Epitaxial structure and preparation method thereof, and epitaxial layer thickness monitoring method of epitaxial structure

Abstract

The invention discloses an epitaxial structure and a preparation method thereof, and an epitaxial layer thickness monitoring method of the epitaxial structure. The preparation method of the epitaxial structure comprises the steps that an epitaxial layer base is formed, and the epitaxial layer base comprises a substrate and an interface reflecting layer; forming an epitaxial layer on the epitaxial layer substrate; wherein the refractive indexes of the epitaxial layer and the interface reflecting layer are different, and the substrate and the epitaxial layer are made of the same material; and when the epitaxial layer is formed on the epitaxial layer substrate, the thickness of the epitaxial layer is monitored in real time by using an optical method. The method can reduce the monitoring difficulty of the thickness of the epitaxial layer in the manufacturing process of the epitaxial structure.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an epitaxial structure and a preparation method thereof, and a method for monitoring the thickness of an epitaxial layer of the epitaxial structure. Background Art

[0002] With the development of semiconductor technology, epitaxial structures are increasingly used in the field of semiconductor technology, and correspondingly, the quality requirements for epitaxial structures are also high.

[0003] The thickness uniformity of the epitaxial layer in the epitaxial structure has an important impact on the quality of the epitaxial structure, and it is very important to monitor the thickness of the epitaxial layer. However, in the related art, when the epitaxial layer and the substrate are made of homogeneous materials, it is difficult to monitor the thickness of the epitaxial layer. Generally, after growing a certain epitaxial thickness, the epitaxial wafer is taken out of the growth furnace, and the thickness is measured and then adjusted. Sometimes, in order to ensure that the thickness meets the requirements as much as possible, it is even necessary to take it out for measurement and adjustment multiple times, which is very time-consuming and cost-intensive. In addition, the thickness accuracy is not enough, which is a major problem in homoepitaxial growth. Summary of the invention

[0004] The present invention provides an epitaxial structure and a preparation method thereof, and an epitaxial layer thickness monitoring method of the epitaxial structure, so as to reduce the difficulty of monitoring the epitaxial layer thickness during the epitaxial structure manufacturing process.

[0005] According to one aspect of the present invention, there is provided a method for preparing an epitaxial structure, comprising:

[0006] forming an epitaxial layer substrate, wherein the epitaxial layer substrate comprises a substrate and an interface reflection layer;

[0007] forming an epitaxial layer on the epitaxial layer substrate;

[0008] The epitaxial layer and the interface reflection layer have different refractive indices, and the substrate and the epitaxial layer are made of the same material; when the epitaxial layer is formed on the epitaxial layer substrate, the method further includes: using an optical method to monitor the thickness of the epitaxial layer in real time.

[0009] Optionally, forming an epitaxial layer substrate comprises:

[0010] providing the substrate;

[0011] forming the interface reflection layer on one side of the substrate;

[0012] The step of forming an epitaxial layer on the epitaxial layer substrate comprises:

[0013] The epitaxial layer is formed on the other side of the substrate.

[0014] Optionally, after forming the epitaxial layer on the epitaxial layer substrate, the method further includes:

[0015] The interface reflective layer is removed.

[0016] Optionally, forming an epitaxial layer substrate comprises:

[0017] providing the substrate;

[0018] forming the interface reflection layer on the substrate;

[0019] The step of forming an epitaxial layer on the epitaxial layer substrate comprises:

[0020] The epitaxial layer is formed on the interface reflection layer, wherein the lattice constant of the interface reflection layer matches that of the epitaxial layer.

[0021] Optionally, the material of the interface reflection layer is InAlN, wherein the In component ranges from 15% to 19%.

[0022] Optionally, the thickness of the interface reflection layer ranges from 10 nm to 100 nm.

[0023] Optionally, the material of the substrate and the epitaxial layer is gallium nitride.

[0024] According to another aspect of the present invention, there is provided an epitaxial structure, the epitaxial structure comprising:

[0025] An epitaxial layer substrate, the epitaxial layer substrate comprising a substrate and an interface reflection layer;

[0026] The epitaxial layer is arranged on the epitaxial layer substrate; wherein the epitaxial layer and the substrate are made of the same material; the epitaxial layer and the interface reflection layer have different refractive indices and lattice constants.

[0027] Optionally, the material of the interface reflection layer is InAlN, wherein the In component ranges from 15% to 19%.

[0028] According to another aspect of the present invention, a method for monitoring the thickness of an epitaxial layer of an epitaxial structure is provided, wherein the epitaxial structure comprises an epitaxial layer substrate and an epitaxial layer, wherein the epitaxial layer substrate comprises a substrate and an interface reflection layer; the epitaxial layer and the interface reflection layer have different refractive indices, and the substrate and the epitaxial layer are made of the same material;

[0029] The method for monitoring the thickness of the epitaxial layer comprises: when the epitaxial layer is formed on the epitaxial layer substrate, using an optical method to monitor the thickness of the epitaxial layer in real time.

[0030] The technical solution of the embodiment of the present invention adopts a method for preparing an epitaxial structure, which includes: forming an epitaxial layer substrate, the epitaxial layer substrate includes a substrate and an interface reflection layer; forming an epitaxial layer on the epitaxial layer substrate; wherein the epitaxial layer and the interface reflection layer have different refractive indices, and the substrate and the epitaxial layer are made of the same material; when forming the epitaxial layer on the epitaxial layer substrate, it also includes: using an optical method to monitor the thickness of the epitaxial layer in real time. By setting the interface reflection layer, when growing the homogeneous epitaxial layer material on the substrate, the thickness of the epitaxial layer can be monitored in real time, thereby improving the thickness accuracy and growth efficiency of the homogeneous epitaxial layer; because the interface reflection layer is grown on one side of the substrate, the measurement light can be reflected back to the epitaxial layer, thereby forming two beams of reflected light, and then the interference principle of light can be used to monitor the film thickness of the epitaxial layer in real time.

[0031] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 A flow chart of a method for preparing an epitaxial structure provided in Embodiment 1 of the present invention;

[0034] Figure 2 A flow chart of a method for preparing an epitaxial structure provided in Embodiment 2 of the present invention;

[0035] Figure 3 A schematic diagram of an epitaxial structure provided in Embodiment 2 of the present invention;

[0036] Figure 4 A flowchart of a method for preparing an epitaxial structure provided in Embodiment 3 of the present invention;

[0037] Figure 5 A schematic structural diagram of an epitaxial structure provided in Embodiment 3 of the present invention. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme 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 are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0039] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0040] Embodiment 1

[0041] Figure 1 A flowchart of a method for preparing an epitaxial structure provided in Example 1 of the present invention, referring to Figure 1 , the method for preparing the epitaxial structure comprises:

[0042] Step S101, forming an epitaxial layer substrate, wherein the epitaxial layer substrate includes a substrate and an interface reflective layer;

[0043] Specifically, the substrate is used to provide support for the epitaxial structure grown on the substrate, and the interface reflection layer is used to provide a light reflection interface.

[0044] Step S102, forming an epitaxial layer on the epitaxial layer substrate, wherein the epitaxial layer and the interface reflective layer have different refractive indices, and the epitaxial layer and the substrate have the same material, and when the epitaxial layer is formed on the epitaxial layer substrate, it also includes: monitoring the thickness of the epitaxial layer by an optical method. It should be noted that the epitaxial layer described in this embodiment represents the epitaxial layer closest to the substrate, and the epitaxial structure may include multiple epitaxial layers, and the epitaxial layers other than the epitaxial layer closest to the substrate may be made of the same material as the substrate or different material.

[0045] Specifically, the optical method monitors the film thickness, for example, it can be an in-situ detection method, etc., which mainly uses the reflection of light on the two surfaces of the film layer. Because the optical path difference is different, the two beams of light reflected on the upper surface and the lower surface interfere with each other. The interference principle of light is used to measure the film thickness. When the thickness is different, the interference effect is inconsistent. The specific formula for measuring thickness is well known to those skilled in the art and will not be repeated here. In the related art, in order to obtain an epitaxial layer of better quality, the epitaxial layer and the substrate are set to be the same material. However, when the substrate and the epitaxial layer are homogeneous materials, when light is irradiated to the surface where the epitaxial layer contacts the substrate, the light will not be reflected, but will be completely incident on the substrate. Therefore, the epitaxial layer only reflects light on the upper surface, and the lower surface will not reflect light. It is also impossible to use the interference principle of two beams of reflected light to measure the film thickness. At this time, the epitaxial structure needs to be taken out and measured, and then the epitaxial parameters are readjusted according to the measurement results before growth. This approach greatly increases the time cost and the cost of manpower and materials. In this embodiment, during the growth of the epitaxial layer homogeneous with the substrate, an interface reflection layer is provided, and the refractive index of the interface reflection layer is set to be different from the refractive index of the epitaxial layer, so that light will be reflected when incident on the surface of the interface reflection layer close to the epitaxial layer, and this beam of reflected light will interfere with the light reflected when incident on the upper surface of the epitaxial layer (the surface far away from the interface reflection layer), and then the film thickness of the epitaxial layer can be monitored in real time using the principle of light interference. In other words, when making the epitaxial layer, the epitaxial structure does not need to be taken out of the epitaxial device for thickness measurement, and the thickness can be measured directly in the epitaxial device using an optical method, thereby achieving real-time monitoring.

[0046] It should be noted that monitoring the thickness of the epitaxial layer may specifically include monitoring the uniformity of the thickness of the epitaxial layer, specifically monitoring the uniformity of the thickness from the center to the edge of the epitaxial layer, and using a sensor to receive two beams of reflected light to calculate and obtain real-time thickness information. When it is monitored that the thickness of the epitaxial layer is uneven, the epitaxial parameters of the epitaxial layer are adjusted in time to ensure the uniformity of the epitaxial layer film.

[0047] The technical solution of this embodiment adopts a method for preparing an epitaxial structure, which includes: forming an epitaxial layer substrate, the epitaxial layer substrate includes a substrate and an interface reflection layer; forming an epitaxial layer on the epitaxial layer substrate; wherein the epitaxial layer and the interface reflection layer have different refractive indices, and the substrate and the epitaxial layer are made of the same material; when the epitaxial layer is formed on the epitaxial layer substrate, it also includes: using an optical method to monitor the thickness of the epitaxial layer in real time. By setting the interface reflection layer, when the substrate and the epitaxial layer are made of the same material, light can still be reflected back to the epitaxial layer, thereby forming two beams of reflected light, and then the interference principle of light can be used to monitor the film thickness of the epitaxial layer, without taking out the epitaxial structure, thereby greatly reducing the difficulty of monitoring the thickness of the epitaxial layer during the epitaxial structure manufacturing process.

[0048] Embodiment 2

[0049] Figure 2 A flowchart of a method for preparing an epitaxial structure provided in Embodiment 2 of the present invention, Figure 3 A schematic diagram of an epitaxial structure provided in the second embodiment of the present invention, combined with Figure 2 and Figure 3 In this embodiment, forming the epitaxial layer substrate includes:

[0050] Step S201, providing a substrate;

[0051] Step S202, forming an interface reflection layer on one side of the substrate;

[0052] Specifically, in the finished epitaxial structure, the substrate 10 and the interface reflective layer 11 can be an integral structure, that is, the interface reflective layer 11 can be formed by growing on one side of the substrate 10. Alternatively, the substrate 10 and the interface reflective layer 11 can also be independent structures. In other words, the substrate 10 and the interface reflective layer 11 are formed independently, and then the substrate 10 is placed on the interface reflective layer 10, and it is only necessary to maintain a fixed position during the growth of the epitaxial layer to facilitate real-time monitoring. This arrangement can facilitate the subsequent removal of the interface reflective layer, thereby reducing the thickness of the epitaxial structure. In this embodiment, the interface reflective layer 11 can be a material with a different refractive index from the epitaxial layer 13.

[0053] Forming an epitaxial layer on an epitaxial layer substrate includes:

[0054] Step S203, forming an epitaxial layer on the other side of the substrate.

[0055] Specifically, the material of the substrate 10 can be gallium nitride, and the material of the epitaxial layer 13 is the same material as the substrate 10, which is also gallium nitride. By growing a gallium nitride epitaxial layer on a gallium nitride substrate, the dislocation problem of the homogeneously grown gallium nitride epitaxial layer is greatly improved, and there is no stress problem caused by lattice constant mismatch and thermal expansion coefficient mismatch. When using optical methods to monitor the thickness of the epitaxial layer, such as Figure 3 As shown, the incident light is reflected at the surface of the epitaxial layer 12 away from the interface reflection layer 11 to form a first reflection light. The light transmitted to the epitaxial layer 12 will not be reflected at the interface between the epitaxial layer 12 and the substrate 10, but will be directly incident into the substrate 10, and then reflected at the interface between the substrate 10 and the interface reflection layer 11, and finally emitted from the surface of the epitaxial layer 12 away from the interface reflection layer 11 to form a second reflection light. The interference of the first reflection light and the second reflection light is used to realize real-time monitoring of the thickness of the epitaxial layer 12.

[0056] Optionally, after forming the epitaxial layer on the epitaxial layer substrate, the method further includes: removing the interface reflective layer. This arrangement can reduce the overall thickness of the epitaxial structure, thereby facilitating the reduction of the size of the chip formed by the epitaxial structure.

[0057] Embodiment 3

[0058] Figure 4 A flowchart of a method for preparing an epitaxial structure provided in Embodiment 3 of the present invention, Figure 5 A schematic diagram of an epitaxial structure provided in the third embodiment of the present invention, combined with Figure 4 and Figure 5 .

[0059] In this embodiment, forming the epitaxial layer substrate includes:

[0060] Step S301, providing a substrate;

[0061] Specifically, in this embodiment, the substrate 10 may be a gallium nitride substrate.

[0062] Step S302, forming an interface reflection layer on the substrate;

[0063] Specifically, in this embodiment, the interface reflection layer 11 and the substrate 10 are an integral structure, that is, the interface reflection layer 11 is grown on the interface reflection layer 11 by a growth method.

[0064] Forming an epitaxial layer on an epitaxial layer substrate includes:

[0065] Step S303 , forming an epitaxial layer on the interface reflective layer, wherein the lattice constants of the interface reflective layer and the epitaxial layer match.

[0066] Specifically, in this embodiment, by setting the lattice constant of the interface reflection layer to match that of the epitaxial layer, that is, the lattice constants are the same, when the epitaxial layer is formed, no stress is generated in the epitaxial layer, and no additional dislocations are introduced. Therefore, the advantages of growing the epitaxial layer on the homogeneous substrate can be retained, and the quality of the epitaxial layer is not affected. At the same time, the growth thickness of the epitaxial layer can be monitored in real time. When the thickness of the epitaxial layer is monitored by optical methods, such as Figure 5 As shown, the incident light is reflected on the surface of the epitaxial layer 12 away from the interface reflection layer 11 to form a first reflected light. The light transmitted to the epitaxial layer 12 is reflected at the interface between the epitaxial layer 12 and the interface reflection layer 11, and finally emitted from the surface of the epitaxial layer 12 away from the interface reflection layer 11 to form a second reflected light. The interference between the first reflected light and the second reflected light is used to monitor the thickness of the epitaxial layer 12.

[0067] Optionally, the material of the interface reflection layer 12 is InAlN, wherein the In component ranges from 15% to 19%.

[0068] Specifically, the materials of the epitaxial layer 12 and the substrate 10 are both gallium nitride. The lattice constant of the material of the interface reflection layer 12 of this embodiment is consistent with the lattice constant of gallium nitride, so that the interface reflection layer 12 will not generate any stress to the subsequently grown gallium nitride epitaxial layer, thereby ensuring that the quality of gallium nitride epitaxy is not affected. In addition, the temperature of InAlN growth is low, the growth conditions are not harsh, and the growth materials are easy to obtain, which will not put pressure on equipment and costs.

[0069] Optionally, the thickness of the interface reflection layer 11 is in the range of 10 nm to 100 nm.

[0070] Specifically, if the thickness of the interface reflection layer 11 is too thin, the interface of the interface reflection layer 11 will be unclear, the intensity of the reflected light will be insufficient, and the thickness information obtained by measurement will be unclear and the thickness information error will be large. If the thickness of the interface reflection layer 11 is too thick, the overall size of the epitaxial structure will be thicker, which is not conducive to the miniaturization of the epitaxial structure. The thickness range setting of this embodiment will neither increase the cost by requiring too high a measurement accuracy, nor make the overall size of the epitaxial structure thicker.

[0071] Optionally, the interface reflective layer is grown by continuous growth or pulse growth.

[0072] Specifically, the continuous growth method is to introduce Al source, In source and NH3 into the cavity at the same time to grow InAlN. The pulse growth method is to introduce In source and Al source into the cavity at the same time for a period of time, but NH3 is not introduced into the cavity during this period; in the next period of time, NH3 is introduced into the cavity, but In source and Al source are not introduced into the cavity. Alternatively, it can be a pulse growth method in which In source, Al source and NH3 are introduced into the cavity at different time periods.

[0073] Embodiment 4

[0074] The present invention also provides an epitaxial structure, which includes: an epitaxial layer substrate, which includes a substrate and an interface reflection layer; an epitaxial layer, which is arranged on the epitaxial layer substrate; wherein the epitaxial layer and the substrate are made of the same material; the epitaxial layer and the interface reflection layer have different refractive indices and match lattice constants.

[0075] Specifically, the epitaxial structure in this embodiment can be Figure 3 or Figure 5 The specific working principle and beneficial effects of the epitaxial structure shown can be referred to the description of the method for preparing the epitaxial structure in the embodiment of the present invention, which will not be repeated here.

[0076] Optionally, the material of the interface reflection layer is InAlN, wherein the In component ranges from 15% to 19%.

[0077] Optionally, the thickness of the interface reflective layer ranges from 10 nm to 100 nm.

[0078] Optionally, the material of the epitaxial layer is gallium nitride, and the material of the substrate is gallium nitride.

[0079] Embodiment 5

[0080] The embodiment of the present invention also provides a method for monitoring the thickness of an epitaxial layer of an epitaxial structure, wherein the epitaxial structure includes an epitaxial layer substrate and an epitaxial layer, wherein the epitaxial layer substrate includes a substrate and an interface reflection layer; the epitaxial layer and the interface reflection layer have different refractive indices; and the substrate and the epitaxial layer are made of the same material;

[0081] The method for monitoring the thickness of the epitaxial layer includes: when the epitaxial layer is formed on the epitaxial layer substrate, using an optical method to monitor the thickness of the epitaxial layer in real time.

[0082] Specifically, in the epitaxial device, the epitaxial layer is formed epitaxially on the epitaxial substrate. For homoepitaxial layers (the substrate and the epitaxial layer are made of the same material), the conventional epitaxial structure cannot monitor the thickness of the homoepitaxial layer in real time using optical methods. When the thickness of the epitaxial layer needs to be measured, the epitaxial structure needs to be taken out and then measured, and real-time thickness measurement cannot be achieved. In this embodiment, by setting an interface reflection layer, when the thickness is measured using an optical method, the light can be reflected back to the epitaxial layer, thereby forming two beams of reflected light, and then the interference principle of light can be used to monitor the film thickness of the epitaxial layer, without the need to take out the epitaxial structure, thereby greatly reducing the difficulty of monitoring the thickness of the epitaxial layer during the epitaxial structure manufacturing process.

[0083] The epitaxial layer thickness monitoring method of the epitaxial structure of this embodiment can monitor the thickness of the epitaxial layer in real time, thereby greatly shortening the preparation time of the epitaxial structure. When the epitaxial layer thickness is abnormal, it can be discovered in time, and then the thickness of the epitaxial layer can be adjusted to reduce the defective rate of the epitaxial structure.

[0084] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0085] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an epitaxial structure, characterized in that: include: forming an epitaxial layer substrate, wherein the epitaxial layer substrate comprises a substrate and an interface reflection layer; forming an epitaxial layer on the epitaxial layer substrate; The epitaxial layer and the interface reflection layer have different refractive indices, and the substrate and the epitaxial layer are made of the same material; when the epitaxial layer is formed on the epitaxial layer substrate, the method further includes: using an optical method to monitor the thickness of the epitaxial layer in real time.

2. The method for preparing an epitaxial structure according to claim 1, characterized in that: The forming of the epitaxial layer substrate comprises: providing the substrate; forming the interface reflection layer on one side of the substrate; The step of forming an epitaxial layer on the epitaxial layer substrate comprises: The epitaxial layer is formed on the other side of the substrate.

3. The method for preparing an epitaxial structure according to claim 2, characterized in that: After forming the epitaxial layer on the epitaxial layer substrate, the method further comprises: The interface reflective layer is removed.

4. The method for preparing an epitaxial structure according to claim 1, characterized in that: The forming of the epitaxial layer substrate comprises: providing the substrate; forming the interface reflection layer on the substrate; The forming of an epitaxial layer on the epitaxial layer substrate comprises: The epitaxial layer is formed on the interface reflection layer, wherein the lattice constant of the interface reflection layer matches that of the epitaxial layer.

5. The method for preparing an epitaxial structure according to claim 4, characterized in that: The material of the interface reflection layer is InAlN, wherein the In component ranges from 15% to 19%.

6. The method for preparing an epitaxial structure according to claim 4, characterized in that: The thickness of the interface reflection layer ranges from 10 nm to 100 nm.

7. The method for preparing an epitaxial structure according to claim 1, characterized in that: The substrate and the epitaxial layer are made of gallium nitride.

8. An epitaxial structure, characterized in that: The epitaxial structure comprises: An epitaxial layer substrate, the epitaxial layer substrate comprising a substrate and an interface reflection layer; The epitaxial layer is arranged on the epitaxial layer substrate; wherein the epitaxial layer and the substrate are made of the same material; the epitaxial layer and the interface reflection layer have different refractive indices and lattice constants.

9. The epitaxial structure according to claim 8, characterized in that: The material of the interface reflection layer is InAlN, wherein the In component ranges from 15% to 19%.

10. A method for monitoring the thickness of an epitaxial layer of an epitaxial structure, characterized in that: The epitaxial structure comprises an epitaxial layer substrate and an epitaxial layer, wherein the epitaxial layer substrate comprises a substrate and an interface reflection layer; the epitaxial layer and the interface reflection layer have different refractive indices, and the substrate and the epitaxial layer are made of the same material; The method for monitoring the thickness of the epitaxial layer comprises: when the epitaxial layer is formed on the epitaxial layer substrate, using an optical method to monitor the thickness of the epitaxial layer in real time.

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