JP2002184857A - Semiconductor integrated circuit device and its fabricating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor integrated circuit device having a structure suitable for high integration in which the isolation characteristics, operational characteristics, reliability and yield are enhanced by a selective oxide film for isolating element forming regions from each other. SOLUTION: Element forming regions 2-1, 2-2,... for forming discrete elements, e.g. transistors, are arranged on the surface part of a semiconductor substrate 1 and surrounded by selective oxide films 3-1, 3-2,... for isolating element forming regions from each other having a constant width of 1 μm or less. The selective oxide films 3-1, 3-2,... for isolating element forming regions from each other are formed by forming an oxidation resistant sidewall 15 on the inner circumferential surface of a mask opening 14a and oxidizing it after shrinking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit device, and more particularly to a semiconductor integrated circuit device with high reliability and high integration, and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 3 is a plan view showing a conventional semiconductor integrated circuit device, schematically showing the arrangement of element formation regions and isolation regions between element formation regions. In general, as shown in FIG. 3, a semiconductor integrated circuit device includes, on a semiconductor substrate 1 such as silicon, element forming regions (active regions) 2-1, 2-2,.・ ・
, And element isolation regions 3 that insulate and isolate the element formation regions 2-1, 2-2,... From each other.

For high integration, it is necessary to reduce the size of each element and to reduce the width and area of an element isolation region, that is, an element isolation insulating region. Conventionally, junction isolation
LOCOS (Local Oxidation
of Silicon) method, trench with embedded insulator (tr
ench) method.

For example, in the LOCOS method, a selective oxide film is formed by oxidizing a field region other than an element formation region on a semiconductor substrate using an oxidation-resistant insulating film such as a silicon nitride film as a mask. In this method, a film is used as an element isolation region. 4 (A) to 4 (D) show a conventional L
FIG. 4 is a process chart showing a process of forming an element isolation insulating film by an OCOS method. Hereinafter, a procedure of a process of forming an element isolation insulating film by a LOCOS method will be described with reference to FIGS. 4A to 4D.

As shown in FIG. 4A, first, a pad oxide film 22 made of SiO ₂ and an oxidation resistant mask film 23 made of SiN having oxidation resistance are sequentially formed on a semiconductor substrate 21 to a predetermined thickness. Then, a patterned resist film 24 for selective oxidation is formed on the oxidation-resistant mask film 23.

Next, as shown in FIG. 4B, the oxidation-resistant mask film 23 and the pad oxide film 22 are etched using the resist film 24 as a mask, and the semiconductor substrate 21 is recess-etched to a desired depth (selective etching). Etching of semiconductor substrate surface in anticipation of expansion of oxidized part due to oxidation)
I do. 25 denotes a semiconductor substrate 21 formed by recess etching.
This is a recess formed on the surface.

Thereafter, the resist film 24 is removed, and the surface of the semiconductor substrate 21 is thermally oxidized using the oxidation-resistant mask film 23 as a mask, thereby forming the exposed portion of the semiconductor substrate 21 as shown in FIG. A selective oxide film 26 is formed.
FIG. 4D shows selective oxide films 26a and 26b having different widths formed in this manner.

[0008]

By the way, in the conventional semiconductor integrated circuit device, as shown in FIG. 3, a selective oxide film 26 is formed in all the field regions other than the element formation region as element isolation regions, and the element formation region is formed. Since the regions are separated from each other, as shown in FIG. 4D, a thin selective oxide film 26a and a thick selective oxide film 26b coexist, and the element isolation effect is poor due to the thickness of the selective oxide film 26. There was a problem of uniformity.

This is because the thickness of the selective oxide film 26 formed by the thermal oxidation process is different due to the difference in the formation width and area of the selective oxide film. Specifically, width,
In the element isolation region having a small area, the recess etching is shallow, the thickness of the thermal oxide film is small, and a thin insulating film such as the selective oxide film 26a is formed. On the other hand, in the element isolation region having a large area, the recess etching is deep, the thickness of the thermal oxide film is large, and a thick insulating film such as the selective oxide film 26b is formed. Therefore, the thickness of the selective oxide film 26 becomes non-uniform.

As described above, if the thicknesses of the selective oxide films 26a and 26b are not uniform, these selective oxide films 26a and 26b
In the case where a channel stopper is formed by implanting ions for preventing a reduction in punch-through voltage between element forming regions during 6b, the implantation depth becomes non-uniform. For this reason, there is a problem that the punch-through voltage between the element forming regions is partially reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. In a semiconductor integrated circuit device, an element isolation region made of a selective oxide film having a uniform thickness can be formed. An object is to improve uniformity and reliability of element isolation characteristics.

[0012]

According to a first aspect of the present invention, there is provided a semiconductor integrated circuit device, wherein a plurality of element forming regions formed on a semiconductor substrate are surrounded by a selective oxide film for isolating between element forming regions having substantially the same width. It is characterized by being surrounded by.

Therefore, according to the semiconductor integrated circuit device of the first aspect, the periphery of each element forming region is surrounded by the selective oxide film for separating the element forming regions having substantially the same width. The thickness of the selective oxide film for separation can be made substantially uniform. Accordingly, the uniformity and reliability of the isolation characteristics between the element formation regions can be improved.

According to a second aspect of the invention, there is provided a method of manufacturing a semiconductor integrated circuit device, comprising: forming a first insulating film (for example, SiO ₂ ) on a semiconductor substrate, and then forming a selective oxide film for separating the element formation region of the film. An opening is formed by selectively etching a portion to be formed, and then a second insulating film (for example, SiN) having oxidation resistance is deposited on the first insulating film including the inner peripheral surface of the opening, Next, the film is etched back by anisotropic etching to leave a sidewall film made of the film on the inner peripheral surface of the opening, and thereafter, the surface of the semiconductor substrate is oxidized using the second insulating film as a mask. By doing so, the selective oxide film for isolation between the element formation regions is formed.

Therefore, according to the method of manufacturing a semiconductor integrated circuit device of the second aspect, the sidewall film made of the second insulating film formed on the inner peripheral surface of the opening of the first insulating film is also formed by the first insulating film. Since selective oxidation can be performed as an oxidation-resistant mask for selective oxidation together with the second insulating film on the insulating film, the opening formed by photolithography can be further shrunk by the sidewall made of the second insulating film. Therefore, the surface of the semiconductor substrate can be oxidized through the shrinked opening, so that the width of the selective oxide film for isolation between element formation regions can be narrowed beyond the limit of miniaturization by photolithography, and as a result, High integration can be achieved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor integrated circuit device according to the present invention basically includes a plurality of element forming regions formed on a semiconductor substrate, each having a substantially same width between element forming regions. The selective oxide film is surrounded by a selective oxide film for isolation, and the selective oxide film is formed by oxidizing after performing recess etching on the surface of the semiconductor substrate using the second insulating film (oxidation-resistant mask film) as a mask. Or may be formed without recess etching.
The present invention can be implemented in any of the aspects.

Further, in order to further narrow the width of the selective oxide film in order to further increase the degree of integration of the semiconductor integrated circuit device, a portion of the first insulating film where the selective oxide film for separating the element formation regions is to be formed is selectively formed. After the opening is formed by etching, the second
Forming an insulating film on the first insulating film and the inner peripheral surface of the opening, and then removing the portion of the second insulating film deposited on the semiconductor substrate in the opening in the second insulating film. Etch back by anisotropic etching to a thickness of about
The surface of the semiconductor substrate may be oxidized using the second insulating film as a mask to form a selective oxide film for isolation between element formation regions. That is, the opening exposing the surface of the semiconductor substrate is shrunk by making full use of the sidewall technology, and the opening is reduced beyond the limit of miniaturization of photolithography.

However, making full use of such a technique is not necessarily indispensable for manufacturing the semiconductor integrated circuit device of the first aspect. The first insulating film corresponds to a so-called pad insulating film, which is generally made of SiO ₂ , and formed by heating and oxidizing a semiconductor substrate. The second insulating film serves as an oxidation-resistant mask film, and is generally made of oxidation-resistant SiN.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 is a plan view showing a first embodiment of the semiconductor integrated circuit device of the present invention, and schematically shows the arrangement of element formation regions and isolation regions between element formation regions.

2-1 are element forming regions where individual elements such as transistors are formed on the surface of the semiconductor substrate 1 made of single-crystal silicon.
,... Are formed on the surface of the semiconductor substrate 1 so as to surround the element forming regions 2-1, 2-2,. As shown in FIG. 1, the film is formed to have a substantially constant width (for example, 1 μm).

Since the widths of the selective oxide films 3-1, 3-2,... Are made uniform, the semiconductor substrate 1 has no element forming region and a portion where no selective oxide film is formed. . 31 indicates such a part.

According to the present semiconductor integrated circuit device, the selective oxide films 3-1 and 3 for isolation between element formation regions have substantially the same width around each of the element formation regions 2-1 2-2. −
, Can be made substantially uniform in the thickness of the selective oxide films 3-1, 3-2,... Between the element formation regions. The thickness of the selective oxide film for separation can be made substantially uniform. Therefore, the uniformity and reliability of element isolation characteristics can be improved. Since the thicknesses of the selective oxide films 3-1, 3-2,... Are substantially the same, the depth appropriate for the implantation depth of the impurity ion implantation for forming the channel stopper is the region where the channel stopper is to be formed. Can be uniform over the entire area. Therefore, even if the impurity is ion-implanted with the same energy, the best channel stopper can be formed for each of the selective oxide films 3-1, 3-2,....

FIGS. 2A to 2F show a main part (selective oxide film) of a method of manufacturing the semiconductor integrated circuit device of FIG. 1 (first embodiment of the method of manufacturing a semiconductor integrated circuit device of the present invention). FIG. 4 is a cross-sectional view illustrating a method of forming a semiconductor device in the order of steps. Next, FIG.
A method for forming a selective oxide film in the semiconductor integrated circuit device of FIG. 1 will be described with reference to FIG.

(A) As shown in FIG. 2A, a pad oxide film (corresponding to a first insulating film in the claims) 12 having a thickness of, for example, about 100 nm is formed on a semiconductor substrate 11. Then, a resist film is formed on the pad oxide film 12, and the resist film is patterned. Reference numeral 13 denotes the patterned resist film. The resist film 13
Is formed at a value (for example, 1 μm or less) close to the resolution limit determined by the performance of the exposure apparatus and the photosensitive film material.

(B) Next, the pad oxide film 12 is etched using the resist film 13 as a mask. Reference numeral 12a denotes an opening formed by this etching.
After the formation of a, the resist film 13 is removed. This allows
As shown in FIG. 2B, a pad oxide film 12 having an opening 12a having a width W remains on the silicon substrate 11.

Further, as shown in FIG. 2C, an oxidation-resistant mask film 14 made of silicon nitride is deposited on the surface of the pad oxide film 12 and the opening 12a. At this time, the thickness of the oxidation-resistant mask film 14 formed on the surface of the pad oxide film 12 is, for example, 150 to 600 nm in consideration of the etching at the time of forming a sidewall film made of silicon nitride later. The thickness of the oxidation-resistant mask film 14 on the side wall (inner peripheral surface) and the bottom surface of the opening 12a is slightly smaller than the thickness on the pad oxide film 12 (150 to 600 nm).

After forming such an oxidation resistant mask film 14, anisotropic etching is performed without using a mask. At this time, the oxidation resistant mask film 14 on the pad oxide film 12
Etching is performed so that a thickness of nm or more can be maintained. Thereby, as shown in FIG. 2D, a sidewall 15 made of silicon nitride is formed on the inner peripheral surface (side wall) of the opening 12a.

After the formation of the sidewalls 15, the surface of the exposed portion of the semiconductor substrate 11 is subjected to a thermal oxidation process using the oxidation-resistant mask film 14 and the sidewalls 15 as a mask to form a thermal oxide film 16 as a field oxide film. , 300-500
It is formed to a thickness of about nm. Next, the first nitride film 14 and the sidewalls 15 are removed. As a result, FIG.
The selective oxide film 16 as shown in (E) and (F), that is, the selective oxide film 3-1 in FIG. 1 is formed. Note that FIG.
(F) shows, for example, two element formation regions 2-1 in FIG.
2-2, two selective oxide films 3-1 formed corresponding to
3-2 is shown.

As described above, according to the method of manufacturing the semiconductor integrated circuit device, the side wall 15 formed on the inner peripheral surface of the opening 12 a of the pad insulating film 12 also has the oxidation-resistant mask film on the pad insulating film 12. Since the selective oxidation can be performed as an oxidation-resistant mask for selective oxidation together with 14, the opening formed by photolithography can be shrunk by the sidewall 15 made of silicon nitride having further oxidation resistance.
Through the shrinked opening 12a, the semiconductor substrate 1
Since the surface portion can be oxidized, the width of the selective oxide film 3 for isolation between element formation regions can be narrowed beyond the limit of miniaturization by photolithography, and thus high integration can be achieved. .

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible. For example, there are the following modifications.

(1) In the method of forming the selective oxidation film, immediately after forming the oxidation-resistant mask film 14 and the side wall 15,
Although the selective oxidation film 16 is formed, the exposed surface of the semiconductor substrate 11 may be recess-etched before thermal oxidation, and then thermal oxidation may be performed. Even in this case, since the width of the opening 12a is constant, the etching depth of the recess etching becomes uniform, and the depth of the selective oxide film 13 for isolation between element formation regions becomes uniform. There is no danger of causing any trouble.

(2) In order to prevent a reduction in punch-through voltage between element formation regions, a channel stopper may be formed by implanting ions after performing a thermal oxidation process for forming a selective oxide film. good.

[0033]

According to the semiconductor integrated circuit device of the first aspect, since the periphery of each element forming region is surrounded by the selective oxide film having substantially the same width, the selective oxide film having a substantially uniform thickness is provided. Isolation between element formation regions can be performed. Uniform separation characteristics between electric element formation regions can be obtained, and operation characteristics, reliability, and yield can be improved.

That is, since the thickness of the selective oxide film is substantially the same,
For example, when a channel stopper is formed thereunder, an appropriate depth as the implantation depth of the impurity ion implantation for forming the channel stopper can be made uniform over the entire region of the selective oxide film formation region. Therefore, even if the impurity is ion-implanted with the same energy, it is possible to form the best channel stopper for each selective oxide film.

According to the semiconductor integrated circuit device of the second aspect,
The sidewall film made of the second insulating film formed on the inner peripheral surface of the opening of the first insulating film can also be selectively oxidized together with the second insulating film on the first insulating film as an oxidation resistant mask for selective oxidation. Therefore, the opening formed by photolithography can be further shrunk by the sidewall made of the second insulating film, and the surface of the semiconductor substrate can be oxidized through the shrinked opening, so that the width of the selective oxide film for isolation between element formation regions can be reduced. Can be made narrower than the limit of miniaturization by photolithography, and thus higher integration can be achieved.

[Brief description of the drawings]

FIG. 1 is a plan view showing a first embodiment of a semiconductor integrated circuit device of the present invention.

FIG. 2 is a process diagram showing a main part of a method of manufacturing a selective oxide film in the semiconductor integrated circuit device of FIG. 1 (first embodiment of the method of manufacturing a semiconductor integrated circuit device of the present invention) in the order of steps;

FIG. 3 is a plan view showing one conventional example of a semiconductor integrated circuit device.

FIG. 4 is a cross-sectional view sequentially showing a conventional method for forming a selective oxide film for isolation between element formation regions.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Element formation area, 3 ...
Selective oxide film for isolation between element formation regions, 11: semiconductor substrate, 12: first insulating film (pad oxide film), 13 ·
..Resist film, 14: second insulating film (oxidation-resistant mask film), 15: sidewall, 16: selective oxide film for isolation between element formation regions.

Claims (3)

[Claims] A plurality of element forming regions formed on the surface of the semiconductor substrate, each of which is surrounded by a selective oxide film for separating the element forming regions formed on the surface of the semiconductor substrate having substantially the same width; A semiconductor integrated circuit device comprising: 2. A semiconductor device according to claim 1, wherein each of the plurality of element forming regions formed on the surface of the semiconductor substrate is surrounded by a selective oxide film for separating the element forming regions formed on the surface of the semiconductor substrate having substantially the same width. In the method for manufacturing a semiconductor integrated circuit device according to the above, after forming a first insulating film on the semiconductor substrate,
Forming an opening by selectively etching a portion of the insulating film where the selective oxide film for isolation between element formation regions is to be formed; and forming an acid-resistant layer on the first insulating film including the inner peripheral surface of the opening. Forming a second insulating film having a chemical property; and forming the second insulating film into a thickness anisotropic enough to remove at least a portion of the second insulating film exposed on the surface of the semiconductor substrate exposed to the opening. Etching back by reactive etching; and oxidizing a surface portion of the semiconductor substrate using the second insulating film as a mask to form the selective oxide film for isolation between element forming regions. Of manufacturing a semiconductor integrated circuit device. 3. The first insulating film is made of SiO ₂ ,
3. The method according to claim 2, wherein the second insulating film is made of SiN.