JPS6155939A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To realize the miniaturization of elements and to effect the isolation of elements of high reproductivity by an easy process by using the photoresist film capable of reliquefaction as one left in the recesses after forming an insulating film on a semiconductor substrate. CONSTITUTION:Grooves are formed in a field region of a semiconductor substrate 1 and B<+> ions are implanted to form a P layer 8. Nextly, a field insulating film 10 is deposited on the substrate 1 and a resist film 9 is formed in a part of the field region. Then the film 9 is fused again and is solidified and the films 10 and 9 are etched uniformly. Consequently, even if the elements are miniaturized, the field insulating film is levelled with good controllability and the good element isolation characteristics can be obtained. Also, the demand for the accuracy in mask alignment during a photolithography process is alleviated and the facile mask alignment of low cost becomes possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a MOa type semiconductor device that allows fine element isolation.

[Technical background of the invention and its problems]

2. Description of the Related Art Conventionally, semiconductor devices and integrated circuit devices have been becoming smaller in size due to improved device characteristics and higher integration. Element isolation technology is required to electrically insulate and separate the huge number of devices on each chip from each other. An important requirement for device isolation technology is to minimize the area required for isolation so that the chip area can be effectively dedicated to active devices. Furthermore, considering that wiring will be applied after separation, it is better to have no steep steps.

From the various viewpoints mentioned above, the selective oxidation method using a silicon dioxide film, which is the mainstream of conventional device isolation technology, has the disadvantage that the isolation region invades the device region in a bird's beak shape, reducing the effective area of the device region. ．． 1. Several new element isolation methods have been proposed. 0 An example of this is a method of element isolation using a buried oxide film, which will be explained with reference to FIG.

A P-type silicon substrate (1) with a (100) plane orientation is used. A groove having side faces (2) with a (111) plane direction is formed in an element isolation region using an alcohol solution of potassium dihydroxide. After this, OVD method (Ochemical Vapor Depos
tion) Deposit a K silicon dioxide film (3) (FIG. 2(a)). Next, the photoresist (4) is left by photolithography, and then a photoresist (5) with low viscosity is applied (Figure 2 (b)). - Etch the entire surface using an etching method to flatten it (Figure 2 (C)). However,
In reality, the resist (4) is made using a photolithographic method, so if the mask alignment is incomplete, as shown in FIG. The field film (
3) is not flat (Fig. 3 Q))). After this, the field film (3) is generally exposed to a hydrofluoric acid etching solution several times, and thinning of the film is unavoidable.

If the field film becomes thin, sufficient insulation effect from indirect elements cannot be obtained. As mentioned above, it is undesirable to increase the area of the lock and field regions to ensure insulation from the viewpoint of high integration.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device that solves the above-mentioned problems, achieves miniaturization of devices, and performs device separation with easy steps and high reproducibility.

[Summary of the invention]

The gist of the present invention is that after an insulating film is formed on a semiconductor substrate, a photoresist film left in the recesses is made of a material that can be liquefied again, thereby achieving high flatness despite rough mask alignment accuracy. Realizing an element isolation structure [6. For example, the remaining resist film is exposed to high temperature and liquefied, buried flat in the depression of the insulating film by gravity and surface tension, and then cured by, for example, UV irradiation.
This can be achieved by uniformly etching using reactive ion etching.

〔Effect of the invention〕

According to the present invention, even when the device is miniaturized, the field insulating film can be flattened with good controllability and good device isolation characteristics can be achieved. In addition, the requirements for mask alignment accuracy in the photolithography process are relaxed, and mask alignment becomes possible at low cost and easy.

[Embodiments of the invention]

A specific embodiment of the present invention will be described below with reference to FIG. First, plane orientation (100), specific resistance 5~10Ω-
Etching resistant i on scratched P-type silicon single crystal substrate (6)
For example, a silicon dioxide film (7) of 4000A is formed as a mask and an ion implantation-resistant mask1, and a trench of about 8 μm is formed in the field region vcO by reactive ion etching, leaving this film only in the element region. Form. followed by B+
ion at 50Kev, I x 10'"an-"
ion implantation to become a channel stopper (Pit8)
(Fig. 1(a)). Next, after removing the oxide film, a silicon dioxide film a0 is deposited on the entire surface of the substrate by the OVD method to a groove depth of 0.8 μm or thicker. After this,
A photoresist film (9), which has the property of becoming liquid at high temperatures and hardening with ultraviolet light, is selectively formed in the recesses on the surface of the oxide film C11 by photolithography. This photo flattens the concave part.
In order to embed with resist, 7 oto resist film (9)
It is important to control the volume etc.

In reality, the photoresist (9) should be made as thick as 1.5 or 1.8 μm to form it in a relatively narrow area of the recess, and the alignment error in mask alignment can be minimized. (Figure 1(b)).

Thereafter, the processed surface of the substrate is turned upward and left at 130'O for 15 minutes to liquefy the photoresist (9). Next, this is cooled to room temperature and cured with an ultraviolet lamp (Figure 1 (C)).
). After smoothing the surface as described above, the entire surface is etched by reactive ion etching using Freon gas. The etching conditions at this time are set so that the etching speed of the silicon dioxide film <1 (I and the photoresist film (9) is the same, or the silicon dioxide film (11) is about twice as fast as the etching rate of the photoresist film (9).

As a result, in the field region, the resist film (9) acts as a stopper against etching, and etches until the substrate surface in the element formation region is exposed, leaving unnecessary resist ff! Upon removal, the silicon dioxide film Uω is flat and completely embedded in the field region (as shown in FIG. 1).

The element isolation structure formed in this manner has good insulation from adjacent elements and is easier to miniaturize than conventional methods.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the manufacturing process of one embodiment of the present invention, and FIG. 2 is a cross-sectional view showing the manufacturing process of an embodiment of the present invention.
FIG. 3 is a diagram showing an example of the manufacturing process of a 1MO8 type semiconductor device, and is a yi plane view showing an example where mask alignment is incomplete. 1... P-type silicon substrate, 2... Base desk side, 3...
・Silicon dioxide film (OVD method), 4...Resist film, 5.
・Low viscosity resist film, 6...P-type silicon substrate,
7...Silicon dioxide film (thermal oxidation), 8...P+ layer (B
+ion implantation), 9...resist film, lO...silicon dioxide film C0VD method). (7317) Representative Patent Attorney Noriyuki Chika (and 1 others)
name)-Q Figure 2 Figure 3

Claims (3)

[Claims] (1) A step of forming a groove in the field region of a semiconductor substrate, a step of depositing a field insulating film on the substrate, a step of forming a resist film in a part of the field region, and remelting and solidification of this resist film. 1. A method of manufacturing a semiconductor device, comprising: a step of uniformly etching an insulating film and a resist film. (2) A method of manufacturing a semiconductor device according to claim 1, characterized in that single crystal silicon is used as the semiconductor substrate and a silicon dioxide film is used as the field insulating film. (3) A method of manufacturing a semiconductor device according to claim 1, characterized in that a groove having an inclination is formed in a field region of a semiconductor substrate.