CN114937724A - UVC-LED chip and manufacturing method thereof - Google Patents

UVC-LED chip and manufacturing method thereof Download PDF

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CN114937724A
CN114937724A CN202210330341.XA CN202210330341A CN114937724A CN 114937724 A CN114937724 A CN 114937724A CN 202210330341 A CN202210330341 A CN 202210330341A CN 114937724 A CN114937724 A CN 114937724A
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layer
algan
uvc
gan
led chip
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汤磊
徐丽琼
吴叶楠
姜栋裕
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Jiaxing Dingga Semiconductor Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen
    • H01L33/325—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen characterised by the doping materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds
    • H01L33/0066—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound
    • H01L33/007—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound comprising nitride compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/36—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
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    • H—ELECTRICITY
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    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/44—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the coatings, e.g. passivation layer or anti-reflective coating
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Abstract

The invention discloses a UVC-LED chip and a manufacturing method thereof. According to the UVC-LED chip provided by the invention, the etching stop layer with relatively large difference of etching rates is inserted in the growth process of the LED epitaxial layer, so that only the P-GaN layer can be selectively etched, the P-GaN layer is selectively left, and the other P-electrode layer is completely covered. Since a part of the P-GaN layer is remained in the P-electrode layer, ohmic contact with the P-electrode layer is easily formed through the P-electrode layer, driving voltage can be reduced, P-GaN does not exist or is negligible in most of the P-electrode layer, and reflectivity through the P-electrode layer is improved by minimizing light loss caused by light absorption occurring at the active layer, thereby effectively improving light efficiency of the UVC-LED. The manufacturing method of the UVC-LED chip provided by the invention is stable in process, simple to operate and suitable for large-scale production in factories.

Description

UVC-LED chip and manufacturing method thereof
Technical Field
The invention relates to the technical field of semiconductors, in particular to a UVC-LED chip and a manufacturing method thereof.
Background
Recently, sterilization and disinfection have been receiving more and more attention due to environmental pollution, bacteria, and the like, and conventional sterilization methods include heat/steam sterilization, chemical sterilization, light sterilization, and the like.
The heat/steam sterilization is the most common sterilization method, and is mainly used for materials which do not deform at 100 ℃ like metal and metal products, and if the materials do not have such characteristics, the use of the heat/steam sterilization method is limited. Also, the heat/steam sterilization method requires direct exposure to heat/steam for sterilization effect, so its use is limited in the sterilization similar to that in a wide space range, and thus the main means for sterilization of the space is chemical sterilization.
The chemical sterilization method is to directly spray chemicals to a sterilization object for sterilization, and the chemicals are sprayed in a large space and on the surface of an object, so that bacteria on the surface of the object in the space can be effectively killed. However, although the chemical sterilization method can only remove bacteria and viruses temporarily and effectively, the effect is exhibited immediately after use, but bacteria and viruses increase again in characteristics, and therefore, sterilization using chemicals requires frequent and continuous sterilization treatment. However, when chemicals are used for sterilization, Chlorine (CI) series chemicals are used as main components of the chemicals, and although bacteria and viruses can be effectively removed, they are harmful to human bodies and need to be used carefully. Therefore, when using these drugs, attention must be paid so as not to be inhaled directly from the respiratory tract of the human body. Although chemical methods are advantageous for sterilization of surfaces to which bacteria and viruses can be directly contacted, they are not suitable for air sterilization, and one of the methods for minimizing human body harmfulness and even air sterilization is to use light sterilization.
The light source used in the conventional optical sterilization method is a mercury lamp, and since the commonly used mercury lamp uses a high-voltage electrical discharge effect, not only light having a wavelength required for sterilization but also light having other wavelengths are generated together. Especially 185nm light generated by mercury lamp, due to its ability to remove oxygen (O) from atmosphere 2 ) Conversion to ozone (O) 3 ) Of light energy inWhen a mercury lamp is used, ozone (O3) gas is generated together. Generally if ozone (O) 3 ) Since it is known that lung cancer is induced by inhalation of gas into the human body, careful use is required for sterilization using a mercury lamp. Because of the 2020 start-up of mercury lamps using limited protocols, research into new light sources that can replace mercury lamps has been developed, and UVC LEDs have grown in the arena as the closest light source.
Blue led developed by doctor of japan Zhongcun in 1993 has led to vigorous and continuous development of the technology, and has now been widely used in the fields of lighting, displays, and the like in our lives. Unlike other light sources, LEDs are suitable for many industries because they can selectively produce specific wavelengths as desired. InGaN based on Blue LEDs cannot produce a wavelength band below UVA due to a bandgap (energy band gap) problem. The wavelength region having the bactericidal action against bacteria and viruses is the 265nm region, and in order to emit light in this wavelength region, an AlGaN material having a higher band gap than InGaN is used. Recently, devices have been developed which can produce high quality AlGaN layers and UVC LEDs emitting 275nm wavelengths. In the UVC LED, as in the conventional blue LED, although it is not so difficult to perform a process of using Si and Mg as a P-, N-electrode-doped material for supplying current, and doping an AlGaN layer with Si, which is an N-electrode-doped material, Mg used as a P-electrode material is doped with AlGaN in a proper amount, which is difficult.
Like the conventional blue LED, the UVC LED uses GaN doped with Mg as a P-electrode layer. When the pGaN layer is used as the p-electrode layer, since the threshold voltage is lower than that of AlGaN, there is an advantage that the driving voltage of the LED can be reduced. However, the p-type GaN layer used as the p-electrode layer has a GaN absorption spectrum (GaN absorption spectrum), absorbs 275nm light, and absorbs 275nm light, which is a main cause of the decrease in the light efficiency of the UVC LED. To solve such a problem, the p-electrode layer is replaced with an AlGaN layer other than the GaN layer. However, the p-type AlGaN layer used in UVC has a high AI content due to the use of an Electron blocking layer (Electron blocking layer), and it is difficult to mix Mg. But in order to manufacture a UVC LED with high light efficiency, a pAlGaN layer other than the conventional pGaN layer should be used. Therefore, the kinds of metals used as the electrode layers and the fabrication process are very different, and thus the light efficiency of the UVC LED is relatively improved, but additional problems including the driving voltage are caused. The UVC LED manufactured by the driving voltage improvement has low reliability and low light efficiency.
Disclosure of Invention
The invention aims to provide a UVC-LED chip and a manufacturing method thereof aiming at the defects in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
the UVC-LED chip comprises a substrate, an epitaxial layer, an N electrode layer and a P electrode layer, wherein the epitaxial layer, the N electrode layer and the P electrode layer are arranged on the substrate, the epitaxial layer comprises an AlN layer, an AlGaN layer, an N-AlGaN layer, an MQW light-emitting layer, a P-AlGaN layer and a P-GAN layer which are sequentially arranged from bottom to top, an ESL etching stop layer is inserted between the P-AlGaN layer and the P-GaN layer, and the ESL etching stop layer selectively etches the P-GaN layer to enable the P-GaN layer to be divided into two parts, wherein the thickness of one part of the P-GaN layer is not less than that of the P-GaN layer
Figure BDA0003575056850000031
The other part of the p-GaN layer has a thickness less than that of the
Figure BDA0003575056850000032
The P-GaN layer is completely covered with the P electrode layer, and the N electrode layer is arranged on the N-AlGaN layer.
Further, the composition of the AlGaN layer is AlGaN v N，0≤v<0.5; the thickness of the film is 1-3 μm.
Further, the component of the n-AlGaN layer is n-AlGawN, and w is more than or equal to 0 and less than or equal to 0.6; the sum of the thicknesses of the n-AlGaN layer and the AlGaN layer is greater than 5 μm.
Further, the MQW light-emitting layer has AlGa x N and AlGa y N, wherein 0<x≤0.9，0<y≤0.85，x+w>y，x>y≥w。
Further, the composition of the p-AlGaN layer is p-AlGaN z N, z is more than or equal to 0 and less than or equal to 0.6; having a thickness of
Figure BDA0003575056850000033
Further, the thickness of the p-GAN layer is
Figure BDA0003575056850000041
The invention also provides a manufacturing method of the UVC LED chip, which comprises the following steps:
step S1, providing a sapphire substrate, and growing an ALN layer, an AlGaN layer, an n-AlGaN layer, an MQW light-emitting layer, a p-AlGaN layer, an ESL etching stop layer and a p-GAN layer on the substrate in sequence by adopting an MOCVD system to obtain an epitaxial layer;
step S2, carrying out graphical etching on the epitaxial layer obtained in the step S1, exposing the N-type AlGaN structure of part of the N-type AlGaN layer, and preparing an N electrode layer on the N-type AlGaN structure;
and step S3, preparing a P electrode on the P-GAN layer of the epitaxial layer obtained in the step S1, and obtaining the UVC-LED chip with the inverted vertical structure.
Further, the AlN growth conditions of the ESL etching stop layer comprise the temperature of 1100-1350 ℃, 0.5-40L of ammonia gas and the concentration of 10-800 mu mol of trimethylaluminum; the growth conditions of the p-GaN layer comprise the temperature of 850-1100 ℃, 0.5-40L of ammonia gas, the concentration of trimethyl gallium of 5-400 mu mol and the concentration of magnesium cyclopentadienyl of 0.1-1000 mu mol.
Furthermore, the growth conditions of the n-AlGaN layer comprise the temperature of 1100-1350 ℃, 0.5L-40L of ammonia gas, the concentration of trimethyl aluminum of 10 mu mol-800 mu mol, the concentration of trimethyl gallium of 5 mu mol-400 mu mol and the concentration of silane of 1 multiplied by 10 -6 ～1×10 1 μmol。
The invention has the beneficial effects that:
(1) according to the UVC-LED chip provided by the invention, the etching stop layer with relatively large difference of etching rates is introduced in the growth process of the LED epitaxial layer, so that only the P-GaN layer can be selectively etched, the P-GaN layer is selectively left, and the other P-electrode layer is completely covered. Since a part of the P-GaN layer is remained in the P-electrode layer, ohmic contact with the P-electrode layer is easily formed through the P-GaN layer, driving voltage can be reduced, P-GaN does not exist or P-GaN is negligible in most of the P-electrode layer, and reflectivity through the P-electrode layer is improved by minimizing light loss caused by light absorption occurring at the active layer, thereby effectively improving light efficiency of the UVC LED.
(2) The manufacturing method of the UVC-LED chip provided by the invention is stable in process, simple to operate and suitable for large-scale production in factories.
Drawings
Fig. 1 is a structural view of a UVC-LED chip of the present invention;
FIG. 2 is a flow chart of a UVC-LED chip manufacturing process according to the present invention;
fig. 3 is a graph showing the correspondence between the optical intensity and the forbidden bandwidth of a gallium nitride material at a high temperature (T ═ 4K);
FIG. 4 is a graph showing the difference in etching rates between GaN and AlN;
fig. 5 is a schematic view of an epitaxial structure of a UVC LED chip of comparative example 1;
FIG. 6 is a spectrum of GaN absorption and emission;
fig. 7 is a schematic view of an epitaxial structure of a UVC LED chip of comparative example 2;
FIG. 8a is a graph of output power versus voltage for a UVC LED chip of p-GaN construction;
FIG. 8b is a graph of output power versus voltage for a UVC LED chip of a p-AlGaN structure;
FIG. 9 is a schematic view showing the light emitting direction and the heat generating direction of an LED and a mercury lamp;
fig. 10 is a real picture of the UVC LED chip prepared in example 1.
Illustration of the drawings:
1. a substrate; 2. an epitaxial layer; 21. an AlN layer; 22. an AlGaN layer; 23. an n-AlGaN layer; 24. an MQW light emitting layer; 25. a p-AlGaN layer; 26. a p-GAN layer; 261. thickness of not less than
Figure BDA0003575056850000051
Figure BDA0003575056850000052
A p-GAN layer of (a); 262. thickness ofIs less than
Figure BDA0003575056850000053
A p-GAN layer of (2); 27. an ESL etch stop layer; 3. an N electrode layer; 4. and a P electrode layer.
Detailed Description
The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.
As shown in figure 1, the UVC-LED chip comprises a substrate 1, an epitaxial layer 2, an N electrode layer 3 and a P electrode layer 4 which are arranged on the substrate 1, wherein the epitaxial layer comprises an AlN layer 21, an AlGaN layer 22, an N-AlGaN layer 23, an MQW light-emitting layer 24, a P-AlGaN layer 25 and a P-GAN layer 26 which are sequentially arranged from bottom to top, an ESL etching stop layer 27 is inserted between the P-AlGaN25 layer and the P-GaN26 layer, the ESL etching stop layer 27 selectively etches the P-GaN layer 26 to enable the P-GaN layer to be divided into two parts, wherein the thickness of one part of the P-GaN layer 261 is not less than that of the P-GaN layer
Figure BDA0003575056850000061
The other part of the p-GaN layer 262 has a thickness smaller than that of the
Figure BDA0003575056850000062
The P-GaN layer 26 is entirely covered with the P electrode layer 4, and the N electrode layer 3 is disposed on the N-AlGaN layer 23.
Fig. 2 is a flow chart of the UVC-LED chip manufacturing method according to the present invention. It should be noted that, during the process of preparing the UVC-LED chip of the present invention using the MOCVD system, the temperature of the commercial MOCVD can be raised to 1200 ℃. Such MOCVD has difficulty growing high quality AlGaN or AlN layers required for UVB, UVC LED epitaxy. Therefore, MOCVD capable of rising to 1500 degrees is required, which requires modification of main components of existing MOCVD or use of new MOCVD capable of rising to 1500 degrees.
For the substrate for MOCVD, a Sapphire substrate, AlN or AlN on Sapphire, or the like can be used. The size can reach 2inch to 6 inch.
The UVC used in UVB/UVC epicxy has a wavelength range of 200nm to 290nm and a UVB wavelength range of 290nm to 320 nm.
Example 1
The manufacturing process of the UVC-LED chip is as follows:
1. growth of AlN layer
As shown in fig. 7, the UVB/UVC Epitaxy wafer was fabricated using a sapphire substrate as follows: an AlN buffer layer is formed on sapphire by MOCVD at a high temperature (1500 ℃ C.), and in this case, NH3 gas 0.1L-20L and TMAl (trimethylaluminum) 0.5. mu. mol-300. mu. mol are used at a growth temperature of 700 ℃ to 1100 ℃ for growing the AlN buffer layer. As carrier gas for moving TMAI, H was used 2 (Hydrogen). The AlN buffer thickness grown under such conditions exists
Figure BDA0003575056850000063
Figure BDA0003575056850000071
In the meantime.
After the AlN buffer layer grows, the temperature of the MOCVD reaction chamber is increased to 1150-1400 ℃, so that the AlN layer grows to 1-3 mu m. NH3 gas is 0.5-40L, and the concentration of TMAl is 10-800. mu. mol.
2、AlGa v N(0≤v<0.5) growth
Then adjusting the growth temperature to 1100-1350 ℃ to ensure that the AlGa v N(0≤v<0.5) increase by 1 to 3 μm. NH (NH) 3 gas is 0.5L-40L, TMAl concentration is 10 mu mol-800 mu mol, TMGa concentration is 4 mu mol-400 mu mol. AlGa grown at this time v N(0≤v<0.5) the growth method of the layer can be performed by:
the method comprises the following steps: as shown in fig. 3, starting from the contact AlN, the inverse method of the manner of providing TMGa, the exponential function method, the staircase method.
Fig. 3 shows the correspondence between the optical intensity and the energy gap of the gallium nitride material at high temperature (T ═ 4K), and indicates the optical density index of the gallium nitride material in the growth environment. A forbidden bandwidth and optical density rating of 3.4eV also shows excellent semiconductor material properties of gallium nitride materials.
The second method comprises the following steps: AlGa of AlN layer and target v v N(0≤v<0.5) method of pairing
(1) Thickness variation of two layers
Method of varying the thickness of one layer over another: the layer of constant thickness being maintained by an AlN layer and the layer of increasing thickness by an AlGaN layer v N(0≤v<0.5) layer by layer. The AlN layer with a certain thickness is kept at the same time
Figure BDA0003575056850000072
Of increased thickness v N(0≤v<0.5) thickness of the layer
Figure BDA0003575056850000073
In between, AlN layer and AlGa v N(0≤v<0.5) is formed, and the number of the laminated layers is 10-100.
The method for reducing the thickness of one layer and increasing the thickness of the other layer comprises the following steps: the layer of reduced thickness is an AlN layer and the layer of increased thickness is an AlGaN layer v N(0≤v<0.5) layers. An AlN layer made of
Figure BDA0003575056850000074
Gradually decrease to less
Figure BDA0003575056850000075
AlGa v N(0≤v<0.5) layers from
Figure BDA0003575056850000076
Is gradually increased to
Figure BDA0003575056850000077
AlN layer and AlGa v N(0≤v<0.5) one layer, and the number of the laminated layers is between 10 and 100.
(2) Method for increasing number of same thickness stacks
The thickness of the AlN layer and AlGavN (v is more than or equal to 0)<0.5) thickness of the layers are the same and the two layers constitute one, stack. The number of the laminated layers is about 10-100, and the thickness of the same growth is in the range
Figure BDA0003575056850000081
In the meantime.
(3) Adding TMGa to the growth of AlN layer, growing AlGa v N(0≤v<0.5) method of layer
The input time of TMGa was adjusted while growing the AlN layer. In this case, the concentration of TMGa is 0.05 to 50. mu. mol, and the time for charging TMGa is 1 second to 2 min. Although the initial TMGa time is short, the more TMGa is packed, the longer the TMGa input time is.
3、n-AlGa w N (w is more than or equal to 0 and less than or equal to 0.6) layer growth
AlGa v N(0≤v<0.5) Ga of the last surface constituting v and n-AlGa w W is compared with Ga used for N (0. ltoreq. w.ltoreq.0.6) layer, w>v。AlGa v N(0≤v<0.5) layer with n-AlGa w The reason why the composition of N (0. ltoreq. w.ltoreq.0.6) is not uniformly used is as follows:
stress generates a large number of dislocations inside the AlN layer due to the lattice difference of sapphire and AlN. To minimize the formation of AlN layers, AlGa is grown by the various methods described previously v N(0≤v<0.5) layer. However, when various methods are used, dislocation cannot be reduced surely, and Sapphire, AlN and AlGa cannot be reduced sufficiently v N(0≤v<0.5) lattice and tensile stress due to differences in thermal expansion. To reduce this effect, n-AlGa w Composition of N (w is more than or equal to 0 and less than or equal to 0.6) and AlGa v N(0≤v<0.5) are separated. This is because, for the occurrence of AlGaN-tunneling in the AlN layer v N(0≤v<0.5) dislocation continuously proceeding, and the crystal lattice becomes larger by the amount adjustment of Ga to decrease n-AlGa w The combined density of the N (w is more than or equal to 0 and less than or equal to 0.6) layers.
But n-AlGa w When N (w is more than or equal to 0 and less than or equal to 0.6) layer grows, the used growth temperature is 1100-1350 ℃, NH 3 Is 0.5L to 40L, TMAl is present in a concentration of 10. mu. mol to 800. mu. mol, and TMGa is present in a concentration of 5. mu. mol to 400. mu. mol. In addition, Silane SiH is used for preparing the doping source of the n-type semiconductor element by using Silane series gas 4 Or is Si 2 H 6 Using 50ppm/H 2 ～300ppm/H 2 At a concentration of 1x 10 -6 ～1x10 1 Mu mol. The thickness ranges from 2 μm to 3 μm.
Additional AlGa v N(0≤v<0.5) thickness and n-AlGa w The sum of the thicknesses of the N (0. ltoreq. w.ltoreq.0.6) layers is to exceed 5 μm.
4. MQW (active layer) growth
The light-emitting well layer and barrier functioning as a blocking hole and electron constitute a pair of active layers. Both Well and Barrier are composed of AlGaN, and can be recorded in more detail as follows. Well (AlGa) x N) is (0<x≤0.9),Barrier(AlGa y N) is (0<y is less than or equal to 0.85). In addition to the composition and n-AlGa w N (0. ltoreq. w. ltoreq.0.6) is x + w>y，x>y≥w。
The growth conditions of the active layer are growth temperature of 1100-1350 ℃ and NH 3 The concentration of TMAl is 10 to 800. mu. mol at 0.5 to 40L. This is similar or identical to the conditions of the previously grown layer. However, TMGa used for growth of the Well layer and barrier layer is similar to that of AlGa which is conventionally used v N(0≤v<0.5) layer and n-AlGa w The N (0. ltoreq. w.ltoreq.0.6) layer is different from that of TMGa, and 2 TMGa sources, i.e., TMGa #1 and #2, are used in the well and barrier.
The purpose of this is to maintain a certain Barrier (AlGa) y N)(0<y ≦ 0.85), the addition of TMGa #2 was provided for growth of Well, minimizing growth variation conditions at the epitax growth of Well and Barrier. In a general growth method, TMGa #1 used for growing a well layer and TMGa #2 used for a barrier layer were used. If so used, it is necessary to switch (switching) from TMGa #2 used in the first barrier layer to TMGa #1 required for well growth. In the MO source switching process, all TMGa is not supplied (1)<1sec) is responsible for growing the AlN layer between the well and barrier layers. In order to prevent such a problem, the mode used in the present invention is to supply TMGa amount in conformity with the barrier layer growth by TMGa #2 and supply the addition amount of TMGa necessary for the well growth by TMGa # 1. This is because, unlike the conventional growth method, only the TMGa concentration required for well growth is added while maintaining a certain barrier growth condition,TMGa is discontinued to minimize the growth potential of AlN.
The growth conditions used in Well and barrier are growth temperature 1100-1350 ℃ and NH 3 0.5L-40L, TMAl concentration 10 mu mol-800 mu mol and n-AlGa w N (w is more than or equal to 0 and less than or equal to 0.6) is consistent, Well (AlGa) x N)(0<x.ltoreq.0.9) two different kinds of TMGa #1, and #2 are used. At this time, the amount of TMGa #1 used and barrier (AlGayN) (0)<y.ltoreq.0.85) are identical. (5. mu. mol. about.600. mu. mol.) to increase the Ga ratio of well, TMGa having a well composition is additionally provided by TMGa # 2. The concentration range supplied at this time is 0.001. mu. mol to 10. mu. mol. The thickness distribution of Well is
Figure BDA0003575056850000101
In between, the thickness of Barrier is distributed
Figure BDA0003575056850000102
The thickness of the pair of Well and barrier added together is larger than
Figure BDA0003575056850000103
The sum of the total thicknesses of the grown MQW (active layer) is
Figure BDA0003575056850000104
The above.
5、p-AlGa y N (y is more than or equal to 0 and less than or equal to 0.6)
p-AlGa y N (y is more than or equal to 0 and less than or equal to 0.6) and N-AlGa w The growth methods of N (w is more than or equal to 0 and less than or equal to 0.6) are the same. The growth temperature is 1100-1350 ℃, NH 3 0.5L to 40L, TMAl with a concentration of 10 mu mol to 800 mu mol, TMGa with a concentration of 5 mu mol to 400 mu mol. But and n-AlGa w N (0. ltoreq. w. ltoreq.0.6) SiH for N-type semiconductor element 4 And Si 2 H 6 In contrast, p-AlGa y N (0. ltoreq. y. ltoreq.0.6) is Cp for p-type semiconductor 2 And Mg. Cp used at this time 2 The Mg concentration is 0.05 to 500. mu. mol. In addition p-AlGa y N (y is more than or equal to 0 and less than or equal to 0.6) and N-AlGa w N (w is more than or equal to 0 and less than or equal to 0.6)The composition is that y is less than or equal to w. With a thickness of
Figure BDA0003575056850000105
In the meantime.
6. Etch stop layer growth
AlN was used for the etch stop layer. Growth conditions and p-AlGa y N (y is more than or equal to 0 and less than or equal to 0.6) at 1100-1350 deg.c and NH3 at 0.5-40L, and TMAl at 10-800 mol concentration.
The detailed growth method of the etching stop layer is as follows: P-AlGa y After the N (y is more than or equal to 0 and less than or equal to 0.6) layer grows to the target temperature, the N layer is not supplied to the p-AlGaN y The TMGa source used in the N (y is more than or equal to 0 and less than or equal to 0.6) layer. The time for the TMGa already existing in the TMGa tube and the reaction furnace to completely disappear requires about 1 to 3sec even if the TMGa is not supplied. (the time required varies depending on the length of the TMGa tube and the size of the reactor) during this period p-AlGa y The Ga (y is more than or equal to 0 and less than or equal to 0.6) of the N layer is gathered to be 0. Increase in time of only 1sec will be in p-AlGa y A very thin AlN layer on the N (y is more than or equal to 0 and less than or equal to 0.6). With a thickness of
Figure BDA0003575056850000111
Figure BDA0003575056850000112
Mg doping is very difficult to perform in order to produce p-type semiconductor elements on AlN. Thus according to p-AlGa y The tunneling effect of band gap bonding between N (0. ltoreq. y. ltoreq.0.6) and the pGaN layer above the etch stop layer, so the AlN thickness cannot be too thick. If the AlN thickness exceeds
Figure BDA0003575056850000113
Since the hole supplied on p-GaN cannot overcome the band gap of AlN, a higher operating voltage is required, and eventually it cannot function as an LED element.
The etch stop layer means that each substance generates an etch rate difference according to the nature of the substance and the etching manner. Such a difference in etching rate is caused by the difference in etching rate occurring between different substances when etching a specific substance. By utilizing such characteristics, a substance to be etched and a substance having a difference in etching rate are interposed (etching stopper layer) to prevent etching from proceeding.
As shown in table 1 and fig. 4, the GaN and AlN layers have a large difference in etching rate according to the etching method (wet method/Dry method).
TABLE 1 GaN/AlN etch rate difference using wet method (NaOH/KOH)
Figure BDA0003575056850000114
As shown in table 1 and fig. 4, the difference in etching rates between GaN and AlN was 2.5 to 4 times. The final layer of the present invention, p-GaN, has a thickness of
Figure BDA0003575056850000115
If the etch stop layer is not present, then there is p-AlGa y N (0 is more than or equal to y is less than or equal to 0.6)/p-GaN layer exists. With such a layer distribution, even if etching is performed only for selectively etching the p-GaN layer, the p-AlGa layer is not uniform in thickness in the epiproxy wafer, and the like y N (0 + -y + -0.6) also poses a risk of etching. But in p-AlGa y The N (0. ltoreq. y. ltoreq.0.6) layer can be etched only at all times because of the existence of the GaN component. In contrast, if an etch stop layer is present,
even if pAlGa is completely etched y N (0. ltoreq. y. ltoreq.0.6)/etching stopper layer (AlN)/pGaN, and GaN prevents additional etching of the AlN layer, which has a relatively slow etching rate due to the non-uniform thickness of pGaN.
The etching method used at this time may be the Wet method or Dry method.
Wet method: the temperature of KOH/NaOH (40-50 mol%/60-60 mol%) solution is 300-450 deg.C, and the etching time depends on the thickness of pGaN, but is 10 seconds to 10 minutes.
The Dry method comprises the following steps: plasma Thermal ICP is used, Rf Power is 12-15 MHz, Power is 300-600W, and used gas is 10Cl 2 Ar, reaction chamber pressure 2 mTorr. Although the etching time depends on the thickness, it is within 5 seconds to 5 minutesAnd (4) carrying out the steps.
7. Growth of p-GaN
The growth condition of the p-GaN layer is 850-1100 ℃, NH 3 0.5L to 40L, a TMGa concentration of 5 mu mol to 400 mu mol, Cp 2 The concentration of Mg is between 0.1 mu mol and 1000 mu mol, and the thickness of Mg is between
Figure BDA0003575056850000121
Are distributed among them. Because the ESL etching stop layer selectively etches the p-GaN layer, the p-GaN layer is divided into two parts, and the thickness of one part of the p-GaN layer is equal to that of the other part
Figure BDA0003575056850000122
While the other part of the p-GaN layer has a thickness less than that of the p-GaN layer
Figure BDA0003575056850000123
The ratio of the two is within about 6.7%.
Comparative example 1
A general epitaxial structure of the UVC LED chip is schematically shown in fig. 5. The UVC LED chip is the same as a traditional blue LED chip, and GaN doped with Mg is used as a P-electrode layer. When the pGaN layer is used as the p-electrode layer, since the threshold voltage is lower than that of AlGaN, there is an advantage that the driving voltage of the LED can be reduced. However, the p-type GaN layer used as the p-electrode layer has a GaN absorption spectrum (GaN absorption spectrum), and absorbs 275nm light as shown in fig. 6, and a process of absorbing 275nm light in a main emission wavelength region of the UVC LED is a main cause of lowering the light efficiency of the UVC LED.
Comparative example 2
Fig. 7 is a schematic view of an epitaxial structure of a UVC LED chip for improving optical power in the prior art. The UVC LED chip replaces a p-electrode layer with an AlGaN layer which is not a GaN layer. However, the p-type AlGaN layer used in UVC has a high AI content due to the use of an Electron blocking layer (Electron blocking layer), and it is difficult to mix Mg. But in order to manufacture a UVC LED with high light efficiency, a p-AlGaN layer other than the conventional p-GaN layer should be used. Therefore, there are many differences in the kinds of metals used as the electrode layers and the fabrication process, and thus the light efficiency of the UVC LED fabricated in this way is relatively improved, but additional problems including the driving voltage are caused. As shown in fig. 8a and 8b, the driving voltage of pGaN structure and pAlGaN structure is increased, which results in low reliability of the manufactured UVC LED.
Compared with comparative examples 1 and 2, the applicant obtains the UVC-LED chip of example 1 through optimizing the epitaxial structure and the process, improves the output light power of the UVC-LED chip at 265nm from 799.76 to 1417.10 and improves the photoelectric conversion efficiency from 2.5% to 5.7% on the premise of not changing the input voltage of 5.5V and the IF current of 350 mA.
As described above, the UVC LED of the present applicant is not a conventional lateral type LED, but is fabricated as a flip-chip type LED. As shown in fig. 9, the general LED characteristics are different from those of the mercury lamp, and the light emitting direction and the heat generating direction are opposite. The lareal type LED is generally a conventional type, and when a GaAs substrate emitting Red light is used, heat is easily conducted due to high thermal conductivity, but after blue LED is developed, heat generated cannot be easily removed due to the use of sapphire having low thermal conductivity as a substrate. To solve this problem, the problem can be solved by a flip-chip type in which electrodes are mounted on the bottom. However, when a flip chip type UVC LED is manufactured, the p-GaN layer lowers the light transmittance due to the action of the light absorption layer. To solve this problem, only the pGaN layer may be selectively etched by interposing an etch stop layer using an etch rate difference between the p-AlGaN layer and the p-GaN layer, as shown in fig. 1. As shown in fig. 10, the P-GaN layer is selectively left, and the other P-electrode layer is entirely covered, thereby solving the ohmic contact problem of the P-electrode layer, thereby reducing the driving voltage, and improving the reflectivity through the P-metal when manufacturing the flip chip.
The above is not relevant and is applicable to the prior art.
While certain specific embodiments of the present invention have been described in detail by way of illustration, it will be understood by those skilled in the art that the foregoing is illustrative only and is not limiting of the scope of the invention, as various modifications or additions may be made to the specific embodiments described and substituted in a similar manner by those skilled in the art without departing from the scope of the invention as defined in the appending claims. It should be understood by those skilled in the art that any modifications, equivalents, improvements and the like made to the above embodiments in accordance with the technical spirit of the present invention are included in the scope of the present invention.

Claims (10)

1. A UVC-LED chip comprises a substrate, an epitaxial layer, an N electrode layer and a P electrode layer, wherein the epitaxial layer, the N electrode layer and the P electrode layer are arranged on the substrate, the epitaxial layer comprises an AlN layer, an AlGaN layer, an N-AlGaN layer, an MQW light-emitting layer, a P-AlGaN layer and a P-GAN layer which are sequentially arranged from bottom to top, and the UVC-LED chip is characterized in that an ESL etching stop layer is inserted between the P-AlGaN layer and the P-GaN layer and selectively etches the P-GaN layer to divide the P-GaN layer into two parts, wherein the thickness of one part of the P-GaN layer is not less than that of the P-GaN layer
Figure FDA0003575056840000011
The other part of the p-GaN layer has a thickness less than that of the
Figure FDA0003575056840000012
The P-GaN layer is completely covered with the P electrode layer, and the N electrode layer is arranged on the N-AlGaN layer.
2. A UVC LED chip according to claim 1, wherein: the AlGaN layer has the composition of AlGaN v N，0≤v<0.5; the thickness is 1-3 μm.
3. A UVC LED chip according to claim 2, wherein: the composition of the n-AlGaN layer is n-AlGaN w N, w is more than or equal to 0 and less than or equal to 0.6; the sum of the thicknesses of the n-AlGaN layer and the AlGaN layer is greater than 5 μm.
4. The UVC LED chip of claim 3, wherein the MQW light emitting layer is of AlGaN x N and AlGa y N, wherein 0<x≤0.9，0<y≤0.85，x+w>y，x>y≥w。
5. The UVC LED chip of claim 4, wherein the composition of said p-AlGaN layer is p-AlGaN z N, z is more than or equal to 0 and less than or equal to 0.6; having a thickness of
Figure FDA0003575056840000013
6. The UVC LED chip of claim 5, wherein said ESL etch stop layer is AlN and has a thickness of
Figure FDA0003575056840000014
7. The UVC LED chip of claim 6, wherein the p-GAN layer has a thickness of
Figure FDA0003575056840000015
8. A method of manufacturing a UVC LED chip as claimed in any one of claims 1 to 7, wherein: the manufacturing method specifically comprises the following steps:
s1, providing a sapphire substrate, and growing an AlN layer, an AlGaN layer, an n-AlGaN layer, an MQW light-emitting layer, a p-AlGaN layer, an ESL etching stop layer and a p-GAN layer on the substrate in sequence from bottom to top by adopting an MOCVD system to obtain an epitaxial layer;
s2, carrying out patterned etching on the epitaxial layer obtained in the step S1, exposing the N-type AlGaN structure of part of the N-type AlGaN layer, and preparing an N electrode layer on the N-type AlGaN structure;
and S3, preparing a P electrode on the P-GAN layer of the epitaxial layer obtained in the step S1, and obtaining the UVC-LED chip with the inverted vertical structure.
9. The method of claim 8, wherein the AlN growth conditions for the ESL etch stop layer include a temperature of 1100 ℃ to 1350 ℃, ammonia gas of 0.5L to 40L, and a concentration of trimethylaluminum of 10 μmol to 800 μmol; the growth conditions of the p-GaN layer comprise the temperature of 850-1100 ℃, 0.5-40L of ammonia gas, the concentration of trimethyl gallium of 5-400 mu mol and the concentration of magnesium cyclopentadienyl of 0.1-1000 mu mol.
10. The method according to claim 8, wherein the growth conditions of the n-AlGaN layer include a temperature of 1100 to 1350 ℃, 0.5L to 40L of ammonia gas, a concentration of trimethylaluminum of 10 μmol to 800 μmol, a concentration of trimethylgallium of 5 μmol to 400 μmol, and a concentration of silane of 1x 10 -6 ～1×10 1 μmol。
CN202210330341.XA 2022-03-31 2022-03-31 UVC-LED chip and manufacturing method thereof Pending CN114937724A (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108352427A (en) * 2015-08-24 2018-07-31 Lg伊诺特有限公司 Light-emitting component
CN211182232U (en) * 2019-09-11 2020-08-04 北京中科优唯科技有限公司 Inverted ultraviolet light-emitting diode chip
CN111755330A (en) * 2019-03-26 2020-10-09 苏州晶湛半导体有限公司 Semiconductor structure and manufacturing method thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108352427A (en) * 2015-08-24 2018-07-31 Lg伊诺特有限公司 Light-emitting component
CN111755330A (en) * 2019-03-26 2020-10-09 苏州晶湛半导体有限公司 Semiconductor structure and manufacturing method thereof
CN211182232U (en) * 2019-09-11 2020-08-04 北京中科优唯科技有限公司 Inverted ultraviolet light-emitting diode chip

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