JPS62232143A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress the generation of crystal defects due to field-oxide-film forming process, by depositing a polycrystalline silicon film on the entire surface of a substrate, on which an oxidation resisting mask is formed in an element forming region, and performing anisotropic etching of the polycrystalline silicon film so that said film remains on the side wall of the oxidation resisting mask. CONSTITUTION:On a P-type silicon substrate 11, an Si3N4 film 13, which is to become an oxidation resisting mask, is deposited and formed through a thermal oxide film 12. Then, the Si3N4 film 13 is selectively etched away. A polycrystalline silicon film 14 is deposited and formed on the entire surface of the substrate. At this time, the thermal oxide film 12 is made to present between the polycrystalline silicon film 14 in a field region and the substrate 11 without fail. Then, the entire surface of the polycrystalline silicon film 14 is etched so that the film 14 remains only on the side wall part of the Si3N4 film 13. Then, a P<+> type layer 15 for preventing inversion is formed. Thereafter, the polycrystalline silicon film 14 and the substrate 11 are oxidized. A thick field oxide film 16 is formed. Then, the Si3N4 film 13 in the element forming region and the thermal oxide film 12 are etched away, and the surface of the substrate 11 is exposed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a method of manufacturing a semiconductor 11, and in particular, a method of forming a field region that reduces dimensional errors in an element region of a high-density integrated circuit. Regarding.

(Prior Art) In conventional semiconductor devices, especially MO8 type integrated circuit devices, a selective oxidation method (<LOCO8 method) is generally used as a method for forming a thick insulating film in an isolation region (field oxide film) between elements. . In this method, silicon nitride Ml (S i3
After forming N4 II) and implanting ions into the field region to prevent inversion, a thick field oxide film is formed by performing thermal oxidation at high temperature and for a long time in an oxidizing atmosphere. However, in this method, when forming the field oxide film, oxidation also progresses in the lateral direction, so the Si3N
A phenomenon in which the thick field oxide film digs into the edge of +111 in the shape of a bird's beak can be seen. This causes a dimensional error in the element formation region, which hinders high integration, especially in high-density integrated circuits, and causes deterioration of characteristics of micro IO elements.

As a method for forming a field oxide film to solve such problems, the method shown in FIGS. 2(a) to 2(d) has been proposed. First, as shown in (a), 5i0 is applied to the silicon substrate 21.
The Si3N4 film 23 is formed with a jfi oxide film through the two films 22 and patterned to form an oxidation-resistant mask. Then, using the SiO2 film 22 and Si3N41123 as a mask, for example, a reactive ion etching method (RIE method) is performed.
The substrate 21 is selectively etched by about 2,000 people to form a wafer 24. After this, the entire surface of the board was coated with CVD to a thickness of 700 APi! A layer of polycrystalline silicon 25 is deposited. Next, the entire surface of the polycrystalline silicon film 25 is etched using, for example, the RIE method as an anisotropic etching method (b
), the polycrystalline silicon film 25 is left only on the sidewalls of the Si3N+ffQ23. Then, boron ions are implanted to form the anti-inversion groove 26. After this, the deposited polycrystalline silicon film 25 and substrate 21 are simultaneously thermally oxidized at 100°C for 4 hours in an atmosphere containing water vapor, and as shown in FIG. form.

Then, as shown in (d), S ix N in the element formation region
4 WA23 and oxidation! 122 is removed to expose the substrate surface.

According to this method, there is a polycrystalline silicon film on the side wall of the mask when the field oxide film is formed, and this is oxidized at the same time, so that encroachment of the field oxide film under the mask is effectively prevented.

However, in this method, since the field fRR is formed in advance, a large stress is applied to a part of the corner of the groove 24 during the high-temperature, long-time thermal oxidation process. As a result, as shown in FIG. 2 (d), crystal defects 28 enter the substrate in the element formation region from around the field m region, which impairs the device characteristics. A polycrystalline silicon layer 25 is deposited on this surface with its surface exposed, and as shown in FIG.
It is etched away leaving it on the side wall of 3N411!23. Therefore, the surface of the substrate 21 is exposed to the RIE etching atmosphere, causing damage and contamination by ions. These also cause crystal defects in the substrate in a subsequent high-temperature process, resulting in a decrease in device reliability and yield.

(Problems to be Solved by the Invention) As described above, in the conventional field oxide film forming method, crystal defects occur in the element region from the edge of the field WA, especially when fine elements are integrated at high density. There was a problem that the characteristics deteriorated.

An object of the present invention is to provide a method for manufacturing a semiconductor IN that solves the above problems.

[Structure of the Invention] (Means for Solving the Problems) The method of the present invention involves depositing a polycrystalline silicon pattern over the entire surface of a semiconductor substrate with an oxidation-resistant mask formed in the element formation region, and depositing this polycrystalline silicon film. is etched by anisotropic etching and left on the oxidation-resistant mask sidewall. Here, the method of the present invention differs from the conventional method in that, firstly, no grooves are formed on the substrate surface in the field region surrounded by the oxidation-resistant film, which causes stress, and secondly, the method is different from the conventional method in that Polycrystalline silicon is deposited with a thermally oxidized film formed so that the surface of the substrate is not exposed during the etching process. Thereafter, as in the conventional method, a field oxide film is formed by thermally oxidizing the substrate surface at the same time as polycrystalline silicon oxidation.

(Function) According to the method of the present invention, since grooves are not formed in the field region, the generation of crystal defects during a high-temperature, long-time thermal process is suppressed. Furthermore, since a thermal oxide film is interposed under the polycrystalline silicon film, this polycrystalline silicon film can be
When etching is performed using the E method, the substrate surface is not exposed to the RIE atmosphere, and ion damage and contamination are prevented. This also suppresses the occurrence of crystal defects. Therefore, according to the present invention, it is possible to integrate fine elements at a high density without deteriorating the element characteristics.

(Example) The present invention will be explained in detail below.

FIGS. 1(a) to 1(f) show the process of forming a field oxide film in one embodiment. As shown in <a), the surface orientation (100
), 5iiN+1113 is formed by CVD as an oxidation-resistant mask through thermal oxidation [112] on a p-type silicon substrate 11 with a specific resistance of 5 to 50 Ω·1. thermal oxidation 1
For example, 112 is 600 people, Si3N<[! 113 has a board of about 1,000 people, for example.

Thereafter, as shown in (b), the 51 g N41113 on the field area is selectively etched away using a conventional photolithography method, for example, by RIE.

Then, as shown in (C), about 700 polycrystalline silicon films 14 are deposited over the entire surface of the substrate by the CVD method. At this time, the polycrystalline silicon film 14 in the field region and the substrate 11
Thermal oxidation Wj112 is ensured to exist between the two. If the thermal oxide film 12 is etched away at the same time in the Si3N+IIl etching step of (b), or if it becomes thin, thermal oxidation is performed again so that at least 400 substrate thermal oxide films are present. Make it.

Next, the entire surface of the polycrystalline silicon layer 14 is etched by an anisotropic etching method, for example, the RIE method, so that it remains only on the side walls of the Si3N4 film 13, as shown in FIG. At this time, since the substrate surface is covered with the thermal oxide film 12, the substrate surface will not be damaged or contaminated by polycrystalline silicon film etching. Next, boron ions are implanted to form a p+ type layer 15 for preventing inversion. Thereafter, the polycrystalline silicon 114 and the substrate 11 are oxidized in an oxidizing atmosphere containing water vapor to form a thick field oxide film 16 as shown in FIG. and(
As shown in f), 5i3N41111 in the element formation region
3 and thermal oxidation 1112 are removed by etching to remove the substrate 11.
expose the surface. Following the well-known process, for example, MO
Elements such as S transistors are formed.

According to this embodiment, unlike the conventional method, a groove is not formed in the field region, so that crystal defects due to stress at a part of the corner of the groove are prevented from occurring in a later thermal process. Further, the substrate surface is not damaged by ions or contaminated during the polycrystalline silicon film etching process. Therefore, deterioration of device characteristics can be effectively prevented. Also,
Field oxidation is performed while leaving a polycrystalline silicon film on the mask sidewalls, and since polycrystalline silicon has a faster oxidation rate than single crystal silicon, a thick field oxide film can be obtained in a relatively short heat process.

Of course, the action of the polycrystalline silicon film prevents the field oxide film from penetrating into the device region in a bird's beak shape, and dimensional errors in the device region can be kept small. Furthermore, since the ion implantation to prevent field reversal is performed with the polycrystalline silicon film left on the sidewalls of the mask, the anti-reversal layer is prevented from spreading into the device area during the subsequent thermal process and affecting device characteristics. be done.

Note that the present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications without departing from the spirit thereof.

[Effects of the Invention] As described above, according to the present invention, the occurrence of crystal defects caused by the field oxide film forming process is effectively suppressed,
High-density integration of fine devices with excellent device characteristics becomes possible.

[Brief explanation of drawings]

FIGS. 1(a) to (f) are diagrams for explaining the field oxide film forming process in one embodiment of the present invention, and FIGS. 2(a) to (f)
d) is a diagram for explaining a conventional field oxide film forming process. 11...p-type silicon substrate, 12...thermal oxide film, 1
3...Si3N4 film (oxidation-resistant mask), 14...
Polycrystalline silicon layer, 15...p+ type layer, 16... field oxide film.

Claims (3)

[Claims] (1) Forming an oxidation-resistant mask in the element formation region of the semiconductor substrate, and covering the entire surface of the substrate with polycrystalline silicon with a thermal oxide film formed on the substrate surface in the field region surrounded by the oxidation-resistant mask. a step of depositing a film; a step of etching the polycrystalline silicon film by an anisotropic etching method so that it remains only on the side wall of the oxidation-resistant mask; and thermally oxidizing the remaining polycrystalline silicon film and the substrate. 1. A method of manufacturing a semiconductor device, comprising the step of forming a field oxide film. (2) The oxidation-resistant mask is S formed by CVD.
The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is an i_3N_4 film. (3) The method of manufacturing a semiconductor device according to claim 1, wherein the anisotropic etching method is a reactive ion etching method.