JPH0777231B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a semiconductor device having a trench structure portion and a plane structure portion, and a field isolation region of the plane structure portion and a groove. The present invention relates to a method for manufacturing a semiconductor device in which a field isolation region on a side surface and a field isolation region on a bottom surface of a groove are formed in a self-aligned manner.

[Prior Art] FIGS. 8 and 9 are perspective views showing a method of manufacturing a conventional semiconductor device with a trench structure. The conventional method of manufacturing a semiconductor device shown in FIGS.
ational Electron Devices Meeting 1984, p.236〜2
Shown in 39.

First, with reference to FIGS. 8 and 9, a conventional method of manufacturing a semiconductor device with a trench structure will be described. In FIG. 8, first, the trench structure 2 is formed on the main surface side of the silicon substrate 1. Further, in order to form an integrated circuit on the silicon substrate 1 by the subsequent steps, the A-side surface and the B-side surface which are the divided side surfaces of the trench structure 2 and the C-side surface which is the main surface of the silicon substrate 1 are Must be electrically isolated from each other. Such electrical isolation of the surface on the semiconductor substrate is called field isolation, and it is an ordinary large scale integrated circuit (LS) that does not have a trench structure as shown in FIG.
In the case of I), the so-called LOCOS (Local Oxidation of Silico) is a selective oxidation method using a silicon nitride film.
Field separation on the main surface of the semiconductor substrate is performed by n). However, since an effective method of applying the LOCOS method to the sidewall of the trench structure of the semiconductor substrate has not been found, in the case of the silicon substrate 1 having the trench structure 2 as shown in FIG. As shown in FIG. 9, an insulator 11 such as silicon oxide is buried in the groove 2 to perform the necessary field separation. This insulator 11
Is filled with the insulator 11 once in the trench structure 2 by, for example, a vapor phase chemical reaction (CVD), and then a necessary portion is covered with a resist by a photolithography method to completely remove the unnecessary portion of the insulator 11. Alternatively, it is carried out by etching away a part. By this, side A, B
The electrical separation of the plane and the C plane is achieved, and the subsequent steps of integrated circuit manufacturing are executed.

[Problems to be Solved by the Invention] Since the conventional semiconductor device with a trench structure is manufactured by the above method, it is necessary for compensating a mask alignment shift due to photolithography when performing field separation. Must be covered with a resist having sufficient margins (α and β in FIG. 9) for etching, and as shown in FIG. 9, insulators are formed on the side surfaces A and B of the trench structure portion 2. There is a problem in that the area 11 that extends laterally increases the amount of waste in the field separation. Further, it is difficult to keep the height of the main surface of the silicon substrate 1 and the height of the upper surface of the embedded insulator 11 the same over the entire surface of the wafer. For example, a step occurs at the portion indicated by γ in FIG. There has been a problem that leakage current increases in the subsequent integrated circuit (eg, MOS transistor) manufacturing process.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to form the field separation region of the flat surface portion, the field separation region of the groove side surface, and the field separation region of the groove bottom surface in a self-aligned manner. It is to provide a method of manufacturing a semiconductor device having a trench structure that can be formed.

[Means for Solving Problems] In a method of manufacturing a semiconductor device according to the present invention, a groove is formed in a part of a semiconductor substrate, and a silicon nitride film is formed on the main surface of the semiconductor substrate and the entire region inside the groove. A first field isolation region is defined on the main surface of the semiconductor substrate, a second field isolation region is defined on the side surface of the groove so as to be continuous with the first field isolation region, and a third field isolation region is defined on the bottom of the groove. The silicon nitride film is selectively removed so as to define the field isolation region, and the field oxide film is formed on the first, second and third field isolation regions by the selective oxidation method. is there.

[Operation] According to the method of manufacturing a semiconductor device of the present invention, a flat surface portion of a semiconductor substrate, a side surface portion of a groove, and a predetermined region of a bottom portion of the groove are provided.
The field isolation region is formed in a self-aligning manner by the selective oxidation method, and in particular, the field isolation region on the flat surface and the field isolation region on the side surface of the groove are connected in a self-aligning manner without deviation, and a step is formed on the flat surface. Absent.

[Embodiment of the Invention] An embodiment of a method for manufacturing a semiconductor device according to the present invention will be described below with reference to the drawings.

1 to 6 are diagrams showing respective process steps of a method for manufacturing a semiconductor device according to an embodiment of the present invention, in which (a) is a plan view of the semiconductor device and (b) is a plan view thereof. ) Is a sectional view taken along the line AB in FIG.
(C) is a sectional view taken along the line CD in (a), and (d) is a sectional view taken along the line EF in (a). Further, FIG. 7 is a perspective view showing the semiconductor device at the final process stage of the present embodiment shown in FIG.

First, referring to FIG. 1, a silicon oxide film 3 having a thickness of about 100 to 1000 Å is formed on a silicon substrate 1 by thermal oxidation or another method. Next, a silicon nitride film 4 having a thickness of 500 to 1500Å and a silicon oxide film 5 having a thickness of 2000 to 3000Å are deposited on the silicon oxide film 3 by, for example, a CVD method. Further, a resist pattern (not shown) is formed on the silicon oxide film 5 by photolithography so as to have an opening defining a desired trench region. Then, the silicon oxide film 5, the silicon nitride film 4, the silicon oxide film 3 and the silicon substrate 1 are sequentially anisotropically plasma-etched through the openings defined by the resist pattern, and the silicon oxide film 5, silicon nitride film 4, and silicon substrate 1 are sequentially subjected to anisotropic plasma etching. d)
As shown in FIG. 5, the trench structure 6 having a predetermined depth is formed. At this time, the silicon oxide film 5 acts as an etching mask against the trench etching that requires a long time.

Next, referring to FIG. 2, the resist pattern (not shown) and the silicon oxide film 5 are removed by etching. Further, a silicon oxide film 3A equivalent to the silicon oxide film 3 is formed on the entire surface of the cross section of the silicon substrate 1 inside the trench structure 6, and further on the entire surface of the silicon nitride film 4 and the entire inner region of the trench structure 6, For example thickness
A 1000Å silicon nitride film 7 is deposited using the CVD method.

Next, referring to FIG. 3, a photoresist is applied to the entire surface of the silicon nitride film 7 with a thickness sufficient to fill the trench structure 6 to form a photoresist layer 8 (FIG. 3 (b)). ). Next, a third photolithography method is used.
A pattern for defining the field separation region is formed as shown in the plan view of FIG. Further, as shown in FIGS. 3A and 3D, the grooved structure is surrounded by a part of the side surface of the grooved structure 6 connected to the field isolation region of the plane portion and the cross section of the photoresist layer 8. Form a vertical hole 6 ′ that extends to the bottom of 6. Such a hole 6 '
Is, for example, SCIENCE FORUM, Submicron Lithography Comprehensive Technical Data Book, Chapter 5, Section 4, Page 302 (198
The multi-layer resist method described in (5 years) can be easily formed by using anisotropic etching with oxygen-based plasma. After patterning the photoresist layer 8 and forming the holes 6 ', Freon-based isotropic plasma etching is performed by an amount corresponding to the thickness of the silicon nitride film 7, as shown in FIG. 3 (d). The silicon nitride film 7 is removed from the field isolation region of the plane portion and the hole 6 '.

Next, referring to FIG. 4, after the photoresist layer 8 is removed, anisotropic plasma etching (Reactive
Ion Etching) removes the silicon nitride film 4 exposed in the field isolation region of the flat surface, and removes the silicon nitride film 7 covered with the resist layer 8 from the entire surface of the silicon substrate 1. Although removed, the silicon nitride film 7 formed on the side surface of the trench structure 6 is left as it is as shown in FIGS. 4B and 4D because of anisotropic etching. Next, (b) and (c) of FIG.
And as shown in (d), an impurity diffusion layer 9 is formed in a region not covered with the silicon nitride film 7 by ion implantation or the like.

Next, referring to FIG. 5, using the silicon nitride film 4 left on the surface of the silicon substrate 1 and the silicon nitride film 7 left on the side surfaces of the trench structure 6 as an oxidation mask, a normal LOCOS film is formed. By the method, a portion without a silicon nitride film is selectively oxidized to form an oxide film 10 for field separation.

Next, referring to FIG. 6, the remaining silicon nitride films 4 and 7 are removed by etching, and further the silicon oxide films 3 and 3A thereunder are removed by etching, whereby the surface of the silicon substrate 1 and the trench structure 6 are removed. The formation of the field oxide film 10 having a desired shape is completed on the side surface and the bottom surface.

Next, FIG. 7 is a perspective view of the semiconductor device in the final process stage shown in FIG. As shown in FIG. 7, according to the manufacturing method of the present invention, the oxide film 10 for field separation is formed in predetermined regions of the surface portion of the silicon substrate 1 and the side surface portion and the bottom surface portion of the trench structure 6. Are formed in a self-aligning manner by the LOCOS method, and in particular, they are formed in a self-aligning manner so that the field isolation oxide film region on the surface portion and the field isolation oxide film region on the trench side surface are connected without displacement. In the region indicated by γ, a steep step that increases the leak current of the transistor does not occur.

In the above embodiment, the silicon nitride film 7 is formed on the silicon nitride film 4 so as to be in close contact with the silicon nitride film 4, and the silicon nitride film 4 is left on the flat surface of the silicon substrate 1 due to the etching time difference. A silicon oxide film may be further interposed between the two silicon nitride films 4 and 7. In this case, the selectivity due to the difference in material can be utilized during anisotropic etching of the silicon nitride film shown in FIG. 4, and control becomes easy.

Although the photoresist layer 8 as shown in FIG. 3 is used in the above embodiment, this layer may be made of resin other than resist such as polyimide or glass if it is removed by the multi-layer resist method. It may be an inorganic substance.

Further, the other side surface of the trench structure portion 6 facing the field oxide film may be used as a constituent region of a capacitor or the like.

[Effects of the Invention] As described above, according to the present invention, the field isolation region on the plane portion of the semiconductor substrate, the field isolation region on the side surface and the field isolation region on the bottom surface of the trench structure are formed by the selective oxidation method. Since they are formed in a self-aligned manner, the field isolation regions are connected without waste due to the alignment margin, and the integration degree of the semiconductor device can be improved. Further, since no step is formed between the surface of the semiconductor substrate and the field isolation region, it is possible to reduce the leak current of the integrated circuit formed on the semiconductor substrate in the subsequent steps.

[Brief description of drawings]

1 to 6 are diagrams showing respective process steps of a method for manufacturing a semiconductor device according to an embodiment of the present invention. FIG. 7 is a perspective view showing the final step of the method of manufacturing a semiconductor device according to an embodiment of the present invention. 8 and 9 are perspective views showing a conventional method for manufacturing a semiconductor device. In the figure, 1 is a silicon substrate, 2, 6 are trench structures, 3, 3A,
Reference numeral 5 is a silicon oxide film, 4 and 7 are silicon nitride films, 8 is a photoresist layer, 9 is an impurity diffusion layer, and 10 is a field oxide film.

Claims (5)

[Claims] 1. A method of manufacturing a semiconductor device having a trench structure section and a planar structure section, comprising: a first step of preparing a semiconductor substrate having a main surface; and a part of the semiconductor substrate as an active region. A second step of forming a groove having a main surface to be used and a side surface, a third step of forming a silicon nitride film on the main surface of the semiconductor substrate and over the entire region inside the groove, the semiconductor A first field isolation region is defined on the main surface of the substrate, and a second field isolation region is defined on the side surface of the groove so as to be continuous with the first field isolation region, and the bottom of the groove is defined. Selectively removing the silicon nitride film so as to define a third field isolation region, and forming a field oxide film in the first, second and third field isolation regions by a selective oxidation method. And a fifth step, a method of manufacturing a semiconductor device. 2. The second step is a step of forming a resist pattern on the main surface of the semiconductor substrate so as to define an opening of the groove, and anisotropic plasma etching is performed from the opening. The method for manufacturing a semiconductor device according to claim 1, further comprising: 3. The second and third steps include a step of forming a first silicon nitride film only on the main surface of the semiconductor substrate, and a step of forming a first silicon nitride film on the first silicon nitride film and inside the groove. The method of manufacturing a semiconductor device according to claim 1, further comprising the step of forming a second silicon nitride film over the entire surface of the region. 4. The step of forming a photoresist layer on the entire surface of the silicon nitride film so as to fill the inside of the groove, and the step of defining the first field isolation region. Patterning a photoresist layer, a portion on the side surface of the groove that is continuous with the first field isolation region inside the groove, and defines the second field isolation region; Forming a vertical hole surrounded by the cross section of the resist layer and reaching the bottom of the groove; the first field isolation region on the main surface; and the second field isolation inside the hole. Etching away the silicon nitride film from the region, removing all the photoresist layer, and removing the silicon from the third field isolation region at the bottom of the trench. The nitride film and a step of etching away, a method of manufacturing a semiconductor device as set forth in claim 1, wherein the appended claims. 5. The fourth step is a step of forming a photoresist layer on the entire surface of the second silicon nitride film so as to fill the inside of the groove, and the first field isolation region is defined. Patterning the photoresist layer as described above, and a portion on the side surface of the groove that is continuous with the first field isolation region inside the groove so as to define the second field isolation region. Forming a vertical hole surrounded by the cross section of the photoresist layer and reaching the bottom of the groove; the first field isolation region on the main surface; and the second field inside the hole. Removing the second silicon nitride film from the first field isolation region, removing all of the photoresist layer, and removing the first field isolation region from the first field isolation region. The silicon nitride film, wherein and a step of the third and the second silicon nitride film from the field isolation region in the bottom of the trench is etched away, a method of manufacturing a semiconductor device of the third term recited in the claims.