JPS61276341A - Forming method for element separating region - Google Patents

Abstract

PURPOSE:To form a separating layer by selectively perforating a polysilicon formed on an Si substrate by an anodic oxidation method in a porous state, and forming an oxide film. CONSTITUTION:Polysilicon 2 and Si2N4 film 3 are superposed on a P-type Si film 1, a resist mask 4 is coated, the film 3 is opened, and <11>B<+> ions are implanted. The resist 4 is removed, the B is thermally diffused, subjected to an anodic oxidation in HF of 40-50% to alter to a porous Si 5. Then, it is altered to an SiO2 film 6 by heat treating at approx. 1,000 deg.C in O2. The expansion of the porous Si 5 after oxidation is almost zero, and there is not step difference on the surface after the film 3 is removed. Then, a laser beam is emitted to the polysilicon 2, or the polysilicon 2 is heated to 1,100-1,200 deg.C by a linear heat source, and recrystallized to form a single crystal region 10. According to the construction, an element separation of a wide region can be readily performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for forming an element isolation region that allows easy isolation of a wide area when manufacturing element isolation in a semiconductor device.

(Prior Art) Conventionally, isolation between semiconductor elements in a semiconductor device has been achieved using a method (LOCO8) of selectively growing an oxide film (810).
@ or l5OPLANAR method), dig a groove and oxidize M
This is done by embedding a (SiOs) or polycrystalline silicon.

Recently, as shown in FIG. 2, a separation method using selective epitaxial growth technology has also been proposed.

FIGS. 2(a) to 2(e) show an example of an element isolation formation process using selective epitaxial growth. First, as shown in FIG. 2(a), a (100) Si substrate is grown. 1, a thermal oxide film 2 of 0.15 to 2 .mu.m is grown and etched to form an element isolation pattern having vertical sidewalls.

Next, as shown in FIG. 2(b), polycrystalline silicon (or 5isN4) 3 with a thickness of about 0.1 μm is deposited, and polycrystalline silicon (or 5isN4) 3 is deposited on the sidewall of the thermal oxide film 2 using a directional etching technique. Sil N<) 3 should be left.

Finally, as shown in FIG. 2(e), the surrounding thermal oxide film 2
By selectively growing the epitaxial film 4 on the exposed substrate Sil until it becomes flat, a structure in which the elements are separated can be obtained.

In this structure, the dimensions of the isolation region are determined by the thickness of the thermal oxide film 2 and the phosphorography process.

Therefore, there is no reduction in device dimensions during the process as seen in the LOCO8 method and the 15OPLANAR method, and a high aspect ratio can be obtained.

(Problem to be Solved by the Invention) However, when the area of the thermal oxide film 2 with respect to the wafer increases, nucls are formed on the thermal oxide film 2 during epitaxial growth.
There were problems such as nucleation (nucleation) becoming more likely to occur and selectivity deteriorating, and the crystallinity of the epitaxial Si film 4 near the sidewalls of the thermal edge film 2 becoming worse.

As described above, in the conventional device isolation formation method, an increase in the area of the thermal oxide film (that is, an increase in the isolation area) degrades the isolation characteristics, which poses a problem that imposes restrictions on the isolation pattern when designing semiconductor devices. Due to its poor crystallinity, there is a problem in that it adversely affects the electrical characteristics of semiconductor devices.

This invention provides a method for forming an element isolation region that solves the problems of the prior art mentioned above, such as restrictions on isolation patterns and adverse effects on the electrical characteristics of semiconductor elements. .

(Means for Solving the Problems) In a method for forming an element isolation region, the present invention selectively makes polycrystalline Si formed on a semiconductor substrate porous by an anodization method and converts it into an oxide film to form an isolation region. This method introduces a process to form a .

(Function) According to the present invention, since the above-described steps are introduced into the method for forming an element isolation region, the polycrystalline SL in the region to be isolated on the semiconductor substrate is selectively made porous by anodization. Heat treatment is performed in an oxygen atmosphere to form an oxide film and to form an isolation region.

(Example) Hereinafter, an example of the method for forming an element isolation region of the present invention will be described based on the drawings.

FIGS. 1(a) to 1(f) are process explanatory diagrams of an embodiment of the present invention, and will be explained in order.

In this Fig. 1(a) to Fig. 1(f), Fig. 2(a)
) to FIG. 2(c) will be described with the same reference numerals assigned to the same parts.

First, as shown in FIG. 1(a), a P-type Si substrate (10
0) Polycrystalline Si 2 is deposited to a thickness of 0.5 μm to 2.0 μm on 1, and then a nitride film (hereinafter referred to as 5iaN+ film) 3 is deposited on 0.5 μm to 2.0 μm.
Grows 1 μm.

Next, as shown in FIG. 1(b), the area O8 to be separated is
i. The N4 film 3 is removed by a known photolithography and etching technique. After removing the SL and N4 films 3, B (poron) was applied by ion implantation using the Si3N, film 3, and resist film 4 as masks at approximately 1X10" to IX1015.
Enter 2.

Next, as shown in FIG. 1(c), the resist film 4 is removed and B (, trron) is diffused by heat treatment.

Next, the polycrystalline Si in the region to be separated to which B has been added is made into porous Si 5 as shown in Fig. 1(d) by anodizing in 40 to 50% HF (hydrofluoric acid). .

After that, the porous region' was heated to 900°C to 1000°C.
A heat treatment is performed in an oxygen atmosphere at a temperature of 100 to form an oxide film 6 as shown in FIG. 1(e). Since there is almost no deposition expansion of the porous Si5 after oxidation, there is no step difference in the optical surface after the removal of Si, N, and film 3, and the surface is almost flat.

In addition, during oxidation, SL, N, and polycrystalline Si2 directly under the film 3 are
Since it is protected by the 3i3N4 film 3, it will not be oxidized.

Next, 20 to 1
Heating and recrystallization are performed by scanning a laser beam or electron beam narrowly focused to about 00 μm at a speed of 10 to 50 inches/see, or by scanning a linear heating source such as a carbon heater at a scanning speed of several milliliters +/-. , the substrate temperature is 1100 ~
Single crystal region 1 to be recrystallized at 1200℃
0 is obtained.

At this time, polycrystalline S on PffiSi substrate (Zoo) 1
Since i2 is recrystallized, this recrystallized Si (single crystal Si) has good crystallinity with a (100) orientation.

By forming a MOSFET or bipolar element in a separated and single crystallized region! 5. It becomes possible to create MOS type or bipolar type integrated circuits.

(Effects of the Invention) As described in detail above, according to the present invention, regions of polycrystalline Si on a semiconductor substrate to be separated are selectively made porous by anodization, and heat treatment is performed to form an oxide film. Since the separation area is formed in a different manner, the area to be separated is not limited, and by making it porous, it is possible to easily separate a wide area.

Furthermore, since polycrystalline Si on single-crystal Si is recrystallized, stable orientation and good crystallinity can be obtained.

Therefore, when a MOSFET or bipolar transistor is formed in this region, leakage current is small and
It is expected that stable characteristics will be obtained.

[Brief explanation of drawings]

1(a) to 1(f) are process explanatory diagrams of an embodiment of the method for forming an element isolation region of the present invention, and FIG. 2(a)
2C to 2C are process explanatory diagrams of a conventional element isolation forming method. 1... P-type Si substrate, 2... Polycrystalline Si. 3...
513N4 film, 4... Resist film, 5... Porous S
i, 6...Oxide film, 10...Single crystal region. Fig. 1 10 To the top of the boiling fin and roaring territory 2-4 80 elements + 9 i^ Tadahiro pt some sweat〃 Shigekata Jio's energy l friend Akira Fig. 1 (a) (b) (C) Buried

Claims (1)

[Claims] (a) A step of depositing polycrystalline Si on a semiconductor substrate;
b) A step of selectively converting this polycrystalline Si into porous Si using an anodization method; (c) A step of oxidizing this porous Si; (d) A step of converting the remaining polycrystalline Si into single-crystal Si. A method for forming an isolation region, characterized by comprising the following steps.