CN116825923A - Flip light-emitting diode chip and preparation method thereof - Google Patents
Flip light-emitting diode chip and preparation method thereof Download PDFInfo
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Abstract
The invention relates to the technical field of semiconductor devices, in particular to a flip LED chip and a preparation method thereof, at least comprising a substrate, an N-type semiconductor layer, an active luminous layer and a P-type semiconductor layer which are sequentially laminated on the substrate, wherein a current expansion layer is laminated on the P-type semiconductor layer, a P-type electrode is arranged between the P-type semiconductor layer and the current expansion layer, an N-type semiconductor conductive step is arranged on the N-type semiconductor layer, and an N-type electrode is arranged on the N-type semiconductor conductive step; the P-type electrode comprises a reflecting layer, a protective layer, a conductive layer, an over-etching layer and an ohmic contact layer which are sequentially laminated along the growth direction of the chip, wherein the reflecting layer is an Al layer, the protective layer is a periodically laminated structure of a Ni layer and a Pt layer or a Ti layer and a Pt layer, the conductive layer is an Au layer or a Cu layer, the over-etching layer is any one of the Ni layer, the Ti layer and the Pt layer, and the ohmic contact layer is a Cr layer or a Ni layer. The LED chip can effectively improve the luminous brightness of the LED chip and reduce the working voltage of the LED chip.
Description
Technical Field
The invention relates to the technical field of semiconductor devices, in particular to a flip LED chip and a preparation method thereof.
Background
The flip LED is widely applied to various aspects of lighting lamps, car lamps, display screens and the like due to the advantages of strong back light emitting, strong heat dissipation capability, high light efficiency, energy conservation and the like; the existing flip LED chip is characterized in that a current blocking layer is arranged between a current expansion layer and a P-type semiconductor, a first electrode is arranged on the current expansion layer and is in projection superposition with the current blocking layer or smaller than the current blocking layer, and the current blocking layer has the function of preventing current passing through the P-type electrode from directly and vertically flowing into the P-type semiconductor layer below the first electrode, so that current diffusion of the LED chip is uneven, and working voltage and brightness of the LED chip are higher; the current blocking layer is used for forcing the current passing through the P-type electrode to be transmitted transversely from the current expansion layer and then vertically transmitted to all the P-type semiconductor layers by the current expansion layer, so that the current of the LED chip is uniformly diffused.
In addition, the bottommost layer of the electrode layer of the conventional flip-chip light-emitting diode chip is metal Cr or Ni which can form ohmic contact with the current expansion layer, but the reflectivity of Cr or Ni is low, and light from the direction of the P-type semiconductor layer cannot be reflected from the substrate surface well.
Disclosure of Invention
In order to solve the technical problems, the invention provides a flip LED chip and a preparation method thereof.
The invention adopts the following technical scheme: the flip LED chip at least comprises a substrate, and an N-type semiconductor layer, an active light-emitting layer and a P-type semiconductor layer which are sequentially laminated on the substrate, wherein a current expansion layer is laminated on the P-type semiconductor layer, a P-type electrode is arranged between the P-type semiconductor layer and the current expansion layer, an N-type semiconductor conductive step is arranged on the N-type semiconductor layer, and an N-type electrode is arranged on the N-type semiconductor conductive step;
the P-type electrode comprises a reflecting layer, a protective layer, a conductive layer, an over-etching layer and an ohmic contact layer which are sequentially laminated along the growth direction of the chip, wherein the reflecting layer is an Al layer, the protective layer is a structure of periodically laminating a Ni layer and a Pt layer or a Ti layer and a Pt layer, the conductive layer is an Au layer or a Cu layer, the over-etching layer is any one of the Ni layer, the Ti layer and the Pt layer, and the ohmic contact layer is a Cr layer or a Ni layer.
According to the flip LED chip provided by the embodiment of the invention, the metal reflectivity of the side, close to the P-type semiconductor layer, of the P-type electrode is effectively enhanced by adjusting the structure of the P-type electrode, so that more light from the P-type semiconductor layer is reflected; the reflecting layer does not form ohmic contact with the P-type semiconductor layer, so that current passing through the P-type electrode does not vertically flow into the P-type semiconductor layer, and a current blocking layer is not required to be arranged; the protective layer can prevent the oxidation or migration of the underlying active metal Al; the conductivity of the conductive layer is higher and is responsible for long-distance transverse current transmission; the over-etching layer is responsible for ensuring that a conductive through hole arranged on the P-type electrode is completely etched, and preventing an oxide layer from being arranged on the contact surface of the bonding pad and the P-type electrode, so that the voltage of the LED chip is overhigh; ohmic contact is formed between the ohmic contact layer and the current expansion layer, so that ohmic contact area between the current expansion layer and the P-type electrode is increased, and working voltage of the LED chip is effectively reduced.
Further, the thickness of the reflecting layer is betweenThe thickness of the Ni layer and the Pt layer or the Ti layer and the Pt layer of the protective layer is between +.>The thickness of the conductive layer is between +.>The thickness of the over-etched layer is between +.>The thickness of the ohmic contact layer is between +.>
Further, the P-type electrode is gradually narrowed along the growth direction of the chip, and an included angle between the side surface of the P-type electrode and the P-type semiconductor layer is 5-30 degrees.
Further, the distance between the edge of the current expansion layer and the edge of the P-type semiconductor layer is 3-10 μm.
Further, the flip-chip light emitting diode chip further comprises a Bragg reflection layer laminated on the current spreading layer, wherein the Bragg reflection layer covers the N-type electrode, and the Bragg reflection layer is formed by TiO (titanium dioxide) 2 And SiO 2 The alternating layers are formed by periodic alternating layers, and the number of the periodic numbers of the alternating layers is 20-40.
Further, a P-type bonding pad and an N-type bonding pad are laminated on the bragg reflection layer, a P-type bragg reflection layer through hole and an N-type bragg reflection layer through hole are formed in the bragg reflection layer, the P-type bonding pad penetrates through the P-type bragg reflection layer through hole and penetrates through the current expansion layer to be electrically connected with the P-type electrode, and the N-type bonding pad penetrates through the N-type bragg reflection layer through hole to be electrically connected with the N-type electrode.
Further, the flip-chip light emitting diode chip is further provided with an isolation groove 114, and the bragg reflection layer covers the isolation groove.
Further, the N-type electrode is formed by alternately laminating one or more of a Cr layer, a Ni layer, an Al layer, an ALCu layer, a Ti layer, a Pt layer, an Au layer, an Ag layer, a Cu layer and an Sn layer.
Correspondingly, the invention also provides a preparation method of the flip LED chip, which is used for preparing the flip LED chip, and comprises the following steps:
providing a substrate;
sequentially growing an N-type semiconductor layer, an active light emitting layer and a P-type semiconductor layer on the substrate;
depositing a P-type electrode on the P-type semiconductor layer, wherein the P-type electrode comprises a reflecting layer, a protective layer, a conducting layer, an over-etching layer and an ohmic contact layer which are sequentially deposited along the growth direction of the chip;
depositing a current expansion layer covering the P-type electrode on the P-type semiconductor layer;
preparing an isolation groove on the N-type semiconductor layer;
depositing an N-type electrode on the N-type semiconductor layer;
depositing a Bragg reflection layer on the current expansion layer, wherein the Bragg reflection layer covers the isolation groove;
p-type bonding pads and N-type bonding pads are respectively deposited on the Bragg reflection layer.
According to the preparation method of the flip LED chip, the metal reflectivity of the side, close to the P-type semiconductor layer, of the P-type electrode is effectively enhanced by adjusting the structure of the P-type electrode, so that more light from the P-type semiconductor layer is reflected; the reflecting layer does not form ohmic contact with the P-type semiconductor layer, so that current passing through the P-type electrode does not vertically flow into the P-type semiconductor layer, and a current blocking layer is not required to be arranged; the protective layer can prevent the oxidation or migration of the underlying active metal Al; the conductivity of the conductive layer is higher and is responsible for long-distance transverse current transmission; the over-etching layer is responsible for ensuring that a conductive through hole arranged on the P-type electrode is completely etched, and preventing an oxide layer from being arranged on the contact surface of the bonding pad and the P-type electrode, so that the voltage of the LED chip is overhigh; ohmic contact is formed between the ohmic contact layer and the current expansion layer, so that ohmic contact area between the current expansion layer and the P-type electrode is increased, and working voltage of the LED chip is effectively reduced.
Further, the reflecting layer is an Al layer, the protecting layer is a periodically laminated structure of a Ni layer and a Pt layer or a Ti layer and a Pt layer, the conducting layer is an Au layer or a Cu layer, the over-etching layer is any one of the Ni layer, the Ti layer and the Pt layer, and the ohmic contact layer is a Cr layer or a Ni layer.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a flip-chip led chip according to a first embodiment of the present invention;
fig. 2 is a schematic diagram of a flip-chip led chip according to a first embodiment of the present invention;
FIG. 3 is a schematic cross-sectional view of a P-type current transmission strip portion of a P-type electrode in a flip LED chip according to a first embodiment of the present invention;
fig. 4 is a flowchart of a method for manufacturing a flip-chip light emitting diode chip according to a first embodiment of the present invention.
Reference numerals illustrate:
10. a substrate; 111. an N-type semiconductor layer; 112. an active light emitting layer; 113. a P-type semiconductor layer; 114. an isolation groove; 115. an N-type semiconductor conductive step; 12. a P-type electrode; 121. a P-type disc part; 122. a P-type current transmission strip part; 123. a reflective layer; 124. a protective layer; 125. a conductive layer; 126. over-etching the layer; 127. an ohmic contact layer; 13. a current spreading layer; 131. an extension layer through hole; 14. an N-type electrode; 141. an N-type disk portion; 142. an N-type current transmission strip part; 15. a Bragg reflection layer; 151. a P-type Bragg reflection layer through hole; 152. an N-type Bragg reflection layer through hole; 161. a P-type bonding pad; 162. an N-type bonding pad.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and intended to illustrate embodiments of the invention and should not be construed as limiting the invention.
In the description of the embodiments of the present invention, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate description of the embodiments of the present invention and simplify description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless explicitly defined otherwise.
In the embodiments of the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured" and the like are to be construed broadly and include, for example, either permanently connected, removably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the embodiments of the present invention will be understood by those of ordinary skill in the art according to specific circumstances.
Example 1
Referring to fig. 1 to 4, a flip-chip light emitting diode chip according to a first embodiment of the present invention at least includes a substrate 10, an N-type semiconductor layer 111, an active light emitting layer 112, and a P-type semiconductor layer 113 sequentially stacked on the substrate 10, a current spreading layer 13 stacked on the P-type semiconductor layer 113, a P-type electrode 12 disposed between the P-type semiconductor layer 113 and the current spreading layer 13, an N-type semiconductor conductive step 115 disposed on the N-type semiconductor layer 111, and an N-type electrode 14 disposed on the N-type semiconductor conductive step 115;
the P-type electrode 12 includes a reflective layer 123, a protective layer 124, a conductive layer 125, an over-etched layer 126, and an ohmic contact layer 127 sequentially stacked along a chip growth direction, wherein the reflective layer 123 is an Al layer, the protective layer 124 is a periodically stacked structure of a Ni layer and a Pt layer or a Ti layer and a Pt layer, the conductive layer 125 is an Au layer or a Cu layer, the over-etched layer 126 is any one of the Ni layer, the Ti layer, and the Pt layer, and the ohmic contact layer 127 is a Cr layer or a Ni layer.
In this embodiment, the protective layer 124 is a periodically laminated structure of Ti layer and Pt layer, and the lamination period is 2; the conductive layer 125 is an Au layer; the over-etch layer 126 is a Pt layer; the ohmic contact layer 127 is a Cr layer.
According to the flip LED chip of the embodiment of the invention, the metal reflectivity of the side, close to the P-type semiconductor layer 113, of the P-type electrode 12 is effectively enhanced by adjusting the structure of the P-type electrode 12, so that more light from the P-type semiconductor layer 113 is reflected; the reflective layer 123 does not form an ohmic contact with the P-type semiconductor layer 113, so that current passing through the P-type electrode 12 does not vertically flow into the P-type semiconductor layer 113, and thus a current blocking layer is not required; the protective layer 124 can prevent the underlying active metal Al from oxidizing or migrating; the conductive layer 125 has higher conductivity and is responsible for long-distance lateral current transmission; the over-etching layer 126 is responsible for ensuring that the conductive through hole arranged above the P-type electrode 12 is completely etched, and preventing the contact surface between the bonding pad and the P-type electrode 12 from being provided with an oxide layer, so that the voltage of the LED chip is overhigh; the ohmic contact layer 127 forms ohmic contact with the current spreading layer 13, and increases the ohmic contact area of the current spreading layer 13 and the P-type electrode 12, thereby effectively reducing the operating voltage of the LED chip.
The thickness of the reflective layer 123 is betweenThe Ni layer and the Pt layer or the Ti layer and the Pt layer of the protection layer 124 are respectively between +.>The thickness of the conductive layer 125 is between +.>The thickness of the over-etch layer 126 is between +.>The ohmic contact layer 127 has a thickness of +.>The thickness of the reflective layer 123 is less than->The reflectivity is reduced, the emission effect is reduced, and the thickness is between +.>Can meet the reflectivity requirement, and has a thickness greater than +.>The Al layer expands more by heating, more protective layer 124 is required, and too thick a thickness causes an increase in cost; if the thickness of the protective layer 124 is too small, the coating property of the reflective layer 123 is too poor, so that the reflective layer 123 cannot be protected from oxidation migration, and the cost is increased due to too much thickness; the conductive layer 125 mainly plays a role in current transmission, the thicker the thickness is, the better the conductive effect is, the lower the working voltage of the LED chip is, and of course, the cost is increased due to the excessive thickness; the thickness of the over-etched layer 126 is less thanThe situation that the P-type conductive through holes on the P-type electrodes are not completely etched easily occurs, so that the voltage of the LED chip is higher, and the cost is increased due to the fact that the thickness of the LED chip is too thick; ohmic contact layer 127 has a thickness of less than->Cannot form ohmic contact with the current spreading layer 13 arranged on the LED chip, so that the working voltage of the LED chip is higher than +.>Can be shaped in thicknessAn ohmic contact is made, and of course, an increase in thickness causes an increase in cost.
In this embodiment, the protective layer 124 is a structure formed by periodically stacking Ni layers and Pt layers, and the number of cycles is 2-4, and in practice, the number of cycles is 2.
The P-type electrode 12 is gradually narrowed along the growth direction of the chip, and the included angle between the side surface of the P-type electrode 12 and the P-type semiconductor layer 113 is 5-30 degrees; the smaller angle can ensure that the thickness of the current expansion layer 13 coated on the side surface of the P-type electrode 12 is close to the thickness of the P-type electrode 12, and effectively prevent the situation that the working voltage of the LED chip is increased due to the fact that the thickness of the current expansion layer 13 on the side surface of the P-type electrode 12 is too thin; in this embodiment, the included angle between the side surface of the P-type electrode 12 and the P-type semiconductor layer 113 is 27 °.
In this embodiment, the P-type electrode 12 includes a P-type disc portion 121 and a P-type current transmission strip portion 122, the P-type disc portion 121 is electrically connected to the P-type pad 161, and is used for guiding current, and the P-type current transmission strip portion 122 is used for long-distance current transmission; the P-type disc part 121 is projected to be circular, the diameter of the circular part is 15um-35um, the P-type current transmission strip part 122 is projected to be rectangular, the width is 2um-10um, and the length is determined according to the length of the LED chip; the total area of the P-type electrode 12 accounts for 1% -5% of the area of the P-type semiconductor layer 113; in this embodiment, the diameter of the P-type disc portion 121 is 30um, the width of the P-type current transmission stripe portion 122 is 7um, and the total area of the P-type electrode 12 occupies 3% of the area of the P-type semiconductor layer 113.
The distance between the edge of the current spreading layer 13 and the edge of the P-type semiconductor layer 113 is 3 μm-10 μm; the LED chip can be prevented from being turned on under reverse current, so that the LED chip is prevented from being invalid; in the present embodiment, the current spreading layer 13 is disposed on the P-type semiconductor layer 113 except for the portion disposed on the P-type electrode 12, and the area of the current spreading layer 13 is smaller than that of the P-type semiconductor layer 113, and the current spreading layer 13 may be In 2 O 3 One of the layer, snO layer, znO layer and ITO layer with thickness betweenThe current expansion layer 13 is provided with an expansion layer through hole 131 above the P-type disc part 121 to ensure the P-type bonding pad 161 and the P-type electricityConnection of the poles 12; the projection area of the expansion layer through hole 131 is smaller than the area of the P-type disc part 121; in this embodiment, the distance between the edge of the current spreading layer 13 and the edge of the P-type semiconductor layer 113 is 5 μm, the current spreading layer 13 is an ITO layer, and the thickness is
The flip-chip light emitting diode chip further comprises a Bragg reflection layer 15 laminated on the current spreading layer 13, the Bragg reflection layer 15 covers the N-type electrode 14, and the Bragg reflection layer 15 is composed of TiO 2 And SiO 2 The alternating lamination is formed, and the number of the alternating lamination periods is 20-40; the bragg reflection layer 15 is responsible for reflecting light from the P-type semiconductor layer 113 out from underneath the substrate 10; in this embodiment, the number of cycles in which the bragg reflection layers 15 are alternately laminated is 30.
The Bragg reflection layer 15 is laminated with a P-type bonding pad 161 and an N-type bonding pad 162, the Bragg reflection layer 15 is provided with a P-type Bragg reflection layer through hole 151 and an N-type Bragg reflection layer through hole 152, the P-type bonding pad 161 penetrates through the P-type Bragg reflection layer through hole 151 and penetrates through the current expansion layer 13 so as to be electrically connected with the P-type electrode 12, and the N-type bonding pad 162 penetrates through the N-type Bragg reflection layer through hole 152 to be electrically connected with the N-type electrode 14; in this embodiment, the P-type bragg reflector layer via 151 corresponds to the extension layer via 131.
The flip-chip light-emitting diode chip is also provided with an isolation groove 114, and the Bragg reflection layer 15 covers the isolation groove 114; the isolation groove 114 is disposed around the LED chip, and oxidation and corrosion of the N-type semiconductor layer 111 and the active light emitting layer 112 by external moisture and contaminants can be prevented by pre-disposing the isolation groove 114 and then coating the isolation groove 114 with the insulating bragg reflection layer 15.
The N-type electrode 14 is formed by alternately laminating one or more of a Cr layer, a Ni layer, an Al layer, an ALCu layer, a Ti layer, a Pt layer, an Au layer, an Ag layer, a Cu layer and an Sn layer; in this embodiment, the N-type electrode 14 also includes an N-type disk portion 141 and an N-type current transmission bar portion 142, and the N-type electrode 14 is an ALCu layer.
Correspondingly, the invention also provides a preparation method of the flip LED chip, which is used for preparing the flip LED chip, and comprises the following steps:
s1: providing a substrate 10; the substrate 10 is made of a light-transmitting material and can be a GaN layer, an AlN layer or an Al2O3 layer; in this embodiment, the substrate 10 is a GaN layer.
S2: an N-type semiconductor layer 111, an active light emitting layer 112, and a P-type semiconductor layer 113 are sequentially grown on the substrate 10; the specific implementation thereof is well known to those skilled in the art and will not be described in detail herein.
S3: depositing a P-type electrode 12 on the P-type semiconductor layer 113, wherein the P-type electrode 12 comprises a reflecting layer 123, a protective layer 124, a conductive layer 125, an over-etching layer 126 and an ohmic contact layer 127 which are sequentially deposited along the growth direction of the chip; the reflective layer 123 is an Al layer, the protective layer 124 is a periodically laminated structure of a Ni layer and a Pt layer or a Ti layer and a Pt layer, the conductive layer 125 is an Au layer or a Cu layer, the over-etched layer 126 is any one of the Ni layer, the Ti layer, and the Pt layer, and the ohmic contact layer 127 is a Cr layer or a Ni layer.
Specifically, a negative photoresist is coated on the surface of the P-type semiconductor layer 113, then exposed, developed, and part of the photoresist is removed to form a preset P-type electrode 12 photoresist pattern, and then an Al layer, a periodically laminated Ti layer, a Pt layer, an Au layer, a Pt layer, and a Cr layer (each layer having a thickness of sequentially) Then, the metal except the P-type electrode 12 is removed by a blue film peeling process, and then the photoresist is removed to obtain the P-type electrode 12.
S4: depositing a current spreading layer 13 covering the P-type electrode 12 on the P-type semiconductor layer 113; specifically, the thickness of the P-type semiconductor layer 113 and the P-type electrode 12 is deposited by magnetron sputteringThen coating photoresist on the surface of the ITO layer, exposing and developing to remove part of the photoresist to expose part of the ITO layer, removing the exposed ITO layer by using ITO corrosive liquid, and removing the photoresist to obtain the current expansion layer 13.
S5: an isolation trench 114 is prepared on the N-type semiconductor layer 111; specifically, photoresist is coated on the surfaces of the current spreading layer 13 and the P-type semiconductor layer 113, then part of the photoresist positioned on the P-type semiconductor layer 113 is removed by exposure and development, part of the P-type semiconductor layer 113 is exposed, then the exposed P-type semiconductor layer 113 and the active light emitting layer 112 below the P-type semiconductor layer 113 are removed by utilizing an inductively coupled plasma etching process, part of the N-type semiconductor layer 111 is exposed, then the photoresist is removed, and the part of the N-type semiconductor layer 111 is the N-type semiconductor conductive step 115 and is used for depositing the N-type electrode 14 on the N-type semiconductor layer and preparing the isolation groove 114; photoresist is coated on the N-type semiconductor layer 111, the P-type semiconductor layer 113 and the current expansion layer 13, then part of the photoresist is exposed and developed to expose part of the N-type semiconductor layer 111 around the LED chip, then the exposed N-type semiconductor layer 111 is removed by utilizing an inductively coupled plasma etching process, and isolation grooves 114 are formed around the LED chip.
S6: depositing an N-type electrode 14 on the N-type semiconductor layer 111; specifically, a negative photoresist is coated on the surfaces of the isolation groove 114, the N-type semiconductor layer 111, the P-type semiconductor layer 113 and the current spreading layer 13, then the photoresist on the N-type semiconductor conductive step 115 is partially removed by exposure and development, a preset N-type electrode 14 photoetching pattern is formed on the N-type semiconductor conductive step 115, and then an ALCu layer (with thickness of) Then, the metal except the N-type electrode 14 is removed by a blue film peeling process, and then the photoresist is removed to form the N-type electrode 14.
S7: depositing a Bragg reflection layer 15 on the current spreading layer 13, wherein the Bragg reflection layer 15 covers the isolation groove 114; specifically, 30 groups of TiO were sequentially deposited on the surfaces of the isolation trench 114, the N-type semiconductor layer 111, the N-type electrode 14, the P-type semiconductor layer 113, and the current spreading layer 13 by an electron beam deposition process 2 And SiO 2 Laminating to form Bragg reflection layer 15, coating photoresist on the surface of Bragg reflection layer 15, exposing, and developing to remove part of photoresistAnd then removing the exposed Bragg reflection layer 15 on the N-type disc part 141 and the P-type disc part 121 by using an inductively coupled plasma etching process to form an N-type Bragg reflection layer through hole 152, and removing the exposed Bragg reflection layer 15 on the P-type disc part 121 and the current expansion layer 13 below the Bragg reflection layer 15 to form a P-type Bragg reflection layer through hole 151 and an expansion layer through hole 131.
S8: p-type bonding pads 161 and N-type bonding pads 162 are respectively deposited on the Bragg reflection layer 15; specifically, the surface of the bragg reflection layer 15, the surface of the P-type bragg reflection layer through hole 151 and the surface of the N-type bragg reflection layer through hole 152 are coated with negative photoresist, then part of the photoresist is removed by exposure and development, a pad layer preset photoresist pattern is formed, and then a Cu layer (thickness is formed by evaporation of an electron beam evaporation process) Then, the metal except the pad is removed by a blue film peeling process, and then the photoresist is removed, forming a P-type pad 161 and an N-type pad 162.
According to the flip LED chip manufacturing method, the metal reflectivity of the side, close to the P-type semiconductor layer 113, of the P-type electrode 12 is effectively enhanced by adjusting the structure of the P-type electrode 12, so that more light from the P-type semiconductor layer 113 is reflected; the reflective layer 123 does not form an ohmic contact with the P-type semiconductor layer 113, so that current passing through the P-type electrode 12 does not vertically flow into the P-type semiconductor layer 113, and thus a current blocking layer is not required; the protective layer 124 can prevent the underlying active metal Al from oxidizing or migrating; the conductive layer 125 has higher conductivity and is responsible for long-distance lateral current transmission; the over-etching layer 126 is responsible for ensuring that the conductive through hole arranged above the P-type electrode 12 is completely etched and preventing the contact surface between the P-type bonding pad 161 and the P-type electrode 12 from being provided with an oxide layer, so that the voltage of the LED chip is overhigh; the ohmic contact layer 127 forms ohmic contact with the current spreading layer 13, and increases the ohmic contact area of the current spreading layer 13 and the P-type electrode 12, thereby effectively reducing the operating voltage of the LED chip.
The chips of example 1 and comparative example were prepared to 10×24mil using the same chip process conditions, 500 LED chips were extracted, and the photoelectric properties of the chips were tested at 60mA current, the brightness of the chips obtained in example 1 was 116.18mw by the test instrument, 103.6% of the brightness of the chips obtained in comparative example, the operating voltage was 2.715V, and other good electrical properties were obtained, and specific results are shown in table 1.
Example 2
This embodiment differs from embodiment 1 in that: the thickness of the reflective layer 123 in this embodiment isThe protective layer 124 has a thickness +.>Conductive layer 125 has a thickness->The thickness of the over-etched layer 126 is +.>Ohmic contact layer 127 has a thickness->
The chips of example 2 and comparative example were prepared to 10×24mil using the same chip process conditions, 500 LED chips were extracted, and the photoelectric properties of the chips were tested at 60mA current, and the brightness of the chips obtained in example 2 was 112.74mw, which was 100.5% of the brightness of the chips obtained in comparative example, the operating voltage was 2.729V, and other good electrical properties were obtained by testing the chips with a test instrument, and specific results are shown in table 1.
Example 3
This embodiment differs from embodiment 1 in that: the thickness of the reflective layer 123 in this embodiment isThe protective layer 124 has a thickness +.>Conductive layer 125 has a thickness->The thickness of the over-etched layer 126 is +.>Ohmic contact layer 127 has a thickness->
The chips of example 3 and comparative example were prepared to 10×24mil using the same chip process conditions, 500 LED chips were extracted, and the photoelectric properties of the chips were tested at 60mA current, and the brightness of the chips obtained in example 3 was 115.69mw, which was 103.2% of the brightness of the chips obtained in comparative example, and the operating voltage was 2.718V, and other good electrical properties were obtained, with specific results shown in table 1.
Example 4
This embodiment differs from embodiment 1 in that: the thickness of the reflective layer 123 in this embodiment isThe protective layer 124 has a thickness +.>Conductive layer 125 has a thickness->The thickness of the over-etched layer 126 is +.>Ohmic contact layer 127 has a thickness->
The chips of example 4 and comparative example were prepared to 10×24mil using the same chip process conditions, 500 LED chips were extracted, and the photoelectric properties of the chips were tested at 60mA current, and the brightness of the chips obtained in example 4 was 114.95mw, which was 102.4% of the brightness of the chips obtained in comparative example, the operating voltage was 2.722V, and other good electrical properties were obtained by testing the chips with a test instrument, and specific results are shown in table 1.
Example 5
This embodiment differs from embodiment 1 in that: the thickness of the reflective layer 123 in this embodiment isThe protective layer 124 has a thickness +.>Conductive layer 125 has a thickness->The thickness of the over-etched layer 126 is +.>Ohmic contact layer 127 has a thickness->
The chips of example 5 and comparative example were prepared to 10×24mil using the same chip process conditions, 500 LED chips were extracted, and the photoelectric properties of the chips were tested at 60mA current, and the brightness of the chips obtained in example 5 was 113.23mw, which was 101% of the brightness of the chips obtained in comparative example, the operating voltage was 2.726V, and other good electrical properties were obtained by testing the chips with a test instrument, and specific results are shown in table 1.
Table 1: partial parameter comparison of each example and comparative example and comparison table of corresponding brightness and working voltage
As can be seen from the above table, the flip LED chip provided by the present invention has the P-type electrode 12 sequentially laminated along the chip growth directionThe reflective layer 123 is an Al layer, the protective layer 124 is a periodically laminated structure of a Ni layer and a Pt layer or a Ti layer and a Pt layer, the conductive layer 125 is an Au layer or a Cu layer, the over-etched layer 126 is any one of the Ni layer, the Ti layer and the Pt layer, and the ohmic contact layer 127 is a Cr layer or a Ni layer; and the thickness of the reflecting layer 123 is betweenThe thickness of the protection layer 124 is between +.>The thickness of the conductive layer 125 is between +.>The thickness of the over-etch layer 126 is between +.>The ohmic contact layer 127 has a thickness betweenCompared with the comparative example, the chip prepared by the preparation method has obviously improved brightness and effectively reduced working voltage; namely, by adjusting the structure of the P-type electrode 12, the metal reflectivity of the P-type electrode 12 on the side close to the P-type semiconductor layer 113 is effectively enhanced, so that more light from the P-type semiconductor layer 113 is reflected; the reflective layer 123 does not form an ohmic contact with the P-type semiconductor layer 113, so that current passing through the P-type electrode 12 does not vertically flow into the P-type semiconductor layer 113, and thus a current blocking layer is not required; the protective layer 124 can prevent the underlying active metal Al from oxidizing or migrating; the conductive layer 125 has higher conductivity and is responsible for long-distance lateral current transmission; the over-etching layer 126 is responsible for ensuring that the conductive through hole arranged above the P-type electrode 12 is completely etched and preventing the contact surface between the P-type bonding pad 161 and the P-type electrode 12 from being provided with an oxide layer, so that the voltage of the LED chip is overhigh; the ohmic contact layer 127 forms an ohmic contact with the current spreading layer 13, increases the ohmic contact area of the current spreading layer 13 with the P-type electrode 12,thereby effectively reducing the working voltage of the LED chip.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The above additional technical features can be freely combined and superimposed by a person skilled in the art without conflict.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (10)
1. The flip LED chip at least comprises a substrate, and an N-type semiconductor layer, an active light-emitting layer and a P-type semiconductor layer which are sequentially laminated on the substrate, and is characterized in that a current expansion layer is laminated on the P-type semiconductor layer, a P-type electrode is arranged between the P-type semiconductor layer and the current expansion layer, an N-type semiconductor conductive step is arranged on the N-type semiconductor layer, and an N-type electrode is arranged on the N-type semiconductor conductive step;
the P-type electrode comprises a reflecting layer, a protective layer, a conductive layer, an over-etching layer and an ohmic contact layer which are sequentially laminated along the growth direction of the chip, wherein the reflecting layer is an Al layer, the protective layer is a structure of periodically laminating a Ni layer and a Pt layer or a Ti layer and a Pt layer, the conductive layer is an Au layer or a Cu layer, the over-etching layer is any one of the Ni layer, the Ti layer and the Pt layer, and the ohmic contact layer is a Cr layer or a Ni layer.
2. According to claimThe flip-chip light emitting diode chip as set forth in 1, wherein said reflective layer has a thickness betweenThe thickness of the Ni layer and the Pt layer or the Ti layer and the Pt layer of the protective layer is between +.>The thickness of the conductive layer is between +.>The thickness of the over-etched layer is between +.>The thickness of the ohmic contact layer is between +.>
3. The flip-chip light emitting diode chip of claim 1, wherein the P-type electrode is tapered along a chip growth direction, and an included angle between a side surface of the P-type electrode and the P-type semiconductor layer is between 5 ° and 30 °.
4. The flip-chip light emitting diode chip of claim 1, wherein the current spreading layer edge is between 3 μm and 10 μm from the P-type semiconductor layer edge.
5. The flip-chip light emitting diode chip of claim 1, further comprising a bragg reflector layer laminated on the current spreading layer, the bragg reflector layer covering the N-type electrode, the bragg reflector layer being comprised of TiO 2 And SiO 2 The alternating layers are formed by periodic alternating layers, and the number of the periodic numbers of the alternating layers is 20-40.
6. The flip-chip light emitting diode chip of claim 5, wherein a P-type bonding pad and an N-type bonding pad are laminated on the bragg reflection layer, a P-type bragg reflection layer through hole and an N-type bragg reflection layer through hole are formed on the bragg reflection layer, the P-type bonding pad penetrates through the P-type bragg reflection layer through hole and penetrates through the current spreading layer to be electrically connected with the P-type electrode, and the N-type bonding pad penetrates through the N-type bragg reflection layer through hole to be electrically connected with the N-type electrode.
7. The flip-chip led chip of claim 5, further comprising isolation trenches 114, wherein said bragg reflector layer covers said isolation trenches.
8. The flip-chip light emitting diode chip of claim 1, wherein the N-type electrode is composed of one or more of Cr layer, ni layer, al layer, ALCu layer, ti layer, pt layer, au layer, ag layer, cu layer, and Sn layer alternately stacked.
9. A method of fabricating a flip-chip light emitting diode chip for fabricating the flip-chip light emitting diode chip of claims 1-8, the method comprising:
providing a substrate;
sequentially growing an N-type semiconductor layer, an active light emitting layer and a P-type semiconductor layer on the substrate;
depositing a P-type electrode on the P-type semiconductor layer, wherein the P-type electrode comprises a reflecting layer, a protective layer, a conducting layer, an over-etching layer and an ohmic contact layer which are sequentially deposited along the growth direction of the chip;
depositing a current expansion layer covering the P-type electrode on the P-type semiconductor layer;
preparing an isolation groove on the N-type semiconductor layer;
depositing an N-type electrode on the N-type semiconductor layer;
depositing a Bragg reflection layer on the current expansion layer, wherein the Bragg reflection layer covers the isolation groove;
p-type bonding pads and N-type bonding pads are respectively deposited on the Bragg reflection layer.
10. The method for manufacturing a flip-chip light emitting diode chip according to claim 9, wherein the reflective layer is an Al layer, the protective layer is a periodically laminated structure of a Ni layer and a Pt layer or a Ti layer and a Pt layer, the conductive layer is an Au layer or a Cu layer, the over-etched layer is any one of the Ni layer, the Ti layer and the Pt layer, and the ohmic contact layer is a Cr layer or a Ni layer.
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