CN114429908A - A kind of RFLDMOS device and its manufacturing method - Google Patents

Abstract

The invention provides an RFLDMOS device and a manufacturing method thereof, which comprises the steps of providing a substrate, forming an epitaxial layer on the substrate, growing a thick gate oxide layer above the epitaxial layer, photoetching and opening a source region forming region, a part of grid electrode forming region close to a source and a part of drift region forming region close to a grid, removing the thick gate oxide layer of the photoetching and opening region by utilizing a wet etching process, forming undercuts at two ends of the rest thick gate oxide layer, growing a thin gate oxide layer above the epitaxial layer, forming a stepped gate oxide layer by the thin gate oxide layer and the thick gate oxide layer together, and carrying out subsequent processes to form a stepped Faraday shield. The step-type Faraday shield improves hot carrier performance while considering breakdown voltage, reduces the resistance of the Faraday shield to the ground, effectively improves the reliability and frequency characteristic of a device, ensures that a single-layer Faraday shield can achieve the effect of the traditional two-layer or even three-layer Faraday shield, reduces the photoetching level of the Faraday shield, simplifies the process and saves the cost.

Description

A kind of RFLDMOS device and its manufacturing method

technical field

The invention relates to the technical field of semiconductor manufacturing, in particular to an RFLDMOS device and a manufacturing method thereof.

Background technique

RFLDMOS (Radio Frequency Laterally Diffused Metal Oxide Semiconductor, Radio Frequency Laterally Diffused Metal Oxide Semiconductor) is a radio frequency power device, which has the characteristics of high gain, high linearity, high withstand voltage, and high output power. RFLDMOS devices are widely used in RF base stations, wireless broadcasting stations, radars and other fields. Power arrays and multi-chip synthesis are used, and the output power of the products can reach more than 500W.

Faraday shields are often used in RFLDMOS devices. As shown in FIG. 1, it is a cross-sectional view of an RFLDMOS device with a Faraday shield, an epitaxial layer 12 is formed on a substrate 11, a source region 15 and a drain region 17 are located in the body region 14 and the drift region 13, respectively, and are heavily doped The impurity region 16 is connected to the source region 15, the surface of the epitaxial layer between the body region 14 and the drift region 13 has a gate oxide layer 18 and a polysilicon gate 19, and a metal silicide is formed on the surface of the source region 15, the drain region 17 and the polysilicon gate 19. 23; the Faraday shielding layer 20 is located on the polysilicon gate 19, and the dielectric layer 21 is separated from the polysilicon gate 19. The Faraday shield 20 is connected to the source region 15 and the sinker channel 22 through metal contact wires, and the sinker channel 22 is connected to the substrate 11 . The Faraday shield 20 can move the position of the strong electric field inside the device from the edge of the gate to the bottom of the shielding layer, which can reduce the injection of hot carriers into the gate during high voltage applications, thereby improving the reliability of the device. At the same time, the Faraday shield 20 can also greatly reduce the capacitance Cgd between the gate and the drain, that is, the Miller capacitance, and improve the frequency characteristics of the device.

In the prior art, in order to further improve the reliability and frequency characteristics of the device and optimize the device performance, as shown in Figure 2, the RFLDMOS device can also use a double-layer or even three-layer Faraday shield, but this will greatly increase the process complexity and cost. .

SUMMARY OF THE INVENTION

In view of this, the present invention provides an RFLDMOS device and a manufacturing method thereof, which are used to solve the problem of increased process complexity and cost due to the use of a multi-layer Faraday shield in the prior art, and realize the use of a single-layer Faraday shield. The purpose of the multi-layer Faraday shield effect can be achieved.

The present invention provides a method for manufacturing an RFLDMOS device, comprising the following steps:

Step 1, providing a substrate, forming an epitaxial layer on the substrate, and growing a thick gate oxide layer on the epitaxial layer;

Step 2, photolithography opens the source region formation region, the partial gate formation region close to the source, and the gate drift region formation region;

Step 3, using a wet etching process to remove the thick gate oxide layer in the lithography open area, and form undercuts at both ends of the remaining thick gate oxide layer;

Step 4, growing a thin gate oxide layer above the epitaxial layer, and the thin gate oxide layer and the thick gate oxide layer together form a stepped gate oxide layer;

Step 5, depositing polysilicon and forming a gate in the gate formation region by using a photolithography etching process;

Step 6, forming a body region and a drift region in the epitaxial layer;

Step 7, forming gate sidewalls, forming a heavily doped region and a source region in the body region, and forming a drain region in the drift region;

Step 8, forming metal silicide on the source region, the drain region and the gate;

Step 9, depositing a dielectric layer, the dielectric layer covering the body region, the drift region and the top of the gate;

Step ten, depositing a Faraday shielding layer on the dielectric layer;

Step 11, forming a Faraday shield over a portion of the gate close to the drain region and over a portion of the drift region close to the gate using a photolithography process.

Preferably, in step 1, the substrate is N-type, or, the substrate is P-type.

Preferably, after the undercut is formed in step 3, the shape of the thick gate oxide layer becomes two isosceles trapezoids spaced apart on the epitaxial layer.

Preferably, the upper left corner of the gate in step 5 is stepped.

Preferably, the dielectric layer in step 9 is a silicon oxide layer.

Preferably, the material of the Faraday shielding layer in step ten is tungsten silicon or titanium nitride.

Preferably, the Faraday shield in step eleven is of a stepped type.

Preferably, the method further includes: forming a sinking through hole, the bottom of the sinking through hole is located in the substrate, and the sinking through hole penetrates the body region and the epitaxial layer.

The present invention also provides an RFLDMOS device, comprising:

substrate;

an epitaxial layer located above the substrate; a drift region and a body region are arranged in the epitaxial layer; a drain region is arranged in the drift region, a heavily doped region and a source region are arranged in the body region, and the a heavily doped region is connected to the source region;

a stepped gate oxide layer located above the epitaxial layer;

a gate structure located on the surface of the epitaxial layer, the gate structure comprising the gate oxide layer, a gate and a gate spacer;

a metal silicide over the source region, the drain region and the gate;

a dielectric layer covering the body region, the drift region and the top of the gate structure;

a Faraday shield covering the dielectric layer and over a portion of the gate close to the drain region and over a portion of the drift region close to the gate; and

a sinking through hole, the bottom of the sinking through hole is located in the substrate and penetrates the body region and the epitaxial layer;

Wherein, the gate oxide layer in the gate structure has a slope under the gate, and the gate oxide layer on the side of the drain region is thicker than the gate oxide layer on the side of the source region; the Faraday shield is Ladder type.

The invention improves the Faraday shield of the existing RFLDMOS device, and changes the existing stepped Faraday shield into a stepped Faraday shield, so that the RFLDMOS device of the single-layer Faraday shield can achieve the traditional two-layer or even three-layer Faraday shield. The effect of shielding the RFLDMOS device solves the problems of increased process complexity and cost due to the use of a multi-layer Faraday shield in the prior art.

Description of drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic structural diagram of an existing RFLDMOS device with a layer of Faraday shield;

FIG. 2 is a schematic structural diagram of an existing RFLDMOS device with a two-layer Faraday shield;

3 shows a flowchart of a method for manufacturing an RFLDMOS device according to an embodiment of the present invention;

FIG. 4-FIG. 10 are schematic structural diagrams of each step in the manufacturing method of the RFLDMOS device according to the embodiment of the present invention;

FIG. 11 shows a schematic diagram of an RFLDMOS device according to an embodiment of the present invention.

Detailed ways

The present invention is described below based on examples, but the present invention is not limited to these examples only. In the following detailed description of the invention, some specific details are described in detail. The present invention can be fully understood by those skilled in the art without the description of these detailed parts. Well-known methods, procedures, procedures, components and circuits have not been described in detail in order to avoid obscuring the essence of the present invention.

Furthermore, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.

Unless clearly required by the context, words such as "including", "comprising" and the like throughout this application should be construed in an inclusive rather than an exclusive or exhaustive sense; that is, in the sense of "including but not limited to".

In the description of the present invention, it should be understood that the terms "first", "second" and the like are used for descriptive purposes only, and should not be construed as indicating or implying relative importance. Also, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

The RFLDMOS device adopts the structure of the multi-layer Faraday shield, which can further uniformize the field intensity distribution in the drift region, reduce the electric field at the gate-drain fringe, and improve the breakdown voltage of the device. However, its manufacturing process is relatively complicated. Each additional layer of Faraday shield requires additional process steps such as photolithography, deposition of metal, deposition of insulating dielectric materials, stripping, cleaning, etc. The insulating dielectric material has a suitable thickness, and tedious process debugging must be carried out, which greatly increases the difficulty and cost of device manufacturing and reduces the yield of the device. Therefore, the present invention provides an RFLDMOS device and a manufacturing method thereof. The technical solutions of the present invention are further described below with reference to the accompanying drawings and through specific embodiments.

FIG. 3 is a flowchart of a method for fabricating an RFLDMOS device according to an embodiment of the present invention. As shown in Figure 3, it includes the following steps:

Step 1, providing a substrate 101 , forming an epitaxial layer 102 on the substrate 101 , and growing a thick gate oxide layer 103 on the epitaxial layer 102 .

In the embodiment of the present invention, the substrate 101 is N-type, or the substrate 101 is P-type. A P-type epitaxial layer is grown on a P-type substrate, or an N-type epitaxial layer is grown on an N-type substrate. Preferably, the thick gate oxide layer 103 is grown with a furnace tube.

Step 2, as shown in FIG. 4 , the source region formation region, the partial gate formation region adjacent to the source and the drift region formation region adjacent to the gate are opened by photolithography.

The photoresist (PR) opens the source end and the part close to the source end for making the polysilicon gate region, and the part close to the gate for making the drift region region.

Step 3, as shown in FIG. 5 , use a wet etching process to remove the thick gate oxide layer 103 in the lithographically opened area, and form undercuts at both ends of the remaining thick gate oxide layer 103 .

In the embodiment of the present invention, an undercut is formed between the photoresist PR and the thick gate oxide layer 103 by wet etching (the undercut is shown in the dotted circle in the figure), and the undercut of the thick gate oxide layer 103 is formed after the undercut. The shape becomes two isosceles trapezoids spaced apart on the epitaxial layer 102 .

Step 4, as shown in FIG. 6 , a thin gate oxide layer 104 is grown on the epitaxial layer 102 , and the thin gate oxide layer 104 and the thick gate oxide layer 103 together form a stepped gate oxide layer 105 .

A thin gate oxide layer 104 is regrown. The thicknesses of the thin gate oxide layer 104 and the thick gate oxide layer 103 are not limited in the embodiments of the present invention, and the thicknesses required in the actual process shall prevail. After the above steps 1 to 4, a stepped gate oxide layer 105 is formed on the surface of the epitaxial layer.

Step 5, as shown in FIG. 7 , polysilicon is deposited and a gate 106 is formed in the gate formation region by photolithography.

In the embodiment of the present invention, the gate 106 is formed above the gate oxide layer 105 in the gate formation region at the slope, and the upper left corner of the gate is stepped. .

Step 6, as shown in FIG. 8 , a body region 107 and a drift region 108 are formed in the epitaxial layer 102 .

The body region 107 and the drift region 108 of the RFLDMOS device are respectively formed in the epitaxial layer 102 by a photolithography process and an ion implantation process.

Step 7, as shown in FIG. 8 , the gate spacers are formed, the heavily doped region 109 and the source region 110 are formed in the body region 107 , and the drain region 111 is formed in the drift region 108 .

The heavily doped region and the source region of the RFLDMOS are formed in the body region through the photolithography process and the ion implantation process, and the drain region of the RFLDMOS is formed in the drift. The drain region is located at the end of the drift region away from the body region.

Step 8, as shown in FIG. 8 , metal silicide 112 is formed on the source region 110 , the drain region 111 and the gate electrode 106 .

Open the source and drain regions and the gate area where metal silicide is required, and perform a metal silicide process. Of course, metal silicide 112 also exists on top of the heavily doped region 109 in other regions such as the body region 107 .

Step ninth, as shown in FIG. 9 , a dielectric layer 113 is deposited, and the dielectric layer 113 covers the body region 107 , the drift region 108 and the top of the gate electrode 106 .

In the embodiment of the present invention, the dielectric layer 113 is a silicon oxide layer. Due to the formation of the stepped gate oxide layer in step 4, the dielectric layer 113 covered subsequently is also stepped as shown in the figure.

In step ten, a Faraday shielding layer is deposited on the dielectric layer 113 .

In the embodiment of the present invention, the material of the Faraday shielding layer is tungsten silicon or titanium nitride.

Step eleven, as shown in FIG. 10 , a Faraday shield 114 is formed over the portion of the gate close to the drain region and over the portion of the drift region close to the gate using a photolithography process.

In the embodiment of the present invention, due to the formation of the stepped gate oxide layer in step 4, the dielectric layer 113 and the Faraday shield 114 covered subsequently are all stepped. Compared with the simple stepped Faraday shield structure of the traditional RFLDMOS device, the stepped structure of the embodiment of the present invention improves the hot carrier performance while taking into account the breakdown voltage, reduces the ground resistance of the Faraday shield, and effectively improves the Broadband performance and reliability at high frequencies of the device.

The manufacturing method of the semiconductor device according to the embodiment of the present invention further includes: step 12, forming a sinking through hole, the bottom of the sinking through hole is located in the substrate, and the sinking through hole penetrates the body region and the epitaxial layer.

FIG. 11 shows a schematic diagram of an RFLDMOS device according to an embodiment of the present invention. As shown in FIG. 11 , it includes a substrate 101 , an epitaxial layer 102 located above the substrate, a drift region 108 and a body region 107 disposed in the epitaxial layer 102 , and a drain region 111 disposed in the drift region 108 and disposed in the body region The heavily doped region 109 and the source region 110 in 107, the stepped gate oxide layer 105 located above the epitaxial layer 102, and the gate structure located on the surface of the epitaxial layer, the gate structure includes the gate oxide layer 105, the gate 106 and Gate spacers, metal silicide 112 over source region 110, drain region 111 and gate 106, overlying body region 107, drift region 108 and dielectric layer 113 on top of gate structure, Faraday shield 114 and sinker via hole 115.

In the embodiment of the present invention, the metal silicide 112 also exists on the top of the heavily doped region 109 in the body region 107 . The bottom of the sinking via 115 is located in the substrate, penetrating the body region and the epitaxial layer; the Faraday shield 114 covers the dielectric layer 113 and is located above the part of the gate close to the drain region and the part of the drift region close to the gate.

In the embodiment of the present invention, the gate oxide layer 105 in the gate structure has a slope under the gate, and the thickness of the gate oxide layer on the side of the drain region is larger than that on the side of the source region. The Faraday shield 114 is stepped.

The RFLDMOS device according to the embodiment of the present invention does not need to perform a photolithography etching process to form a double-layer Faraday shield, so as to achieve the effect of further optimizing the reliability and frequency of the device, and greatly reduce the process complexity and cost.

It should be understood that many other layers may also be present, such as spacer elements and/or other suitable components, which have been omitted from the illustration for simplicity.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. a manufacturing method of RFLDMOS device, is characterized in that, comprises the following steps: Step 1, providing a substrate, forming an epitaxial layer on the substrate, and growing a thick gate oxide layer on the epitaxial layer; Step 2, photolithography opens the source region formation region, the partial gate formation region close to the source, and the gate drift region formation region; Step 3, using a wet etching process to remove the thick gate oxide layer in the lithography open area, and form undercuts at both ends of the remaining thick gate oxide layer; Step 4, growing a thin gate oxide layer above the epitaxial layer, and the thin gate oxide layer and the thick gate oxide layer together form a stepped gate oxide layer; Step 5, depositing polysilicon and forming a gate in the gate formation region by using a photolithography etching process; Step 6, forming a body region and a drift region in the epitaxial layer; Step 7, forming gate sidewalls, forming a heavily doped region and a source region in the body region, and forming a drain region in the drift region; Step 8, forming metal silicide on the source region, the drain region and the gate; Step 9, depositing a dielectric layer, the dielectric layer covering the body region, the drift region and the top of the gate; Step ten, depositing a Faraday shielding layer on the dielectric layer; Step 11, forming a Faraday shield over a portion of the gate close to the drain region and over a portion of the drift region close to the gate using a photolithography process. 2 . The method for manufacturing an RFLDMOS device according to claim 1 , wherein in step 1, the substrate is N-type, or the substrate is P-type. 3 . 3. The method for manufacturing an RFLDMOS device according to claim 1, wherein the shape of the thick gate oxide layer after the undercut is formed in step 3 becomes two isosceles trapezoids spaced apart on the epitaxial layer . 4 . The method for manufacturing an RFLDMOS device according to claim 1 , wherein in step 5, the upper left corner of the gate is stepped. 5 . 5 . The method for manufacturing an RFLDMOS device according to claim 1 , wherein the dielectric layer in step 9 is a silicon oxide layer. 6 . 6 . The method for manufacturing an RFLDMOS device according to claim 1 , wherein the material of the Faraday shielding layer in step ten is tungsten silicon or titanium nitride. 7 . 7 . The method for manufacturing an RFLDMOS device according to claim 1 , wherein the Faraday shield in step 11 is a stepped type. 8 . 8 . The method for manufacturing an RFLDMOS device according to claim 1 , wherein the method further comprises: forming a sinking through hole, the bottom of the sinking through hole is located on the substrate, and the sinking through hole is located at the substrate. 9 . through the body region and the epitaxial layer. 9. A RFLDMOS device formed by using the manufacturing method of the RFLDMOS device according to any one of claims 1 to 8, characterized in that, comprising: substrate; an epitaxial layer located above the substrate; a drift region and a body region are arranged in the epitaxial layer; a drain region is arranged in the drift region, a heavily doped region and a source region are arranged in the body region, and the a heavily doped region is connected to the source region; a stepped gate oxide layer located above the epitaxial layer; a gate structure located on the surface of the epitaxial layer, the gate structure comprising the gate oxide layer, a gate and a gate spacer; a metal silicide over the source region, the drain region and the gate; a dielectric layer covering the body region, the drift region and the top of the gate structure; a Faraday shield covering the dielectric layer and over a portion of the gate close to the drain region and over a portion of the drift region close to the gate; and a sinking through hole, the bottom of the sinking through hole is located in the substrate and penetrates the body region and the epitaxial layer; Wherein, the gate oxide layer in the gate structure has a slope under the gate, and the gate oxide layer on the side of the drain region is thicker than the gate oxide layer on the side of the source region; the Faraday shield is Ladder type.

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