JP2001274260A - Semiconductor device and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device having a low breakdown voltage transistor having a stable characteristic without diffusion of boron in a polycrystalline silicon film which becomes a gate electrode to a semiconductor substrate and a high breakdown voltage transistor, having a gate insulting film whose film thickness is controlled on the same substrate. SOLUTION: An oxynitirde film 5 is formed in a low breakdown voltage transistor LMOS region and an oxide film 7 which becomes the gate insulating film of high breakdown voltage transistor HMOS is formed through a thermal oxidation processing. At that time, a low breakdown voltage transistor LMOS region is oxidized simultaneously and a laminated film, which becomes the gate insulating film 8 of the low breakdown voltage transistor and is constituted of the oxide film and the oxynitride film is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly to a semiconductor device having a low breakdown voltage transistor and a high breakdown voltage transistor on the same semiconductor substrate and a method of fabricating the same.

[0002]

2. Description of the Related Art Conventionally, the following method has been used to fabricate transistors having different breakdown voltage characteristics on the same semiconductor substrate.

A conventional method for manufacturing a semiconductor device will be described with reference to FIGS. 3 (a) to 3 (h). FIG. 3 shows a method of forming two transistors, a low breakdown voltage transistor LMOS and a high breakdown voltage transistor HMOS, on the same semiconductor substrate.

In the figure, 1 is a semiconductor substrate, 2 is an injection protection oxide film, 3 is an element isolation region, 4a and 4b are impurity layers, 9, 14, and 15 are resist patterns, 10 is a gate electrode, 11a and 11b are Source / drain regions of the low breakdown voltage transistor, 12a and 12b are source / drain regions of the high breakdown voltage transistor, 13 is a base gate oxide film,
Reference numeral 16 denotes a gate oxide film of a low breakdown voltage transistor, and 17 denotes a stacked gate oxide film of a high breakdown voltage transistor.

In the step shown in FIG. 3A, an injection protection oxide film 2 is formed on a semiconductor substrate 1 made of a silicon substrate on which an element isolation region 3 made of a LOCOS oxide film is formed.

Next, in a step shown in FIG. 3B, an impurity is ion-implanted into the semiconductor substrate 1 to form an impurity layer 4b for controlling the threshold value of the high breakdown voltage transistor.

Next, in the step shown in FIG. 3C, after removing the injection protection oxide film 2, the underlying gate oxide film 13 which becomes a part of the gate oxide film of the high breakdown voltage transistor is thermally oxidized.
To form

Next, in a step shown in FIG. 3D, after forming a resist pattern 14 on the high breakdown voltage transistor region, impurities are ion-implanted into the low breakdown voltage transistor region to control the threshold voltage of the low breakdown voltage transistor. Impurity layer 4a is formed. At this time, the impurity concentration of the impurity layer 4a is higher than that of the impurity layer 4b because the impurity concentration is such that the impurity is further implanted into the impurity layer 4b.

Next, in the step shown in FIG. 3E, after removing the resist pattern 14, a resist pattern 15 is formed again on the high-breakdown-voltage transistor region. The underlying gate oxide film 13 formed in the transistor region is selectively removed.

Next, in the step shown in FIG. 3F, after removing the resist pattern 15, a gate oxide film 16 serving as a gate insulating film of the low breakdown voltage transistor is formed in the low breakdown voltage transistor region by thermal oxidation. At the same time, the high-breakdown-voltage transistor region is also thermally oxidized to form a laminated gate oxide film 17 serving as a gate insulating film of the high-breakdown-voltage transistor, which is thicker than the gate oxide film 16 of the low-breakdown-voltage transistor. At this time, while the surface of the semiconductor substrate in the low-breakdown-voltage transistor region is exposed, the underlying gate oxide film 13 is formed in the high-breakdown-voltage transistor region, and the underlying gate oxide film 13 transmits the oxidizing species. Gate oxide film 1
6, the thickness of the stacked gate oxide film 17 is larger.

Next, in the step shown in FIG. 3 (g), a polycrystalline silicon film is deposited on the semiconductor substrate 1 on which the gate oxide film 16 and the laminated gate oxide film 17 are formed by a low pressure CVD method. A gate electrode forming resist pattern 9 is formed on the silicon film, and the polycrystalline silicon film is removed using the resist pattern 9 as a mask, thereby forming the gate electrodes 1 of the low breakdown voltage transistor and the high breakdown voltage transistor.
0 is formed.

Next, in the step shown in FIG. 3 (h), after removing the resist pattern 9, impurities are ion-implanted using the gate electrode as a mask to form a source / source of the low breakdown voltage transistor.
By forming the drain regions 11a and 11b and the source / drain regions 12a and 12b of the high breakdown voltage transistor, a semiconductor device having a low breakdown voltage transistor and a high breakdown voltage transistor on the same semiconductor substrate 1 is manufactured.

[0013]

However, in the conventional method of manufacturing a semiconductor device, when the gate oxide film of the low breakdown voltage transistor is reduced to, for example, about 5 nm, boron contained in the polycrystalline silicon film as the gate electrode is not used. Penetrates through the gate oxide film and diffuses into the semiconductor substrate. As a result, there is a problem that the impurity concentration of the channel region of the low breakdown voltage transistor changes and the transistor characteristics fluctuate. In addition, the laminated gate oxide film of the high breakdown voltage transistor
It is formed by two thermal oxidations of a first oxidation step of forming an underlying gate oxide film and a second oxidation step of forming a gate oxide film of a low-breakdown-voltage transistor, and the underlying gate oxide film transmits oxidizing species. In the second oxidation step, the film is easily oxidized, so that it is difficult to control the film thickness, and the film thickness tends to vary. Therefore, it is difficult to obtain stable high-breakdown-voltage transistor characteristics.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to prevent boron contained in a polycrystalline silicon film serving as a gate electrode from diffusing into a semiconductor substrate. A semiconductor device having stable transistor characteristics by manufacturing a low breakdown voltage transistor having a gate insulating film formed thereon and a high breakdown voltage transistor having a gate insulating film having a controlled thickness on the same semiconductor substrate, and manufacturing the same. Is to provide a way.

[0015]

In order to achieve the above-mentioned object, the present invention provides means for changing the thickness of a gate insulating film between a low breakdown voltage transistor and a high breakdown voltage transistor having different threshold voltages. Is realized by
The gate insulating film of the low-breakdown-voltage transistor is constituted by a laminated film in which an insulating film having low permeability of oxidizing species and impurities is formed thereon, and the gate insulating film of the high-breakdown-voltage transistor is constituted by a single-layer film.

A semiconductor device according to the present invention is a semiconductor device having a low breakdown voltage transistor and a high breakdown voltage transistor.
The low-breakdown-voltage transistor has a first gate insulating film formed of a laminated film in which an insulating film having low permeability of oxidizing species and impurities is formed as an upper layer, and the second gate insulating film has a high-breakdown-voltage transistor formed of a single-layer film.
Wherein the thickness of the second gate insulating film is larger than the thickness of the first gate insulating film.

In the above semiconductor device, the insulating film is formed of an oxynitride film, the first gate insulating film is formed of a laminated film of a lower first oxide film and an upper oxynitride film, The film is composed of a single-layer film made of a second oxide film.

In this semiconductor device, the first gate insulating film of the low-breakdown-voltage transistor is formed of a laminated film in which an insulating film having low permeability of oxidizing species and impurities is formed as an upper layer. Even if it is formed of a polycrystalline silicon film containing, since penetration of boron can be prevented by an insulating film having low permeability, stable low breakdown voltage transistor characteristics can be obtained. Further, since the second gate insulating film of the high-breakdown-voltage transistor is formed of a single-layer film, it is possible to easily control the film thickness and obtain stable high-breakdown-voltage transistor characteristics.

According to the method of manufacturing a semiconductor device of the present invention, there is provided a method of manufacturing a semiconductor device having a low-breakdown-voltage transistor and a high-breakdown-voltage transistor. Forming a part of the first gate insulating film and forming an insulating film to be an upper layer film; and exposing a semiconductor substrate surface in a high withstand voltage transistor region and thermally oxidizing the semiconductor substrate to form a second withstand voltage of the high withstand voltage transistor. Forming a second oxide film which is to be a gate insulating film, and simultaneously thermally oxidizing the low-breakdown-voltage transistor region to form a lower-layer film which is a part of the first gate insulating film of the low-breakdown-voltage transistor under the insulating film; Forming a first oxide film that becomes a second oxide film by thermal oxidation as compared with a first gate insulating film made of a laminated film of an insulating film and a first oxide film. It is characterized in that the direction of thickness of the second gate insulating film made of a single layer film of monolayer is formed thickly.

In the above method of manufacturing a semiconductor device, the insulating film is formed of an oxynitride film, and the first gate insulating film is formed of a laminated film including a lower first oxide film and an upper oxynitride film.

In the method of manufacturing a semiconductor device, the oxynitride film is formed in an atmosphere containing at least NO.

In this method of manufacturing a semiconductor device, the semiconductor substrate is thermally oxidized in a state where an insulating film having low permeability of oxidizing species and impurities is formed on the semiconductor substrate in the low breakdown voltage transistor region, thereby forming the low breakdown voltage transistor region. The thickness of the second gate oxide film formed in the high breakdown voltage transistor region is smaller than the thickness of the first gate insulating film formed of the stacked film of the insulating film and the first oxide film. The second gate insulating film can be formed to be thicker. Moreover, the thin first gate insulating film of the low breakdown voltage transistor is
Since the upper layer is formed of a stacked film including an insulating film having low permeability of oxidized species and impurities and the first oxide film, even if the gate electrode is formed of a polycrystalline silicon film containing boron, low permeability is obtained. Through the insulating film, penetration of boron can be prevented.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a semiconductor device and a method of manufacturing the same according to the present invention will be described below with reference to FIG. 1A to 1G are cross-sectional views illustrating the steps of manufacturing the semiconductor device according to the present embodiment. FIG. 1 shows a method of forming two transistors, a low breakdown voltage transistor LMOS and a high breakdown voltage transistor HMOS, on the same semiconductor substrate.

1A to 1G, reference numeral 1 denotes a semiconductor substrate, 2 denotes an implantation protection oxide film, 3 denotes an element isolation region, 4a denotes an impurity layer for controlling a threshold voltage of a low breakdown voltage transistor, and 4b.
Are impurity layers for controlling the threshold voltage of the high breakdown voltage transistor;
Is an oxynitride film, 6 and 9 are resist patterns, 7 is a gate insulating film of a high voltage transistor, 8 is a gate insulating film of a low voltage transistor, 10 is a gate electrode, 11a and 11b are source / drain regions of the low voltage transistor, Reference numerals 12a and 12b denote source / drain regions of the high breakdown voltage transistor.

First, in the step shown in FIG. 1A, an element isolation region 3 made of a LOCOS oxide film is formed on the surface of a semiconductor substrate 1 made of a silicon substrate, and then implanted into active regions of a low breakdown voltage transistor and a high breakdown voltage transistor. Protective oxide film 2
Is formed to a thickness of 20 nm.

Next, in the step shown in FIG. 1B, impurity ions are selectively implanted into the semiconductor substrate 1 under the implantation protection oxide film 2 in each of the low breakdown voltage transistor region and the high breakdown voltage transistor formation region. Thus, an impurity layer 4a for controlling the threshold voltage of the low breakdown voltage transistor is formed in the low breakdown voltage transistor region, and an impurity layer 4b for controlling the threshold value of the high breakdown voltage transistor is formed in the high breakdown voltage transistor formation region. Thereafter, the injection protection oxide film 2 is dissolved and removed with an HF aqueous solution.

Next, in the step shown in FIG.
4a, 4b having a thickness of about 3 nm by oxynitriding.
An oxynitride film 5 is formed. This oxynitride film 5 is made of, for example, N
O, N _TwoO, NH_ThreeGas containing nitrogen atom such as N_Two, O_Two
Formed in an atmosphere in which gases such as
It becomes a gate insulating film of the transistor. This acid
The nitride film 5 is impure due to the inclusion of nitrogen.
Low permeability of the material, for example, a polycrystalline silicon
Oxynitride film even if boron is contained as an impurity in the capacitor film
5, it is difficult to penetrate through the semiconductor substrate 1.
Can be prevented from spreading. Film thickness of this oxynitride film 5
Is 1 to 10 nm depending on the characteristics of the low breakdown voltage transistor.
It is preferable to form in the range of.

Next, in a step shown in FIG. 1D, a resist pattern 6 covering at least the low-breakdown-voltage transistor region and opening the high-breakdown-voltage transistor region is formed on the semiconductor substrate 1. Is used as a mask to dissolve and remove the oxynitride film 5 with an HF aqueous solution to expose the surface of the semiconductor substrate 1 in the high breakdown voltage transistor region. After that, the resist pattern 6 is removed.

Next, in the step shown in FIG. 1E, an oxide film serving as a gate insulating film 7 of the high breakdown voltage transistor is formed to a thickness of about 15 nm on the surface of the semiconductor substrate 1 where the high breakdown voltage transistor region is exposed by performing a thermal oxidation process. Form. The thickness of the gate insulating film 7 of the high breakdown voltage transistor is preferably in the range of 7 to 30 nm according to the characteristics of the high breakdown voltage transistor. By this thermal oxidation treatment, the low-breakdown-voltage transistor region is also oxidized at the same time, and a laminated film including an oxide film and an oxynitride film which is to be the gate insulating film 8 of the low-breakdown-voltage transistor is formed to a thickness of about 5 nm. At this time, since the oxynitride film 5 having low permeability of the oxidizing species including oxygen is formed in the low breakdown voltage transistor region, the oxynitride film 5 is more oxidized than the high breakdown voltage transistor region in which the surface of the semiconductor substrate 1 is exposed. Since the oxidizing species transmitted through the film 5 and supplied to the surface of the semiconductor substrate 1 is suppressed, the increase in film thickness due to the thermal oxidation treatment is small.

Next, in the step shown in FIG. 1F, after a polycrystalline silicon film having a thickness of about 250 nm is deposited by the CVD method, a resist pattern 9 for forming a gate electrode is formed.
Is formed, and etching is performed using this resist pattern 9 as a mask to form a gate electrode 1 made of a polycrystalline silicon film.
0 is formed. The polycrystalline silicon film serving as the gate electrode 10 contains impurities such as boron for increasing conductivity. Thereafter, the resist pattern 9 is removed.

Next, in the step shown in FIG. 1 (g), impurities are ion-implanted using the gate electrode 10 as a mask, and the source / drain regions 11a and 11b of the low breakdown voltage transistor and the source / drain region of the high breakdown voltage transistor are formed. 12a,
By forming 12b, a semiconductor device having a low breakdown voltage transistor and a high breakdown voltage transistor on the same semiconductor substrate 1 is manufactured.

FIG. 2 shows the change in the thickness of the oxide film with respect to the oxidation time depending on the state of the underlying substrate before the thermal oxidation treatment. That is, since the oxidation rate of the silicon substrate covered with the oxynitride film having low oxidizing species permeability is lower than the oxidation rate of the state where the silicon substrate surface is exposed, the silicon substrate becomes the gate insulating film 8 of the low breakdown voltage transistor. The single-layer film serving as the gate insulating film 7 of the high breakdown voltage transistor can be formed thicker by the stacked film. In particular, an oxynitride film formed in an atmosphere containing NO has lower permeability to oxidizing species than an oxynitride film formed in an atmosphere containing N ₂ O, and has a very small increase in film thickness due to thermal oxidation. Since the gate insulating film of the high withstand voltage transistor can be selectively formed without increasing the gate insulating film of the withstand voltage transistor, it is preferable as the gate insulating film of the low withstand voltage transistor.

The low breakdown voltage transistor and the high breakdown voltage transistor manufactured in this manner have stable characteristics, and it has been confirmed that the high breakdown voltage transistor is particularly excellent in the breakdown voltage.

Although the present embodiment has been described using an oxynitride film as the insulating film having low oxidizing species and impurities,
An insulating material having low permeability to oxidized species and boron as an impurity may be used instead.

In this embodiment, two types of transistors are formed on the same semiconductor substrate.
Between the step shown in (d) and the step shown in FIG. 1E, two steps of forming a gate insulating film and selectively removing the gate insulating film from a predetermined region are performed at least once. Accordingly, three or more types of transistors can be formed over the same semiconductor substrate.

[0036]

According to the semiconductor device and the method of manufacturing the same of the present invention, it is possible to form an oxynitride film having low permeability of oxidizing species and impurities on a semiconductor substrate in a low breakdown voltage transistor region.
By forming the gate insulating film of the high-breakdown-voltage transistor by the thermal oxidation treatment, the gate insulating film of the high-breakdown-voltage transistor which is thicker than the gate insulating film of the low-breakdown-voltage transistor can be selectively formed. In addition, since the gate insulating film of the low-breakdown-voltage transistor is formed as a laminated film formed of an oxynitride film having low impurity permeability in the upper layer, even if the gate electrode is formed of a silicon material containing impurities such as boron, The penetration and diffusion of impurities into the substrate can be prevented. Therefore, a semiconductor device in which a low breakdown voltage transistor and a high breakdown voltage transistor having stable transistor characteristics are formed over the same semiconductor substrate can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a manufacturing process of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a change in film thickness with respect to oxidation time when a silicon substrate surface is exposed and when an oxynitride film is formed in a manufacturing process of a semiconductor device according to an embodiment of the present invention.

FIG. 3 is a sectional view showing a manufacturing process of a conventional semiconductor device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Injection protection oxide film 3 Element isolation region 4a Impurity layer for threshold control of low voltage transistor 4b Impurity layer for threshold control of high voltage transistor 5 Oxynitride film 6 Resist pattern 7 High voltage transistor Gate insulating film 8 Gate insulating film of low breakdown voltage transistor 9 Resist pattern 10 Gate electrode 11a, 11b Source / drain region of low breakdown voltage transistor 12a, 12b Source / drain region of high breakdown voltage transistor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F048 AA05 AA07 AC01 AC06 BB05 BB07 BB11 BB12 BB16 BB17 BD04 BG12 5F058 BA01 BA06 BC02 BC11 BD01 BD04 BD15 BF62 BF64 BF80

Claims (5)

[Claims] 1. A semiconductor device having a low breakdown voltage transistor and a high breakdown voltage transistor, wherein the low breakdown voltage transistor is a first gate insulating film comprising a laminated film in which an insulating film having low permeability of oxidizing species and impurities is formed as an upper layer. Wherein the high breakdown voltage transistor has a second gate insulating film made of a single-layer film, and the thickness of the second gate insulating film is greater than the thickness of the first gate insulating film. A semiconductor device characterized by being thick. 2. The semiconductor device according to claim 1, wherein the insulating film is formed of an oxynitride film, and the first gate insulating film is formed of a lower first oxide film and an upper oxynitride film. Wherein the second gate insulating film is a single-layer film made of a second oxide film. 3. A method of manufacturing a semiconductor device having a low-breakdown-voltage transistor and a high-breakdown-voltage transistor, wherein the first gate insulating film has low permeability of oxidizing species and impurities on at least the semiconductor substrate in the low-breakdown-voltage transistor region. Forming a part of the insulating film to be an upper layer film, and exposing the semiconductor substrate surface in the high withstand voltage transistor region, and then thermally oxidizing the second gate insulating film of the high withstand voltage transistor At the same time as forming the second oxide film, the low breakdown voltage transistor region is thermally oxidized to form a part of the first gate insulating film of the low breakdown voltage transistor under the insulating film, Forming a first oxide film, wherein the thermal oxidation reduces the thickness of the first gate insulating film made of a laminated film of the insulating film and the first oxide film. Base, the method of manufacturing a semiconductor device characterized by better film thickness of the second gate insulating film made of a single layer film of the second oxide film is formed thickly. 4. The method of manufacturing a semiconductor device according to claim 3, wherein said insulating film is made of an oxynitride film, and said first gate insulating film is a lower first oxide film and an upper oxynitride film. A method for manufacturing a semiconductor device, comprising: a laminated film comprising: 5. The method for manufacturing a semiconductor device according to claim 4, wherein said oxynitride film is formed in an atmosphere containing at least NO.