JPH01179431A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form an element isolating region in the dimension as designed thereby avoiding the disconnection of wiring etc., by a method wherein, after implanting oxygen ion, an element isolating oxide film is formed in a semiconductor substrate. CONSTITUTION:After forming a surface protective film 12 on the main surface of a semiconductor substrate 11, the first masking material 13 is formed on the protective film 12. The second masking material 14 is formed on the first masking material 13 and then both of the masking materials 13, 14 are selectively removed by anisotropical etching process. The substrate 11 is implanted with oxygen ion using the third masking material 16 as a mask only on the sidewall parts of the pattern comprising the masking materials 13, 14. The masking materials 14, 16 are removed and after converting the oxygen ion implanted region into an oxide film 18 by annealing process, the masking material 13 and the protective film 12 are removed. Through these procedures, an element isolating region in narrow width can be formed in the dimension as designed to avoid the disconnection of wiring etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a semiconductor device, and particularly to a technique for separating semiconductor elements formed on a semiconductor substrate.

(Prior Art) Conventionally, the ocos method is widely known as an element isolation technique. In this method, as shown in FIG. 2, an oxidation-resistant film, for example, a silicon nitride film 23, is formed on a semiconductor substrate 21 via an insulating layer 122 and patterned, and then the silicon nitride 1123 is selectively oxidized. The element isolation oxide film 24 is formed by performing selective oxidation as a mask material.

By the way, in the above-mentioned LOCO8 method, due to the horizontal growth phenomenon of the element isolation oxide film 24 called bird's beak, the pattern dimension of the selective oxidation mask material (silicon nitride M23) and the dimension of the formed element isolation oxide film 24 are changed. A dimensional error E (represented by E-E1+E2 in FIG. 2) occurs between the two. For example, set the film thickness of insulation M22 to 1500
The film thickness of the silicon nitride film 23 is 2,500 people, and the oxidation I for element isolation during selective oxidation! The thickness of I24 is 8,000 mm, and the thickness of the completed element isolation oxide film 24 is 5,000 to 60 mm.
If there are 00 people, the above-mentioned dimensional error E will be 1.2 to 1.6 tan. Therefore, the practical dimension of the element isolation oxide film 24 is about 2-2, and there is a problem that it is not suitable for forming a narrower element isolation region. Furthermore, since about half of the thickness of the element isolation oxide film 24 formed by the above-mentioned OCOS method is formed with a convex step above the main surface of the semiconductor substrate 21, it is difficult to pass wiring through the upper layer. This problem becomes particularly noticeable when high integration is achieved by forming fine element isolation regions.

(Problems to be Solved by the Invention) As described above, in the conventional semiconductor device manufacturing method, the element isolation oxide film has dimensional errors due to bird's beaks, making it difficult to form a narrow element isolation region, and Since it is formed with a convex step above the substrate, it has the disadvantage that when it is miniaturized, disconnection of wiring becomes noticeable.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for manufacturing a semiconductor device that can be formed with designed dimensions and that can form a flat element isolation oxide film with no step difference from the active region.

[Structure of the Invention] (Means and Effects for Solving the Problems) That is, in the present invention, in order to achieve the above-mentioned object of the invention, after forming a surface adhesive on the main surface of a semiconductor substrate, the above-mentioned Surface protection 5t#! forming a first mask material on top, forming a second mask material on the first mask material, and selectively removing the first and second mask materials using an anisotropic etching method; do. After that, a third mask material is formed only on the side wall portion of the pattern made of the first and second mask materials,
Oxygen ions are implanted into the semiconductor substrate using the first, second, and third mask materials as masks. And the above second and third
The method is characterized in that the first mask material and the surface protection film are removed after the first mask material is removed, and then annealing is performed to convert the oxygen ion implantation region into an oxide film.

Further, after ion-implanting oxygen into the semiconductor substrate, the first
, the second and third mask materials may be removed, and then annealing may be performed to convert the oxygen ion implantation region into an oxide film and the surface protective film may be removed.

According to this manufacturing method, after oxygen ion implantation, annealing is performed to form an oxide film for element isolation in the semiconductor substrate. Therefore, a narrow element isolation region can be formed with the designed dimensions, and there is no need to worry about wiring breakage. Furthermore, by controlling the width of the third mask material (represented by h in FIG. 1C), it is possible to form an oxide film for element isolation that is narrower than the limit of lithography.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIGS. 1(a) to 1(e) show manufacturing steps for explaining the method for manufacturing a semiconductor device of the present invention. First, as shown in FIG. 1A, a silicon oxide film (surface protection film) 12 having a thickness of about 1000 is formed on one and seven surfaces of a silicon substrate 11 by thermal oxidation. Subsequently, a polycrystalline silicon layer (first mask material) 1 is formed on the silicon oxide film.
A silicon oxide layer 11 (second mask material) 14 is deposited to a thickness of about 4000 layers. Next, as shown in FIG. 3B, a resist pattern 15 is formed using the PEP method, and the polycrystalline silicon layer 13 and silicon oxide film 14 are selectively removed by anisotropic etching. Thereafter, as shown in FIG.
When etched back by the IE method, the side walls of the polycrystalline silicon layer 13 and silicon oxide film 14 have a width of 500 mm.
Approximately 0 silicon oxide films (third mask material) 16 remain. Next, using the polycrystalline silicon layer 13, silicon oxide film 14, and silicon oxide 116 as masks, oxygen is dosed by ion implantation ff11018c.
Ion implantation is performed to approximately m4.

Next, as shown in the figure (d), the silicon oxide film 14 and the silicon oxide film 11i16 are removed, and
The oxygen ion-implanted ffi region 17 in the semiconductor substrate 11 is converted into an element isolation oxide film 18 by annealing in a gas atmosphere for 7 hours.

Finally, as shown in the figure (e), a polycrystalline silicon layer 13,
Then, the silicon oxide film 12 is removed to complete the element isolation region.

According to this manufacturing method, an oxide film for element isolation is formed by injecting oxygen ions into the semiconductor substrate and performing annealing, so there is no step difference with the active region.
Furthermore, it is possible to obtain a device isolation region as designed.

For example, assuming that the element isolation region does not expand during the annealing process, the dimensions of the element isolation oxide film are, in principle, "Ion implantation width into the semiconductor substrate + Lateral dispersion width J during ion implantation". Here, the width of ion implantation into the semiconductor substrate is set as rA-hX2J from the PEP width (represented by A in FIG. 1(b)) and the width (h) of the silicon oxide film on the side wall. Therefore, it is also possible to form an oxide film for element isolation that is smaller than the limit of lithography.

In the figure (d), the mask material to be removed is the silicon oxide film 14 and the silicon oxide film I! ! 1G, but in addition, the polycrystalline silicon layer 14 may also be removed, and only the silicon oxide film 12 may be removed after annealing. Further, although a silicon oxide film is used as the third mask material in the above embodiment, the third mask material is not limited thereto, and a silicon nitride film may also be used. Furthermore, although a polycrystalline silicon layer is used as the first mask material, a silicon nitride film may also be used.

[Effects of the Invention] As described above, the present invention provides a method for manufacturing a semiconductor device that can be formed with designed dimensions and that can form a flat element isolation oxide film with no step difference from the active region. can.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining a method of manufacturing a semiconductor device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view for explaining a conventional method of manufacturing a semiconductor device. 11...Silicon substrate, 12...Silicon oxide film (
surface protective film), 13... polycrystalline silicon layer (first mask material), 14... silicon oxide film (second mask material), 15... resist pattern, 16... silicon oxide film (Third mask material), 17... Ion implantation region, 18... Oxide film for element isolation. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (2)

[Claims] (1) A first step of forming a surface protective film on the main surface of a semiconductor substrate, a second step of forming a first mask material on the surface protective film, and a second step of forming a first mask material on the first mask material. a third step of forming a second mask material; and a fourth step of selectively removing the first and second mask materials using an anisotropic etching method.
a fifth step of forming a third mask material only on the sidewalls of the pattern formed in the fourth step; and a step of forming a semiconductor substrate using the first, second, and third mask materials as masks. a sixth step of ion-implanting oxygen into the area; a seventh step of removing the second and third mask materials; and an eighth step of converting the oxygen ion-implanted region into an oxide film by annealing. and a ninth step of removing the first mask material and the surface protective film. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the first mask material is further removed in the seventh step, and the surface protection film is removed in the ninth step.