected through optical systems for perception by the observer. The projection target can be the retina (virtual image) or a projection screen (real image). Traditional microdisplays are not used for direct visual observation; their pixel size is very small, and the pixel density (Pixel per Inch) is very high. Traditional micro-display technologies include LCoS (Liquid Crystal on Silicon) and DLP (Digital Light Processing), while emerging technologies mainly include Micro-LED. The principle is to use high-precision pattern exposure, development and etching to etch LED epitaxial wafers into individual pixels (this process and product is called MESA). The size of pixels is usually in the micrometer range (0.1-50 μm).

[0003] Microdisplay chips are composed of LED light-emitting chips and driver chips bonded together. However, after the LED light-emitting chips and driver chips are bonded, they still need to be electrically interconnected with external circuits. Typical electrical interconnection methods often require a large chip area, and the bonding pads are designed in the area of ​​the driver chip that extends beyond the light-emitting chips, which is also the non-light-emitting area of ​​the microdisplay device. (See [reference needed]). Figure 1 , 2 This leads to a decrease in chip integration, and the high precision requirements for bonding pads and light-emitting chips due to limitations in subsequent bonding process capabilities, resulting in greater process difficulty. This further leads to a decrease in the cutting rate of the driver chip on the wafer, resulting in a decrease in chip yield and an increase in the cost of a single chip. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a microdisplay device with smaller chip area, higher integration, and lower cost, as well as a manufacturing method thereof.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a micro-display device, comprising a first chip and a second chip bonded together, wherein one of the first chip and the second chip is a light-emitting chip and the other is a driving chip, the light-emitting chip has a plurality of LED light-emitting units, the driving chip includes a substrate and a driving circuit for providing driving signals to the LED light-emitting units, the first chip has a plurality of bonding metal pads pre-embedded therein, the second chip has a plurality of metal electrodes on its bonding surface, one side of each of the bonding metal pads is electrically interconnected with the plurality of metal electrodes through metal leads, and the other side of each of the bonding metal pads is exposed on the surface of the first chip to form a plurality of bonding pads.

[0006] In one embodiment of this application, the first chip is a light-emitting chip, and the second chip is a driver chip.

[0007] In one embodiment of this application, the light-emitting chip has a display area and a non-display area, the non-display area being distributed around the display area, and a plurality of bonding pads being distributed within the non-display area of ​​the light-emitting chip.

[0008] In one embodiment of this application, the bonding pad is located on the light-emitting surface side of the light-emitting chip.

[0009] In one embodiment of this application, the first chip and the second chip have the same area and shape, such that the first chip covers all the metal electrodes on the second chip.

[0010] In one embodiment of this application, the first chip and the second chip may have different area sizes and shapes.

[0011] In one embodiment of this application, to further increase the light-emitting area, the area of ​​the light-emitting chip is larger than the area of ​​the driving chip.

[0012] Another technical solution of the present invention is to provide a method for manufacturing the above-mentioned microdisplay device: a method for manufacturing a microdisplay device, comprising the following steps:

[0013] S1. A first substrate is provided, the first substrate having a first substrate and a first device layer formed on the front side of the first substrate;

[0014] S2. Etch deep pits on the first device layer;

[0015] S3. Embed bonding metal pads in the deep pit;

[0016] S4. Form an insulating dielectric layer, etch the insulating dielectric layer to form a trench communicating with the bonding metal pad, and fill the trench with metal to form a metal lead connecting the front side of the bonding metal pad.

[0017] S5. A second substrate is provided, the second substrate having a second substrate, a second device layer formed on the second substrate, and a plurality of metal electrodes;

[0018] S6. Bond the first substrate to the second substrate so that the plurality of metal electrodes are electrically interconnected with the metal leads respectively;

[0019] S7. Remove the first substrate;

[0020] S8. Remove a portion of the material on the back side of the first substrate to expose the back side of the bonding metal pad, forming a bonding pad;

[0021] In this embodiment, one of the first device layer and the second device layer is pre-processed with a plurality of LED light-emitting units, and the other of the first device layer and the second device layer is pre-processed with a driving circuit.

[0022] In one embodiment of this application, step S6 employs one of Die-Die bonding, Die-Wafer bonding, or Wafer-Wafer bonding.

[0023] In one embodiment of this application, the first substrate is a light-emitting chip, the second substrate is a driver chip, and the package pins are formed in the non-display area of ​​the light-emitting chip.

[0024] In one embodiment of this application, the first substrate and the second substrate have the same area and shape.

[0025] Compared with the prior art, the present invention achieves the following beneficial effects: by pre-embedding bonding pad metal on the light-emitting chip or the driver chip, and then interconnecting the bonding pad on the light-emitting chip with the driver chip through chip bonding process, the integration of the driver chip is improved, the chip area is reduced, the yield is increased, and the cost is reduced. Attached Figure Description

[0026] Appendix Figure 1 A wafer containing several microdisplay devices;

[0027] Appendix Figure 2 A top view of the micro-display device before its improvement;

[0028] Appendix Figure 3 A side view of the micro-display device before improvement;

[0029] Appendix Figure 4 This is a top view of the microdisplay device of this application;

[0030] Appendix Figure 5 This is a side view of the micro-display device of this application;

[0031] Appendix Figure 6-10 This is a schematic diagram of the manufacturing process of the micro-display device of this application;

[0032] Wherein: 100, microdisplay device; 101, light-emitting chip; 102, driver chip;

[0033] 10. First chip; 11. First substrate; 12. First device layer; 121. First layer; 122. Second layer; 13. Deep pit; 14. Bonding metal pad; 15. Metal lead; 16. Insulating dielectric layer; 17. Dielectric layer; 20. Second chip; 21. Second substrate; 22. Second device layer; 23. Metal electrode; 30. Bonding pad. Detailed Implementation

[0034] To explain in detail the technical content, structural features, achieved objectives, and effects of the invention, the following will provide a detailed description in conjunction with embodiments and accompanying drawings. The positional relationships of "upper" and "lower" as described in this specification are respectively related to those in the accompanying drawings. Figure 6 The top and bottom correspond to each other.

[0035] This application discloses a microdisplay device 100, comprising a first chip 10 and a second chip 20 bonded together. It is used in wearable devices such as AR, VR, HUD, and watches, or in electronic devices such as displays. One of the first chip 10 and the second chip 20 is a light-emitting chip, and the other is a driving chip. The light-emitting chip can be one of semiconductor light-emitting devices such as Micro-LED, Mini-LED, or OLED. The driving chip can be a driving circuit such as CMOS or TFT.

[0036] This application involves pre-embedding a bonding metal pad on one of the light-emitting chips or the driver chip, and connecting the bonding metal pad to the bonding surface through metal leads. After the light-emitting chip and the driver chip are bonded, the material on the back of the bonding metal pad is removed, exposing it to the outside of the chip, thus forming the bonding pad.

[0037] The following section will use the formation of bonding pads on a light-emitting chip as an example to provide a detailed description of this application.

[0038] See appendix Figure 10The microdisplay device 100 of this application includes a first chip 10 and a second chip 20 bonded together. The first chip 10 is a Micro-LED light-emitting chip, and the second chip 20 is a driver chip. The light-emitting chip has a plurality of LED light-emitting units (not shown in the figure), and the driver chip includes a substrate and a driver circuit that provides driving signals to each of the aforementioned LED light-emitting units. Based on the inventive spirit of this application, it is readily understood that, as a variation of this application, the first chip can also be used as a driver chip, and the second chip as a light-emitting chip.

[0039] The first chip 10 has a first device layer 12, in which a plurality of bonding metal pads 14 are embedded. The front side of the bonding metal pads 14 is connected to the bonding surface of the first chip 10 by metal leads 15, while the back side of the bonding metal pads 14 is exposed or partially exposed on the surface of the first chip, forming a plurality of bonding pads 30 for connection with external circuits.

[0040] The second chip 20 has a second substrate 21 and a second device layer 22 formed on the second substrate 21. The second device layer 22 has a plurality of metal electrodes 23 electrically connected to the driving circuit. These metal electrodes 23 form pads on the bonding surface of the second chip that are electrically connected to the metal leads 15 on the first chip 10.

[0041] For a light-emitting chip, there are display areas and non-display areas. See also Figure 4 and Figure 5 As shown, in this embodiment, the first chip 10 is a light-emitting chip, and the second chip 20 is a driving chip. The aforementioned bonding pads 30 are distributed in the non-display area of ​​the light-emitting chip, and the non-display area is located on the periphery of the display area. In particular, the multiple bonding pads 30 are arranged in two rows on both sides of the display area.

[0042] In one embodiment, the bonding pad 30 is disposed on the light-emitting surface side of the light-emitting chip. In other embodiments, the bonding pad 30 may also be located on the non-light-emitting surface side of the light-emitting chip.

[0043] In a preferred embodiment of this application, the first chip 10 and the second chip 20 have the same area and shape, meaning that the first chip 10 can cover all the metal electrodes on the second chip 20. The advantage of this structure is that the light-emitting area of ​​the first chip can be increased, improving the integration density of the driver chip. It is estimated that this can reduce the chip area by 5%, improve the yield by 6-7%, and reduce the overall cost by approximately 10%.

[0044] In other embodiments of this application, the first chip 10 and the second chip 20 may have different sizes or shapes, as long as the bonding pads of the two chips correspond one-to-one and an electrical connection can be formed. To obtain a larger display area, the area of ​​the light-emitting chip can be increased to be larger than that of the driving chip, thereby achieving a better display effect.

[0045] This application further discloses a method for manufacturing the above-mentioned microdisplay device, which includes the following steps:

[0046] S1. As Figure 6 As shown, a first substrate is provided, the first substrate having a first substrate 11 and a first device layer 12 formed on the front side of the first substrate 11, the first device layer 12 including a first layer 121 and a second layer 122.

[0047] S2. Etch deep pits 13 on the first device layer 12;

[0048] S3. See also Figure 7 Bonding pad metal is pre-embedded in the deep pit 13 to form a bonding metal pad 14. The area of ​​the bonding metal pad 14 is smaller than the area of ​​the bottom of the deep pit 13, that is, there is a gap between the bonding metal pad 14 and the edge of the deep pit 13.

[0049] S4. See also Figure 8 The first substrate is planarized, and an insulating dielectric layer 16 is formed on the first device layer 12. The insulating dielectric layer 16 is etched to form a trench that communicates with the bonding pad metal. The trench is filled with metal to form a metal lead 15 that connects to the front side of the bonding metal pad 14. The bonding metal pad 14 and the metal lead 15 are wrapped by the insulating dielectric layer 16 and are insulated from other devices in the first device layer 12.

[0050] S5. A second substrate is provided, the second substrate having a second substrate 21, a second device layer 22 formed on the second substrate 21, and a plurality of metal electrodes 23;

[0051] S6. Bond the first substrate to the second substrate, such that a plurality of metal electrodes 23 on the second substrate are electrically interconnected with metal leads 15 on the first substrate. See [link to documentation]. Figure 9 ;

[0052] S7. Remove the first substrate 11 and form a protective dielectric layer 17 on the back side of the first substrate 11;

[0053] S8. Remove a portion of the material from the back side of the first substrate to expose the back side of the bonding metal pad 14, forming the encapsulation bonding pad 30, as shown. Figure 10 As shown.

[0054] As mentioned above, in the embodiments of this application, the bonding metal pads can be pre-embedded on the light-emitting chip or on the driver chip. In the specific solution provided in this embodiment, the first device layer 12 has a plurality of LED light-emitting units, and the second device layer 22 is fabricated with a driver circuit. The first substrate is the light-emitting chip, the second substrate is the driver chip, and the bonding pads 30 are formed in the non-display area of ​​the light-emitting chip.

[0055] In one embodiment, step S3 further includes film formation, photolithography, and etching processes to ultimately achieve the pre-embedding of bonding pad metal in the deep pit 13.

[0056] In a preferred embodiment, the light-emitting chip and the driving chip have identical area and shape, and their combination forms an aesthetically pleasing and neat shape. In other embodiments, to further increase the light-emitting area, the light-emitting chip may be made slightly larger than the driving chip.

[0057] In step S6, the bonding between the first substrate and the second substrate can be any one of Die-Die bonding, Die-Wafer bonding, or Wafer-Wafer bonding. Die-Die refers to chip-to-chip bonding, Die-Wafer bonding refers to chip-to-wafer bonding, and Wafer-Wafer refers to wafer-to-wafer bonding.

[0058] In step S8, the back side of the bonding pad metal is exposed through back side thinning, polishing, photolithography and etching processes on the back side of the first substrate.

[0059] After the bonding pad 30 is formed, the micro-display device can be electrically interconnected with the outside world through bonding processes such as wire bond or flip chip.

[0060] Calculations show that this application can improve the integration of driver chips, reduce chip area by about 5%, increase yield by 6-7%, and reduce overall cost by about 10%.

[0061] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope. The scope of protection of the present invention is defined by the appended claims, specification, and their equivalents.

Claims

1. A method for manufacturing a micro-display device, characterized in that, Includes the following steps: S1. A first substrate is provided, the first substrate having a first substrate and a first device layer formed on the front side of the first substrate; S2. Etch deep pits on the first device layer; S3. Embed bonding metal pads in the deep pit; S4. An insulating dielectric layer is formed on the front side of the first substrate, the insulating dielectric layer is etched to form a trench communicating with the bonding metal pad, and metal is filled in the trench to form a metal lead connecting the front side of the bonding metal pad. S5. A second substrate is provided, the second substrate having a second substrate, a second device layer formed on the second substrate, and a plurality of metal electrodes; S6. Bond the first substrate to the second substrate so that the plurality of metal electrodes are electrically interconnected with the metal leads respectively; S7. Remove the first substrate; S8. Remove part of the first device layer and bonding metal pad on the back side of the first substrate, so that the back side of the bonding metal pad is exposed and a pit is formed to form a bonding pad, wherein the bonding pad is located on one side of the light-emitting surface. In this embodiment, one of the first device layer and the second device layer is pre-processed with a plurality of LED light-emitting units, and the other of the first device layer and the second device layer is pre-processed with a driving circuit.

2. The manufacturing method according to claim 1, characterized in that: In step S6, one of Die-Die bonding, Die-Wafer bonding, or Wafer-Wafer bonding is used.

3. The manufacturing method according to claim 1, characterized in that: The first substrate is a light-emitting chip, the second substrate is a driving chip, and the bonding pad is formed in the non-display area of ​​the light-emitting chip.

4. The manufacturing method according to claim 1, characterized in that: The first substrate and the second substrate have the same area and shape.

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