CN114420798A - Preparation method of contact electrode, Mirco-LED array device and preparation method thereof - Google Patents
Preparation method of contact electrode, Mirco-LED array device and preparation method thereof Download PDFInfo
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- CN114420798A CN114420798A CN202111486051.6A CN202111486051A CN114420798A CN 114420798 A CN114420798 A CN 114420798A CN 202111486051 A CN202111486051 A CN 202111486051A CN 114420798 A CN114420798 A CN 114420798A
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- H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
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- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/15—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components with at least one potential-jump barrier or surface barrier specially adapted for light emission
- H01L27/153—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components with at least one potential-jump barrier or surface barrier specially adapted for light emission in a repetitive configuration, e.g. LED bars
- H01L27/156—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components with at least one potential-jump barrier or surface barrier specially adapted for light emission in a repetitive configuration, e.g. LED bars two-dimensional arrays
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- H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/36—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
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- H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/44—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the coatings, e.g. passivation layer or anti-reflective coating
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- H01L2933/0016—Processes relating to electrodes
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Abstract
The invention discloses a preparation method of a contact electrode, a Mirco-LED array device and a preparation method thereof, wherein the preparation method of the contact electrode comprises the following steps: providing a Micro-LED array substrate, and forming an indium main body layer at the position of a contact electrode of the Micro-LED array substrate; forming a metal protection layer on the indium main body layer; and refluxing the indium main body layer and the metal protection layer to obtain the contact electrode. The contact electrode prepared by the invention has uniform height, shape and size and small deviation, and reduces the probability of short circuit and insufficient soldering in the electrode connection process of the contact electrode and the driving circuit board.
Description
Technical Field
The invention relates to the technical field of Micro-LEDs, in particular to a preparation method of a contact electrode, a Mirco-LED array device and a preparation method of the Mirco-LED array device.
Background
The Micro-LED based on the third generation wide bandgap semiconductor GaN material has the characteristics of self-luminescence, low power consumption, high brightness, high contrast, high resolution and the like, and the Micro-LED array device has a high-density pixel array (namely a high-density Micro-LED unit array, each Micro-LED unit represents one pixel) as a display screen, and the size of a single pixel (namely a single Micro-LED unit) is often dozens of micrometers or even several micrometers. The display screen can be applied to AR, VR, MR, micro-projection or wearable equipment with high requirements on resolution and brightness, and even can combine illumination and display into a whole, so that the display screen has high commercial application value and considerable development prospect.
Because the Micro-LED pixel points are relatively small, especially for pixels with sizes of only a few micrometers or even nanometers, in order to achieve effective connection between the contact electrode of each Micro-LED pixel and the electrode of the driving circuit board, the contact electrodes need to have consistency, that is, the contact electrodes need to have small deviations in position, size and height, and have good mechanical properties and electrical properties.
In the prior art, because the metal indium has better ductility, high thermal conductivity, good wettability and plastic deformation, the stress generated between the contact electrode and the electrode of the driving circuit board due to the mismatch of thermal expansion coefficients can be relieved, and therefore, the metal indium is the best material for the contact electrode. When the indium contact electrode is prepared, the indium contact electrode needs to be refluxed in the last step, and the indium contact electrode is condensed into indium ball salient points through refluxing, so that indium in a loose structure becomes more compact, and better mechanical property and electrical property are provided. However, in the prior art, during the reflow process of the indium contact electrode, the indium contact electrode cannot be condensed into the indium ball bump, or the indium contact electrode is not condensed uniformly, and the indium contact electrode is prone to climbing and whisker formation, and the above factors make the height, shape and size of the indium ball bump obtained after reflow uneven, and the deviation is large, referring to fig. 1 and 2, and fig. 5 and 6, thereby affecting the effective connection between the contact electrode and the electrode of the driving circuit board, and easily causing problems of short circuit, insufficient soldering, and the like.
Disclosure of Invention
One of the objectives of the present invention is to overcome the above-mentioned defects in the prior art, and to provide a method for manufacturing a contact electrode, which makes the height, shape and size of the contact electrode obtained after reflow uniform, has small deviation, and reduces the probability of short circuit and insufficient solder during the electrode connection process between the contact electrode and the driving circuit board.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a method for preparing a contact electrode, comprising the steps of:
providing a Micro-LED array substrate, and forming an indium main body layer at the position of a contact electrode of the Micro-LED array substrate;
forming a metal protection layer on the indium main body layer;
and refluxing the indium main body layer and the metal protection layer to obtain the contact electrode.
The second purpose of the invention is to provide a preparation method of the Mirco-LED array device, so that the prepared contact electrode is uniform in height, shape and size and small in deviation, and the probability of short circuit and insufficient soldering in the electrode connection process of the contact electrode and the driving circuit board is reduced.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a preparation method of a Mirco-LED array device comprises the following steps:
preparing a Micro-LED array substrate, wherein the Micro-LED array substrate comprises a substrate, a plurality of Micro-LED chips arranged on the substrate and distributed at intervals, and a passivation layer covering the Micro-LED chips, the passivation layer is provided with through holes exposing the Micro-LED chips, the through holes are used for preparing contact electrodes, and the contact electrodes are used for being connected with electrodes of a driving circuit board and providing power for the Micro-LED chips;
and preparing the contact electrode in the through hole and above the through hole according to the preparation method of the contact electrode to obtain the Mirco-LED array device.
The invention also discloses a Mirco-LED array device prepared by the preparation method of the Mirco-LED array device.
The embodiment of the invention has the following beneficial effects:
according to the embodiment of the invention, the metal protective layer is arranged and used for isolating the indium main body layer from air before backflow, so that the indium main body layer is protected from oxidation, the phenomenon that an oxide layer influences backflow balling effect is avoided, the indium main body layer is protected from climbing and forming whiskers in the backflow process, and the indium main body layer is prevented from evaporating and volatilizing, so that the position, the shape and the size of the indium main body layer are prevented from generating large deviation after backflow, the prepared contact electrode is uniform in height, shape and size, the contact electrode is favorably and effectively connected with the electrode of the driving circuit board, and the probability of short circuit and false soldering is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Wherein:
FIG. 1 is an SEM image of indium contact electrodes formed with a pitch of 10 μm in the prior art.
Fig. 2 is an SEM image of a cross-section of indium contact electrodes formed with a pitch of 10 μm in the prior art.
FIG. 3 is an SEM image of contact electrodes with a pitch of 10 μm prepared according to an embodiment of the present invention.
FIG. 4 is an SEM image of a cross-section of contact electrodes prepared with a pitch of 10 μm according to an embodiment of the present invention.
Fig. 5 is an SEM image of indium contact electrodes formed with a pitch of 15 μm in the prior art.
Fig. 6 is an SEM image of a cross-section of indium contact electrodes formed with a pitch of 15 μm in the prior art.
FIG. 7 is an SEM image of contact electrodes with a pitch of 15 μm prepared according to an embodiment of the present invention.
FIG. 8 is an SEM image of a cross-section of contact electrodes with a pitch of 15 μm prepared according to an embodiment of the present invention.
Fig. 9 to 14 are schematic structural views illustrating a manufacturing process of a Micro-LED array device according to an embodiment of the present invention.
Fig. 15 is a schematic structural view of an unretired Micro-LED array device in accordance with another embodiment of the present invention.
Fig. 16 is a schematic view of the structure shown in fig. 15 after reflow.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 11 to 14, the present invention discloses a method for preparing an electrode, including the steps of:
step 1: a Micro-LED array substrate 100 is provided, and an indium body layer 210 is formed at a position of a contact electrode 200 of the Micro-LED array substrate 100.
Step 2: a metal protection layer 220 is formed on the indium body layer 210.
And step 3: the indium body layer 210 and the metal protection layer 220 are reflowed to obtain the contact electrode 200.
According to the invention, the metal protection layer 220 is arranged, the metal protection layer 220 is used for isolating the indium main body layer 210 from air before backflow, the indium main body layer 210 is protected from oxidation, an oxide layer is prevented from being generated to influence a backflow balling effect, the indium main body layer 210 is protected from climbing and whisker formation in the backflow process, and the indium main body layer 210 is prevented from evaporation and volatilization, so that the position, the shape and the size of the indium main body layer 210 are prevented from generating large deviation after backflow, the prepared contact electrode 200 is uniform in height, shape and size, the contact electrode 200 is favorably and effectively connected with an electrode of a driving circuit board, and the probability of short circuit and insufficient soldering is reduced. Referring to fig. 1 and 2 and fig. 5 and 6, in the prior art, the contact electrode 200 includes only the indium body layer 210, before reflow, the indium body layer 210 is in contact with air, an oxide layer exists on the surface, after reflow, the shape of each contact electrode 200 is irregular and circular, and the difference between the shape and the size is large, as can be seen from the cross-sectional view: the outline has more burrs, and is not smooth, and the difference is great, this is mainly that indium oxide layer is too thick and in the backward flow in-process indium volatilize or outwards splash and cause, consequently, among the prior art, the solder ball bump shape after the backward flow, height and size are all inhomogeneous, and the deviation is great. Referring to fig. 3 and 4 and fig. 7 and 8, after the metal protection layer 220 is added, the contact electrode 200 after reflow is regular circular in shape and has small difference in shape and size, and can be seen from the cross-sectional view: compared with the prior art, the contact electrode 200 prepared by the method has higher height of the solder ball salient point and smoother outline, which shows that the contact electrode 200 prepared by the method is easier to form the solder ball salient point, the formed solder ball salient point has higher wettability and is more favorable for bonding with the electrode of the driving circuit board, and also shows that the metal protection layer 220 effectively protects the indium main body layer 210 from non-volatilization and outward splashing, so the contact electrode 200 formed by the method of the invention has more uniform shape, height and size and high consistency, and is favorable for bonding with the electrode of the driving circuit board.
The main structure of the contact electrode 200 is the indium main body layer 210, but of course, other functional layers may be included, for example, in order to enhance the adhesion with the conductive metal layer 122, an adhesion metal layer 230 is formed at the bottom of the through hole 140 (referring to fig. 15 and 16, for example, a Ti layer or an Au layer, etc., may be deposited in sequence), and a light reflecting layer (for example, an Al layer, etc.) and a magnetic material layer (for example, an Ni layer, etc.) may be disposed in the middle of the indium main body layer 210.
In a preferred embodiment, the material of the metal protection layer 220 includes Au, Ag, Ni, or an alloy of any two or three of Au, Ag, and Ni. Indium has relatively high permeability in Au, Ag or Ni, and can form stable alloy with Au, Ag or Ni, and in the backflow process, the metal protection layer 220 of Au, Ag or Ni can be condensed together with the indium main body layer 210 to form solder ball salient points, and in addition, the metal protection layer 220 can protect the indium main body layer 210 from climbing and forming whiskers, and prevent the indium main body layer 210 from evaporating and volatilizing, so that the solder ball salient points with uniform height, shape and size can be obtained, referring to figures 1-8, the solder ball salient points with the metal protection layer 220 have higher height than the pure indium solder ball salient points, the wettability of the indium main body layer 210 is improved, and the bonding with the electrode of the driving circuit board is facilitated, so that the yield of the connection of the contact electrode 200 and the electrode of the driving circuit board is improved. In addition, the contact electrode 200 obtained after reflow, i.e., the alloy formed by Au, Ag or Ni and indium, is proved by experiments to have higher shear strength, electrical conductivity and thermal conductivity and lower resistance, which shows that Au, Ag or Ni also improves the mechanical and electrical properties of the indium body layer 210. Au, Ag or Ni is also an oxidation-resistant metal, is not easily oxidized by itself, and can protect the indium body layer 210 from being oxidized to form indium oxide, and since indium oxide has a high melting point, a high hardness, and a high resistance, the formation of indium oxide not only has an adverse effect on condensation to form a solder bump, but also increases the resistance of the contact electrode 200 and reduces the adhesion of the contact electrode 200, impairing the mechanical and electrical properties of the contact electrode 200.
Further, in a preferred embodiment, the thickness of the metal protection layer 220 is 5nm to 500 nm. The melting temperatures of Au, Ag, and Ni are conventionally about 1065 c, 962 c, and 1668 c, respectively, however, the melting temperature of Au, Ag, or Ni having a nano thickness (5nm to 500nm) is greatly reduced by the nano size effect, has a melting point close to that of the indium body layer 210, and does not affect the melting state, adhesive strength, and the like when the contact electrode 200 is connected to the electrode of the driving circuit board. In addition, the thickness of the indium body layer 210 is usually micron-sized (1 μm-8 μm), and the metal protection layer 220 with a nanometer thickness is thinner, so that the metal protection layer and the indium body layer 210 are more easily condensed into a solder bump together, and the wettability of the contact electrode 200 is improved.
The mass of the metal protection layer 220 accounts for 0.1-25% of the total mass of the metal protection layer 220 and the indium main body layer 210, and the alloy of the indium main body layer and the metal protection layer formed after reflow still has a low melting temperature, so that welding is facilitated.
In the above embodiments, it is preferable that the atmosphere from the start of forming the indium body layer 210 until the formation of the metal protection layer 220 is continued to be a vacuum atmosphere or an oxygen-free atmosphere, so as to prevent the indium body layer 210 from being oxidized, prevent the condensation reaction during the reflow process from being affected, and prevent the height of the solder bump from being lowered.
In a preferred embodiment, the method for forming the indium body layer 210 and the method for forming the metal protection layer 220 are both vacuum evaporation methods. The vacuum evaporation method comprises the following specific steps: the substrate is placed in a vacuum coating device, such as an electron beam evaporator, a thermal evaporator, a magnetron sputtering device and the like, metal particles to be deposited or corresponding targets are placed, the metal materials are converted into gas after obtaining energy, and deposition is carried out on the surface of the substrate to form a deposition layer. The electron beam evaporator bombards metal material with electrons to heat and gasify the metal material. The thermal evaporator is used for heating and gasifying metal materials by utilizing a current heating evaporation boat. In the magnetron sputtering, argon is introduced to generate plasma to bombard a target material, and then atoms sputtered out are deposited to form a metal film.
The advantages of using the vacuum evaporation method include, firstly, the indium main layer 210 and the metal protection layer 220 can be formed by continuous evaporation, i.e. the device can be continuously placed in a vacuum coating device, contact with air can be completely avoided, the operation is more convenient, and the process is more optimized. In the prior art, a solution plating method is adopted, the device needs to be taken out of the solution after the indium body layer 210 is formed, air is inevitably contacted, and the indium body layer 210 is easily oxidized. Secondly, the vacuum evaporation method can accurately control the film forming thickness, the thicknesses of the indium main body layer 210 and the metal protection layer 220 covering the surface of the indium main body layer 210 can be monitored in real time by using a crystal control instrument in the evaporation process, the precision can reach 0.1nm, and the content of the metal protection layer 220 in the contact electrode 200 alloy generated after backflow can be accurately adjusted by accurately controlling the thicknesses of the indium main body layer 210 and the metal protection layer 220, so that the melting point temperature of the contact electrode 200 alloy generated after backflow is adjusted, and the reliability of the contact electrode 200 alloy at high temperature is improved. The solution plating method cannot monitor the thickness of the deposited layer in real time, and the deposited layer with the nanometer-scale thickness is difficult to be plated. Thirdly, a vacuum evaporation method may be combined with a photolithography process, that is, a patterned photoresist layer is formed on the passivation layer 130, a hollow pattern of the patterned photoresist layer corresponds to a position of the contact electrode 200, then the indium body layer 210 and the metal protection layer 220 are sequentially formed by using the patterned photoresist layer as a mask and the vacuum evaporation method, and then the patterned photoresist layer is removed, and simultaneously, the photoresist is removed, and the excessive deposition layer above the photoresist is removed together, so that the process is simpler. In the solution electroplating method, a metal seed layer is required to be deposited firstly for priming, and the metal seed layer is difficult to strip cleanly, so that the size of indium balls is not uniform after indium reflows, and the flip-chip yield is reduced. The distance between the Micro-LED pixels is small, several micrometers to dozens of micrometers, and residual indium metal can increase the leakage of the Micro-LED and even short circuit, so that the Micro-LED is invalid. Moreover, the seed layer of the substrate is a copper plating layer, and copper is easily diffused into silicon or silicon oxide of the Micro-LED chip, so that the performance of the device is seriously affected. And fourthly, the vacuum evaporation process is to deposit a film by utilizing physical vapor phases such as thermal evaporation, electron beam evaporation, magnetron sputtering and the like, so that no waste liquid is generated, and the vacuum evaporation process is more environment-friendly. The solution plating method uses a plating solution, and a plating waste solution is treated after use.
Specifically, in step 1, in one embodiment, the process of forming the indium body layer 210 includes: firstly, forming a patterned photoresist layer on the surface of the Micro-LED array substrate 100, wherein the hollow pattern of the patterned photoresist layer corresponds to the position of the contact electrode 200, then placing the Micro-LED array substrate 100 with the patterned photoresist layer in a vacuum coating device, placing indium particles or an indium target material, wherein the indium particles or the indium target material obtain energy and are converted into indium gas to be deposited at the position of the contact electrode, forming an indium main body layer 210, and monitoring the thickness of the indium main body layer 210 in real time during the formation of the indium main body layer 210, wherein, preferably, the vacuum degree in the vacuum coating device is 1.0 × 10-5Torr～1.0×10-6Torr, the deposition rate of indium gas is
Using photoresist as mask to remove photoresistAnd the redundant deposited layer above the photoresist can be removed together, compared with the prior art, the redundant deposited layer is easier to be removed, and the working procedure is saved.
In step 2, in an embodiment, the process of forming the metal protection layer 220 includes: continuously placing the Micro-LED array substrate 100 with the indium main body layer 210 formed, which is prepared in the step 1, in a vacuum coating device, placing metal particles or corresponding targets to be evaporated, converting the energy of the metal particles or the targets into gas to be deposited on the indium main body layer to form a metal protection layer 220, and monitoring the thickness of the metal protection layer 220 in real time in the process of forming the metal protection layer 220, wherein the background vacuum degree of the vacuum coating device is 1.0 x 10-5Torr～1.0×10-6Torr, the deposition rate of the metal protective layer is
In the step 3, in a specific embodiment, the refluxing environment is a vacuum environment or an oxygen-free atmosphere (for example, an atmosphere of nitrogen and formic acid), the highest temperature of the refluxing is 150 ℃ to 300 ℃, and the highest temperature of the refluxing is maintained for 10s to 150 s.
Referring to fig. 9 to 16, the present invention also discloses a method for manufacturing a Micro-LED array device, comprising the steps of:
step S1: the method comprises the steps of preparing a Micro-LED array substrate 100, wherein the Micro-LED array substrate 100 comprises a substrate 110, a plurality of Micro-LED chips arranged on the substrate 110 and distributed at intervals, and a passivation layer 130 covering the Micro-LED chips, the Micro-LED chips distributed at intervals form a Micro-LED array, each Micro-LED chip represents a pixel point, the passivation layer 130 is used for protecting the Micro-LED chips and preventing adjacent Micro-LED chips from short-circuiting, the passivation layer 130 is provided with a through hole 140 exposing the Micro-LED chips, the through hole 140 is used for preparing a contact electrode 200, and the contact electrode 200 is used for being connected with an electrode of a driving circuit board and providing power for the Micro-LED chips.
Step S2: by adopting the preparation method of the contact electrode 200, the contact electrode 200 is formed in the through hole 140 and above the through hole 140, and the Micro-LED array device is obtained.
In one embodiment, the Micro-LED chip includes an N-type layer 1211, an active layer 1212, a P-type layer, and a conductive metal layer 122 sequentially disposed over the substrate 110, the passivation layer 130 is disposed over the conductive metal layer 122, the contact electrode 200 includes an anode and a cathode, the N-type layer 1211 is connected to the cathode, the P-type layer is connected to the anode, and the Micro-LED chip can emit light when the contact electrode is energized. The N-type layer 1211, the active layer 1212, and the P-type layer constitute the Micro-LED semiconductor 121.
In one embodiment, each Micro-LED chip includes an anode and a cathode, in another embodiment, each Micro-LED chip includes an anode, and two or more Micro-LED chips share a cathode, and in other embodiments, each Micro-LED chip includes a cathode, and two or more Micro-LED chips share an anode.
In the above embodiments, the anode and the cathode may be disposed on the same side of the Micro-LED chip, i.e., in a flip-chip structure, or the anode and the cathode may be disposed on two sides of the Micro-LED chip, i.e., in a vertical structure.
In this particular embodiment, the Micro-LED chip further comprises a current spreading layer 123 disposed between the conductive metal layer 122 and the P-type layer, the current spreading layer 123 for making the current passing through the Micro-LED chip more uniform.
Example 1
The Micro-LED array substrate 100 can be prepared by any method, and referring to fig. 9 to 16, in this embodiment, the method for preparing the Micro-LED array substrate 100 includes the following steps:
step S11: referring to fig. 9, an epitaxial wafer is sequentially grown on the substrate 110, and the epitaxial wafer includes an N-type layer 1211, an active layer 1212, and a P-type layer sequentially grown on the substrate 110, and in this embodiment, in order to improve the growth quality of the epitaxial wafer, a process of growing the buffer layer 150 on the substrate 110 is further included before the epitaxial wafer is formed. In this embodiment, a u-GaN layer 160 is also grown over the buffer layer 150 in order to improve the growth quality of the epitaxial wafer.
The material of the substrate 110 may be sapphire, silicon carbide, or the like, in this specific embodiment, the material of the substrate 110 is a sapphire transparent substrate 110, and the material of the epitaxial wafer is gallium nitride.
Step S12: referring to fig. 9, the epitaxial wafer is etched until inside the N-type layer 1211 to form a plurality of Micro-LED semiconductors 121 distributed at intervals, the Micro-LED semiconductors 121 including the N-type layer 1211, the active layer 1212, and the P-type layer sequentially disposed on the substrate 110.
Step S13: referring to fig. 10, a current spreading layer 123 is formed over the P-type layer.
Step S14: referring to fig. 10, a conductive metal layer 122 is formed at the positions of the anode and the cathode, respectively.
Step S15: referring to fig. 11, a passivation layer 130 is formed on the upper surface of the device obtained in step S14, and the material of the passivation layer 130 may be silicon nitride or silicon oxide.
Step S16: referring to fig. 11, the passivation layer 130 is etched at the positions of the anode and the cathode respectively until the conductive metal layer 122 is exposed, and a through hole 140 is formed, that is, the Micro-LED array substrate 100 is obtained, where the position of the through hole 140 corresponds to the position of the contact electrode 200.
Step S17: the contact electrode 200 is prepared in the through-hole 140 and above the through-hole 140 according to the above-described method for preparing the contact electrode 200.
In this embodiment, a patterned photoresist layer is first formed on the upper surface of the device obtained in step S16, the hollow pattern of the patterned photoresist layer corresponds to the position of the through hole 140, i.e. the position of the contact electrode 200, and then the device with the patterned photoresist layer is placed in an electron beam evaporator, metal particles to be evaporated are placed in the device, and the vacuum degree is 5 × 10-6Torr, deposition rate of
The solid indium solid particles are converted into indium metal gas by using electron beams, an indium gas source is deposited in the through holes 140 to form an indium body layer 210, and the thickness of the indium body layer 210 is monitored in real time during the formation of the indium body layer 210, as shown in fig. 12.
Secondly, the device is continuously arranged in an electron beam evaporator to convert the metal to be evaporated with the vacuum degree of5×10- 6Torr, deposition rate of
The solid Au solid particles are converted into gold gas by using electron beams, an Au gas source is continuously deposited above the indium body layer 210 to obtain an Au metal protection layer 220, and the thickness of the metal protection layer 220 is monitored in real time in the process of forming the metal protection layer 220, as shown in fig. 13.
Thirdly, the device with the Au metal protection layer 220 formed thereon is placed in a vacuum eutectic reflow furnace, and the device is reflowed for 60s at a reflow temperature of 220 ℃ in an atmosphere of formic acid and nitrogen. The contact electrodes 200 are condensed into a dome-shaped ball, i.e., a solder ball bump, as shown in fig. 14.
Referring to fig. 15, in another embodiment, the contact electrode 200 further includes an adhesive metal layer 230 disposed at the bottom of the via hole 140, including an Au layer and a Ti layer stacked in sequence, the other processes and parameters are the same as those of embodiment 1, and the structure after forming the solder ball bump is as shown in fig. 16.
Contact electrodes 200 having pitches of 10 μm and 15 μm were respectively manufactured by the method of example 1, as shown in fig. 3 and 4 and fig. 7 and 8.
Comparative example 1
Comparative example 1 is different from example 1 in that the contact electrode 200 includes only the indium body layer 210, the reflow is directly performed after the indium body layer 210 is formed, the remaining processes and parameters are the same as those of example 1, and SEM images of the resulting contact electrode 200 are shown in fig. 1 and 2 and fig. 5 and 6.
Referring to fig. 1 and 2 and fig. 5 and 6, the contact electrode 200 includes only the indium body layer 210, and after reflow, the shape of each contact electrode 200 is irregular and circular, and the difference between the shape and the size is large, as can be seen from the cross-sectional views: the outer contour has more burrs, is not smooth and has larger difference, which is mainly caused by that the indium is retracted into balls under the influence of an excessively thick oxide layer on the indium surface and the indium is volatilized or splashed outwards in the backflow process, so the shapes, the heights and the sizes of the reflowed solder ball salient points are not uniform, and the deviation is larger. Referring to fig. 3 and 4 and fig. 7 and 8, after the metal protection layer 220 is added, the contact electrode 200 after reflow is regular circular in shape and has small difference in shape and size, and can be seen from the cross-sectional view: compared with the prior art, the contact electrode 200 prepared by the method has higher height of the solder ball salient point and smoother outline, which shows that the contact electrode 200 prepared by the method is easier to form the solder ball salient point, the formed solder ball salient point has higher wettability and is more favorable for bonding with the electrode of the driving circuit board, and also shows that the metal protection layer 220 effectively protects the indium main body layer 210, so that the indium is not oxidized before reflow and is not volatilized and splashed outwards during reflow, therefore, the contact electrode 200 formed by the method has more uniform shape, height and size and high consistency, and is favorable for bonding with the electrode of the driving circuit board.
In comparative example 1, the formation of indium oxide was unavoidable, and indium oxide had a larger resistance than indium. After reflow of the indium-gold solder in example 1, an indium-gold alloy is formed, for which the resistivity can be simply calculated using the following equation: rho ═ Σ kiρi＝k1ρ1+k2ρ2Wherein k isi＝mi/m，kiIs the ratio of mass of a substance to total mass, rhoiIs the resistivity of a substance. The resistivity of gold is 2.40 μ Ω · cm and that of indium is 8.37 μ Ω · cm, so that the resistivity of an indium-gold alloy is smaller than that of pure indium.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A method for preparing a contact electrode, comprising the steps of:
providing a Micro-LED array substrate, and forming an indium main body layer at the position of a contact electrode of the Micro-LED array substrate;
forming a metal protection layer on the indium main body layer;
and refluxing the indium main body layer and the metal protection layer to obtain the contact electrode.
2. The method of claim 1, wherein the metal protective layer comprises Au, Ag, Ni, or an alloy of any two or three of Au, Ag, and Ni.
3. The method of claim 2, wherein the metal protective layer has a thickness of 5nm to 500 nm.
4. The method for producing a contact electrode according to any one of claims 1 to 3, wherein an atmosphere from the start of forming the indium main body layer until the formation of the metal protective layer is continued to be a vacuum atmosphere or an oxygen-free atmosphere.
5. The method for producing a contact electrode according to claim 4, wherein the method for forming the indium main layer and the method for forming the metal protective layer are both vacuum evaporation methods.
6. The method for manufacturing a contact electrode according to claim 5, wherein the indium body layer is formed by: forming a patterned photoresist layer on the surface of the Micro-LED array substrate, wherein the hollow pattern of the patterned photoresist layer corresponds to the position of the contact electrode, then placing the Micro-LED array substrate with the patterned photoresist layer in a vacuum coating device, placing indium particles or an indium target material, converting the energy obtained by the indium particles or the indium target material into indium gas, depositing the indium gas at the position of the contact electrode to form an indium main body layer, and monitoring the thickness of the indium main body layer in real time in the process of forming the indium main body layer, wherein the vacuum degree of the vacuum coating device is 1.0 x 10-5Torr～1.0×10-6Torr, the deposition rate of the indium body layer is
7. The method for preparing a contact electrode according to claim 6, wherein the process of forming the metal protective layer is: continuously placing the Micro-LED array substrate with the indium main body layer in the vacuum coating device, placing metal particles to be evaporated or corresponding target materials, and converting the energy obtained by the metal particles or the target materials into gas to be deposited on the indium main body layer to form the metal protection layer, wherein the vacuum degree of the vacuum coating device is 1.0 x 10- 5Torr～1.0×10-6Torr, the deposition rate of the metal protective layer is
8. The method for producing a contact electrode according to any one of claims 1 to 3 and 5 to 7, wherein the reflow atmosphere is a vacuum atmosphere or an oxygen-free atmosphere, the maximum temperature of the reflow is 150 ℃ to 300 ℃, and the maximum temperature holding time of the reflow is 10s to 150 s.
9. A preparation method of a Mirco-LED array device is characterized by comprising the following steps:
preparing a Micro-LED array substrate, wherein the Micro-LED array substrate comprises a substrate, a plurality of Micro-LED chips arranged on the substrate and distributed at intervals, and a passivation layer covering the Micro-LED chips, the passivation layer is provided with through holes exposing the Micro-LED chips, the through holes are used for preparing contact electrodes, and the contact electrodes are used for being connected with electrodes of a driving circuit board and providing power for the Micro-LED chips;
preparing the contact electrode in the through hole and above the through hole according to the preparation method of the contact electrode in any one of claims 1 to 8 to obtain the Mirco-LED array device.
10. A Mirco-LED array device made by the method of making as claimed in claim 9.
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| CN1855462A (en) * | 2005-04-25 | 2006-11-01 | 日立协和技术工程公司 | Substrate for mounting electronic part and electronic part |
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| CN102064120A (en) * | 2010-10-22 | 2011-05-18 | 中国科学院上海微系统与信息技术研究所 | Soldering flux-free reflow technological method based on indium bumps |
| CN113257959A (en) * | 2021-04-09 | 2021-08-13 | 深圳市思坦科技有限公司 | Preparation method of micro light-emitting diode chip, micro light-emitting diode chip and display module |
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| CN1855462A (en) * | 2005-04-25 | 2006-11-01 | 日立协和技术工程公司 | Substrate for mounting electronic part and electronic part |
| KR20070073621A (en) * | 2006-01-04 | 2007-07-10 | 한양대학교 산학협력단 | Flip chip mount type of bump, manufacturing method thereof, and bonding method for flip chip using non conductive adhesive |
| CN102064120A (en) * | 2010-10-22 | 2011-05-18 | 中国科学院上海微系统与信息技术研究所 | Soldering flux-free reflow technological method based on indium bumps |
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