Prior to giving a description with respect to detailed embodiments, a description will now be given with respect to an outline of a method of applying a stress to a desired region on a back face side of a BOX layer of the present invention. Although there are a plurality of application methods, a common point among them is as follows. That is to say, a predetermined region on a back face side of a BOX layer is previously amorphized by utilizing an ion implantation method. Then, while the amorphized region is recrystallized by performing a heat treatment, a stress is applied from the outside to the amorphized region, so that the stress is left in the amorphized region on the back face side of the BOX layer.
Now, in a first stress applying method, a predetermined region on a back face side of a BOX layer is amorphized by implanting ions into a portion of the back face side of the BOX layer contacting an end face of an isolation trench in a state in which the isolation trench is previously formed. An outline of the first stress applying method will now be described with reference to
The control for the application direction of the strain is important from a viewpoint of an improvement in the performance of the transistor. For an N-channel metal oxide semiconductor (NMOS) transistor, a tensile strain is preferably applied in parallel with a current direction of a channel. In addition, for a P-channel metal oxide semiconductor (PMOS) transistor, conversely, a compressive strain is preferably applied in parallel with the current direction of the channel. Therefore, it is preferable to adopt processes for applying a different stress to each of the NMOS region and the PMOS region. While details will be described in later embodiments, the first stress applying method enables the above processes to be performed. The SiN etching stopper film 3 can arbitrarily change an application direction and a magnitude of a stress depending on its formation condition. Therefore, an SiN film which generates a tensile stress may be formed in the NMOS region, and an SiN film which applies a compressive stress may be formed in the PMOS region. When the SiN film which generates the tensile stress is desired to be firstly formed in the NMOS region, after formation of the SiN film in the NMOS region, the SiN film may be removed only from the PMOS region through a photolithography process. Also, similarly, after formation of the SiN film for applying the compressive stress in the PMOS region, the SiN film may be removed only from the NMOS region. During this process, there is no need for preparing any of excessive masks in addition to a normal process. In the normal process, a mask used to divide an active region into the NMOS region and the PMOS region is generally prepared for formation of a source/drain region. Thus, this mask may be utilized in this process. The same processes as those for a normal complementary metal oxide semiconductor (CMOS) can be used after completion of the isolation process.
In the second stress applying method, an isolation region, a gate electrode, and an offset spacer are formed by utilizing the normal method. After that, before a process for forming an extension region, the amorphization is performed for a supporting substrate on a back face side of a BOX layer in a self-align manner by utilizing an ion implantation method. An SOI layer of a source/drain region is also amorphized in the phase of the amorphization. However, as will be described in detail in the later embodiments, the crystalline of the SOI layer of a channel region is held. Thus, the crystalline of the source/drain region can also be recovered by performing the heat treatment. Next to the ion implantation for the amorphization, impurity ions are implanted into the extension region as well. During this process, for the NMOS transistor, a gate stress can be applied by implanting As ions into the gate as well. After that, a heat treatment is performed after formation of a liner film for stress application, thereby performing activation of the extension region and recrystallization of the back side portions of the SOI layer and the BOX layer. In this process, either the liner film or the gate applies the strain to the channel. Similarly to the first stress applying method, the stress applied from either the liner film or the gate can be separately controlled for the NMOS region and the PMOS region. After that, the liner film thus formed may be used as a gate sidewall film just as it is. Or, after removal of the liner film, a gate sidewall film may be newly formed. After completion of this process, the same processes as those in the normal CMOS can be used.
A projected range of the implanted ions, that is, a depth of the amorphized portion is preferably nearly equal to a gate length or about 2 times as large as the gate length when being measured from a back side interface of the BOX layer. In the substrate, for a semiconductor element, as an object of the present invention, normally, a thickness of the SOI layer falls within the range of 5 to 100 nm, and a thickness of the BOX layer falls within the range of 5 to 50 nm. For example, when the gate length is 40 nm, and the thickness of each of the SOI layer and the BOX layer is 10 nm, it is recommended that the depth of the ion implantation is set in the range of about 40 to about 80 nm from the back side interface of the BOX layer and is set in the range of about 60 to about 100 nm from a surface of the SOI layer. From a viewpoint of application of the stress, it may safely be said that it is better to perform the amorphization until the deeper portion is reached. On the other hand, from a viewpoint of avoidance of generation of crystal defects in the phase of recrystallization, it is desirable that the better, the shallower the portion which is amarphized is. Thus, when the balance between both the viewpoints is taken into consideration, the depth range as described above is suitable.
The ion species which are implanted in the amorphizing process are preferably the group IV elements from a standpoint of holding a carrier concentration of a semiconductor constant. The implantation of the ions of Si as the same material as that of the substrate makes it possible to efficiently perform only the amorphization. In addition, only either one of Ge ions or C ions can be implanted, or can be implemented together with the Si ions. When the Ge ions are implanted, the compressive stress can be applied to the region into which the Ge ions were implanted because an atomic radius of a Ge atom is larger than that of an Si atom. Thus, the process for implanting the Ge ions is suitable for the PMOS. On the other hand, when C ions are implanted, contrary to the above case, the tensile stress can be applied to the region into which the C ions were implanted. Thus, the process for implanting the C ions is suitable for the NMOS.
In order to obtain the maximum strain application effect, selection of a surface orientation and a current direction in the channel is also important. Although (100) oriented silicon is normally used in the channel, in order to enhance the performance while the compatibility with a circuit library which has been used until now is held, the selection of the surface orientation is important as first selection. In the case of the NMOS transistor in which the tensile strain is applied to the impurity ion-implanted region, the current direction in this case has a larger effect in a <100> crystal orientation than in a <110> crystal orientation. In the case of the PMOS transistor in which the compressive stress is applied to the impurity ions-implanted region, conversely, the current direction has a larger effect in the <110> crystal orientation than in the <100> crystal orientation. However, in the case of the PMOS transistor, the characteristics of a micro-transistor when the strain is hardly applied are more excellent in <100> rather than in <110>. Thus, the <100> crystal orientation is preferable when the strain is nearly equal to or lower than 2,000 MPa in the channel position having a less amount of strain applied thereto, and the <110> crystal orientation is preferable when the strain is equal to or larger than 2,000 MPa in the channel region. In the latter case, the channel direction is rotated between the NMOS transistor and the PMOS transistor by 450. The rotation of the channel direction is not desirable in terms of a circuit layout. Therefore, it is preferable that the <100> crystal orientation be used in a circuit in which the NMOS performance is regarded as important, and the <110> crystal orientation be used in a circuit such as an SRAM in which the balance between the NMOS transistor performance and the PMOS transistor performance is regarded as important.
When the performance is aimed at being improved to the maximum, a region may be formed in which a crystal orientation of the SOI layer is rotated by 45°, and this region, for example, may be used only in the PMOS transistor. This process can be attained as follows. That is to say, the SOI substrate in which the crystal orientation of the supporting substrate on the back face side of the BOX layer is rotated by 45° is used, and the original SOI layer (which is different in crystal orientation from the supporting substrate) is selectively removed in a portion in which that SOI region is intended to be formed. After that, a part of the BOX layer is opened, and a film having the same crystal orientation as that of the supporting substrate is epitaxially grown on the BOX layer by utilizing an epitaxial lateral overgrowth (ELO) method. As a result, the above-mentioned process can be attained. Note that, although a portion which is obtained by opening the part of the BOX layer becomes a seed crystal for the ELO process, if this portion is utilized in the form of the isolation region, no chip area is excessively consumed.
Moreover, when the NMOS region and the PMOS region are given the different crystal orientations, respectively, setting (110) as a surface orientation of the PMOS channel results in the largest performance enhancement being obtained. At this time, the channel direction is also preferably made to match the <110> crystal orientation. To sum up, for the channel surface orientation and the channel current direction in which the maximum performance can be expected, the tensile strain for the combination of the (100) surface orientation and the <100> crystal orientation is obtained in the NMOS transistor, and the compressive strain for the combination of the (110) surface orientation and the <110> crystal orientation is obtained in the PMOS transistor.
Note that, when a description is necessary in the detailed embodiments for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, the plurality of sections or embodiments have some connection with one another except for the case where they are especially stated clearly, but one is connected with changes, details and a supplementary explanation of a part or all of the other. In addition, when reference is made to the number of elements, or the like (including the number of constituent elements, numeric values, amounts, ranges and the like) in the following embodiments, the present invention is not intended to be limited to the specific number thereof except for the case where they are especially stated clearly and the case where they are clearly limited to the specific number in principles. Thus, the number of elements may be equal to or larger than a specific number or may be equal to or smaller than the specific number. Moreover, it goes without saying that in the following embodiments, constituent elements thereof (including constituent steps) are necessarily essential to the present invention except for the case where they are especially stated clearly and the case where they are thought to be clearly essential to the present invention in principles. Likewise, when in the following embodiments, reference is made to shapes and positional relationships of constituent elements or the like, elements or the like which are substantially approximate or similar to the shapes or the like of the constituent elements or the like are included in the present invention except for the case where they are especially stated clearly and the case where they are thought not to be clearly so in principles. This is also applied to the numeric values and range described above. In addition, the constituent elements which have the same functions in all the figures for explanation of the following embodiments are designated with the same reference numerals, respectively, and their repeated descriptions are omitted here for the sake of simplicity.
The detailed embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. It is to be understood that materials, conductivity types, manufacturing conditions and the like of portions are not intended to be limited to those described in the following embodiments of the present invention, and the various changes of the embodiments may be made.
A first embodiment of the present invention uses the first stress applying method described above.
An SOI substrate including an SOI layer 6 with 30 nm thickness and a BOX layer 4 with 10 nm thickness as shown in
Next, after an active region 2 is coated with a photoresist by utilizing the photolithography technique for forming an isolation trench 1, a part of the first and second SiN etching stopper films 9 and 13 is removed by utilizing a dry etching method.
Next, Si ions are implanted at an acceleration voltage of 50 keV at an angle of 25° when viewed from a direction vertical to a substrate surface. At this time, a range of the implanted species is about 70 nm. Si of a portion into which the Si ions are implanted with a dose of 1e15/cm2 is sufficiently amorphized.
Next, an SiO2 film 15 using a tetraethoxysilane (TEOS) raw material is formed over the whole surface, including the isolation trench 1, to have a thickness of 600 nm. Moreover, a densification heat treatment for an oxide film is performed at 1,100° C. for 30 minutes. In this process, the above-mentioned amorphized regions 14 are crystallized, and at the same time, desired stresses are applied to portions adjacent to the amorphized regions 14, respectively.
Hereinafter, after completion of the same processes as those of the normal case, a CMOS transistor is manufactured. These processes will now be described in brief. The SiO2 film 15 is polished until the first and second SiN etching stopper films 9 and 13 are exposed, and the first and second SiN etching stopper films 9 and 13 are then removed by utilizing the chemical etching method.
Subsequently, there are performed a process for forming an offset spacer 21, a process for forming an extension region 22, a process for forming a gate sidewall 23, and a process for epitaxially growing an Si elevated layer 25 on a source/drain region 24.
A semiconductor device according to a second embodiment of the present invention will be described in detail hereinafter with reference to
Next, a detailed description will now be given with respect to a third embodiment utilizing the second stress applying method, that is, the method of implanting the impurity ions into the supporting substrate on the back face side of the BOX layer in the self-align manner by using the gate electrode as the mask.
Next, an SiO2 film 15 using the TEOS raw material is formed over the whole surface, including the isolation trench 1, to have a thickness of 600 nm. Moreover, a densification heat treatment for an oxide film is performed at 1,100° C. for 30 minutes.
Next, the SiO2 film 15 is polished until the SiN etching stopper film 9 is exposed, and the remaining SiN etching stopper film 9 is then removed by utilizing the chemical etching method.
Before impurity ions are implanted in order to form an extension region 22, Si ions are implanted into a back face portion of the BOX layer 4 formed below a source/drain region 24 at an acceleration voltage of 60 keV at an angle of 600 by using the gate electrode 20 as a mask. Si of a portion into which the Si ions are implanted with a dose of 1e15/cm2 is sufficiently amorphized.
Next, a first SiN liner film 31 for generating a tensile stress, and a second SiN liner film 32 for generating a compressive stress are formed in the NMOS region and the PMOS region, respectively, in order to form gate sidewalls 23 by utilizing the same method as that shown in the first embodiment.
Hereinafter, the same processes as those in the first embodiment 1 will be performed. That is to say, subsequently, there is performed the process for epitaxially growing an Si elevated layer 25 on the source/drain region 24. Next, deep ion implantation for formation of the source/drain region 24 is performed, and a rapid heat treatment for activating the impurity is performed. In this process as well, the strains hardly change. Next, a part of the Si elevated layer 25 epitaxially grown on the source/drain region 24 is made to turn into an NiSi layer 26. At this time, since the gate 20 and the gate sidewall 23 portion are coated with the SiO2 film, no NiSi reaction occurs in the gate 20 and the gate sidewall 23 portion. Moreover, an SiN layer 27 which becomes an etching stopper when contact holes for the gate 20 and the source/drain region 24 are formed, and an interlayer insulating film 28 are formed. After that, the polycrystalline silicon film 18 in a gate electrode 20 portion is exposed by utilizing the CMP method, and the NiSi reaction is made to occur in the polycrystalline silicon film 18. At this time, an Ni film having a sufficient thickness is deposited, and a heat treatment is then performed for a suitable time, which results in that all the polycrystalline silicon film 18 of the gate electrode 20 portion turns into an NiSi layer 29. After completion of the formation of the NiSi layer 29, the excessive Ni film is removed and an additional interlayer insulating film 28 is formed to have a desired thickness. After that, a first wiring layer 30 is formed.
Next, after a photoresist mask is formed on a portion in which the NMOS region 10 is defined, Si ions are implanted vertically to the substrate surface at an acceleration voltage of 130 keV with a dose of 1e15/cm2. As a result, the SOI layer 6 only in the PMOS region 11 is amorphized.
Next, a photoresist mask for formation of an isolation trench 1 is formed, and the isolation trench 1 for an isolation region is formed by the same dry etching method as that in the first embodiment 1. All the opening portion and the crystal grain portion which have irregularities are removed in this process.
In a fifth embodiment, only points of difference from the fourth embodiment 4 will be described in detail hereinafter. Although a prepared substrate has the same film structure as that in the fourth embodiment, it is assumed that a surface orientation of the supporting substrate 7 is (100), and a surface orientation of the SOI layer 6 is (100). In addition, it is assumed that a crystal orientation of the supporting substrate 7 parallel with an orientation flat or a notch of the supporting substrate 7 is <110>, and a crystal orientation of the SOI layer 6 is <100>. All the subsequent processes are the same as those in the fourth embodiment. After completion of that process, in the NMOS region 10, a surface orientation of the channel becomes (100) and the channel direction matches <100>, and in the PMOS region 11, a surface orientation of the channel becomes (100) and the channel direction matches <110>. In this case, a layout of the transistors is set as shown in
When the insulated gate type semiconductor device according to each of the first to fifth embodiments of the present invention which have been described in detail so far is used in the electronic information apparatus or electronic computer having a logic circuit and the like mounted thereto, the power consumption of the electronic information apparatus or the electronic computer can be greatly reduced and also the processing performance thereof can be improved. Note that, the various inventions disclosed in the paragraph of “DETAILED DESCRIPTION OF THE INVENTION” which has been described so far are described in brief as follows.
The fully depleted type insulated gate field effect transistor includes at least the single crystal semiconductor thin film and the gate electrode, the single crystal semiconductor thin film being formed through the first insulating film formed on the semiconductor substrate, the gate electrode being formed through the second insulating film formed on the single crystal semiconductor thin film; and the stress applying region is formed within the semiconductor substrate on the back face side of the first insulating film.
The stress applying region is selectively formed below the source/drain region.
The stress applying region is recrystallized in the state where a stress is applied to the amorphized region from the portion other than the amorphized region, thereby generating the stress.
The stress applying region preferably generates the stress by implanting the group IV semiconductor atoms.
The group IV semiconductor atoms are applied to the stress applying region from the side face of the isolation trench.
The group IV semiconductor atoms are applied to the stress applying region through the single crystal semiconductor thin film and the first insulating film from the upper portion of the single crystal semiconductor thin film in the source/drain region.
The stress is applied by the thin film formed on the single crystal semiconductor thin film.
The stress is applied by the material buried in the trench of the isolation region.
The stress applied by the stress applying film is the tensile stress in the region in which the NMOS transistor is intended to be formed, and is the compressive stress in the region in which the PMOS transistor is intended to be formed.
The stress applying film serves also as the etching stopper in the process for forming the isolation region.
In the state in which the insulator region is formed, the tensile stress is applied to the single crystal semiconductor thin film in the NMOS formation region surrounded by the isolation region, and the compressive stress is applied to the single crystal semiconductor thin film in the PMOS formation region surrounded by the isolation region.
The surface orientation of the semiconductor substrate is (100), the surface orientation of the single crystal semiconductor thin film is (100) in the region in which the NMOS transistor is intended to be formed, and the crystal orientation of the single crystal semiconductor thin film parallel with the current direction of the NMOS channel is <100>. In addition, the surface orientation of the single crystal semiconductor thin film in the region in which the PMOS transistor is intended to be formed is (100), and the crystal orientation of the single crystal semiconductor thin film parallel with the current direction of the PMOS channel is <110>.
The surface orientation of the semiconductor substrate is (110), the surface orientation of the single crystal semiconductor thin film in the region in which the NMOS transistor is intended to be formed is (100) and the crystal orientation of the single crystal semiconductor thin film parallel with the current direction of the NMOS channel is <100>. In addition, the surface orientation of the single crystal semiconductor thin film in the region in which the PMOS transistor is intended to be formed is (110), and the crystal orientation of the single crystal semiconductor thin film parallel with the current direction of the PMOS channel is <110>.
Furthermore, the surface orientation of the semiconductor substrate may be (100), the surface orientation of the single crystal semiconductor thin film in the region in which the NMOS transistor is intended to be formed may be (100), and the crystal orientation of the single crystal semiconductor thin film parallel with the current direction of the NMOS channel may be <100>. In addition, the surface orientation of the single crystal semiconductor thin film in the region in which the PMOS transistor is intended to be formed may be (110), and the crystal orientation of the single crystal semiconductor thin film parallel with the current direction of the PMOS channel may be <110>.
The single crystal semiconductor thin film in the region in which the NMOS transistor is intended to be formed is amorphized, and is then recrystallized in the same direction as the crystal orientation of the semiconductor substrate. As a result, the surface orientation of the single crystal semiconductor thin film in the region in which the NMOS transistor is intended to be formed is (100), and the crystal orientation of the single crystal semiconductor thin film parallel with the current direction of the NMOS channel is <100>.
The single crystal semiconductor thin film in the region in which the PMOS transistor is intended to be formed is amorphized, and is then recrystallized in the same direction as the crystal orientation of the semiconductor substrate. As a result, the surface orientation of the single crystal semiconductor thin film in the region in which the PMOS transistor is intended to be formed is (100), and the crystal orientation of the single crystal semiconductor thin film parallel with the current direction of the PMOS channel is <110>.
The single crystal semiconductor thin film in the region in which the PMOS transistor is intended to be formed is amorphized, and is then recrystallized in the same direction as the crystal orientation of the semiconductor substrate. As a result, the surface orientation of the single crystal semiconductor thin film in the region in which the PMOS transistor is intended to be formed is (110), and the crystal orientation of the single crystal semiconductor thin film parallel with the current direction of the PMOS channel is <110>.
Number | Date | Country | Kind |
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2006-164620 | Jun 2006 | JP | national |