JP2014033128A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that negative bias thermal instability (NBTI) occurs in which a threshold value of a transistor is fluctuated with heat and negative voltage especially in a PMOS transistor, in an MOS transistor, and in a lamination structure between a silicon oxide film and a silicon oxynitride film, the NBTI is remarkable when the film thickness is 5 nm or more.SOLUTION: A silicon oxide film is used for an MOS transistor of a thick film gate insulation film 3, and a lamination structure between a silicon oxide film 7 and a silicon oxynitride film 8 is used for an MOS transistor of a thin film gate insulation film 9, so that NBTI deterioration in the MOS transistor of the thick film gate insulation film can be avoided when the performance of the MOS transistor of the thin film gate insulation film is improved.

Description

  The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly to a MOS semiconductor device including two types of transistors having different gate insulating films and a manufacturing method thereof.

  The MOS semiconductor device includes a driving system and a power system MOS transistor. The driving system mainly includes a thin gate oxide film, and the power system includes a thick gate oxide film. Is used.

  Patent Document 1 discloses a method for forming two types of gate oxide films having different thicknesses. In Patent Document 1, after forming a thin first gate oxide film on a silicon substrate, a first polycrystalline silicon film is formed, and a first gate oxide film in a region where a thick gate oxide film is formed Is removed to expose the surface of the silicon substrate. Next, a thick second gate oxide film is formed on the surface of the silicon substrate exposed by thermal oxidation. At the same time, a silicon oxide film is also formed on the surface of the first polycrystalline silicon film. Further, after depositing the second polycrystalline silicon film, the second polycrystalline silicon film overlying the first polycrystalline silicon film is removed, and the surface of the first polycrystalline silicon film is oxidized with hydrofluoric acid. The silicon film is removed, a third polycrystalline silicon film is further deposited thereon, and the first to third polycrystalline silicon films are etched to form a gate electrode.

  Recently, in order to improve the performance of a transistor, a dielectric constant is increased by using a gate insulating film as a stacked structure of a silicon oxide film and a silicon oxynitride film.

Japanese Patent Laid-Open No. 06-021369

  In the case of MOS transistors, the problem of negative bias temperature instability (NBTI), in which the threshold of the transistor varies at high temperatures and negative voltages, especially in PMOS transistors, is notable as the gate insulating film becomes thicker. It has become to. It has been clarified by the present inventors that this phenomenon becomes significant when the film thickness is 5 nm or more in the laminated structure of the silicon oxide film and the silicon oxynitride film.

According to one embodiment of the present invention,
A semiconductor device comprising a first MOS transistor having a first gate insulating film and a second MOS transistor having a second gate insulating film,
There is provided a semiconductor device, wherein the first gate insulating film includes a silicon oxide film, and the second gate insulating film includes a silicon oxide film and a silicon oxynitride film.

Also, according to another embodiment of the present invention,
Forming a first silicon oxide film on the semiconductor substrate;
Forming a first polycrystalline silicon on the first silicon oxide film;
Removing the first silicon oxide film and the first polycrystalline silicon to expose a part of the semiconductor substrate;
Forming a second silicon oxide film on the exposed semiconductor substrate, and forming a second silicon oxide film on the remaining first polycrystalline silicon surface;
And a step of forming a silicon oxynitride film on the surface of the second silicon oxide film.

  According to an embodiment of the present invention, a gate oxide film is used for a MOS transistor of a thick gate insulating film, and a stacked structure of an oxide film and an oxynitride film is used for a MOS transistor of a thin film gate insulating film. In addition to improving the performance of the film MOS transistor, it is possible to prevent the NBTI deterioration of the thick gate insulating film MOS transistor.

FIG. 5 is a process cross-sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the invention. The top view of the FIG. 1 process. FIG. 5 is a process cross-sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the invention. FIG. 5 is a process cross-sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the invention. 4 is a plan view of the process. FIG. 5 is a process cross-sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the invention. FIG. 5 is a process cross-sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the invention. FIG. 5 is a process cross-sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the invention. FIG. 5 is a process cross-sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the invention. 9 is a plan view of the process. FIG. 5 is a process cross-sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the invention. FIG. 11 is a plan view of the step. FIG. 5 is a process cross-sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the invention. FIG. 13 is a plan view of the step.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments.

(Example 1)
1 to 14 are process diagrams illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention, and are schematic cross-sectional views (FIGS. 1, 3, 4, 6-9, 11, 13) and plan views. (FIGS. 2, 5, 10, 12, and 14) are shown.

  First, as shown in FIG. 1 and FIG. 2, element isolation is performed on a semiconductor substrate (silicon substrate) 1 on which N-wells and P-wells are formed by channel implantation at the boundary between N-wells and P-wells by a known method. Region (STI) 2 is formed. A PMOS is formed on the N-well, and an NMOS is formed on the P-well. The well structure is not limited to this example. When a P-type silicon substrate is used, a structure without P-well or a triple well structure in which a P-well is formed in an N-well can be used. .

  Next, as shown in FIG. 3, a thick first gate insulating film (first gate oxide film) 3 is formed on the entire surface of the semiconductor substrate 1. In this example, the first gate oxide film 3 is formed by a deposition method, but may be formed by substrate oxidation. In that case, it is not formed on the STI 2, but about half of its film thickness is formed in the semiconductor substrate 1 receding from the upper surface of the STI 2. The first gate oxide film 3 may be a film that is thicker than a thin second gate insulating film, which will be described later.

  A first polycrystalline silicon film (first polysilicon film) 4 is formed on the first gate oxide film 3. For the first polysilicon film 4, undoped polysilicon or doped polysilicon doped with N-type impurities such as phosphorus (P) can be used.

  As shown in FIGS. 4 and 5, a photoresist mask 6 is formed on the N-well to form a first (PMOS) gate stack 5, and the first polysilicon film 4 on the P-well is dry-etched. Then, the first gate oxide film 3 is removed by etching. Thereafter, the resist mask 6 is removed.

  Next, as shown in FIG. 6, a second gate oxide film 7 is formed. The second gate oxide film 7 may be formed by a thermal oxidation method or a deposition method.

  Next, as shown in FIG. 7, the surface of the second gate oxide film 7 is nitrided to form an oxynitride film 8. A stack of the second gate oxide film 7 and the oxynitride film 8 is referred to as a second gate insulating film 9. The second gate insulating film 9 is thinner than the first gate oxide film 3, and is, for example, less than 10 nm, more preferably less than 5 nm. The surface of the oxynitride film 8 may be substantially a nitride film (silicon nitride film). Nitriding can be performed by exposing the substrate on which the second gate oxide film 7 has been formed to a nitrogen plasma atmosphere. When the second gate oxide film 7 is formed by a deposition method, the oxynitride film 8 may be formed continuously. For example, in the case of forming by the CVD method, the second gate oxide film 7 is deposited in the initial stage using a silicon source gas (for example, tetraethoxysilane (TEOS) or the like) and an oxidizing gas (for example, oxygen or ozone). The oxynitride film 8 can be formed by introducing a nitriding gas (for example, ammonia gas).

  Next, as shown in FIG. 8, a second polycrystalline polysilicon film (second polysilicon film) 10 is formed on the entire surface. The second polysilicon film 10 can be made of undoped polysilicon or doped polysilicon doped with a P-type impurity such as boron (B).

  Next, as shown in FIGS. 9 and 10, the second polysilicon film 10 is planarized by chemical mechanical polishing (CMP). At this time, the second gate insulating film 9 on the first polysilicon film 4 is used as an etching stopper, the upper surface of the first polysilicon film 4 is exposed, and the first polysilicon film 4 and the second polysilicon film 10 Align. The second gate insulating film 9 (second gate oxide film 7 and oxynitride film 8) is exposed at the boundary with the first gate stack 5.

  Next, as shown in FIGS. 11 and 12, a metal layer 11 such as tungsten (W) and a silicon nitride film as a cap layer 12 are formed on the entire surface, and a mask photoresist 13 for forming a gate pattern is further formed. To do.

  Finally, as shown in FIGS. 13 and 14, the cap layer 12 is etched using the mask photoresist 13 as a mask, and then the underlying film is etched away so that the surface of the STI 2 and the surface of the semiconductor substrate 1 are exposed. A first gate electrode (PMOS gate) 14 formed by stacking the first polysilicon film 4, the metal layer 11, and the cap layer 12 in the region, and a stack of the second polysilicon film 10, the metal layer 11, and the cap layer 12 in the NMOS region. A second gate electrode (NMOS gate) 15 is formed. On the exposed surface of the semiconductor substrate 1, P-type impurities are implanted into the PMOS formation region to form the source / drains 16A and 16B of the first MOS transistor, and N-type impurities are implanted into the NMOS region to form the second MOS transistor. Source / drains 17A and 17B are formed.

  Thereafter, contacts and wirings connected to the first and second MOS transistors are formed by a known method, and the semiconductor device is completed.

  In the above example, when the PMOS transistor and the NMOS transistor are formed, the PMOS transistor having excellent NBTI characteristics by applying the first gate insulating film not including the thick oxynitride film to the gate insulating film of the PMOS transistor. On the other hand, in the NMOS to which the thin second gate insulating film including the oxynitride film is applied, the transistor characteristics are improved by increasing the dielectric constant.

  In addition, this invention is not limited to the said embodiment example illustrated. For example, although the case where the PMOS and NMOS are formed as the structure of the MOS transistor has been described, the present invention can be applied to the case where PMOSs or NMOSs having different threshold characteristics are formed. In addition, as the gate electrode structure, a so-called polymetal structure in which a metal layer is formed on a polysilicon film has been described. A poly gate structure using only a polysilicon film may be used. Further, although an example in which a gate electrode is formed for each semiconductor substrate 1 (active region) surrounded by STI as a gate electrode has been described, a gate electrode having a wiring structure straddling a plurality of active regions may be used. Furthermore, when the PMOS and the NMOS are adjacent to each other as illustrated, the CMOS may be formed by connecting the respective gate electrodes.

  When the PMOS and NMOS are formed as in the first embodiment, the first polysilicon film 4 and the second polysilicon film 10 constituting the respective gate electrodes are provided on the semiconductor substrate 1 serving as the channel of each transistor. By introducing an impurity of the same conductivity type (source / drain and opposite conductivity type), a highly reliable and high speed PMOS and NMOS can be produced.

Embodiment 2
In the first embodiment, the thick first gate insulating film 3 is formed first, and the thin second gate insulating film 9 is formed later. Conversely, the thin second gate insulating film 9 is formed. After forming the second polysilicon film 10, the second gate stack is formed on the NMOS region side as shown in FIG. 4, and then the thick first gate oxide film 3, the first polysilicon film 10 are formed. The silicon film 4 may be formed, and the heights of the first polysilicon film 4 and the second polysilicon film 10 may be made uniform as shown in FIG.

1 Semiconductor substrate (silicon substrate)
2 STI
3 First gate insulating film (first gate insulating film)
4 First polycrystalline silicon film (first polysilicon film)
5 First gate stack 6 Photoresist 7 Second gate oxide film 8 Oxynitride film 9 Second gate insulating film 10 Second polycrystalline silicon film (second polysilicon film)
11 Metal layer 12 Cap layer 13 Photoresist 14 First gate electrode (PMOS gate)
15 Second gate electrode (NMOS gate)
16A, 16B Source / drain (PMOS)
17A, 17B Source / drain (NMOS)

Claims (12)

A semiconductor device comprising a first MOS transistor having a first gate insulating film and a second MOS transistor having a second gate insulating film,
The semiconductor device, wherein the first gate insulating film includes a silicon oxide film, and the second gate insulating film includes a silicon oxide film and a silicon oxynitride film.   2. The semiconductor device according to claim 1, wherein a film thickness of the first gate insulating film is larger than a film thickness of the second gate insulating film.   3. The semiconductor device according to claim 2, wherein a gate electrode is formed in contact with the silicon oxide film of the first MOS transistor.   The semiconductor device according to claim 2, wherein the first gate insulating film does not include a silicon oxynitride film.   The semiconductor device according to claim 2, wherein the first gate insulating film has a thickness of 5 nm or more.   The semiconductor device according to claim 5, wherein the first MOS transistor is a PMOS transistor, and the second transistor is an NMOS transistor. Forming a first silicon oxide film on the semiconductor substrate;
Forming a first polycrystalline silicon on the first silicon oxide film;
Removing the first silicon oxide film and the first polycrystalline silicon to expose a part of the semiconductor substrate;
Forming a second silicon oxide film on the exposed semiconductor substrate, and forming a second silicon oxide film on the remaining first polycrystalline silicon surface;
And a step of forming a silicon oxynitride film on the surface of the second silicon oxide film. Forming a second polycrystalline silicon on the silicon oxynitride film;
Polishing the second polycrystalline silicon and the silicon oxynitride film on the surface of the first polycrystalline silicon until the first polycrystalline silicon is exposed;
The method of manufacturing a semiconductor device according to claim 7, comprising:   The method of manufacturing a semiconductor device according to claim 8, wherein the first polycrystalline silicon includes an N-type impurity, and the second polycrystalline silicon includes a P-type impurity.   10. The method according to claim 8, further comprising a step of forming a gate electrode by patterning the remaining first and second polycrystalline silicon films after the step of polishing until the first polycrystalline silicon is exposed. A method for manufacturing a semiconductor device.   The method for manufacturing a semiconductor device according to claim 7, wherein the first and second silicon oxide films are formed by thermal oxidation.   12. The method of manufacturing a semiconductor device according to claim 7, wherein the silicon oxynitride film is formed by performing nitrogen plasma treatment on a surface of the second silicon oxide film.

Images