Display device and method of forming the same

Abstract

In some embodiments of the present invention, a display device is provided, the display device comprising: an isolation structure disposed on a reflector electrode; a transparent electrode disposed on the isolation structure; an optical emitter structure disposed on the transparent electrode; and a through-hole structure. The through-hole structure extends from the transparent electrode to the top surface of the reflector electrode at the top surface of the isolation structure. The through-hole structure comprises a central horizontal segment in contact with the top surface of the reflector electrode, a sidewall vertical segment in contact with the inner sidewall of the isolation structure, and an upper horizontal segment connected to the central horizontal segment through the sidewall vertical segment. The upper horizontal segment is thicker than the central horizontal segment.

Description

Technical Field

[0001] The present invention relates to a display device and a method for forming the same. Background Art

[0002] Many modern electronic devices, such as televisions and cellular devices, use image display devices to convert digital data into optical images. To achieve this purpose, the image display device may include an array of pixel regions. Each pixel region may have an optical emitter structure and may be coupled to a semiconductor device. The semiconductor device may selectively apply an electrical signal (e.g., a voltage) to the optical emitter structure. After applying the electrical signal, the optical emitter structure may emit an optical signal (e.g., light). For example, the optical emitter structure may be an organic light emitting diode (OLED) or some other suitable light emitting device. Summary of the invention

[0003] In some embodiments, the present invention relates to a display device, which includes: an isolation structure arranged on a reflector electrode; a transparent electrode arranged on the isolation structure; an optical emitter structure arranged on the transparent electrode; and a through-hole structure extending from the transparent electrode to the top surface of the reflector electrode at the top surface of the isolation structure, wherein the through-hole structure includes a central horizontal segment in contact with the top surface of the reflector electrode, a side wall vertical segment in contact with the inner side wall of the isolation structure, and an upper horizontal segment in contact with the top surface of the isolation structure, wherein the upper horizontal segment is connected to the central horizontal segment through the side wall vertical segment, and wherein the upper horizontal segment is thicker than the central horizontal segment.

[0004] In other embodiments, the present invention relates to a display device, comprising: a reflector electrode coupled to an internal connection structure; an isolation structure disposed above the reflector electrode; a transparent electrode disposed above the isolation structure; an optical emitter structure disposed above the transparent electrode; and a through-hole structure extending from the top surface of the isolation structure to the reflector electrode, wherein the through-hole structure comprises a first layer located on the top surface of the isolation structure and further comprises a second layer, wherein the second layer is suspended above the top surface of the isolation structure and is separated from the top surface of the isolation structure by the first layer, and wherein the second layer has a downward protrusion that directly contacts the reflector electrode and directly contacts the inner side wall of the isolation structure.

[0005] In another embodiment, the present invention relates to a method for forming a display device, the method comprising: forming an isolation structure over a reflector electrode; depositing a protective layer over the isolation structure; forming a first opening extending through the protective layer and the isolation structure to expose the first surface of the reflector electrode, wherein the inner sidewalls of the protective layer and the inner sidewalls of the isolation structure define the sidewalls of the first opening; performing a cleaning process to clean the first surface of the reflector electrode; depositing a conductive layer over the protective layer, the sidewalls of the first opening, and the first surface of the reflector electrode; and performing an etching process to remove a peripheral portion of the protective layer and a peripheral portion of the conductive layer, thereby forming a through-hole structure including the protective layer and the conductive layer, wherein the through-hole structure directly contacts the top surface of the isolation structure and the first surface of the reflector electrode and extends from the top surface of the isolation structure to the first surface of the reflector electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The various aspects of the present invention can be best understood by reading the following detailed description in conjunction with the accompanying drawings. Note that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0007] Figure 1A and Figure 1B Cross-sectional views illustrating some embodiments of a display device having a via structure extending through an isolation structure, the via structure having an upper horizontal section that is thicker than a center horizontal section.

[0008] Figure 2 Cross-sectional views illustrating some additional embodiments of display devices having a via structure including two layers and extending through an isolation structure and having exemplary light paths through isolation structures of varying thicknesses.

[0009] Figures 3 to 12 Cross-sectional views illustrating some embodiments of methods of forming a display device having a via structure extending through an isolation structure, wherein the via structure includes a protective layer and a conductive layer to prevent damage to the isolation structure.

[0010] Fig.13 Description and Figures 3 to 12 Flowcharts of some embodiments of the corresponding methods. DETAILED DESCRIPTION

[0011] The following disclosure provides many different embodiments or examples to implement the different features of the provided subject matter. Specific examples of components and arrangements are described below to make the present invention concise. Of course, these are only examples and are not intended to be limiting. For example, in the following description, a first feature formed on or formed on a second feature may include an embodiment in which the first feature and the second feature are formed to be in direct contact, and may also include an embodiment in which an additional feature may be formed between the first feature and the second feature so that the first feature and the second feature cannot be in direct contact. In addition, the present invention may reuse reference numbers and / or letters in various examples. This repetition is for the purpose of simplicity and clarity, and does not essentially specify the relationship between the various embodiments and / or configurations described.

[0012] Additionally, for ease of description, spatially relative terms, such as "beneath," "below," "lower," "above," "upper," etc., may be used herein to describe the relationship of one element or feature to another element or feature, as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0013] The display device includes an array of pixel regions, wherein each pixel region includes an isolation structure arranged between a reflector electrode and a transparent electrode. A through-hole structure may extend through the thickness of the isolation structure and electrically couple the reflector electrode to the transparent electrode. An optical emitter structure may be arranged above the transparent electrode. The isolation structure may include silicon dioxide having a thickness corresponding to a certain color. For example, during operation of the display device, an electrical signal (e.g., a voltage) may be applied to the transparent electrode from a circuit system that is coupled to the reflector electrode, the through-hole structure, and the transparent electrode. The electrical signal may cause light to be generated at the interface between the optical emitter structure and the transparent electrode (e.g., due to electron-hole recombination). The light may be reflected by the top surface of the isolation structure and / or may travel through the isolation structure, be reflected by the reflector electrode, and travel back toward the top surface of the isolation structure. Since light of a given wavelength undergoes constructive and / or destructive interference at the top surface of the isolation structure, colored light according to the thickness of the isolation structure may be emitted from the top surface of the optical emitter structure.

[0014] To form a through-hole structure, an isolation structure may be formed, for example, on the reflector electrode, and an opening may be formed in the isolation structure to expose the first surface of the reflector electrode. The opening may be formed using an etching process, which may leave residues (e.g., metal oxides) on the first surface of the reflector electrode. Therefore, a cleaning process (e.g., an argon sputtering process) is performed to remove the residues from the first surface of the reflector electrode. If the cleaning process is not performed, the through-hole structure may have poor electrical contact with the first surface (e.g., the contact resistance may be high). However, the cleaning process may damage the upper surface of the isolation structure (e.g., increase the surface roughness). Since the upper surface of the isolation structure receives and reflects light, when the upper surface of the isolation structure is damaged, the light may be scattered, which may, for example, cause the emitted light to be a different color and / or reduce the intensity of the emitted light. Therefore, the cleaning process may cause the display device to be unreliable.

[0015] Various embodiments of the present invention relate to a method for forming a through-hole structure, the through-hole structure including a protective layer and a conductive layer located on an isolation structure to prevent damage to the isolation structure of a display device. In some embodiments, a protective layer is deposited on the isolation structure located on a reflector electrode so that the protective layer directly contacts the top surface of the isolation structure. A first etching process may be performed to form a first opening in the protective layer and the isolation structure to expose the first surface of the reflector electrode. A cleaning process may be performed to remove any residue on the first surface of the reflector electrode. Then, a conductive layer is deposited on the protective layer, on the sidewalls of the first opening defined by the inner sidewalls of the isolation structure, and on the first surface of the reflector electrode. A second etching process may be performed to remove the peripheral portion of the protective layer and the peripheral portion of the conductive layer, thereby forming a through-hole structure. The through-hole structure includes: a central segment directly contacting the reflector electrode; a sidewall segment connected to the central segment and extending upward toward the top surface of the isolation structure; and an upper horizontal segment connected to the sidewall segment and directly contacting the top surface of the isolation structure. The horizontal segment includes a protective layer and a conductive layer, and thus the horizontal segment may be thicker than the central segment. Since the protection layer is deposited on the isolation structure, the top surface of the isolation structure is protected during the cleaning process, thereby reducing damage to the top surface of the isolation structure and producing a reliable display device.

[0016] Figure 1A A cross-sectional view 100A of some embodiments of a display device is illustrated that includes a via structure extending through an isolation structure.

[0017] The display device of the cross-sectional view 100A includes a first pixel region 101a, a second pixel region 101b, and a third pixel region 101c. Each of the first pixel region 101a, the second pixel region 101b, and the third pixel region 101c is configured to emit light of different colors (e.g., red, green, blue) when receiving an electrical signal (e.g., voltage), and the color of the light depends on the thickness of the isolation structure 106. For example, in some embodiments, the first pixel region 101a may include a first portion 106a of the isolation structure 106 having a first thickness t1; the second pixel region 101b may include a second portion 106b of the isolation structure 106 having a second thickness t2; and the third pixel region 101c may include a third portion 106c of the isolation structure 106 having a third thickness t3. In some embodiments, the first thickness t1, the second thickness t2, and the third thickness t3 are each different from each other. For example, in some embodiments, the first thickness t1 may be greater than the second thickness t2 and the third thickness t3, and the second thickness t2 may be greater than the third thickness t3. In some embodiments, the isolation structure 106 may include an oxide (e.g., silicon dioxide), a nitride (e.g., silicon nitride), or some other material having optical properties such that incident light may be reflected as colored light due to constructive and / or destructive interference, and wherein the color of the colored light depends on the thickness of the isolation structure 106. For example, the first thickness t1 may correspond to green light; the second thickness t2 may correspond to blue light; and the third thickness t3 may correspond to red light.

[0018] In some embodiments, the isolation structure 106 is arranged between the reflector electrode 102 and the transparent electrode 112. The first blocking structure 104 can be arranged between portions of the reflector electrode 102 so that each pixel region 101a, 101b, 101c includes an electrically isolated portion of the reflector electrode 102. In some embodiments, the optical emitter structure 110 can be arranged above the transparent electrode 112. Furthermore, in some embodiments, the second blocking structure 114 can be arranged above the isolation structure 106 and between portions of the optical emitter structure 110 and portions of the transparent electrode 112 to isolate the first pixel region 101a, the second pixel region 101b, and the third pixel region 101c from each other.

[0019] In some embodiments, the reflector electrode 102 can be coupled to the control circuit system 120. For example, in some embodiments, the reflector electrode 102 is disposed on an interconnect structure 130, which includes a network of interconnect wires 134 and interconnect vias 136 embedded in the interconnect dielectric structure 132. In some embodiments, the interconnect structure 130 is arranged on the substrate 122 and coupled to the semiconductor device 124. In some embodiments, the semiconductor device 124 can be, for example, a metal oxide semiconductor field-effect transistor (MOSFET), which includes a source / drain region 124a located in the substrate 122 and a gate electrode 124b located on the substrate 122. The gate electrode 124b and the substrate 122 can be separated by a gate dielectric layer 124c. The control circuit system 120 is configured to selectively supply an electrical signal (eg, voltage) to each of the first pixel region 101a, the second pixel region 101b, and the third pixel region 101c to cause the pixel region to emit color light indicated by the digital data.

[0020] In some embodiments, each of the first pixel region 101a, the second pixel region 101b, and the third pixel region 101c includes a through-hole structure 108 so that an electrical signal (e.g., voltage) can be supplied to the transparent electrode 112 and the optical emitter structure 110. The electrical signal (e.g., voltage) can, for example, cause electron-hole recombination to occur between the transparent electrode 112 and the optical emitter structure 110 to generate light, and the light can be reflected by the top surface of the isolation structure 106 and / or travel through the isolation structure 106, reflected by the reflector electrode 102 and exit through the top surface of the isolation structure 106. Colored light according to the thickness of the isolation structure 106 is emitted due to constructive and / or destructive interference.

[0021] In some embodiments, the via structure 108 extends from the top surface 106t of the isolation structure 106 and extends downward toward the first surface 102f of the reflector electrode 102, thereby electrically coupling the reflector electrode 102 to the transparent electrode 112. The first surface 102f of the reflector electrode 102 may be the top surface of the reflector electrode 102. In some embodiments, the via structure 108 has a fourth thickness t4 along the first surface 102f of the reflector electrode, and the via structure 108 has a fifth thickness t5 along the top surface 106t of the isolation structure 106. In some embodiments, since the via structure 108 may include multiple layers along the top surface 106t of the isolation structure 106 (see Figure 1B), so the fifth thickness t5 is greater than the fourth thickness t4, and the plurality of layers are included because the top surface 106t of the isolation structure 106 is protected during the manufacture of the through-hole structure 108 to produce a reliable display device.

[0022] Figure 1B Description and Figure 1A Box B corresponds to the cross-sectional view 100B of some embodiments.

[0023] In some embodiments, the via structure 108 may be described as including: a central horizontal segment 108c in contact with the first surface 102f of the reflector electrode 102; a sidewall vertical segment 108s in contact with the inner sidewall 106s of the isolation structure 106; and an upper horizontal segment 108u in contact with the top surface 106t of the isolation structure 106, wherein the sidewall vertical segment 108s connects the upper horizontal segment 108u to the central horizontal segment 108c. In some embodiments, from the cross-sectional view 100B, there are two upper horizontal segments 108u separated from each other by the transparent electrode 112, and there are two sidewall vertical segments 108s separated from each other by the transparent electrode 112. In some embodiments, the upper horizontal segment 108u includes a conductive layer 108b located above the protective layer 108a, and the sidewall vertical segment 108s and the central horizontal segment 108c include the conductive layer 108b but not the protective layer 108a.

[0024] In some embodiments, the protective layer 108a and the conductive layer 108b may each include a conductive material. In an alternative embodiment, the protective layer 108a is a dielectric material different from the isolation structure 106, rather than a conductive metal. However, this may result in a degradation of the electrical coupling with the transparent electrode 112 at the sidewall of the through-hole structure 108. In some embodiments, the protective layer 108a and the conductive layer 108b include the same conductive material, while in other embodiments, the protective layer 108a and the conductive layer 108b may include different conductive materials. For example, in some embodiments, the protective layer 108a and the conductive layer 108b may include the same material such as titanium nitride. Therefore, in some embodiments, the protective layer 108a and the conductive layer 108b cannot be distinguished from each other. However, since the upper horizontal segment 108u has a fifth thickness t5 greater than the fourth thickness t4 of the central horizontal segment 108c, the presence of the protective layer 108a can be detected. In some embodiments, the fourth thickness t4 may be described as being measured from the bottommost surface of the via structure 108 to the bottommost surface of the transparent electrode 112 .

[0025] Similarly, in some embodiments, the fifth thickness t5 may be described as being measured from the top surface 106t of the isolation structure 106 to the topmost surface of the through-hole structure 108. In some embodiments, the fourth thickness t4 is measured in a first direction orthogonal to the first surface 102f of the reflector electrode 102, and the fifth thickness t5 is also measured in the first direction. The difference between the fifth thickness t5 and the fourth thickness t4 may be equal to the thickness of the protective layer 108a. In addition, the sidewall vertical section 108s may have a sixth thickness t6 measured in a second direction perpendicular to the first direction. In some embodiments, the sixth thickness t6 may be described as being measured between the inner sidewall 106s of the isolation structure 106 and the inner sidewall of the transparent electrode 112. In some embodiments, the fifth thickness t5 is greater than each of the fourth thickness t4 and the sixth thickness t6. In addition, in some embodiments, the fourth thickness t4 is approximately equal to the sixth thickness t6.

[0026] In some embodiments, the fourth thickness t4 and the sixth thickness t6 may each be in a range of, for example, between about 200 angstroms and about 700 angstroms. In some embodiments, the fifth thickness t5 may be in a range of, for example, between 300 angstroms and about 1000 angstroms. Thus, in some embodiments, the difference between the fourth thickness t4 and the fifth thickness t5 may be at least equal to 100 angstroms. In addition, in some embodiments, the ratio of the fifth thickness t5 to the fourth thickness t4 may be at least equal to about 1.15.

[0027] Figure 2 A cross-sectional view 200 of some embodiments of a display device including a via structure extending through an isolation structure and various light paths is illustrated during operation of the display device.

[0028] In some embodiments, the via structure 108 may completely and continuously fill the space laterally located between the inner sidewalls 106s of the isolation structure 106 in each pixel region (101a, 101b, 101c). In these embodiments, the via structure 108 may still include the protection layer 108a and the conductive layer 108b. In addition, in some embodiments, the conductive layer 108b may extend from above the top surface 106t of the isolation structure 106 and to the top surface 102t of the reflector electrode 102, while the protection layer 108a may directly contact the top surface 106t of the isolation structure 106 and be arranged on the top surface 106t of the isolation structure 106. The protection layer 108a does not extend below the top surface 106t of the isolation structure 106.

[0029] In some embodiments, the first pixel region 101a, the second pixel region 101b, and the third pixel region 101c each include a reflector electrode having substantially equal widths ( Figure 1A 102). However, in other embodiments, such as in Figure 2In the cross-sectional view 200 of , the first pixel region 101a may have a first reflector electrode portion 102a having a first width w1; the second pixel region 101b may have a second reflector electrode portion 102b having a second width w2; and the third pixel region 101c may have a third reflector electrode portion 102c having a third width w3. In these embodiments, the first width w1, the second width w2, and the third width w3 may be different from each other. For example, in some embodiments, the third width w3 may be smaller than the second width w2, and the second width w2 may be smaller than the first width w1. In some embodiments, the minimum width (e.g., w3) corresponds to the pixel region (e.g., 101c) having a portion of the isolation structure 106 with the smallest thickness (e.g., t3). Similarly, in some embodiments, the maximum width (e.g., w1) corresponds to the pixel region (e.g., 101a) having a portion of the isolation structure 106 with the largest thickness (e.g., t1). However, in other embodiments, the relationship between the widths of the reflector electrode 102 has no correlation with the thickness of the isolation structure 106.

[0030] Cross-sectional view 200 illustrates an exemplary first light path 202 in the second pixel region 101b and an exemplary second light path 204 in the third pixel region 101c. In some embodiments, light is generated at a first interface 206 between the optical emitter structure 110 and the transparent electrode 112 due to the control circuit system 120 applying an electrical signal (e.g., a voltage) to the reflector electrode 102. For example, in cross-sectional view 200, the second pixel region 101b and the third pixel region 101c are "ON" (e.g., light is generated at the first interface 206), while the first pixel region 101a is "OFF" (e.g., light is not generated at the first interface 206). In the second pixel region 101b, the exemplary first light path 202 illustrates how, in some embodiments, light generated at the first interface 206 may be reflected by the top surface 106t of the second portion 106b of the isolation structure 106 and / or travel through the second portion 106b of the isolation structure 106, be reflected by the second reflector electrode portion 102b, and travel back up toward the top surface 106t of the second portion 106b of the isolation structure 106. Due to constructive and / or destructive interference, only colored light having the first wavelength associated with the second thickness t2 of the second portion 106b of the isolation structure 106 will be emitted from / observed from the top surface of the optical emitter structure 110 located in the second pixel region 101b.

[0031] Similarly, in the third pixel region 101c, the exemplary second light path 204 illustrates how, in some embodiments, light generated at the first interface 206 may be reflected by the top surface 106t of the third portion 106c of the isolation structure 106 and / or travel through the third portion 106c of the isolation structure 106, be reflected by the third reflector electrode portion 102c, and travel back up toward the top surface 106t of the third portion 106c of the isolation structure 106. Due to constructive and / or destructive interference, the top surface of the optical emitter structure 110 located in the third pixel region 101c will only emit / observe from the top surface only colored light having a second wavelength associated with the third thickness t3 of the third portion 106c of the isolation structure 106. In some embodiments, because the third thickness t3 of the third portion 106c of the isolation structure 106 is different from the second thickness t2 of the second portion 106b of the isolation structure 106, the second wavelength will be different from the first wavelength, and thus the third pixel region 101c emits different colored light than the second pixel region 101b. Thus, control circuitry 120 may use the digital data to selectively turn on one or more of the pixel regions (eg, 101a, 101b, 101c) to produce an optical image.

[0032] Figures 3 to 12 Cross-sectional views 300 to 1200 of some embodiments illustrate a method of forming a via structure over an isolation structure of a display device, the via structure having a protective layer to prevent damage to the isolation structure. Figures 3 to 12 , it should be understood, but Figures 3 to 12 The structure disclosed in is not limited to this method, but can exist as a structure independently of the method.

[0033] like Figure 3As shown in the cross-sectional view 300 of FIG. 1 , the reflector electrode 102 may be formed on the control circuit system 120. In some embodiments, the control circuit system 120 may include an interconnect structure 130 arranged on the substrate 122. The interconnect structure 130 may include an interconnect wire 134 and an interconnect via 136 embedded in the interconnect dielectric structure 132. In some embodiments, the interconnect wire 134 and the interconnect via 136 may include copper, tungsten, etc. The interconnect structure 130 may couple the reflector electrode 102 to a semiconductor device 124, which is integrated on the substrate 122. In some embodiments, the semiconductor device 124 may be or include a metal oxide semiconductor field effect transistor (MOSFET), wherein the metal oxide semiconductor field effect transistor includes a source / drain region 124a located in the substrate 122. The semiconductor device 124 may also include a gate electrode 124b, which is arranged on a gate dielectric layer 124c located on the substrate 122. In alternative embodiments, the reflector electrode 102 may be formed over a carrier substrate and then later formed before forming a pixel region (eg, Figure 1A After that, the reflector electrode 102 is removed from the carrier substrate and bonded to the control circuit system ( Figure 1A of 120).

[0034] In some embodiments, the first blocking structure 104 may separate the reflector electrode 102 so that the reflector electrode 102 has, for example, a first reflector electrode portion 102a, a second reflector electrode portion 102b, and a third reflector electrode portion 102c. In some embodiments, the first blocking structure 104 comprises the same material as the interconnect dielectric structure 132. The reflector electrode 102 may comprise a metal that is both conductive and reflective. For example, in some embodiments, the reflector electrode 102 may comprise aluminum or aluminum copper. In some embodiments, the first blocking structure 104 may be formed using a deposition process (e.g., physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PE-CVD), atomic layer deposition (ALD), sputtering, etc.) followed by a patterning process (e.g., photolithography and etching). Then, a deposition process (e.g., physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition, atomic layer deposition (ALD), sputtering, etc.) may be used, followed by a patterning process (e.g., photolithography, etching, chemical mechanical planarization (CMP), etc.) to form the reflector electrode 102 on the interconnect dielectric structure 132.

[0035] Furthermore, an isolation structure 106 is formed over the reflector electrode 102. In some embodiments, the isolation structure 106 includes a first portion 106a, a second portion 106b, and a third portion 106c having a first thickness t1, a second thickness t2, and a third thickness t3, respectively. The thicknesses (t1, t2, t3) may be determined based on the material of the isolation structure 106 and a predetermined light color to be emitted from each portion (106a, 106b, 106c) of the isolation structure 106. In some embodiments, the isolation structure 106 includes a material having optical properties such that incident light may be reflected as colored light due to constructive and / or destructive interference, and wherein the color of the colored light depends on the thickness of the isolation structure 106. Non-limiting examples of such materials include silicon nitride and silicon dioxide. Furthermore, each portion (106a, 106b, 06c) of the isolation structure 106 may be continuously connected to each other. In some embodiments, the formation of the isolation structure 106 may include a deposition process step (e.g., physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition, atomic layer deposition (ALD), sputtering, etc.) and a patterning process step (e.g., photolithography / etching process). In some embodiments, the first barrier structure 104 includes the same material as the isolation structure 106. In addition, in some embodiments, the first barrier structure 104, the interconnect dielectric structure 132, and the isolation structure 106 include the same material. In other embodiments, the first barrier structure 104 and / or the interconnect dielectric structure 132 may include a dielectric material, such as undoped silicate glass (USG), silicon nitride, etc. In some embodiments, the first thickness t1, the second thickness t2, and the third thickness t3 of the isolation structure 106 may each be in a range of, for example, between about 200 angstroms and about 1500 angstroms.

[0036] like Figure 4 As shown in the cross-sectional view 400 of , in some embodiments, a conformal protective layer 402 is deposited over the isolation structure 106. In some embodiments, the conformal protective layer 402 has a seventh thickness t7 in a range of, for example, between about 100 angstroms and about 300 angstroms. The conformal protective layer 402 may be deposited by a deposition process (e.g., physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition, atomic layer deposition (ALD), sputtering, etc.). In some embodiments, the conformal protective layer 402 may include a conductive metal, such as titanium nitride or tantalum nitride. In an alternative embodiment, the conformal protective layer 402 may be replaced by a conformal dielectric layer. The conformal protective layer 402 includes a dielectric layer that resists a cleaning process used later (see Figure 7 Similarly, the seventh thickness t7 of the conformal protection layer 402 is thick enough to be used in a cleaning process (see Figure 7702) during the cleaning process (see Figure 7 702) causes the top surface 106t of the isolation structure 106 to be exposed.

[0037] like Figure 5 As shown in the cross-sectional view 500 of , in some embodiments, a first masking layer 502 may be formed over the conformal protective layer 402. The first masking layer 502 may include a first opening 504. In some embodiments, each of the first openings 504 may be arranged over each portion (106a, 106b, 106c) of the isolation structure 106. In some embodiments, the first masking layer 502 may be formed by photolithography and may include a photosensitive material (e.g., photoresist) formed by a spin coating process. In these embodiments, the photosensitive material layer is selectively exposed to electromagnetic radiation according to a photomask or a photomask. The electromagnetic radiation changes the solubility of the exposed area within the photosensitive material to define a soluble area. Subsequently, the photosensitive material is developed to define the first opening 504 in the photosensitive material by removing the soluble area. In other embodiments, the first masking layer 502 may include a hard mask layer (e.g., a silicon nitride layer, a carbide layer, etc.), which is patterned by, for example, a photolithography / etching process or some other suitable patterning process.

[0038] like Figure 6 As shown in the cross-sectional view 600 of FIG. 1 , a first etching process 602 may be performed to remove the conformal protection layer 402 and the first opening ( 200 ) of the isolation structure 106 located in the first masking layer 502. Figure 5 504), thereby forming a second opening 604 in the isolation structure 106. In some embodiments, the second opening 604 has a fourth width w4 in a range, for example, between about 0.1 microns and about 0.6 microns. The bottom of the second opening 604 can be defined by the first surface 606 of the reflector electrode 102, and the sidewalls of the second opening 604 can be defined by the inner sidewalls 106s of the isolation structure 106. In some embodiments, the first etching process 602 is a dry etching process, and a residue 608 remains on the first surface 606 of the reflector electrode 102. The residue may include, for example, a metal oxide, including the material of the isolation structure 106, the material of the reflector electrode 102, and / or the material of the conformal protective layer 402.

[0039] like Figure 7 As shown in the cross-sectional view 700 of FIG. 7 , the first masking layer ( Figure 6 502), and a cleaning process 702 may be performed on the isolation structure 106 to remove residues on the first surface 606 of the reflector electrode 102 ( Figure 6608). In some embodiments, the cleaning process 702 may be or include an argon sputtering process. In addition, in these embodiments, during the cleaning process 702, the top surface 106t of the isolation structure 106 is covered by the conformal protection layer 402. Therefore, the top surface 106t of the isolation structure 106 is protected by the conformal protection layer 402 and prevents the cleaning process 702 from damaging the isolation structure 106. Since the top surface 106t is used to reflect light during the operation of the display device (see Figure 2 ), so preventing damage to the top surface 106t of the isolation structure (e.g., increasing the surface roughness, changing the composition, etc.) is critical to a reliable display device. Therefore, due to the presence of the conformal protection layer 402, during the cleaning process 702 (e.g., Figure 6 ), the isolation structure 106 may have a top surface 106t with a first average surface roughness before cleaning process 702, and after cleaning process 702, the top surface 106t may have a second average surface roughness that is the same as the first average surface roughness. In some embodiments, to measure the average surface roughness, a roughness measurement tool (e.g., a profilometer, AFM) calculates a mean line along the surface and measures the deviation of the height of a peak or valley on the surface from the mean line. After measuring many deviations at the peaks and valleys on the entire surface, the average surface roughness is calculated by taking the average of the many deviations, wherein the deviation is an absolute value. In other embodiments, the surface roughness is quantified by measuring the total thickness variation (TTV). The total thickness variation of a layer is the difference between the minimum thickness and the maximum thickness of the layer. The total thickness variation is measured over the entire length of the layer.

[0040] like Figure 8 As shown in the cross-sectional view 800 of FIG. 8 , the conformal protective layer 402 may be formed on the second opening ( Figure 7 A conformal conductive layer 802 is deposited on the sidewalls and bottom of the conformal protective layer 404. In some embodiments, the conformal conductive layer 802 has a fourth thickness t4 in a range of, for example, between about 200 angstroms and about 700 angstroms. In other embodiments, the fourth thickness t4 may be in a range of, for example, between about 100 angstroms and about 900 angstroms. In some embodiments, the fourth thickness t4 is greater than the seventh thickness t7 of the conformal protective layer 402, while in other embodiments, the fourth thickness t4 may be less than or approximately equal to the seventh thickness t7. In addition, the conformal conductive layer 802 may not fill the second opening ( Figure 7 604), and thus the third opening 804 may still exist between the inner sidewalls 106s of the isolation structure 106. In other words, twice the fourth thickness t4 is smaller than the second opening ( Figure 7 The fourth width (604) Figure 6In an alternative embodiment, the conformal conductive layer 802 may completely fill the second opening ( Figure 7 604), so there is no third opening 804. (Participate Figure 2 Therefore, in an alternative embodiment, the fourth thickness t4 may be greater than the second opening ( Figure 7 The fourth width (604) Figure 6 In these alternative embodiments, conformal conductive layer 802 may have an upper surface with a small indentation that overlies first surface 606 of reflector electrode 102.

[0041] In addition, in some embodiments, conformal conductive layer 802 may include a conductive metal, such as titanium nitride or tantalum nitride. Therefore, in some embodiments, conformal protective layer 402 and conformal conductive layer 802 include the same material. In other embodiments, conformal conductive layer 802 may include a different material than conformal protective layer 402. Figure 7 702) Remove the residue ( Figure 8 608), so the conformal conductive layer 802 can directly contact the first surface 606 of the reflector electrode 102. The direct contact between the conformal conductive layer 802 and the reflector electrode 102 allows a reliable electrical connection to be achieved. The conformal conductive layer 802 can be deposited by a deposition process (e.g., physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition, atomic layer deposition (ALD), sputtering, etc.).

[0042] like Fig. 9 As shown in the cross-sectional view 900 of FIG. 8 , above the conformal conductive layer 802 and in the third opening ( Figure 8 The second masking layer 902 may overlie some portions of the top surface 802t of the conformal conductive layer 802. It should be understood that the second masking layer 902 may be formed within the conformal conductive layer 804. Figure 5 The second masking layer is formed by a photolithography process similar to the photolithography process of the first masking layer 502.

[0043] like Fig.10 As shown in the cross-sectional view 1000 of FIG. 1 , a second etching process 1002 may be performed based on the second masking layer 902 to remove the conformal protection layer ( Fig. 9 402) and the peripheral portion of the conformal conductive layer ( Fig. 9 The peripheral portion of the through hole structure 108 is formed by etching the through hole structure 108. The through hole structure 108 may include a protective layer 108a and a conductive layer 108b. In some embodiments, the second etching process 1002 includes a wet etching process instead of a dry etching process to remove the conformal protective layer ( Fig. 9The second etching process 1002 can reduce the damage of the residue to the top surface 106t of the isolation structure 106. Therefore, the second etching process 1002 can use a wet etchant that does not affect the isolation structure 106. In addition, in some embodiments, after performing the second etching process 1002, the top surface 106t of the isolation structure 106 not covered by the protection layer 108a can have a third average surface roughness that is approximately equal to the second surface roughness.

[0044] like Fig.11 As shown in the cross-sectional view 1100 of FIG. 1 , the second masking layer ( Fig.10 902). The via structures 108 each include an upper horizontal segment 108u, the upper horizontal segment 108u including a protective layer 108a and a conductive layer 108b, and the via structure 108 may include a sidewall vertical segment 108s and a central horizontal segment 108c, the sidewall vertical segment 108s and the central horizontal segment 108c only including the conductive layer 108b. In some embodiments, the upper horizontal segment 108u of the via structure 108 has a fifth thickness t5, which is greater than the fourth thickness t4 of the central horizontal segment 108c and the sixth thickness t6 of the sidewall vertical segment 108s. In some embodiments, the difference between the fifth thickness t5 and the fourth thickness t4 is approximately equal to the seventh thickness ( t6 ) of the conductive layer 108b. Figure 4 In some embodiments, for example, the fifth thickness t5 is in a range of about 300 angstroms and about 1000 angstroms.

[0045] like Fig.12 As shown in the cross-sectional view 1200 of FIG. 1 , a transparent electrode 112, an optical emitter structure 110, and a second blocking structure 114 are formed on the isolation structure 106 and the through-hole structure 108. In some embodiments, since the transparent electrode 112 fills the third opening ( Figure 8 804), so the transparent electrode 112 has a bottommost surface 112b lower than the top surface 106t of the isolation structure 106. Therefore, from the cross-sectional view 1200, each of the through-hole structures 108 has two sidewall vertical segments ( Fig.11108s). In addition, the through-hole structure 108 electrically couples the transparent electrode 112 to the reflector electrode 102. In some embodiments, the transparent electrode 112 may include a conductive material that is also optically transparent, such as indium tin oxide (ITO), fluorine tin oxide (FTO), etc. In some embodiments, the transparent electrode 112 may have a thickness in a range of, for example, between about 500 angstroms and about 3000 angstroms. In some embodiments, the optical emitter structure 110 may be or include an organic light emitting diode (OLED) or some other suitable light generating device. In some embodiments, the optical emitter structure 110 may have a thickness in a range of, for example, between about 500 angstroms and about 3000 angstroms.

[0046] In some embodiments, to generate light at the first interface 206 between the transparent electrode 112 and the optical emitter structure 110 during operation of the display device, the transparent electrode 112 and the optical emitter structure 110 may include different materials. In addition, in some embodiments, the second blocking structure 114 may separate a portion of the transparent electrode 112 from a portion of the optical emitter structure 110 to define the first pixel region 101a, the second pixel region 101b, and the third pixel region 101c. It should be understood that the display device may include an array of pixel regions and may include more than the first pixel region 101a, the second pixel region 101b, and the third pixel region 101c. Some of the second blocking structures 114 may directly overlie the first blocking structure 104, and the second blocking structure 114 may include a dielectric material for electrically and optically isolating the pixel regions (101a, 101b, 101c) from each other. For example, the second blocking structure 114 may include a nitride (e.g., silicon nitride, silicon oxynitride), an oxide (e.g., silicon oxide), etc. For example, in some embodiments, the second barrier structure 114 may include a multilayer film stack of silicon nitride and silicon oxide. In addition, in some embodiments, the second barrier structure 114 may include the same material as the isolation structure 106, the first barrier structure 104, and / or the interconnect dielectric structure 132. Each of the transparent electrode 112, the optical emitter structure 110, and the second barrier structure 114 may be formed by various steps, including a deposition process (e.g., physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition, atomic layer deposition (ALD), sputtering, etc.), a removal process (e.g., wet etching, dry etching, chemical mechanical planarization (CMP), etc.) and / or a patterning process (e.g., photolithography / etching).

[0047] Therefore, the display device includes a control circuit system 120 for selectively operating the first pixel region 101a, the second pixel region 101b, and the third pixel region 101c. Since the protection layer 108a protects the isolation structure 106 from being subjected to the cleaning process ( Figure 7 702) is damaged, and thus each of the pixel regions (101a, 101b, 101c) can be selectively operated by the control circuit system 120 to reliably emit colored light according to the thickness (t1, t2, t3) of the isolation structure 106.

[0048] Fig.13 Description and Figures 3 to 12 Flowchart of some embodiments of the corresponding method 1300 .

[0049] Although method 1300 is described and described as a series of actions or events below, it should be understood that the described ordering of these actions or events should not be interpreted in a limiting sense. For example, in addition to the order described and / or described herein, some actions may also occur in a different order and / or simultaneously with other actions or events. In addition, all of the actions described may not be required to implement one or more aspects or embodiments of the description herein. In addition, one or more of the actions depicted herein may be implemented in one or more separate actions and / or stages.

[0050] At act 1302, an isolation structure is formed over the reflector electrode. Figure 3 Cross-sectional view 300 of some embodiments corresponding to act 1302 is illustrated.

[0051] At act 1304, a protective layer is deposited over the isolation structure. Figure 4 Cross-sectional view 400 of some embodiments corresponding to act 1304 is illustrated.

[0052] At act 1306, a first etching process is performed to form a first opening in the protection layer and the isolation structure to expose a first surface of the reflector electrode. Figure 5 and Figure 6 The cross-sectional view 500 and the cross-sectional view 600 of some embodiments corresponding to act 1306 are described.

[0053] At act 1308, a cleaning process is performed to clean the first surface of the reflector electrode. Figure 7 Cross-sectional view 700 of some embodiments corresponding to act 1308 is illustrated.

[0054] At act 1310, a conductive layer is deposited over the protective layer and within the first opening. Figure 8 Cross-sectional view 800 of some embodiments corresponding to act 1310 is illustrated.

[0055] At act 1312, a peripheral portion of the protective layer and a peripheral portion of the conductive layer are removed to form a via structure within the opening, wherein the via structure includes the protective layer and the conductive layer and extends from a top of the isolation structure to a first surface of the reflector electrode. Figures 9 to 11 Cross-sectional views 900 to 1100 illustrate some embodiments corresponding to act 1312 .

[0056] At act 1314, a transparent electrode is formed over the isolation structure and the via structure.

[0057] At act 1316, an optical emitter structure is formed over the transparent electrode. Fig.12 Cross-sectional view 1200 illustrates some embodiments corresponding to acts 1314 and 1316 .

[0058] Therefore, the present invention is directed to a method of manufacturing a via structure using a protective layer and a conductive layer that are located above an isolation structure to mitigate damage to the isolation structure, thereby producing a reliable display device.

[0059] Therefore, in some embodiments, the present invention relates to a display device, which includes: an isolation structure arranged on a reflector electrode; a transparent electrode arranged on the isolation structure; an optical emitter structure arranged on the transparent electrode; and a through-hole structure extending from the transparent electrode to the top surface of the reflector electrode at the top surface of the isolation structure, wherein the through-hole structure includes a central horizontal segment in contact with the top surface of the reflector electrode, a sidewall vertical segment in contact with the inner sidewall of the isolation structure, and an upper horizontal segment in contact with the top surface of the isolation structure, wherein the upper horizontal segment is connected to the central horizontal segment through the sidewall vertical segment, and wherein the upper horizontal segment is thicker than the central horizontal segment.

[0060] In some embodiments, the transparent electrode has a protrusion that protrudes into the through-hole structure to the central horizontal segment, and wherein the through-hole structure surrounds the lower side of the protrusion in a cup shape. In some embodiments, the upper horizontal segment of the through-hole structure includes a conductive layer located above a protective layer. In some embodiments, the through-hole structure includes titanium nitride. In some embodiments, the sidewall vertical segment and the central horizontal segment include a continuous layer of a single material. In some embodiments, the first thickness of the upper horizontal segment is measured in a first direction orthogonal to the top surface of the reflector electrode, and wherein the second thickness of the central horizontal segment is measured in the first direction. In some embodiments, the sidewall vertical segment has a third thickness measured in a second direction perpendicular to the first direction, and wherein the first thickness is greater than the third thickness.

[0061] In other embodiments, the present invention relates to a display device, comprising: a reflector electrode coupled to an internal connection structure; an isolation structure disposed above the reflector electrode; a transparent electrode disposed above the isolation structure; an optical emitter structure disposed above the transparent electrode; and a through-hole structure extending from the top surface of the isolation structure to the reflector electrode, wherein the through-hole structure comprises a first layer located on the top surface of the isolation structure and further comprises a second layer, wherein the second layer is suspended above the top surface of the isolation structure and is separated from the top surface of the isolation structure by the first layer, and wherein the second layer has a downward protrusion that directly contacts the reflector electrode and directly contacts the inner side wall of the isolation structure.

[0062] In other embodiments, the top surface of the isolation structure has a first portion directly contacting the through-hole structure and a second portion directly contacting the transparent electrode, wherein the first portion of the top surface of the isolation structure has a first average surface roughness, wherein the second portion of the top surface of the isolation structure has a second average surface roughness, wherein the first average surface roughness is approximately equal to the second average surface roughness. In other embodiments, the first layer comprises a material different from the second layer. In other embodiments, the through-hole structure has a first thickness measured from the top surface of the isolation structure to the topmost surface of the through-hole structure, wherein the through-hole structure has a second thickness measured from the bottommost surface of the through-hole structure to the bottommost surface of the transparent electrode, and wherein the first thickness is greater than the second thickness. In other embodiments, the through-hole structure directly contacts the inner sidewall of the transparent electrode, wherein the through-hole structure directly separates the inner sidewall of the isolation structure from the inner sidewall of the transparent electrode, wherein the through-hole structure has a third thickness measured from the inner sidewall of the transparent electrode to the inner sidewall of the isolation structure, and wherein the first thickness is greater than the third thickness, and wherein the third thickness is approximately equal to the second thickness. In other embodiments, the first thickness is at least about 100 angstroms greater than the second thickness.

[0063] In another embodiment, the present invention relates to a method for forming a display device, the method comprising: forming an isolation structure over a reflector electrode; depositing a protective layer over the isolation structure; forming a first opening extending through the protective layer and the isolation structure to expose the first surface of the reflector electrode, wherein the inner sidewalls of the protective layer and the inner sidewalls of the isolation structure define the sidewalls of the first opening; performing a cleaning process to clean the first surface of the reflector electrode; depositing a conductive layer over the protective layer, the sidewalls of the first opening, and the first surface of the reflector electrode; and performing an etching process to remove a peripheral portion of the protective layer and a peripheral portion of the conductive layer, thereby forming a through-hole structure including the protective layer and the conductive layer, wherein the through-hole structure directly contacts the top surface of the isolation structure and the first surface of the reflector electrode and extends from the top surface of the isolation structure to the first surface of the reflector electrode.

[0064] In other embodiments, the protective layer and the conductive layer include the same material. In other embodiments, the cleaning process is an argon sputtering process. In other embodiments, performing the etching process includes a wet etching process, and wherein forming the first opening includes a dry etching process. In other embodiments, before forming the protective layer, the isolation structure has a first average surface roughness, wherein after performing the etching process, the isolation structure has a second average surface roughness approximately equal to the first average surface roughness. In other embodiments, it also includes: forming a transparent electrode on the isolation structure and the through-hole structure; and forming an optical emitter structure on the transparent electrode, wherein the transparent electrode and the optical emitter structure include different materials. In other embodiments, the protective layer is thinner than the conductive layer.

[0065] The foregoing summarizes the features of several embodiments so that those skilled in the art can better understand the various aspects of the present invention. Those skilled in the art will appreciate that they can easily use the present invention as a basis for designing or modifying other processes and structures to achieve the same purposes and / or achieve the same advantages as the embodiments described herein. Those skilled in the art will also appreciate that these equivalent constructions do not depart from the spirit and scope of the present invention, and that they may make various changes, substitutions, and modifications herein without departing from the spirit and scope of the present invention.

Claims

1. A display device, comprising: an isolation structure disposed on the reflector electrode; A transparent electrode, disposed on the isolation structure; an optical emitter structure disposed on the transparent electrode; as well as A through-hole structure extending from the transparent electrode to the top surface of the reflector electrode at the top surface of the isolation structure, wherein the through-hole structure includes a central horizontal segment in contact with the top surface of the reflector electrode, a sidewall vertical segment in contact with the inner sidewall of the isolation structure, and an upper horizontal segment in contact with the top surface of the isolation structure, wherein the upper horizontal segment is connected to the central horizontal segment through the sidewall vertical segment, and wherein the upper horizontal segment is thicker than the central horizontal segment, wherein the transparent electrode has a protrusion protruding into the through-hole structure to the central horizontal segment, and wherein the through-hole structure surrounds the lower side of the protrusion in a cup shape. 2 . The display device according to claim 1 , wherein the transparent electrode comprises indium tin oxide or fluorine tin oxide. 3 . The display device of claim 1 , wherein the upper horizontal segment of the via structure comprises a conductive layer located above a protective layer. The display device according to claim 1 , wherein the through-hole structure comprises titanium nitride.

5. The display device of claim 1, wherein the sidewall vertical segments and the central horizontal segment comprise continuous layers of a single material.

6. The display device of claim 1, wherein a first thickness of the upper horizontal segment is measured in a first direction normal to the top surface of the reflector electrode, and wherein a second thickness of the central horizontal segment is measured in the first direction. 7 . The display device of claim 6 , wherein the sidewall vertical segment has a third thickness measured in a second direction perpendicular to the first direction, and wherein the first thickness is greater than the third thickness.

8. A display device, comprising: a reflector electrode coupled to the interconnect structure; an isolation structure disposed on the reflector electrode; A transparent electrode, disposed on the isolation structure; an optical emitter structure disposed on the transparent electrode; as well as A through-hole structure extending from the top surface of the isolation structure to the reflector electrode, wherein the through-hole structure includes a first layer located on the top surface of the isolation structure and also includes a second layer, wherein the second layer is suspended above the top surface of the isolation structure and is separated from the top surface of the isolation structure by the first layer, and wherein the second layer has a downward protrusion that directly contacts the reflector electrode and directly contacts the inner side wall of the isolation structure.

9. A display device according to claim 8, wherein the top surface of the isolation structure has a first portion directly contacting the through-hole structure and a second portion directly contacting the transparent electrode, wherein the first portion of the top surface of the isolation structure has a first average surface roughness, wherein the second portion of the top surface of the isolation structure has a second average surface roughness, wherein the first average surface roughness is approximately equal to the second average surface roughness. 10 . The display device of claim 8 , wherein the first layer comprises a material different from that of the second layer.

11. A display device according to claim 8, wherein the through-hole structure has a first thickness measured from the top surface of the isolation structure to the topmost surface of the through-hole structure, wherein the through-hole structure has a second thickness measured from the bottommost surface of the through-hole structure to the bottommost surface of the transparent electrode, and wherein the first thickness is greater than the second thickness.

12. The display device according to claim 11, wherein the through-hole structure directly contacts the inner side wall of the transparent electrode, wherein the through-hole structure directly separates the inner side wall of the isolation structure from the inner side wall of the transparent electrode, wherein the through-hole structure has a third thickness measured from the inner side wall of the transparent electrode to the inner side wall of the isolation structure, and wherein the first thickness is greater than the third thickness, and wherein the third thickness is approximately equal to the second thickness. The display device according to claim 11 , wherein the first thickness is at least 100 angstroms greater than the second thickness.

14. A method of forming a display device, the method comprising: forming an isolation structure over the reflector electrode; depositing a protective layer on the isolation structure; forming a first opening extending through the protective layer and the isolation structure to expose a first surface of the reflector electrode, wherein an inner sidewall of the protective layer and an inner sidewall of the isolation structure define a sidewall of the first opening; performing a cleaning process to clean the first surface of the reflector electrode; depositing a conductive layer over the protective layer, the sidewalls of the first opening, and the first surface of the reflector electrode; as well as An etching process is performed to remove a peripheral portion of the protective layer and a peripheral portion of the conductive layer, thereby forming a through-hole structure including the protective layer and the conductive layer, wherein the through-hole structure directly contacts a top surface of the isolation structure and the first surface of the reflector electrode and extends from the top surface of the isolation structure to the first surface of the reflector electrode. 15 . The method for forming a display device according to claim 14 , wherein the protective layer and the conductive layer comprise the same material. 16 . The method of forming a display device according to claim 14 , wherein the cleaning process is an argon sputtering process. 17 . The method of forming a display device according to claim 14 , wherein performing the etching process comprises a wet etching process, and wherein forming the first opening comprises a dry etching process.

18. The method for forming a display device according to claim 14, wherein before forming the protection layer, the isolation structure has a first average surface roughness, and wherein after performing the etching process, the isolation structure has a second average surface roughness approximately equal to the first average surface roughness.

19. The method for forming a display device according to claim 14, further comprising: forming a transparent electrode on the isolation structure and the through-hole structure; as well as An optical emitter structure is formed over the transparent electrode, wherein the transparent electrode and the optical emitter structure comprise different materials.

20. The method of forming a display device according to claim 14, wherein the protection layer is thinner than the conductive layer.

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