A substrate heater suitable for use in a molecular beam epitaxy apparatus and a method of manufacturing the same

Abstract

The application discloses a substrate heater suitable for a molecular beam epitaxy device, which comprises a disc-shaped boron nitride pyrolytic base, a pyrolytic graphite coating arranged on the boron nitride pyrolytic base and a boron nitride pyrolytic protective coating arranged on the pyrolytic graphite coating, an inner ring circuit and an outer ring circuit are arranged on the pyrolytic graphite coating, and the inner ring circuit and the outer ring circuit are respectively led out by electrodes to realize independent heating. The application further discloses a manufacturing method of the heater, which comprises the following steps: S1, depositing a pyrolytic graphite coating on a boron nitride pyrolytic base; S2, processing a circuit pattern on the pyrolytic graphite coating; and S3, depositing a boron nitride pyrolytic protective coating on the pyrolytic graphite coating. The application has the advantages of high material purity, low outgassing rate, good mechanical property in a high-temperature environment, convenient flexible adjustment of the circuit design for different application scenes and the like, and the temperature uniformity is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor equipment technology, and in particular to a substrate heater suitable for molecular beam epitaxy equipment and its manufacturing method. Background Technology

[0002] In the field of semiconductor thin film fabrication technology, the temperature uniformity of the substrate surface directly affects the thickness uniformity, composition uniformity, doping uniformity, and batch repeatability of the epitaxial material. This is especially true for substrate heaters used in molecular beam epitaxy (MBE) equipment, where the system operates in an ultra-high vacuum environment, thus requiring high purity heater materials and low outgassing rates. MBE equipment uses a fixed heater to heat a rotating substrate disk via thermal radiation, requiring a maximum heating temperature ≥1000℃, temperature control accuracy ≤±0.2℃, and temperature uniformity ≤±5℃.

[0003] The larger the substrate disk size, the more challenging it is to design the heater uniformity. Generally, heat is not easily dissipated at the center of the heater, while heat loss is more severe at the edges, thus requiring compensation for the edge regions. For different models of molecular beam epitaxy (MBE) equipment, such as models supporting single 4-inch substrate epitaxy compatible with three 2-inch substrates, models supporting single 6-inch substrate epitaxy compatible with three 3-inch substrates, models supporting four 6-inch substrates compatible with nine 4-inch substrates, and models supporting seven 6-inch substrates compatible with fourteen 4-inch substrates, heaters need to be specifically designed to meet the heating requirements of different numbers and sizes of substrates. In addition, the absorption rates of thermal radiation by the substrate and the molybdenum support in the substrate disk are different. Especially when multiple substrates are epitaxially grown at the same time, after the substrate disk rotates, the temperature effect is averaged along the radial direction of the substrate disk. The temperature is low in the radius where the substrate accounts for a large proportion, and the temperature is high in the radius where the molybdenum support accounts for a large proportion, which is distributed in a "saddle" shape. Therefore, the temperature zone design of the heater and the circuit layout need to be fully considered.

[0004] Existing molecular beam epitaxy equipment generally uses refractory metals as heating elements for substrate heaters, such as tantalum wires, tungsten wires, or tantalum or tungsten sheets. The design of metal wires or sheets has certain drawbacks. First, the cross-section of the metal wires or sheets may be uneven, resulting in local hot spots. Second, at high temperatures, the metal wires or sheets are prone to deformation or displacement, which can lead to deterioration of heater performance or hardware damage. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a substrate heater suitable for molecular beam epitaxy equipment with high material purity, low outgassing rate, good mechanical properties under high temperature environment, and convenient circuit design that can be flexibly adjusted for different application scenarios to improve temperature uniformity.

[0006] The present invention further provides a method for manufacturing the above-mentioned substrate heater suitable for molecular beam epitaxy equipment.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A substrate heater suitable for molecular beam epitaxy equipment includes a disc-shaped pyrolytic boron nitride substrate, a pyrolytic graphite coating disposed on the pyrolytic boron nitride substrate, and a pyrolytic boron nitride protective coating disposed on the pyrolytic graphite coating. The pyrolytic graphite coating is provided with an inner ring circuit and an outer ring circuit, and the inner ring circuit and the outer ring circuit are respectively led out by electrodes to achieve independent heating.

[0009] As a further improvement to the above technical solution: the outline of the inner circuit is a circle, a square, a regular hexagon, a regular octagon, a regular dodecagon, or a regular sixteen-sided polygon.

[0010] As a further improvement to the above technical solution: when the outline of the inner ring circuit is circular, both the inner ring circuit and the outer ring circuit include multiple concentric and uniformly arranged arc-shaped patterns. The arc-shaped patterns include at least two arcs with a gap between adjacent two arcs, and the gaps between the arc-shaped patterns in each ring are staggered.

[0011] As a further improvement to the above technical solution: when the outline of the inner ring circuit is a square, a regular hexagon, a regular octagon, or a regular sixteen-fold shape, the inner ring circuit includes multiple evenly arranged parallel zigzag lines, and the outer ring circuit has multiple evenly arranged parallel zigzag lines in the areas corresponding to each side of the inner ring circuit.

[0012] As a further improvement to the above technical solution: the width of the texture of the inner ring circuit is greater than the width of the texture of the outer ring circuit.

[0013] As a further improvement to the above technical solution: the resistance value of the inner circuit and the resistance value of the outer circuit are both 10Ω to 20Ω.

[0014] As a further improvement to the above technical solution: at least one middle ring circuit is provided between the inner ring circuit and the outer ring circuit, and the outline of the middle ring circuit is the same as the outline of the inner ring circuit.

[0015] As a further improvement to the above technical solution: the substrate heater suitable for molecular beam epitaxy equipment also includes a pyrolytic boron nitride homogenizing plate disposed between the pyrolytic boron nitride protective coating and the substrate.

[0016] As a further improvement to the above technical solution: the pyrolytic boron nitride substrate, the pyrolytic graphite coating, and the pyrolytic boron nitride protective coating are provided with through holes at their centers.

[0017] A method for manufacturing a substrate heater suitable for molecular beam epitaxy equipment includes the following steps;

[0018] S1. Depositing a pyrolytic graphite coating on a pyrolytic boron nitride substrate;

[0019] S2. Processing circuit patterns on pyrolytic graphite coating;

[0020] S3. Deposit a pyrolytic boron nitride protective coating on the pyrolytic graphite coating.

[0021] Compared with the prior art, the advantages of the present invention are as follows: The substrate heater disclosed in the present invention, which is suitable for molecular beam epitaxy equipment, comprises a pyrolytic boron nitride substrate, a pyrolytic graphite coating, and a pyrolytic boron nitride protective coating. The material has high purity and low outgassing rate, and is an integrally formed structure with good mechanical properties under high temperature environment. The pyrolytic graphite coating is provided with inner and outer ring circuits, which are heated independently. The circuit design can be flexibly adjusted for different application scenarios, which is conducive to ensuring temperature uniformity.

[0022] The present invention discloses a method for manufacturing a substrate heater suitable for molecular beam epitaxy equipment. This method involves few steps, is easy to operate, and produces a heater with a one-piece molded structure and good mechanical properties at high temperatures. Attached Figure Description

[0023] Figure 1 This is a schematic cross-sectional view of the substrate heater of the present invention applicable to molecular beam epitaxy equipment.

[0024] Figure 2 This is a schematic diagram of the planar structure of the dual-temperature zone pyrolytic graphite coating in this invention.

[0025] Figure 3 This is a schematic diagram of the structure of the first embodiment of the dual-temperature zone pyrolytic graphite coating circuit in this invention.

[0026] Figure 4 This is a schematic diagram of the second embodiment of the dual-temperature zone pyrolytic graphite coating circuit in this invention.

[0027] Figure 5 This is a schematic diagram of the planar structure of the three-temperature-zone pyrolytic graphite coating in this invention.

[0028] The labels in the figure represent: 11, pyrolytic boron nitride substrate; 12, pyrolytic graphite coating; 121, inner circuit; 122, outer circuit; 123, middle circuit; 13, pyrolytic boron nitride protective coating; 21, substrate; 22, molybdenum support; 3, pyrolytic boron nitride heat exchanger. Detailed Implementation

[0029] As indicated in this section and the claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include the plural. The terms "first," "second," and similar terms used in this section do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "comprising" or "including" mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, without excluding other elements or objects. The terms "connected" or "linked" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1

[0032] Figures 1 to 4 This illustration shows an embodiment of the substrate heater of the present invention applicable to molecular beam epitaxy equipment. This embodiment is a dual-temperature zone composite ceramic heater, comprising a disc-shaped pyrolytic boron nitride (PBN) substrate 11, a pyrolytic graphite (PG) coating 12, and a pyrolytic boron nitride (PBN) protective coating 13. The composite ceramic heater is constructed by depositing a conductive pyrolytic graphite coating 12 on an insulating pyrolytic boron nitride substrate 11, then engraving a circuit pattern using laser or mechanical methods to form a pyrolytic graphite coating circuit, and finally depositing a pyrolytic boron nitride protective coating 13.

[0033] The substrate disk portion includes one or more substrates 21 and a molybdenum support 22 for supporting the substrates 21. Figure 1 The diagram shows a single-piece configuration. Further, a pyrolytic boron nitride uniform heating plate 3 is added between the dual-temperature zone composite ceramic heater and the substrate disk. Its functions are twofold: firstly, to improve temperature uniformity, and secondly, to protect the composite ceramic heater from contamination by the injected source material below. The diameter of the dual-temperature zone composite ceramic heater and the pyrolytic boron nitride uniform heating plate 3 is slightly larger than that of the substrate disk, thus completely covering the heating of the substrate disk.

[0034] Figure 2 A schematic diagram of the planar structure of the dual-temperature zone pyrolytic graphite coating of the present invention is shown. Figure 2 a, Figure 2 b illustrates two different slide mounting scenarios: Figure 2 a represents the design of the inner circuit 121 with a circular outline, corresponding to... Figure 2 C. Heating of a single, larger substrate 21; Figure 2 b represents the design of the inner ring circuit 121 with a square outline, corresponding to... Figure 2 Multiple smaller substrates 21 in d are heated.

[0035] The circuit of the pyrolytic graphite coating 12 adopts a dual-temperature zone design, consisting of an inner circuit 121 and an outer circuit 122. The inner circuit 121 and the outer circuit 122 are heated independently, each led out by a set of electrodes (not shown in the figure), which are respectively connected to an external DC power supply and a temperature controller for heating and temperature control.

[0036] For the same type of molecular beam epitaxy equipment, the most suitable pyrolytic graphite coating 12 circuit design can be selected according to different substrate disk types. The outline of the inner ring circuit 121 can be circular, square, regular hexagonal, regular octagonal, regular dodecagonal, or regular sixteen-sided. The outer ring circuit 122 is adjusted accordingly based on the shape of the inner ring circuit 121 to meet the heating requirements of different numbers and sizes of substrates 21 and achieve optimal temperature uniformity.

[0037] For heating a single, large-sized substrate 21, such as a single 6-inch substrate 21, this embodiment adopts a circular inner ring circuit 121 and an annular outer ring circuit 122 design. The circuit layout consists of multiple arc-shaped patterns evenly arranged from the center to the outer periphery. The arc-shaped patterns include at least two spaced arcs, and the intervals between the arc-shaped patterns are staggered.

[0038] For heating multiple smaller substrates 21, such as three 3-inch substrates, this embodiment uses a square inner circuit 121 design, with the outer circuit 122 densely filling the other areas of the circumference. The circuit layout consists of evenly arranged parallel zigzag lines. Of course, in other embodiments, the inner circuit 121 can also be designed as a regular hexagon, regular octagon, or other regular polygons. The regular polygon design breaks the symmetry of the circle, and after superimposing the rotation effect of the substrate disk, a transition area is formed between the inner and outer temperature zones, avoiding abrupt changes in temperature gradients at the temperature zone boundaries and improving the flexibility of temperature adjustment.

[0039] Preferably, the conductive texture of the pyrolytic graphite coating 12 can be optimized so that the texture width of the inner circuit 121 is greater than that of the outer circuit 122. This results in the outer circuit 122 generating more heat per unit length than the inner circuit 121, compensating for heat dissipation at the heater edge and further improving temperature uniformity. The resistance value of the inner circuit 121 is similar to the total resistance value of the outer circuit 122, both ranging from 10Ω to 20Ω.

[0040] The dual-temperature zone composite ceramic heater has a through hole (not shown in the figure) in the center, which can be used to install a thermocouple for temperature measurement. Preferably, both the inner and outer temperature zones of the dual-temperature zone composite ceramic heater adopt PID temperature control, which can achieve a maximum heating temperature greater than 1000℃, a temperature control accuracy better than ±0.2℃, and a temperature uniformity better than ±3℃, fully meeting the requirements of substrate heaters for molecular beam epitaxy equipment.

[0041] Figure 3The diagram illustrates the inner ring circuit of a dual-temperature zone composite ceramic heater according to an embodiment of the present invention. The inner ring circuit 121 has a circular outline, while the outer ring circuit 122 has an annular outline. The two circuits are heated independently, each led out by a set of symmetrical electrodes. The inner ring circuit 121 and the outer ring circuit 122 employ a uniformly arranged arc-shaped conductive pattern design, with the pattern width of the inner ring circuit 121 being greater than that of the outer ring circuit 122.

[0042] Figure 4 The diagram illustrates the inner ring circuit of a square-outlined dual-temperature zone composite ceramic heater according to Embodiment 2 of the present invention. The inner ring circuit 121 has a square outline, while the outer ring circuit 122 densely fills the surrounding area excluding the inner ring circuit 121. The two circuits are heated independently, each led out by a set of symmetrical electrodes. The inner ring circuit 121 and outer ring circuit 122 employ a uniformly arranged parallel zigzag pattern design, with the zigzag width of the inner ring circuit 121 being greater than that of the outer ring circuit 122.

[0043] Example 2

[0044] Dual-zone composite ceramic heaters can be expanded to three-zone or even more-zone designs to meet the heating needs of larger and more numerous substrates. Figure 5 This paper illustrates another embodiment of the substrate heater applicable to molecular beam epitaxy equipment. This embodiment is a large-area three-zone composite ceramic heater, which consists of an inner ring circuit 121, a middle ring circuit 123, and an outer ring circuit 122. The inner ring circuit 121 and the middle ring circuit 123 adopt a concentric hexagonal design, and the circuit layout is a uniformly arranged parallel zigzag pattern. The above-mentioned three-zone composite ceramic heater is suitable for heating large-area substrate disks, such as epitaxy of 4 6-inch or 9 4-inch substrates, or epitaxy of 7 6-inch or 14 4-inch substrates. By optimizing the temperature zone design and circuit layout of the three-zone composite ceramic heater, highly uniform and efficient heating of multiple substrates 21 can be achieved.

[0045] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A substrate heater suitable for molecular beam epitaxy equipment, characterized in that: The substrate heater suitable for molecular beam epitaxy equipment comprises a disc-shaped pyrolytic boron nitride base body (11), a pyrolytic graphite coating (12) arranged on the pyrolytic boron nitride base body (11), and a pyrolytic boron nitride protective coating (13) arranged on the pyrolytic graphite coating (12), wherein the pyrolytic graphite coating (12) is provided with an inner ring circuit (121) and an outer ring circuit (122), the inner ring circuit (121) and the outer ring circuit (122) are respectively led out by electrodes to realize independent heating; the substrate heater suitable for molecular beam epitaxy equipment further comprises a pyrolytic boron nitride heat uniformizing sheet (3) arranged between the pyrolytic boron nitride protective coating (13) and a substrate (21), which is used for improving temperature uniformity and preventing contamination of an ejection source; the contour of the inner ring circuit (121) is a square, a regular hexagon, a regular octagon, a regular dodecagon or a regular hexadecagon, the inner ring circuit (121) comprises a plurality of uniformly arranged parallel zigzag lines, and the outer ring circuit (122) is respectively provided with a plurality of uniformly arranged parallel zigzag lines in regions corresponding to each side of the inner ring circuit (121).

2. A substrate heater suitable for use in a molecular beam epitaxy apparatus according to claim 1, wherein: The width of the lines of the inner ring circuit (121) is greater than the width of the lines of the outer ring circuit (122).

3. A substrate heater suitable for use in a molecular beam epitaxy apparatus according to claim 2, wherein: The resistance value of the inner ring circuit (121) and the resistance value of the outer ring circuit (122) are both 10Ω-20Ω.

4. A substrate heater suitable for use in a molecular beam epitaxy apparatus according to any one of claims 1 to 3, characterised in that: At least one middle ring circuit (123) is arranged between the inner ring circuit (121) and the outer ring circuit (122), and the contour of the middle ring circuit (123) is the same as that of the inner ring circuit (121).

5. A substrate heater suitable for use in a molecular beam epitaxy apparatus according to any one of claims 1 to 3, characterised in that: The pyrolytic boron nitride base body (11), the pyrolytic graphite coating (12) and the pyrolytic boron nitride protective coating (13) are provided with through holes at the centers thereof.

6. A method of manufacturing a substrate heater for a molecular beam epitaxy apparatus according to any one of claims 1 to 5, characterized by: The method comprises the following steps: S1, depositing a pyrolytic graphite coating (12) on a pyrolytic boron nitride base body (11) base body; S2, processing a circuit pattern on the pyrolytic graphite coating (12); S3, depositing a pyrolytic boron nitride protective coating (13) on the pyrolytic graphite coating (12).

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