Composite capacitor and method for manufacturing the same

Abstract

The application discloses a composite capacitor and a preparation method thereof. The composite capacitor comprises a substrate, an epitaxial structure arranged on the substrate, the epitaxial structure being formed with a two-dimensional electron gas, and a metal capacitor structure arranged on a side of the epitaxial structure away from the substrate, the metal capacitor structure comprising a first metal plate and a second metal plate, the second metal plate being located on a side of the first metal plate away from the substrate, and the first metal plate being insulated from the two-dimensional electron gas, and along a thickness direction of the composite capacitor, a total projection of the first metal plate and the second metal plate on the substrate at least partially overlaps with a projection of the two-dimensional electron gas on the substrate. The application can increase the integration of the capacitor in the composite capacitor.

Description

Technical Field

[0001] This invention relates to capacitor technology, and more particularly to a composite capacitor and its preparation method. Background Technology

[0002] On-chip composite capacitors are one of the main components of modern RF / MM circuits and have important applications in modern electronic technology.

[0003] However, with the trend of miniaturization in electronic devices, the requirements for capacitor integration are becoming increasingly higher. The low integration of existing capacitors limits their application. Summary of the Invention

[0004] This invention provides a composite capacitor and its fabrication method to increase the integration density of the capacitor without increasing the wafer area.

[0005] In a first aspect, embodiments of the present invention provide a composite capacitor, the composite capacitor comprising:

[0006] Substrate; epitaxial structure disposed on the substrate, wherein a two-dimensional electron gas is formed on the epitaxial structure;

[0007] A metal capacitor structure is disposed on the side of the epitaxial structure away from the substrate. The metal capacitor structure includes a first metal plate and a second metal plate. The second metal plate is located on the side of the first metal plate away from the substrate, and the first metal plate is insulated from the two-dimensional electron gas.

[0008] Along the thickness direction of the composite capacitor, the total projection of the first metal plate and the second metal plate onto the substrate at least partially overlaps with the projection of the two-dimensional electron gas onto the substrate.

[0009] Optionally, the two-dimensional electron gas is configured to be at the same potential as the second metal electrode;

[0010] Along the thickness direction of the composite capacitor, the projection of the first metal plate on the substrate at least partially overlaps with the projection of the two-dimensional electron gas on the substrate.

[0011] Optionally, the composite capacitor further includes a connection structure;

[0012] The connection structure is in ohmic contact with the two-dimensional electron gas and is electrically connected to the second metal electrode plate.

[0013] Optionally, the composite capacitor further includes:

[0014] A first interlayer dielectric layer covers the epitaxial structure;

[0015] The metal capacitor structure is disposed on the side of the first interlayer dielectric layer away from the substrate, and the metal capacitor structure includes the first metal electrode, the second metal electrode, and the second interlayer dielectric layer.

[0016] Optionally, the epitaxial structure is a semiconductor material based on a III-V compound.

[0017] Optionally, along the thickness direction of the composite capacitor, the projection of the two-dimensional electron gas onto the substrate overlaps the projection of the first metal electrode onto the substrate and the projection of the second metal electrode onto the substrate.

[0018] Optionally, the epitaxial structure is formed with an isolation portion that defines a region corresponding to the two-dimensional electron gas.

[0019] Optionally, the two-dimensional electron gas is insulated from the second metal electrode.

[0020] Secondly, embodiments of the present invention also provide a method for preparing a composite capacitor, the method comprising:

[0021] An epitaxial structure is formed on a substrate, wherein a two-dimensional electron gas is formed in the epitaxial structure;

[0022] A metal capacitor structure is formed on the side of the epitaxial structure away from the substrate. The metal capacitor structure includes a first metal plate and a second metal plate. The second metal plate is located on the side of the first metal plate away from the substrate, and the first metal plate is insulated from the two-dimensional electron gas.

[0023] Along the thickness direction of the composite capacitor, the total projection of the first metal plate and the second metal plate onto the substrate at least partially overlaps with the projection of the two-dimensional electron gas onto the substrate.

[0024] Optionally, forming a metal capacitor structure on the side of the epitaxial structure away from the substrate includes:

[0025] The first metal electrode is formed such that, along the thickness direction of the composite capacitor, the projection of the first metal electrode on the substrate at least partially overlaps with the projection of the two-dimensional electron gas on the substrate.

[0026] The step of forming a metal capacitor structure on the side of the epitaxial structure away from the substrate further includes: forming a connection structure, the connection structure being in ohmic contact with the two-dimensional electron gas and electrically connected to the second metal electrode.

[0027] The technical solution of this embodiment employs a composite capacitor comprising: a substrate; an epitaxial structure disposed on the substrate, wherein a two-dimensional electron gas is formed on the epitaxial structure; and a metal capacitor structure disposed on the side of the epitaxial structure away from the substrate, the metal capacitor structure comprising a first metal plate and a second metal plate, the second metal plate being located on the side of the first metal plate away from the substrate, and the first metal plate being insulated from the two-dimensional electron gas; along the thickness direction of the composite capacitor, the total projection of the first metal plate and the second metal plate onto the substrate at least partially overlaps with the projection of the two-dimensional electron gas onto the substrate. The two-dimensional electron gas can be equivalent to one plate of the capacitor. This embodiment can increase the number of capacitors and increase the integration density of the capacitor without increasing the occupied wafer area. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a composite capacitor provided in an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of another composite capacitor provided in an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of another composite capacitor provided in an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of another composite capacitor provided in an embodiment of the present invention;

[0032] Figure 5 A flowchart illustrating a method for preparing a composite capacitor according to an embodiment of the present invention;

[0033] Figures 6 to 31 This is a schematic diagram of the product structure corresponding to the main process of the composite capacitor preparation method provided in the embodiments of the present invention. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0035] Figure 1 This is a schematic diagram of a composite capacitor provided in an embodiment of the present invention, with reference to... Figure 1The composite capacitor includes: a substrate 11; an epitaxial structure 12 disposed on the substrate 11, the epitaxial structure 12 forming a two-dimensional electron gas 121; a first interlayer dielectric layer 13 covering the epitaxial structure 12; and a metal capacitor structure 14 disposed on the side of the epitaxial structure 12 away from the substrate 11, the metal capacitor structure 13 including a first metal plate 141 and a second metal plate 143, the second metal plate 143 being located on the side of the first metal plate 141 away from the substrate 11, and the first metal plate 141 being insulated from the two-dimensional electron gas 121; along the thickness direction X of the composite capacitor, the total projection of the first metal plate 141 and the second metal plate 143 on the substrate 11 at least partially overlaps with the projection of the two-dimensional electron gas 121 on the substrate 11.

[0036] Specifically, the substrate 11 can be, for example, one or more of gallium nitride, aluminum gallium nitride, indium gallium nitride, aluminum indium gallium nitride, indium phosphide, gallium arsenide, silicon carbide, diamond, sapphire, germanium, and silicon, or any other material capable of growing group III nitrides. The epitaxial structure 12 can be formed by growing on the substrate 11, and the growth method can be, for example, any of metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and hydride vapor phase epitaxy (HVPE). The epitaxial structure 12 can include multiple layers, and each layer can be a semiconductor material based on group III-V compounds. The epitaxial structure 12 can be, for example, a heterojunction. This embodiment does not specifically limit this. After the epitaxial structure 12 is grown, a layer of high-concentration free charge (Two Dimensional Electron Gas, 2DEG) will be formed inside it, that is, a two-dimensional electron gas 121 will be formed. The surface density of the two-dimensional electron gas 121 is usually greater than 1e 13 / cm 2 Its resistivity is low, and the resistivity of the two-dimensional electron gas 121 can be considered similar to that of a metal; that is, the two-dimensional electron gas 121 can be equivalent to the metal plates of a capacitor. Figure 1As shown, since the first metal electrode 141 and the second metal electrode 143 need to have electrodes led out separately, the projection of the first metal electrode 141 on the substrate 11 and the projection of the second metal electrode 143 on the substrate 11 can be configured not to completely overlap. That is, the total projection of the first metal electrode 141 and the second metal electrode 143 on the substrate 11 is located in three regions on the substrate 11. The projection in the first region 111 only includes the projection of the first metal electrode 141, the projection in the second region 112 includes both the projection of the first metal electrode 141 and the projection of the second metal electrode 143, and the projection in the third region 113 only includes the projection of the second metal electrode 141. The projection of the two-dimensional electron gas 121 on the substrate 11 is located in the first region 111 and / or the second region 112, and the two-dimensional electron gas 121 and the first metal plate 141 form a capacitor; when the projection of the two-dimensional electron gas 121 on the substrate 11 is located in the third region 113 and is not connected to the second metal plate 143, the two-dimensional electron gas 121 and the second metal plate 143 form a capacitor. The two-dimensional electron gas 121 is disposed in the thickness direction of the metal capacitor structure 14 and does not increase the area occupied on the wafer. Therefore, this embodiment can increase the number of capacitors and increase the integration of capacitors without increasing the occupied wafer area.

[0037] The technical solution of this embodiment employs a composite capacitor comprising: a substrate; an epitaxial structure disposed on the substrate, wherein a two-dimensional electron gas is formed on the epitaxial structure; and a metal capacitor structure disposed on the side of the epitaxial structure away from the substrate, the metal capacitor structure comprising a first metal plate and a second metal plate, the second metal plate being located on the side of the first metal plate away from the substrate, and the first metal plate being insulated from the two-dimensional electron gas; along the thickness direction of the composite capacitor, the total projection of the first metal plate and the second metal plate onto the substrate at least partially overlaps with the projection of the two-dimensional electron gas onto the substrate. The two-dimensional electron gas can be equivalent to one plate of the capacitor. This embodiment can increase the number of capacitors and increase the integration density of the capacitor without increasing the occupied wafer area.

[0038] Optionally, continue to refer to Figure 1 The epitaxial structure 12 has an isolation portion 122, which defines the region corresponding to the two-dimensional electron gas 121.

[0039] Specifically, in this embodiment, the portion of the epitaxial structure other than the portion that needs to retain the two-dimensional electron gas 121 can be configured to form an isolation portion 122. For example, along the thickness direction of the composite capacitor, the projection of the first metal plate 141 on the substrate and the projection of the second metal plate 143 on the substrate 11 can be superimposed and completely overlap with the projection of the two-dimensional electron gas 121 on the substrate 11, while the other portions of the epitaxial structure 12 form the isolation portion 122. The isolation portion 122 can be formed, for example, by ion implantation, such as implanting argon ions, thereby making the resistance of the isolation portion 122 extremely high, thereby reducing substrate loss.

[0040] Optionally, continue to refer to Figure 1 The composite capacitor also includes a protective layer 17 covering the second metal plate 143.

[0041] Specifically, the protective layer 17 can be one or more of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, or any other material that can serve as an insulating medium. The protective layer 17 can protect the composite capacitor from corrosion by external water, oxygen, etc., thereby improving the service life of the composite capacitor.

[0042] Optionally, such as Figure 1As shown, the two-dimensional electron gas 121 is insulated from the second metal plate 143. In this embodiment, the two-dimensional electron gas 121 can form a capacitor with the metal plate whose projection overlaps with it. Preferably, the projection of the two-dimensional electron gas 121 on the substrate 11 can be located in the first region 111 and / or the second region 112, but not in the third region 113. In this case, the first metal plate 141 and the two-dimensional electron gas 121 form a capacitor. Since the first metal plate 141 is closer to the two-dimensional electron gas 121 than the second metal plate 143, the performance of this capacitor is better. In addition, the first metal plate 141 and the second metal plate 143 form a capacitor. The composite capacitor contains two capacitors, and the capacitor integration is high. The two-dimensional electron gas 121 can be electrically connected to an external circuit by setting an electrode that makes ohmic contact with it. The position of the electrode is not specifically limited. For example, it can be set on the side of the two-dimensional electron gas 121 away from the substrate 11, or it can be set on the side of the two-dimensional electron gas 121 closer to the substrate 11. In some embodiments, if the projection of the two-dimensional electron gas 121 on the substrate 11 is located in the third region 113, and is not present in either the first region 111 or the second region 112, then the two-dimensional electron gas 121 and the second metal electrode 143 form a capacitor, and the composite capacitor still includes two capacitors. In other embodiments, if the projection of the two-dimensional electron gas 121 on the substrate 11 is located in both the third region 113 and at least one of the first region 111 and the second region 112, then the two-dimensional electron gas 121 and the first metal electrode 141 form a capacitor, and the two-dimensional electron gas 121 and the second metal electrode 143 also form a capacitor, and the composite capacitor includes three capacitors, further increasing the integration density of the capacitor. In this case, it is preferable that the projection of the two-dimensional electron gas 121 on the substrate 11 covers the projections of the first metal electrode 141 and the second metal electrode 143 on the substrate 11. The capacitance values ​​of the two capacitors formed by the two-dimensional electron gas 121 in the composite capacitor are both large, and the capacitance density of the composite capacitor is also large.

[0043] Optionally, the two-dimensional electron gas 121 is configured to be at the same potential as the second metal electrode 143; along the thickness direction of the composite capacitor, the projection of the first metal electrode 141 on the substrate 11 at least partially overlaps with the projection of the two-dimensional electron gas 121 on the substrate 11. With this configuration, the two-dimensional electron gas 121 and the second metal electrode 143 are essentially a single electrode, overlapping with two surfaces of the first metal electrode 141 respectively. This improves the integration density of the capacitor and effectively increases the capacitance value of the composite capacitor, thereby increasing the capacitance density.

[0044] For example, Figure 2This is a schematic diagram of another composite capacitor provided in an embodiment of the present invention. In this embodiment, the composite capacitor further includes a connection structure 15, which is in ohmic contact with the two-dimensional electron gas 121 and electrically connected to the second metal plate 143. The connection structure 15 forms an ohmic contact with the two-dimensional electron gas 121, resulting in extremely low contact resistance, thus allowing charge to be introduced from the two-dimensional electron gas 121 into the connection structure 15. The connection structure 15 is electrically connected to the second metal plate 143 and insulated from the first metal plate 141. Since the projection of the two-dimensional electron gas 121 onto the substrate 11 overlaps with the projection of the first metal plate 141 onto the substrate 11 along the thickness direction X of the composite capacitor, and the two-dimensional electron gas 121 is insulated from the first metal plate 141, the two-dimensional electron gas 121 and the first metal plate 141 form a capacitor. The capacitor is designated as capacitor C1; the metal capacitor structure 14 is designated as capacitor C2. Capacitor C2 and capacitor C1 share a common electrode (first metal electrode 141, which has movable charges on both its upper and lower surfaces when the composite capacitor is working). The non-shared electrodes of capacitors C1 and C2 (two-dimensional electron gas 121 and second metal electrode 143) are electrically connected through connection structure 15, which is equivalent to capacitors C1 and C2 being connected in parallel. That is, the capacitance value of the composite capacitor is equal to the sum of the capacitance values ​​of capacitors C1 and C2, which is equivalent to increasing the area of ​​the capacitor electrodes facing each other. Since the two-dimensional electron gas 121 is located in the thickness direction of the metal capacitor structure 14, it does not increase the area occupied on the wafer. Therefore, this embodiment can increase the capacitance value of the composite capacitor without increasing the occupied wafer area. Furthermore, since fewer metal layers are required, the manufacturing difficulty and cost can be reduced.

[0045] Of course, in other embodiments, other methods can be used to achieve equipotentiality between the two-dimensional electron gas 121 and the second metal plate 143. For example, the two-dimensional electron gas 121 and the second metal plate 143 can be electrically connected outside the composite capacitor.

[0046] Optionally, such as Figure 1 and Figure 2 As shown, the composite capacitor also includes a first interlayer dielectric layer 13, which covers the epitaxial structure 12. The metal capacitor structure 14 includes a first metal plate 141, a second metal plate 143, and a second interlayer dielectric layer 142, which is disposed between the first metal plate 141 and the second metal plate 143. By providing the first interlayer dielectric layer 141 and the second interlayer dielectric layer 142, the performance of the capacitor can be enhanced. The metal capacitor structure 14 is a MIM capacitor in this case.

[0047] Optionally, continue to refer to Figure 2Along the thickness direction X of the composite capacitor, the projection of the two-dimensional electron gas 121 on the substrate 11 covers the projection of the first metal plate 141 on the substrate 11 and the projection of the second metal plate 143 on the substrate 11.

[0048] Specifically, the larger the overlapping area of ​​the two-dimensional electron gas 121 and the first metal electrode 141, the larger the capacitance value of capacitor C1. Therefore, along the thickness direction X of the composite capacitor, the projection of the two-dimensional electron gas 121 on the substrate 11 can cover the projection of the first metal electrode 141 on the substrate 11, thereby increasing the capacitance value of capacitor C1 to a greater extent. In the metal capacitor structure 14, since the lead-out electrodes of the MIM capacitor need to be set, along the thickness direction X of the composite capacitor, the projection of the second metal electrode 143 on the substrate 11 and the orthogonal projection of the first metal electrode 143 on the substrate 11 will not completely overlap. Therefore, along the thickness direction X of the composite capacitor, the projection of the two-dimensional electron gas 121 on the substrate 11 can cover the orthogonal projection of the second metal electrode 143 on the substrate 11, thereby facilitating the setting of the connection structure 15.

[0049] It should be noted that, as Figure 1 and Figure 2 As shown, the composite capacitor may further include a first electrode 16, which is located on the side of the first metal plate 141 away from the substrate 11 and is electrically connected to the first metal plate 141; the portion of the connection structure 15 that penetrates the second interlayer dielectric layer 142 can serve as the second electrode of the composite capacitor.

[0050] For example, such as Figure 2 As shown, the connection structure 15 includes a connection metal layer 151 and a connection metallized via; the connection metal layer 151 is in contact with the surface of the two-dimensional electron gas; the connection metallized via penetrates the first interlayer dielectric layer 13 and the second interlayer dielectric layer 142 and is electrically connected to the connection metal layer 151 and the second metal electrode 143.

[0051] Specifically, in this embodiment, the connecting metal layer 151 is in direct ohmic contact with the two-dimensional electron gas 121. When fabricating the composite capacitor, the connecting metal layer 151 can be fabricated directly after the epitaxial structure 12 is formed. This results in better contact performance between the connecting metal layer 151 and the two-dimensional electron gas 121, which is more conducive to improving the performance of the composite capacitor. The first via penetrates the first interlayer dielectric layer 13, and the second via penetrates the second interlayer dielectric layer 142. The connecting metallized via includes a first sub-via 153 and a second sub-via 154, where the first sub-via 153 is the metallized first via 153, and the second sub-via 154 is the metallized second via 154. The connecting metal layer 151 can be formed, for example, by first depositing a composite metal using an electron beam evaporation system, and then using a rapid thermal annealing (RTA) process. The connecting metallized via can be formed by first etching to create the via, and then metallizing the via.

[0052] In some other implementations, such as Figure 3 As shown, Figure 3 This is a schematic diagram of another composite capacitor provided in an embodiment of the present invention, and... Figure 2 The connection structure 15 in this embodiment differs from the one shown in the previous one in that it includes a connection metal layer 151, an ohmic metallized via 152, and a connection metallized via. The connection metal layer 151 is disposed in the same layer as the first metal electrode 141. The connection metal layer 151 is in ohmic contact with the two-dimensional electron gas 121 through the ohmic metallized via 152 that penetrates the first interlayer dielectric layer 13. The connection metallized via penetrates the second interlayer dielectric layer 142 and is electrically connected to the connection metal layer 151 and the second metal electrode 143.

[0053] Specifically, in this embodiment, the connecting metal layer 151 and the first metal electrode 141 are disposed in the same layer. After the epitaxial structure 12 is formed, the first interlayer dielectric layer 13 can be grown first, and then through holes can be etched on the first interlayer dielectric layer 13. Then, the connecting metal layer 151 and the ohmic metallized through hole 152 are simultaneously fabricated using the ohmic metallization process. The fourth through hole penetrates the second interlayer dielectric layer 142, and the connecting metallized through hole only includes the second sub-through hole 154. In this embodiment, the second sub-through hole 154 is the metallized fourth through hole.

[0054] In some other implementations, such as Figure 4 As shown, Figure 4 This is a schematic diagram of another composite capacitor provided in an embodiment of the present invention, and... Figure 2 and Figure 3 The difference from the structure shown is that the connection structure 15 in this embodiment includes a connection metal layer 151, an ohmic metallized via 152, and a connection metallized via; the first interlayer dielectric layer 13 includes a first sub-dielectric layer 131 and a second sub-dielectric layer 132 stacked on the epitaxial structure 12; the connection metal layer 151 is disposed on the surface of the first sub-dielectric layer 131 away from the epitaxial structure 12, and is in ohmic contact with the two-dimensional electron gas 121 through the ohmic metallized via 152 penetrating the first sub-dielectric layer 131; the connection metallized via penetrates the second interlayer dielectric layer 142 and the second sub-dielectric layer 132 and is electrically connected to the connection metal layer 151 and the second metal electrode 143.

[0055] Specifically, in this embodiment, the first interlayer dielectric layer 13 includes a first sub-dielectric layer 131 and a second sub-dielectric layer 132. The material of the first sub-dielectric layer 131 can be one or more of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, or any other material that can serve as an insulating medium. The second sub-dielectric layer 132 can be one or more of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, or any other material that can serve as an insulating medium. The composite capacitor can be fabricated on the same wafer as other thin-film devices, such as thin-film transistors. By placing the connecting metal layer 151 on the first sub-dielectric layer 131, it can be compatible with other devices on the wafer, thereby improving the compatibility of the composite capacitor fabrication process. The sixth via penetrates the second sub-dielectric layer 132, and the seventh via penetrates the second interlayer dielectric layer 142. The connecting metallized vias include a first sub-via 153 and a second sub-via 154. In this embodiment, the first sub-via 153 is the metallized sixth via, and the second sub-via 154 is the metallized seventh via.

[0056] This invention also provides a method for preparing a composite capacitor, such as... Figure 5 As shown, Figure 5 This is a flowchart illustrating a method for preparing a composite capacitor according to an embodiment of the present invention. The method includes:

[0057] Step S301: An epitaxial structure is formed on the substrate, and a two-dimensional electron gas is formed in the epitaxial structure;

[0058] Specifically, Figures 6 to 31 A schematic diagram of the product structure corresponding to the main process of the composite capacitor preparation method provided in the embodiments of the present invention is shown below. Figure 6 As shown, a substrate 11 can be provided first. The substrate 11 can be one or more of gallium nitride, aluminum gallium nitride, indium gallium nitride, aluminum indium gallium nitride, indium phosphide, gallium arsenide, silicon carbide, diamond, sapphire, germanium, and silicon, or any other material capable of growing group III nitrides; subsequently, as... Figure 7 As shown, an epitaxial structure 12 is epitaxially formed on substrate 11. The growth method can be, for example, any one of metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or hydride vapor phase epitaxy (HVPE). The epitaxial structure 12 can include multiple layers, each of which can be a semiconductor material based on a III-V compound. The epitaxial structure 12 can be, for example, a heterojunction. After the epitaxial structure 12 is formed, a two-dimensional electron gas 121 will be formed inside it. The two-dimensional electron gas 121 can be used to form one electrode of a capacitor; subsequently... Figure 8As shown, in order to reduce substrate loss, the portion of the epitaxial structure that needs to retain the two-dimensional electron gas 121 can be formed into an isolation portion 122. The isolation portion 122 can be formed, for example, by ion implantation, such as implanting argon ions, thereby making the resistance of the isolation portion 122 extremely high, thereby reducing substrate loss.

[0059] Step S302: A metal capacitor structure is formed on the side of the epitaxial structure away from the substrate. The metal capacitor structure includes a first metal plate and a second metal plate. The second metal plate is located on the side of the first metal plate away from the substrate, and the first metal plate is insulated from the two-dimensional electron gas. Along the thickness direction of the composite capacitor, the total projection of the first metal plate and the second metal plate on the substrate at least partially overlaps with the projection of the two-dimensional electron gas on the substrate.

[0060] The composite capacitor prepared by the method of this embodiment forms a capacitor with a two-dimensional electron gas and a first metal plate and / or a second metal plate. The two-dimensional electron gas is disposed in the stacking direction of the first metal plate and the second metal plate. Therefore, the number of capacitors in the composite capacitor can be increased without increasing the wafer area occupied by the composite capacitor, thereby improving the integration of the capacitor.

[0061] Optionally, forming a metal capacitor structure on the side of the epitaxial structure away from the substrate includes:

[0062] The process further includes forming a first metal electrode plate such that the projection of the first metal electrode plate onto the substrate along the thickness direction of the composite capacitor at least partially overlaps with the projection of the two-dimensional electron gas onto the substrate; when forming the metal capacitor structure on the side of the epitaxial structure away from the substrate, the process further includes forming a connection structure, the connection structure being in ohmic contact with the two-dimensional electron gas and electrically connected to the second metal electrode plate.

[0063] For example, a first interlayer dielectric layer may also be formed when forming the metal capacitor structure; wherein the first interlayer dielectric layer covers the epitaxial structure; the metal capacitor structure is disposed on the side of the first interlayer dielectric layer away from the substrate, and the metal capacitor structure includes a first metal plate, a second metal plate, and a second interlayer dielectric layer, wherein the second metal plate is located on the side of the first metal plate away from the substrate. The connection structure includes a connecting metal layer and a connecting metallized via; forming the first interlayer dielectric layer, the metal capacitor structure, and the connection structure includes:

[0064] like Figure 9 As shown, a connecting metal layer 151 is formed on the surface of the epitaxial structure 12 away from the substrate 11; specifically, this can be achieved by first depositing a composite metal using an electron beam evaporation system, followed by a rapid thermal annealing (RTA) process to form the connecting metal layer; subsequently, as shown... Figure 10As shown, a dielectric layer material is first grown. This dielectric layer material can be, for example, one or more combinations of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, or any other material capable of serving as an insulating dielectric; then, as... Figure 11 As shown, a first via 201 is formed by exposure, development, and etching, exposing the connecting metal layer 151; then as... Figure 12 As shown, a first metal electrode 141 is formed on the surface of the first interlayer dielectric layer 13 away from the substrate, and a first through-hole is metallized. This can be achieved, for example, by sputtering or deposition. The first metal electrode 141 is formed using a mask, and the first through-hole is simultaneously metallized to form a first sub-through-hole 153. Then, as... Figure 13 As shown, the entire surface is covered with a dielectric layer material 1420. This dielectric layer material 1420 can be one or more combinations of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, or any other material that can serve as an insulating dielectric, acting as an isolation layer for the metal capacitor structure; then as... Figure 14 As shown, a second via 202 is formed through exposure, development, etching, and other methods, exposing the first via 202. Additionally, an electrode via 301 can be formed simultaneously, which can be used to subsequently form a metal electrode, thereby forming... Figure 14 The second interlayer dielectric layer 142; then as follows Figure 15 As shown, it can be fabricated using sputtering, deposition, or other methods, and a second metal electrode 143 is formed using a mask. Simultaneously, the second through-hole 202 and electrode through-hole 301 are metallized to form a second sub-through-hole 154, a second metal electrode 143, an electrode metal through-hole 161, and an electrode 162. The electrode metal through-hole 161 and the electrode 162 constitute the first electrode of the composite capacitor, and the portion of the connecting structure 15 penetrating the second interlayer dielectric layer 142 can serve as the second electrode of the composite capacitor. Finally, as... Figure 2 As shown, a protective layer 17 is then applied to the entire surface to form... Figure 2 The protective layer 17 in the structure shown can be, for example, one or more combinations of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, or any other material that can serve as an insulating medium. The protective layer 17 protects the composite capacitor from corrosion by external water, oxygen, etc., thereby improving the lifespan of the composite capacitor.

[0065] Optionally, unlike the above-described preparation method, the connection structure in this embodiment includes a connection metal layer, an ohmic metallized via, and a connection metallized via; forming the first interlayer dielectric layer, the metal capacitor structure, and the connection structure includes:

[0066] like Figure 16 As shown, in the formation Figure 8After the structure shown, a first interlayer dielectric layer material 1301 can be deposited on the epitaxial structure 12. The material of the first interlayer dielectric layer can be, for example, one or more combinations of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, or any other material that can serve as an insulating dielectric; then as shown... Figure 17 As shown, a third via 203 is formed through methods such as exposure, development, and etching, exposing the area corresponding to the connecting metal layer; then as... Figure 18 As shown, a connecting metal layer 151 is formed on the surface of the first interlayer dielectric layer 13 away from the substrate, and a third via is metallized to form an ohmic metallized via 152. The connecting metal layer 151 is in ohmic contact with the two-dimensional electron gas 121 through the ohmic metallized via 152. The connecting metal layer 151 and the ohmic metallized via 152 are simultaneously fabricated using the ohmic metal fabrication process. The ohmic metal fabrication process can be to first deposit a composite metal using an electron beam evaporation system, and then use a rapid thermal annealing process to form the ohmic metal; then as follows... Figure 19 As shown, since the fabrication of the connecting metal layer requires a high-temperature process, the connecting metal layer can be fabricated first, followed by the fabrication of the first metal electrode 161. The first metal electrode 161 can be fabricated using methods such as sputtering or deposition. Alternatively, if only a single layer of metal can be fabricated first, to prevent electrical connection between the first metal electrode and the connecting metal layer, a sacrificial layer can be fabricated on the connecting metal layer before depositing the entire metal layer. After etching the metal layer to form the first metal electrode 141, the sacrificial layer is then etched away, thereby forming... Figure 19 The structure shown is such that the first metal electrode 141 and the connecting metal layer 151 are on the same layer; subsequently as... Figure 20 As shown, the entire surface is covered with a dielectric layer material 1420. This dielectric layer material 1420 can be one or more combinations of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, or any other material that can serve as an insulating dielectric, acting as an isolation layer for the metal capacitor structure; then as... Figure 21 As shown, a fourth via 204 is formed through exposure, development, etching, and other methods, exposing the connecting metal layer 151. Additionally, an electrode via 301 can be formed simultaneously, which can be used to subsequently form a metal electrode, thereby forming... Figure 20 The second interlayer dielectric layer 142; then as follows Figure 22 As shown, it can be fabricated using sputtering, deposition, or other methods, and a second metal electrode plate 143 is formed using a mask. Simultaneously, the fourth through-hole 204 and the electrode through-hole 301 are metallized to form a second sub-through-hole 154, the second metal electrode plate 143, the electrode metal through-hole 161, and the electrode 162. Finally, as... Figure 2 As shown, a protective layer 17 is then applied to the entire surface to form... Figure 3The protective layer 17 in the structure shown can be, for example, one or more combinations of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, or any other material that can serve as an insulating medium. The protective layer 17 protects the composite capacitor from corrosion by external water, oxygen, etc., thereby improving the lifespan of the composite capacitor.

[0067] Optionally, unlike the above-described preparation method, the connection structure in this embodiment includes a connection metal layer, an ohmic metallized via, and a connection metallized via; the first interlayer dielectric layer includes a first sub-dielectric layer and a second sub-dielectric layer; forming the first interlayer dielectric layer, the metal capacitor structure, and the connection structure includes:

[0068] like Figure 23 As shown, in the formation Figure 8 After the structure shown, a first sub-dielectric layer material 1310 can be deposited on the epitaxial structure 12. The first sub-dielectric layer material 1310 can be, for example, one or more combinations of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, or any other material that can serve as an insulating dielectric; then as shown... Figure 23 As shown, a fifth via 205 is formed through methods such as exposure, development, and etching, exposing the area corresponding to the connecting metal layer; then as... Figure 25 As shown, a connecting metal layer 151 is formed on the surface of the first sub-dielectric layer 131 away from the substrate, and a fifth via is metallized to form an ohmic metallized via 152. The connecting metal layer 151 is in ohmic contact with the two-dimensional electron gas 121 through the ohmic metallized via 152. The connecting metal layer 151 and the ohmic metallized via 152 are simultaneously fabricated using the ohmic metal fabrication process. The ohmic metal fabrication process can be to first deposit a composite metal using an electron beam evaporation system, and then use a rapid thermal annealing process to form the ohmic metal; then as follows... Figure 26 As shown, the material 1320 forming the second sub-dielectric layer is then fully covered. The material of the second sub-dielectric layer can be, for example, one or more combinations of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, or any other material capable of serving as an insulating dielectric; then as... Figure 27 As shown, a sixth via 206 is formed through methods such as exposure, development, and etching, exposing the connecting metal layer 151; then as... Figure 28 As shown, a first metal electrode 141 is formed on the surface of the second sub-dielectric layer 132 away from the substrate, and a sixth via is metallized. This can be achieved, for example, by sputtering or deposition. The first metal electrode 141 is formed using a mask, and the sixth via is simultaneously metallized to form a first sub-via 153; then... Figure 29As shown, the entire surface is covered with a dielectric layer material 1420. This dielectric layer material 1420 can be one or more combinations of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, or any other material that can serve as an insulating dielectric, acting as an isolation layer for the metal capacitor structure; then as... Figure 30 As shown, a seventh through-hole 207 is formed through exposure, development, etching, and other methods, exposing the sixth through-hole. Additionally, an electrode through-hole 301 can be formed simultaneously, which can be used to subsequently form a metal electrode, thereby forming... Figure 13 The second interlayer dielectric layer 142; then as follows Figure 31 As shown, it can be fabricated using sputtering, deposition, or other methods, and a second metal electrode plate 143 is formed using a mask. Simultaneously, the seventh through-hole 207 and electrode through-hole 301 are metallized to form a second sub-through-hole 154, the second metal electrode plate 143, the electrode metal through-hole 161, and the electrode 162. Finally, as... Figure 4 As shown, a protective layer 17 is then applied to the entire surface to form... Figure 3 The protective layer 17 in the structure shown can be, for example, one or more combinations of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, or any other material that can serve as an insulating medium. The protective layer 17 protects the composite capacitor from corrosion by external water, oxygen, etc., thereby improving the lifespan of the composite capacitor.

[0069] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A composite capacitor, characterized in that, The composite capacitor includes: Substrate; epitaxial structure disposed on the substrate, wherein a two-dimensional electron gas is formed on the epitaxial structure; A metal capacitor structure is disposed on the side of the epitaxial structure away from the substrate. The metal capacitor structure includes a first metal plate and a second metal plate. The second metal plate is located on the side of the first metal plate away from the substrate, and the first metal plate is insulated from the two-dimensional electron gas. Along the thickness direction of the composite capacitor, the total projection of the first metal plate and the second metal plate on the substrate at least partially overlaps with the projection of the two-dimensional electron gas on the substrate. The composite capacitor also includes a connection structure; The connection structure is in ohmic contact with the two-dimensional electron gas and is electrically connected to the second metal electrode plate.

2. The composite capacitor according to claim 1, characterized in that, The two-dimensional electron gas is configured to be at the same potential as the second metal electrode; Along the thickness direction of the composite capacitor, the projection of the first metal plate on the substrate at least partially overlaps with the projection of the two-dimensional electron gas on the substrate.

3. The composite capacitor according to claim 1, characterized in that, The composite capacitor also includes: A first interlayer dielectric layer covers the epitaxial structure; The metal capacitor structure is disposed on the side of the first interlayer dielectric layer away from the substrate, and the metal capacitor structure includes the first metal electrode, the second metal electrode, and the second interlayer dielectric layer.

4. The composite capacitor according to claim 1, characterized in that, The epitaxial structure is a semiconductor material based on a III-V compound.

5. The composite capacitor according to claim 1, characterized in that, Along the thickness direction of the composite capacitor, the projection of the two-dimensional electron gas onto the substrate covers the projection of the first metal electrode onto the substrate and the projection of the second metal electrode onto the substrate.

6. The composite capacitor according to claim 1, characterized in that, The epitaxial structure has an isolation portion that defines the region corresponding to the two-dimensional electron gas.

7. The composite capacitor according to claim 1, characterized in that, The two-dimensional electron gas is insulated from the second metal electrode.

8. A method for preparing a composite capacitor, used to prepare the composite capacitor as described in any one of claims 1-7, characterized in that, The preparation method includes: An epitaxial structure is formed on a substrate, wherein a two-dimensional electron gas is formed in the epitaxial structure; A metal capacitor structure is formed on the side of the epitaxial structure away from the substrate. The metal capacitor structure includes a first metal plate and a second metal plate. The second metal plate is located on the side of the first metal plate away from the substrate, and the first metal plate is insulated from the two-dimensional electron gas. Along the thickness direction of the composite capacitor, the total projection of the first metal plate and the second metal plate onto the substrate at least partially overlaps with the projection of the two-dimensional electron gas onto the substrate.

9. The method for preparing the composite capacitor according to claim 8, characterized in that, The formation of a metal capacitor structure on the side of the epitaxial structure away from the substrate includes: The first metal electrode is formed such that, along the thickness direction of the composite capacitor, the projection of the first metal electrode on the substrate at least partially overlaps with the projection of the two-dimensional electron gas on the substrate. The step of forming a metal capacitor structure on the side of the epitaxial structure away from the substrate further includes: forming a connection structure, the connection structure being in ohmic contact with the two-dimensional electron gas and electrically connected to the second metal electrode.

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