CN112271211B - Terminal structure of sectional type composite field plate - Google Patents

Abstract

The invention proposes a terminal structure of a segmented composite field plate, which belongs to the technical field of power semiconductor devices. The invention includes a ring injection area, polysilicon, a short field plate, a contact hole, and a cutoff ring metal; the ring injection area is located outside the gate lead, and the polysilicon is located outside the ring injection area; the ring injection area and the polysilicon are repeatedly arranged in multiple groups; and the cutoff ring The metal is outside the last polysilicon, which is the outermost structure of the chip; the short field plate is on the ring injection area and the polysilicon, and is connected to the ring injection area through the contact hole; the short field plate is arranged in an array on the polysilicon to form the polysilicon and Array area of short field plate. This structure solves the problem that when realizing the connection between the metal field plate and the field limiting ring, the distance between the field limiting ring is too close, the distance between the contact hole and the metal edge is not enough, resulting in the metal spacing not meeting the requirements of the metal wet etching process. In the limited A higher withstand voltage is achieved on the terminal area, while also improving the device's ability to withstand thermal stress.

Description

Segmented Composite Field Slab Terminal Structure

Technical field

The invention relates to the technical field of power semiconductor devices, and in particular to a terminal structure of a segmented composite field plate.

Background technique

As power semiconductor devices continue to develop toward high voltage and high current, the requirements for device structure, process, and reliability are getting higher and higher.

A structure commonly used in terminal protection of high-voltage devices is composite terminal technology that combines field limiting rings, polycrystalline field plates, and metal field plates, which can effectively improve device withstand voltage. In order to ensure the reliability of the device, a bias field plate is often used to connect the metal field plate and the field limiting ring through contact holes. Since the higher the withstand voltage of the device, the more field limiting rings and metal field plates need to be designed. When connecting the metal field plates and field limiting rings, the distance between the field limiting rings will be too close, and the distance between the contact holes and the metal edge will not be enough, resulting in The metal spacing cannot meet the requirements of the metal wet etching process. As shown in Figure 1, the existing technology is to make contact holes at the four corners of the chip to connect the metal field plate and the field limiting ring. By increasing the width of the field limiting ring, sufficient distance is obtained to realize the biased field plate. The problem with this design is that the curvature radius of the field limiting ring is reduced, and the device withstand voltage is relatively reduced.

Contents of the invention

The purpose of the present invention is to provide a terminal structure of a segmented composite field plate to solve the problems existing in the prior art.

The technical solutions adopted by the present invention are:

A terminal structure of a segmented composite field plate, which is characterized by:

The structure includes a ring injection region, polysilicon, a short field plate, a contact hole, and a cutoff ring metal;

The ring injection area is located outside the gate lead, and the polysilicon is located outside the ring injection area; the ring injection area and the polysilicon are repeatedly arranged in multiple groups;

The cutoff ring metal is outside the last polysilicon and is the outermost ring structure of the chip;

The short field plates are on the ring injection area and polysilicon, and are connected to the ring injection area through contact holes; the short field plates are arranged in an array on the polysilicon to form an array area of polysilicon and short field plates.

The array arrangement of polysilicon and short field plates forms a segmented composite field plate.

The array arrangement means that in the array area of polysilicon and short field plates, the short field plates and short field plates are staggered and arranged at intervals along the X-axis direction; along the Y-axis direction, the polysilicon and short field plates are arranged at intervals.

The short field plate thickness is greater than the polysilicon thickness.

The short field plate is a bias field plate. The short field plate is on the ring injection area and the polysilicon, and is connected to the ring injection area through a contact hole, and the contact hole is located at the flat edge of the chip.

The spacing of the short field plates along the X-axis is greater than the length of the short field plates.

The spacing of the short field plates along the Y-axis is smaller than the width of the short field plates.

There is a ring injection area under the cutoff ring metal. This ring injection area is different from other ring injection areas and functions to form a cutoff ring.

The invention has the following advantages:

Based on the existing technology, the present invention uses segmented composite field plates, that is, an array arrangement of polysilicon and short field plates, so that the width of the metal strips breaks the etching spacing limit, and the metal spacing fully meets the requirements of the metal wet etching process. . In the structure proposed by the present invention, the contact holes of the existing metal field plates and field limiting rings are designed from the four corners of the chip to the flat sides of the chip, ensuring the consistency of the field limiting ring design. A higher withstand voltage is achieved in a limited terminal area, ultimately enabling devices with the same area to have higher withstand voltage. In addition, the structure involved in the present invention improves device reliability from two aspects. First, the new design improved from the existing metal field plate is a segmented composite field plate. Each short field plate can disperse the stress on the metal field plate. force, so that the stress between the plastic packaging material and the chip surface is reduced, and the device's ability to withstand thermal stress during the thermal cycle is improved; secondly, the function of the contact hole involved in the present invention is to realize a bias field plate, which can make the device have higher The stability satisfies the high-temperature aging assessment under 150℃ and 100% BV _DSS conditions.

Description of the drawings

Figure 1 is a schematic diagram of the chip surface in the prior art;

Figure 2 is a schematic structural diagram of the segmented composite field plate.

Figure 3 is an example of the structural layout of a segmented composite field plate;

Figure 4 is a schematic diagram of the stress analysis on the chip surface.

Detailed ways

Specific embodiments of the present invention will be described in detail below with reference to examples. Those skilled in the art can easily understand the advantages, effects and design methods of the present invention from the content disclosed in the specification. The present invention can also be implemented or applied through other different specific embodiments, and can be modified or applied in the same type based on the design concept of the present invention.

The present invention does not involve a process and is compatible with ordinary VDMOS processes. Its structure is mainly realized through layout, and it belongs to the horizontal structure of the device, and the vertical structure and function do not change.

As shown in Figure 3, the present invention discloses a terminal structure of a segmented composite field plate. The structure includes a ring injection region, polysilicon, a short field plate, a contact hole, and a cutoff ring metal; this structure belongs to a power semiconductor device. The terminal structure of a general device is the active area, the gate lead, and the terminal structure in order from the inside to the outside; the ring injection area referred to in the terminal structure of the segmented composite field plate of the present invention is located outside the gate lead; the polysilicon is located outside the ring injection area ; The ring injection area and polysilicon are repeatedly arranged in multiple groups; the final cutoff ring metal is outside the last polysilicon, which is the outermost ring structure of the chip; the short field plate is on the ring injection area and polysilicon, and is connected to the ring injection area through contact holes connect. The technical feature of the present invention is the invention of a segmented composite field plate, which is characterized in that short field plates are arranged in an array on polysilicon to form an array area of polysilicon and short field plates.

This structure is located in the terminal area of the device. The layout design is the same as the ordinary layout design rules. First, the active area cell arrangement is completed, then the gate leads are arranged, and then the ring injection area, polysilicon and short field plate are arranged; the ring injection area is located at the gate Outside the lead; polysilicon is located outside the ring injection area, and the ring injection area and polysilicon are arranged in 5 repeated groups. The cutoff ring metal is outside the polysilicon and is the outermost ring structure of the chip; the short field plate is above the ring injection area and polysilicon, and is implemented through contact holes and the connection to the ring injection zone. A ring injection area is made under the cutoff ring metal. This ring injection area is different from other ring injection areas and functions to form a cutoff ring.

The short field plates are arranged in an array on the polysilicon. The arrangement method is shown in Figure 3. In the array area of the polysilicon and short field plates, along the X-axis direction, the short field plates and short field plates are staggered and arranged at intervals; along the Y-axis direction , polysilicon and short field plates are spaced apart. The length of the short field plate is 30 μm, and the spacing between the short field plates along the X-axis is 1 short field plate length plus 2.5 metal wet etching process redundancies. The spacing of short field plates along the Y-axis is more flexible.

As shown in the example of Figure 3, the spacing S1 of the short field plate in the X-axis direction is 40 μm. The spacing S2 in the Y-axis direction is 19.2 μm, which meets the line width requirements of the wet etching process, allowing sufficient distance to place polysilicon and short field plates, as well as short field plates and contact holes in the ring injection area. The width of the contact holes is 20 μm. . The first function of the short field plate is to make the width of the metal strip in the Y direction break the etching spacing limit, and the metal spacing fully meets the requirements of the metal wet etching process. The second is to reduce chip surface stress. The principle is shown in Figure 4. This structure distributes the force that originally acts on the metal field plate to multiple short field plates.

The content of the present invention is not limited to the examples listed. Any equivalent transformations made to the technical solution of the present invention by those of ordinary skill in the art after reading the description of the present invention will be covered by the claims of the present invention.

Claims (6)

1. A terminal structure of a segmented composite field plate, characterized by: The structure includes a ring injection region, polysilicon, a short field plate, a contact hole, and a cutoff ring metal; The ring injection area is located outside the gate lead, and the polysilicon is located outside the ring injection area; the ring injection area and the polysilicon are repeatedly arranged in multiple groups; The cutoff ring metal is outside the last polysilicon and is the outermost ring structure of the chip; The short field plates are on the ring injection area and polysilicon, and are connected to the ring injection area through contact holes; the short field plates are arranged in an array on the polysilicon to form an array area of polysilicon and short field plates; The array arrangement of polysilicon and short field plates forms a segmented composite field plate; The array arrangement means that in the array area of polysilicon and short field plates, the short field plates and short field plates are staggered and arranged at intervals along the X-axis direction; along the Y-axis direction, the polysilicon and short field plates are arranged at intervals. 2. The terminal structure of the segmented composite field plate according to claim 1, characterized in that: The short field plate thickness is greater than the polysilicon thickness. 3. The terminal structure of the segmented composite field plate according to claim 2, characterized in that: The short field plate is a bias field plate. The short field plate is on the ring injection area and the polysilicon, and is connected to the ring injection area through a contact hole, and the contact hole is located at the flat edge of the chip. 4. The terminal structure of the segmented composite field plate according to claim 3, characterized in that: The spacing of the short field plates along the X-axis is greater than the length of the short field plates. 5. The terminal structure of the segmented composite field plate according to claim 4, characterized in that: The spacing of the short field plates along the Y-axis is smaller than the width of the short field plates. 6. The terminal structure of the segmented composite field plate according to claim 5, characterized in that: There is a ring injection area under the cutoff ring metal. This ring injection area is different from other ring injection areas and functions to form a cutoff ring.