Micro-display chip and preparation method thereof

Abstract

According to the micro-display chip and the preparation method thereof provided by the invention, in the micro-display chip, a plurality of groups of driving electrodes which are tightly arranged are configured on the surface of a driving substrate; each group of driving electrodes comprises a first electrode contact, a second electrode contact, a third electrode contact and a fourth electrode contact which are different in position and mutually insulated, the first electrode contact, the second electrode contact and the third electrode contact are electrode contacts of the same type, and the first electrode contact, the second electrode contact and the third electrode contact are arranged around the fourth electrode contact; the fourth electrode contact is positioned in a maximum triangle formed by outer common tangent lines of the first electrode contact, the second electrode contact and the third electrode contact; the light-emitting units are bonded to different height positions of the first electrode contact, the second electrode contact and the third electrode contact in the longitudinal direction and connected with the anode contacts respectively, the light-emitting units in the same group are conductively connected with the common cathodes in the driving electrodes in each group, and the arrangement density of the light-emitting units can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, and in particular to a micro display chip and a preparation method thereof. BACKGROUND

[0002] Micro LED display technology integrates micro semiconductor light-emitting diodes (LEDs) in a matrix form on a chip with high density, has the characteristics of small size, high integration, and self-emission, and the like. With the application of Micro LED in the fields of AR / VR, vehicle screens, and the like, full-color Micro LED display has become a demand. In the prior art, in order to reduce the difficulty of alignment bonding, a three-layer LED structure is usually used to achieve full-color display in a vertical stacking manner. For example, a full-color pixel unit is disclosed in Chinese Patent 202210475669.0, in which the light-emitting devices of each layer are vertically stacked and connected to a driving substrate through vias, respectively, to achieve full-color display. However, this approach has the technical problem of low light extraction efficiency. Since the upper layer of light-emitting material covers the lower layer of light-emitting material, and the connection electrodes of each layer also block part of the light-emitting surface, the light of the lower layer of device is blocked, and the light extraction efficiency of the pixel unit cannot be fully utilized. In addition, due to the large number of pixel units and high density in the Micro LED display chip, there is also a problem of difficulty in lateral expansion of current. SUMMARY

[0003] In order to overcome the above shortcomings, the present application provides a micro display chip and a preparation method thereof. The RGB light-emitting units are arranged in a three-dimensional staggered manner combined with a central common conductive column, which can fully utilize the light efficiency of each light-emitting unit and make the current better and more evenly expand to each light-emitting unit.

[0004] The technical scheme provided by the present application is as follows: On the one hand, the present application provides a micro display chip, comprising: a driving substrate, the surface of which is configured with a driving circuit, and the surface of the driving circuit is configured with a plurality of groups of driving electrodes arranged closely; each group of driving electrodes includes first, second, third, and fourth electrode contacts that are different in position and insulated from each other, the first, second, and third electrode contacts are the same type of electrode contacts, the first, second, and third electrode contacts are arranged around the fourth electrode contact, and the fourth electrode contact is located within the largest triangle formed by the outer common tangent of the first, second, and third electrode contacts; a first light-emitting unit, a second light-emitting unit, and a third light-emitting unit are respectively bonded in the longitudinal direction of the positions of the first, second, and third electrode contacts, and the longitudinal heights of the light-emitting surfaces of the first, second, and third light-emitting units are different. The first light-emitting unit, the second light-emitting unit, and the third light-emitting unit each include an upper electrode surface and a lower electrode surface. The lower electrode surface of the first light-emitting unit is electrically connected to the first electrode contact, the lower electrode surface of the second light-emitting unit is electrically connected to the second electrode contact, and the lower electrode surface of the third light-emitting unit is electrically connected to the third electrode contact. Furthermore, the upper electrode surfaces of the first light-emitting unit, the second light-emitting unit, and the third light-emitting unit are all electrically connected to the fourth electrode contact.

[0005] On the other hand, the present invention provides a method for fabricating a microdisplay chip, comprising: S10 provides a driving substrate, on the surface of which a driving circuit is disposed, and on the surface of which a plurality of closely arranged driving electrodes are disposed; each group of driving electrodes includes a first electrode contact, a second electrode contact, a third electrode contact and a fourth electrode contact that are insulated from each other and are located at different positions. The first electrode contact, the second electrode contact and the third electrode contact are electrode contacts of the same type. The first electrode contact, the second electrode contact and the third electrode contact are arranged around the fourth electrode contact, and the fourth electrode contact is located within the largest triangle formed by the outer common tangent of the first electrode contact, the second electrode contact and the third electrode contact. S20 Bonds a first semiconductor light-emitting structure to the surface of the driving substrate, etches the first semiconductor light-emitting structure, and forms a first light-emitting unit at the location of the first electrode contact; the lower electrode surface of the first light-emitting unit is electrically connected to the first electrode contact, a transparent electrode layer is formed from the metal electrode on the upper electrode surface of the first light-emitting unit to the bonding layer surface at the corresponding position of the fourth electrode contact, and an insulating material is filled to cover the first light-emitting unit and the transparent electrode layer and the upper surface is planarized to form a primary insulating layer. S30 Bonds a second semiconductor light-emitting structure to the surface of the primary insulating layer, etches the second semiconductor light-emitting structure, and forms a second light-emitting unit in the longitudinal direction at the location of the second electrode contact; the lower electrode surface of the second light-emitting unit is electrically connected to the second electrode contact, and a transparent electrode layer is formed from the metal electrode on the upper electrode surface of the second light-emitting unit to the bonding layer surface at the corresponding position of the fourth electrode contact; an insulating material is filled to cover the second light-emitting unit and the transparent electrode layer, and the upper surface is planarized to form a secondary insulating layer. S40 bonds a third semiconductor light-emitting structure to the surface of the secondary insulating layer, etches the third semiconductor light-emitting structure, and forms a third light-emitting unit in the longitudinal direction at the location of the third electrode contact; the lower electrode surface of the third light-emitting unit is electrically connected to the third electrode contact, a transparent electrode layer is formed from the metal electrode on the upper electrode surface of the third light-emitting unit to the bonding layer surface at the corresponding position of the fourth electrode contact, and an insulating material is filled to cover the third light-emitting unit and the transparent electrode layer and the upper surface is planarized to form a tertiary insulating layer.

[0006] The microdisplay chip and its fabrication method provided by this invention can bring at least the following beneficial effects: 1. The heights of the three light-emitting units in each group are different. They are formed by etching after vertically stacking and bonding semiconductor light-emitting structures of different colors on the entire surface. No alignment bonding is used, so it is not limited by alignment accuracy. 2. The three light-emitting units in each group are arranged around the common cathode and are simultaneously conductively connected to the central common cathode, which enables the current to be better and more evenly distributed to each light-emitting unit. 3. The triangular spaces occupied by two adjacent groups of light-emitting units are interlocked, making full use of the space and effectively increasing the arrangement density of light-emitting units in the microdisplay chip; 4. Large bonding layers are sequentially formed on the surface of the cathode contact at the height of the light-emitting unit. Each light-emitting unit is electrically connected to the cathode contact by forming a transparent electrode layer and a large bonding layer, which enhances the stability and reliability of the conductivity. Attached Figure Description

[0007] Figure 1 This is a top view schematic diagram of the driving substrate of the microdisplay chip in one embodiment of the present invention; Figure 2 This is a top view of a microdisplay chip in another embodiment of the present invention; Figure 3 for Figure 2 A cross-sectional view along the XX direction; Figure 4 for Figure 2 A cross-sectional view along the YY direction; Figure 5 for Figure 2 A cross-sectional view along the ZZ direction.

[0008] Figure label: 10-Metal electrode, 11-Transparent electrode layer, 12-Conductive pillar, 100-Driving substrate, 110-First electrode contact, 120-Second electrode contact, 130-Third electrode contact, 140-Fourth electrode contact, 200-Primary insulating layer, 210-Primary bonding layer, 220-First light-emitting unit, 300-Secondary insulating layer, 310-Secondary bonding layer, 320-Secondary light-emitting unit, 400-Tertiary insulating layer, 410-Secondary bonding layer, 420-Third light-emitting unit. Detailed Implementation

[0009] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0010] One embodiment of the present invention provides a microdisplay chip, comprising: A driving substrate has a driving circuit disposed on its surface, and multiple sets of driving electrodes are arranged closely on the surface of the driving circuit. Each set of driving electrodes includes a first electrode contact, a second electrode contact, a third electrode contact, and a fourth electrode contact that are insulated from each other and located at different positions. The first, second, and third electrode contacts are of the same type and are arranged around the fourth electrode contact. The fourth electrode contact is located within the largest triangle formed by the external common tangents of the first, second, and third electrode contacts. A first light-emitting unit, a second light-emitting unit, and a third light-emitting unit are bonded together in the longitudinal direction at the locations of the first electrode contact, the second electrode contact, and the third light-emitting unit has a different longitudinal height of its light-emitting surface. The first light-emitting unit, the second light-emitting unit, and the third light-emitting unit include an upper electrode surface and a lower electrode surface. The lower electrode surface of the first light-emitting unit is electrically connected to the first electrode contact, the lower electrode surface of the second light-emitting unit is electrically connected to the second electrode contact, and the lower electrode surface of the third light-emitting unit is electrically connected to the third electrode contact.

[0011] In this embodiment, the driving substrate can be a silicon-based CMOS wafer, a glass-based TFT substrate, a rigid substrate based on PCB (Printed Circuit Board), glass, or any other rigid substrate. It can also be a flexible substrate made primarily of PET (Polyethylene Terephthalate), PI (Polyimide), PEN (Polyethylene Naphthalate), etc. The substrate can be transparent or opaque. In practical applications, those skilled in the art can flexibly select a suitable substrate according to actual needs, and this embodiment does not impose specific limitations in this regard. The driving circuit on the surface of the driving substrate is used to provide current to the light-emitting unit and realize the on-off control of the light-emitting unit. Multiple sets of driving electrodes on the surface of the driving circuit are closely arranged together to facilitate conduction to the closely arranged light-emitting units. Each set of driving electrodes includes one cathode electrode contact and three anode electrode contacts. The three anode contacts surround the cathode contact, so that the light-emitting units corresponding to the three anode contacts in the same set of driving electrodes share a cathode contact, forming a common cathode structure. Alternatively, each set of driving electrodes includes one anode electrode contact and three cathode electrode contacts. The three cathode contacts surround the anode contact, so that the light-emitting units corresponding to the three cathode contacts in the same set of driving electrodes share a cathode contact, forming a common anode structure.

[0012] Each light-emitting unit, electrically connected to the first, second, and third electrode contacts, contains stacked N-type semiconductor material, an active layer material, and P-type semiconductor material. When a voltage is applied to the light-emitting unit, electrons and holes in the N-type and P-type semiconductor materials recombine in the active layer material and release energy to emit light. The upper electrode surface of each light-emitting unit is the surface of N-type semiconductor material, and the lower electrode surface is the surface of P-type semiconductor material. The P-type semiconductor material surface of each light-emitting unit is electrically connected to the anode contacts (first electrode contact / second electrode contact / third electrode contact), respectively. The N-type semiconductor material surfaces of the same group of light-emitting units are electrically connected to the cathode contact (fourth electrode contact). The three light-emitting units in the same group share one cathode contact, but the three connected anode contacts are independent of each other. Therefore, by controlling the corresponding anode contact, the independent control of the corresponding light-emitting unit can be achieved. Those skilled in the art can design corresponding driving circuits to control the light-emitting units according to actual needs. In other embodiments, a common anode design can also be adopted. For example, in each group of driving electrodes on the driving substrate used in a microdisplay chip, the first, second, and third electrode contacts are cathode contacts, and the fourth electrode contact is also a cathode contact. The upper electrode surface of each light-emitting unit is a P-type semiconductor material surface, and the lower electrode surface of each light-emitting unit is an N-type semiconductor material surface. The N-type semiconductor material surface of each light-emitting unit is electrically connected to the cathode contact (first electrode contact / second electrode contact / third electrode contact), respectively. The P-type semiconductor material surfaces of the same group of light-emitting units are all electrically connected to the anode contact (fourth electrode contact). To achieve full-color light emission, the first, second, and third light-emitting units emit one of red, green, and blue light, respectively, and they are all different from each other; for example, the first light-emitting unit emits red light, the second light-emitting unit emits green light, and the third light-emitting unit emits blue light.The first, second, and third light-emitting units are all formed by etching after bonding a semiconductor light-emitting structure. The first light-emitting unit is formed by etching away the area excluding the first electrode contact after bonding the first semiconductor light-emitting structure; the second light-emitting unit is formed by etching away the area excluding the second electrode contact after bonding the second semiconductor light-emitting structure; and the third light-emitting unit is formed by etching away the area excluding the third electrode contact after bonding the third semiconductor light-emitting structure. In this embodiment, the distance between adjacent light-emitting units can be adjusted according to the size and shape of the light-emitting units, as long as they do not overlap or obstruct each other. The horizontal projected areas of the light-emitting units do not overlap and are located at the positions of the first electrode contact, the second electrode contact, and the third electrode contact, respectively. Therefore, in this microdisplay chip, the light efficiency of each light-emitting unit can be fully utilized, avoiding the waste or loss of light caused by different colors of light overlapping or superimposing each other, resulting in a more uniform light distribution and thus improving the display effect. Furthermore, the vertical heights of the first, second, and third light-emitting units are also different. In the bonding process, the semiconductor light-emitting structures at the heights of each light-emitting unit can be stacked and bonded sequentially, significantly reducing the difficulty of bonding in the process. In this embodiment, the first, second, and third light-emitting units are circular in shape and size. In other embodiments, those skilled in the art can design each light-emitting unit to have other shapes, such as squares, polygons, or even irregular shapes, according to actual conditions. The size of each light-emitting unit can also be designed independently. This embodiment does not limit this, as long as the horizontal projections of each light-emitting unit do not overlap, are at a certain distance from the fourth electrode contact at the center of each group of driving electrodes, and can be arranged closely together.

[0013] To increase the arrangement density of the light-emitting units on the surface of the driving substrate, this embodiment further configures the first electrode contact, the second electrode contact, and the third electrode contact to surround the fourth electrode contact, and the fourth electrode contact is located within the largest triangle formed by the outer common tangent of the first electrode contact, the second electrode contact, and the third electrode contact. Specifically, the largest triangle is the triangle formed by the first electrode contact, the second electrode contact, and the third electrode contact being inscribed in the three vertices of a triangle. Placing the fourth electrode contact within this triangle further reduces the area of ​​a single set of driving electrodes without affecting the arrangement of adjacent driving electrodes, thereby increasing the pixel density on the surface of the driving substrate. The specific positional relationship between the fourth electrode contact and the first, second, and third electrode contacts can be determined according to the actual situation. Theoretically, as long as it is located within the largest triangle formed by the outer common tangent of the first, second, and third electrode contacts, and the semiconductor light-emitting units formed on the surfaces of the first, second, and third electrode contacts are mutually insulated, and the light-emitting units are mutually insulated from the conductive pillars formed on the surface of the fourth electrode contact, it is acceptable.

[0014] The P-type semiconductor material side of each light-emitting unit is located at the bottom of the unit and is electrically connected to the anode contact on the surface of the driving substrate through a bonding layer. A metal electrode is formed on the upper electrode surface of each light-emitting unit, making an ohmic contact with the N-type semiconductor material. A transparent electrode layer is formed on the bonding layer surface from the metal electrode to the fourth electrode contact surface, and is electrically connected to the cathode contact. The upper electrode surfaces of the first, second, and third light-emitting units are all electrically connected to the fourth electrode contact. The lower electrode surfaces of the first, second, and third light-emitting units are all electrically connected to the corresponding first / second / third electrode contacts on the driving substrate surface through bonding layers. Furthermore, the bonding layers corresponding to each light-emitting unit are also formed in the longitudinal direction at the location of the fourth electrode contact. Bonding layers of different heights are connected by conductive pillars. That is, the surface of the fourth electrode contact is sequentially formed with bonding layers and conductive pillars stacked upwards. The connection method between each light-emitting unit and the fourth electrode contact is that each light-emitting unit forms a transparent electrode layer from the metal electrode on the upper electrode surface to the bonding layer surface at the location of the fourth electrode contact. In this way, the fourth electrode contact is connected to the metal electrode on the upper electrode surface of the light-emitting unit through the bonding layer and the transparent electrode layer, thus conducting current to the corresponding light-emitting unit.

[0015] To ensure better and more uniform current distribution, in each group of driving electrodes on the driving substrate, all first, second, and third electrode contacts are arranged in an equilateral triangular grid array. Within each group of driving electrodes, the first, second, and third electrode contacts are located at the three vertices of the equilateral triangle, and in the horizontal direction, the equilateral triangles formed by adjacent driving electrode groups face opposite directions; in the vertical direction, the equilateral triangles formed by adjacent driving electrode groups face the same direction. In one example, in multiple groups of driving electrodes closely arranged on the surface of the driving substrate, within each group of driving electrodes, the fourth electrode contact is positioned at the center of the equilateral triangle formed by the first, second, and third electrode contacts.

[0016] For ease of description, the first, second, and third electrode contacts will all be anode contacts, and the fourth electrode contact will be a cathode contact, as an example of the microdisplay chip provided in this embodiment. Figure 1As shown, the driving substrate 100 used in a microdisplay chip has a total of 8 sets of driving electrodes on its surface. In each set of driving electrodes, the first electrode contact 110, the second electrode contact 120, and the third electrode contact 130 (i.e., 3 anode contacts) are respectively arranged at the 3 vertices of an equilateral triangle, and the fourth electrode contact 140 (i.e., the cathode contact) is arranged at the center of the equilateral triangle formed by the 3 anode contacts of the driving electrode set, with the same distance from each anode contact (for ease of understanding, the triangle formed by connecting the anode contacts in each set of driving electrodes in the figure is not a solid structure); and in the driving substrate, two adjacent sets of driving electrodes in the horizontal direction are arranged together, that is, the vertices of the triangle formed by connecting a set of driving electrodes are connected together. One set of driving electrodes is positioned upwards and facing forwards, while the other set of driving electrodes forms a triangle with its vertices facing downwards and inverted. Adjacent sets of driving electrodes fit together to form a rhombus, and the next row of driving electrode sets is also arranged in this manner, making them more densely packed on the entire surface of the driving substrate. At the same time, since each light-emitting unit is bonded to the vertical direction of the first electrode contact, the second electrode contact, and the third electrode contact, the arrangement of the driving electrodes determines the layout of the light-emitting units. Each light-emitting unit is also arranged in an equilateral triangular grid array, with the light-emitting units in the same group located at the three vertices of the equilateral triangle and connected to the fourth electrode contact at the center of the triangle. This arrangement can utilize space more efficiently and is beneficial to improving display performance.

[0017] In one example, such as Figures 2-5 As shown, Figure 2 The microdisplay chip shown has four groups of RGB light-emitting units. The three light-emitting units in each group are circular and arranged at the vertices of an equilateral triangle. A transparent electrode layer 11 is formed on the metal electrode surface of each light-emitting unit and connected to the common cathode at the center of the triangle, forming a common cathode structure. This facilitates the uniform spread of current to each light-emitting unit. The triangular space occupied by two adjacent groups of light-emitting units in the horizontal direction is interlocked, making full use of the space and increasing the arrangement density. The microdisplay chip has three layers. In each group of light-emitting units, the first light-emitting unit 220 is located in the lowest first layer, the second light-emitting unit 320 is located in the middle second layer, which is higher than the first light-emitting unit, and the third light-emitting unit 420 is located in the highest third layer, which is higher than the second light-emitting unit. In the first and second layers, conductive pillars 12 are formed above the transparent electrode layer 11 in the longitudinal direction of the fourth electrode contact, allowing the fourth electrode contact to extend upwards layer by layer. In the first layer, conductive pillars 12 are also formed in the longitudinal direction of the second and third electrode contacts, allowing the second and third electrode contacts to extend upwards to the upper surface of the first layer. In the second layer, conductive pillars 12 are also formed in the longitudinal direction of the third electrode contact, allowing the third electrode contact to extend upwards to the upper surface of the second layer. The details are as follows: The first layer includes: such as Figure 3 As shown, a primary bonding layer 210 formed on the surface of the driving substrate 100 covers at least the surfaces of the first electrode contact 110 and the fourth electrode contact 140. The lower electrode surface of the first light-emitting unit 220 is bonded to the surface of the first electrode contact of the driving substrate through the primary bonding layer and is electrically connected to the first electrode contact. The primary bonding layer covering the surfaces of the first electrode contact and the fourth electrode contact not only serves to bond the light-emitting unit but also expands the area of ​​the electrode contact, forming a more stable conductive connection with the light-emitting unit. To prevent leakage, a primary insulating layer 200 is also formed around the first light-emitting unit. The primary insulating layer is formed on the entire surface of the driving substrate, with a height that at least covers the first light-emitting unit. Through holes are provided on the upper electrode surface of the first light-emitting unit 220 and at the position of the fourth electrode contact 140. The first light-emitting unit is electrically connected to the fourth electrode contact 140 at the center of each group of driving electrodes by forming a metal electrode 10 in the through hole extending to the upper electrode surface and forming a transparent electrode layer 11 on the surface of the primary bonding layer in the through hole from the metal electrode to the position of the fourth electrode contact. The primary insulating layer is formed through two deposition processes: the first deposition covers the surface of the light-emitting unit, and the second deposition covers the transparent electrode layer. After the second deposition of insulating material onto the transparent electrode layer, to allow the second, third, and fourth electrode contacts to be led upwards to the surface of the primary insulating layer for conductive connection with the upper light-emitting unit, as shown below... Figure 4 and Figure 5 As shown, the primary insulating layer 200 also has first through holes for filling conductive metal etched at the corresponding positions of the second electrode contact 120, the third electrode contact 130 and the fourth electrode contact 140. The first through holes at the second electrode contact and the third electrode contact extend to the surface of the primary bonding layer, and the first through hole at the fourth electrode contact extends to the surface of the transparent electrode layer connected to the first light-emitting unit. Subsequently, conductive metal is filled into the first through holes to form conductive pillars 12 that lead the second electrode contact 120, the third electrode contact 130 and the fourth electrode contact 140 upward. It should be noted that the function of the conductive pillar 12 in this layer is different from that of the transparent electrode layer 11. The function of the conductive pillar 12 is to lead the second electrode contact 120, the third electrode contact 130 and the fourth electrode contact 140 upward to the surface of the first insulating layer. The transparent electrode layer 11 is only formed at the location of the fourth electrode contact and connected to the metal electrode of the first light-emitting unit, and does not exist at the locations of other electrode contacts. Its function is to conductively connect the first light-emitting unit and the fourth electrode contact. The structures and formation methods of the two are also different. The transparent conductive layer is formed after the first deposition of insulating material, and the conductive pillar is formed after the second deposition of insulating material.

[0018] The second layer includes: such as Figure 4As shown, the secondary bonding layer 310 formed on the surface of the primary insulating layer 200 covers at least the second electrode contact 120, the surface of the first through hole filled with conductive metal, and the fourth contact 140, the surface of the first through hole filled with conductive metal. The lower electrode surface of the second light-emitting unit 320 is bonded to the surface of the primary insulating layer at the second electrode contact position (i.e., the surface of the first through hole above the second electrode contact, where conductive metal is filled to form a conductive pillar 12) through the secondary bonding layer. From top to bottom, it is electrically connected to the second electrode contact 120 through the secondary bonding layer 310, the conductive pillar 12, and the primary bonding layer 210. The secondary bonding layer covers the surface of the primary insulating layer at the second electrode contact and the fourth electrode contact position. In addition to bonding the second light-emitting unit, it can also increase the area of ​​the electrode contact and form a more stable conductive connection with the second light-emitting unit. To prevent leakage, a secondary insulating layer 300 is formed around the second light-emitting unit. This secondary insulating layer covers the entire surface of the primary insulating layer and its height is sufficient to cover the second light-emitting unit. Through-holes are formed on the electrode surface and at the fourth electrode contact 140 positions of the second light-emitting unit 320. The second light-emitting unit is electrically connected to the fourth electrode contact 140 at the center of each group of driving electrodes by forming a metal electrode 10 in the through-hole extending to the upper electrode surface and a transparent electrode layer 11 forming on the surface of the secondary bonding layer from the metal electrode to the through-hole at the fourth electrode contact position. The secondary insulating layer is formed by two depositions of insulating material during the fabrication process: the first deposition covers the upper surface of the light-emitting unit, and the second deposition covers the transparent electrode layer. After the second deposition of insulating material to the transparent electrode layer, and simultaneously to allow the third and fourth electrode contacts to be led upwards to the surface of the secondary insulating layer for conductive connection with the light-emitting unit in the third layer, as shown... Figure 5 As shown, in the secondary insulating layer 300, second through-holes for filling conductive metal are etched at the corresponding positions of the third electrode contact 130 and the fourth electrode contact 140. The second through-hole at the third electrode contact extends to the surface of the secondary bonding layer, and the second through-hole at the fourth electrode contact extends to the surface of the transparent electrode layer connected to the second light-emitting unit. Subsequently, conductive metal is filled into the second through-holes to form conductive pillars 12, which lead the third and fourth electrode contacts upward. It should be noted that the function of the conductive pillars 12 in the second layer is different from that of the transparent electrode layer 11. The function of the conductive pillars 12 is to lead the third electrode contact 130 and the fourth electrode contact 140 upward to the surface of the second insulating layer. The transparent electrode layer 11 is only formed at the location of the fourth electrode contact and connected to the metal electrode of the second light-emitting unit, and does not exist at other electrode contact locations. Its function is to conductively connect the second light-emitting unit and the fourth electrode contact. The structures and formation methods of the two are also different. The transparent conductive layer is formed after the first deposition of insulating material, and the conductive pillars are formed after the second deposition of insulating material.

[0019] The third layer includes: such as Figure 5 As shown, the tertiary bonding layer 410 formed on the surface of the secondary insulating layer 300 covers at least the third electrode contact 130, the surface of the second through hole filled with conductive metal, and the fourth electrode contact 140, the surface of the second through hole filled with conductive metal. The lower electrode surface of the third light-emitting unit 420 is bonded to the surface of the secondary insulating layer at the third electrode contact position (i.e., the surface of the second through hole above the third electrode contact, where conductive metal is filled to form a conductive pillar 12) through the tertiary bonding layer. From top to bottom, it is electrically connected to the third electrode contact through the tertiary bonding layer 410, the conductive pillar 12, the secondary bonding layer 310, the conductive pillar 12, and the primary bonding layer 210. The tertiary bonding layer covers the surface of the secondary insulating layer at the third electrode contact and the fourth electrode contact position. In addition to bonding the third light-emitting unit, it can also increase the area of ​​the electrode contact and form a more stable conductive connection with the third light-emitting unit. To prevent leakage, a tertiary insulating layer 400 is formed around the third light-emitting unit. This tertiary insulating layer covers the entire surface of the secondary insulating layer and its height at least covers the third light-emitting unit. Through-holes are formed on the electrode surface and at the fourth electrode contact 140 of the third light-emitting unit 420. The third light-emitting unit is electrically connected to the fourth electrode contact at the center of each group of driving electrodes by forming a metal electrode 10 in the through-hole extending to the upper electrode surface and a transparent electrode layer 11 forming on the surface of the secondary bonding layer in the through-hole from the metal electrode to the fourth electrode contact. To protect the transparent electrode layer, the tertiary insulating layer is formed by two depositions of insulating material during the fabrication process: the first deposition covers the upper surface of the light-emitting unit, and the second deposition covers the transparent electrode layer. The transparent electrode layer 11 of the third layer is formed at the location of the fourth electrode contact and connects to the metal electrode of the third light-emitting unit, serving to electrically connect the third light-emitting unit and the fourth electrode contact. It is important to note that, unlike the first and second layers, the third layer does not contain conductive pillar structures. This is because it is not necessary to form other light-emitting units above the third layer, so there is no need to extend the electrode contacts upwards.

[0020] The transparent electrode layer 11 is made of a conductive material that is transparent to the emission wavelength of each light-emitting unit, such as ITO (tin-doped indium oxide), ICO (cerium-doped indium oxide), IZO (zinc-doped indium oxide), etc.

[0021] In this embodiment, the metal electrodes of each light-emitting unit are formed at the center of the upper electrode surface. To reduce the obstruction of the light-emitting surface of the light-emitting unit by the metal electrodes, the metal electrodes should be designed to be as small as possible while ensuring conductivity. Positioning them at the center of the upper electrode surface of each light-emitting unit facilitates the uniform spread of current within the light-emitting unit. It should be understood that the horizontal projection of the metal electrodes on the upper electrode surface of each light-emitting unit corresponds one-to-one with the anode contact arrangement on the driving substrate surface. That is, the metal electrodes, along with the first electrode contact, the second electrode contact, and the third electrode contact, are arranged in an equilateral triangular grid array.

[0022] At the second, third, and fourth electrode contacts, conductive pillars 12 formed by filling conductive metal in the through-holes of each insulating layer are perpendicular to the surface of the driving substrate and stacked sequentially upwards. The primary bonding layer 210, secondary bonding layer 310, and tertiary bonding layer 410 are all made of metals with good conductivity, such as at least one of gold, titanium, nickel, aluminum, copper, indium, tin, or silver-tin alloys, and can be formed by one or more processes including deposition, evaporation, magnetron sputtering, thermal evaporation, electroless plating, electroplating, and electron beam evaporation. In the fabrication process of the bonding layer, the bonding layer is first formed across the entire surface. After bonding the semiconductor light-emitting structures of each layer and etching to form the light-emitting units, the bonding layer is further etched except for the location of the formed light-emitting units to prevent the light-emitting units from connecting with other electrode contacts. In this embodiment, when etching the primary bonding layer 210, only the area between each electrode contact is etched away. That is, except for the primary bonding layer at the bottom of the first light-emitting unit and the surface of the fourth electrode contact, the primary bonding layer on the surface of the second electrode contact and the third electrode contact is retained. In this way, when the primary insulating layer is subsequently etched to form the first through-hole to lead the second electrode contact and the third electrode contact upward, The bonding layer expands the area of ​​the electrode contacts, and only the bonding layer needs to be aligned during etching, significantly reducing the alignment difficulty and also reducing the etching depth (only etching to the bonding layer is required). Similarly, when etching the secondary bonding layer 310, only the area corresponding to the first light-emitting unit and the area between each electrode contact is etched away. That is, except for the secondary bonding layer at the bottom of the second light-emitting unit and the location of the fourth electrode contact, the secondary bonding layer on the surface of the first via filled with conductive metal at the location of the third electrode contact is retained. This facilitates the subsequent etching of the secondary insulating layer to lead the third electrode contact upward, thereby expanding the corresponding area of ​​the third electrode contact and reducing the alignment difficulty. At the locations of the second, third, and fourth electrode contacts, in the vertical direction, each layer is led upward layer by layer to the required height by means of bonding layers and conductive pillars.

[0023] In addition, to prevent the transparent electrode layer from being affected by external factors and to ensure the normal operation of the light-emitting unit, the thicknesses of the primary, secondary, and tertiary insulating layers respectively cover the transparent electrode layer connecting the metal electrodes at the top of the first, second, and third light-emitting units to the fourth electrode contact position, and form a flat upper surface through chemical mechanical etching. Therefore, the primary insulating layer 200, secondary insulating layer 300, and tertiary insulating layer 400 are all prepared in two steps. First, insulating material is deposited over the entire surface to cover the light-emitting unit, forming the metal electrode 10 at the top of the light-emitting unit and the transparent electrode layer 11 extending to the fourth electrode contact position. Then, insulating material is deposited over the entire surface to cover the transparent electrode layer 11, thereby forming the primary / secondary / tertiary insulating layers. Afterward, the first / secondary through-holes for filling the conductive metal are etched at the corresponding electrode contact positions in the insulating layers, forming conductive pillars to lead the electrode contacts upward.

[0024] Another embodiment of the present invention provides a method for fabricating a microdisplay chip, comprising: S10 provides a driving substrate, on the surface of which a driving circuit is disposed, and on the surface of the driving circuit are disposed multiple sets of closely arranged driving electrodes; each set of driving electrodes includes a first electrode contact, a second electrode contact, a third electrode contact and a fourth electrode contact that are insulated from each other and are located at different positions. The first electrode contact, the second electrode contact and the third electrode contact are electrode contacts of the same type. The first electrode contact, the second electrode contact and the third electrode contact are arranged around the fourth electrode contact, and the fourth electrode contact is located within the largest triangle formed by the outer common tangent of the first electrode contact, the second electrode contact and the third electrode contact.

[0025] In this embodiment, the driving substrate can be a silicon-based CMOS wafer, a glass-based TFT substrate, a rigid substrate based on PCB (Printed Circuit Board), glass, or any other rigid substrate. It can also be a flexible substrate made primarily of PET (Polyethylene Terephthalate), PI (Polyimide), PEN (Polyethylene Naphthalate), etc. The substrate can be transparent or opaque. In practical applications, those skilled in the art can flexibly select a suitable substrate according to actual needs, and this embodiment does not impose specific limitations in this regard. The driving circuit on the surface of the driving substrate is used to provide current to the light-emitting unit and realize the on-off control of the light-emitting unit. Multiple sets of driving electrodes on the surface of the driving circuit are closely arranged together to facilitate conduction to the closely arranged light-emitting units. Each set of driving electrodes includes one cathode electrode contact and three anode electrode contacts. The three anode contacts surround the cathode contact, so that the light-emitting units corresponding to the three anode contacts in the same set of driving electrodes share a cathode contact, forming a common cathode structure. Alternatively, each set of driving electrodes includes one anode electrode contact and three cathode electrode contacts. The three cathode contacts surround the anode contact, so that the light-emitting units corresponding to the three cathode contacts in the same set of driving electrodes share a cathode contact, forming a common anode structure.

[0026] To increase the arrangement density of the light-emitting units on the surface of the driving substrate, this embodiment further configures the first electrode contact, the second electrode contact, and the third electrode contact to surround the fourth electrode contact, and the fourth electrode contact is located within the largest triangle formed by the outer common tangent of the first electrode contact, the second electrode contact, and the third electrode contact. Specifically, the largest triangle is the triangle formed by the first electrode contact, the second electrode contact, and the third electrode contact being inscribed in the three vertices of a triangle. Placing the fourth electrode contact within this triangle further reduces the area of ​​a single set of driving electrodes without affecting the arrangement of adjacent driving electrodes, thereby increasing the pixel density on the surface of the driving substrate. The specific positional relationship between the fourth electrode contact and the first, second, and third electrode contacts can be determined according to the actual situation. Theoretically, as long as it is located within the largest triangle formed by the outer common tangent of the first, second, and third electrode contacts, and the semiconductor light-emitting units formed on the surfaces of the first, second, and third electrode contacts are mutually insulated, and simultaneously insulated from the conductive pillars formed on the surface of the fourth electrode contact, it is acceptable. To ensure better and more uniform current distribution, the first, second, third, and fourth electrode contacts in each group of driving electrodes on the driving substrate are spaced at the same distance. In one example, in multiple groups of driving electrodes closely arranged on the surface of the driving substrate, all the first, second, and third electrode contacts are arranged in an equilateral triangular grid array. Within each group of driving electrodes, the first, second, and third electrode contacts are located at the three vertices of the equilateral triangle, and the fourth electrode contact is positioned at the center of the equilateral triangle. Furthermore, in the lateral direction, the equilateral triangles formed by adjacent groups of driving electrodes face opposite directions; in the longitudinal direction, the equilateral triangles formed by adjacent groups of driving electrodes face the same direction. That is, the vertices of the triangles formed by connecting one group of driving electrodes are oriented upwards, while the vertices of the triangles formed by connecting another group of driving electrodes are oriented downwards and inverted. Adjacent groups of driving electrodes fit together to form a rhombus, and the driving electrode groups in the next row are also arranged in this manner, making them more densely packed across the entire surface of the driving substrate.

[0027] For ease of description, the first electrode contact, the second electrode contact, and the third electrode contact are all anode contacts, and the fourth electrode contact is a cathode contact, as an example of the microdisplay chip provided in this embodiment.

[0028] S20 Bonds a first semiconductor light-emitting structure to the surface of the driving substrate, etches the first semiconductor light-emitting structure, and forms a first light-emitting unit at the location of the first electrode contact. The lower electrode surface of the first light-emitting unit is electrically connected to the first electrode contact. A transparent electrode layer is formed from the metal electrode on the upper electrode surface of the first light-emitting unit to the bonding layer surface at the corresponding location of the fourth electrode contact. An insulating material is filled to cover the first light-emitting unit and the transparent electrode layer, and the upper surface is planarized to form a primary insulating layer.

[0029] The first semiconductor light-emitting structure comprises stacked N-type semiconductor material, an active layer material, and P-type semiconductor material. When a voltage is applied to the light-emitting unit, electrons and holes in the N-type and P-type semiconductor materials recombine in the active layer material and release energy to emit light. The first semiconductor light-emitting structure emits one of red, green, or blue light. The upper electrode surface of the first light-emitting unit is the surface of the N-type semiconductor material, and the lower electrode surface is the surface of the P-type semiconductor material. The surface of the P-type semiconductor material is electrically connected to the first electrode contact, while the surface of the N-type semiconductor material is electrically connected to the fourth electrode contact. When bonding the first semiconductor light-emitting structure to the driving substrate, the P-type semiconductor material side faces the driving substrate, and a full-surface bonding process is used, eliminating the need for precise alignment. The specific process steps are as follows: Primary bonding layers are formed on the surface of the driving substrate and the surface of the P-type semiconductor material in the first semiconductor light-emitting structure, respectively, thereby bonding the first semiconductor light-emitting structure to the surface of the driving substrate. The shape and size of the first semiconductor light-emitting structure are basically the same as those of the driving substrate. After bonding, it covers the entire surface of the driving circuit. Therefore, the first light-emitting unit needs to be prepared by etching. Etching methods such as wet etching, dry etching, or plasma etching can be used. For example, photoresist is prepared at the location of the first electrode contact of each group of driving electrodes. The first semiconductor structure outside the photoresist is etched away. After cleaning the photoresist, the first light-emitting unit is formed. At this time, multiple first light-emitting units are arranged in an array on the surface of the driving substrate at the first electrode contact of each group of driving electrodes. At the location of the point, the lower electrode surface of the first light-emitting unit is electrically connected to the first electrode contact 110 through the primary bonding layer 210. At this time, the primary bonding layer still covers the entire surface of the driving substrate. Since the primary bonding layer is a conductive metal material, in order to avoid the first light-emitting unit from contacting the electrode contacts other than the first electrode contact and the fourth electrode contact, the primary bonding layer in the area other than the first electrode contact and the fourth electrode contact is further etched away, so that the primary bonding layer at the location of the first electrode contact and the fourth electrode contact remains independent and does not contact other electrode contacts. In this embodiment, in order to increase the area of ​​the electrode contacts and facilitate the subsequent fabrication of conductive pillars to lead other electrode contacts upwards, reducing the alignment difficulty, when etching the primary bonding layer, such as Figures 3-5 As shown, only the area between each electrode contact was etched away. That is, except for the primary bonding layer 210 at the bottom of the first light-emitting unit 220 and the position of the fourth electrode contact 140, the primary bonding layer on the surface of the second electrode contact 120 and the third electrode contact 130 is retained.

[0030] An insulating material is deposited across the entire surface until it completely covers the upper surface of the first light-emitting unit, protecting it from external influences. This insulating material fills the spaces between the first light-emitting units and between the primary bonding layers on the surfaces of the electrode contacts, providing mutual insulation and preventing leakage. To create a conductive connection between the first light-emitting unit and the fourth electrode contact, through-holes are etched onto the electrode surfaces of the first light-emitting units and at the locations of the fourth electrode contacts. (The through-holes on the electrode surfaces of the first light-emitting units are centered, ensuring that the metal electrodes formed in the subsequent through-holes are centered on the upper electrode surface.) The central position facilitates uniform current distribution within the light-emitting unit. To minimize the obstruction of the light-emitting surface by the metal electrode, the metal electrode should be designed to be as small as possible while ensuring conductivity. The through-hole shape can be designed as needed, extending to the primary bonding layer from the surface of the upper electrode of the first light-emitting unit to the surface of the fourth electrode contact. Metal material is filled into the through-hole extending to the surface of the upper electrode of the first light-emitting unit, forming an ohmic contact with the surface of the upper electrode of the first light-emitting unit to form a metal electrode. A transparent conductive material is then prepared on the surface of the primary bonding layer in the through-hole from the metal electrode to the fourth electrode contact position, forming a transparent electrode layer. Figure 2 As shown, at this time, a primary bonding layer 210 and a transparent electrode layer 11 are formed in the longitudinal direction from bottom to top at the fourth electrode contact 140 position. The fourth electrode contact is connected to the metal electrode 10 on the electrode surface of the first light-emitting unit 220 through the primary bonding layer 210 and the transparent electrode layer 11.

[0031] Insulating material is deposited again until it covers the upper surface of the transparent electrode layer. The insulating material is then etched at the corresponding positions of the second and third electrode contacts until the primary bonding layer on the surface of the driving substrate is exposed to form the first via. At the same time, the first via is also etched at the positions of the fourth electrode contacts to the transparent electrode layer to form the first via. The size of the first via is only required to be within the area of ​​the primary bonding layer on the surface of each electrode contact. Conductive metal is filled into the first via to form a conductive pillar. In this way, the second, third, and fourth electrode contacts are led upward to the surface of the primary insulating layer by means of the primary bonding layer and conductive pillar. Finally, the upper surface of the primary insulating layer is chemically and mechanically polished to make it planar, so as to facilitate the bonding of the second semiconductor light-emitting structure on the surface of the primary insulating layer.

[0032] S30 Bonds a second semiconductor light-emitting structure to the surface of the primary insulating layer, etches the second semiconductor light-emitting structure, and forms a second light-emitting unit at the location of the second electrode contact in the longitudinal direction; the lower electrode surface of the second light-emitting unit is electrically connected to the second electrode contact, and a transparent electrode layer is formed from the metal electrode on the upper electrode surface of the second light-emitting unit to the conductive pillar surface at the corresponding position of the fourth electrode contact; and an insulating material is filled to cover the second light-emitting unit and the transparent electrode layer and the upper surface is planarized to form a secondary insulating layer.

[0033] The second semiconductor light-emitting structure comprises stacked N-type semiconductor material, an active layer material, and P-type semiconductor material. When a voltage is applied to the light-emitting unit, electrons and holes in the N-type and P-type semiconductor materials recombine in the active layer material and release energy to emit light. The emitted color of the second semiconductor light-emitting structure is one of red, green, or blue light. The upper electrode surface of the second light-emitting unit is the surface of the N-type semiconductor material, and the lower electrode surface is the surface of the P-type semiconductor material. The surface of the P-type semiconductor material is electrically connected to the second electrode contact, while the surface of the N-type semiconductor material is electrically connected to the fourth electrode contact. When bonding the second semiconductor light-emitting structure to the driving substrate, the P-type semiconductor material side faces the driving substrate, using a full-surface bonding process, eliminating the need for precise alignment. The specific process steps are as follows: Secondary bonding layers are formed on the surface of the primary insulating layer and the surface of the P-type semiconductor material in the second semiconductor light-emitting structure, respectively, thereby bonding the second semiconductor light-emitting structure to the surface of the primary insulating layer. The shape and size of the second semiconductor light-emitting structure are basically the same as those of the driving substrate. After bonding, it covers the entire surface of the primary insulating layer. Therefore, the second light-emitting unit needs to be prepared by etching. Etching methods can include wet etching, dry etching, or plasma etching. For example, photoresist is prepared at the location of the second electrode contacts of each group of driving electrodes on the surface of the second semiconductor light-emitting structure. The second semiconductor structure outside the photoresist area is etched away. After cleaning the photoresist, the second light-emitting unit is formed. At this time, multiple second light-emitting units are arranged in an array at the location of the second electrode contacts of each group of driving electrodes on the surface of the primary insulating layer. Figure 4 As shown, the lower electrode surface of the second light-emitting unit is connected to the second electrode contact 120 from top to bottom via a secondary bonding layer 310, a conductive pillar 12, and a primary bonding layer 210. At this time, the secondary bonding layer still covers the entire surface of the driving substrate. Since the secondary bonding layer is a conductive metal material, to prevent the second light-emitting unit from contacting electrode contacts other than the second and fourth electrode contacts, the secondary bonding layer in areas other than the second and fourth electrode contacts is further etched away, ensuring that the secondary bonding layer at the locations of the second and fourth electrode contacts remains independent and does not contact other electrode contacts. In this embodiment, to increase the area of ​​the third electrode contact, it is easier to subsequently fabricate conductive pillars to lead the third electrode contact upwards, reducing alignment difficulty. Figures 3 to 5 As shown, when etching the secondary bonding layer 310, only the area corresponding to the first light-emitting unit 220 and between each electrode contact is etched away. That is, except for the secondary bonding layer at the bottom of the second light-emitting unit 320 and the location of the fourth electrode contact 140, the secondary bonding layer at the third electrode contact 130 on the surface of the primary insulating layer is retained.

[0034] An insulating material is deposited across the entire surface until it completely covers the upper surface of the second light-emitting unit, protecting it from external influences. This insulating material fills the spaces between the second light-emitting units and between the secondary bonding layers on the surfaces of the third and fourth electrode contacts, providing mutual insulation and preventing leakage. To create a conductive connection between the second light-emitting unit and the fourth electrode contact, through-holes are etched onto the surface of the upper electrode of the second light-emitting unit and at the location of the fourth electrode contact. (Similar to the first light-emitting unit, the through-holes on the surface of the upper electrode of the second light-emitting unit are centered, ensuring that the metal electrodes subsequently formed in the through-holes are centered on the surface of the upper electrode, which is advantageous.) The current spreads uniformly within the light-emitting unit. To reduce the obstruction of the light-emitting surface by the metal electrode, the metal electrode should be designed to be as small as possible while ensuring conductivity. The through-hole shape can be designed as needed, extending to the secondary bonding layer at the fourth electrode contact position on the surface of the upper electrode of the second light-emitting unit and the surface of the insulating layer. Metal material is filled into the through-holes penetrating to the surface of the upper electrode of the second light-emitting unit, forming an ohmic contact with the surface of the upper electrode of the second light-emitting unit to form a metal electrode. A transparent conductive material is prepared on the surface of the insulating material, from the metal electrode of the second light-emitting unit to the surface of the secondary bonding layer in the through-holes at the fourth electrode contact position in each group of driving electrodes, forming a transparent electrode layer, such as... Figure 4 As shown, at this time, a primary bonding layer 210, a transparent electrode layer 11, a conductive pillar 12, a secondary bonding layer 310, and a transparent electrode layer 11 are formed in the longitudinal direction from bottom to top at the fourth electrode contact 140 position. That is, the fourth electrode contact is connected to the metal electrode 10 on the electrode surface of the second light-emitting unit 320 through the primary bonding layer 210, the transparent electrode layer 11, the conductive pillar 12, the secondary bonding layer 310, and the transparent electrode layer 11.

[0035] Insulating material is deposited again until it covers the upper surface of the transparent electrode layer. The insulating material is then etched at the position corresponding to the third electrode contact until the secondary bonding layer retained on the surface of the primary insulating layer is exposed, forming a second via. At the same time, the fourth electrode contact is etched down to the transparent electrode layer to form a second via. The size of the second via is only required to be within the area of ​​the secondary bonding layer on the surface of each electrode contact. Conductive metal is filled into the second via to form a conductive pillar. In this way, the third and fourth electrode contacts are led upward to the surface of the secondary insulating layer through the secondary bonding layer and the conductive pillar. Finally, the upper surface of the secondary insulating layer is chemically and mechanically polished to make it planar, which facilitates the bonding of the third semiconductor light-emitting structure on the surface of the secondary insulating layer.

[0036] S40 bonds a third semiconductor light-emitting structure to the surface of the secondary insulating layer, etches the third semiconductor light-emitting structure, and forms a third light-emitting unit in the longitudinal direction at the location of the third electrode contact; the lower electrode surface of the third light-emitting unit is electrically connected to the third electrode contact, and a transparent electrode layer is formed from the metal electrode on the upper electrode surface of the third light-emitting unit to the bonding layer surface at the corresponding position of the fourth electrode contact; insulating material is filled to cover the third light-emitting unit and the transparent electrode layer, and the upper surface is planarized to form a tertiary insulating layer.

[0037] The third semiconductor light-emitting structure stacks N-type semiconductor material, an active layer material, and P-type semiconductor material. When a voltage is applied to the light-emitting unit, electrons and holes in the N-type and P-type semiconductor materials recombine in the active layer material and release energy to emit light. The emitted color of the third semiconductor light-emitting structure is one of red, green, or blue light. The upper electrode surface of the third light-emitting unit is the surface of the N-type semiconductor material, and the lower electrode surface is the surface of the P-type semiconductor material. The surface of the P-type semiconductor material is electrically connected to the third electrode contact, while the surface of the N-type semiconductor material is electrically connected to the fourth electrode contact. When bonding the third semiconductor light-emitting structure to the driving substrate, the P-type semiconductor material side faces the driving substrate, using a full-surface bonding process, eliminating the need for precise alignment. The specific process steps are as follows: The tertiary bonding layers are formed on the surface of the secondary insulating layer and the surface of the P-type semiconductor material in the third semiconductor light-emitting structure, respectively, thereby bonding the third semiconductor light-emitting structure to the surface of the secondary insulating layer. The shape and size of the third semiconductor light-emitting structure are basically the same as those of the driving substrate. After bonding, it covers the entire surface of the primary insulating layer. Therefore, the third light-emitting unit needs to be prepared by etching. Etching methods can be wet etching, dry etching, or plasma etching. For example, photoresist is prepared at the location of the third electrode contact of each group of driving electrodes on the surface of the third semiconductor light-emitting structure. The third semiconductor structure outside the photoresist is etched away. After cleaning the photoresist, the third light-emitting unit is formed. At this time, multiple third light-emitting units are arranged in an array at the location of the third electrode contact of each group of driving electrodes on the surface of the secondary insulating layer. Figure 5 As shown, the lower electrode surface of the third light-emitting unit is connected to the third electrode contact 130 from top to bottom through a tertiary bonding layer 410, a conductive pillar 12, a secondary bonding layer 310, a conductive pillar 12, and a primary bonding layer 210. At this time, the tertiary bonding layer still covers the entire surface of the driving substrate. Since the tertiary bonding layer is a conductive metal material, in order to avoid the third light-emitting unit from contacting the electrode contacts other than the third electrode contact and the fourth electrode contact, the tertiary bonding layer in the area other than the third electrode contact and the fourth electrode contact is further etched to remove the tertiary bonding layer.

[0038] An insulating material is deposited across the entire surface until it completely covers the upper surface of the third light-emitting unit, protecting it from external influences. This insulating material fills the spaces between the third light-emitting units and between the tertiary bonding layers on the surface of the fourth electrode contact, providing mutual insulation and preventing leakage. To create a conductive connection between the third light-emitting unit and the fourth electrode contact, vias are etched on the surface of the upper electrode of the third light-emitting unit and at the location of the fourth electrode contact. (Similar to the first light-emitting unit, the vias on the surface of the upper electrode of the third light-emitting unit are centered, ensuring that the metal electrode formed in the subsequent vias is centered on the upper electrode surface, facilitating uniform current distribution within the light-emitting unit. To minimize the obstruction of the light-emitting surface by the metal electrode, the metal electrode should be designed to be as small as possible while maintaining conductivity.) This process continues until the tertiary bonding layer is formed on the surface of the upper electrode of the third light-emitting unit / on the surface of the secondary insulating layer at the location of the fourth electrode contact. The shape of the through-hole can be designed as needed. Metal material is filled in the through-hole that penetrates to the surface of the upper electrode of the third light-emitting unit to form a metal electrode in ohmic contact with the surface of the upper electrode of the third light-emitting unit. Transparent conductive material is prepared on the surface of the insulating material, from the metal electrode on the surface of the upper electrode of the third light-emitting unit to the position of the fourth electrode contact in each group of driving electrodes, forming a transparent electrode layer. At this time, in the longitudinal direction at the position of the fourth electrode contact, a first-level bonding layer 210, a transparent electrode layer 11, a conductive pillar 12, a second-level bonding layer 310, a transparent electrode layer 11, a conductive pillar 12, a tertiary bonding layer 410, and a transparent electrode layer 11 are formed from bottom to top. That is, the fourth electrode contact is connected to the metal electrode 10 on the surface of the upper electrode of the third light-emitting unit 420 through the first-level bonding layer 210, the transparent electrode layer 11, the conductive pillar 12, the second-level bonding layer 310, the transparent electrode layer 11, the conductive pillar 12, the tertiary bonding layer 410, and the transparent electrode layer 11.

[0039] The insulating material is then deposited again until it covers the upper surface of the transparent electrode layer, protecting it. Finally, the upper surface of the tertiary insulating layer is chemically and mechanically polished to planarize it.

[0040] It should be noted that the above embodiments can be freely combined as needed. The above are merely preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A microdisplay chip, characterized by, The application relates to a micro display chip. The driving substrate is provided with a driving circuit on the surface, and the driving circuit is provided with a plurality of groups of driving electrodes arranged closely; Each group of the driving electrodes comprises first, second, third and fourth electrode contacts which are different in position and insulated from each other, the first, second and third electrode contacts are the same type of electrode contacts, the first, second and third electrode contacts are arranged around the fourth electrode contact, and the fourth electrode contact is located in the largest triangle formed by the outer common tangent of the first, second and third electrode contacts; First, second and third light emitting units are respectively bonded on the positions of the first, second and third electrode contacts in the longitudinal direction, and the longitudinal heights of the light emitting surfaces of the first, second and third light emitting units are different; The first, second and third light emitting units comprise upper and lower electrode surfaces, the lower electrode surface of the first light emitting unit is in conductive connection with the first electrode contact, the lower electrode surface of the second light emitting unit is in conductive connection with the second electrode contact, and the lower electrode surface of the third light emitting unit is in conductive connection with the third electrode contact; and the upper electrode surfaces of the first, second and third light emitting units are all in conductive connection with the fourth electrode contact.

2. The microdisplay chip of claim 1, wherein, In the plurality of groups of driving electrodes closely arranged on the surface of the driving substrate, all the first, second and third electrode contacts are arranged in a regular triangular grid array; in each group of the driving electrodes, the first, second and third electrode contacts are respectively located at the three vertices of the regular triangle, and in the transverse direction, the regular triangles formed by the adjacent driving electrode groups face in opposite directions; in the longitudinal direction, the regular triangles formed by the adjacent driving electrode groups face in the same direction.

3. The microdisplay chip of claim 2, wherein, In each group of the driving electrodes, the fourth electrode contact is arranged at the center position of the regular triangle formed by the first, second and third electrode contacts.

4. The micro display chip according to any one of claims 1-3, wherein the longitudinal position of the second light emitting unit is higher than that of the first light emitting unit, and the longitudinal position of the third light emitting unit is higher than that of the second light emitting unit; the first light emitting unit is bonded to the surface of the first electrode contact of the driving substrate through a primary bonding layer, and a primary insulating layer is formed around the first light emitting unit, a first through hole for filling conductive metal is formed at the positions corresponding to the second, third and fourth electrode contacts in the primary insulating layer; the second light emitting unit is bonded to the surface of the first through hole above the second electrode contact through a secondary bonding layer, and a secondary insulating layer is formed around the second light emitting unit, a second through hole for filling conductive metal is formed at the positions corresponding to the third and fourth electrode contacts in the secondary insulating layer; the third light emitting unit is bonded to the surface of the second through hole above the third electrode contact through a tertiary bonding layer, and a tertiary insulating layer is formed around the third light emitting unit. The upper electrode surfaces of the first, second and third light emitting units are formed with metal electrodes, and the first, second and third bonding layers are further formed on the surfaces of the first, second and third through holes above the fourth electrode contacts, and the metal electrodes on the upper electrode surfaces of the light emitting units are conductively connected to the surfaces of the corresponding bonding layers above the fourth electrode contacts through a transparent electrode layer.

5. The microdisplay chip of claim 4, wherein, The metal electrodes on the upper electrode surfaces of the first, second and third light emitting units are formed at the center positions of the upper electrode surfaces of the light emitting units.

6. The micro display chip of claim 4, wherein, The first bonding layer is further formed on the substrate surface at the positions of the second and third electrode contacts, the first through hole at the position of the second electrode contact penetrates through to the surface of the first bonding layer, and the first through hole at the position of the fourth electrode contact penetrates through to the surface of the transparent electrode layer connected to the first light emitting unit; The second bonding layer is further formed on the surface of the first insulating layer at the position of the third electrode contact, the second through hole at the position of the third electrode contact penetrates through to the surface of the second bonding layer, and the second through hole at the position of the fourth electrode contact penetrates through to the surface of the transparent electrode layer connected to the second light emitting unit.

7. The microdisplay chip of claim 4, wherein, The first, second and third insulating layers are formed with flat upper surfaces.

8. A method of fabricating a microdisplay chip, comprising: The method comprises: S10 providing a driving substrate, the surface of the driving substrate being provided with a driving circuit, and the surface of the driving circuit being provided with a plurality of groups of closely arranged driving electrodes; Each group of the driving electrodes comprises first, second, third and fourth electrode contacts at different positions and insulated from each other, the first, second and third electrode contacts being the same type of electrode contacts, the first, second and third electrode contacts being arranged around the fourth electrode contact, and the fourth electrode contact being located within the largest triangle formed by the outer common tangent of the first, second and third electrode contacts; S20 bonding a first semiconductor light emitting structure on the surface of the driving substrate, and etching the first semiconductor light emitting structure to form a first light emitting unit at the position of the first electrode contact; The lower electrode surface of the first light emitting unit is conductively connected to the first electrode contact, a transparent electrode layer is formed from the metal electrode on the upper electrode surface of the first light emitting unit to the surface of the bonding layer at the corresponding position of the fourth electrode contact, and an insulating material is filled to cover the first light emitting unit and the transparent electrode layer and to planarize the upper surface to form a first insulating layer; S30 bonding a second semiconductor light emitting structure on the surface of the first insulation layer, etching the second semiconductor light emitting structure, and forming a second light emitting unit in the longitudinal direction at the position of the second electrode contact; the lower electrode surface of the second light emitting unit is in conductive connection with the second electrode contact, a transparent electrode layer is formed from the metal electrode on the upper electrode surface of the second light emitting unit to the surface of the bonding layer at the corresponding position of the fourth electrode contact, and an insulation material is filled to cover the second light emitting unit and the transparent electrode layer and to form a second insulation layer by planarizing the upper surface. S40 bonding a third semiconductor light emitting structure on the surface of the second insulation layer, etching the third semiconductor light emitting structure, and forming a third light emitting unit in the longitudinal direction at the position of the third electrode contact; the lower electrode surface of the third light emitting unit is in conductive connection with the third electrode contact, a transparent electrode layer is formed from the metal electrode on the upper electrode surface of the third light emitting unit to the surface of the bonding layer at the corresponding position of the fourth electrode contact, and an insulation material is filled to cover the third light emitting unit and the transparent electrode layer and to form a third insulation layer by planarizing the upper surface.

9. The method of claim 8, wherein the microdisplay chip is prepared by a method comprising: In the plurality of groups of driving electrodes closely arranged on the surface of the driving substrate, all the first electrode contacts, the second electrode contacts, and the third electrode contacts are arranged in a regular triangular grid array; in each group of driving electrodes, the first electrode contact, the second electrode contact, and the third electrode contact are located at the three vertices of a regular triangle, respectively, and in the lateral direction, the regular triangles formed by adjacent groups of driving electrodes face in opposite directions; in the longitudinal direction, the regular triangles formed by adjacent groups of driving electrodes face in the same direction. ​ 10. The method of claim 9, wherein the microdisplay chip is prepared by a method comprising: In each group of driving electrodes, the fourth electrode contact is arranged at the center of the regular triangle formed by the first electrode contact, the second electrode contact, and the third electrode contact. ​ 11. The method of claim 8 or 9 or 10, wherein the microdisplay chip is prepared by a method comprising: In the S20 step, it includes: ​ providing a first semiconductor structure, forming a first bonding layer on the surface of the driving substrate, and bonding the first semiconductor structure to the surface of the substrate; etching and removing the first semiconductor structure except at the position of the first electrode contact, forming a first light emitting unit at the position of the first electrode contact of each group of driving electrodes; and further etching and removing the first bonding layer between the electrode contacts; depositing an insulation material to cover the upper surface of the first light emitting unit, etching the insulation material at the positions of the first light emitting unit and the fourth electrode contact to expose the upper electrode surface of the first light emitting unit and the upper surface of the first bonding layer to form a through hole; depositing a conductive metal in the through hole extending to the upper electrode surface of the first light emitting unit to form a metal electrode, and extending the metal electrode on the upper electrode surface of the first light emitting unit to the surface of the first bonding layer in the through hole at the corresponding position of the fourth electrode contact to form a transparent electrode layer; depositing an insulation material to cover the transparent electrode layer, etching the insulation material in the longitudinal direction at the positions corresponding to the second electrode contact, the third electrode contact, and the fourth electrode contact to expose the first bonding layer / transparent electrode layer to form a first through hole, and filling the first through hole with a conductive metal to form a conductive column.

12. The method of claim 8 or 9 or 10, wherein the microdisplay chip is prepared by a method comprising: In the S30 step, it includes: ​ A second semiconductor structure is provided, a second bonding layer is formed on the surface of a first insulating layer, and the second semiconductor structure is bonded to the surface of the substrate; the second semiconductor structure is etched to remove the second semiconductor structure except the position of the second electrode contact, and a second light emitting unit is formed at the position of the second electrode contact of each group of driving electrodes in the longitudinal direction; and the second bonding layer between the first light emitting unit and the second light emitting unit in the longitudinal direction and between each electrode contact is further etched and removed; An insulating material is deposited on the surface of the second light emitting unit to cover the second light emitting unit, and the insulating material is etched at the positions of the second light emitting unit and the fourth electrode contact to expose the upper electrode surface of the second light emitting unit and the upper surface of the second bonding layer to form a through hole; A conductive metal is deposited in the through hole to form a metal electrode, and a transparent electrode layer is formed on the surface of the second bonding layer in the through hole corresponding to the position of the fourth electrode contact from the metal electrode on the upper electrode surface of the second light emitting unit; An insulating material is deposited on the transparent electrode layer to cover the transparent electrode layer, and the insulating material is etched at the positions of the third electrode contact and the fourth electrode contact in the longitudinal direction to expose the second bonding layer / transparent electrode layer to form a second through hole, and a conductive metal is filled in the second through hole to form a conductive column.

13. The method of claim 8 or 9 or 10, wherein the microdisplay chip is prepared by a method comprising: In step S40, it includes: ​ A third semiconductor structure is provided, a third bonding layer is formed on the surface of a second insulating layer, and the third semiconductor structure is bonded to the surface of the substrate; the third semiconductor structure is etched to remove the third semiconductor structure except the position of the third electrode contact, and a third light emitting unit is formed at the position of the third electrode contact of each group of driving electrodes in the longitudinal direction; and the third bonding layer between the first light emitting unit and the second light emitting unit in the longitudinal direction and between each electrode contact is further etched and removed; An insulating material is deposited on the surface of the third light emitting unit to cover the third light emitting unit, and the insulating material is etched at the positions of the third light emitting unit and the fourth electrode contact to expose the upper electrode surface of the third light emitting unit and the upper surface of the second bonding layer to form a through hole; A conductive metal is deposited in the through hole to form a metal electrode, and a transparent electrode layer is formed on the surface of the third bonding layer in the through hole corresponding to the position of the fourth electrode contact from the metal electrode on the upper electrode surface of the third light emitting unit; An insulating material is deposited on the transparent electrode layer to cover the transparent electrode layer.

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