CN106206310A - The manufacture method of rf-ldmos semiconductor device - Google Patents

Abstract

The invention provides a method for manufacturing a radio frequency lateral double-diffused metal oxide semiconductor device, wherein the manufacturing method includes forming a thick oxide layer on the surface of the gate on the substrate and the surface of the substrate; etching the thick oxide layer to form a field oxide layer, Forming a field plate material layer on the field oxide layer, the field plate material layer including a third slope portion, a fourth slope portion and a second connection portion connected to the third slope portion and the fourth slope portion; etching the field plate material layer . The radio frequency lateral double-diffused metal oxide semiconductor device and its manufacturing method provided by the present invention form the field plate material layer including the third slope part and the fourth slope part, so that the third slope part and the fourth slope part are separated from the field oxide layer. The vertical distance is reduced, therefore, the subsequent etching of the field plate material layer is easier, and the residue caused by field plate etching in the prior art can be avoided, thereby reducing the problem of threshold voltage drift.

Description

Fabrication method of radio frequency lateral double diffused metal oxide semiconductor device

technical field

The invention relates to a semiconductor device technology, in particular to a manufacturing method of a radio frequency lateral double-diffused metal oxide semiconductor device.

Background technique

In the design of radio frequency lateral double-diffused metal oxide semiconductor devices, in order to improve the breakdown voltage of the device, the design of the field plate is essential. Field plate technology is a commonly used terminal technology to improve the surface withstand voltage of devices. It can effectively reduce the surface electric field of the reverse PN junction and improve the withstand voltage capability of the PN junction. That is, when the PN junction covered with a field plate is reversely biased, part of the power lines in the horizontal direction will terminate at the field plate in the vertical direction, thereby reducing the electric field strength in the horizontal direction and improving the breakdown resistance of the device.

1A-1B are schematic diagrams of the field plate structure of a radio frequency lateral double-diffused metal oxide semiconductor device in the prior art. As shown in FIG. 1A, the device includes a supporting substrate 101, a gate 102, and an oxide layer 103. In the prior art Among them, a field plate 104 needs to be formed on the surface of the substrate 101 and the gate 102, wherein the field plate 104 includes a horizontal portion 1041 and a vertical portion 1042, and the horizontal portion 1041 and the vertical portion 1042 are perpendicular to each other. Further, as shown in FIG. 1B , the field plate 104 needs to be etched.

However, in the subsequent etching process of the field plate 104, since the thickness of the vertical portion 1042 of the field plate, that is, the vertical distance H1 between the upper surface of the vertical portion 1042 of the field plate and the oxide layer 103 is thicker than the thickness of the horizontal portion 1041, During the etching process, after the horizontal portion 1041 is etched, the vertical portion 1042 is not etched. Therefore, the residual region 1043 is very easy to form, and the residual region 1043 will cause problems such as threshold voltage drift.

Contents of the invention

The purpose of the present invention is to provide a method for fabricating a radio frequency lateral double-diffused metal oxide semiconductor device, which is used to solve the problem that the field plate is easily left with a residual region in the process of etching the field plate in the prior art, which causes threshold voltage drift.

The invention provides a method for manufacturing a radio frequency lateral double-diffused metal oxide semiconductor device, comprising: forming a thick oxide layer on the surface of the gate on the substrate and the surface of the substrate; etching the thick oxide layer to form a field oxide layer, the field oxide layer includes a first slope portion, a second slope portion and a connection portion connected to the first slope portion and the second slope portion, the connection portion is located on the surface of the gate, and The first slope portion and the second slope portion are respectively located on both sides of the gate; a field plate is formed on the field oxide layer.

The method for fabricating a radio frequency lateral double-diffused metal oxide semiconductor device provided by the present invention comprises forming a field oxide layer including a first slope portion and a second slope portion, and further forming a third slope portion, a fourth slope portion on the surface of the field oxide layer. The field plate material layer of the slope portion reduces the vertical distance between the third slope portion and the fourth slope portion from the field oxide layer, so the subsequent etching of the field plate material layer is easier, and the field field in the prior art can be avoided. Residues caused by plate etch can reduce the problem of threshold voltage drift.

Description of drawings

FIG. 1 is a structural schematic diagram of a radio frequency lateral double-diffused metal oxide semiconductor device with a voltage divider structure in the prior art;

2 is a flowchart of a method for fabricating a radio frequency lateral double-diffused metal oxide semiconductor device according to an embodiment of the present invention;

3A-3E are structural schematic diagrams of various steps of manufacturing a radio frequency lateral double-diffused metal oxide semiconductor device according to Embodiment 2 of the present invention.

detailed description

Embodiment one

This embodiment provides a method for manufacturing a radio frequency lateral double-diffused metal oxide semiconductor device, as shown in FIG. 2 , which is a flowchart of a method for manufacturing a radio frequency lateral double-diffused metal oxide semiconductor device provided by an embodiment of the present invention. The manufacturing method of the radio frequency lateral double-diffused metal oxide semiconductor device includes:

Step 201, forming a thick oxide layer on the surface of the gate on the substrate and the surface of the substrate.

Wherein, the gate may be polysilicon.

The thick oxide layer can be formed by chemical vapor deposition, specifically low pressure, normal pressure or plasma chemical vapor deposition. In order to form a denser thick oxide layer, the thick oxide layer is preferably deposited by low pressure chemical vapor phase.

Step 202, etching the thick oxide layer to form a field oxide layer.

Wherein, the field oxide layer includes a first slope portion, a second slope portion and a first connection portion connected to the first slope portion and the second slope portion, the first connection portion is located on the surface of the gate, the first slope portion and the second slope portion The slope parts are respectively located on two sides of the gate.

Step 203, forming a field plate material layer on the field oxide layer.

Specifically, chemical vapor deposition can be used to form a field plate material layer on the surface of the field oxide layer, so the shape of the field plate material layer is similar to that of the field oxide layer, that is, the field plate material layer includes a third slope, a fourth slope and The second connecting portion connected to the third slope portion and the fourth slope portion, wherein the third slope portion is located on the surface of the first slope portion of the field oxide layer, the fourth slope portion is located on the surface of the second slope portion of the field oxide layer, and the third slope portion is located on the surface of the second slope portion of the field oxide layer. The second connection part is located on the surface of the first connection part of the field oxide layer.

Step 204, etching the field plate material layer to form a field plate.

In the method for fabricating a radio frequency lateral double-diffused metal oxide semiconductor device in this embodiment, a field oxide layer including a first slope portion and a second slope portion is formed, and a field oxide layer including a third slope portion and a second slope portion is further formed on the surface of the field oxide layer. A field plate material layer with four slopes, so that the vertical distance between the third slope and the fourth slope and the field oxide layer is reduced, where it should be noted that the vertical distance refers to the third slope or the fourth slope The vertical distance from the upper surface to the upper surface of the field oxide layer, therefore, the subsequent etching of the field plate material layer is easier, and the residue caused by the field plate etching in the prior art can be avoided, thereby reducing the problem of threshold voltage drift.

Embodiment two

As shown in FIGS. 3A to 3E , FIGS. 3A-3E are schematic structural diagrams of various steps in fabricating a radio frequency lateral double-diffused metal oxide semiconductor device. This embodiment is also a further supplementary description of the above embodiments.

As shown in FIG. 3A , a thick oxide layer 3 is formed on the surface of the gate 2 on the substrate 1 and the surface of the substrate 1 .

Wherein, the substrate 1 includes a substrate 11, a body region 12, a source region 13, a drift region 14, a drain region 15, and a gate oxide layer 16, wherein the substrate 11 is a silicon substrate, and the silicon substrate is doped with impurities, and the impurities can be antimony or arsenic. The formation methods of the substrate 11 , the body region 12 , the source region 13 , the drift region 14 , the drain region 15 , and the gate oxide layer 16 are all in the prior art, and will not be repeated here. The thick oxide layer 3 is formed on the substrate 1 by chemical vapor deposition. Optionally, compared with the prior art, for example, the thickness of the thick oxide layer in the prior art is 1500 angstroms, then the radio frequency lateral The thickness of the thick oxide layer 3 of the double-diffused metal oxide semiconductor device is 3000-5000 angstroms, but the thickness is not limited thereto. The specific thickness can be changed according to the actual device requirements, as long as the thickness of the thick oxide layer 3 is ensured. The thickness may be 2-3 times of the prior art, and the purpose is to ensure the thickness of the field oxide layer formed by etching the thick oxide layer after etching the thick oxide layer 3 in the next step.

Further, as shown in FIG. 3B , the thick oxide layer 3 is etched to form a field oxide layer 4 .

Wherein, the specific method of forming the field oxide layer 4 is to etch the thick oxide layer 3 under the conditions of a vacuum degree of 100-300 mTorr and a magnetic field of 20-40 Gauss. Specifically, etching the thick oxide layer 3 also needs to add etching gas and inert gas. The specific etching gas can be selected according to the material of the thick oxide layer 3. For example, if the thick oxide layer 3 is silicon oxide, the etching gas Trifluoromethane, carbon tetrafluoride, etc. can be used, and the flow rate of the etching gas can be selected as 30-80 ml/min. The amount of the etching gas should not be too large, otherwise the oxide layer on the surface of the substrate 1 will be easily etched away , the etching time for etching the thick oxide layer 3 is 20 seconds to 80 seconds. The inert gas may be argon, and the flow rate is 40-150 ml/min.

The field oxide layer 4 includes a first slope portion 41, a second slope portion 42, and a first connection portion 43 connected to the first slope portion 41 and the second slope portion 42. The first connection portion 43 is located on the surface of the gate 2. A slope portion 41 and a second slope portion 42 are respectively located on two sides of the gate 2 . Wherein, the lengths of the first slope portion 41 , the first connecting portion 43 and the second slope portion 42 in the horizontal direction are equal to the length of the base 1 . As shown in FIG. 3B , the first slope portion 41 includes a first horizontal portion 410 and a first vertical portion 411 , and the second slope portion 42 includes a second vertical portion 421 and a second horizontal portion 422 . The first horizontal part 410 and the second horizontal part 422 are parts parallel to the base 1, the first vertical part 411 is connected between the first horizontal part 410 and the first connecting part 43, and the second vertical part 421 is connected to the first between the second horizontal portion 422 and the second connecting portion 43 . More specifically, the shape of the side of the first vertical portion 411 away from the grid 2 is arc-shaped, and the direction of arc bending is the direction away from the grid 2. Likewise, the second vertical portion 422 is away from the side of the grid 2. The shape of one side is also arc-shaped, and the arc-shaped bending direction is also the direction away from the gate 2 .

As shown in FIG. 3C, the field plate material layer 5 is formed on the field oxide layer 4 by chemical vapor deposition. Optionally, the field plate material layer 5 is any one of polysilicon, tungsten silicide, and titanium, with a thickness of 800 angstroms to 3000 angstroms. Between, the field plate material layer 5 includes a third slope portion 51, a fourth slope portion 52 and a second connecting portion 53 connected to the third slope portion 51 and the fourth slope portion 52, wherein, since the field plate material layer 5 is Formed by chemical vapor deposition, the thicknesses of the third inclined portion 51 , the fourth inclined portion 52 and the second connecting portion are equal, so the shape of the field plate material layer 5 is similar to that of the field oxide layer 4 .

In addition, since the field plate material layer 5 and the gate 2 are both conductors, if the field plate material layer 5 and the gate 2 are in contact, a short circuit will be caused, so the first connecting portion 43 can prevent the connection between the field plate material layer 5 and the gate 2. Further, since the gate oxide layer 16 is usually very thin, it is not enough to isolate the source region 13, the drift region 14 and the drain region 15 under the field plate material layer 5 and the gate oxide layer 16, therefore, the first horizontal portion 44 And the second horizontal part 45 can prevent the short circuit caused by the connection between the field plate material layer 5 and the source region 13 , the drift region 14 and the drain region 15 under the gate oxide layer 16 . In addition, when forming the field oxide layer 4 , the etching conditions need to be strictly controlled to prevent the first connection portion 43 , the first horizontal portion 410 , and the second horizontal portion 422 from being etched away.

Wherein, the third inclined portion 51 further includes a third vertical portion 511 and a third horizontal portion 510, the fourth inclined portion 52 includes a curved portion 521 and a fourth horizontal portion 520, and the third horizontal portion 510 and the fourth horizontal portion 520 are The part parallel to the base 1, the third vertical part 511 is connected between the third horizontal part 510 and the second connecting part 53, the first curved part 521 is connected between the fourth horizontal part 520 and the second connecting part 53, and further To be more specific, the shape of the side of the third vertical portion 511 away from the grid 2 is arc-shaped, and the direction of arc bending is the direction away from the grid 2. Similarly, the shape of the side of the curved portion 521 away from the grid 2 It is also arc-shaped, and the direction of arc-shaped bending is also the direction away from the gate 2 . Wherein, the shape of the third vertical portion 511 and the curved portion 521 can be an arc as shown in FIG. 3C , a triangle (not shown in the figure), or a sector (not shown in the figure). It can ensure that the vertical distance H between the third vertical portion 511 and the curved portion 521 of the field plate material layer 5 and the field oxide layer 4 is smaller than the vertical distance H1 between the vertical portion 1024 of the field plate and the oxide layer 103 in the prior art. The three vertical portions 511 and the curved portion 521 may also be in other shapes that can reduce the vertical distance H, which will not be listed here. Among them, since the dry etching process is anisotropic, it is easiest to etch the first vertical portion 411 and the second vertical portion 421 into an arc shape when etching the field oxide layer 4, that is, the third vertical portion The arc shape of the portion 511 and the curved portion 521 has the simplest process requirements, therefore, preferably, the third vertical portion 511 and the curved portion 521 are arc shaped.

As shown in FIGS. 3D-3E , the field plate material layer is etched to form a field plate.

Specifically, as shown in FIG. 3D, a photoresist layer 6 is formed on the field plate material layer 5, one end of the photoresist layer 6 is located above the gate 2, and the other end of the photoresist layer 6 is located on the side of the gate 2 , wherein the photoresist layer 6 is a photoresist layer after exposure and development. Further, as shown in FIG. 3E , the field plate material layer 5 is etched to form a field plate 50 having a bent portion 521 , and finally, the photoresist layer 6 is removed.

In the manufacturing method of the radio frequency lateral double-diffused metal oxide semiconductor device provided in this embodiment, the field oxide layer 4 including the first slope part 41 and the second slope part 42 is formed, and the field oxide layer 4 is further formed on the surface of the field oxide layer 4. The field plate material layer 5 of the third slope portion 51 and the fourth slope portion 52, so that the vertical distance between the third slope portion 51 and the fourth slope portion 52 and the field oxide layer is reduced, thus making the subsequent field plate etching easier Easy, the residue caused by the etching of the field plate in the prior art can be avoided, so the problem of threshold voltage drift can be reduced.

Embodiment Three

This embodiment also provides a radio-frequency lateral double-diffused metal-oxide semiconductor device, the structure of which is shown in Figure 3E. The radio-frequency lateral double-diffused metal-oxide semiconductor device provided in this embodiment can be based on the radio frequency The fabrication method of the lateral double-diffused metal-oxide semiconductor device will not be described in detail here, and please refer to the description of the fabrication method of the radio-frequency lateral double-diffused metal-oxide semiconductor device.

In the radio frequency lateral double-diffused metal oxide semiconductor device provided by this embodiment, since the field plate is composed of the third slope part 51, the fourth slope part 52 and the second slope part connected to the third slope part 51 and the fourth slope part 52 The field plate material layer 5 of the connection part 53 is etched, therefore, the etching difficulty of manufacturing the field plate 7 is reduced, and the residue caused by the etching of the field plate in the prior art is avoided, so that the voltage drift occurring in the world can be reduced The problem of improving the performance and output yield of the device.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (7)

1. A method for making a radio frequency lateral double-diffused metal oxide semiconductor device, characterized in that it comprises: forming a thick oxide layer on the gate surface on the substrate and on the surface of the substrate; etching the thick oxide layer to form a field oxide layer, the field oxide layer comprising a first slope portion, a second slope portion, and a first connecting portion connected to the first slope portion and the second slope portion, The first connection part is located on the surface of the gate, and the first slope part and the second slope part are respectively located on both sides of the gate; forming a field plate material layer on the field oxide layer, the field plate material layer including a third slope portion, a fourth slope portion, and a second connection portion connected to the third slope portion and the fourth slope portion; Etching the field plate material layer to form a field plate. 2. The method for fabricating a radio frequency lateral double-diffused metal oxide semiconductor device according to claim 1, wherein said forming a field oxide layer comprises: The thick oxide layer is etched under conditions of a vacuum of 100-300 mTorr and a magnetic field of 20-40 Gauss. 3 . The method for fabricating a radio frequency lateral double-diffused metal oxide semiconductor device according to claim 1 , wherein the thick oxide layer has a thickness of 3000 angstroms to 5000 angstroms. 4 . The method for fabricating a radio frequency lateral double-diffused metal oxide semiconductor device according to claim 1 , wherein the etching time for etching the thick oxide layer is 20 seconds to 80 seconds. 5. The method for fabricating a radio frequency lateral double-diffused metal oxide semiconductor device according to claim 1, wherein the first slope portion, the first connection portion and the second slope portion are horizontally The length is equal to the length of the base. 6. The method for fabricating a radio frequency lateral double-diffused metal oxide semiconductor device according to any one of claims 1-5, wherein said etching said field plate material layer to form a field plate comprises: forming a photoresist layer on the field plate material layer, one end of the photoresist layer is located above the grid, and the other end of the photoresist layer is located at the side of the grid; Etching the field plate material layer to form a field plate with a curved portion; removing the photoresist layer. 7 . The method for fabricating a radio frequency lateral double-diffused metal oxide semiconductor device according to claim 1 , wherein the field plate is any one of polysilicon, tungsten silicide, and titanium.