JP2005150285A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device which has a gate insulation film consisting of a silicon oxynitride film having a thickness of 2 nm or less and can achieve a good interfacial characteristic between the gate insulation film and an Si substrate, and has a barrier property that makes it difficult for boron to be diffused from a gate electrode. <P>SOLUTION: A silicon oxide film to be grown to the base is formed. Then, nitrogen is introduced in the form of nitrogen radicals or nitrogen ions generated by plasmas into the silicon oxide film to form the silicon oxynitride film. Thereafter, wet etching is carried out to the peak position of the nitrogen concentration of the silicon oxynitiride film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a gate insulating film of a MOS transistor.

In recent years, as a gate insulating film of a MOS transistor, a silicon oxynitride film containing nitrogen having a good barrier property for boron diffusion from a gate electrode is being used instead of a silicon oxide film (SiO ₂ ).

  As a method for forming a gate insulating film made of a silicon oxynitride film, after forming a silicon oxide film as a base, nitrogen is generally introduced into the silicon oxide film by nitrogen radicals or nitrogen ions generated by plasma. (For example, refer to Patent Document 1).

  FIG. 1 shows a conventional method of manufacturing a semiconductor device (MOS transistor).

  As shown in FIG. 1, in the conventional method for manufacturing a semiconductor device, a silicon oxide film 102 serving as a base is formed on a Si substrate 101. Next, nitrogen is introduced into the silicon oxide film 102 by nitrogen radicals or nitrogen ions generated by plasma to form a gate insulating film 103 made of a silicon oxynitride film. Next, although illustration of subsequent processes is omitted, a polysilicon film is deposited on the gate insulating film 103 made of a silicon oxynitride film, and the gate insulating film 103 made of the polysilicon film and the silicon oxynitride film is patterned. Then, the gate electrode 104 is formed, and source / drain regions 105 are formed by impurity ion implantation using the gate electrode 104 as a mask and heat treatment (for example, RTA) for activation thereof.

  FIG. 2 is a nitrogen concentration profile of a gate insulating film 2 nm made of a silicon oxynitride film formed by a conventional method for manufacturing a semiconductor device (MOS transistor).

  FIG. 3 is a nitrogen concentration profile of a gate insulating film 1.8 nm made of a silicon oxynitride film formed by a conventional method for manufacturing a semiconductor device (MOS transistor).

As shown in FIG. 2 and FIG. 3, in the 2 nm and 1.8 nm nitrogen profiles made of silicon oxynitride films, the maximum nitrogen concentration is 8 atm% (atomic percent) or more, and the maximum nitrogen concentration peak is gate insulating. The position is about 0.5 nm from the upper surface of the film (nitrogen introduction side). However, the nitrogen concentration at the interface between the gate insulating film and the Si substrate is 3 atm% or less for the gate insulating film 2 nm, but is higher than 3 atm% for the gate insulating film 1.8 nm. The reason why the nitrogen concentration at the interface between the gate insulating film and the Si substrate increases as the gate insulating film becomes thinner is that the base silicon oxide film becomes thinner, so that more nitrogen radicals or nitrogen ions reach the Si substrate. Because.
JP 2002-222941 A

  When a gate insulating film made of a silicon oxynitride film of 2 nm or less is formed by a conventional method for manufacturing a semiconductor device, the nitrogen concentration at the interface between the gate insulating film and the Si substrate becomes higher than 3 atm%. If excessive nitrogen is present at the interface between the gate insulating film and the Si substrate, the gate insulating film may deteriorate transistor mobility (decrease in driving power), change in transistor threshold voltage due to holes or electron traps after stress application, etc. And interface characteristics of the Si substrate deteriorate. Therefore, the nitrogen concentration at the interface between the gate insulating film and the Si substrate is desirably 3 atm% or less.

  When the amount of nitrogen reaching the interface between the gate insulating film and the Si substrate is reduced by reducing the amount of nitrogen radicals or nitrogen ions generated by the plasma in the conventional semiconductor device manufacturing method, the interface between the gate insulating film and the Si substrate is reduced. However, the maximum nitrogen concentration is lower than 8 atm%. In order to obtain a good barrier property of boron diffusion from the gate electrode, the maximum nitrogen concentration is desirably 8 atm% or more.

  That is, when a gate insulating film having a thickness of 2 nm or less is formed by a conventional method of manufacturing a semiconductor device, it is impossible to achieve both the interface characteristics between the gate insulating film and the Si substrate and the barrier property of boron diffusion from the gate electrode.

  Therefore, an object of the present invention is a semiconductor in which the maximum nitrogen concentration is 8 atm% or more and the nitrogen concentration at the interface between the gate insulating film and the Si substrate is 3 atm% or less in a gate insulating film made of a silicon oxynitride film of 2 nm or less. A method of manufacturing the device is proposed, which is to achieve both the interface characteristics between the gate insulating film and the Si substrate and the barrier property of boron diffusion from the gate electrode.

  In order to solve the above-described problems, a method for manufacturing a semiconductor device of the present invention forms a silicon oxide film as a base. Next, nitrogen is introduced into the silicon oxide film with nitrogen radicals or nitrogen ions generated by plasma to form a silicon oxynitride film. Next, the silicon oxynitride film is removed to the maximum nitrogen concentration peak position.

  Specifically, if the gate insulating film has a thickness larger than 2 nm, nitrogen can be introduced into a silicon oxide film having a thickness of 2 nm or more, and a maximum nitrogen concentration of 8 atm% or more and an interface nitrogen concentration of 3 atm% or less can be achieved. On the other hand, when nitrogen is introduced into a silicon oxide film having a thickness of 2 nm or less, the maximum nitrogen concentration becomes 8 atm% or more, but the thickness is too thin to reach the silicon substrate and becomes 3 atm% or more. Therefore, in the present invention, nitrogen is introduced into a 2 nm silicon oxide film, and an oxynitride film having a maximum nitrogen concentration of 8 atm% or more and an interface nitrogen concentration of 3 atm% or less is once formed, and then wet-etched to the position of the maximum nitrogen concentration. Thus, an oxynitride film having a thickness of 2 nm or less and a maximum nitrogen concentration of 3 atm% or less is formed.

  According to the semiconductor device manufacturing method of the present invention described above, in the gate insulating film made of a silicon oxynitride film of 2 nm or less, the maximum nitrogen concentration is 8 atm% or more, and the nitrogen concentration at the interface between the gate insulating film and the Si substrate is 3 atm. % Or less of the semiconductor device can be realized.

  As described above, according to the method for manufacturing a semiconductor device of the present invention, the maximum nitrogen concentration in the gate insulating film made of a silicon oxynitride film of 2 nm or less is 8 atm% or more and the nitrogen at the interface between the gate insulating film and the Si substrate is used. The concentration was adjusted to 3 atm% or less. Therefore, it is possible to achieve both the interface characteristics between the gate insulating film and the Si substrate and the barrier property of boron diffusion from the gate electrode. Further, by reducing the thickness of the gate insulating film to 2 nm or less, the speed of the MOS transistor is increased.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 4 shows a method for manufacturing a semiconductor device (MOS transistor) according to the first embodiment of the present invention.

  As shown in FIG. 4, in the method for manufacturing a semiconductor device according to the first embodiment of the present invention, a silicon oxide film 202 having a thickness of 2.0 to 2.2 nm is formed on a Si substrate 201 by thermal oxidation. The silicon oxide film 202 may be formed by generating oxygen radicals or oxygen ions with plasma.

Next, nitrogen radicals or nitrogen ions are generated by plasma under conditions of microwave 1500 W, Ar / N ₂ gas, pressure 130 Pa, and Si substrate 201 temperature of 400 ° C., and nitrogen is introduced for 20 seconds to form silicon oxynitride. A film 203 is formed. As a result, the nitrogen profile of the silicon oxynitride film 203 is such that the maximum nitrogen concentration is 8 atm% and the maximum nitrogen concentration peak is about 0.5 nm from the upper surface of the silicon oxynitride film (nitrogen introduction side). The nitrogen concentration at the interface of the substrate 201 is 1.5 atm%.

  Next, wet etching is performed from the upper surface of the silicon oxynitride film (the nitrogen introduction side) where the maximum nitrogen concentration peak of the silicon oxynitride film 203 is about 0.5 nm to form a gate insulating film 204 made of a silicon oxynitride film. . The wet etching chemical solution uses a low concentration hydrofluoric acid of 0.2 wt%.

  In the following, a control method for accurately stopping etching at 0.5 nm from the upper surface of the silicon oxynitride film will be described.

  FIG. 5 is a graph in which the horizontal axis represents the wet etching time and the vertical axis represents the wet etching amount. Until the wet etching time is around 120 seconds, the amount of wet etching will change little, but when the time reaches 120 seconds, which is the predetermined time, the etching rate will change before and after the peak position of the nitrogen concentration, and wet etching will occur as the elapsed time changes. The amount gets bigger. Here, after starting wet etching, the nitrogen concentration increases as the etching rate changes, the nitrogen concentration reaches its maximum at the time when the etching rate changes, and the nitrogen concentration decreases after the etching rate changes. It turned out to go. At this time, as a condition for maximizing the nitrogen concentration, the etching amount may be removed by 0.5 nm from the upper surface of the silicon oxynitride film. Therefore, the set time for wet etching may be set to a time when the wet etching time and the wet etching rate change.

  Next, although illustration of the subsequent steps is omitted, a polysilicon film is deposited on the gate insulating film 204 made of a silicon oxynitride film, and the gate insulating film 204 made of the polysilicon film and the silicon oxynitride film is patterned. Then, the gate electrode 205 is formed, and source / drain regions 206 are formed by impurity ion implantation using the gate electrode 205 as a mask and heat treatment (for example, RTA) for activation thereof.

  FIG. 6 is a nitrogen profile of a gate insulating film made of a silicon oxynitride film in the semiconductor device (MOS transistor) according to the first embodiment of the present invention.

  As shown in FIG. 6, the maximum nitrogen concentration is 8 atm%, the maximum nitrogen concentration peak is at the interface between the gate insulating film and the gate electrode, and the nitrogen concentration at the interface between the gate insulating film and the Si substrate is 1.5 atm%.

(Second Embodiment)
FIG. 7 shows a method for manufacturing a semiconductor device (MOS transistor) according to the second embodiment of the present invention.

  As shown in FIG. 7, in the method for manufacturing a semiconductor device according to the second embodiment of the present invention, a silicon oxide film 302 having a thickness of 2 to 2.2 nm is formed on a Si substrate 301 by thermal oxidation. The silicon oxide film 302 may be formed by generating oxygen radicals or oxygen ions with plasma.

Next, nitrogen radicals or nitrogen ions are generated by plasma under conditions of microwave 1500 W, Ar / N ₂ gas, pressure 130 Pa, Si substrate 301 temperature of 400 ° C. in the silicon oxide film 302, and nitrogen is introduced for 20 seconds to form a silicon oxynitride film 303 is formed.

  Next, the silicon oxynitride film 304 is formed by wet etching up to about 0.5 nm from the upper surface (nitrogen introduction side) of the silicon oxynitride film having the maximum nitrogen concentration peak of the silicon oxynitride film 303.

  Next, nitrogen radicals or nitrogen ions are generated in the silicon oxynitride film 304 by plasma, and nitrogen is introduced to form a gate insulating film 305 made of a silicon oxynitride film. The introduction of nitrogen here reduces the amount of nitrogen compared to the first introduction of nitrogen. Since the silicon oxynitride film 304 is 2 nm or less, when the same amount of nitrogen is introduced as the first nitrogen introduction, the nitrogen at the interface between the gate insulating film and the Si substrate becomes excessive and the nitrogen concentration becomes 3 atm% or more. Because. The condition for introducing nitrogen is that the pressure is raised from the first pressure condition to 250 Pa, or the nitrogen introduction time is 10 seconds.

  Although illustration of the subsequent steps is omitted, a polysilicon film is deposited on the gate insulating film 305 made of a silicon oxynitride film, the gate insulating film 305 made of the polysilicon film and the silicon oxynitride film is patterned, and the gate An electrode 306 is formed, and source / drain regions 307 are formed by impurity ion implantation using the gate electrode 306 as a mask and heat treatment (for example, RTA) for activation thereof.

  FIG. 8 is a nitrogen profile of a gate insulating film made of a silicon oxynitride film in the semiconductor device (MOS transistor) of the second embodiment of the present invention.

  As shown in FIG. 8, the maximum nitrogen concentration is 10 atm%, the maximum nitrogen concentration peak is at the position of the interface between the gate insulating film and the gate electrode, and the nitrogen concentration at the interface between the gate insulating film and the Si substrate is 2 atm%.

  According to the above, the maximum nitrogen concentration is increased by further introducing nitrogen after the first nitrogen introduction, and the barrier property of boron diffusion from the gate electrode is improved.

(Third embodiment)
FIG. 9 shows a method for manufacturing a semiconductor device (MOS transistor) according to the third embodiment of the present invention.

  As shown in FIG. 9, in the method for manufacturing a semiconductor device according to the third embodiment of the present invention, a silicon oxide film 402 having a thickness of 2 to 2.2 nm is formed on a Si substrate 401 by thermal oxidation. The silicon oxide film 402 may be formed by generating oxygen radicals or oxygen ions with plasma.

Next, nitrogen radicals or nitrogen ions are generated by plasma under conditions of microwave 1500 W, Ar / N ₂ gas, pressure 130 Pa, and Si substrate 401 temperature of 400 ° C., and nitrogen is introduced for 20 seconds to form a silicon oxynitride film. 403 is formed.

  Next, the silicon oxynitride film 404 is formed by wet etching from the upper surface (nitrogen introduction side) of the silicon oxynitride film 403 having the maximum nitrogen concentration peak to about 0.5 nm.

Next, the Si substrate 401 is heated to oxidize the surface region of the Si substrate by 0.1 to 0.2 nm with oxygen passed through the silicon oxynitride film 404 to form a gate insulating film 405 made of a silicon oxynitride film. Specifically, the surface region of the Si substrate is oxidized using a single-wafer lamp heating RTP apparatus under conditions of 800 to 1000 ° C., O ₂ gas, and 1 to 3 KPa.

  Although illustration of the subsequent steps is omitted, a polysilicon film is deposited on the gate insulating film 405 made of a silicon oxynitride film, the gate insulating film 405 made of the polysilicon film and the silicon oxynitride film is patterned, and the gate An electrode 406 is formed, and source / drain regions 407 are formed by impurity ion implantation using the gate electrode 406 as a mask and heat treatment (for example, RTA) for activation thereof.

  FIG. 10 shows a nitrogen profile of a gate insulating film made of a silicon oxynitride film in the semiconductor device (MOS transistor) according to the third embodiment of the present invention.

  As shown in FIG. 10, the maximum nitrogen concentration is 8 atm%, the maximum nitrogen concentration peak is the position at the interface between the gate insulating film and the gate electrode, and the nitrogen concentration at the interface between the gate insulating film and the Si substrate is lower than 1 atm%.

  According to the above, by slightly oxidizing the interface, the nitrogen concentration at the interface is reduced and the interface characteristics are improved.

(Fourth embodiment)
FIG. 11 shows a method of manufacturing a semiconductor device (MOS transistor) according to the fourth embodiment of the present invention.

  As shown in FIG. 11, in the method for manufacturing a semiconductor device according to the fourth embodiment of the present invention, a silicon oxide film 502 of 2 to 2.2 nm is formed on a Si substrate 501 by thermal oxidation. The silicon oxide film 502 may be formed by generating oxygen radicals or oxygen ions with plasma.

Next, nitrogen radicals or nitrogen ions are generated by plasma under conditions of microwave 1500 W, Ar / N ₂ gas, pressure 130 Pa, Si substrate 501 temperature of 400 ° C. on the silicon oxide film 502, and nitrogen is introduced for 20 seconds to form a silicon oxynitride film 503 is formed.

  Next, the silicon oxynitride film 504 is wet-etched from the upper surface (nitrogen introduction side) of the silicon oxynitride film 503 having the maximum nitrogen concentration peak to about 0.5 nm to form a silicon oxynitride film 504.

Next, the Si substrate 501 is heated and the silicon oxynitride film 504 is annealed with nitrous oxide (N ₂ O) to form a gate insulating film 505 made of a silicon oxynitride film. Specifically, annealing is performed under conditions of 800 to 1000 ° C., N ₂ O gas, and 60 to 100 KPa using a single-wafer type lamp heating RTP apparatus.

  Although illustration of the subsequent steps is omitted, a polysilicon film is deposited on the gate insulating film 505 made of a silicon oxynitride film, the gate insulating film 505 made of the polysilicon film and the silicon oxynitride film is patterned, and the gate An electrode 506 is formed, and source / drain regions 507 are formed by impurity ion implantation using the gate electrode 506 as a mask and heat treatment (for example, RTA) for activation thereof.

  FIG. 12 shows a nitrogen profile of a gate insulating film made of a silicon oxynitride film in a semiconductor device (MOS transistor) according to the fourth embodiment of the present invention.

  As shown in FIG. 12, the maximum nitrogen concentration is 9.5 atm%, the maximum nitrogen concentration peak is the position at the interface between the gate insulating film and the gate electrode, and the nitrogen concentration at the interface between the gate insulating film and the Si substrate is 3 atm%.

  According to the above, the maximum nitrogen concentration is increased by thermal nitriding, and the barrier property of boron diffusion from the gate electrode is improved.

  The method for manufacturing a semiconductor device according to the present invention achieves both the interface characteristics between the gate insulating film and the Si substrate and the barrier property of boron diffusion from the gate electrode, and is useful for semiconductor devices equipped with MOS transistors.

Manufacturing method of conventional semiconductor device (MOS transistor) Nitrogen concentration profile of gate insulating film 2 nm made of silicon oxynitride film formed by a conventional method of manufacturing a semiconductor device (MOS transistor) Nitrogen concentration profile of a 1.8 nm gate insulating film made of a silicon oxynitride film formed by a conventional method for manufacturing a semiconductor device (MOS transistor) Manufacturing method of semiconductor device (MOS transistor) of first embodiment of the present invention Graph of silicon oxynitride film 203 with time on the horizontal axis and wet etching amount on the vertical axis Nitrogen profile of gate insulating film made of silicon oxynitride film in semiconductor device (MOS transistor) of first embodiment of the present invention Manufacturing method of semiconductor device (MOS transistor) of second embodiment of the present invention Nitrogen profile of gate insulating film made of silicon oxynitride film in semiconductor device (MOS transistor) of second embodiment of the present invention Manufacturing method of semiconductor device (MOS transistor) of third embodiment of the present invention Nitrogen profile of gate insulating film made of silicon oxynitride film in semiconductor device (MOS transistor) of third embodiment of the present invention Manufacturing method of semiconductor device (MOS transistor) of fourth embodiment of the present invention Nitrogen profile of gate insulating film made of silicon oxynitride film in semiconductor device (MOS transistor) of fourth embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Si substrate 102 ... Silicon oxide film 103 ... Gate insulating film 104 made of silicon oxynitride film ... Gate electrode 105 ... Source / drain region 201 ... Si substrate 202 ... Silicon oxide film 203 ... Silicon oxynitride film 204 ... Silicon oxynitride Gate insulating film 205 made of a film ... Gate electrode 206 ... Source / drain region 301 ... Si substrate 302 ... Silicon oxide film 303 ... Silicon oxynitride film 304 ... Silicon oxynitride film 305 ... Gate insulating film 306 made of silicon oxynitride film ... Gate electrode 307 ... Source / drain region 401 ... Si substrate 402 ... Silicon oxide film 403 ... Silicon oxynitride film 404 ... Silicon oxynitride film 405 ... Gate insulating film 406 made of silicon oxynitride film ... Gate electrode 407 ... Source / drain region 501 ... Si substrate 502 ... Silic acid The gate insulating consisting film 503 ... silicon oxynitride film 504 ... silicon oxynitride film 505 ... silicon oxynitride film layer 506 ... the gate electrode 507 ... source and drain regions

Claims (6)

A semiconductor substrate;
A gate electrode provided on the semiconductor substrate;
A method for manufacturing a semiconductor device comprising a gate insulating film made of a silicon oxynitride film between the semiconductor substrate and the gate electrode,
A first step of forming a base silicon oxide film on a semiconductor substrate;
A second step of forming a silicon oxynitride film by introducing nitrogen into the silicon oxide film with nitrogen radicals or nitrogen ions generated by plasma;
A third step of removing the silicon oxynitride film to its maximum nitrogen concentration peak position;
A method of manufacturing a semiconductor device including: A semiconductor substrate;
A gate electrode provided on the semiconductor substrate;
A method for manufacturing a semiconductor device comprising a gate insulating film made of a silicon oxynitride film between the semiconductor substrate and the gate electrode,
A first step of forming a base silicon oxide film on a semiconductor substrate;
A second step of forming a silicon oxynitride film by introducing nitrogen into the silicon oxide film with nitrogen radicals or nitrogen ions generated by plasma;
A third step of removing the silicon oxynitride film to its maximum nitrogen concentration peak position;
A fourth step of introducing nitrogen into the silicon oxynitride film with nitrogen radicals or nitrogen ions less than the amount of nitrogen radicals or nitrogen ions generated by the plasma of the second step;
A method of manufacturing a semiconductor device including: A semiconductor substrate;
A gate electrode provided on the semiconductor substrate;
A method for manufacturing a semiconductor device comprising a gate insulating film made of a silicon oxynitride film between the semiconductor substrate and the gate electrode,
A first step of forming a base silicon oxide film on a semiconductor substrate;
A second step of forming a silicon oxynitride film by introducing nitrogen into the silicon oxide film with nitrogen radicals or nitrogen ions generated by plasma;
A third step of removing the silicon oxynitride film to its maximum nitrogen concentration peak position;
A fourth step of oxidizing the silicon oxynitride film with oxygen passed through the silicon oxynitride film by heat treatment of the semiconductor substrate;
A method of manufacturing a semiconductor device including: A semiconductor substrate;
A gate electrode provided on the semiconductor substrate;
A method for manufacturing a semiconductor device comprising a gate insulating film made of a silicon oxynitride film between the semiconductor substrate and the gate electrode,
A first step of forming a base silicon oxide film on a semiconductor substrate;
A second step of forming a silicon oxynitride film by introducing nitrogen with nitrogen radicals or nitrogen ions generated from the silicon oxide film by plasma;
A third step of removing the silicon oxynitride film to its maximum nitrogen concentration peak position;
A fourth step of annealing the silicon oxynitride film with nitrous oxide (N ₂ O);
A method of manufacturing a semiconductor device including: In the manufacturing method of the semiconductor device according to claim 1, 2, 3, 4,
In the third step, a semiconductor is characterized in that a wet etching time is taken in advance on the horizontal axis, and a graph in which the wet etching amount is taken on the vertical axis, and then the time point at which the etching rate changes is set as the wet etching setting time. Device manufacturing method. In the manufacturing method of the semiconductor device of Claim 1, 2, 3, 4, 5,
A method of manufacturing a semiconductor device, wherein the thickness of the gate insulating film is 2 nm or less, the maximum nitrogen concentration of the gate insulating film is 8 atm% or more, and the interface nitrogen concentration with the Si substrate is 3 atm% or less.

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