CN113223945A - Manufacturing method of transverse variable doping structure and transverse power semiconductor device - Google Patents

Manufacturing method of transverse variable doping structure and transverse power semiconductor device Download PDF

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CN113223945A
CN113223945A CN202110469366.3A CN202110469366A CN113223945A CN 113223945 A CN113223945 A CN 113223945A CN 202110469366 A CN202110469366 A CN 202110469366A CN 113223945 A CN113223945 A CN 113223945A
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CN113223945B (en
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韩广涛
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Joulwatt Technology Co Ltd
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Abstract

The invention discloses a manufacturing method of a transverse variable doping structure and a transverse power semiconductor device, wherein the manufacturing method of the transverse variable doping structure comprises the following steps: forming a pad oxide layer on a substrate; performing local thermal oxidation on the substrate below the liner oxide layer to generate a field oxide layer comprising a bird's beak region, wherein the thickness of the oxide layer of the bird's beak region is transversely gradually changed; and implanting doping ions into the substrate below the bird's beak region above the bird's beak region. The invention can enable the small-size lateral power semiconductor device to have a better lateral variable doping effect.

Description

Manufacturing method of transverse variable doping structure and transverse power semiconductor device
Technical Field
The invention relates to the technical field of semiconductors, in particular to a manufacturing method of a transverse variable doping structure and a transverse power semiconductor device.
Background
The transverse variable doping structure is a semiconductor structure with impurity ions in quantity which is transversely and gradually changed in the substrate, and has a very remarkable effect of improving the breakdown voltage of a transverse power semiconductor device.
The Lateral Variation Doping (VLD) is a manufacturing technique of the Lateral Variation Doping structure, and fig. 1 shows a process implementation manner and an effect diagram of the conventional VLD. Referring to fig. 1, the conventional VLD technique performs implantation of impurity ions into a target region 112 of a substrate 110 through a plurality of windows formed over the substrate 110 by photoresist, and then connects the impurity ions by high temperature annealing to finally form a laterally varying profile. In practice, the size and the spacing of the windows are adjusted to enable the target region 112 below each window to form an initial ion distribution shown by an envelope curve, and then the target region is subjected to long-time high-temperature annealing and junction pushing to achieve a preset lateral variable doping effect shown by a dotted line.
However, in the application process of the VLD technology, the ion implantation window is as many as several tens, the optimization process of design of parameters such as the size and the spacing of the window is extremely long, and the size and the spacing of the window are difficult to be accurately controlled due to the appearance of the photoresist and the existing precision of the related photolithography process; especially in the case of window size and pitch shrinking with device size reduction, the final doping effect of the conventional VLD technique is more difficult to control, which limits the application range of the lateral doping structure.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a method for manufacturing a variable doping structure and a lateral power semiconductor device, so that the lateral power semiconductor device with a small size has a better lateral variable doping effect.
According to a first aspect of the present invention, there is provided a method for manufacturing a laterally variable doped structure, comprising:
forming a pad oxide layer on a substrate;
performing local thermal oxidation on the substrate below the liner oxide layer to generate a field oxide layer comprising a bird's beak region, wherein the thickness of the bird's beak region oxide layer is laterally gradually changed;
and implanting doping ions into the substrate below the bird's beak region above the bird's beak region.
Optionally, performing a local thermal oxidation on the substrate below the pad oxide layer to generate a field oxide layer including a bird's beak region, including:
forming a shielding layer on the pad oxide layer;
etching the shielding layer to form a local thermal oxidation window;
and carrying out local thermal oxidation on the substrate in a region of the pad oxide layer exposed by the local thermal oxidation window, and growing a field oxide layer, wherein the field oxide layer extends to form the bird's beak region in a region below the shielding layer.
Optionally, implanting dopant ions into the substrate below the bird's beak region includes:
removing the shielding layer;
forming a mask layer above the pad oxide layer without growing a field oxide layer and above the field oxide layer, wherein the mask layer is provided with an ion implantation window in the beak region;
and implanting doping ions into the substrate above the mask layer so that the doping ions are implanted into the substrate below the bird's beak region through the ion implantation window.
Optionally, the bird's beak region comprises a first region located at the left side of the local thermal oxidation window and a second region located at the right side of the local thermal oxidation window, wherein the thickness of the first region in the lateral direction increases from left to right, and the thickness of the first region in the lateral direction decreases from left to right;
the mask layer is provided with the ion implantation window in the first area, or the mask layer is provided with the ion implantation window in the second area.
Optionally, forming a mask layer over the pad oxide layer and over the field oxide layer without growing a field oxide layer, including:
coating photoresist on the gasket oxide layer without growing a field oxide layer and on the field oxide layer;
and removing the part of the photoresist above the bird's beak region through exposure, development and etching treatment to form the ion implantation window.
Optionally, implanting dopant ions into the substrate over the mask layer includes:
acquiring the maximum thickness of the beak area;
determining the implantation energy and implantation dosage of the doping ions according to the maximum thickness so that the doping ions can completely penetrate through the bird's beak region with the laterally-graded whole thickness;
and implanting the doping ions into the substrate above the mask layer based on the determined implantation energy and the determined implantation dosage.
Optionally, the shielding layer is a nitride.
Optionally, the substrate is a semiconductor material of a first conductivity type, and the dopant ions are dopant ions of the first conductivity type;
or, the substrate is a semiconductor material of a first conductivity type, the doping ions are doping ions of a second conductivity type, and more ions of the first conductivity type are implanted in each region of the substrate.
Optionally, after implanting doping ions into the substrate below the bird's beak region, the manufacturing method further includes: and carrying out knot pushing on the doped ions implanted in the substrate.
According to a second aspect of the present invention, there is provided a lateral power semiconductor device comprising a lateral variable doping structure, wherein the lateral variable doping structure is prepared by any one of the manufacturing methods of the first aspect.
The embodiment of the invention has the following beneficial effects:
the manufacturing method of the transverse variable doping structure provided by the invention carries out local thermal oxidation on a liner oxide layer formed on the substrate to generate a field oxide layer comprising a bird's beak region, wherein the thickness of the oxide layer of the bird's beak region is transversely changed, and the field oxide layer has a blocking effect on doping ion implantation, so that the region with the transversely changed thickness has different degrees of blocking on the doping ion implantation, and after doping ions are implanted into the substrate below the bird's beak region above the bird's beak region, the substrate below the bird's beak region forms the transverse variable doping structure. The manufacturing method of the transverse variable doping structure realizes the transverse variable doping effect by combining the local thermal oxidation technology and the ion implantation technology, and is suitable for arranging the transverse variable doping structure on a small-size transverse power semiconductor device because the complicated design process and the high-precision photoetching process of a plurality of photoresist windows are saved; moreover, only a simple thermal process is needed to ensure that the impurity ions are distributed more uniformly in the longitudinal direction, so that a high-temperature (about 1200 ℃) long-time (about 10 hours) thermal process carried out by the traditional VLD technology is not needed to push the junction, and the thermal budget is greatly reduced; it should be noted that when the substrate longitudinal thickness is thin enough, the junction pushing time can be further reduced or even omitted.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:
FIG. 1 shows a diagram of a process implementation of a conventional VLD and its effects;
FIG. 2 shows a flow chart of a manufacturing method in a first embodiment of the invention;
FIGS. 3, 4 and 5 show a process implementation of the manufacturing method in a first embodiment of the invention;
fig. 6 and 7 show laterally varied doping structures in two different directions based on the manufacturing method in the first embodiment of the invention.
Detailed Description
Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by the same or similar reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. In addition, certain well known components may not be shown. For simplicity, the semiconductor structure obtained after several steps can be described in one figure.
Fig. 2 shows a flow chart of a method for manufacturing a laterally varied doping structure according to a first embodiment of the invention. Referring to fig. 2, the method for manufacturing the lateral variation doping structure includes:
step S110, forming a pad oxide layer on a substrate;
step S120, performing local thermal oxidation on the substrate below the pad oxide layer to generate a field oxide layer including a bird 'S beak region, wherein the thickness of the oxide layer of the bird' S beak region is laterally gradually changed;
in step S130, doping ions are implanted into the substrate below the bird 'S beak region above the bird' S beak region.
Fig. 3, 4 and 5 show process implementations of the manufacturing method, and the above steps are described in detail below with reference to fig. 3 to 5.
Referring to fig. 3, a pad oxide layer 220 is formed on a substrate 210 in step S110.
The substrate 210 may be divided into a first region 211 and a second region 212 according to a lateral power semiconductor device with a preset lateral variable doping structure, where the first region 211 and the second region 212 are made of semiconductor materials with different conductivity types, for example, the first region 211 is made of N-type silicon and the second region 212 is made of P-type silicon, or the first region 211 is made of P-type silicon and the second region 212 is made of N-type silicon. In the present invention, the second region 212 is a predetermined region where a laterally varying doping structure is provided.
Referring to fig. 4, in step S120, the substrate 210 under the pad oxide layer 220 is locally thermally oxidized to generate a field oxide layer including a bird' S beak region.
It should be noted that the local thermal oxidation is to oxidize the substrate 210, and illustratively, the substrate 210 is silicon, and the field oxide layer is correspondingly silicon dioxide. It should be emphasized that, since the local thermal oxidation is to oxidize the substrate 210 to generate the field oxide layer, the pad oxide layer 220 and the field oxide layer belong to the oxide layer, which is exemplarily silicon dioxide; and, the substrate 210 is affected by the diffusion reaction of oxygen atoms in the direction parallel to the interface of the substrate 210 and the pad oxide 220 during the local thermal oxidation reaction, and gradually expands and forms a field oxide layer including a bird's beak region in combination with the original portion of the pad oxide 220, wherein the field oxide layer includes the oxidized portion of the substrate 210 and the portion of the pad oxide 220 located above the portion.
In particular, combine FIG. 3 withFig. 4, step S120, performing local thermal oxidation on the substrate 210 under the pad oxide layer 220 to generate a field oxide layer including a bird' S beak region, including: forming a shielding layer 230 on the pad oxide layer 220 and etching the shielding layer 230 to form a line D1And line D2A local thermal oxidation window in between; the substrate 210 under the pad oxide layer 220 is locally thermally oxidized by oxygen diffusion under the pad oxide layer 220 in a region where the pad oxide layer 220 is exposed by the local thermal oxidation window, a field oxide layer is grown, and the finally grown field oxide layer includes not only the field oxide layer located at the dotted line B1And the dotted line B2Between the field oxide layers, and further includes a dotted line a extending below the shield layer 2301And the dotted line B1And in between and at the dotted line a2And the dotted line B2A field oxide layer in between, wherein, located at the dotted line B1And the dotted line B2The field oxide layers between the two layers fully contact with diffused oxygen to react due to the fact that all parts of the substrate material under the local thermal oxidation window are in contact with the diffused oxygen, and therefore the volume of the field oxide layers is expanded uniformly and greatly; at the point line A1And the dotted line B1With the field oxide layer therebetween, the farther away from the local thermal oxide window, the less oxygen atoms are contacted, the less significant the volume expansion, thereby forming a dotted line B1To the point line A1A shape of decreasing thickness of (a); at the point line A2And the dotted line B2The field oxide layer in between is formed in principle with reference to the shape at the dotted line a1And the dotted line B1A field oxide layer in between. The above-mentioned position is located at the point line A1And the dotted line B1The field oxide layer in between is marked as the first region, and is located at the dotted line A2And the dotted line B2The field oxide layer between the first and second regions is marked as a second region, namely a bird's beak region.
Due to the bird's beak region, a portion of the shielding layer 230 adjacent to the local thermal oxidation window is lifted up by stress to conform to the shape of the bird's beak region. The shielding layer 230 is made of nitride, and is illustratively silicon nitride.
It should be understood that the position of the above-mentioned local thermal oxidation window is determined according to the preset position of the laterally varied doping structure, i.e. the starting position of the laterally varied doping structure is set as the edge position of the local thermal oxidation window.
Referring to fig. 5, in step S130, doping ions are implanted into the substrate 210 below the bird 'S beak region above the bird' S beak region, including: removing the shielding layer 230; forming a mask layer 240 over the oxide layers (including the liner oxide layer without grown field oxide layer and the grown field oxide layer), wherein the mask layer 240 is provided with an ion implantation window in the bird's beak region (located in dotted line a in fig. 5)1And the dotted line B1In (d) of (a); dopant ions are implanted into the substrate 210 above the mask layer 230 such that the dopant ions are implanted through the ion implantation window into the substrate 210 below the bird's beak region.
It should be noted that fig. 5 is to implant dopant ions into the substrate 210 under the first region, and thus corresponds to the point line a1And the dotted line B1An ion implantation window is provided therebetween. In some other embodiments, dopant ions may be implanted into the substrate 210 under the second region, thereby correspondingly forming a point line A2And the dotted line B2An ion implantation window is arranged between the two.
The above-mentioned forming mask layer above the liner oxide layer and above the field oxide layer of not growing field oxide layer includes: coating photoresist on the pad oxide layer without growing a field oxide layer and on the field oxide layer; and removing the part of the photoresist above the bird's beak region through exposure, development and etching treatment to form an ion implantation window.
The implanting of the dopant ions into the substrate 210 above the mask layer 240 includes: acquiring the maximum thickness of the beak area; determining the implantation energy and implantation dosage of the doping ions according to the maximum thickness so that the doping ions can completely penetrate through the bird's beak region with the whole thickness being transversely gradually changed; above the mask layer 240, dopant ions are implanted into the substrate 210 based on the determined implantation energy and implantation dose. In this process, the doping ions are implanted into the substrate 210 below the bird's beak region, but the thickness of the bird's beak region is laterally graded, so that the substrate 210 below the bird's beak region forms a laterally graded doping structure.
In an alternative embodiment, the substrate 210 is a semiconductor material of the first conductivity type (i.e., the second region 212 is a semiconductor material of the first conductivity type), and the dopant ions are dopant ions of the first conductivity type. In this example:
(1) the dopant ions implanted into the substrate 210 below the first region through the ion implantation window are from the dotted line a1To the point line B1With a decreasing amount, the laterally varied doping structure (located in dotted line A) in the substrate 2101And the dotted line B1In between) is also from dotted line a as shown in fig. 61To the point line B1The trend of gradually reducing the number of the doping ions is shown (namely a lateral variable doping structure with the gradually reduced number of the doping ions from left to right);
(2) the dopant ions implanted into the substrate 210 below the second region through the ion implantation window are from the dotted line B2To the point line A2The lateral doping profile in the substrate 210 is also from the dotted line B in an increasing amount2To the point line A2A trend of increasing the number of doping ions (i.e., a lateral varying doping structure with increasing number from left to right) is shown.
In another alternative embodiment, the substrate 210 is a semiconductor material of a first conductivity type (i.e., the second region 212 is a semiconductor material of a first conductivity type), and the dopant ions are dopant ions of a second conductivity type; and, more ions of the first conductivity type are implanted in each region of the substrate 210 than dopant ions are implanted. In this example:
(1) the dopant ions implanted into the substrate 210 below the first region through the ion implantation window are from the dotted line a1To the point line B1In decreasing amounts, however, these dopant ions compensate for the first conductivity type ions in the substrate 210, and finally form the dotted line A in the substrate 210 as shown in FIG. 71To the point line B1A lateral variable doping structure in between, and the lateral variable doping structure is an ion of the first conductivity type from the dotted line a1To the point line B1The number of the doped ions is gradually increased (namely, a lateral variable doping structure with the gradually increased number of the doped ions from left to right);
(2) the dopant ions implanted into the substrate 210 under the second region through the ion implantation window are from the dotted line a1To the point line B1The amount of the dopant ions increases, but the dopant ions compensate for the first conductivity type of the ions in the substrate 210, and finally the dotted line B is formed in the substrate 2102To the point line A2A laterally variable doping structure therebetween, and the laterally variable doping structure is a first conductivity type of ions from a dotted line B2To the point line A2With a gradual trend in number (i.e., a gradually lateral varying doping structure from left to right).
It should be noted that the laterally varied doping structures shown in fig. 6 and 7 and even fig. 1 all indicate a greater number of doping ions by a darker color.
Further, in step S130, after implanting doping ions into the substrate below the bird 'S beak region above the bird' S beak region, the method for manufacturing a lateral variable doping structure may further include: the doped ions implanted in the substrate 210 are pulled out so that the doped ions in the substrate 210 can be distributed more uniformly in the longitudinal direction. It is emphasized that, after step S130, the dopant ions in the substrate 110 have reached a relatively uniform lateral graded distribution by the blocking effect of the lateral graded beak region, so that the junction-pushing process herein only needs a process of substantially less than 10 hours to reach the desired state.
It should be understood that the dopant ions are only activated after being implanted into the substrate 210 at a high temperature, and thus the activation of the dopant ions should be performed after the above step S130. In some embodiments, the junction-pushing step may not be omitted, the doped ions in the substrate 210 are pushed after step S130, and the high-temperature activation process is synchronously implemented in the junction-pushing process. However, since the activation of the dopant ions is not an improvement of the present invention, it will not be described in detail here.
According to the manufacturing method of the transverse variable doping structure provided by the first embodiment of the invention, the transverse variable doping effect is realized by combining the local thermal oxidation process and the ion implantation technology, and the complicated design process and the high-precision photoetching process of a plurality of photoresist windows are omitted, so that the manufacturing method is suitable for arranging the transverse variable doping structure on a small-size transverse power semiconductor device; and the lateral gradient distribution of the doped ions is realized without depending on long-time high-temperature junction pushing, so that the junction pushing by a high-temperature (about 1200 ℃) long-time (about 10 hours) thermal process carried out by the traditional VLD technology is not needed, and the thermal budget is greatly reduced.
In response to the method for manufacturing the lateral variable doping structure provided in the first embodiment, a second embodiment of the present invention further provides a lateral power semiconductor device, which includes a lateral variable doping structure, and the lateral variable doping structure is manufactured by any one of the manufacturing methods provided in the first embodiment, so that the lateral power semiconductor device is not limited by size, has a good lateral variable doping effect, and the manufacturing cost is effectively reduced.
When a layer, a region, or a region is referred to as being "on" or "over" another layer, another region, or a region may be directly on or over the other layer, the other region, or another layer or a region may be included between the layer and the other layer or the other region. And, if the device is turned over, that layer, region, or regions would be "under" or "beneath" another layer, region, or regions.
If for the purpose of describing the situation directly on another layer, another region, the expressions "a is directly on B", "a is on and adjacent to B", "a is on and in contact with B", or "a is on the upper surface of B" will be used herein. In the present application, "a is directly in B" means that a is in B and a and B are directly adjacent, rather than a being in a doped region formed in B. Further, "a is located at the upper part of B" means that a is located in B and the top of a is exposed outside B.
Unless otherwise specifically noted above, various layers or regions of a semiconductor device may be composed of materials well known to those skilled in the art. Semiconductor materials include, for example, group III-V semiconductors such as GaAs, InP, GaN, and group IV semiconductors such as Si, Ge. The source, drain and gate electrodes and the gate conductive material may be formed of various conductive materials, such as a metal layer, a doped polysilicon layer, or a laminated conductor including a metal layer and a doped polysilicon layer, or other conductive materials, such as TaC、TiN、TaSiN、HfSiN、TiSiN、TiCN、TaAlC、TiAlN、TaN、PtSix、Ni3Si, Pt, Ru, W, and combinations of the various conductive materials. In the present application, the term "semiconductor structure" refers to the general term for the entire semiconductor structure formed in the various steps of manufacturing a semiconductor device, including all layers or regions that have been formed.
While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.

Claims (10)

1. A method for manufacturing a laterally variable doped structure, comprising:
forming a pad oxide layer on a substrate;
performing local thermal oxidation on the substrate below the liner oxide layer to generate a field oxide layer comprising a bird's beak region, wherein the thickness of the oxide layer of the bird's beak region is laterally gradually changed;
and implanting doping ions into the substrate below the bird's beak region above the bird's beak region.
2. The method of manufacturing of claim 1, wherein locally thermally oxidizing the substrate under the pad oxide to create a field oxide layer including bird's beak regions comprises:
forming a shielding layer on the pad oxide layer;
etching the shielding layer to form a local thermal oxidation window;
and carrying out local thermal oxidation on the substrate in a region of the pad oxide layer exposed by the local thermal oxidation window, and growing a field oxide layer, wherein the field oxide layer extends to form the bird's beak region in a region below the shielding layer.
3. The method of manufacturing of claim 2, wherein implanting dopant ions over the bird's beak region and into the substrate under the bird's beak region comprises:
removing the shielding layer;
forming a mask layer above the pad oxide layer without growing a field oxide layer and above the field oxide layer, wherein the mask layer is provided with an ion implantation window in the beak region;
and implanting doping ions into the substrate above the mask layer so that the doping ions are implanted into the substrate below the bird's beak region through the ion implantation window.
4. The manufacturing method according to claim 3,
the bird's beak region comprises a first region on the left side of the local thermal oxidation window and a second region on the right side of the local thermal oxidation window, wherein the thickness of the first region in the transverse direction is increased from left to right, and the thickness of the first region in the transverse direction is decreased from left to right;
the mask layer is provided with the ion implantation window in the first area, or the mask layer is provided with the ion implantation window in the second area.
5. The method of manufacturing of claim 3, wherein forming a mask layer over the pad oxide layer and over the field oxide layer without growing a field oxide layer comprises:
coating photoresist on the gasket oxide layer without growing a field oxide layer and on the field oxide layer;
and removing the part of the photoresist above the bird's beak region through exposure, development and etching treatment to form the ion implantation window.
6. The method of claim 3, wherein implanting dopant ions into the substrate over the mask layer comprises:
acquiring the maximum thickness of the beak area;
determining the implantation energy and implantation dosage of the doping ions according to the maximum thickness so that the doping ions can completely penetrate through the bird's beak region with the laterally-graded whole thickness;
and implanting the doping ions into the substrate above the mask layer based on the determined implantation energy and the determined implantation dosage.
7. The method of manufacturing according to claim 2, wherein the shielding layer is nitride.
8. The manufacturing method according to claim 1,
the substrate is made of semiconductor materials of a first conduction type, and the doped ions are doped ions of the first conduction type;
or, the substrate is a semiconductor material of a first conductivity type, the doping ions are doping ions of a second conductivity type, and more ions of the first conductivity type are implanted in each region of the substrate.
9. The method of manufacturing according to claim 1, further comprising, after implanting dopant ions above the bird's beak region toward the substrate below the bird's beak region: and carrying out knot pushing on the doped ions implanted in the substrate.
10. A lateral power semiconductor device comprising a lateral variable doping structure, wherein the lateral variable doping structure is manufactured by the manufacturing method of any one of claims 1 to 9.
CN202110469366.3A 2021-04-28 Manufacturing method of transverse variable doping structure and transverse power semiconductor device Active CN113223945B (en)

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