Semiconductor device and manufacturing method thereof

Abstract

A semiconductor device includes a substrate, a plurality of fins on the substrate, and an isolation region between the fins. Each of the fins includes a semiconductor material region and an impurity region disposed in the semiconductor material region. The impurity region has an upper surface below an upper surface of the isolation region.

Claims

1. A semiconductor device comprising: a substrate; a plurality of fins on the substrate, each of the fins comprising a semiconductor material region and an impurity region sandwiched by a top portion of the semiconductor material region and a bottom portion of the semiconductor material region, wherein: the semiconductor material region includes a top semiconductor material region and a bottom semiconductor material region, and the top semiconductor material region and the bottom semiconductor material region are separated from each other by the impurity region, an isolation region between the fins, wherein a bottom surface of the impurity region is above a bottom surface of the isolation region, wherein the isolation region is formed in one step by a flowable chemical vapor deposition (FCVD) process, and a planar sidewall surface of the isolation region is in direct contact with a sidewall surface of the top portion of the semiconductor material region, a sidewall surface of the bottom portion of the semiconductor material region, and a sidewall surface of impurity region of each of the fins; and a well region in the substrate, wherein the well region and the impurity region have a same conductivity type, and a doping concentration of the well region is less than a doping concentration of the impurity region.

2. The semiconductor device of claim 1, wherein an upper surface of the impurity region is below an upper surface of the isolation region.

3. The semiconductor device of claim 1, wherein the impurity region forms a channel stop layer.

4. The semiconductor device of claim 1, wherein the same conductivity type comprises a P-type conductivity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a simplified flowchart of a method for manufacturing a semiconductor device according to an embodiment of the present invention.

(2) FIG. 2 is a cross-sectional view illustrating an intermediate stage of a manufacturing method according to the present invention.

(3) FIG. 3 is a cross-sectional view illustrating an intermediate stage of a manufacturing method according to the present invention.

(4) FIG. 4 is a cross-sectional view illustrating an intermediate stage of a manufacturing method according to the present invention.

(5) FIG. 5 is a cross-sectional view illustrating an intermediate stage of a manufacturing method according to the present invention.

(6) FIG. 6 is a cross-sectional view illustrating an intermediate stage of a manufacturing method according to the present invention.

(7) FIG. 7 is a cross-sectional view illustrating an intermediate stage of a manufacturing method according to the present invention.

(8) FIG. 8 is a cross-sectional view illustrating an intermediate stage of a manufacturing method according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(9) Embodiments of the present invention now will be described more fully hereinafter with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The features may not be drawn to scale, some details may be exaggerated relative to other elements for clarity. Like numbers refer to like elements throughout.

(10) It will be understood that when an element such as a layer, region or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present.

(11) Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “lateral” or “vertical” may be used herein to describe a relationship of one element, layer or region to another element, layer or region as illustrated in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.

(12) The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes”, and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

(13) Embodiments of the invention are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the invention. The thickness of layers and regions in the drawings may be enlarged relative to other layers and regions for clarity. Additionally, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a discrete change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the invention.

(14) Embodiments of the present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

(15) FIG. 1 is a simplified flowchart of a method for manufacturing a semiconductor device according to an embodiment of the present invention. Referring to FIG. 1, the method may include the following process steps:

(16) At 101: providing a substrate, such as a silicon substrate or other semiconductor substrate.

(17) At 103: forming an amorphous layer in the substrate. The amorphous layer advantageously prevents dopants (alternatively also referred to as impurities hereinafter) of a channel stop ion implantation from diffusing into a channel.

(18) At 105: performing a first etching process on the substrate using the amorphous layer as an etch stop layer to form one or more first fins.

(19) At 107: performing a channel stop ion implantation into the amorphous layer to form an impurity region in the amorphous layer. For example the implanted dopants or impurities can be boron or boron difluoride ions. The impurity region can be used as a channel stop layer.

(20) At 109: performing an annealing process to activate the impurities (implanted dopants) in the impurity region. The amorphous layer disappears during the annealing process. The annealing process can activate the impurities in the impurity region, and the impurities are not diffused outside the amorphous layer, thereby preventing the impurities of the channel stop ion implantation from diffusing into the channel. The annealing process also can repair the amorphous layer. The activation and diffusion of the implanted impurities and the repair of the amorphous layer can be performed simultaneously, thus, the amorphous layer can suppress the diffusion of the impurities into the channel.

(21) At 111: performing a second etching process on a portion of the substrate disposed between adjacent first fins to form a plurality of second fins from the first fins.

(22) At 113: forming an isolation region between adjacent second fins partially filling at least an air gap between the adjacent second fins. For example, the air gap between the second fins can be filled with an insulating material using a flowable chemical vapor deposition (FCVD) process to form a shallow trench isolation (STI) region.

(23) In the embodiment, since the channel stop ion implantation and the annealing process are first performed, and the isolation region is formed thereafter, during the annealing process the impurities (implanted dopants) in the impurity region are activated, however, due to the presence of the amorphous layer, the impurities are not diffused outside the amorphous layer. Thus, comparing with conventional techniques, the impurities of the channel stop ion implantation do not diffuse into the channel while forming the isolation region, thereby preventing punch through from occurring.

(24) It is noted that, as used herein, unless specifically stated otherwise, the terms “substantially coplanar” and “substantially flush” refer to surfaces that are sufficiently coplanar or flush within the process variation tolerance.

(25) FIGS. 2 through 8 are cross-sectional views illustrating intermediate stages of a method for manufacturing a semiconductor device according to an embodiment of the present invention.

(26) Referring to FIG. 2, a substrate 201 is provided. An amorphous layer is formed in the substrate. Substrate 201 may be a mono-crystalline silicon substrate, a germanium substrate, a substrate including a III-V group material, and the like. In a preferred embodiment, an ion implantation 203 of germanium ions or carbon ions is performed into the substrate to form an amorphous layer 202. The presence of amorphous layer 202 advantageously prevents the diffusion of implanted impurities of the channel stop implant into the channel. Furthermore, a well region, e.g., a P-well (not shown) may be formed in substrate 201.

(27) Thereafter, referring to FIG. 3, a patterned hardmask 300 is formed on substrate 201. The material of hardmask 300 may be silicon nitride, silicon oxide, silicon oxynitride and the like. A first etching process, e.g., a dry etching, is performing on the amorphous layer using the hardmask as a mask to form a plurality of first fins 301.

(28) Next, referring to FIG. 4, a channel stop ion implantation 403 is performed into amorphous layer 202 to form an impurity region 401. It is noted herein that impurity region 401 is integral with amorphous layer 202. Impurities of impurity region 401 are laterally diffused in amorphous layer 202. For example, for an NMOS device, boron ions or boron difluoride ions can be implanted into the amorphous layer to form an impurity region, which can serve as a channel stop layer. In some embodiments, the impurity region and the well region can have the same conductivity type, and the doping concentration of the well region is less than the doping concentration of the impurity region. For an NMOS device, a P-well may be formed in the substrate, the P-well and the impurity region may have P-type conductivity, and the doping concentration of the P-well region is less than the doping concentration of the impurity region.

(29) Next, referring to FIG. 5, an annealing process is performed to activate impurities in impurity region 401. Amorphous layer 202 disappears during the annealing process.

(30) Next, referring to FIG. 6, a second etching process is performing on a portion of the substrate disposed between adjacent first fins to remove the portion of the substrate and to form second fins. A first portion of impurity region 401 is also removed by the second etching process, so that the second fins include a second portion 401′ of impurity region 401.

(31) Next, referring to FIG. 7, an air gap region between the second fins is filled with an insulating material 701 using a flowable chemical vapor deposition (FCVD) process. Thereafter, a high-temperature annealing process is performed. Because impurities of impurity region 401 have been activated, therefore, the formation of the isolation region will not cause the impurity diffusion. Thereafter, a planarization, e.g., a chemical mechanical polishing (CMP) process, is performed on insulating material 701 so that the top surface of insulation material 701 is substantially flush with the top surface of hardmask 300, as shown in FIG. 7.

(32) Next, referring to FIG. 8, insulating material 701 is etched back to expose at least a portion of second fins 601. Hardmask 300 is then removed, thereby forming a second isolation region 801 between adjacent second fins 601.

(33) A semiconductor device 800 is thus formed as shown in FIG. 8. Referring to FIG. 8, semiconductor device 800 includes a substrate 201, a plurality of fins 601, and an isolation region 801 disposed between adjacent fins 601.

(34) Each of the fins 601 includes a semiconductor material region 201′ and an impurity region 401′ within the semiconductor material region. Impurity region 401 may be used to form a channel stop layer. In a preferred embodiment, the upper surface of impurity region 401 is below the upper surface of isolation region 801. In one embodiment, a well region (not shown) is formed in substrate 201. The well region and impurity region 401′ have the same conductivity type, and the doping concentration of the well region is less than the doping concentration of impurity region 401.

(35) The foregoing descriptions of specific embodiments of the present invention have been presented for purpose of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above disclosure. The exemplary embodiment has been described in order to best explain the principles of the invention and its practical application. Many embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.