JPS5922344A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce the generation of bird beaks at both the sides of an element isolation region, and to contrive to enhance the degree of integration of ICs by a method wherein after a window is opened in an Si3N4 film formed on a semiconductor substrate, a polycrystalline silicon film buried inside of the window is etched to make the polycrystalline silicon film to survive completely inside the window or only at the circumferential part in the window thereof. CONSTITUTION:The surface of a P type silicon substrate 1 is oxidized at a high temperature to form an SiO2 film 2, and the Si3N4 film 3 of 1,000Angstrom film thickness is adhered on the upper face thereof according to the CVD method. After a window is opened in an element isolation region forming region, boron ions are implanted. Then the window part is buried completely with the polycrystalline silicon film 10. Then the polycrystalline silicon film 10 is etched according to reactive ion etching to form the sectional construction left with polycrystalline silicon 10 only in the window. When the oxidatin treatment is performed at the high temperature of 900-100 deg.C, the polycrystalline silicon film 10 inside of the window and the silicon substrate 1 positioning thereunder are oxidized to form an SiO2 film 11 to act as the element isolation rgion, and the isolation region and having extremely little generation of bird beaks is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and particularly to an improvement in a method for forming an insulating film isolation zone region made of dit' silicon silicide (Si20). .

(b) Prior Art and Problems As is well known, in a semiconductor integrated circuit (IC), a large number of elements are formed on the same semiconductor substrate, and an element isolation band region is formed to separate the elements. be done.

Previously, the PN junction isolation method was the main method used to form such a hexagonal isolation zone region, but recently, methods have been developed to reduce the parasitic capacity R4.
Insulator separation methods have come into widespread use in order to speed up operation by eliminating these problems. It is silicon nitride (Si
Mask the element region with a 3N4) film and selectively form a 5joz film region on the exposed substrate surface by high-temperature oxidation.
This is a method in which an insulating film consisting of two films is used as an element isolation band region.

A conventional method of forming an insulator isolation region using such selective oxidation and its problems will be explained. Figures 1 to 3 are sequential diagrams of the manufacturing process. First, as shown in Figure 1, a 5iQ2 film 2 of 500 thickness is formed on the surface 11ii of the Pm silicon substrate 1, and a chemical vapor phase film 2 is formed on the upper surface. A SiBN4 film 8 is deposited to a thickness of 1000 to I500 by an OVD method. Next, as shown in FIG.
'? After etching the exposed Si3N4 film 3 using carbon tetrafluoride (CF4 + freon) gas, the upper surface of the exposed Si3N4 film 3 is removed. Implantation of boron (B) ions.
This is to form a highly concentrated P+ type region under the separation zone region, and this serves as a channel stopper layer that prevents the generation of an 11 type inversion layer in the S102 film.

Next, as shown in FIG. 3, heating is performed at a high temperature of about 1000"C for a long time to form a 5102 film 5 that will become an isolation zone region. As shown in the figure, the above-mentioned P type region 6 is exposed to this high temperature heat treatment. At the same time, the image>1!

By the way, S i O211 formed in this way
The width of the isolation zone region in the fifth section has gradually become narrower as IOs have become more highly integrated, and has recently become about 1.5 to 2 μm. Then, as shown in Figure 8, a crow's beak-shaped 5iOz+1'J B
is formed around the lower part of the Si3N4 film pattern, compressing the element formation area and enlarging the element isolation zone area, which significantly impedes the degree of integration. The occurrence of this bird's beak is very closely related to the thickness of the 5i02 film 5. For example, if the width of the 5iOz film 5 is 2 μm and the film thickness is 8 μm,
0008, a bird's beak with 6000 culms and 0 width will occur on both sides, and the configuration A (5j with upper width 'lμtn) will occur.
Even if an I region is provided in O2 [5 (Q element isolation), a wide I1y region is formed with a width of 2. μm + 0.6ttntx 2 = 3.26 m. Therefore, the design should take this into consideration. d1°, which is the biggest problem for high integration of 10.

(C) Object of the Invention The present invention proposes a forming method that suppresses the above-mentioned bird's beak as much as possible.

(d) H'q formation of the invention The purpose is to selectively open a window in the S+3N4j pattern formed on a semiconductor substrate, and then temporarily attach a polycrystalline silicon film to the 1rli to bury the inside of the knee. The process of etching the polycrystalline silicon film (removing the polycrystalline silicon glands on the Si3N4 film and leaving the polycrystalline silicon film only on the entire internal surface or just one part of the periphery within the window) This can be achieved by a manufacturing method that includes the step of oxidizing the polycrystalline silicon film and the semiconductor substrate inside the window to a high +2! value to form an insulating 11A isolation zone.

(e) Practical Example 1ii [i Example] By the way, if the thin SiOz film 2 interposed between the S I 3N4 film 3 and the silicon substrate 1 is eliminated, the bird's beak will be less likely to occur, and the bird's beak will be less likely to occur. Even if it does, it will be very small. while)
If the 5LO2 film 2 is eliminated, the 1dsiaN4 film will adhere directly to the silicon substrate, which will cause problems such as contaminating the silicon substrate and applying mechanical stress to the silicon substrate.Furthermore, when removing the Si3N4 film by etching, , O
Dry etching using F4 gas damages the silicon substrate due to the low etching selectivity with the silicon substrate, and wet etching using +16 m shows that phosphorus (P) is exposed to silicon l, (11 m) on the board. death,
Problems such as contamination may occur.

Therefore, the present invention is a forming method in which the 5iOz film 2 is interposed and the occurrence of bird's beak is extremely reduced.
Explain to lll. 4 to 8 show cross sections (9) in the order of the sea bream and sushi process of one embodiment. First, as shown in FIG. 4, the surface of the P-type silicon catch plate 10 is oxidized at room temperature and
A film 2 is formed, and a film thickness of 1000~
A 5i3N41 film 3 of 1500"C is temporarily attached. Next, as shown in FIG. 5, the resist film 4 is patterned,
After etching is performed to form a window in the region where the element dividing band is carved, boron ions are implanted. The steps up to this point are the same as those of the conventional method, but then, as shown in FIG. 6, a thick polycrystalline silicon film 1O having a thickness of L to 2 μm, for example, is temporarily deposited on the north surface by CVD. When the polycrystalline silicon film 10 is temporarily attached in this manner, the window portion is also completely buried as shown in □□□.

Next, as shown in FIG. 7, the polycrystalline silicon film 10 is etched using 0.1'4 gas or by active ion etching (a type of dry etching) to leave the polycrystalline silicon film 10 only inside the window. When this reactive ion etching is performed, the polycrystalline silicon film is etched vertically, and when Sj3N4j][3 is exposed, the etching No. 14 of the etching device tI'/ is supported, so etching must be stopped at that point. Middle IJ 2, clause) 7
Ginrzan 1 with polycrystalline silicon removed only within the window shown in the figure
It can be a structure. In this case, another method is
The above-mentioned polycrystalline silicon film 1F+ is deposited in gamma red to a thickness of about 11 mm, and a resist film is applied thereon.

The resist film has a low viscosity and flows, filling all four parts and creating a smooth resist film surface. Then, by sputter etching, the resist IPj% and the polycrystalline silicon film are etched at the same time, resulting in the formation of a similar (packaging material) in which only the inside of the window is buried with the polycrystalline silicon film 10, as shown in FIG. You can also do it.

1 at 900-1100°C as shown in Figure 8.
°, if oxidized at II wetness, the polycrystalline silicon inside the window >1+'A river and the silicon below,! +(The plate 1 is completely oxidized and a 5j02 film 11 is formed as an element isolation band, and the occurrence of bird's beaks is extremely small.

Specifically, FIGS. 9 to 11 are cross-sectional views of the folded culm of other embodiments of the present invention. E il,! After patterning the same S I 3N4 PIA as in Example and implanting boron ions (see Figures 4 and 5), 11441 was formed using the OVD method as shown in Figure 9.
Deposit a polycrystalline silicon film of approximately 1,500%. Next, as shown in FIG. When the polycrystalline silicon film on the 3i3N4 film is etched and removed by reactive ion etching using OF4 gas in the same manner as in the cloth example, a thick polycrystalline silicon film is deposited on the periphery of the window in the device isolation band formation region. The polycrystalline silicon film 12 can be left only in the peripheral portion due to the force applied thereto. power)
After that, by performing high-temperature oxidation treatment, it is possible to form a 5j02 film 13 as an isolation zone with extremely few bird's beaks, as shown in FIG.

When formed in this way, the polycrystalline silicon film is oxidized to form a 5jOz film, and the 5i under the Si3N4 film 3 is
Since the O2 film 2 is not exposed, the amount of oxygen passing around is reduced, and the generation of 5C in the bird's beak is reduced.

(f) As is clear from the effect of the invention, A()^
111j has the effect of reducing the number of /(-zbeak σ) generation trees on both sides of the device isolation zone region, and significantly improving the packing density of IO.

[Brief explanation of the drawing]

Figures 1 to 3 show the conventional manufacturing process 11:i ll+
Figures 4 to 8 are according to the present invention.
i'i: -c l+) Face appearance t i++i Figures 9 through 11 are sectional views in the order of manufacturing steps of another example 1.1ii according to the present invention. In the figure, ■ is a silicon J^ board, 2 is a SIO2 film, 8 is an SI3N4 film, 4 is a resist film, 5, 11, and 13 are elements consisting of 5102 and 1111 band regions, ] (1
, 12 is a polycrystalline silicon film, 6 is a P+ type region 0 171 Fig. 1 Fig. 2 Fig. 3 Fig. 4]

Claims (1)

[Claims] After selectively opening a window in a silicon nitride film formed on a semiconductor substrate, a polycrystalline silicon film M is deposited on the upper surface thereof,
The step of burying the inside of the window, and etching the polycrystalline silicon film to remove the polycrystalline silicon film on the silicon nitride film, deposit a polycrystalline silicon film on the entire inside of the L porthole or only on the peripheral part of the window. A method for manufacturing a semiconductor device, comprising a remaining step and a step of oxidizing the polycrystalline silicon film and the semiconductor substrate inside the window to form an insulating film separation zone region.