JPS6076138A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress encroachment of a field region and to form a fine insulation isolating region by a method wherein a second insulating film is formed at overhang parts only on the peripheral edge parts of a first insulating film pattern formed on the surface of the semiconductor substrate. CONSTITUTION:An SiO2 film 2 is grown on an Si substrate 1, an Si3N4 film 3' is deposited and parts other than the programming parts for forming active regions are removed by performing an etching and channel stopper regions 15 are formed by ion-implanting boron. A thermal oxide film 16 is formed at the isolating region forming parts, the film 16 is removed by performing an etching and parts just below the peripheral edge parts of the Si3N4 film pattern 3' are respectively formed in an overhang state. A thermal oxide film 19 is formed at field forming regions 18, an Si3N4 film 20 is grown on the whole surface and a selective etching is performed, and an Si3N4 film 20' is left at the overhang lower parts only. A wet oxidation is performed and a thick field oxide film 21 is selectively grown. According to such a way, the lateral diffusion of an oxidizing agent, which is performed through the thermal oxide film 19, is suppressed, thereby enabling to lessen the bird's beak.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for manufacturing a semiconductor device.
This invention relates to improvements in isolation technology between elements in the manufacturing process of semiconductor devices such as C, LSI, and VLSI fi.

Conventional Structures and Problems Conventionally, an oxide film isolation technique called selective oxidation has been generally used as a method for isolating elements in the manufacturing process of semiconductor devices, particularly MO8LSIs.

This method will be explained step by step using a tn-channel MO8LSI as an example.

First, as shown in FIG. 1(a), silicon dioxide (
5iOz) film 2 is grown by thermal oxidation, and then a silicon nitride (Si3N4) film 3 is deposited on this SiO2 film 2. Subsequently, as shown in FIG. 4B, a photoresist film 4 is formed in the active region forming part by photolithography, and using this as a mask, the 5isNa film 3 in the active region forming part is removed by etching, and the same shape as this mask 4 is formed. 5lsN of pattern
After forming the a film 3', ions of boron, for example, are implanted to form a P+ region 6 as a channel stopper region in the field portion. Next, as shown in the same figure (0), after removing the photoresist film 4, using the 513N4 film pattern 3' as a mask, wet oxidation is carried out according to the well-known selective oxidation method, and a thick field oxide film of 6 gold is selectively grown. let P+ region 6 formed through these processes
And field oxide film 6 becomes an element isolation region. O
・Continuing, as shown in FIG. 4(d), the Si3N4 film pattern 3' and the 5102 film 2 are removed by etching to form the entire surface of the Si substrate 1 separated by the field oxide film 6, that is, the active region 7. Next, as shown in FIG. 1(e), a gate electrode 9 made of polycrystalline silicon is formed on this active region 7 via a gate oxide film 8, and further, for example, arsenic is diffused by the self-line method. Then, n+ regions 10.11f6 as sources and drains are formed. Finally, as shown in FIG. 3(f), the entire SiO2 film 12 as an interlayer insulating film is deposited by, for example, CvD, and the SiO2 film 12 covering the n+ regions 10, 11 and the gate electrode 9 is further deposited. After opening the contact hole 13, the A/wiring 16 is formed and the n-channel MO3
Fabricate elements and isolation regions.

However, the conventional method described above has various problems as shown below. FIG. 2 shows the adjacent two when the entire field oxide film 6 is formed using the 5i5N4 film pattern 3' for forming the active region shown in FIG. 1(C) as a mask.
This is a detailed depiction of the relationship between the two active regions. In general, in the selective oxidation method, the field oxide film 6 has distribution regions A and F, and in particular grows into the peripheral portion under the Si sNa film pattern 3', forming the entire F region in the figure. Are known. This is because the oxidizing agent diffuses through the thin 5i02 film 2 at the lower peripheral edge of the Si3N4 film pattern 3' during field oxidation, so the oxide film is formed in the so-called bird's beak and the field oxide film 6. It consists of a thick part E and a hollow part E in the lateral direction.

The length of the F region is such that, for example, the thickness of the Si 3 Na film pattern 3' is 1200 mm, and the thickness of the SiO 2 film 2 below it is 6 mm.
When a field oxide film 6 with a thickness of 1 μm is grown under the conditions of 0.00 people, the thickness reaches approximately 1 μm. For this reason, if the distance C between the Si sNa film patterns 3' is 2 μm, the total width distance C of the field region cannot be reduced to 4 μm or less since the F region is 1 μm, which is a major hindrance to high integration of LSI devices. . Due to this, recently 51
The thickness of the 5Na film pattern 3' is made thicker, and the SiO layer underneath is made thicker.
A method of suppressing bird's beak has been attempted in which 2 films 2'e thin<I. This is because by increasing the thickness of the S i s II 4 film, the edges of the 5 is N 4 film are bent and K becomes difficult, thereby reducing the bird's beak. Furthermore, by reducing the thickness of the 5102 film below the 5i3Na film, the cross-sectional area of the 5102 film is reduced, thereby suppressing the lateral diffusion of the oxidizing agent.

However, in the title of the song, cracks occur in the Si 3N a film at the periphery of the field oxide film, and in the latter case, stress is applied to the silicon surface mainly around the active region, causing dislocations. Ta.

OBJECTS OF THE INVENTION The present invention solves the problems seen in the above-mentioned conventional examples, and provides a method for manufacturing a semiconductor device that can suppress the digging into the field region by selective oxidation. be.

Structure of the Invention To summarize, the present invention includes a step of completely forming an oxide film and a first insulating film on the surface of a semiconductor substrate, a step of forming an opening in a predetermined region of the first insulating film and the oxide film, and the opening. a step of selectively oxidizing the conductor substrate through the opening to form a bird's beak-shaped selective oxide film, and etching and removing the selective oxide film extending over the bird's beak to form a portion below the periphery of the first insulating film opening. a step of forming an overhang-shaped opening, a step of forming a thin oxide film on the surface of the semiconductor substrate exposed in the opening, a step of forming a second insulating film covering the entire surface, and a step of forming the second insulating film with full anisotropy. etching the second insulating film only on the overhang-like portion of the lower peripheral edge of the first insulating film and removing the second insulating film in other parts; This is a method for manufacturing a semiconductor device that includes a selective thermal oxidation process that fills insulating film openings, thereby suppressing lateral diffusion of the oxidizing agent,
It makes the bird's beak smaller.

DESCRIPTION OF EMBODIMENTS The present invention will be described in detail below, taking a method of manufacturing an n-channel MO8LSI as an example.

First, as shown in FIG. 3 (2L), a 5iOz film 2 is grown by thermal oxidation on a P-type Si substrate 1 having a (100) crystal plane. Next, a 5j-3ea film 3 is deposited on this SiO2i2. Subsequently, as shown in FIG. 3 fb), a resist film 4 is formed in the intended active region by photolithography,
Using this as a mask, the Si3N4 film 3ff outside the intended active region is removed by etching. Thereafter, boron ions are implanted over the entire surface to form a channel brim region 16 in the field portion. Next, after removing the resist film 4, 5i
The thermal oxide film 16 on the surface of the Si substrate other than the active region is removed by etching, using the entire sNa film/cutan 3' as a mask. At this time, since the thermal oxide film 16 had formed a bird's beak 17, an overhang was formed immediately below the peripheral edge of the 5i5N4 film pattern 3'. Next, field forming area 1
A thin thermal oxidation film of about 100 people on the Si surface of B
9 and then psi3N4 by reduced pressure CVN method.
The film 20 is grown on the entire film surface (FIG. 2(d)). This 5is
If the Na film 20 is too thick, defects will occur in the Si substrate 1 due to stress caused by the difference in coefficient of thermal expansion between the Si3N4 film 20 and the Si substrate 1 during field selective oxidation. From this, the thickness of the 5i5N4 film 20 is 100
The thickness is preferably 0 Å or less.

Next, the second 5isNa film 2Off:
Selective etching and F3i, s as shown in Figure 3 (el)
The second 5i-3N4 film 20' is left only at the lower part of the peripheral edge of the Na film pattern 3'. membrane) (The peripheral edge of the turn 3' is in an overhanging state, so the second Si sea
The film 20 is also oat (-/) as shown in FIG. 3 (el).
In this state, if the second 5isN4 film 20 is etched by the thickness of the second 5isN4 film 20 by anisotropic etching, the 18i3N4 film 20 will be etched under the periphery of the 18i3N4 turf 3'. A second 5i5N4 film 20”
I can definitely leave 6 Next, Figure 3 (like an illusion, the first 5
13Na film pattern 3' and second 513N4 film 20
′ as a mask, wet oxidation is performed, and the first S i ′
3 Na film pattern 3' peripheral portion is the second Si s
Since the ratio of the thickness of the underlying thermal oxide film 19 to the thickness of the Na film 20' is small, lateral diffusion of the oxidant through the thermal oxide film 19 is suppressed, and the bird's beak is therefore reduced. After forming the field oxide film in this way, as shown in FIG. 3(q), the first 5isN4 film pattern 3' and the second Si5N4 film 20' are removed, and then the area where the active region is to be formed is removed. The thin thermal oxide film 2 is removed. After that, the MOS is placed in the active region separated by the field region.

A semiconductor device is manufactured by forming active elements such as bipolar. In FIG. 3, the entire process of forming the active element is omitted, but this step may be performed according to the conventional forming process.

Effects of the Invention As described above, according to the present invention, by selectively forming the second S-sN4 film on the periphery of the 15th isNa film pattern, the cod beak suppression region can be reliably formed with high precision. Since it can be formed, it greatly contributes to the manufacture of semiconductor devices with fine insulation isolation areas.

[Brief explanation of drawings]

FIGS. 1(a) to (0) are structural cross-sectional views showing the manufacturing process of an n-channel MO8LSI using a conventional selective oxidation method, and FIG. 2 is an enlarged cross-sectional view showing the substrate shape Tμ after selective oxidation in the above process. 3(a) to 3(q) are structural cross-sectional views showing a part of the manufacturing process of an n-channel MO8LSI for fully explaining one embodiment of the present invention. 1... P-type silicon substrate, 2...Si
O2 film, 3...5isNa film, 4...
Photoresist, 6°16...Channel stopper, 6.21...Field oxide film, 17.
... Over solder, 18 ... Field formation region, 19 ... SiO2 film, 20 ...
...5isNa film (second). Name of agent: Patent attorney Toshio Nakao and one other person

Claims (1)

Scope of Claims: (1) A step of forming an oxide film and a first insulating film on the surface of a semiconductor substrate, a step of forming an opening in a predetermined region of the first insulating film and the oxide film, and the opening selectively oxidizing the semiconductor substrate through etching to form a bird's beak-shaped selective oxide film, etching and removing the selective oxide film to the bird's beak portion, and forming an overhang-like shape below the periphery of the first insulating film opening. a step of forming an opening, a step of completely forming a thin oxide film on the surface of the semiconductor substrate exposed in the opening, a step of forming a second insulating film covering the entire surface, and anisotropic etching of the second insulating film. and leaving the second insulating film only in the oversolder portion of the lower peripheral edge of the first insulating film and removing the second insulating film in other parts, the opening of the first insulating film A method for manufacturing a semiconductor device that includes a selective thermal oxidation process that fills the surface with an oxide film. 2)) The method of manufacturing a semiconductor device according to claim 1, wherein the first insulating film and the second insulating film are made of silicon nitride. (3) The method according to claim 1, wherein the length of the bird's beak at the lower peripheral edge of the first insulating film is larger than the total thickness of the second insulating film and the thin oxide film at the bottom of the first insulating film. A method for manufacturing a semiconductor device. (4) The method for manufacturing a semiconductor device according to any one of claims 1, 2, and 3, wherein the second insulating film has a thickness of 1000A or less.