CN117316931B - Isolation capacitor and preparation method thereof - Google Patents

Abstract

The invention relates to the field of chip technology, and discloses an isolation capacitor and a preparation method of the isolation capacitor. The isolation capacitor includes: a lower plate provided on the base; a first insulating medium provided on the lower plate; and a metal layer provided in the first insulating medium, wherein the edge of the metal layer is Smooth curved surface structure, and the mating surface of the smooth curved surface structure and the metal layer is a tangential surface; and an upper electrode plate provided on the first insulating medium, wherein the upper electrode plate and the metal layer pass through a metal channel connected. The invention at least partially solves the problem of sharp corners and side discharge of the metal end of the upper plate of the isolation capacitor. At the same time, the high voltage and strong electric field of the upper plate are introduced into the silicon dioxide body to avoid the interface between different dielectric layers (easy breakdown). Point) breakdown causes device failure.

Description

Isolation capacitor and preparation method of isolation capacitor

Technical field

The present invention relates to the field of chip technology, and specifically relates to an isolation capacitor and a preparation method of the isolation capacitor.

Background technique

With the rapid development of integrated circuits, digital isolators are gradually being widely used in industrial fields such as smart grids, rail transit, and automotive electronics. However, digital isolators will inevitably work in high voltage and strong magnetic field environments for a long time in these industrial fields, so the life of the isolation capacitor is crucial. In order to solve the device life problem, the following three technologies are usually used to isolate the device: optocoupler isolation, magnetic isolation and capacitive isolation. Compared with traditional optocoupler isolation, capacitive isolation technology has obvious advantages in terms of power consumption, communication speed, circuit integration and service life. At the same time, capacitive isolation technology is well compatible with standard CMOS processes. It is quickly accepted by the market and occupies a certain position due to its characteristics of fast transmission rate, low cost, and high integration. Therefore, it has also attracted much attention in the power industry and has received a lot of research. , and then widely used in smart meters, power relay protection, power generation control and other scenarios.

Existing isolation capacitors usually include an upper plate, a lower plate, and a dielectric layer between the plates. The upper plate and the lower plate are made by metal target sputtering process, and the dielectric layer is silicon dioxide deposited by chemical vapor deposition method. However, the upper and lower plates of existing isolation capacitors are usually rectangular. When the upper plate is subjected to high voltage, tip discharge is inevitably formed at the metal end, where the current is conducted to the passivation layer through the top metal, causing the passivation layer to The silicon dioxide breaks down at the interface, as shown in Figure 17, which leads to device failure and life cannot be guaranteed. Figure 1 is a schematic diagram of an existing isolation capacitor.

Therefore, in order to solve the problem of discharge at the tip and side of the metal end of the plate on the device, it is urgent to propose a new isolation capacitor device and its preparation method.

Contents of the invention

The object of the present invention is to provide an isolation capacitor and a preparation method of the isolation capacitor, which at least partially solves the problem of sharp corners and side discharge of the metal ends of the upper plate of the isolation capacitor, and at the same time introduces the high voltage and strong electric field of the upper plate into the silicon dioxide body to avoid breakdown at the interface of different dielectric layers (easy breakdown points) causing device failure.

In order to achieve the above object, a first aspect of the present invention provides an isolation capacitor. The isolation capacitor includes: a lower plate provided on a substrate; a first insulating medium provided on the lower plate; A metal layer in an insulating medium, wherein the edge of the metal layer is a smooth curved surface structure, and the mating surface of the smooth curved surface structure and the metal layer is a tangential surface; and an upper electrode provided on the first insulating medium plate, wherein the upper plate is connected to the metal layer via a metal channel.

Preferably, the metal layer includes two metal regions that are symmetrical about a central axis, wherein the central axis is a line between the center of the upper plate and the center of the lower plate, and the metal region The edges are smooth curved structures.

Preferably, the distance from any point on the lower plate to any point on the smooth curved structure is greater than or equal to the thickness of the first insulating medium.

Preferably, the upper plate is connected to the smooth curved structure at the edge of the metal area through four metal channels.

Preferably, when the metal layer is a plurality of metal layers, any two adjacent metal layers are connected through a metal channel.

Preferably, in the case where the metal layer includes two metal regions that are symmetrical about the central axis, the upper metal region among the metal regions on the same side of any two adjacent metal layers is connected to the lower metal region through four metal channels. The edges of a metal area are connected by smooth curved structures.

Preferably, the number of the plurality of metal layers is determined by the thickness of the first insulating medium.

Preferably, the edge of the upper electrode plate and/or the lower electrode plate has a smooth curved surface structure, wherein the edge of the metal layer has a smooth curved surface structure, and the mating surface of the smooth curved surface structure and the metal layer is a tangent surface. .

Preferably, the material of the smooth curved surface structure is different from the materials of the upper electrode plate and the metal layer, and the material of the smooth curved surface structure is tungsten.

Preferably, the upper electrode plate, the lower electrode plate and the metal layer are all sandwich structures formed by Ti or TiN, metal and TiN.

Preferably, the outer layer of the metal channel is a Ti or TiN layer.

Preferably, the isolation capacitor further includes: a first insulating medium and a second insulating medium sequentially provided on the upper plate, wherein the dielectric constant of the first insulating medium is smaller than the dielectric constant of the second insulating medium. electrical constant.

Preferably, the smooth curved surface structure includes a cylindrical structure.

Through the above technical solution, the present invention creatively provides a first insulating medium on the lower plate, and a metal layer is provided in the first insulating medium, wherein the edge of the metal layer is a smooth curved surface structure, and the smooth The mating surface of the curved structure and the metal layer is a tangential surface, and an upper plate is provided on the first insulating medium, wherein the upper plate is connected to the metal layer through a metal channel, thereby at least partially solving the isolation problem The metal end sharp corners and side discharge problems of the upper plate of the capacitor. At the same time, the high voltage and strong electric field of the upper plate are introduced into the silicon dioxide body to avoid breakdown at the interface of different dielectric layers (easy breakdown points). Device failure problem.

A second aspect of the present invention provides a method for preparing an isolation capacitor. The preparation method includes: forming a lower plate on a substrate; forming a first insulating medium on the lower plate; and forming a first insulating medium inside the first insulating medium. Forming a metal layer, wherein the edge of the metal layer is a smooth curved surface structure, and the mating surface of the smooth curved surface structure and the metal layer is a tangent surface; and forming an upper plate on the first insulating medium, wherein the The upper electrode plate is connected to the metal layer through metal channels.

Preferably, forming a metal layer inside the first insulating medium; and forming an upper plate on the first insulating medium includes: forming a metal layer inside the first insulating medium, wherein the metal layer It includes two metal regions that are symmetrical about a central axis, and the central axis is a connection between the center of the upper plate and the center of the lower plate; from the upper surface of the first insulating medium downward Form four through holes connected to the four edges of the metal area, and fill the through holes with metal to form a smooth curved structure of metal channels and edges of the metal area; and on the first insulating medium An upper plate covering the metal channel is formed.

Preferably, four through holes connected to four edges of the metal area are formed downward from the upper surface of the first insulating medium, and metal is filled in the through holes to form metal channels and the metal The smooth curved surface structure at the edge of the area includes: using dry etching to form four vertical through holes downward from the upper surface of the first insulating medium, wherein the bottom of the vertical through holes is horizontal to the metal area The central axes are aligned and the distance from the center of the bottom of the vertical through hole to the corresponding edge of the metal area is smaller than the radius of the smooth curved structure; wet etching is used to form the bottom of the vertical through hole. The bottom center line of the vertical through hole is a cylindrical through hole, the radius of the cylindrical through hole is greater than the thickness of the metal area; and the vertical through hole and the cylindrical through hole are filled with metal .

Preferably, when the metal layer is a plurality of metal layers, a first insulating medium is formed on the lower plate; a metal layer is formed inside the first insulating medium; and Forming an upper plate on the dielectric includes: forming an insulating medium of a first thickness on the lower plate or a next metal layer; forming a first metal layer on the insulating medium of the first thickness, wherein the first The metal layer includes two metal regions that are symmetrical about a central axis, and the central axis is a connection between the center of the upper plate and the center of the lower plate; a third metal layer is formed on the first metal layer. An insulating medium of two thicknesses; forming four through holes connected to the four edges of the metal area downward from the upper surface of the insulating medium of the second thickness, and filling the through holes with metal to form metal channels and a smooth curved surface structure at the edge of the metal area; forming a second metal layer covering the metal channel on the insulating medium of the second thickness to form any two adjacent metal layers; and in the total area of each insulating medium When the thickness is equal to the thickness of the first insulating medium, an upper plate covering the metal channel is formed on the first insulating medium.

Preferably, the number of the plurality of metal layers is determined by the thickness of the first insulating medium.

Preferably, the distance from any point on the lower plate to any point on the smooth curved structure is greater than or equal to the thickness of the first insulating medium.

Preferably, four through holes connected to four edges of the metal area are formed downward from the upper surface of the insulating medium of the second thickness, and metal is filled in the through holes to form metal channels and the The smooth curved surface structure at the edge of the metal area includes: using dry etching to form four vertical through holes downward from the upper surface of the insulating medium of the second thickness, wherein the bottom of the vertical through holes is in contact with the The horizontal central axes of the metal area are aligned and the distance from the center of the bottom of the vertical through hole to the corresponding edge of the metal area is smaller than the radius of the smooth curved structure; wet etching is used to A cylindrical through hole is formed at the bottom with the bottom center line of the vertical through hole as the axis, and the radius of the cylindrical through hole is greater than the thickness of the metal area; and between the vertical through hole and the cylindrical through hole Fill the hole with metal.

Preferably, before performing the step of filling metal in the vertical through hole and the cylindrical through hole, the preparation method further includes: filling the vertical through hole and the cylindrical through hole. Deposit a Ti or TiN layer.

Preferably, the edge of the upper electrode plate and/or the lower electrode plate is a smooth curved surface structure, and the mating surface of the smooth curved surface structure and the upper electrode plate and/or the lower electrode plate is a tangent surface.

Preferably, the material of the smooth curved surface structure is different from the materials of the upper electrode plate and the metal layer, and the material of the smooth curved surface structure is tungsten.

Preferably, the preparation method further includes: forming a first insulating medium on the upper plate; and forming a second insulating medium on the first insulating medium, wherein the dielectric constant of the first insulating medium is less than The dielectric constant of the second insulating medium.

Through the above technical solution, the present invention creatively forms a first insulating medium on the lower plate, and forms a metal layer in the first insulating medium, wherein the edge of the metal layer is a smooth curved surface structure, and the smooth curved surface structure is The mating surface of the metal layer is a tangential surface, and an upper plate is formed on the first insulating medium, wherein the upper plate is connected to the metal layer through a metal channel, thereby at least partially solving the upper problem of the isolation capacitor. The metal end of the plate has sharp corners and side discharge problems. At the same time, the high voltage and strong electric field of the upper plate are introduced into the silicon dioxide body to avoid breakdown at the interface of different dielectric layers (easy breakdown points) causing device failure. question.

A third aspect of the present invention provides a chip, which includes the isolation capacitor.

Other features and advantages of embodiments of the present invention will be described in detail in the detailed description that follows.

Description of drawings

The drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the description. Together with the following specific implementation modes, they are used to explain the embodiments of the present invention, but do not constitute a limitation to the embodiments of the present invention. In the attached picture:

Figure 1 is a structural diagram of an isolation capacitor in the prior art;

Figure 2 is a structural diagram of an isolation capacitor provided by an embodiment of the present invention;

Figure 3 is a structural diagram of an isolation capacitor provided by an embodiment of the present invention;

Figures 4a and 4b are structural diagrams of a substrate provided by an embodiment of the present invention;

5 to 16 are schematic structural diagrams of the preparation process of the isolation capacitor provided by an embodiment of the present invention; and

FIG. 17 is a structural diagram of an isolation capacitor in the prior art provided by an embodiment of the present invention.

Detailed ways

Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

FIG. 2 is a structural diagram of an isolation capacitor provided by an embodiment of the present invention. As shown in Figure 2, the isolation capacitor may include: a lower plate 2 provided on the substrate 1; a first insulating medium 3 provided on the lower plate 2; and provided in the first insulating medium 3 The metal layer 4, wherein the edge of the metal layer 4 is a smooth curved surface structure 7 (as shown in Figure 3), and the mating surface of the smooth curved surface structure 7 and the metal layer 4 is a tangent surface; and is located on the The upper electrode plate 5 is on the first insulating medium 3 , wherein the upper electrode plate 5 and the metal layer 4 are connected through a metal channel 6 . Therefore, the present invention proposes for the first time to transfer the strong electric field at the metal end and sides of the upper plate of the isolation capacitor into the same insulating medium through the metal channel, so that the strong electric field at the metal end and side is away from the two different insulating media. interface. It should be noted that the upper electrode plate here can be connected to any position of the metal layer through a metal channel.

The metal layer 4 and the smooth curved surface structure 7 on its edge may be formed in one piece or in two pieces (for details on the formation process, see the preparation process of the isolation capacitor below).

The metal layer 4 may be one metal layer (as shown in FIG. 2 ) or multiple metal layers (as shown in FIG. 15 , including multiple metal layers 45 and 46 ). That is, the strong electric field of the upper plate of the isolation capacitor can be introduced through the metal channel into one or more metal layers in the dielectric.

Wherein, the smooth curved surface structure may include a cylindrical structure. This arrangement makes the electric field intensity at the metal end and sides uniform and solves the problem of sharp corners and side discharges at the metal end of the conventional upper electrode plate. Of course, the smooth curved surface structure can be set to other curved surface structures according to actual conditions, but other curved surface structures will also cause discharge problems to a certain extent.

Wherein, the upper electrode plate 5 , the lower electrode plate 2 and the metal layer 4 may all be a sandwich structure formed of Ti or TiN, metal and TiN. For example, the metal may be aluminum.

Specifically, the metal layer includes two metal regions (for example, the metal regions L and R shown in Figure 2 or Figure 15) that are symmetrical about the central axis (OO').

Wherein, the central axis (OO') is the connection between the center (O) of the upper plate and the center (O') of the lower plate, and the edge of the metal area is a smooth curved structure. . As a result, the strong electric field that isolates the upper plate without capacitance can be introduced into the central area of the dielectric through the symmetrical structure, thereby avoiding the problem of device failure caused by breakdown at the interface of different dielectric layers (easy breakdown points).

Wherein, the distance from any point on the lower plate to any point on the smooth curved structure is greater than or equal to the thickness a of the first insulating medium.

As shown in FIG. 16 , the distances c and b from the left edge of the lower plate to the right edge of the metal area L of the metal layer 45 and the right edge of the metal area L of the metal layer 46 simultaneously satisfy c≥a, b≥ a; Similarly, the distances c' and b' (not shown) from the right edge of the lower electrode plate to the left edge of the metal area R of the metal layer 45 and the left edge of the metal area R of the metal layer 46 satisfy at the same time c'≥a, b'≥a, the purpose is to prevent the capacitance between the metal layer 45 or the metal layer 46 and the lower plate 2 from being broken down in advance and improve the breakdown reliability of the device over time.

As shown in FIG. 2 , the upper plate 5 is connected to the smooth curved surface structure 7 at the edge of the metal area (for example, L or R) through four metal channels 6 .

In this embodiment, the upper electrode plate can be connected to the smooth curved structure in the metal layer through a metal channel. The manufacturing process corresponding to this connection method is simpler and more efficient. It is proposed for the first time that the upper plate 5 is connected to the lower metal (i.e. metal layer 4) through the metal channel 6, so that the lower metal and the upper plate are at the same potential, effectively transferring the strong electric field at the metal end and sides of the upper plate to the insulating medium in the body, thereby preventing the current caused by the strong electric field of the conventional upper plate from breaking down along the interface between the first insulating medium 3 and the second insulating medium 8 (as shown in Figure 16), thereby improving the breakdown reliability of the device over time.

In one embodiment, the strong electric field of the upper plate of the isolation capacitor can be introduced into multiple metal layers in the dielectric through metal channels.

Specifically, the metal layer 4 is a plurality of metal layers (as shown in Figure 15, two metal layers 45 and 46).

Wherein, the number of the plurality of metal layers is determined by the thickness of the first insulating medium. However, the metal layer is at least 1 layer and at most (n-3) layers, where n is the total number of metal layers in the process determined by the chip complexity. For isolation capacitors, if the total number of metal layers in the process is n=5, which is determined by the chip complexity, the number of metal layers is at most 2.

When the metal layer is multiple metal layers, any two adjacent metal layers are connected through metal channels. If the metal layers are metal layers 45 and 46, in addition to the upper electrode plate being connected to the metal layer 46 through the metal channel 6, the metal layer 45 is connected to the metal layer 46 through the metal channel. As a result, the upper plate 5 can be connected to the lower metal (i.e., the metal layers 45 and 46) through the metal channel 6, so that the lower metal and the upper plate have the same potential, effectively connecting the metal ends of the upper plate and the strong sides of the upper plate. The electric field transfers within the body of the insulating medium, thereby preventing the current caused by the strong electric field of the conventional upper plate from breaking down along the interface between the first insulating medium 3 and the second insulating medium 8, thereby improving the breakdown reliability of the device over time. It should be noted that the previous metal layer among the adjacent metal layers may be connected to any position of the next metal layer via metal channels.

Further, in the case where the metal layer includes two metal regions that are symmetrical about the central axis, the upper metal region in the metal regions on the same side of any two adjacent metal layers is connected to the lower metal region through four metal channels. The edges of a metal area are connected by smooth curved structures.

In this embodiment, the previous metal layer can be connected to the smooth curved structure in the next metal layer through metal channels. The manufacturing process corresponding to this connection method is simpler and more efficient. As shown in Figure 15, if the metal layers are metal layers 46, 46, in addition to the upper electrode plate being connected to the metal layer 46 through the metal channel 6, the metal area L in the metal layer 46 is connected to the metal layer 45 through the metal channel. The smooth curved surface structure of the edge of the metal region L is connected to the metal region R in the metal layer 46 through the metal channel and the smooth curved surface structure of the edge of the metal region R in the metal layer 45 is connected, thereby allowing the upper electrode plate 5 to pass The metal channel 6 is connected to the lower metal (i.e., the metal layers 45 and 46), so that the lower metal and the upper plate have the same potential, effectively transferring the strong electric field at the metal end and sides of the upper plate into the body of the insulating medium, thereby avoiding conventional The current formed by the strong electric field of the upper plate breaks down along the interface between the first insulating medium 3 and the second insulating medium 8, thereby improving the breakdown reliability of the device over time.

In one embodiment, the edges of the upper plate and/or the lower plate have a smooth curved structure. As a result, tip discharge can be more effectively avoided and the breakdown reliability of the device over time can be improved.

For example, the shape of the ends and sides of the lower electrode plate can be a conventional rectangular shape or a spherical structure.

Furthermore, the material of the smooth curved surface structure is different from the materials of the upper electrode plate and the metal layer, and the material of the smooth curved surface structure is tungsten.

For example, a smooth curved structure (for example, a cylindrical structure) at the edges of the upper plate, the metal layer, and the lower plate can be filled with tungsten. This is because tungsten has a good filling effect, which can more effectively avoid tip discharge and improve the breakdown reliability of the device over time. For the first time, the metal end of the upper plate is set into a cylindrical structure (the cross-section view shows a spherical shape) and filled with tungsten metal. The end of the conventional upper plate is formed by dry etching, so the sidewall morphology is relatively rough. However, the end of the upper plate of the present invention is formed into a spherical shape by wet etching, and then filled with tungsten metal through chemical vapor deposition. Therefore, the top shape of the upper plate is fully repaired and becomes very smooth, thereby effectively avoiding tip discharge and improving the device. Breakdown reliability over time.

In one embodiment, the outer layer of the metal channel is a Ti or TiN layer. Due to the poor adhesion between tungsten and the insulating medium (oxide, such as silicon dioxide), metallic tungsten is easily separated from the insulating medium without the assistance of Ti/TiN.

In an embodiment, the isolation capacitor may further include: a first insulating medium and a second insulating medium sequentially provided on the upper plate, wherein the dielectric constant of the first insulating medium is smaller than the second insulating medium. The dielectric constant of the insulating medium.

Since the present invention transfers the strong electric field at the metal end and sides of the upper plate of the isolation capacitor into the same insulating medium through the metal channel, the strong electric field at the metal end and side is kept away from the interface of two different insulating media. Therefore, in this embodiment, a thinner first insulating medium can be provided.

To sum up, the present invention creatively disposes a first insulating medium on the lower plate, and disposes a metal layer in the first insulating medium, wherein the edge of the metal layer is a smooth curved surface structure, and on the An upper plate is disposed on the first insulating medium, wherein the upper plate is connected to the metal layer through a metal channel, thereby at least partially solving the problem of sharp corners and side discharge of metal ends of the upper plate of the isolation capacitor, and at the same time The high voltage and strong electric field of the upper plate are introduced into the silicon dioxide body to avoid breakdown at the interface of different dielectric layers (easy breakdown points) causing device failure.

An embodiment of the present invention provides a method for preparing an isolation capacitor. The preparation method includes: forming a lower plate on a substrate; forming a first insulating medium on the lower plate; and forming a first insulating medium inside the first insulating medium. Forming a metal layer, wherein the edge of the metal layer is a smooth curved surface structure, and the mating surface of the smooth curved surface structure and the metal layer is a tangent surface; and forming an upper plate on the first insulating medium, wherein the The upper electrode plate is connected to the metal layer through metal channels.

As shown in Figure 4a, the substrate 1 includes a substrate 11, an insulating medium 12, and a metal 10. In other figures below, they are represented by the substrate 1 shown in Figure 4b.

In one embodiment, a metal layer is formed inside the first insulating layer. Specifically, the metal layer and the upper electrode plate can be prepared through the following process.

forming a metal layer inside the first insulating medium; and forming an upper plate on the first insulating medium, including: forming a metal layer inside the first insulating medium, wherein the metal layer includes a Two axially symmetrical metal regions, and the central axis is a connection between the center of the upper pole plate and the center of the lower pole plate; separate connections are formed downward from the upper surface of the first insulating medium. two sets of through holes to the two metal regions, and filling metal in the two sets of through holes to form two sets of metal channels and a smooth curved structure at the edges of the two metal regions, wherein each set of through holes surrounds The horizontal distance from the edge of the formed area to the edge of the corresponding metal area is smaller than the radius of the smooth curved structure; and an upper plate covering the two sets of metal channels is formed on the first insulating medium.

Specifically, two sets of through holes respectively connected to the two metal regions are formed downward from the upper surface of the first insulating medium, and metal is filled in the two sets of through holes to form two sets of metal channels. The smooth curved surface structure with the edges of the two metal areas includes: using dry etching to form two sets of vertical through holes from the upper surface of the first insulating medium downward, wherein each set of vertical through holes includes four A vertical through hole, and the bottom of the vertical through hole is aligned with the horizontal central axis of the metal area and the distance from the center of the bottom of the vertical through hole to the corresponding edge of the metal area is less than the smooth The radius of the curved surface structure; wet etching is used to form a cylindrical through hole with the bottom center line of the vertical through hole as the axis at the bottom of the two sets of vertical through holes, and the radius of the cylindrical through hole is greater than the The thickness of the metal area; and filling metal in the vertical through hole and the cylindrical through hole.

In another embodiment, a plurality of metal layers are formed inside the first insulating layer. Wherein, the number of the plurality of metal layers is determined by the thickness of the first insulating medium. Specifically, multiple metal layers and upper electrode plates can be prepared through the following process.

When the metal layer is a plurality of metal layers, a first insulating medium is formed on the lower plate; a metal layer is formed inside the first insulating medium; and a first insulating medium is formed on the first insulating medium. The upper plate includes: forming an insulating medium of a first thickness on the lower plate or the next metal layer; forming a first metal layer on the insulating medium of the first thickness, wherein the first metal layer includes Two metal regions are symmetrical about a central axis, and the central axis is a line between the center of the upper plate and the center of the lower plate; forming a second thickness on the first metal layer Insulating medium; forming two sets of through holes connected to the four edges of the two metal regions from the upper surface of the insulating medium of the second thickness downward, and filling the two sets of through holes with metal to form A smooth curved surface structure between two groups of metal channels and the edges of the two metal areas, wherein the horizontal distance from the edge of the area surrounded by each group of through holes to the edge of the corresponding metal area is smaller than the radius of the smooth curved surface structure; in the A second metal layer covering the two sets of metal channels is formed on an insulating medium of a second thickness to form any two adjacent metal layers; and when the total thickness of each insulating medium is equal to the thickness of the first insulating medium Next, an upper plate covering the metal channel is formed on the first insulating medium.

Specifically, two sets of through holes are formed downwardly from the upper surface of the insulating medium of the second thickness, respectively connected to the four edges of the two metal regions, and metal is filled in the two sets of through holes. To form two sets of metal channels and a smooth curved structure at the edges of the two metal regions, the method includes: using dry etching to form two sets of vertical through holes downwardly from the upper surface of the insulating medium of the second thickness, wherein Each group of vertical through holes includes four vertical through holes, and the bottom of the vertical through holes is aligned with the horizontal central axis of the metal area and the center of the bottom of the vertical through holes is to the center of the metal area. The distance between the corresponding edges is less than the radius of the smooth curved surface structure; wet etching is used to form a cylindrical through hole at the bottom of the two sets of vertical through holes with the bottom center line of the vertical through holes as the axis. The radius of the cylindrical through hole is greater than the thickness of the metal area; and the vertical through hole and the cylindrical through hole are filled with metal.

For any of the above embodiments, before performing the step of filling metal in the vertical through hole and the cylindrical through hole, the preparation method may further include: filling the vertical through hole and the cylindrical through hole with metal. A Ti or TiN layer is deposited in the cylindrical through hole. Due to the poor adhesion between tungsten and the insulating medium (oxide, such as silicon dioxide), metallic tungsten is easily separated from the insulating medium without the assistance of Ti/TiN.

For any of the above embodiments, the distance from any point on the lower plate to any point on the smooth curved structure is greater than or equal to the thickness of the first insulating medium.

As shown in Figure 2, the distance c from the left edge of the lower electrode plate to the right edge of the metal area L of the metal layer 4 satisfies c≥a; similarly, the distance c from the left edge of the lower electrode plate to the metal area of the metal layer 4 The distance c' from the left edge of R satisfies c' ≥ a. The purpose is to prevent the capacitance between the metal layer 4 and the lower plate 2 from being broken down in advance and improve the breakdown reliability of the device over time.

As shown in FIG. 16 , the distances c and b from the left edge of the lower plate to the right edge of the metal area L of the metal layer 45 and the right edge of the metal area L of the metal layer 46 simultaneously satisfy c≥a, b≥ a; Similarly, the distances c' and b' (not shown) from the right edge of the lower electrode plate to the left edge of the metal area R of the metal layer 45 and the left edge of the metal area R of the metal layer 46 satisfy at the same time c'≥a, b'≥a, the purpose is to prevent the capacitance between the metal layer 45 or the metal layer 46 and the lower plate 2 from being broken down in advance and improve the breakdown reliability of the device over time.

For any of the above embodiments, the edges of the upper electrode plate and/or the lower electrode plate have a smooth curved surface structure, and the cooperation between the smooth curved surface structure and the upper electrode plate and/or the lower electrode plate The surface is a cut surface. For example, the shape of the ends and sides of the lower electrode plate can be a conventional rectangular shape or a cylindrical structure.

For any of the above embodiments, the material of the smooth curved surface structure is different from the materials of the upper electrode plate and the metal layer, and the material of the smooth curved surface structure is tungsten.

For example, the upper plate, the metal layer, the smooth curved structure (eg, cylindrical structure) at the edge/end of the lower plate can be filled with tungsten. This is because tungsten has a good filling effect, which can more effectively avoid tip discharge and improve the breakdown reliability of the device over time. For the first time, the metal end of the upper plate is set into a cylindrical shape and filled with tungsten metal. The end of the conventional upper plate is formed by dry etching, so the sidewall morphology is relatively rough. However, the end of the upper electrode plate of the present invention is formed into a cylindrical shape by wet etching, and then filled with tungsten metal through chemical vapor deposition. Therefore, the top end of the upper electrode plate is fully repaired and becomes very smooth, thereby effectively avoiding tip discharge and improving the device. Breakdown reliability over time.

In one embodiment, the preparation method further includes: forming a first insulating medium on the upper electrode plate; and forming a second insulating medium on the first insulating medium, wherein the intermediary of the first insulating medium The electrical constant is smaller than the dielectric constant of the second insulating medium. Since the present invention transfers the strong electric field at the metal end and sides of the upper plate of the isolation capacitor into the same insulating medium through the metal channel, the strong electric field at the metal end and side is kept away from the interface of two different insulating media. Therefore, in this embodiment, a thinner first insulation thickness can be provided.

The preparation process of the isolation capacitor will be described below with reference to Figures 5 to 15 as examples.

As shown in Figure 5, a physical vapor deposition method is used to deposit a sandwich structure of Ti/TiN (not shown), metal 20, and TiN (not shown) on substrate 1. In various embodiments of the present invention, the metal X of the sandwich structure is referred to as metal Metal 20.

As shown in FIG. 6 , photoresist is spin-coated on the metal 20 , and then exposure, development, etching, etc. are performed to etch away the unnecessary metal 20 , leaving only the required metal 20 as the lower plate 2 .

As shown in FIG. 7 , the first layer of insulating dielectric 3 is deposited using PECVD, and then chemical mechanical polishing is used to planarize the insulating dielectric 3 . The insulating medium 3 in this embodiment is silicon dioxide. The deposition method is to use tetraethoxysilane (TEOS) to decompose at about 400°C to form a silicon dioxide dielectric layer.

As shown in FIG. 8 , a physical vapor deposition method is used to deposit metal 30 on the insulating medium 3 .

As shown in Figure 9, photoresist is spin-coated on the metal 30, and then exposure, development, etching, etc. are performed to etch away the unnecessary metal 30, leaving only the required metal 30 (which includes the metal area L, R) to form metal layer 45.

As shown in Figure 10, a second layer of insulating dielectric 3 is deposited using PECVD, and then chemical mechanical polishing is used to planarize the insulating dielectric 3. The insulating medium 3 in this embodiment is silicon dioxide. The deposition method is to use tetraethoxysilane (TEOS) to decompose at about 400°C to form a silicon dioxide dielectric layer.

As shown in Figure 11, through-hole exposure, development, and dry etching are performed on the second layer of insulating medium 3. The dry etching is anisotropic etching, so a straight topography can be etched to form a vertical Straight hole.

As shown in Figure 12, the formed vertical through hole is further etched. This etching uses wet etching, which is isotropic etching. Therefore, the bottom (for example, the center) of the through hole formed in the previous step is the center of the circle. At the same time, isotropic etching is performed with a certain radius to form a spherical hollow through hole (Figure 12 is a cross-sectional view, for the actual three-dimensional situation, a cylindrical through hole is formed). Among them, the vertical through hole and the hollow through hole form the through hole 31 . However, during the process of forming the sphere, the metal cannot be etched away, so the two ends are incomplete spheres.

As shown in Figure 13, a layer of Ti/TiN is deposited using physical vapor deposition method (due to the poor adhesion between tungsten and oxide, metallic tungsten is easily separated from the oxide without the assistance of Ti/TiN) , then deposit a layer of tungsten metal, and then perform chemical mechanical polishing to polish the tungsten metal. If only one metal layer is prepared (as shown in FIG. 2 ), the following steps corresponding to the metal 40 and the through hole 41 in FIG. 14 can be skipped.

As shown in Figure 14, the formation of metal 40, through hole 41, metal 50, and through hole 51 adopts the same steps as the above-mentioned metal 30 and through hole 31. The filling of metal tungsten is also similar, that is, corresponding to Figures 8 to 13 step. Among them, one thing to note is that the stop position of the chemical mechanical polishing of the through hole 51 is just in contact with the circular sphere.

As shown in Figure 15, a layer of insulating dielectric 3 is deposited using HDP CVD, and then a layer of insulating dielectric 8 is deposited using PECVD. Afterwards, the window is exposed, developed, and etched to form a window for packaging and wiring. At this point, a new isolation capacitor structure has been prepared.

To sum up, the present invention creatively forms a first insulating medium on the lower plate, forms a metal layer in the first insulating medium, wherein the edge of the metal layer has a smooth curved surface structure, and the first insulating medium is An upper electrode plate is formed on the medium, wherein the upper electrode plate is connected to the metal layer through a metal channel, thereby at least partially solving the problem of sharp corners and side discharge of the metal ends of the upper electrode plate of the isolation capacitor, and at the same time, the upper electrode plate is connected to the metal layer through a metal channel. The high voltage and strong electric field of the board are introduced into the silicon dioxide body to avoid breakdown at the interface of different dielectric layers (easy breakdown points) causing device failure.

An embodiment of the present invention also provides a chip, which includes the isolation capacitor.

For specific details and benefits of the chip provided by the present invention, please refer to the above description of the isolation capacitor, and will not be described again here.

The optional implementations of the embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above-mentioned implementations. Within the scope of the technical concept of the embodiments of the present invention, the embodiments of the present invention can be modified. The technical solution is subjected to various simple modifications, and these simple modifications all belong to the protection scope of the embodiments of the present invention.

In addition, it should be noted that the specific technical features described in the above-mentioned specific embodiments can be combined in any suitable manner as long as there is no contradiction. In order to avoid unnecessary repetition, various possible combinations will not be further described in the embodiments of the present invention.

In addition, any combination of different implementation modes of the embodiments of the present invention can also be performed. As long as they do not violate the ideas of the embodiments of the present invention, they should also be regarded as the content disclosed in the embodiments of the present invention.

Claims (23)

1. An isolation capacitor, characterized in that the isolation capacitor includes: The lower plate is located on the base; a first insulating medium provided on the lower plate; A metal layer provided in the first insulating medium, wherein the edge of the metal layer is a smooth curved surface structure, and the mating surface of the smooth curved surface structure and the metal layer is a tangent surface; and an upper electrode plate disposed on the first insulating medium, wherein the upper electrode plate and the metal layer are connected through a metal channel, Wherein, the distance from any point on the lower plate to any point on the smooth curved structure is greater than or equal to the thickness of the first insulating medium. 2. The isolation capacitor according to claim 1, wherein the metal layer includes two metal regions that are symmetrical about a central axis, The central axis is a line connecting the center of the upper plate and the center of the lower plate, and the edge of the metal area is a smooth curved structure. 3. The isolation capacitor according to claim 2, wherein the upper plate is connected to the smooth curved structure at the edge of the metal area through four metal channels. 4. The isolation capacitor according to any one of claims 1 to 3, wherein when the metal layer is a plurality of metal layers, any two adjacent metal layers are connected through a metal channel. 5. The isolation capacitor according to claim 4, wherein when the metal layer includes two metal regions that are symmetrical about a central axis, the metal regions on the same side of any two adjacent metal layers The upper metal area in the metal area is connected to the smooth curved surface structure at the edge of the next metal area through four metal channels. 6. The isolation capacitor according to claim 4, wherein the number of the plurality of metal layers is determined by the thickness of the first insulating medium. 7. The isolation capacitor according to claim 1, wherein the edges of the upper plate and/or the lower plate have a smooth curved structure, and the smooth curved structure is in contact with the upper plate and/or the lower plate. The mating surface of the lower electrode plate is a tangential surface. 8. The isolation capacitor according to claim 7, wherein the material of the smooth curved surface structure is different from the materials of the upper plate and the metal layer, and the material of the smooth curved surface structure is tungsten. . 9. The isolation capacitor according to claim 1, wherein the upper plate, the lower plate and the metal layer are all sandwich structures formed by Ti or TiN, metal and TiN. 10. The isolation capacitor according to claim 1, wherein the outer layer of the metal channel is a Ti or TiN layer. 11. The isolation capacitor according to claim 1, wherein the isolation capacitor further includes: a first insulating medium and a second insulating medium sequentially provided on the upper plate, wherein the first insulating medium The dielectric constant of the second insulating medium is smaller than the dielectric constant of the second insulating medium. 12. The isolation capacitor according to claim 1, wherein the smooth curved structure includes a cylindrical structure. 13. A method for preparing an isolation capacitor, characterized in that the preparation method includes: forming a lower plate on the substrate; Form a first insulating medium on the lower plate; A metal layer is formed inside the first insulating medium, wherein the edge of the metal layer is a smooth curved surface structure, and the mating surface of the smooth curved surface structure and the metal layer is a tangent surface; and forming an upper electrode plate on the first insulating medium, wherein the upper electrode plate and the metal layer are connected through a metal channel, Wherein, the distance from any point on the lower plate to any point on the smooth curved structure is greater than or equal to the thickness of the first insulating medium. 14. The preparation method according to claim 13, characterized in that forming a metal layer inside the first insulating medium; and forming an upper plate on the first insulating medium, including: A metal layer is formed inside the first insulating medium, wherein the metal layer includes two metal regions that are symmetrical about a central axis, and the central axis is the center of the upper plate and the center of the lower plate. the connection between; Two sets of through holes respectively connected to the two metal regions are formed from the upper surface of the first insulating medium downward, and metal is filled in the two sets of through holes to form two sets of metal channels and the two A smooth curved surface structure at the edge of the metal area, wherein the horizontal distance from the edge of the area surrounded by each group of through holes to the edge of the corresponding metal area is smaller than the radius of the smooth curved surface structure; and An upper plate covering the two sets of metal channels is formed on the first insulating medium. 15. The preparation method according to claim 14, characterized in that, two sets of through holes respectively connected to the two metal regions are formed downward from the upper surface of the first insulating medium, and in the Two sets of through holes are filled with metal to form two sets of metal channels and a smooth curved structure at the edges of the two metal areas, including: Dry etching is used to form two sets of vertical through holes from the upper surface of the first insulating medium downward, wherein each set of vertical through holes includes four vertical through holes, and the bottom of the vertical through holes and all the vertical through holes are The horizontal central axes of the metal area are aligned and the distance from the center of the bottom of the vertical through hole to the corresponding edge of the metal area is smaller than the radius of the smooth curved surface structure; Wet etching is used to form a cylindrical through hole at the bottom of the two sets of vertical through holes with the bottom center line of the vertical through hole as the axis. The radius of the cylindrical through hole is greater than the thickness of the metal area. ;as well as The vertical through holes and the cylindrical through holes are filled with metal. 16. The preparation method according to claim 13, characterized in that, when the metal layer is a plurality of metal layers, a first insulating medium is formed on the lower plate; forming a metal layer inside; and forming an upper plate on the first insulating medium, including: forming an insulating medium of a first thickness on the lower electrode plate or next metal layer; A first metal layer is formed on the insulating medium of the first thickness, wherein the first metal layer includes two metal regions that are symmetrical about a central axis, and the central axis is the center of the upper plate and the The line between the centers of the lower plates; forming an insulating medium of a second thickness on the first metal layer; Two sets of through holes respectively connected to the four edges of the two metal regions are formed downward from the upper surface of the insulating medium of the second thickness, and metal is filled in the two sets of through holes to form two sets of metal A smooth curved surface structure between the channel and the edges of the two metal areas, wherein the horizontal distance from the edge of the area surrounded by each group of through holes to the edge of the corresponding metal area is smaller than the radius of the smooth curved surface structure; Form a second metal layer covering the two sets of metal channels on the insulating medium of the second thickness to form any two adjacent metal layers; and When the total thickness of each insulating medium is equal to the thickness of the first insulating medium, an upper plate covering the metal channel is formed on the first insulating medium. 17. The preparation method according to claim 16, wherein the number of the plurality of metal layers is determined by the thickness of the first insulating medium. 18. The preparation method according to claim 16, wherein two sets of passages are formed downwardly from the upper surface of the insulating medium of the second thickness, respectively connected to four edges of the two metal regions. holes, and fill the two sets of through holes with metal to form two sets of metal channels and a smooth curved structure at the edges of the two metal areas, including: Use dry etching to form two sets of vertical through holes from the upper surface of the second thickness of the insulating medium downward, wherein each set of vertical through holes includes four vertical through holes, and the bottom of the vertical through holes Aligned with the horizontal central axis of the metal area and the distance from the center of the bottom of the vertical through hole to the corresponding edge of the metal area is smaller than the radius of the smooth curved surface structure; Wet etching is used to form a cylindrical through hole at the bottom of the two sets of vertical through holes with the bottom center line of the vertical through hole as the axis. The radius of the cylindrical through hole is greater than the thickness of the metal area. ;as well as The vertical through holes and the cylindrical through holes are filled with metal. 19. The preparation method according to claim 15 or 18, characterized in that, before performing the step of filling metal in the vertical through holes and the cylindrical through holes, the preparation method further includes: A Ti or TiN layer is deposited in the vertical through hole and the cylindrical through hole. 20. The preparation method according to claim 13, wherein the edges of the upper electrode plate and/or the lower electrode plate have a smooth curved surface structure, and the smooth curved surface structure is in contact with the upper electrode plate and/or the lower electrode plate. The mating surface of the lower electrode plate is a tangential surface. 21. The preparation method according to claim 20, wherein the material of the smooth curved surface structure is different from the materials of the upper electrode plate and the metal layer, and the material of the smooth curved surface structure is tungsten. . 22. The preparation method according to claim 13, characterized in that the preparation method further includes: Forming a first insulating medium on the upper plate; and A second insulating medium is formed on the first insulating medium, wherein the dielectric constant of the first insulating medium is smaller than the dielectric constant of the second insulating medium. 23. A chip, characterized in that the chip includes the isolation capacitor according to any one of claims 1-12.