TWI795968B - The substrate tray and its MOCVD reactor - Google Patents

Abstract

The invention provides a substrate tray for supporting substrates to be processed and an MOCVD reactor therein, which are used for inverting substrates for film growth. The substrate tray includes a side wall and a central opening surrounded by the side wall, the inner side of the side wall includes a first step for placing a heat diffusion plate, and the bottom of the first step includes a second step. A heat insulating device is provided on the upper surface of the second stepped part, and the heat insulating device is used to support the first surface of the substrate to be processed, and the diameter of the inner side wall of the first stepped part is larger than the diameter of the inner side wall of the second stepped part.

Description

Substrate tray and its MOCVD reactor

The invention relates to the field of semiconductors, in particular to the technical field of a substrate tray for compound semiconductor epitaxial material growth and an MOCVD reactor thereof.

The demand for compound semiconductor epitaxial materials is more and more extensive, and typical materials such as gallium nitride can be used in the manufacture of LEDs and power components. Commonly used compound semiconductor material reactors include metal-organic chemical vapor reactors (MOCVD). MOCVD reactors include a reaction chamber with a rotating substrate tray at the bottom of the reaction chamber, and a heater below the substrate tray for heating the substrate tray. , the substrate to be processed is set on the substrate tray, and the upper part of the reactor includes an air inlet device, and the reaction gas flowing in from the inlet device flows to the substrate arranged on the upper surface of the tray, and grows on the upper surface of the substrate to produce the required epitaxial material layer. With the development of industry demand, micro/mini LED has higher and higher requirements for the uniformity of the epitaxial layer above the substrate, and at the same time, the requirement for the upper limit of the number of particles is also higher and higher. The air intake device above the substrate in the existing MOCVD reactor will generate a large amount of particles during the reaction process, and these particles will move with the airflow or be attracted by gravity and fall to the upper surface of the substrate, resulting in damage to the micro-sized LED chip structure.

In order to prevent particles from falling onto the substrate, the industry needs a new substrate tray structure that reduces particles when the substrate undergoes epitaxial growth. At the same time, the temperature on the substrate has extremely high uniformity, and optimally, it needs to be easy to load and unload. Substrate to realize automatic operation in vacuum environment to avoid the introduction of particles.

In order to solve the above technical problems, the present invention provides a substrate tray for supporting substrates, the substrate tray includes a side wall and a central opening surrounded by the side wall, and the inner side of the side wall includes a first step for placing a thermal diffusion plate, a second stepped portion is included under the first stepped portion, and a heat insulating device is provided on the upper surface of the second stepped portion, and the heat insulating device is used to support the first surface of the substrate to be processed, so The diameter of the inner wall of the first stepped portion is greater than the diameter of the inner wall of the second stepped portion.

Preferably, the heat insulation device includes a heat insulation ring, the bottom surface of the heat insulation ring is placed on the second step part, and the top of the second step part includes a support surface for supporting the The substrate further includes a vertical sidewall surrounding the support surface.

Preferably, the heat insulating device includes a heat insulating ring, the top of the heat insulating ring includes a plurality of upwardly protruding ribs, and the substrate is placed on the plurality of upwardly protruding ribs.

Preferably, the bottom surface of the heat insulating ring includes a plurality of downwardly protruding ribs, and the heat insulating ring is in contact with the second step portion through the plurality of ribs.

Preferably, the heat insulating device includes a plurality of supporting claws arranged separately along the circumferential direction, the supporting claws are arranged on the second step portion, and at least part of the top is used to support the substrate.

Preferably, the supporting claw includes a horizontal extension part and a vertical extension part, wherein the bottom plane of the horizontal extension part is placed on the second step part, and the top cross section of the horizontal extension part is smaller than the bottom plane.

Preferably, the vertical extension is located outside the horizontal extension, and the cross-section of the vertical extension near the central opening of the substrate tray is tapered to minimize the contact area between the side wall of the substrate and the vertical extension.

Preferably, the supporting claw includes a tray connection part, a lower extension part and a substrate support part, the bottom surface of the tray connection part is supported by the top surface of the second step part, and one end of the lower extension part is connected to The other end of the tray connection portion extends downward and is connected to the substrate support portion, The top of the substrate supporting part is used to support the substrate to be processed, so that the first surface of the substrate is lower than the top surface of the second step part.

Preferably, the substrate supporting part extends along the horizontal direction, wherein the cross-section of the top is smaller than the cross-section of the bottom of the substrate supporting part.

Preferably, the end of the lower extension near the central opening of the substrate tray has a tapered cross-section, so that the contact area between the side wall of the substrate and the vertical extension is minimized.

Preferably, the thermal insulation device is made of a material with a first thermal conductivity, and the substrate tray is made of a material with a second thermal conductivity, wherein the first thermal conductivity is less than 1/4 of the second thermal conductivity .

Preferably, the thermal conductivity of the heat insulating device is less than or equal to 40W/m.k, and the thermal conductivity of the substrate tray is greater than or equal to 150W/m.k.

Further, the present invention also provides a reactor, which includes a reaction chamber, and the substrate tray as described above is arranged in the reaction chamber.

The advantage of the present invention is that: the present invention provides a substrate tray of an inverted MOCVD reactor and the reactor therein, wherein the substrate tray includes a first step portion for placing a thermal diffusion plate, and also includes a second step portion, wherein A support ring made of heat insulating material is placed on the second step to reduce lateral heat transfer between the edge region of the substrate and the substrate tray through conduction. Wherein the diameter of the inner wall of the first stepped portion is greater than the diameter of the inner wall of the second stepped portion. The thermal insulation material can be made of ceramic materials such as alumina, quartz, and sapphire. The thermal conductivity of alumina, quartz, and sapphire materials is only 4, 20, and 40W/m.k. The thermal conductivity of traditional substrate tray materials such as graphite and silicon carbide materials The coefficient can reach 150-490W/m.k. By using the above heat insulating material, the heat conduction between the edge of the substrate and the substrate tray can be greatly reduced, thereby improving the temperature uniformity from the center to the edge of the substrate, and improving the uniformity of the growth quality of the epitaxial material on the substrate.

1: Top cavity

10, W: Substrate

11: Clearance

12: Controller

3: Air intake device

4: exhaust device

7: Drive disk

8: Substrate tray

80: Bottom surface of substrate tray

81: The first step

81S, 82’S: Medial wall

82,82’,82”,82''': the second step

84,85: support ring

851: raised edge

851a, 86a: vertical extension

851b, 86b: horizontal extension

852: Slender edge

86,87: Support claw

86a1, 86b1, 87b1, 87c1: Ridges

87a: Tray connection part

87b: lower extension

87c: Substrate support part

9: Thermal diffusion plate

H1, H2: Heater

S1, S2: Probe

Fig. 1 is the structural representation of a kind of upside-down MOCVD reactor of the present invention; Fig. 2 is the substrate tray schematic diagram that is used for upside-down MOCVD reactor of the present invention; Fig. 3 a is the substrate that is used for upside-down MOCVD reactor of the present invention Schematic diagram of the second embodiment of the tray; Fig. 3b and Fig. 3c are schematic views of the structure of the carrier ring in the third embodiment of the substrate tray of the present invention; Fig. 4a and 4b are the fourth embodiment of the substrate tray for flip-chip MOCVD reactors of the present invention Intentional embodiment; FIG. 5a is a schematic diagram of a fifth embodiment of a substrate tray for flip-chip MOCD reactors according to the present invention;

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art of the present invention without making progressive changes shall fall within the protection scope of the present invention.

Fig. 1 is a schematic structural view of a flip-chip MOCVD reactor of the present invention. As shown in Fig. 1, the flip-chip substrate reaction chamber includes a heater in the top chamber 1, and the heater can be a plurality of independent heaters with zoned temperature control H1, H2. A substrate tray 8 is included below the heater, and the inner side of the substrate tray 8 includes an annular first step portion 81 for placing the heat diffusion plate 9, and also includes a second step portion below the first step portion 81 82, for placing the substrate to be processed, wherein the back of the substrate faces the thermal diffusion plate 9, and the edge of the surface to be processed is supported by the second step portion 82 and faces the bottom of the reaction chamber below. There is also a gap 11 between the thermal diffusion plate 9 and the back of the substrate. After the heat from the heaters H1 and H2 heats the thermal diffusion plate 9 through radiation, the thermal diffusion plate 9 radiates downward through the gap 11 to heat the lower substrate 10. back. Wherein the substrate tray 8 and the thermal diffusion plate 9 are made of high Made of thermally conductive materials, such as graphite, SiC, etc. Because there is a surface in direct contact with the second step portion 82 in the edge region of the processing surface of the substrate 10, a large amount of heat flows laterally between the second step portion 82 and the substrate 10 through the contact surface of the edge, which will cause the substrate The temperature difference between the edge area and the central area of the sheet 10 is too large, and this temperature difference cannot be compensated by controlling the power of the upper heater. In order to support and drive the substrate tray 8 to rotate, a driving disc 7 is included around the periphery of the substrate tray 8, so that the substrate tray 8 rotates during processing. The bottom of the reaction chamber may also include a plurality of probes S1 and S2 for detecting parameters such as temperature, thickness, and degree of deformation of the upper substrate. A controller 12 controls the heating power and ratio of the upper heater according to the parameters obtained by these probes S1, S2. One side below the substrate tray 8 and the drive disk 7 includes an air inlet device 3 for introducing the reaction gas into the reaction space below the substrate tray 8, and the position opposite to the inlet device 3 includes an exhaust device 4 for reacting The final gas exits the reaction chamber.

In addition, this inverted substrate tray 8 also has high substrate loading and unloading difficulties. When loading, it is necessary to first use a suction cup to absorb the substrate 10 and place it on the second step portion 82, and then absorb the heat diffusion plate 9 and place it on the second step portion 82. On the first step portion 81; when unloading, the temperature of the substrate tray 8 needs to be reduced to a certain degree, and the suction cup is stretched into the reaction chamber and the thermal diffusion plate 9 is sucked out of the reaction chamber, and then the suction cup is used to remove the substrate 10 from the substrate 10. After sucking the substrate 10 from the back, the substrate 10 is removed from the reaction chamber, and the substrate 10 is turned over after being removed from the reaction chamber, so that the processed surface of the substrate 10 is placed on the corresponding fixing frame. This process of repeatedly absorbing, moving, and flipping is very complicated and cannot be completed by low-cost robotic arms. It is often done manually, which will cause a large amount of particles to be adsorbed on the substrate 10 during the transfer process of the substrate 10, and eventually flip-chip The advantage of less particles brought by the substrate reaction chamber is greatly weakened.

Based on the technical problems disclosed above, the inventor proposes a novel substrate tray structure. As shown in FIG. 2 is a schematic diagram of a substrate tray for a flip-chip MOCVD reactor of the present invention, wherein the substrate tray 8 includes a first step 81 for placing a heat diffusion plate 9, and also includes a second step 82', Wherein, a support ring 84 made of heat insulating material is placed on the second step portion 82 ′ to reduce lateral heat transfer between the edge region of the substrate and the substrate tray 8 through conduction. in The diameter of the inner wall 81S of the first stepped portion 81 is larger than the diameter of the inner wall 82'S of the second stepped portion 82'. The thermal insulation material can be made of ceramic materials such as alumina, quartz, and sapphire. The thermal conductivity of alumina, quartz, and sapphire materials is only 4, 20, and 40W/m.k. The thermal conductivity of traditional substrate tray materials such as graphite and silicon carbide materials The coefficient can reach 150-490W/m.k. By using the above heat insulating material, the heat conduction between the substrate edge and the substrate tray can be greatly reduced, thereby improving the temperature uniformity from the center to the edge region of the substrate, and improving the uniformity of the growth quality of the epitaxial material on the substrate. The support ring 84 has an L-shaped cross-section, wherein the bottom surface cooperates with the second step 82', and the inner side of the upper surface includes a heat-insulating step, and the substrate is placed on the heat-insulating step.

In order to further reduce the heat conduction between the substrate W and the substrate tray 8, the present invention proposes a substrate tray as shown in FIG. , the support ring as a whole still has an L-shaped cross-section. As shown in Figure 3b and Figure 3c, the bottom surface of the support ring 85 includes a plurality of elongated ribs 852 protruding from the bottom surface, and the inner side of the upper surface of the support ring 85 includes a plurality of L-shaped raised ribs 851, wherein the raised ribs 851 include vertical extensions 851a and the horizontal extension 851b, the edge of the material growth surface of the substrate to be processed is supported by the horizontal extension 851b, and the sidewall of the substrate to be processed can be in contact with the inner sidewall of the vertical extension 851a. Corresponding elongated ribs 852 are also provided on the lower surface of the support ring 85. The elongated ribs 852 further reduce the actual contact area between the support ring 85 and the substrate W and between the support ring 85 and the second lower step portion 82', and also This greatly reduces the heat flux between the substrate W and the second stepped portion 82'. Wherein the inner side wall of the vertical extension 851a is not necessarily completely perpendicular to the plane of the substrate at 90 degrees, but also can be inclined downward, so that the substrate can be automatically aligned with the center of the support ring 85 when placing the substrate.

In order to simplify the structure of the substrate tray 8 of the present invention, the inventor proposes another embodiment of the substrate tray. As shown in Figure 4a, the inner wall of the inner through hole of the substrate tray 8 includes a plurality of independent supporting claws 86 evenly distributed on the annular supporting surface of the second step portion 82", so that the supporting ring is no longer required to be arranged on the substrate. and the second step portion 82". The supporting claw 86 is also made of heat-insulating ceramic material, and its specific structure is shown in Fig. 4b, including a vertical extension 86a and a horizontal extension 86b. Wherein the horizontal extension 86b has the shape of a triangular prism, wherein the bottom area is larger so that the supporting claw 86 Stably fixed on the second step portion 82", the upper end is a ridgeline 86b1, so that there is only a linear contact area between the edge area of the substrate and the supporting claw 86, which greatly reduces the conduction between the substrate and the supporting claw 86 Heat. The structure of the vertical extension part 86a is similar to that of the horizontal extension part 86b, except that its outer wall area is larger, so that the outer wall of the support claw 86 can be close to the inner wall of the substrate tray above the second step part 82", while extending vertically The innermost part of the portion 86a is a ridgeline 86a1, so that the contact between the side wall of the substrate and the supporting claw 86 only has a linear contact area, which also reduces the heat conduction in the direction of the side wall of the substrate. The cross-section of the supporting claw 86 can also be other polygons, as long as the area in contact with the substrate has a tapered cross-section, the contact surface between the substrate and the supporting claw can be minimized.

The above-mentioned support rings 84, 85 and support claws 86 can greatly reduce the heat conduction between the edge region of the substrate and the second step, but the substrate is erected above the second step and the support ring/claw for material layer The lower surface of the growing substrate is higher than the bottom surface 80 of the substrate tray 8, which will cause the reaction gas to flow through the bottom surface 80 of the substrate tray 8 in the horizontal direction, and when reaching the edge of the substrate, the gas flow will turn upward to the upper recessed area , which leads to chaotic eddy currents in the edge region of the substrate. This disorder of gas flow distribution will lead to inhomogeneity in the thickness or crystal structure of the material layer grown on the substrate, which seriously affects the growth quality of the material layer on the substrate surface. In order to further solve the problem of uneven airflow distribution on the surface of the substrate, the inventor proposed a substrate tray 8 as shown in Figure 5a. New shaped support claw 87. As shown in FIG. 5b, the supporting claw 87 includes a tray connecting portion 87a, a lower extending portion 87b and a substrate supporting portion 87c. The tray connecting portion 87a is fixed above the second step portion 82'' of the substrate tray 8, and the lower extending portion 87b extends downward for a certain distance from the inner end of the tray connecting portion 87a to connect with the outer end of the substrate supporting portion 87c. Wherein the top of the substrate supporting portion 87c includes a raised ridgeline 87c1 for supporting the substrate to be processed, and the lower extension 87b can also be designed to include a ridgeline 87b1 inside, so that the supporting claw 87 is aligned with the edge of the substrate. Heat conduction between areas is minimized. Wherein, the downward extension value of the lower extension part 87b can be optimally designed, so that the height of the ridge line 87c1 is close to the height of the bottom surface 80 of the substrate tray 8, so that it is fixed on the substrate support part 87c The substrate to be processed has substantially the same height as the bottom surface 80 of the substrate tray 8, so that there is a stable airflow distribution on the substrate during the process, and a high-quality material layer is grown.

In the embodiments shown in Fig. 4a, Fig. 4b, Fig. 5a, and Fig. 5b of the present invention, multiple supporting claws can be easily replaced with new ones or supporting claws with new shapes selected according to process requirements. After long-term use in the MOCVD reactor, the physical properties of the surface materials of the substrate tray, support ring, and support claws will gradually change. After adopting the replaceable supporting claws of the present invention, the supporting claws can be replaced conveniently without dismantling the entire substrate tray, so that the reaction chamber can be maintained in the best state for a long time. Or when it is found that the temperature in a local area is too high or too low according to the results of the processing process, the support claw at the corresponding position on the substrate tray can be selected to be replaced with a support claw with a smaller contact surface or a larger contact surface, so that the structure of the present invention The combination of the substrate tray and the preferred supporting claws can also serve as a preferred means to adjust the temperature uniformity of the substrate surface.

Although the present invention is disclosed above, the present invention is not limited thereto. Anyone with ordinary knowledge in the technical field of the present invention can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the scope of the patent application.

8: Substrate tray

80: Bottom surface of substrate tray

81: The first step

81S, 82’S: Medial wall

82': the second step

84: support ring

W: Substrate

Claims (13)

A substrate tray for supporting substrates, wherein: the substrate tray includes a side wall and a central opening surrounded by the side wall, the inner side of the side wall includes a first step portion for placing a heat diffusion plate, the first The bottom of the step part includes a second step part, and the upper surface of the second step part is provided with a heat insulating device, and the heat insulating device is used to support a first surface of a substrate to be processed, and the first step part The diameter of the inner wall is greater than the diameter of the inner wall of the second stepped portion. The substrate tray according to claim 1, wherein the thermal insulation device includes a thermal insulation ring, the bottom surface of the thermal insulation ring is placed on the second step portion, and the top of the second step portion includes a support surface for For supporting the substrate to be processed, a vertical side wall surrounds the supporting surface. The substrate tray as claimed in claim 1, wherein the heat insulating device includes a heat insulating ring, and the top of the heat insulating ring includes a plurality of upwardly protruding ribs, and the substrate is placed on the upwardly protruding ribs. on the edge. The substrate tray according to claim 3, wherein the bottom surface of the heat insulation ring includes the plurality of downwardly protruding ribs, and the heat insulating ring passes through the plurality of downwardly protruding ribs and the second step portion touch. The substrate tray according to claim 1, wherein the heat insulating device comprises a plurality of support claws arranged separately along the circumferential direction, the support claws are arranged on the second step part, and at least part of the top is used to support the substrate. piece. The substrate tray as claimed in claim 5, wherein the supporting claw comprises a horizontally extending portion and a vertically extending portion, wherein a bottom plane of the horizontally extending portion is placed on the second step portion, and a portion of the horizontally extending portion The top cross-section is smaller than the bottom plane. The substrate tray according to claim 6, wherein the vertical extension is located outside the horizontal extension, and the cross-section of the vertical extension near the central open end of the substrate tray is tapered such that the side wall of the substrate The contact area with this vertical extension is minimized. The substrate tray as claimed in claim 5, wherein the supporting claw includes a tray connection portion, a lower extension portion and a substrate support portion, and the bottom surface of the tray connection portion obtains the second step portion One end of the lower extension part is connected to the tray connection part, and the other end extends downwards and is connected to the substrate support part, and the top of the substrate support part is used to support the substrate to be processed, so that The first surface of the substrate is lower than the top surface of the second stepped portion. The substrate tray of claim 8, wherein the substrate support portion extends in a horizontal direction, wherein a cross-section of a top of the substrate support portion is smaller than a cross-section of a bottom of the substrate support portion. The substrate tray as claimed in claim 8, wherein the lower extension near the central open end of the substrate tray has a tapered cross-section, so that the contact area between the sidewall of the substrate and the vertical extension is minimized. The substrate tray as claimed in claim 1, wherein the thermal insulation device is made of a material having a first thermal conductivity, and the substrate tray is made of a material having a second thermal conductivity, wherein the first thermal conductivity The coefficient is less than 1/4 of the second thermal conductivity. The substrate tray according to claim 1, wherein the thermal conductivity of the thermal insulation device is less than or equal to 40W/m.k, and the thermal conductivity of the substrate tray is greater than or equal to 150W/m.k. An MOCVD reactor, comprising a reaction chamber, wherein: a substrate tray according to any one of claims 1-12 is set in the reaction chamber.

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