CN204577429U - A GaN-based composite substrate for array pattern transfer - Google Patents

Abstract

The utility model relates to a GaN base composite substrate that arrayed pattern shifted, including heat conduction electric conduction transfer substrate, be located the heat conduction electric bonding dielectric layer on this substrate and go up the GaN base epitaxial film that arrayed distributes. The GaN-based epitaxial film is formed by etching an arrayed small-size film by laser, and transferring the arrayed GaN-based epitaxial film to a transfer substrate through a medium bonding and substrate stripping process. The utility model discloses compound substrate, the advantage that is applicable to gaN homoepitaxy and can directly prepare vertical structure LED device that had both taken into account the compound substrate that the substrate technique realized in the past, simplified technology, reduce cost can effectively reduce the stress in the substrate transfer process again, reduce substrate warpage, fold and microcrack production, and can solve because of the gaN film damage that the chip cutting caused, dielectric layer material splash and device short circuit problem to improve the performance of gaN base compound substrate and the chip of preparing.

Description

A GaN-based composite substrate for array pattern transfer

technical field

The utility model relates to the technical field of semiconductor optoelectronic devices, in particular to a GaN-based composite substrate with arrayed pattern transfer and low stress state.

Background technique

Wide bandgap GaN-based semiconductor materials have excellent optoelectronic properties and have been widely used in the production of light-emitting diodes, lasers, ultraviolet detectors and high-temperature, high-frequency, high-power electronic devices, and can be applied to the preparation of high-end microelectronics required by aerospace Devices, such as high-mobility transistors (HEMTs) and heterojunction transistors (HFETs), have become research hotspots in the international optoelectronics field.

Since the preparation of GaN bulk single crystal is very difficult, large-scale single crystal GaN is difficult to obtain directly, and the price is expensive, the epitaxial growth of GaN material system is mainly based on the large mismatch heteroepitaxy technology. At present, it is commonly used in the industry to epitaxial GaN materials by two-step growth method on sapphire substrates with good stability and relatively low price. This buffer layer-based heterogeneous epitaxy technology has achieved great success. Among them, blue and green LEDs It has been commercialized, but the sapphire-based GaN composite substrate has shown great limitations. The problems are mainly reflected in: (1) sapphire is an insulating material, so that related devices cannot achieve a vertical structure, and only the same-side stepped electrode structure can be used. , the current is injected laterally, causing the current flowing through the active layer to be uneven, resulting in the current crowding effect, reducing the material utilization rate, and increasing the photolithography and etching process in the device preparation, which significantly increases the cost; (2) sapphire The thermal conductivity of GaN is not good, and the thermal conductivity is about 0.25W/cmK at 1000°C. The problem of heat dissipation is prominent, which affects the electrical, optical characteristics and long-term working reliability of GaN-based devices, and limits its use in high temperature and high-power devices. (3) Sapphire has high hardness, and there is a 30° angle between the sapphire lattice and the GaN lattice, so it is not easy to cleavage, and the cavity surface of GaN-based devices cannot be obtained by cleavage.

Silicon substrate has the advantages of excellent thermal and electrical conductivity, low cost, easy to realize large size and integration, and has become one of the important research topics in the field of GaN-based LEDs in recent years. However, the lattice mismatch and thermal mismatch between silicon and GaN At present, the technology for growing GaN epitaxial layers on silicon substrates is not yet mature, and the dislocation density in the composite substrate is high, and even cracks and cracks appear. Silicon carbide is an ideal substrate for epitaxial GaN. The lattice mismatch and thermal mismatch between it and GaN are small, and it has good thermal and electrical conductivity, which can greatly simplify the manufacturing process, but the silicon carbide substrate is expensive. Moreover, there are problems such as adhesion between the epitaxial layer and the substrate, so it is not suitable for industrial production.

With the deepening of research, people are increasingly aware that homoepitaxial is the best choice to obtain high-performance GaN substrates. In view of the high price of GaN single crystal substrates, some research institutions have begun to pay attention to the combination of dielectric bonding and laser lift-off technology, transferring GaN epitaxial single crystal layers to substrates with high thermal conductivity and high electrical conductivity to eliminate sapphire adverse effects on the substrate. However, changes in the substrate transfer process and the thermally and electrically conductive substrate will generate a large stress in the transferred substrate, resulting in a certain warpage of the composite substrate, and even the formation of wrinkles and cracks on the GaN epitaxial film, making it difficult to achieve high-performance GaN monolayers. Epitaxy and chip preparation; in addition, the subsequent chip cutting process will cause problems such as dielectric layer material splashing, GaN-based thin film damage, and device short circuit.

Contents of the invention

The utility model provides a GaN-based composite substrate for array pattern transfer as shown in FIG. On the above, the GaN-based epitaxial film 3 that is transferred from the arrayed pattern after marking the arrayed pattern with a laser and then through dielectric bonding and peeling off; the utility model uses dielectric bonding technology and laser lift-off technology to realize the GaN-based epitaxial film. The transfer of the arrayed pattern is to transfer the GaN-based epitaxial thin film drawn into the arrayed pattern from the sapphire substrate to the thermal and conductive transfer substrate to realize the transfer of the arrayed pattern. Due to the above structural features and the use of laser to scribe the arrayed pattern first, the transfer of the arrayed patterned GaN-based epitaxial film is realized through dielectric bonding and laser lift-off technology, which not only simplifies the process, reduces the cost, but also effectively reduces the substrate transfer process. The stress in the medium can reduce substrate warping, wrinkles and microcracks, and can solve the problems of GaN-based film damage, dielectric layer material sputtering and device short circuit that often occur in subsequent chip dicing, thereby improving the performance of GaN-based composite substrates and prepared GaN-based composite substrates. chip performance.

As shown in Figure 1, a GaN-based composite substrate for array pattern transfer proposed by the utility model includes (from bottom to top) a thermally and electrically conductive transfer substrate 1, a thermally and electrically conductive bonding medium layer located thereon 2. GaN-based epitaxial thin film 3 on the bonding medium layer with arrayed pattern transfer.

The thickness of the GaN-based epitaxial thin film 3 transferred by the array pattern is 1 micron to 100 microns, preferably 3 microns to 50 microns; the thickness of the thermally and electrically conductive bonding medium layer 2 is 10 nanometers to 100 microns, preferably 500 microns. nanometer to 20 micrometers; the thickness of the thermally conductive substrate 1 is 10 micrometers to 3000 micrometers, preferably 50 micrometers to 1000 micrometers.

Both the bonding medium layer 2 and the thermally and electrically conductive substrate 1 are required to have the following characteristics: (1) high temperature resistance, melting point over 1000°C, and no violent diffusion; (2) thermal and electrical conductivity.

The thermally and electrically conductive bonding medium layer 2, whose material has a melting point higher than 1000°C and has thermal and electrical conductivity, can be selected from molybdenum (Mo), titanium (Ti), palladium (Pd), gold (Au), copper (Cu) , tungsten (W), nickel (Ni), chromium (Cr), a single metal or an alloy of several, or a resin matrix and conductive particles silver (Ag), gold (Au), copper (Cu), aluminum Conductive polymers composed of one or more of (Al), zinc (Zn), iron (Fe), nickel (Ni), and graphite (C), or particles of one or more of the above conductive particles and Conductive paste composed of binders, solvents, additives, or silicate-based high-temperature conductive adhesive (HSQ), or nickel (Ni), chromium (Cr), silicon (Si), boron (B), etc. A high-temperature alloy slurry formed of metal; the thermally and electrically conductive bonding medium layer 2 can be a single-layer or multi-layer structure, and can be prepared on the thermally and electrically conductive substrate 1 by using magnetron sputtering or vacuum thermal evaporation or a wet process .

The thermally and electrically conductive transfer substrate 1, whose material has a melting point higher than 1000°C and has thermal and electrical conductivity, can be selected from molybdenum (Mo), titanium (Ti), palladium (Pd), copper (Cu), tungsten (W), A single metal or an alloy of nickel (Ni), chromium (Cr), or a silicon (Si) crystal, silicon carbide (SiC) crystal or AlSi crystal.

The GaN-based epitaxial film 3 for arrayed pattern transfer can be GaN film, AlN film, InN film, or an alloy film of two or three of them; the GaN-based epitaxial film for arrayed pattern transfer is carried out Before the dielectric bonding and substrate lift-off processes, lasers are used to scribe small-sized arrayed patterns.

Between the thermally and electrically conductive transfer substrate 1 and the GaN-based epitaxial film before arrayed pattern transfer, through the diffusion of the bonding medium layer 2, the gap between the GaN-based epitaxial film and the thermally and electrically conductive transfer substrate 1 before the arrayed pattern is transferred On the front side, tight bonding is performed; the diffusion bonding conditions are: temperature ≥ 0°C, pressure 100 kgf/square inch to 4 tons/square inch.

Compared with the GaN-based composite substrate realized by relatively traditional substrate transfer technology, the utility model has many unique advantages:

1) The GaN-based epitaxial film is first scribed by laser and then transferred into an array pattern, which can effectively reduce the stress during the substrate transfer process, reduce the occurrence of defects such as substrate warpage, wrinkles and microcracks, and obtain residual stress Smaller high-performance GaN-based composite substrates are conducive to subsequent GaN homoepitaxial and chip preparation;

2) In the later chip cutting, there is no need to cut the GaN-based thin film, so the damage to the GaN-based epitaxial thin film is reduced;

3) Arrayed pattern transfer makes the patterning process of GaN-based composite substrates simple, and the source of bonding dielectric materials is extensive, which can effectively reduce costs and facilitate industrialization;

4) By adjusting the laser energy and laser spot size in the laser scribing process, the size of each region and the channel width between adjacent regions in the arrayed pattern-transferred GaN-based composite substrate are controlled.

Description of drawings

FIG. 1 is a schematic diagram of a vertical cross-sectional structure of an arrayed pattern transfer GaN-based composite substrate of the present invention.

Fig. 2 is a schematic diagram of the preparation process of a GaN-based composite substrate that uses a laser to perform square scribing on a GaN-based epitaxial film, and uses a Ni/Pd/Ni bonding dielectric layer to realize arrayed pattern transfer in Example 1. Among them, (a) is a schematic diagram of using a laser to scribe a GaN-based epitaxial film to form an array of small-sized GaN-based epitaxial films; (b) and (c) use a Ni/Pd/Ni bonding dielectric layer 21 to form an array Schematic flow chart of bonding GaN-based epitaxial thin film 31 and Mo substrate 11 before pattern transfer; (d) is the GaN-based composite substrate formed by array pattern transfer after removing sapphire substrate 4 by laser lift-off process Schematic diagram of the vertical section structure.

Fig. 3 is the front top view of the GaN-based composite substrate of embodiment 2. Using a laser to scribe a square of the GaN-based epitaxial film, using conductive Ag glue to bond the dielectric layer 22 and using laser lift-off technology to realize arrayed pattern transfer and a schematic diagram of the vertical section.

The meaning of the number marks in the attached drawings: 1: transfer substrate 11: Mo substrate 12: Si substrate 2: bonding dielectric layer 21: Ni/Pd/Ni bonding dielectric layer 22: conductive Ag glue bonding dielectric layer 3 : GaN-based epitaxial film for array pattern transfer 31: (laser scribed) GaN-based epitaxial film before array pattern transfer 4: Sapphire substrate.

Detailed ways

A GaN-based composite substrate transferred in an array is described in detail below with reference to the accompanying drawings of the utility model. First of all, it should be explained that those skilled in the art can make various modifications or improvements according to the basic idea of the utility model, as long as they do not deviate from the basic idea of the utility model, all are within the scope of the utility model.

Embodiment 1: Use a laser to scribe the GaN-based epitaxial film on the sapphire substrate 4 to form an arrayed [square] GaN-based epitaxial film 31 before pattern transfer, and use Ni/Pd/Ni to bond the dielectric layer 21 to form an arrayed [square] pattern. [Square] The GaN-based epitaxial film 31 before pattern transfer is tightly bonded to the front of the Mo substrate 11; the laser lift-off technique is used to remove the sapphire substrate 4 and at the same time the arrayed [square] GaN-based epitaxial film 31 before pattern transfer is formed from the sapphire The substrate 4 is transferred to the Mo substrate 11 to realize the GaN-based epitaxial thin film 3 transferred with an arrayed [square] pattern, and finally obtain a GaN-based composite substrate with an arrayed [square] pattern; the specific process is as follows:

(1) Epitaxial growth of a GaN single crystal layer on the sapphire substrate 4: on a 2-inch 430-micron-thick flat sapphire substrate, first use MOCVD technology to epitaxially grow a 4-micron-thick GaN single-crystal layer, and then grow the GaN single crystal layer in HVPE. Thick GaN layer thickness up to 15 microns;

(2) Using a laser with an energy of 150 micro-joules and a square spot with a side length of 10 microns to scribe the GaN-based epitaxial film, on which an arrayed [square] pattern GaN-based epitaxial film 31 with a side length of 5 mm is formed, such as As shown in Figure 2(a);

(3) on the Mo substrate 11 surface of 150 micrometers, use the Ni of 100 nanometers, the Pd of 1 micrometer and the Ni of 100 nanometers to be deposited successively by magnetron sputtering, as Ni/Pd/Ni bonding dielectric layer 21; 600°C, 10Torr pressure, bonded for 3 hours to realize the tight bonding of the GaN epitaxial layer 31 and the Mo substrate 11 before the arrayed [square] pattern transfer, as shown in Figure 2 (b) and (c);

(4) Using laser lift-off technology to remove the sapphire substrate 4, transfer the GaN-based epitaxial film 31 before the arrayed [square] pattern transfer from the sapphire substrate 4 to the Mo substrate 11 to obtain an arrayed [square] Pattern-transferred GaN-based epitaxial film 3; the surface of the obtained composite substrate is cleaned with hydrochloric acid, acetone, etc., and an arrayed [square] pattern-transferred GaN/Ni/Pd/Ni/Mo composite substrate is obtained. As shown in Figure 2(d).

(5) The resulting composite substrate comprises a Mo substrate 11 with a thickness of 150 microns, a Ni/Pd/Ni bonding medium layer 21 with an adjustable thickness, and a GaN single crystal epitaxial layer with a thickness of 15 microns. Closely bonded together, and finally get arrayed [square] pattern transferred GaN-based composite substrate.

Embodiment 2: Use a laser to scribe the GaN-based epitaxial film on the sapphire substrate to form an arrayed [square] pattern before transferring the GaN-based epitaxial film, use conductive Ag glue to bond the dielectric layer 22, and form the arrayed [square] pattern Before the transfer, the GaN-based epitaxial film is closely bonded to the front side of the Si substrate 12; then, while the sapphire substrate is removed by laser lift-off technology, the GaN-based epitaxial film before the arrayed [square] pattern transfer is transferred from the sapphire substrate to The conductive Ag glue on the Si substrate 12 is bonded to the dielectric layer 22 to realize the GaN-based epitaxial thin film with arrayed [square] pattern transfer, and finally obtain the GaN-based composite substrate with arrayed [square] pattern; the specific process is as follows:

(1) Epitaxial growth of a GaN single crystal layer on the sapphire substrate 4: on a 2-inch 430-micron-thick flat sapphire substrate, first use MOCVD technology to epitaxially grow a 4-micron-thick GaN single-crystal layer, and then grow the GaN single crystal layer in HVPE. Thick GaN layer thickness up to 15 microns;

(2) Use a laser with an energy of 150 microjoules and a square spot with a side length of 10 microns to scribe the GaN-based epitaxial film, and form an arrayed [square] GaN-based epitaxial film with a side length of 10 mm on it before pattern transfer;

(3) On the surface of the Si substrate 12 with a thickness of 300 microns, use a spin-coating process to prepare a conductive Ag glue bonding medium layer 22, and then perform bonding at a temperature of 1000° C. and a pressure of 2 Torr for 30 minutes to realize an array [square] pattern Close bonding of GaN-based epitaxial layer and Si substrate 12 before transfer;

(4) Using laser lift-off technology to remove the sapphire substrate, transfer the GaN-based epitaxial film before the arrayed [square] pattern transfer from the sapphire substrate to the conductive Ag glue bonding medium layer 22 on the Si substrate 12 , to obtain a GaN-based epitaxial layer with an arrayed [square] pattern transfer; the surface of the obtained composite substrate is cleaned with hydrochloric acid, acetone, etc., and an arrayed [square] pattern transferred GaN/conductive Ag glue/Si Composite substrate, as shown in Figure 3(b).

(5) The resulting composite substrate comprises a 300 micron thick Si substrate 12, an adjustable conductive Ag glue bonding medium layer 22, a 15 micron thick GaN single crystal epitaxial layer, and the three are closely bonded. Taken together, an arrayed [square] pattern-transferred GaN-based composite substrate is finally obtained, as shown in Figure 3(a) and (b).

Claims (3)

1. a GaN-based composite substrate for array pattern transfer, is characterized in that it comprises a thermally conductive transfer substrate (1), a thermally conductive bonding medium layer (2) positioned thereon, a bonding medium layer ( 2) GaN-based epitaxial thin film (3) transferred on an arrayed pattern. 2. The GaN-based composite substrate for arrayed pattern transfer according to claim 1, characterized in that, the thermally and electrically conductive transfer substrate (1) and the bonding medium layer (2) have a melting point higher than 1000 ℃ and has thermal and electrical conductivity. 3. A GaN-based composite substrate for arrayed pattern transfer according to claim 1, characterized in that, the thickness of the GaN-based epitaxial film (3) for arrayed pattern transfer is 1 micron to 100 microns, preferably 3 microns to 50 microns; the thickness of the thermally conductive bonding medium layer (2) is 10 nanometers to 100 microns, preferably 0.5 microns to 20 microns; the thickness of the thermally conductive transfer substrate (1) is 10 microns to 3000 microns, preferably 50 microns to 1000 microns.