JP2000124302A - Semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the formation of deep slits, even when a contact hole is moved into a trench separation region due to deviation in alignment. SOLUTION: In the manufacture of a semiconductor device, a step 4A is formed on the sidewall of a trench of a first shallow trench 4 and a second deep trench 6. Since a contact hole 11 is moved into a trench separation region 8 due to misalignment, the trench separation region 8 is also etched. However, since the etching of the trench separation region 8 is stopped at the position of the step 4A, the depth of a slit being formed by the etching of the trench separation region 8 will not be deeper than that of the first trench 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, to a technique for preventing a deep slit from being formed even when a contact hole covers a trench isolation region due to misalignment.

[0002]

2. Description of the Related Art Along with the miniaturization of LSIs, trench isolation technology has been used in which a trench is dug in a silicon substrate and an oxide film is buried therein to isolate elements. Also, the margin between the contact hole and the diffusion layer has been reduced with the miniaturization of LSI. With reference to FIG. 3, a description will be given of a case where a contact hole overlaps a trench isolation region due to misalignment in a semiconductor device using the trench isolation technique. First, a trench isolation region 8 in which a groove is formed and an oxide film is buried and a diffusion layer 9 are formed in a semiconductor substrate 1, and an interlayer insulating film 10 is further formed. With the above steps, the state shown in FIG.

Next, a contact hole pattern is formed in a predetermined region using a photoresist 17 and the contact hole 11 is formed by dry etching. In this case, since the contact hole 11 is displaced from the diffusion layer 9 due to misalignment, the oxide film in the trench isolation region 8 is also etched when the contact hole 11 is etched, and
8 are formed. With the above steps, the state shown in FIG. Next, in order to prevent a short circuit between the conductive film formed in the slit 18 and the semiconductor substrate 1, ion implantation is performed on the side wall and the bottom of the slit 18 to form a diffusion layer 19. Then, after forming the conductive film 12 in the contact hole 11, the wiring 13 is formed. With the above steps, the state shown in FIG.

[0004]

However, the conventional method for manufacturing a semiconductor device has the following problems (1) and (2). (1) The first problem is that ions must be implanted into the bottom and side walls of the narrow slit formed by misalignment of the contact hole. The reason is that since the trench in the trench isolation region is deeper than the diffusion layer, when a conductive film is formed in the contact hole, the conductive film and the semiconductor substrate are short-circuited.

(2) A second problem is that when a TiN film or the like is formed as a barrier metal on a slit formed due to misalignment of a contact hole, the TiN film does not cover the slit portion. The reason is that the slit portion has a deep and narrow structure. An object of the present invention is to solve the above-described problems of the conventional example, and an object of the present invention is to provide a semiconductor device capable of preventing a deep slit from being formed even when contact hole misalignment occurs. And a method for producing the same.

[0006]

An object of the present invention is to provide a semiconductor device having a trench isolation region formed in a semiconductor substrate and a diffusion layer separated by the trench isolation region. The problem can be solved by providing a step on the side wall of the trench to be formed. This semiconductor device comprises (1) a step of forming a first oxide film on a semiconductor substrate, (2) a step of forming a nitride film on the first oxide film, and (3) a step of forming a nitride film on the nitride film. Patterning a photoresist into a predetermined shape, etching the nitride film, the first oxide film, and the semiconductor substrate to form a first trench; and (4) forming a second trench on the entire surface. Depositing an oxide film and etching it back to form a sidewall film of the second oxide film on the side surface of the first trench; and (5) using the nitride film and the sidewall film as a mask to form the semiconductor. Forming a second trench at the bottom of the first trench by etching the substrate; and (6) a third oxide film having a thickness sufficient to bury the first and second trenches over the entire surface. Is formed and planarized to expose the surface of the nitride film. Except that the step, the third oxide film (7) in said first and second trenches,
Forming a trench isolation region by removing the nitride film, unnecessary third oxide film, and the first oxide film.

[Operation] According to the method of manufacturing a semiconductor device according to the present invention, after forming the first trench, the second trench is formed at the bottom of the first trench. As a result, a step is formed at the bottom of the first trench, and a step is formed on the side wall of the trench including the first trench and the second trench. In the semiconductor device formed as described above, even when the contact hole overlaps the trench isolation region due to misalignment, the contact hole can be stopped at the step portion, so that no slit is formed. Therefore, it is not necessary to implant ions into the slit.

[0008]

Next, embodiments of the present invention will be described in detail with reference to the drawings. [First Embodiment] FIG. 1 is a sectional view of a semiconductor device according to a first embodiment of the present invention. Here, the same or corresponding portions as in FIG. 3 are denoted by the same reference numerals as those used in FIG. First, after an oxide film 2 having a thickness of, for example, 20 nm is formed on a semiconductor substrate 1, a nitride film 3 having a thickness of, for example, 200 nm is formed. Next, a photoresist is patterned on the nitride film 3 into a predetermined shape, and the nitride film 3 and the oxide film 2 are etched by, for example, dry etching using CF ₄ . Thereafter, the semiconductor substrate 1 is etched by, for example, 50 nm by etching using, for example, HBr to form the first trench 4 having a small depth. By the above steps, the state shown in FIG.

Next, an oxide film is formed on the entire surface, and etch back is performed to form a sidewall film 5 made of an oxide film. Then, the semiconductor substrate 1 is formed using the nitride film 3 and the sidewall film 5 as a mask.
Is etched to, for example, 200 nm to form a second trench 6 having a large depth. With the above steps, the state shown in FIG. Next, after removing the side wall film 5 by wet etching using, for example, hydrofluoric acid, a trench filling oxide film 7 is deposited on the entire surface. Through the above steps, the state shown in FIG. As shown in this figure, a step 4A due to the bottom of the first trench 4 is formed between the side wall of the first trench 4 and the side wall of the second trench 6.

[0010] Furthermore, CMP (Chemical Mechanical Po
After performing lithing), the nitride film 3 and the unnecessary buried oxide film 7 are etched back by performing etch-back under etching conditions under which the nitride film and the oxide film have substantially the same etching rate.
Then, oxide film 2 is removed, and trench isolation region 8 is formed. Instead of the method of removing the nitride film and the oxide film by one etch-back, after the nitride film is removed by etching, the unnecessary buried oxide film 7 and the oxide film 2 are removed by etch-back of the oxide film or CMP. The trench isolation region 8 may be formed. After that, by ion-implanting the semiconductor substrate 1, the diffusion layer 9 is formed on the surface of the semiconductor substrate 1.
To form At this time, ion implantation is performed so that the lower surface of the diffusion layer 9 is deeper than the position of the step 4A. Through the above steps, the state shown in FIG. Next, after the interlayer insulating film 10 is formed on the entire surface, a contact hole pattern is formed in a predetermined region using a photoresist, and the contact hole 11 is formed by etching the interlayer insulating film 10 by dry etching. Furthermore, contact hole 1
After forming the conductive film 12 in 1, the wiring 13 is formed.
With the above steps, the state shown in FIG.

In this embodiment, as shown in FIG. 1E, misalignment occurs when the contact hole 11 is formed, and the right end of the contact hole 11 becomes the left end of the trench isolation region 8. And even if a part of the trench isolation region 8 is etched, the etching of the trench isolation region 8 stops at the position of the step 4A. Therefore, the depth of the slit formed by the etching of the trench isolation region 8 is the first. Does not become deeper than the depth of the trench 4. Therefore, since the conductive film 12 and the semiconductor substrate 1 do not short-circuit, it is not necessary to implant ions into the bottom and side walls of the slit.

[Second Embodiment] FIG. 2 shows a second embodiment of the present invention.
FIG. 13 is a cross-sectional view for illustrating the method for manufacturing the semiconductor device according to the embodiment. Here, the same or corresponding parts as those in FIG. 1 are denoted by the same reference numerals as those used in FIG. First, after an oxide film 2 having a thickness of, for example, 20 nm is formed on a semiconductor substrate 1, a nitride film 3 having a thickness of, for example, 200 nm is formed. Next, a photoresist is patterned on the nitride film 3 into a predetermined shape, and the nitride film 3 and the oxide film 2 are etched by, for example, dry etching using CF ₄ . Thereafter, the semiconductor substrate 1 is etched by, for example, 100 nm by etching using, for example, HBr to form the first trench 4 having a small depth. Next, ion implantation of the same conductivity type as a diffusion layer to be formed in the future is performed.
At this time, the ion implantation angle is inclined by about 20 to 45 ° so that the ions are implanted into the side wall and the bottom of the first trench 4, and the implantation energy is increased by 20 to 45 ° while rotating the wafer.
Ion implantation is performed at 40 keV with an implantation amount of about 1E14 to 1E15 / cm ² to form an implantation layer 16. With the above steps, the state shown in FIG.

Next, an oxide film is formed on the entire surface, and etch back is performed to form a sidewall film 5 made of an oxide film. Then, the semiconductor substrate 1 is formed using the nitride film 3 and the sidewall film 5 as a mask.
Is etched to, for example, 200 nm to form a second trench 6 having a large depth. With the above steps, the state shown in FIG. 2B is obtained. Next, after removing the side wall film 5 by wet etching using, for example, hydrofluoric acid, a trench filling oxide film 7 is deposited on the entire surface. With the above steps, the state shown in FIG. Also in the present embodiment, a step 4A due to the bottom of the first trench 4 is formed between the side wall of the first trench 4 and the side wall of the second trench 6, as in the first embodiment. ing.

Further, after performing the CMP, the nitride film 3, unnecessary trench buried oxide film 7 and oxide film 2 are removed to form a trench isolation region 8. Thereafter, a diffusion layer 9 is formed on the surface of the semiconductor substrate 1 by ion implantation. At this time, ion implantation is performed so that the lower surface of the diffusion layer 9 becomes shallower than the position of the step 4A. By the above steps, FIG.
The state shown in is shown. Next, after an interlayer insulating film 10 is formed over the entire surface, a contact hole pattern is formed in a predetermined region using a photoresist, and the interlayer insulating film 10 is etched by dry etching to form a contact hole 1.
Form one. Further, the conductive film 1 is provided in the contact hole 11.
After forming 2, the wiring 13 is formed. With the above steps, the state shown in FIG.

In this embodiment, as in the first embodiment, even if the trench isolation region 8 is etched due to misalignment that occurs when the contact hole 11 is formed, the etching stops at the position of the step 4A. . Further, in the first embodiment, when the depth of the first trench 4 becomes deeper than the diffusion layer 9 due to the variation in etching, the conductive film 12 formed thereafter and the semiconductor substrate 1 are short-circuited. In the present embodiment, since the injection layer 16 is formed after the first trench 4 is formed, even if the depth of the first trench 4 becomes deeper than the diffusion layer 9 due to variation in etching, the contact hole is formed. The conductive film 12 formed in the semiconductor substrate 11 and the semiconductor substrate 1 do not short-circuit.

[0016]

As described above, in the semiconductor device according to the present invention, since the step is provided on the side wall of the isolation trench, the contact hole formed in the interlayer insulating film formed on the semiconductor substrate is provided. Is formed in the trench isolation region due to misalignment, it is possible to avoid formation of a deep slit. Therefore, the step of implanting ions into the bottom and side walls of the slit becomes unnecessary, and a stable and highly reliable film can be formed when a barrier metal is formed in the contact hole. According to the semiconductor device of the present invention,
Since the conductive film filling the contact hole and the semiconductor substrate are not short-circuited, performance and reliability are improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a semiconductor device according to a first embodiment of the present invention in a manufacturing order;

FIG. 2 is a sectional view of the semiconductor device according to the first embodiment of the present invention in the order of manufacturing steps.

FIG. 3 is a sectional view of a conventional semiconductor device in a manufacturing order of the manufacturing process.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2 oxide film 3 nitride film 4 first trench 4A step 5 sidewall film 6 second trench 7 trench buried oxide film 8 trench isolation region 9 diffusion layer 10 interlayer insulating film 11 contact hole 12 conductive film 13 wiring 16 injection Layer 17 Photoresist 18 Slit

Claims (6)

[Claims] 1. A semiconductor device having a trench isolation region formed in a semiconductor substrate and a diffusion layer separated by the trench isolation region, wherein a sidewall of the trench forming the trench isolation region has a step. Semiconductor device. 2. The semiconductor device according to claim 1, wherein said step is formed at a position shallower than a depth of said diffusion layer. 3. The step is formed at a position deeper than the depth of the diffusion layer, and the inside of a side wall extending from the step to the opening of the trench has the same conductivity type as the diffusion layer and a similar concentration. 2. The semiconductor device according to claim 1, wherein said second diffusion layer is formed. 4. A step of forming a first oxide film on a semiconductor substrate; a step of forming a nitride film on the first oxide film; and a step of forming a nitride film on the first oxide film. Forming a first trench by etching the nitride film, the first oxide film, and the semiconductor substrate after patterning a photoresist into a predetermined shape; and (4) forming a second trench on the entire surface. Depositing an oxide film and etching it back to form a sidewall film of the second oxide film on the side surface of the first trench; (5) using the nitride film and the sidewall film as a mask to form the semiconductor Forming a second trench at the bottom of the first trench by etching the substrate; and (6) a third oxide film having a thickness sufficient to bury the first and second trenches over the entire surface. Is formed and planarized to expose the surface of the nitride film. Process and, (7) wherein the nitride film and unnecessary of said third oxide film first
Removing the oxide film and burying the third oxide film in the first and second trenches to form a trench isolation region. 5. After the step (3) and prior to the step (4), a step of forming an implanted layer by ion implantation at the bottom and side walls of the etched semiconductor substrate is added. The method for manufacturing a semiconductor device according to claim 4, wherein: 6. A step of forming a diffusion layer in a surface region of the semiconductor substrate in which the trench isolation region has been formed after the step (7); Forming a film, forming a contact hole exposing a predetermined region of the interlayer insulating film to expose the surface of the diffusion layer, forming a conductive film filling the contact hole, 6. The method for manufacturing a semiconductor device according to claim 4, wherein a step of forming a wiring on the insulating film is added.