JPH10209442A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent fluctuation in threshold voltage due to boron penetration, by introducing a crystal defect into a gate oxide film formation region of a semiconductor substrate, doping with nitrogen, allowing the crystal defect to fix the nitrogen, applying an oxidation process with the semiconductor substrate, for forming a gate oxide film. SOLUTION: A element separation/sacrifice film 4 is formed on a silicon substrate 1, then ion-implantation for well and that for threshold value control are performed, after that, Ge ion-implantation for introducing crystal defect is performed. A nitrogen is ion-implanted into the silicon substrate 1. The silicon substrate is annealed and nitrogen atoms are fixed with crystal defect. After the sacrifice oxide film 4 is removed, a gate oxidation process is performed with the silicon substrate. Since, with a crystal defect introduced in advance, the crystal defect is complemented with nitrogen atoms, no characteristics of a semiconductor device is degraded, and the fluctuation in threshold voltage due to boron penetration is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a fine MOS type semiconductor device.

[0002]

2. Description of the Related Art In a p @ + type gate used in a surface channel type PMOSFET (field effect transistor) which is one of components of a fine CMOS type semiconductor device, boron which is a dopant of a gate electrode is subjected to heat during a thermal process. So-called boron penetration, which penetrates and diffuses through the gate oxide film to reach the channel region and fluctuates the threshold voltage, has become a problem.

[0005] To solve this problem, (1) a method of suppressing the diffusion of boron in the gate electrode by ion-implanting nitrogen into a polysilicon film serving as a gate electrode; (3) nitriding or oxynitriding the gate oxide film in an atmosphere such as ammonia gas or N2 O gas to form a gate oxide film. A method for suppressing the diffusion of boron has been proposed.

However, the above method is effective in preventing boron penetration, but the method (1) has a disadvantage that the gate electrode is depleted, and the methods (2) and (3) have a mutual conductance. (Hereinafter, abbreviated as gm), which is a disadvantage that the characteristics of the transistor are deteriorated.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and has been made in view of the above circumstances. Therefore, it is possible to manufacture a semiconductor device capable of preventing a change in threshold voltage due to boron penetration without deteriorating the characteristics of the semiconductor device. The aim is to provide a method.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device comprising a gate electrode containing an impurity element provided on a semiconductor substrate via a gate oxide film. Introducing a crystal defect into the
A semiconductor device comprising: doping nitrogen into a semiconductor substrate; fixing nitrogen to the crystal defects; and forming a gate oxide film by subjecting the semiconductor substrate to an oxidation process. A manufacturing method is provided.

The present invention also relates to a method of manufacturing a semiconductor device comprising a gate electrode containing an impurity element provided on a semiconductor substrate via a gate oxide film. Introducing a crystal defect by ion implantation of a Group IV element, doping nitrogen into the semiconductor substrate by ion implantation, and fixing nitrogen to the crystal defect by subjecting the semiconductor substrate to a heat treatment. And a step of forming a gate oxide film by subjecting the semiconductor substrate to an oxidation treatment.

According to the present invention, since a crystal defect is introduced into the gate oxide film forming region of the semiconductor substrate, boron is doped to suppress diffusion of boron, which is an impurity element contained in the gate electrode, into the channel region. Trapped nitrogen atoms by crystal defects. Therefore, it is possible to prevent a decrease in channel mobility due to diffusion of nitrogen into the channel region,
Deterioration of characteristics of the semiconductor device (particularly, decrease in gm) can be prevented.

The present invention also relates to a method of manufacturing a semiconductor device in which a gate electrode is provided on a semiconductor substrate via a gate oxide film, wherein a step of introducing a crystal defect into a gate oxide film forming region of the semiconductor substrate is provided. A step of doping the semiconductor substrate with nitrogen by heat treatment in a nitrogen-containing gas, a step of fixing nitrogen to the crystal defects, and a step of forming a gate oxide film by performing an oxidation treatment on the semiconductor substrate. The present invention provides a method for manufacturing a semiconductor device, characterized in that:

According to the present invention, nitrogen is doped not by ion implantation but by (oxy) nitridation. In the case of ion implantation, it is difficult to introduce nitrogen only on the surface side because the substrate has a peak and the nitrogen distribution has a spread (ΔR _P ). On the other hand, in the case of the (oxy) nitriding treatment, there is an advantage that a peak is present on the outermost surface and a shallow distribution is easily formed because of a thermal diffusion phenomenon.

[0011]

Embodiments of the present invention will be specifically described below with reference to the drawings. As shown in FIG. 1, characteristic degradation of a semiconductor device in which a gate electrode 3 containing an impurity element, for example, boron (B) is provided via a gate oxide film 2 on a silicon substrate 1 which is a semiconductor substrate, especially gm
Nitrogen doped to suppress the diffusion of boron into the channel region of the silicon substrate 1, that is, as shown in FIG.
During heat treatment such as nitriding treatment, gate oxidation treatment, and impurity activation annealing, diffusion into the channel region to reduce carrier mobility in the channel region can be mentioned. Therefore, it is necessary to prevent nitrogen from diffusing into the channel region in some way.

The present inventors have found that crystal defects having a certain density or higher introduced by ion implantation or the like are not removed even after a subsequent heat treatment and become secondary defects, and these secondary defects are referred to as “gettering sites”. Focusing on trapping various atoms, crystal defects are introduced in advance, and by trapping nitrogen atoms in these crystal defects, it is possible to prevent diffusion of nitrogen into the channel region of the semiconductor substrate. The present invention led to the heading.

That is, during ion implantation, the larger the implantation dose, the larger the mass of implanted ions, and the lower the substrate temperature at the time of implantation, the greater the amount of crystal defects generated in the semiconductor substrate. Furthermore, the initial crystal defects disappear or form dislocation loops (secondary defects) of various sizes depending on the annealing (heat treatment) conditions (temperature, time, atmosphere). When the dislocation loop is formed, dangling bonds are present in the material constituting the semiconductor substrate, for example, a lattice of silicon, and various atoms are trapped (gettered) therein.

Based on the above fact, the dislocation loop depth,
By appropriately controlling the density and size so that nitrogen atoms are present near crystal defects during annealing, a desired position and amount of nitrogen atoms can be captured and fixed by a dislocation loop. Therefore, even after a heat treatment step such as a gate oxidation treatment, nitrogen can be kept in the gate oxide film, and diffusion of nitrogen into a channel region of the semiconductor substrate can be prevented. As a result, while preventing boron from passing through the gate oxide film and reaching the channel region to change the threshold value, it is possible to prevent nitrogen from diffusing into the channel region and reducing gm, and the state shown in FIG. Can be realized.

In the present invention, as an element to be ion-implanted to introduce a crystal defect, considering that a deep level is not formed in a silicon substrate, a group IV element of the periodic table, for example, C, Si, Ge is used. , Sn are preferably used.

Further, it is preferable to form a sacrificial oxide film on the semiconductor substrate in advance to introduce crystal defects. By forming the sacrificial oxide film, the defect distribution can be controlled to be shallow.

In the present invention, doping with nitrogen may be performed before the ion implantation step for introducing crystal defects.

Next, an embodiment of the present invention will be described. Example 1 Element separation, formation of a sacrificial oxide film, ion implantation for wells, and ion implantation for threshold control are performed on a silicon substrate, which is a semiconductor substrate, and then a group IV element of the periodic table for introducing crystal defects. Ge ions are implanted. At this time, as shown in FIG. 3, the Ge concentration is distributed so that the interface between the silicon substrate 1 and the sacrificial oxide film 4 becomes a peak, and the crystal defects are located near the interface between the silicon substrate 1 and the sacrificial oxide film 4. It is introduced into the substrate, that is, into the gate oxide film forming region.

Ge ion implantation for introducing crystal defects is as follows.
Implantation energy of about 10 keV, implantation dose of 2 × 10
14ions / cm2 or more is required. By using the range table based on the LSS theory in Table 1 below, the position of the crystal defect under this condition can be calculated. That is, L in Table 1
The depth, density, and size of dislocation loops, which are crystal defects, are appropriately controlled using a range table based on SS theory. In this case, the projection range Rp of Ge in the oxide film is 7.8 nm, the standard deviation ΔRp in Si is 3.6 nm, and crystal defects are introduced into a region of about 4 nm from the silicon substrate surface. If the thickness of the sacrificial oxide film is different, the first
Conditions such as injection energy are appropriately selected and set from the range table of the table.

[0020]

[Table 1]

Then, nitrogen is ion-implanted into the silicon substrate to introduce nitrogen. Injection energy is 2 keV
The implantation dose must be at least 5 × 10 13 ions / cm 2. In this case, the projected range Rp of nitrogen is 4 nm, and the standard deviation ΔRp is 3 nm. As shown in FIG. To In addition,
This nitrogen ion implantation may be performed before the ion implantation step for introducing crystal defects.

Next, the silicon substrate is annealed to fix nitrogen atoms with crystal defects. An appropriate annealing temperature is about 500 to 1100 ° C. and an appropriate annealing time is about 10 seconds to 10 hours. The nitrogen concentration distribution at this time is as shown in FIG. That is, it can be seen that the nitrogen atoms are fixed by crystal defects. This prevents nitrogen from diffusing into the channel region of the silicon substrate.

Next, after removing the sacrificial oxide film, the silicon substrate is subjected to a gate oxidation treatment in an atmosphere of dry nitrogen, hydrochloric acid-containing dry nitrogen, water vapor-containing oxygen, or the like. In this case, care must be taken because nitrogen may be present in the silicon substrate and the oxidation rate may be reduced. When the thickness of the gate oxide film is about 5 nm, the nitrogen concentration distribution is as shown in FIG. 6, and nitrogen is present in the gate oxide film 2.

After that, p + type gate electrode formation, LDD
(Lightly Doped Drain) ion implantation, source / drain ion implantation, interlayer insulating film formation, impurity activation annealing, wiring process, etc., to complete the semiconductor device.

In the semiconductor device thus obtained, the threshold voltage does not fluctuate due to boron penetration, and gm does not decrease.

(Example 2) In place of Ge ion implantation for introducing crystal defects, an example in which Si ion implantation of Group IV element of the periodic table, C ion implantation, or Sn ion implantation is performed. The same effect as that of No. 1 can be obtained. In addition, when the thickness of the sacrificial oxide film is 10 nm, the respective implantation energy and implantation dose are as follows including Ge. Also, if the thickness of the sacrificial oxide film changes, the implantation energy also changes accordingly. Implantation energy Implantation dose C 3 keV 5 × 10 15 ions / cm 2 Si 6 keV 6 × 10 14 ions / cm 2 Ge 10 keV 2 × 10 13 ions / cm 2 Sn 15 keV 1 × 10 13 ions / cm 2

Embodiment 3 In order to introduce nitrogen into a silicon substrate, instead of ion-implanting nitrogen, as shown in FIG. 7, after removing a sacrificial oxide film, N
(Oxidation) nitriding may be performed in a nitrogen-containing gas atmosphere such as H3 gas, N2 O gas, and NO gas. In this case, the gas flow rate is about 10 l / min or less, and the temperature is 950.
１1100 ° C., and a time of 10 seconds or more is required. Also in this case, by performing a gate oxidation process thereafter,
The element structure and the nitrogen concentration distribution shown in FIG. 6 are obtained.

[0028]

As described above, according to the method of manufacturing a semiconductor device of the present invention, a crystal defect is introduced in advance, and nitrogen atoms are trapped in the crystal defect. It is possible to prevent a change in threshold voltage due to boron penetration.

[Brief description of the drawings]

FIG. 1 is a diagram showing an element structure showing a state where boron is diffused to a silicon substrate and a boron concentration distribution.

FIG. 2 is a diagram showing an element structure and a boron concentration distribution showing a state where boron is not diffused to a silicon substrate.

FIG. 3 is a view for explaining a Ge ion implantation step in the method of manufacturing a semiconductor device according to the present invention.

FIG. 4 is a diagram for explaining a nitrogen ion implantation step in the method for manufacturing a semiconductor device according to the present invention.

FIG. 5 is a diagram for explaining an annealing step for fixing nitrogen in the method of manufacturing a semiconductor device according to the present invention.

FIG. 6 is a diagram illustrating a gate oxidation treatment step in the method for manufacturing a semiconductor device according to the present invention.

FIG. 7 is a view for explaining a nitriding treatment step for introducing nitrogen in the method of manufacturing a semiconductor device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Gate oxide film, 3 ... Boron-doped gate electrode, 4 ... Sacrificial oxide film.

Claims (4)

[Claims] 1. A method of manufacturing a semiconductor device, comprising: providing a gate electrode containing an impurity element on a semiconductor substrate via a gate oxide film, the method comprising: introducing a crystal defect into a gate oxide film forming region of the semiconductor substrate; A step of doping nitrogen into a semiconductor substrate; a step of fixing nitrogen to the crystal defects; and a step of forming a gate oxide film by oxidizing the semiconductor substrate. Device manufacturing method. 2. A method of manufacturing a semiconductor device, comprising providing a gate electrode containing an impurity element on a semiconductor substrate with a gate oxide film interposed therebetween, wherein a gate oxide film forming region of the semiconductor substrate includes a group IV element of a periodic table. Introducing a crystal defect by ion implantation of nitrogen, a step of doping nitrogen into the semiconductor substrate by ion implantation, and a step of fixing nitrogen to the crystal defect by subjecting the semiconductor substrate to a heat treatment. Forming a gate oxide film by subjecting the substrate to an oxidation process. 3. A method for manufacturing a semiconductor device, comprising: providing a gate electrode containing an impurity element on a semiconductor substrate via a gate oxide film, the method comprising: introducing a crystal defect into a gate oxide film forming region of the semiconductor substrate; A step of doping the semiconductor substrate with nitrogen by a heat treatment in a nitrogen-containing gas, a step of fixing nitrogen to the crystal defects, and a step of forming a gate oxide film by performing an oxidation treatment on the semiconductor substrate. A method for manufacturing a semiconductor device, comprising: 4. The method according to claim 2, wherein the crystal defects are introduced into the semiconductor substrate by ion-implanting a Group IV element of the periodic table after forming an oxide film on the semiconductor substrate. A method for manufacturing a semiconductor device according to claim 1.