JPH05326691A - Method for forming element isolation region - Google Patents

Abstract

PURPOSE:To enable a narrow and high aspect ratio of element isolation region to be formed and materialize high integration by applying heat treatment to a silicon substrate, after selectively implanting oxygen ions into a silicon substrate, so as to selectively form the element isolation area in a silicon substrate. CONSTITUTION:A protective film 2 and a resist film 3 are formed in order on a silicon substrate 1, and then the place in which to form an element isolation region is patterned, and with the patterned resist film 3 as a mask, the protective film 2 is etched to form an opening. Next, oxygen ions are implanted into the silicon substrate 1, and then oxygen ions are implanted into the silicon substrate 1, and then they are heat-treated from three to four hours at about 1200-1300 deg.C in the mixed atmosphere of argon and a very small quantity of oxygen, whereby the oxygen whose ions are implanted into the silicon substrate 1 and silicon are compounded to form an silicon oxide film, thus an element isolation area 6 is formed. Lastly, the protective film 2 used as the protective film is removed lastly, whereby a semiconductor substrate where the element formation region 1a is separated by the insulating film can be gotten.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device isolation region forming method. More specifically, the present invention relates to a method for forming an element isolation region, which can form an element isolation region having a narrow width and a high aspect ratio and can achieve miniaturization of an integrated circuit.

[0002]

2. Description of the Related Art Conventionally, an element isolation region is formed so as to surround an element formation region so that electrical interference between the elements during operation is prevented and each element is completely independently controlled. Is being done. 5-9
FIG. 7 is a process explanatory view of a trench type element isolation region forming method which is currently generally performed among the element isolation techniques.

In the trench type element isolation region forming method, as shown in FIG. 5, a resist film 13 is first formed, and then an oxide film 12 on a silicon substrate 11 is patterned by etching (see FIG. 6). Then,
A trench 14 is formed in the silicon substrate 11 by anisotropic etching using the oxide film 12 as a mask (see FIG. 7).
Next, the oxide film on the surface is removed, and another oxide film is embedded in the trench by the CVD method or the like (see FIG. 8). Finally, the oxide film on the element formation region is removed (see FIG. 9).

[0004]

However, although the method of forming such a trench has an advantage that element isolation can be performed with a narrower width than LOCOS isolation, it is necessary to bury an insulator in the formed trench. In the case of an aspect ratio (a high aspect ratio in this specification means that the ratio of the width and the depth of the opening is large, that is, the cross-sectional shape of the trench is narrow and deep), and the case of the narrow width. However, there is a problem that the insulator cannot be surely buried in the trench. Therefore, there is a limit to reducing the element isolation width, which is an obstacle to miniaturization of integrated circuits.

In view of the above circumstances, it is an object of the present invention to provide a device isolation region forming method capable of forming a device isolation region having a narrow width and a high aspect ratio.

[0006]

According to the present invention, oxygen ions are selectively implanted into a silicon substrate, and then the silicon substrate is subjected to heat treatment to selectively form a silicon oxide film in the silicon substrate. It has a feature.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for forming an element isolation region of the present invention will be described below with reference to the accompanying drawings.

1 to 4 are process explanatory views of an embodiment of the element isolation region forming method of the present invention.

First, LP-CVD is performed on the silicon substrate 1.
Method, thermal oxidation method or the like to form the protective film 2 of silicon oxide, silicon nitride or the like. The thickness of this protective film 2 is
Although not particularly limited in the present invention, the thickness is preferably 70% or more of the depth of the element isolation region to be obtained from the viewpoint that oxygen ion implantation into the element formation region can be reliably prevented. A resist film 3 is further formed on the protective film 2, and a patterning of a device isolation region forming place is performed by a photolithography process (see FIG. 1).

Next, the protective film 2 is etched using the resist film 3 as a mask to form an opening 4 (see FIG. 2).

The opening 4 is an opening for implanting oxygen ions and determines the width of the element isolation region.
Apertures with a narrow width of ˜1 μm are formed.

Next, oxygen ions are implanted into the silicon substrate 1. The dose of oxygen ions is preferably 0.2 × 10 ¹⁸ cm ⁻² or more from the viewpoint of complete oxide film formation. The acceleration energy is usually 50 to 80 keV, but 500 to 10 from the viewpoint of forming a deep element isolation region.
It is preferably 00 keV. In this case, it is preferable to change the acceleration energy of ion implantation a plurality of times or steplessly so that the ion concentration is uniform in the depth direction, depending on the depth of the element isolation region to be formed. Specifically, in order to form a device isolation region having a depth of 2 μm, the dose amount is kept constant at 1 × 10 ¹⁸ cm ⁻² and the acceleration energy is 9
When ion implantation is performed while changing the pressure to 00 keV, 400 keV, and 100 keV, a substantially uniform oxygen ion implantation region is formed with a depth of 2 μm.

That is, the implantation of oxygen ions into the silicon substrate 1 is 2 when the acceleration energy is 900 keV.
It is distributed like a normal distribution at the deepest concentration at the depth of μm,
When the acceleration energy is 400 keV, the distribution is centered on a depth of about 1 μm, and when the acceleration energy is 100 keV, the distribution is centered on a depth of about 0.2 μm. Therefore, in order to form a device isolation region having a depth of about 2 μm, it is necessary to implant oxygen ions within this depth to oxidize, and as described above, it is necessary to implant ions by changing the acceleration energy. ..
From the point of changing the depth of ion implantation, it is preferable to change the acceleration energy continuously rather than stepwise, and in this case, for example, 50 to 9
By continuously changing 00 keV and repeating it about twice, an oxygen ion implantation region having a narrow depth of 2 μm is formed.

During the ion implantation, the substrate temperature may be raised so that the ions can easily enter the substrate. In this case, the substrate temperature is 500 to 600 ° C.
A degree is preferable.

Next, heat treatment is performed at 1200 to 1300 ° C. for 3 to 4 hours in a mixed atmosphere of argon and a slight amount of oxygen, whereby the oxygen ion-implanted in the silicon substrate 1 and the silicon are combined to form silicon oxide. The film is formed and the element isolation region 6 is formed. Finally, the protective film 2 on the surface of the substrate used as the mask is removed to obtain a semiconductor substrate in which the element formation region 1a is separated by an insulating film.

In the above-mentioned embodiment, the ion implantation of oxygen ions is explained with an example of a dose amount of 1 × 10 ¹⁸ cm ^-2 . However, the oxygen ions are for forming silicon oxide, and are of high quality. In order to improve the insulating property of the film, the dose amount is preferably 0.2 × 10 ¹⁸ cm ^-2 or more.
That is, if the dose amount is smaller than this, a perfect oxide film cannot be obtained, and the insulation characteristics deteriorate. Further, in order to obtain better insulating properties, the dose amount is more preferably 1 × 10 ¹⁸ cm ^-2 or more.

The protective film 2 is a film for preventing oxygen ions from being implanted into the element forming region 1a during implantation of oxygen ions, and completely implants oxygen ions into the element forming region 1a. It must be prevented and a sufficient thickness is required. However, since the implantation depth of oxygen ions into the silicon oxide film or the silicon nitride film is about 1/2 of the implantation depth into the silicon substrate, the thickness of 70% or more of the depth of the element isolation region to be formed. It is sufficient if the protective film is formed.
In addition to the silicon oxide film and the silicon nitride film, a resist film may be used, but in this case, the resist film is easily deformed due to the temperature rise during ion implantation, and moreover, the resist film is easily broken by ion bombardment. It is difficult to form the element isolation region.

[0018]

As described above, in the element isolation region forming method of the present invention, oxygen ions are implanted into the silicon substrate using the protective film as a mask, and then the silicon substrate is heat-treated to form the element isolation region. Therefore, it is possible to form an element isolation region having a narrow width and a high aspect ratio, and thereby miniaturization of the integrated circuit can be achieved.

[Brief description of drawings]

FIG. 1 is a process explanatory view of an example of a method for forming an element isolation formation region of the present invention.

FIG. 2 is a process explanatory view of an example of an element isolation formation region forming method of the present invention.

FIG. 3 is a process explanatory view of an example of the element isolation formation region forming method of the present invention.

FIG. 4 is a process explanatory view of an example of the element isolation formation region forming method of the present invention.

FIG. 5 is a process explanatory view of a conventional trench type element isolation region forming method.

FIG. 6 is a process explanatory view of a conventional trench type element isolation region forming method.

FIG. 7 is a process explanatory view of a conventional trench type element isolation region forming method.

FIG. 8 is a process explanatory view of a conventional trench type element isolation region forming method.

FIG. 9 is a process explanatory view of a conventional trench type element isolation region forming method.

[Explanation of symbols]

 1 Silicon substrate 2 Protective film 3 Resist film 6 Element isolation region

Claims (4)

[Claims] 1. A method for forming an element isolation region, which comprises selectively implanting oxygen ions into a silicon substrate and then subjecting the silicon substrate to a heat treatment to selectively form an element isolation region in the silicon substrate. .. 2. When selectively implanting oxygen ions,
2. The method for forming an element isolation region according to claim 1, wherein a protective film made of a silicon oxide film or a silicon nitride film is used as a mask, and the film thickness is 70% or more of the length of the element isolation region in the direction perpendicular to the substrate. .. 3. The method for forming an element isolation region according to claim 1, wherein the acceleration energy during oxygen ion implantation is changed a plurality of times or continuously. 4. A dose amount of oxygen ions is 0.2 × 10 ^18.
The method for forming an element isolation region according to claim 1, wherein the element isolation region is at least cm ^-2 .