JPH097967A - Fabrication method of semiconductor device - Google Patents

Abstract

PURPOSE: To fabricate a semiconductor device including a channel stopper and a high resistance element under a LOCOS oxide film formed through ion implantation of boron. CONSTITUTION: LOCOS oxidization is effected with two-step oxidization of wet oxidization and dry oxidization after there is applied twice boron doping at low energy and high energy to achieve channel stopper formation of a boron diffusion layer and the boron doping at high energy. Thereafter, a LOCOS oxide film 39 is formed with two-step oxidization of wet oxidization and dry oxidization to form a high resistance element 1 under the LOCOS oxide film 39 by making use of a boron diffusion layer 43. Hereby, deterioration of withstand voltage of the channel stopper part in contact with a high concentration N<+> diffusion layer is reduced, and a boron concentration diffusion layer also securely processing a channel stopper effect can be accurately formed. Further, the high resistance element 1 can be formed under the LOCOS oxide film 39 with reduced variations of the resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device.
The present invention relates to a method of manufacturing a semiconductor device including a step of forming a high resistance element by a channel stopper under an OCOS oxide film and a diffusion layer under a LOCOS oxide film.

[0002]

2. Description of the Related Art With higher integration and higher performance of semiconductor devices such as LSI, an effective element isolation method by ion implantation of LOCOS method and boron and a field region of a thick oxide film formed by the LOCOS method are formed. High integration has been achieved by forming a high resistance element using a boron diffusion layer.

By the LOCOS method and boron ion implantation, L
A conventional element isolation method for forming a channel stopper under the OCOS oxide film will be described with reference to FIG. First, as shown in FIG. 5A, an oxide film 31 is formed on the surface of a semiconductor substrate 11 by thermal oxidation, and a SiN film 32 is deposited thereon by plasma CVD, and a field of a semiconductor integrated circuit is formed by photolithography. Area SiN3
2 is patterned, and then boron ions are implanted to form a boron implantation region 33. Next, as shown in FIG. 5B, after the implanted ions are activated by heat treatment with an inert gas, the SiN film 32 is used as an oxidation mask for an oxidation mask, and the LOCOS oxide film 34 is formed into a semiconductor by thermal oxidation. It is formed on the substrate 11. In this way, a channel stopper is formed by the boron diffusion layer 35 below the LOCOS oxide film 34 in the field region.

Further, a high resistance element using a diffusion layer of boron has been formed under the LOCOS oxide film in the field region of the semiconductor integrated circuit to achieve high integration of the semiconductor integrated circuit. This manufacturing method will be described with reference to FIG. . First, as shown in FIG. 6A, an N-type impurity is diffused into the P-type semiconductor substrate 11 to form an N well 12.
A thermal oxide film 31 is formed on the mold semiconductor substrate 11, and a SiN film 32 is further formed thereon by a plasma CVD method. Next, the SiN film 32 is patterned by photolithography to remove the SiN film 32 in the portion to be the field region.

After that, as shown in FIG. 6 (b),
A photoresist 36 is applied, and the photoresist 36 is patterned using a boron ion implantation mask for forming a high resistance element in the boron diffusion layer under LOCOS oxidation. Next, in order to form a desired high resistance, boron is ion-implanted to form a boron implantation region 37. Next, as shown in FIG. 6C, after removing the photoresist 36, a heat treatment for activating the ion-implanted boron is performed.
After that, the SiN film 32 is used as an antioxidation film as an oxidation mask and is oxidized by a wet oxidation method to form a LOCOS oxide film 34. In this way, the LOCOS oxide film 3
Underneath 4, the high resistance element 1 is formed by the boron diffusion layer 38.

However, the problem in forming the channel stopper under the LOCOS oxide film by the above boron ion implantation is that the boron ion implantation dose is large.
Although the effect of the channel stopper is enhanced, the breakdown voltage at the portion (not shown) in contact with the high concentration N ⁺ diffusion layer is reduced. on the other hand,
If the dose of boron ion implantation is small, the LOCO
A large amount of boron is taken into the oxide film during S oxidation, and further, the deviation coefficient of boron is small, which results in LOCOS.
The boron concentration decreases at the interface under the oxide film, and the effect of the channel stopper decreases. Further, in the semiconductor integrated circuit of the MOS transistor, the decrease in the boron concentration under the bird's beak that occurs around the LOCOS region causes the channel width variation of the gate electrode and deteriorates the MOS characteristics.

Further, in the formation of the high resistance element under the LOCOS oxide film in the field region by the boron ion implantation as described above, the variation of the resistance value due to the substantial variation of the boron concentration of the diffusion layer is a serious problem. Is this variation in the resistance value due to a substantial variation in the boron concentration due to the diffusion of impurities serving as a dopant of silicon in the LOCOS step and the heat treatment step before the LOCOS step?
Alternatively, due to the deviation coefficient of boron, it is caused by a variation in the degree of incorporation of boron into the oxide film during the LOCOS process. As a result, the resistance value of the high resistance element varies, and the manufacturing yield of the semiconductor device is reduced.

[0008]

SUMMARY OF THE INVENTION According to the present invention, when the LOCOS oxidation is performed after the ion implantation as described above and the channel stopper is formed by the boron diffusion layer under the LOCOS oxide film, it is adjacent to the high concentration N ⁺ diffusion layer. An object of the present invention is to provide a method for manufacturing a semiconductor device, which suppresses the breakdown voltage reduction at a desired position and enables accurate boron concentration control for ensuring the effect of a channel stopper. Further, according to the present invention, when the LOCOS oxidation is performed after the ion implantation as described above to form a high resistance element by the boron diffusion layer under the LOCOS oxide film, variation in boron concentration in the boron diffusion layer under the LOCOS oxide film is suppressed. Therefore, it is an object of the present invention to provide a method for manufacturing a semiconductor device that can suppress variations in resistance value of a high resistance element.

[0009]

A method for manufacturing a semiconductor device according to the present invention is proposed to solve the above-mentioned problems, and an antioxidation film is formed on a semiconductor substrate and formed on the semiconductor substrate. The oxidation prevention film, which becomes the field region of the semiconductor integrated circuit, is opened by photolithography,
A method of manufacturing a semiconductor device, wherein a LOCOS oxide film is formed by thermal oxidation using the anti-oxidation film as a mask, and a channel stopper is formed under the LOCOS oxide film. Ion implantation for implanting into the surface of the semiconductor substrate with low energy, and LO
Ion implantation is performed with high energy to a depth from the surface of the semiconductor substrate corresponding to a value approximately half the thickness of the COS oxide film, and then thermal oxidation is performed using the antioxidant film as a mask.
It is characterized in that an OCOS oxide film is formed. A method for manufacturing a semiconductor device of the present invention is the above-described method for manufacturing a semiconductor device, in which a LOCOS oxidation step is performed in this order by a wet oxidation step using water vapor and oxygen gas, and a dry oxidation step using only oxygen gas, The LOCOS oxide film is formed.

Furthermore, the method of manufacturing a semiconductor device of the present invention is a method of manufacturing a semiconductor device in which a high resistance element is formed by a diffusion layer under a LOCOS oxide film in a field region in a semiconductor integrated circuit formed on a semiconductor substrate. Then, after ion implantation of boron with high energy is implanted into the depth from the surface of the semiconductor substrate corresponding to approximately half the thickness of the LOCOS oxide film to be formed, LOCOS oxidation is performed by thermal oxidation using the antioxidant film as a mask. By forming a film, LOC
It is characterized in that a high resistance is formed by the diffusion layer under the OS oxide film. A method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device in which a high resistance element is formed of a diffusion layer below the LOCOS oxide film.
The LOCOS oxide film is formed by performing a COS oxidation process in the order of a wet oxidation process using water vapor and oxygen gas and a dry oxidation process using only oxygen gas.

[0011]

According to the method of manufacturing a semiconductor device of the present invention, the LO
By suppressing the state where boron is eaten into the oxide film during COS oxidation as much as possible, it is possible to stably and accurately form the channel stopper and the high resistance element by the boron diffusion layer under the LOCOS oxide film. In general, when a silicon semiconductor substrate containing boron is oxidized, more boron is deviated in the oxide film due to the deviation coefficient of boron. Therefore, in order to reduce the amount of boron taken into the oxide film, the thickness (L
Boron is ion-implanted with high energy to a depth of at least 40% of the OCOS oxide film thickness) and then thermally oxidized using the antioxidant film as a mask to form the LOCOS oxide film. The amount eaten by the LOCOS oxide film can be suppressed as much as possible.

Further, it is known that the deviation coefficient of boron is given by the following equation, depending on the difference in oxidation conditions. Deviation coefficient m during wet oxidation (impurity concentration in Si and SiO ₂
The ratio of the impurity concentration in) is m = 104.0 EXP (-0.66 eV / kT) The deviation coefficient m during dry oxidation is m = 13.4 EXP (-0.33 eV / kT) When performing LOCOS oxidation, the deviation coefficients m during wet oxidation and during dry oxidation are m = 0.255 and m = 0.663, respectively. Therefore,
Dry oxidation requires less incorporation of boron into the oxide film. Normally, a thick LOCOS oxide film is formed by wet oxidation, which has a high oxidation rate due to workability. However, in consideration of the above, from the surface of the semiconductor substrate corresponding to about half the value of the LOCOS oxide film thickness. After implanting boron ions with high energy to the depth of
If the OS oxidation process is performed by a wet oxidation process using water vapor and oxygen gas and a dry oxidation process using only oxygen gas in this order to form the LOCOS oxide film, the LOCOS film is formed.
A high resistance element formed of a boron diffusion layer below the oxide film can be stably formed with a resistance value having little variation, and can be formed with good workability.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. It should be noted that the same components as those in FIGS. 5 and 6 referred to in the description of the prior art are designated by the same reference numerals.

Example 1 This example is an LO method in a method for manufacturing a semiconductor integrated circuit.
This is an example in which the present invention is applied to the element isolation method by the COS method and boron ion implantation, which will be described with reference to FIGS. First, as shown in FIG.
The oxide film 3 having a thickness of about 30 nm is formed on the surface of the semiconductor substrate 11.
1 is formed by thermal oxidation, a SiN film 32 having a thickness of about 200 nm is deposited thereon by a plasma CVD method, and a photoresist 37 is applied thereon with a thickness of 1.5 μm. Next, in order to remove the SiN film 32 in the field region of the semiconductor integrated circuit, first the photoresist 37 is removed.
Is patterned by the lithography method, and then the SiN film 32 is etched by the RIE method using the photoresist 37 as a mask.

Next, using the photoresist 37 and the SiN film 32 as a mask, the oxide film 31 on the P-type semiconductor substrate 11 is used.
Through boron ion implantation into the P-type semiconductor substrate 11 at a dose amount of about 2E13 / cm ² and energy of about 20 KeV, and low-energy boron implantation to a shallower portion (about 60 nm) of the surface of the P-type semiconductor substrate 11. Area 3
3 is formed. After that, as shown in FIG. 1B, high-energy boron ion implantation is performed to form a high-energy boron implantation region 38. The energy of boron ions at the time of implantation is LOCO formed later.
Determined from the S oxide film thickness, for example, the LOCOS oxide film thickness is about 6
When the thickness is set to 00 nm, L is less than the surface of the P-type semiconductor substrate 11.
The energy is set such that boron ions are implanted at a depth of about 300 nm, which is about half the thickness of the OCOS oxide film. This energy value is about 100 K when the oxide film 31 is taken into consideration.
eV. At this time, the dose amount of boron ions is set to about 2E13 / cm ^{2 in} consideration of the channel stopper effect and the fact that the breakdown voltage does not decrease at the portion in contact with the N ⁺ high-concentration impurity diffusion region (not shown). .

Next, the photoresist 37 is removed, and about 1 is used to activate the boron in the low energy boron implantation region 33 and the high energy boron implantation region 38.
Heat treatment is performed at 000 ° C. for 10 minutes. Then SiN film 3
Wet oxidation method in which 2 is used as an anti-oxidation mask and, as an example, a gas in which hydrogen gas and oxygen gas are mixed at a ratio of 1: 1.1 is burned in an oxidizing furnace to oxidize in an atmosphere of steam and oxygen. Oxidize for about 160 minutes at about 950 ° C, and then dry oxidize only with oxygen gas for about 950
1 hour at 30 ° C for about 6 minutes as shown in Fig. 1 (c).
A LOCOS oxide film 39 of 00 nm is formed. When the LOCOS oxidation is performed in this way, the boron in the boron-implanted regions 33 and 38, which has been implanted by the low energy and the high energy, is partially taken into the oxide film and diffuses in the depth direction and the plane direction. A boron diffusion layer 40 is formed under the oxide film 39.

At this time, the former boron in the low-energy boron-implanted region 33, which has been implanted into the surface of the P-type semiconductor substrate 11, is also effectively diffused under the bird's beak portion 41 of the LOCOS oxide film 39 to be a channel stopper. The function of can be surely provided. In the latter case, boron in the boron-implanted region 38 due to high energy is hardly taken into the oxide film at the time of LOCOS oxidation, and the LOCOS of the LOCOS determined by the relationship between the deviation coefficient of boron is determined by the two-step oxidation of wet oxidation and dry oxidation. The decrease in the concentration at the interface is reduced, and the desired boron concentration determined in terms of the channel stopper effect and the breakdown voltage can be accurately obtained. When the above-mentioned double implantation of boron ions and two-stage LOCOS oxidation are performed, the LOC
FIGS. 2A and 2B show the boron concentration distributions of the OS oxide film 39 and the P-type semiconductor substrate 11 in comparison with the conventional method. Here, FIG. 2A shows the case of the first embodiment, and FIG.
(B) is the case of the conventional example. As is clear from FIG. 2, in the case of the first embodiment, the amount of boron taken into the LOCOS oxide film is small, and the boron concentration at the interface of LOCOS is not lowered so that the desired boron concentration can be easily obtained.

Embodiment 2 This embodiment is an example in which the present invention is applied to the case where a high resistance element is formed under the LOCOS oxide film in the field region in the method of manufacturing a semiconductor integrated circuit, and FIG.
This will be described with reference to (c) and FIG. In this embodiment, first, as shown in FIG. 3A, the N-type impurity is diffused in the P-type semiconductor substrate 11 by a normal method, and the film thickness is formed on the P-type semiconductor substrate 11 in which the N well 12 is formed. 30 nm thermal oxide film 3
1 is formed, and Si is further formed thereon by plasma CVD.
The N film 32 is formed to a film thickness of about 200 nm. Next, the SiN film 13 is patterned by photolithography to remove the SiN film 32 in the portion to be the field region.

After that, as shown in FIG. 3 (b),
Photoresist 36 is applied to a film thickness of about 1.5 μm, and L
The photoresist 36 is patterned using a photomask for boron ion implantation for forming a high resistance element in the boron diffusion layer under the OCOS oxide film. Next, in order to form a desired high resistance, the pattern shape of the photoresist 36 and L
The boron dose determined in consideration of OCOS oxidation and the subsequent heat treatment, for example, 6E13 / cm ² , and the energy is about half the film thickness of the LOCOS oxide film to be formed thereafter, for example, about 600 nm. Boron is implanted into the P-type semiconductor substrate 11 using the photoresist 36 as a mask at an energy of about 100 KeV that gives a projection range to form a boron implantation region 42.

Next, after the photoresist 36 is stripped off, at a temperature of about 1000.degree.
Heat treatment for 1 minute. Then, subsequently, the SiN film 32 is formed.
Is used as an anti-oxidation mask, and as an example, a gas in which hydrogen gas and oxygen gas are mixed at a ratio of 1: 1.1 is burned in an oxidizing furnace to perform oxidation in an atmosphere of steam and oxygen. , Oxidize at about 950 ° C for 160 minutes, and then dry oxidize only with oxygen gas at about 950 ° C
For 30 minutes, and as shown in Fig. 3 (c), about 60
A LOCOS oxide film 39 of 0 nm is formed. By forming the high resistance element 1 by the boron diffusion layer 43 under the LOCOS oxide film 39 by the above-described boron ion implantation method and LOCOS oxidation method, the amount of boron taken into the LOCOS oxide film is reduced. Further, it is possible to reduce the drop in boron concentration at the LOCOS interface due to the deviation coefficient of boron, to stably form the high resistance element 1 having a desired resistance value with little variation, and to perform wet oxidation of LOCOS oxidation. There is almost no effect on workability due to the two-stage oxidation of dry oxidation.

High resistance element 1 under the LOCOS oxide film described above.
After the formation, the P-channel MOS transistor 2 is formed in the region of the N-well 31 of the P-type semiconductor substrate 11 and the N-channel MOS transistor (not shown) is formed in the P-type semiconductor substrate 11 by the conventional method. Then, a contact window is opened, electrodes are formed, and a semiconductor integrated circuit as shown in FIG. 4 is manufactured. As described above, the manufacturing method described in the two examples of the present invention is not limited to these examples. For example, wet oxidation at the time of LOCOS oxidation may use steam by heating distilled water, and CVD SiO is used as a mask for high-energy boron implantation.
_Two membranes may be used. In addition, the manufacturing conditions of boron ion implantation and LOCOS oxidation can be appropriately changed within the scope of the technical idea of the present invention.

[0022]

As is apparent from the above description, the channel stopper formation under the LOCOS oxide film according to the method of manufacturing a semiconductor device of the present invention is performed by wet oxidation after boron ion implantation with low energy and high energy. By adopting the two-step oxidation method of dry oxidation, the decrease in breakdown voltage at a portion adjacent to the high-concentration N ⁺ diffusion layer was suppressed, and a channel stopper function under the LOCOS oxide film including the bird's beak portion was surely provided. Enables accurate boron concentration control. Further, according to the method for manufacturing a semiconductor device of the present invention, a high resistance element is formed by a boron diffusion layer under a LOCOS oxide film by performing a two-step oxidation method of wet oxidation and dry oxidation after ion implantation of boron with high energy. By doing so, a high resistance element under the LOCOS oxide film having a desired resistance value with less variation can be stably formed, and the manufacturing yield of semiconductor devices can be improved.

[Brief description of drawings]

1A and 1B are schematic cross-sectional views for explaining the steps of Example 1 to which the present invention is applied, in the order of the steps, where FIG. 1A is a state in which a boron implantation region is formed by low energy boron ion implantation, and FIG. A state in which a boron-implanted region is formed by high-energy boron ion implantation, and (c) is a state in which a LOCOS oxidation is performed to form a boron diffusion layer.

FIG. 2 shows a boron concentration distribution of a LOCOS oxide film and a P-type semiconductor substrate when LOCOS oxidation is performed.
(A) is the case of the present invention, and (b) is the conventional case.

3A and 3B are schematic cross-sectional views illustrating the steps of Example 2 to which the present invention is applied, in the order of the steps, where FIG. 3A is a state in which a SiN film as an antioxidant film is patterned, and FIG. 3B is high energy boron. A state where a boron implantation region is formed by ion implantation is shown, and (c) is a state where a LOCOS oxidation is performed to form a boron diffusion layer.

FIG. 4 is a schematic cross-sectional view of a semiconductor integrated circuit having a high resistance element under a LOCOS oxide film according to a second embodiment of the present invention.

5A to 5C are schematic cross-sectional views illustrating a conventional step of forming a channel stopper under a LOCOS oxide film, in order of the steps.
(A) is a state in which a boron implantation region is formed by low-energy boron ion implantation, and (b) is a state in which a boron diffusion layer is formed by LOCOS oxidation.

6A to 6C are schematic cross-sectional views illustrating a conventional high resistance element formation process under a LOCOS oxide film in the order of the process,
Is a state in which the SiN film of the antioxidant film is patterned,
(B) shows a state in which a boron-implanted region is formed by low-energy boron ion implantation, and (c) shows a state in which a high-resistance element is formed by LOCOS oxidation and a boron diffusion layer.

[Explanation of symbols]

 1 High-resistance element under LOCOS oxide film 2 MOS transistor 11 P-type semiconductor substrate 12 N well 31 Oxide film 32 SiN film 39 LOCOS oxide film 40 Channel stopper 43 High-resistance element

Claims (4)

[Claims] 1. An anti-oxidation film is formed on a semiconductor substrate, and the anti-oxidation film to be a field region of a semiconductor integrated circuit formed on the semiconductor substrate is opened by photolithography to serve as a channel stopper in the field region. In a method of manufacturing a semiconductor device, in which boron is ion-implanted, thermal oxidation is performed using the anti-oxidation film as a mask to form a LOCOS oxide film, and a channel stopper is formed under the LOCOS oxide film. At the time of implantation, ion implantation is performed with low energy on the surface of the semiconductor substrate, and ion implantation is performed with high energy at a depth from the surface of the semiconductor substrate corresponding to approximately half the LOCOS oxide film thickness. The LOCOS oxide film is formed by thermal oxidation using an antioxidant film as a mask. Method of manufacturing a body apparatus. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the LOCOS oxidation step is performed by a wet oxidation step using water vapor and oxygen gas and a dry oxidation step using only oxygen gas in this order to form the LOCOS oxide film. A method of manufacturing a semiconductor device, which comprises forming the semiconductor device. 3. A method of manufacturing a semiconductor device in which a high resistance element is formed of a diffusion layer under a LOCOS oxide film in a field region in a semiconductor integrated circuit formed on a semiconductor substrate, wherein the LOCOS oxide film thickness is about half the thickness of the LOCOS oxide film. After implanting boron ions with a high energy into the depth from the surface of the semiconductor substrate corresponding to the value of, the LOCOS oxide film is formed by thermal oxidation using the antioxidant film as a mask. A method of manufacturing a semiconductor device in which a high resistance element is formed by a diffusion layer. 4. The method of manufacturing a semiconductor device according to claim 3, wherein the LOCOS oxidation step is performed by a wet oxidation step using water vapor and oxygen gas and a dry oxidation step using only oxygen gas in this order to form the LOCOS oxide film. A method of manufacturing a semiconductor device, which comprises forming the semiconductor device.