KR-20260064409-A - VERTICAL STACKED MICRODISPLAY PANEL WITHOUT COLOR FILTER AND MANUFACTURING METHOD THEREOF

KR20260064409AKR 20260064409 AKR20260064409 AKR 20260064409AKR-20260064409-A

Abstract

The present invention relates to a vertically stacked microdisplay panel that does not require a color filter, comprising: a back wafer having a plurality of CMOS electrode pads aligned on its upper surface; a plurality of LED stacks each comprising a plurality of light-emitting parts and a plurality of bonding layers stacked in a vertical direction, each of which is aligned on the plurality of CMOS electrode pads; and a common electrode formed on the plurality of LED stacks, wherein each of the plurality of LED stacks has a short passage of a predetermined length formed therein to conduct current to the light-emitting parts, thereby emitting only a specific color. According to the present invention, even though a vertically stacked tandem structure is adopted, a color filter becomes unnecessary, so the color quality of the microdisplay can be significantly improved, and process complexity and productivity can be significantly improved. In addition, unlike conventional monolithic integration methods or hybrid methods that have alignment issues, by etching the stack on an engineering monolithic epitaxy wafer to separate it into preset units, a plurality of LED stacks are aligned on a plurality of CMOS electrode pads, thereby enabling the use of not only small-diameter wafers of 6 inches or less but also large-diameter wafers of 8 inches or more, which has the effect of significantly increasing the product yield.

Inventors

송준오
문지형
윤형선
김태경

Assignees

웨이브로드 주식회사

Dates

Publication Date: 20260507
Application Date: 20241202
Priority Date: 20241030

Claims (10)

A back wafer having a plurality of CMOS electrode pads aligned on its upper surface; A plurality of LED laminates each comprising a plurality of light-emitting parts stacked in a vertical direction and a plurality of bonding layers, and each aligned on a plurality of CMOS electrode pads; and It includes a common electrode formed on a plurality of the above-mentioned LED stacks, and Each of the plurality of the above LED stacks is, A vertically stacked microdisplay panel that does not require a color filter, wherein a short passage of a predetermined length is formed and current is passed through the light-emitting part to emit only a specific color.
In claim 1, A plurality of the above LED stacks, It includes a first LED stack for emitting only a first color, a second LED stack for emitting only a second color, and a third LED stack for emitting only a third color, Each of the above first LED laminate, the above second LED laminate, and the above third LED laminate is, A vertically stacked microdisplay panel that does not require a color filter, comprising a first light-emitting part disposed on the CMOS electrode pad and emitting the first color, a second light-emitting part disposed on the first light-emitting part and emitting the second color, and a third light-emitting part disposed on the second light-emitting part and emitting the third color.
In claim 2, The above-mentioned first LED laminate is, The short passage is formed to penetrate the third light-emitting part and the second light-emitting part so as not to inject current into the third light-emitting part and the second light-emitting part, and current is passed only to the first light-emitting part so as to emit only the first color. The above second LED laminate is, The short passage is formed to penetrate the first light-emitting part and the third light-emitting part, respectively, so that current is not injected into the first light-emitting part and the third light-emitting part, respectively, and current is passed only to the second light-emitting part, thereby emitting only the second color. The above third LED laminate is, A vertically stacked microdisplay panel that does not require a color filter, wherein the short passage is formed to penetrate the first light-emitting part and the second light-emitting part so as not to inject current into the first light-emitting part and the second light-emitting part, and current is passed only to the third light-emitting part to emit only the third color.
In claim 3, A plurality of the above LED stacks, A vertically stacked microdisplay panel that does not require a color filter, wherein a transparent layer electrically connected to the short passage is formed on the upper part of the first light-emitting part and the lower part of the third light-emitting part, respectively.
A preparation step of preparing a plurality of front wafers, a temporary wafer, and a back wafer having a plurality of CMOS electrode pads aligned on an upper surface, each including a support wafer and a light-emitting part and emitting a different color; A stacking step of vertically stacking a plurality of light-emitting parts and a bonding layer on a temporary wafer by repeating the process of bonding the front wafer onto the temporary wafer through a bonding layer and then removing the support wafer; A bonding step of bonding the temporary wafer, having a plurality of the light-emitting parts and the bonding layer stacked in a vertical direction, with the back wafer, and then removing the temporary wafer; An etching step in which a plurality of LED stacks are aligned on a plurality of CMOS electrode pads by etching a plurality of stacked light-emitting parts and a bonding layer to separate them into preset units; and It includes a forming step of forming a common electrode on a plurality of the above-mentioned LED stacks, and Each of the plurality of the above LED stacks is, A method for manufacturing a vertically stacked microdisplay panel that does not require a color filter, wherein a short passage of a predetermined length is formed and current is passed through the light-emitting part to emit only a specific color.
In claim 5, A plurality of the above-mentioned front wafers, A first front wafer comprising the support wafer and a first light-emitting part, a second front wafer comprising the support wafer and a second light-emitting part, and a third front wafer comprising the support wafer and a third light-emitting part, A plurality of the above LED stacks, A method for manufacturing a vertically stacked microdisplay panel that does not require a color filter, comprising a first LED stack for emitting only a first color, a second LED stack for emitting only a second color, and a third LED stack for emitting only a third color.
In claim 6, After the above stacking step, The method further includes a first processing step of forming a short passage to penetrate the first light-emitting part and the second light-emitting part in the portion where the third LED laminate is to be formed, and forming a short passage to penetrate the first light-emitting part in the portion where the second LED laminate is to be formed. After the above bonding step, A method for manufacturing a vertically stacked microdisplay panel that does not require a color filter, further comprising a second processing step of forming a short passage to penetrate the third light-emitting part and the second light-emitting part in a portion where the first LED stack is to be formed, and forming a short passage to penetrate the third light-emitting part in a portion where the second LED stack is to be formed.
In claim 7, The above first processing step is, A transparent layer electrically connected to the short passage is formed on the first light-emitting part, and The above second processing step is, A method for manufacturing a vertically stacked microdisplay panel that does not require a color filter, wherein a transparent layer electrically connected to the short passage is formed on the third light-emitting part.
In claim 5, The above stacking step is, A method for manufacturing a vertically stacked microdisplay panel that does not require a color filter, wherein a plurality of the light-emitting parts and the bonding layer are stacked vertically on the above temporary wafer, and then heat treatment is performed.
In claim 5, The above support wafer and the above temporary wafer are, A method for manufacturing a vertically stacked microdisplay panel that does not require a color filter, which is a silicon (Si) or sapphire wafer.

Description

Vertical stacked microdisplay panel without color filter and manufacturing method thereof The present invention relates to a vertically stacked microdisplay panel that does not require a color filter and a method for manufacturing the same. More specifically, it relates to a vertically stacked LEDoS microdisplay panel that does not require a color filter by using an engineering monolithic epitaxy wafer method, thereby eliminating the need for an alignment process between the LED stack and the CMOS electrode pad, and by ensuring that each LED stack emits only a specific color. The types of implementation for the recently trending Metaverse are classified into four forms: VR (virtual reality), AR (augmented reality), MR (mixed reality), and XR (extended reality). Among these, the future Metaverse ecosystem is expected to develop around XR, a reality that integrates VR, AR, and MR. To effectively implement this, devices (such as smart glasses and head-mounted displays) containing microdisplays with a diagonal length of less than one inch as core components are required, along with software for next-generation computing platforms capable of providing innovative user experiences. In particular, the development of high-performance microdisplay panel technology is absolutely necessary to provide XR users with the greatest sense of immersion, visibility, and convenience while minimizing dizziness. As illustrated in FIG. 1, the conventional microdisplay panel (10) is a technology that combines a Si CMOS semiconductor wafer process with a high-resolution, high-brightness ultra-small display process. The conventional microdisplay panel (10) may have a structure in which a Si CMOS wafer (11) having a crystal plane of 4" or larger (100) equipped with a plurality of CMOS electrode pads (12), a microLED electrode pad (14), and a transparent wafer (13) having a plurality of microLED chips (15) are bonded through a conductive bond (16). Meanwhile, the types of microdisplay panels expected to be applied to XR devices include liquid crystal (LC) based LCoS (LC on Si), OLED (organic light-emitting diode) based OLEDoS (OLED on Si), and ultra-small microLED based LEDoS (LED on Si) having a pixel size of less than 5㎛. In the case of VR with a low pixel density display, development and mass production are centered on LCoS and OLEDoS. However, with the advancement of metaverse implementation technology, there is an increasing need for lightweight AR, MR, and XR devices equipped with high pixel density microdisplay panels. In response to this need, there is an urgent need to develop LEDoS technology, which is attracting attention as a theoretically ideal solution based on the superiority of inorganic properties, but a microdisplay panel platform for this has not yet been established. When applied to XR devices, microLED-based LEDoS with pixel sizes of less than 5㎛ offers the advantages of excellent power-to-performance ratio and short response speed. Additionally, it has a long lifespan due to its inorganic composition and allows for efficient power usage, which helps mitigate heat and enables long battery life. In particular, since XR devices have a very short distance between the display and the eyes, even a slight delay in image conversion can easily cause discomfort such as dizziness. Therefore, LEDoS, which has a nanosecond response speed, is considered the most suitable for XR devices compared to LCoS and OLEDoS, which have microsecond response speeds. Furthermore, it is assessed that the biggest reason LEDoS is attracting attention in AR, MR, and XR devices, unlike VR, is due to its brightness and luminous efficiency. Given the nature of smart glasses that can be worn regardless of location, high brightness is an essential condition to ensure normal operation even in outdoor environments such as sunlight. Theoretically, microLEDs support brightness levels of tens to millions of nits, and since microLEDs are inorganic rather than organic, they also have the advantage of high luminous efficiency. However, despite the aforementioned advantages, the biggest reason why ultra-small microLED-based LEDoS with pixel sizes of less than 5㎛ has not established itself as a key component of XR devices is the difficulty of mass production. In other words, since LEDoS requires fixing millions of ultra-small microLEDs onto a Si CMOS wafer, the process difficulty is high and the yield is very low, leading to increased manufacturing costs and high component prices. This is reflected in the end consumer price, resulting in high-priced XR devices, making it difficult to meet market demand. Meanwhile, as illustrated in Fig. 2, until recently, the development of LEDoS with microLED light sources of group 3-5 compounds (GaN, GaP, etc.) has been carried out through traditional approaches such as ① monolithic integration of a wafer (or unit die) composed of a microLED array on a Si CMOS wafer, or ② hybridization between wafers (or unit dies) on a Si C