Patent Description:
In the recent years, LEDs have become popular in lighting applications. As light sources, LEDs have many advantages including higher light efficiency, lower energy consumption, longer lifetime, smaller size, and faster switching.

Displays having micro-scale LEDs are known as micro-LED. Micro-LED displays have arrays of micro-LEDs forming the individual pixel elements. A pixel may be a minute area of illumination on a display screen, one of many from which an image is composed. In other words, pixels may be small discrete elements that together constitute an image as on a display. Pixels are normally arranged in a two-dimensional (2D) matrix, and are represented using dots, squares, rectangles, or other shapes. Pixels may be the basic building blocks of a display or digital image and with geometric coordinates.

When manufacturing the micro-LEDs, an etching process, such as a dry etching or a wet etching process, is frequently used to electrically isolate individual micro-LEDs. In order to yield a plurality of fully isolated functional micro-LED mesas, the conventional process typically etches away the continuous functional epitaxy layer completely. However, when transferring, or after transferring, the conventional micro-LED mesas to a substrate, such as a driving circuit substrate, the fully isolated functional micro-LED mesas may easily peel off from the substrate because the adhesion of the micro-LED mesas is weak. The problem is even more significant when the micro-LED mesas become even smaller. Furthermore, during the convention etching process to isolate the micro-LED mesas, the sidewalls of the micro-LED mesas may be damaged and impact the optical and electrical properties of the LED structure.

Patent document No. <CIT> discloses techniques for wafer-to-wafer bonding for manufacturing light emitting diodes (LEDs). A method of manufacturing LEDs includes etching a semiconductor material to form a plurality of adjacent mesa shapes. The semiconductor material includes one or more epitaxial layers. The method also includes forming a passivation layer within gaps between the adjacent mesa shapes and bonding a base wafer to a first surface of the semiconductor material.

Patent document No. <CIT> discloses an improved method of creating LEDs. Rather than using a dielectric coating to separate the bond pads from the top surface of the LED, this region of the LED is implanted with ions to increase its resistivity to minimize current flow therethrough. A plurality of LEDs are produced on a single substrate by implanting ions in the regions between the LEDs and then etching a trench, where the trench is narrower than the implanted regions and positioned within these regions. This results in a trench where both sides have current confinement capabilities to reduce leakage.

Patent document No. <CIT> discloses a light emitting device, including: a first semiconductor region; a second semiconductor region and third semiconductor region which are provided in the first semiconductor region; a first semiconductor light emitting element of which first electrode is electrically connected to a main surface of the second semiconductor region; a second semiconductor light emitting element of which third electrode is electrically connected to a main surface of the third semiconductor region; and a conductor which electrically connects the second electrode of the first semiconductor light emitting element and the third semiconductor region, and which electrically connects the second electrode and the third electrode through the third semiconductor region. In the light emitting device, the semiconductor light emitting elements are connected in series, and are directly connected to a power source.

Embodiments of the disclosure address the above problems by providing a LED structure with a plurality of LED units surrounded by an isolation layer and the method for manufacturing the same, and therefore the drawbacks of using etching process can be avoided.

Embodiments of the LED structure and method for forming the LED structure are disclosed herein.

In one example, a LED structure is disclosed. The LED structure includes a substrate, a bonding layer, a first doping type semiconductor layer, a multiple quantum well (MQW) layer, a second doping type semiconductor layer, a passivation layer and an electrode layer. The bonding layer is formed on the substrate, and the first doping type semiconductor layer is formed on the bonding layer. The MQW layer is formed on the first doping type semiconductor layer, and the second doping type semiconductor layer is formed on the MQW layer. The second doping type semiconductor layer includes an isolation material made through implantation, and the passivation layer is formed on the second doping type semiconductor layer. The electrode layer is formed on the passivation layer in contact with a portion of the second doping type semiconductor layer through a first opening on the passivation layer, the isolation material divides the second doping type semiconductor layer into a plurality of LED mesas, and the plurality of LED mesas correspond to a plurality of LED units, respectively, and the LED structure further includes: a plurality of contacts of a driving circuit formed in the substrate, each contact is located at an interspace of adjacent LED mesas, the electrode layer electrically connects the second doping type semiconductor layer and the contact through the first opening and a second opening on each contact, and each LED unit is individually driven by a corresponding contact of the driving circuit, and the plurality of LED mesas include a first LED mesa and a second LED mesa adjacent to the first LED mesa, and the MQW layer, the first doping type semiconductor layer and the bonding layer beneath the first LED mesa horizontally extend to the MQW layer, the first doping type semiconductor layer and the bonding layer beneath the second LED mesa.

In another example, the isolation material includes an ion-implanted material.

In another example, the ion-implanted material includes hydrogen, helium, nitrogen, oxygen, fluorine, magnesium, silicon, or argon ion implanted material.

In another example, each LED unit includes: the bonding layer formed on the substrate; the first doping type semiconductor layer formed on the bonding layer; the MQW layer formed on the first doping type semiconductor layer; and the second doping type semiconductor layer formed on the MQW layer, the plurality of LED units includes a first LED unit and a second LED unit adjacent to the first LED unit, and the second doping type semiconductor layer of the first LED unit is electrically isolated with the second doping type semiconductor layer of the second LED unit by the isolation material.

In another example, a method for manufacturing a LED structure is disclosed. The method includes: forming a semiconductor layer on a first substrate, the semiconductor layer comprising a first doping type semiconductor layer, a multiple quantum well (MQW) layer on the first doping type semiconductor layer, and a second doping type semiconductor layer on the MQW layer; performing an implantation operation to form an ion-implanted material in the second doping type semiconductor layer, to divide the second doping type semiconductor layer into a plurality of LED mesas, where each LED mesa is electrically isolated by the ion-implanted material; performing a first etching operation to remove at least a portion of the ion-implanted material, a portion of the MQW layer, a portion of the first doping type semiconductor layer and a portion of the bonding layer to expose a plurality of contact of a driving circuit formed in the first substrate; forming a passivation layer on the second doping type semiconductor layer; forming a first opening on the passivation layer exposing a portion of the second doping type semiconductor layer and a second opening on the passivation layer exposing the contact; and forming an electrode layer on the passivation layer covering the first opening and the second opening, and each contact is located at an interspace of adjacent LED mesas, and the electrode layer electrically connects the second doping type semiconductor layer and the contact through the first opening and the second opening on each contact, and the plurality of LED mesas include a first LED mesa and a second LED mesa adjacent to the first LED mesa, and the MQW layer, the first doping type semiconductor layer and the bonding layer beneath the first LED mesa horizontally extend to the MQW layer, the first doping type semiconductor layer and the bonding layer beneath the second LED mesa, and the plurality of LED mesas correspond to a plurality of LED units, respectively, and each LED unit is individually driven by a corresponding contact of the driving circuit.

In another example, the implantation operation is performed with an implantation energy between about <NUM> keV and about <NUM> keV.

In another example, forming the semiconductor layer on the first substrate, includes: forming a driving circuit in the first substrate; forming the semiconductor layer on a second substrate; bonding the semiconductor layer onto the first substrate through a bonding layer; and removing the second substrate.

The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate implementations of the present disclosure and, together with the description, further serve to explain the present disclosure and to enable a person skilled in the pertinent art to make and use the present disclosure.

Implementations of the present disclosure will be described with reference to the accompanying drawings.

Although specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. As such, other configurations and arrangements can be used without departing from the scope of the invention as defined by the claims.

Functional and structural features as described in the present disclosures can be combined, adjusted, and modified with one another and in ways not specifically depicted in the drawings, such that these combinations, adjustments, and modifications are within the scope of the invention as defined by the claims.

Similarly, terms, such as "a," "an, " or "the, " again, may be understood to convey a singular usage or to convey a plural usage, depending at least in part upon context.

It should be readily understood that the meaning of "on, " "above, " and "over" in the present disclosure should be interpreted in the broadest manner such that "on" not only means "directly on" something but also includes the meaning of "on" something with an intermediate feature or a layer therebetween, and that "above" or "over" not only means the meaning of "above" or "over" something but can also include the meaning it is "above" or "over" something with no intermediate feature or layer therebetween (i.e., directly on something).

Further, spatially relative terms, such as "beneath, " "below, " "lower, " "above, " "upper, " and the like, may be used herein for ease of description to describe one element or feature's relationship to another element (s) or feature (s) as illustrated in the figures.

A substrate can be a layer, can include one or more layers therein, and/or can have one or more layers thereupon, thereabove, and/or therebelow. For example, a semiconductor layer can include one or more doped or undoped semiconductor layers and may have the same or different materials.

The substrate itselfcan be patterned. Furthermore, the substrate can include a wide array of semiconductor materials, such as silicon, silicon carbide, gallium nitride, germanium, gallium arsenide, indium phosphide, etc. Alternatively, the substrate can be made from an electrically non-conductive material, such as a glass, a plastic, or a sapphire wafer. Further alternatively, the substrate can have semiconductor devices or circuits formed therein.

As used herein, the term "micro" LED, "micro" p-n diode or "micro" device refers to the descriptive size of certain devices or structures according to implementations of the invention. As used herein, the terms "micro" devices or structures are meant to refer to the scale of <NUM> to <NUM>. However, it is to be appreciated that implementations of the present invention are not necessarily so limited, and that certain aspects of the implementations may be applicable to larger, and possibly smaller size scales.

Implementations of the present invention describe a LED structure or a micro-LED structure and a method for manufacturing the structure. For manufacturing a micro-LED display, an epitaxy layer is bonded to a receiving substrate. The receiving substrate, for example, may be, but is not limited to, a display substrate including a CMOS backplane or TFT glass substrate. Then the epitaxy layer is formed with an array of micro-LEDs on the receiving substrate. When forming the micro-LEDs on the receiving substrate, because the adhesion of the small functional mesas on the receiving substrate is weak and it is proportional to the mesa size, the plurality of small functional mesas may peel off from the receiving substrate and cause failure of a display (dead pixel) during the manufacturing process. To address the aforementioned issues, the present disclosure introduces a solution in which the functional LED mesas are isolated by an isolation material without performing etching process on the epitaxy layer, and therefore the adhesion area between the functional LEDs and the receiving substrate could be enlarged to avoid potential peeling off. In addition, the manufacturing method described in the present disclosure can further reduce physical damage of sidewalls of functional LED mesas, reduce damage of quantum well structure which is the light emitting region of the LED, and improve the optical and electrical properties of functional mesas.

<FIG> illustrates a top view of an exemplary LED structure <NUM>, according to some implementations of the present disclosure, and <FIG> illustrates a cross-section view of an exemplary LED structure <NUM> along line A-A', according to some implementations of the present disclosure. For the purpose of better explaining the present disclosure, the top view of LED structure <NUM> in <FIG> and the cross-section view of LED structure <NUM> in <FIG> will be described together. LED structure <NUM> includes a first substrate <NUM> and a plurality of LED units <NUM> (e.g., LED units <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> as shown in <FIG>). LED units <NUM> are bonded on first substrate <NUM> through a bonding layer <NUM>. In some implementations, first substrate <NUM> may include a semiconductor material, such as silicon, silicon carbide, gallium nitride, germanium, gallium arsenide, indium phosphide. In some implementations, first substrate <NUM> may be made from an electrically non-conductive material, such as a glass, a plastic or a sapphire wafer. In some implementations, first substrate <NUM> may have driving circuits formed therein, and first substrate <NUM> may be CMOS backplane or TFT glass substrate. The driving circuit provides the electronic signals to LED units <NUM> to control the luminance. In some implementations, the driving circuit may include an active matrix driving circuit, in which each individual LED unit <NUM> corresponds to an independent driver. In some implementations, the driving circuit may include a passive matrix driving circuit, in which the plurality of LED units <NUM> are aligned in an array and are connected to the data lines and the scan lines driven by the driving circuit.

Bonding layer <NUM> is a layer of an adhesive material formed on first substrate <NUM> to bond first substrate <NUM> and LED units <NUM>. In some implementations, bonding layer <NUM> may include a conductive material, such as metal or metal alloy. In some implementations, bonding layer <NUM> may include Au, Sn In Cu or Ti. In some implementations, bonding layer <NUM> may include a non-conductive material, such as polyimide (PI) , polydimethylsiloxane (PDMS). In some implementations, bonding layer <NUM> may include a photoresist, such as SU-<NUM> photoresist. In some implementations, bonding layer <NUM> may be hydrogen silsesquioxane (HSQ) or divinylsiloxane-bis-benzocyclobutene (DVS-BCB). It is understood that the descriptions of the material of bonding layer <NUM> are merely illustrative and are not limiting, and those skilled in the art can change according to requirements, all of which are within the scope of the present application.

Referring to <FIG>, each LED unit <NUM> includes its portion of bonding layer <NUM>, a first doping type semiconductor layer <NUM>, a second doping type semiconductor layer <NUM>, and a multiple quantum well (MQW) layer <NUM> formed between first doping type semiconductor layer <NUM> and second doping type semiconductor layer <NUM>. First doping type semiconductor layer <NUM> is formed on bonding layer <NUM>. In some implementations, first doping type semiconductor layer <NUM> and second doping type semiconductor layer <NUM> may include one or more layers formed with II-VI materials, such as ZnSe or ZnO, or III-V nitride materials, such as GaN, AlN, InN, InGaN, GaP, AlInGaP, AlGaAs, and their alloys.

In some implementations, first doping type semiconductor layer <NUM> may be a p-type semiconductor layer that extends across multiple LED units <NUM> (e.g., four LED units <NUM> as illustrated in <FIG>) and forms a common anode of these LED units <NUM>. For example, first doping type semiconductor layer <NUM> of LED unit <NUM>-<NUM> extends to its adjacent LED units <NUM>-<NUM> and <NUM>-<NUM>, and similarly, first doping type semiconductor layer <NUM> of LED unit <NUM>-<NUM> extends to its adjacent LED units <NUM>-<NUM> and <NUM>-<NUM>. In some implementations, first doping type semiconductor layer <NUM> that extends across the LED units may be relatively thin. By having a thin layer of continuous first doping type semiconductor across the individual LED units, the bonding area between substrate <NUM> and the plurality of LED units <NUM> is not limited in the area beneath second doping type semiconductor layer <NUM> but also extends to the areas between the individual LED units. In other words, by having a thin layer of continuous first doping type semiconductor layer <NUM>, the area of bonding layer <NUM> is increased. Hence, the bonding strength between substrate <NUM> and the plurality of LED units <NUM> is increased and the risk of peeling-off of LED structure <NUM> can be reduced.

In some implementations, first doping type semiconductor layer <NUM> may include p-type GaN. In some implementations, first doping type semiconductor layer <NUM> may be formed by doping magnesium (Mg) in GaN. In some implementations, first doping type semiconductor layer <NUM> may include p-type InGaN. In some implementations, first doping type semiconductor layer <NUM> may include p-type AlInGaP. Each of LED units <NUM> has an anode and a cathode connected to the driving circuit, e.g., one that is formed in substrate <NUM> (driving circuit not explicitly shown). For example, each LED unit <NUM> has the anode connected to a constant voltage source and has the cathode connected to a source/drain electrode of the driving circuit. In other words, by forming the continuous first doping type semiconductor layer <NUM> across the individual LED units <NUM>, the plurality of LED units <NUM> have a common anode formed by first doping type semiconductor layer <NUM> and bonding layer <NUM>.

In some implementations, second doping type semiconductor layer <NUM> may be a n-type semiconductor layer and form a cathode of each LED unit <NUM>. In some implementations, second doping type semiconductor layer <NUM> may include n-type GaN. In some implementations, second doping type semiconductor layer <NUM> may include n-type InGaN. In some implementations, second doping type semiconductor layer <NUM> may include n-type AlInGaP. Second doping type semiconductor layers <NUM> of different LED units <NUM> are electrically isolated, thus each LED unit <NUM> having a cathode that can have a voltage level different from the other units. As a result of the disclosed implementations, a plurality of individually functionable LED units <NUM> are formed with their first doping type semiconductor layers <NUM> horizontally extended across the adjacent LED units, and their second doping type semiconductor layers <NUM> electrically isolated between the adjacent LED units. Each LED unit <NUM> further includes a multiple quantum well (MQW) layer <NUM> formed between first doping type semiconductor layer <NUM> and second doping type semiconductor layer <NUM>. MQW layer <NUM> is the active region of LED unit <NUM>.

According to the invention, the second doping type semiconductor layer <NUM> is divided by an isolation material <NUM>. For example, as shown in <FIG>, second doping type semiconductor layer <NUM> is divided into a plurality of LED mesas <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> by isolation material <NUM>. In other words, LED mesas <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> are electrically isolated by isolation material <NUM> formed inbetween. For example, LED mesa <NUM>-<NUM> of LED unit <NUM>-<NUM> is electrically isolated with LED mesa <NUM>-<NUM> of LED unit <NUM>-<NUM> and LED mesa <NUM>-<NUM> of LED unit <NUM>-<NUM> by isolation material <NUM>.

In some implementations, isolation material <NUM> may be an ion-implanted material. In some implementations, isolation material <NUM> may be formed by implanting ion materials in second doping type semiconductor layers <NUM>. In some implementations, isolation material <NUM> may be formed by implanting H +, He +, N +, O +, F +, Mg +, Si +or Ar +ions in second doping type semiconductor layers <NUM>. In some implementations, second doping type semiconductor layers <NUM> may be implanted with one or more ion materials to form isolation material <NUM>. Isolation material <NUM> has the physical properties of electrical insulation. By implanting ion material in a defined area of second doping type semiconductor layers <NUM>, the material of second doping type semiconductor layers <NUM> in the defined area may be transformed to isolation material <NUM>, which electrically isolates LED mesas <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> from each other.

In some implementations, as shown in <FIG>, isolation material <NUM> may be formed in second doping type semiconductor layers <NUM> for a depth not sufficient to penetrate MQW layer <NUM>. MQW layer <NUM>, first doping type semiconductor layer <NUM> and bonding layer <NUM> beneath each LED mesa horizontally extend to MQW layer <NUM>. first doping type semiconductor layer <NUM> and bonding layer <NUM> beneath adjacent LED mesas. For example, MQW layer <NUM>, first doping type semiconductor layer <NUM> and bonding layer <NUM> beneath LED mesa <NUM>-<NUM> horizontally extend to MQW layer <NUM>, first doping type semiconductor layer <NUM> and bonding layer <NUM> beneath LED mesas <NUM>-<NUM> and <NUM>-<NUM>.

In some implementations, the implantation depth of isolation material <NUM> may be controlled above MQW layer <NUM>, as shown in <FIG>. In some implementations, the implantation depth of isolation material <NUM> may be controlled to not penetrate MQW layer <NUM> and isolation material <NUM> stops short to contact first doping type semiconductor layer <NUM>. It is understood that the location, shape, and depth of isolation material <NUM> shown in <FIG> are merely illustrative and are not limiting, and those skilled in the art can change according to requirements, all of which are within the scope of the present application.

As shown in <FIG>, a passivation layer <NUM> is formed on second doping type semiconductor layer <NUM>, including LED mesas <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> and isolation material <NUM>. Passivation layer <NUM> may be used for protecting and isolating LED units <NUM>. In some implementations, passivation layer <NUM> may include SiO <NUM>, Al 2O <NUM>, SiN or other suitable materials. In some implementations, passivation layer <NUM> may include polyimide, SU-<NUM> photoresist, or other photo-patternable polymer. An electrode layer <NUM> is formed on a portion of passivation layer <NUM>, and electrode layer <NUM> electrically connects second doping type semiconductor layer <NUM> through an opening <NUM> on passivation layer <NUM>. In some implementations, electrode layer <NUM> may be conductive materials, such as indium tin oxide (ITO) , Cr, Ti, Pt, Au, Al, Cu, Ge or Ni.

<FIG> illustrates another cross-section view of the exemplary LED structure <NUM> along line B-B', according to some implementations of the present disclosure. First substrate <NUM> has driving circuits formed therein for driving LED units <NUM>. A contact <NUM> of the driving circuit is exposed in an opening <NUM> between two LED units <NUM>, and contact <NUM> is electrically connected with second doping type semiconductor layer <NUM> through electrode layer <NUM>. In other words, the electrical connection of second doping type semiconductor layer <NUM> and contact <NUM> of the driving circuit is accomplished by electrode layer <NUM>. As described above, second doping type semiconductor layer <NUM> forms the cathode of each LED unit <NUM>, hence contact <NUM> provides a driving voltage of the cathode of each LED unit <NUM> from the driving circuit to second doping type semiconductor layer <NUM> through electrode layer <NUM>.

<FIG> illustrates another top view of LED structure <NUM>, according to some implementations of the present disclosure. In <FIG>, the layers beneath electrode layer <NUM> and passivation layer <NUM> are illustrated with dash lines for the purpose of explanation. In <FIG>, LED structure <NUM> includes <NUM> LED units <NUM>. Each LED unit <NUM> includes a p-n diode layer formed by first doping type semiconductor layer <NUM> and second doping type semiconductor layer <NUM> and multiple quantum well layer <NUM>. Passivation layer <NUM> is formed on the p-n diode layer, and electrode layer <NUM> is formed on passivation layer <NUM>.

Opening <NUM> is formed on passivation layer <NUM> exposing second doping type semiconductor layer <NUM>, and opening <NUM> is formed on passivation layer <NUM> exposing contact <NUM>. Electrode layer <NUM> is formed on a portion of passivation layer <NUM> covering opening <NUM> and opening <NUM>, and therefore electrode layer <NUM> electrically connects with second doping type semiconductor layer <NUM> and contact <NUM>. In the examples shown in <FIG>, opening <NUM> is located at the center of each LED unit <NUM> and opening <NUM> is located at the interspace of adjacent LED units <NUM>. It is understood that the locations and designs (such as shapes and sizes) of opening <NUM>, opening <NUM> and electrode layer <NUM> may deviate from the examples shown in <FIG>based on the specific implementations and are not limited here.

In <FIG>, LED structure <NUM> includes <NUM> LED units <NUM>, and each LED unit <NUM> is individually functionable. Second doping type semiconductor layer <NUM> of each LED unit <NUM> is electrically isolated by isolation material <NUM>. First doping type semiconductor layer <NUM> locates under second doping type semiconductor layer <NUM> and passivation layer <NUM>, and first doping type semiconductor layer <NUM> is the common anode of these <NUM> LED units <NUM>. Consistent with the present disclosure, a plurality of LED units are referred to as "individually functionable" when first doping type semiconductor layer <NUM> of these LED units (e.g., the <NUM> LED units <NUM>) is electrically connected not only during the manufacturing process of forming LED structure <NUM> but also after the manufacturing process and each LED unit <NUM> can be individually driven by a different driving circuit.

<FIG> illustrates a top view of another LED structure <NUM>, according to some implementations of the present disclosure. The shape of LED mesa <NUM>-<NUM> in the top view in <FIG> is circular, which is different from the shape of LED mesa <NUM>-<NUM> in the top view of LED structure <NUM> shown in <FIG>. By implanting ion material in a different defined area of second doping type semiconductor layers <NUM>, the shape of LED mesa <NUM>-<NUM> may be formed differently. It is understood that, in some implementations, the position and shape of LED mesas in the top view may be changed according to various designs or applications, and the shape of LED mesas or LED unit <NUM> in the top view is not limited here. In some implementations, the position and shape of opening <NUM>, opening <NUM>, electrode layer <NUM> or contact <NUM> in the top view may be changed according to various designs and applications as well, and is not limited here.

<FIG> illustrate cross sections of the exemplary LED structure <NUM> during a manufacturing process, according to some implementations of the present disclosure, <FIG> illustrate top views of LED structure <NUM> at different stages of a manufacturing process, according to some implementations of the present disclosure, and <FIG> is a flowchart of an exemplary method <NUM> for manufacturing LED structure <NUM>, according to some implementations of the present disclosure. For the purpose of better explaining the present disclosure, <FIG>, <FIG> and <FIG> will be described together.

In <FIG>, a driving circuit is formed in first substrate <NUM> and the driving circuit includes contact <NUM>. For example, the driving circuit may include CMOS devices manufactured on a silicon wafer and some wafer-level packaging layers or fan-out structures are stacked on the CMOS devices to form contact <NUM>. For another example, the driving circuit may include TFTs manufactured on a glass substrate and some wafer-level packaging layers or fan-out structures are stacked on the TFTs to form contact <NUM>. A semiconductor layer is formed on a second substrate <NUM>, and the semiconductor layer includes first doping type semiconductor layer <NUM>, second doping type semiconductor layer <NUM> and MQW layer <NUM>.

In some implementations, first substrate <NUM> or second substrate <NUM> may include a semiconductor material, such as silicon, silicon carbide, gallium nitride, germanium, gallium arsenide, indium phosphide. In some implementations, first substrate <NUM> or second substrate <NUM> may be made from an electrically non-conductive material, such as a glass, a plastic or a sapphire wafer. In some implementations, first substrate <NUM> may have driving circuits formed therein, and first substrate <NUM> may include a CMOS backplane or TFT glass substrate. In some implementations, first doping type semiconductor layer <NUM> and second doping type semiconductor layer <NUM> may include one or more layers based on II-VI materials, such as ZnSe or ZnO, or III-V nitride materials, such as GaN, AlN, InN, InGaN, GaP, AlInGaP, AlGaAs, and their alloys. In some implementations, first doping type semiconductor layer <NUM> may include a p-type semiconductor layer, and second doping type semiconductor layer <NUM> may include a n-type semiconductor layer.

In <FIG>, bonding layer <NUM> is formed on first substrate <NUM>. In some implementations, bonding layer <NUM> may include a conductive material, such as metal or metal alloy. In some implementations, bonding layer <NUM> may include Au, Sn In Cu or Ti. In some implementations, bonding layer <NUM> may include a non-conductive material, such as polyimide (PI), or polydimethylsiloxane (PDMS). In some implementations, bonding layer <NUM> may include a photoresist, such as SU-<NUM> photoresist. In some implementations, bonding layer <NUM> may include hydrogen silsesquioxane (HSQ) or divinylsiloxane-bis-benzocyclobutene (DVS-BCB). In some implementations, a conductive layer <NUM> may be formed on first doping type semiconductor layer <NUM>. In some implementations, conductive layer <NUM> may form a common electrode covering the entire first doping type semiconductor layer <NUM>. In some implementations, conductive layer <NUM> may form an ohmic contact on first doping type semiconductor layer <NUM>. In some implementations, conductive layer <NUM> and bonding layer <NUM> may be collectively referred to as one layer in later operations.

Referring to <FIG> and operation <NUM> of <FIG>, second substrate <NUM> and the semiconductor layer, including first doping type semiconductor layer <NUM>, second doping type semiconductor layer <NUM> and MQW layer <NUM>, are flipped over and bonded to first substrate <NUM> through bonding layer <NUM> and conductive layer <NUM>. Then, second substrate <NUM> may be removed from the semiconductor layer. <FIG> shows bonding layer <NUM> between first substrate <NUM> and first doping type semiconductor layer <NUM>. However, in some implementations, bonding layer <NUM> may include one or multiple layers to bond first substrate <NUM> and first doping type semiconductor layer <NUM>. For example, bonding layer <NUM> may include a single conductive or non-conductive layer. For another example, bonding layer <NUM> may include an adhesive layer and a conductive or non-conductive layer. In some implementations, bonding layer <NUM> and conductive layer <NUM> may be collectively referred to as one layer after operation <NUM>. It is understood that the descriptions of the material of bonding layer <NUM> are merely illustrative and are not limiting, and those skilled in the art can change according to requirements, all of which are within the scope of the present application.

In <FIG>, a thinning operation may be performed on second doping type semiconductor layer <NUM> to remove a portion of second doping type semiconductor layer <NUM>. <FIG> shows a top view of second doping type semiconductor layer <NUM> after the thinning operation. In some implementations, the thinning operation may include a dry etching or a wet etching operation. In some implementations, the thinning operation may include a chemicalmechanical polishing (CMP) operation. In some implementations, the thickness including first doping type semiconductor layer <NUM>, MQW layer <NUM> and second doping type semiconductor layer <NUM> may be between about <NUM> and about <NUM>. In some other implementations, the thickness including first doping type semiconductor layer <NUM>, MQW layer <NUM> and second doping type semiconductor layer <NUM> may be between about <NUM> and about <NUM>. In some alternative implementations, the thickness including first doping type semiconductor layer <NUM>, MQW layer <NUM> and second doping type semiconductor layer <NUM> may be between about <NUM> and about <NUM>.

Referring to <FIG> and operation <NUM> of <FIG>, an implantation operation is performed to form an isolation material <NUM> in second doping type semiconductor layer <NUM>, and as a result of the implantation, second doping type semiconductor layer <NUM> is divided into a plurality of LED mesas <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> by isolation material <NUM>. The plurality of LED mesas <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> are electrically isolated from each other by isolation material <NUM>. <FIG> shows a top view of LED structure <NUM> after the implantation operation, and <FIG> shows the cross section along line BB' in <FIG>. In <FIG>, second doping type semiconductor layer <NUM> is divided into a plurality of LED mesas <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> by isolation material <NUM>.

In some implementations, isolation material <NUM> may be formed by implanting ion materials to a defined region in second doping type semiconductor layers <NUM>. In some implementations, isolation material <NUM> may be formed by implanting H +, He +, N +, O +, F +, Mg +, Si + or Ar + ions in second doping type semiconductor layers <NUM>. In some implementations, second doping type semiconductor layers <NUM> may be implanted with one or more ion materials to form isolation material <NUM>. Isolation material <NUM> has the physical properties of electrical insulation. By implanting ion material in a defined area of second doping type semiconductor layers <NUM>, the material of second doping type semiconductor layers <NUM> in the defined area may be transformed to isolation material <NUM> and electrically isolate LED mesas <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>. In some implementations, the implantation operation may be performed with an implantation energy between about <NUM> keV and about <NUM> keV. In some implementations, the implantation operation may be performed with an implantation energy between about <NUM> keV and about <NUM> keV. In some implementations, the implantation operation may be performed with an implantation energy between about <NUM> keV and about <NUM> keV.

In some implementations, isolation material <NUM> may be formed in second doping type semiconductor layers <NUM> for a depth not sufficient to penetrate MQW layer <NUM>. MQW layer <NUM>, first doping type semiconductor layer <NUM> and bonding layer <NUM> beneath each LED mesa horizontally extend to MQW layer <NUM>, first doping type semiconductor layer <NUM> and bonding layer <NUM> beneath adjacent LED mesas. For example, MQW layer <NUM>, first doping type semiconductor layer <NUM> and bonding layer <NUM> beneath LED mesa <NUM>-<NUM> horizontally extend to MQW layer <NUM>, first doping type semiconductor layer <NUM> and bonding layer <NUM> beneath LED mesas <NUM>-<NUM> and <NUM>-<NUM>.

In some implementations, the implantation depth of isolation material <NUM> may be controlled so that isolation material <NUM> stops short to contact MQW layer <NUM>, as shown in <FIG>. In some implementations, the implantation depth of isolation material <NUM> may be controlled to not penetrate MQW layer <NUM> and isolation material stops short to contact first doping type semiconductor layer <NUM>. It is understood that the location, shape, and depth of isolation material <NUM> shown in <FIG> are merely illustrative and are not limiting, and those skilled in the art can change according to specific implementations, all of which are within the scope of the present application.

Referring to <FIG> and operation <NUM> of <FIG>, a first etching operation is performed to remove a portion of isolation material <NUM>, a portion of MQW layer <NUM>, and a portion of first doping type semiconductor layer106 to expose contact <NUM> of the driving circuit formed in first substrate <NUM>. <FIG> shows a top view of LED structure <NUM> after the first etching operation. The first etching operation may be a dry etching or a wet etching operation. In a dry etching operation or a wet etching operation, a hard mask (e.g., a photoresist) may be formed on second doping type semiconductor layer <NUM> by photolithography process. Then, the uncovered portion of second doping type semiconductor layer <NUM> is removed by dry etching plasma or wet etching solution to expose contact <NUM>. During the first etching operation, LED mesas are protected by isolation material <NUM>, and the physical damage of sidewalls of LED mesas can be therefore prevented.

Referring to <FIG> and operations <NUM> and <NUM> of <FIG>, passivation layer <NUM> is formed on second doping type semiconductor layer <NUM>, and first opening <NUM> is formed on passivation layer <NUM> exposing a portion of second doping type semiconductor layer <NUM> and second opening <NUM> is formed on passivation layer <NUM> exposing contact <NUM>. <FIG> shows a top view of LED structure <NUM> after forming openings <NUM> and <NUM>. The LED structure <NUM> is covered by passivation layer <NUM> and openings <NUM> and <NUM> expose second doping type semiconductor layer <NUM> and contacts <NUM>.

In some implementations, passivation layer <NUM> may include SiO <NUM>, Al2O <NUM>, SiN or other suitable materials for isolation and protection. In some implementations, passivation layer <NUM> may include polyimide, SU-<NUM> photoresist, or other photo-patternable polymer. In operation <NUM> of <FIG>, opening <NUM> and opening <NUM> are formed to expose a portion of second doping type semiconductor layer <NUM> and expose contact <NUM>. In some implementations, operation <NUM> may be performed by a second etching operation to remove a portion of passivation layer <NUM> and form opening <NUM> and opening <NUM>. In some further implementations, provided passivation layer <NUM> is formed by a photo-sensitive material (e.g., polyimide, SU-<NUM> photoresist, or other photo-patternable polymer) , operation <NUM> may be performed by a photolithography operation to pattern passivation layer <NUM> and expose opening <NUM> and opening <NUM>.

Referring to <FIG> and operation <NUM> of <FIG>, electrode layer <NUM> is formed on passivation layer <NUM> covering opening <NUM> and opening <NUM>. The top view of LED structure <NUM> after operation <NUM> is shown in <FIG>. Electrode layer <NUM> electrically connects second doping type semiconductor layer <NUM> and contact <NUM> and forms an electrical path to connect the LED unit with the driving circuit in substrate <NUM>. The driving circuit may control the voltage and current level of second doping type semiconductor layer <NUM> through contact <NUM> and electrode layer <NUM>. In some implementations, electrode layer <NUM> may include conductive materials, such as indium tin oxide (ITO) , Cr, Ti, Pt, Au, Al, Cu, Ge or Ni.

The present disclosure provides a LED structure and a method for manufacture the LED structure in which second doping type semiconductor layer <NUM> is divided by isolation material <NUM>. The functional LED mesas are divided by isolation material <NUM> without performing etching process on the epitaxy layer, and therefore the adhesion area between the functional LEDs and the receiving substrate could be enlarged to avoid potential peeling off. Because ion-implanted semiconductor material may have a physical characteristic of high electrical resist, the current flow of LED units could be confined within a certain semiconductor layer, which define the light emitting areas. By using ion implantation to form the isolation material in the semiconductor functional epitaxy layer to form highly resistive region, the present disclosure may eliminate the use of wet etching or dry etching in the formation of LED mesas, avoid the physical damage of sidewall of LED mesas, and improve the optical and electrical properties of LED units. Furthermore, without using conventional isolation trenches between mesas, the space and density of micro-LED array limited by the physical trenches could be greatly improved.

According to one aspect of the present disclosure, a LED structure is disclosed. The LED structure includes a substrate, a bonding layer, a first doping type semiconductor layer, a multiple quantum well (MQW) layer, a second doping type semiconductor layer, a passivation layer and an electrode layer. The bonding layer is formed on the substrate, and the first doping type semiconductor layer is formed on the bonding layer. The MQW layer is formed on the first doping type semiconductor layer, and the second doping type semiconductor layer is formed on the MQW layer. The second doping type semiconductor layer includes an isolation material made through implantation, and the passivation layer is formed on the second doping type semiconductor layer. The electrode layer is formed on the passivation layer in contact with a portion of the second doping type semiconductor layer through a first opening on the passivation layer.

According to the invention, the isolation material divides the second doping type semiconductor layer into a plurality of LED mesas. According to the invention, the LED structure further includes a plurality of contacts of a driving circuit formed in the substrate, and each contact is located at an interspace of adjacent LED mesas. According to the invention, the electrode layer electrically connects the second doping type semiconductor layer and the contact through the first opening and a second opening on each contact.

According to the invention, the plurality of LED mesas include a first LED mesa and a second LED mesa adjacent to the first LED mesa, and the MQW layer, the first doping type semiconductor layer and the bonding layer beneath the first LED mesa horizontally extend to the MQW layer, the first doping type semiconductor layer and the bonding layer beneath the second LED mesa. In some implementations, the isolation material includes an ion-implanted material.

According to a further aspect of the present disclosure, a method for manufacturing a LED structure is disclosed. A semiconductor layer is formed on a first substrate. The semiconductor layer includes a first doping type semiconductor layer, a MQW layer on the first doping type semiconductor layer, and a second doping type semiconductor layer on the MQW layer. An implantation operation is performed to form an ion-implanted material in the second doping type semiconductor layer. A first etching operation is performed to remove at least a portion of the ion-implanted material, a portion of the MQW, a portion of the first doping type semiconductor layer and a portion of the bonding layer to expose a contact of a driving circuit formed in the first substrate. A passivation layer is formed on the second doping type semiconductor layer. A first opening is formed on the passivation layer exposing a portion of the second doping type semiconductor layer and a second opening is formed on the passivation layer exposing the contact on the first substrate. An electrode layer is formed on the passivation layer covering the first opening and the second opening.

According to the invention, the ion-implanted material is formed in the second doping type semiconductor layer through implantation to divide the second doping type semiconductor layer into a plurality of LED mesas, and each LED mesa is electrically isolated by the ion-implanted material. In some implementations, an ion material is implanted to a defined region of the semiconductor layer with an implantation depth so that the ion-implanted material does not contact the first doping type semiconductor layer. In some implementations, an ion material is implanted to a defined region of the semiconductor layer with an implantation depth so that the ion-implanted material does not contact the first doping type semiconductor layer and the MQW layer.

In some implementations, the implantation operation is performed with an implantation energy between about <NUM> keV and about <NUM> keV. In some implementations, the ion material includes hydrogen, helium, nitrogen, oxygen, fluorine, magnesium, silicon, or argon ion.

According to the invention, a driving circuit is formed in the first substrate, the semiconductor layer is formed on a second substrate, the semiconductor layer is bonded onto the first substrate through a bonding layer, and the second substrate is removed.

The foregoing description of the specific implementations can be readily modified and/or adapted for various applications.

Claim 1:
A light emitting diode, LED, structure (<NUM>), comprising:
a substrate (<NUM>);
a bonding layer (<NUM>) formed on the substrate (<NUM>);
a first doping type semiconductor layer (<NUM>) formed on the bonding layer (<NUM>);
a multiple quantum well, MQW, layer (<NUM>) formed on the first doping type semiconductor layer (<NUM>); and
a second doping type semiconductor layer (<NUM>) formed on the MQW layer (<NUM>), wherein the second doping type semiconductor layer (<NUM>) comprises an isolation material (<NUM>) made through implantation;
a passivation layer (<NUM>) formed on the second doping type semiconductor layer (<NUM>); and
an electrode layer (<NUM>) formed on the passivation layer (<NUM>) in contact with a portion of the second doping type semiconductor layer (<NUM>) through a first opening (<NUM>) on the passivation layer (<NUM>),
wherein the isolation material (<NUM>) divides the second doping type semiconductor layer (<NUM>) into a plurality of LED mesas (<NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>), and the plurality of LED mesas (<NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>) correspond to a plurality of LED units (<NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>), respectively, and
the LED structure (<NUM>) further comprises:
a plurality of contacts (<NUM>) of a driving circuit formed in the substrate (<NUM>), wherein each contact (<NUM>) is located at an interspace of adjacent LED mesas (<NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>), the electrode layer (<NUM>) electrically connects the second doping type semiconductor layer (<NUM>) and the contact (<NUM>) through the first opening (<NUM>) and a second opening (<NUM>) on each contact (<NUM>), and each LED unit (<NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>) is individually driven by a corresponding contact (<NUM>) of the driving circuit, and
the plurality of LED mesas (<NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>) comprise a first LED mesa and a second LED mesa adjacent to the first LED mesa, wherein the MQW layer (<NUM>), the first doping type semiconductor layer (<NUM>) and the bonding layer (<NUM>) beneath the first LED mesa horizontally extend to the MQW layer (<NUM>), the first doping type semiconductor layer (<NUM>) and the bonding layer (<NUM>) beneath the second LED mesa.