JP2000299373A - Semiconductor element containing conductor film in field oxide film and forming method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize electrical characteristics of an element by forming a conductor film on a first field insulating film for embedding one part of a trench, and at the same time forming a second field insulating film onto the conductor film for embedding the remaining part of the trench. SOLUTION: A first field oxide film 43 is formed on a semiconductor substrate 40 by a deposition process, and a conductor film 44 is formed. The conductor film 44 and the first field oxide film 43 are subjected to a etch back process, and a nitride film 42 is exposed for leaving the conductor film 44 merely in the trench. Then, on the conductor film 44, a second field insulating film 45 is formed via oxidation process or deposition process, the etch back process is made for leaving the second field insulating film 45 merely in the trench, and the remaining part of the trench is embedded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device including a field oxide film for separating devices formed on a semiconductor wafer, and more particularly to a semiconductor device having a conductor film in a field oxide film and its manufacture. It is about the method.

[0002]

2. Description of the Related Art As is well known, a static random access (SRAM)
ess memory), DRAM (dynamic random access memory),
And ferroelectric random access mem
(Ory, FeRAM) includes an active region and a field region. A number of devices such as transistors are formed in an active region, and a number of field oxide films for device isolation are formed in a field region.

[0003] As semiconductor elements are highly integrated,
The formation of a field oxide film for isolation between devices has become important. As one of such element isolation methods, a LOCOS (LOCal Oxidation of Silicon) process is widely used. On the other hand, as another method, STI
The (shallow trench isolation) step can prevent a thin oxide film from being formed in a narrow region or a thick oxide film from being formed at an edge of an active region.

[0004] However, as the size of the device becomes smaller, the field oxide film becomes thinner. Therefore, there arises a problem that the threshold voltage and the like change due to the influence of the electric field due to the potential difference between the junction region and the semiconductor substrate. In addition, the characteristics of the semiconductor element are degraded due to the potential change of the adjacent element.

FIG. 1 is a plan view showing a DRAM cell, and FIG. 2 is a sectional view taken along the line AA 'in FIG. Here, reference numeral 10 denotes a semiconductor substrate, 11 denotes a field oxide film, 14 denotes a gate insulating film, 15 denotes a gate electrode,
Numeral 16 indicates a bonding region. As shown in FIG. 2, a field oxide layer (FOX) is formed in a field region, and a junction region and a channel region are formed in an active region.

Hereinafter, a conventional method for manufacturing a semiconductor device will be described with reference to FIGS.

Referring to FIG. 3, an oxide film 11 and a nitride film 12 are sequentially formed on a semiconductor substrate 10, and a mask (not shown) defining a plurality of field regions is formed on the nitride film 12. Next, the nitride film 12, the oxide film 11, and a part of the semiconductor substrate 10 are selectively etched in order to form a trench in a field region.

Referring to FIG. 4, after removing the mask,
A field insulating film 13 is formed inside the trench and on the nitride film 12. Next, chemical mechanical polishing (CMP, chemical mec
hanical polishing) or etch-ba
ck) The step is performed to leave the field insulating film 13 only in the trench.

Referring to FIG. 5, the nitride film 12 and the oxide film 11 are sequentially etched to complete the formation of the field oxide film.

Referring to FIG. 6, a gate insulating film 14, a gate electrode 15, and a junction region 16 are sequentially formed. Therefore, a channel region is formed between the junction regions below gate electrode 15.

In this case, as described above, since the field insulating film 13 is a non-conductor, the electric field is attenuated.
n) is transmitted to the channel region without any change. Further, the field insulating film 13 forms a capacitor together with the junction region and the channel region.
3 serves as a dielectric layer of the capacitor. Therefore, a change in the potential of the junction region causes a change in the potential of the channel region formed below the gate electrode.

[0012] N-channel enhancement
hancement) MOSFET (metal oxide semi conductor field
effect transistor) as an example, the junction region 1
When the potential of the semiconductor substrate 10 is higher than the potential of the semiconductor substrate 10, the potential of the channel region, particularly the region adjacent to the field region, becomes higher than the potential of the semiconductor substrate 10 due to the potential of the junction region.

A depletion region (depletion regio) in the active region
From the viewpoint of n), the carrier in the active region adjacent to the field region is depleted by the change in the potential of the junction region 16, resulting in a decrease in the threshold voltage of the semiconductor device. This is due to the influence of the electric field due to the potential difference between the channel region below the gate electrode and the junction region 16.

FIG. 7 shows an equipotential line (e) according to the distance from the center of the channel region and the depth from the surface of the semiconductor substrate in FIG.
5 is a diagram showing a potential distribution using a qui-potential line). FIG. 7 illustrates a case where the potential of the junction region adjacent to the channel region is higher than the potential of the semiconductor substrate.
As can be seen from FIG. 7, the intervals between the equipotential lines are extremely narrow, and the inclination of the equipotential lines is steep in the field region. This may cause the potential of the channel region to fluctuate easily due to a change in the potential of the adjacent junction region, thereby deteriorating the device characteristics.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention suppresses a change in the potential of a channel region due to the potential of an adjacent device or a junction region, thereby reducing the electric potential of the device. It is an object of the present invention to provide a semiconductor device having a field oxide film capable of stabilizing characteristics and a method for manufacturing the same.

[0016]

In order to achieve the above-mentioned object, the present invention provides an active region including a junction region and a channel region and a field region on which a field oxide film for element isolation is formed. A semiconductor device comprising: a first step of providing a semiconductor structure having a trench in the field region; a second step of forming a first field insulating film in the trench; A third step of forming a conductive film and filling a part of the trench, and a fourth step of forming a second field insulating film on the conductive film and filling the remaining part of the trench.

In a semiconductor device including an active region formed by a junction region and a channel region and a field region formed with a field oxide film for device isolation, a semiconductor substrate having a trench in the field region A first field insulating film formed in the trench, a conductive film filling a part of the trench, and a conductive film formed on the conductive film and filling the remaining part of the trench. A second field insulating film.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the most preferred embodiment of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention belongs can easily implement the technical idea of the present invention. The description will be made with reference to the accompanying drawings.

According to the present invention, a conductive film is formed in a field oxide film for device isolation so as to reduce undesired effects due to a change in an adjacent device and reduce the package density.
Provided is a semiconductor device capable of improving the density and the characteristics of the semiconductor device.

A method of manufacturing a semiconductor device according to an embodiment of the present invention will be described with reference to FIGS.

Referring to FIG. 8, after an oxide film 41 and a nitride film 42 are sequentially formed on a semiconductor substrate 40, a mask (not shown) defining a plurality of field regions is formed on the nitride film 42. Next, the nitride film 42, the oxide film 41, and a portion of the semiconductor substrate 40 are selectively etched to form a trench in the field region, thereby forming a semiconductor structure having the trench.

Next, after removing the mask, a first field insulating film 43 is formed on the side walls and the lower portion of the trench through a deposition process or an oxidation process. In this case, when the first field insulating film 43 is formed through a deposition process, the first field insulating film 43 is formed on the entire surface of the semiconductor structure having the trench, and when the first field insulating film 43 is formed through an oxidation reaction. Is formed only in the exposed portion of the semiconductor substrate 40 in the trench by the oxidation reaction of the semiconductor substrate 40.
The first field insulating film 43 is formed of a nitride film or an oxide film.

Next, a conductor film 44 is formed on the first field oxide film 43. As the conductor film 44, single crystal silicon, polycrystal silicon, amorphous silicon, or a stacked structure of a combination thereof can be used.

Referring to FIG. 9, the conductive film 44 and the first
A chemical mechanical polishing process or an etch back process is performed on the field insulating film 43 to expose the nitride film 42 and leave the conductor film 44 only in the trench. As a result, a part of the trench is buried with the conductive film. in this case,
It is preferable that the thickness of the conductor film 44 is formed to be equal to or longer than the Debye length.

Referring to FIG. 10, the second field insulating film 45 is oxidized or vapor-deposited to form a conductor film 4.
4 is formed. Next, a chemical mechanical polishing process or an etch back process is performed so that the second field insulating film 45 remains only in the trench, and the remaining portion of the trench is buried. As a result, the trench is filled with a stacked structure of the first field insulating film 43, the conductor film 44, and the second field insulating film 45. Here, the second field insulating film 45 can be formed of an oxide film.

Referring to FIG. 11, after etching the nitride film 42 and the oxide film 41, a gate oxide film 46 and a gate electrode 47 are sequentially formed. Finally, a junction region 48 is formed in the active region via ion implantation.

Referring again to FIG. 11, a semiconductor device according to an embodiment of the present invention includes a semiconductor substrate 4 having a trench.
0, a first field insulating film 43 formed on the side wall and lower portion of the trench, a conductive film 44 formed on the first field insulating film and partially burying the trench, and formed on the conductive film 44 The second field insulating film 45 buried in the remaining portion of the trench.

In this case, the first field insulating film 43 is
The conductor film 44 is formed of a nitride film or an oxide film.
A single crystal silicon film, a polycrystalline silicon film, an amorphous silicon film, or a combination thereof may be formed in a stacked structure. The thickness of the conductor film 44 is preferably formed to be equal to or longer than the Debye distance. Further, the second field insulating film can be formed by an oxide film.

The semiconductor device further includes a gate insulating film 46 formed on the entire structure, a gate electrode 47 formed on the gate insulating film 46, and a junction region 48 formed in the active region by ion implantation. .

A method of manufacturing a semiconductor device according to another embodiment of the present invention will be described with reference to FIGS.

Referring to FIG. 12, after an oxide film 51 and a nitride film 52 are sequentially formed on a semiconductor substrate 50, a mask (not shown) defining a plurality of field regions is formed.
Form on top. Next, the nitride film 52, the oxide film 51, and a portion of the semiconductor substrate 50 are selectively etched to form a trench in the field region, thereby forming a semiconductor structure having the trench.

Next, after removing the mask, a first field insulating film 53 is formed on the semiconductor structure through a vapor deposition process and an oxidation process. In this case, the first field insulating film 53
When the first field insulating film 53 is formed on the entire surface of the semiconductor structure, the first field insulating film 53 is formed on the entire surface of the semiconductor structure. It is formed only on the exposed portion of the substrate 50. Here, the first field insulating film 53 is
It is formed of a nitride film or an oxide film.

Referring to FIG. 13, the first field insulating film 53 is subjected to an anisotropic etching process to leave the first field insulating film 53 only on the side walls of the trench. Next, a conductor film 54 is formed on the entire structure.
The conductor film 54 can be formed in a stacked structure by using a single crystal silicon film, a polycrystalline silicon film, an amorphous silicon film, or a combination thereof.

Referring to FIG. 14, a chemical mechanical polishing step,
Alternatively, an etch-back process is performed to expose the nitride film 52 and leave the conductor film 54 only in the trench. As a result, a part of the trench is buried by the conductor film 54. In this case, the thickness of the conductor film 54 is preferably formed to be equal to or longer than the Debye distance.

Referring to FIG. 15, after a second field insulating film 55 is formed on the conductor film 54 through an oxidation process or a deposition process, a chemical mechanical polishing process or an etch-back process is performed. The field insulating film 55 is left only in the trench. After all, the trench is filled with the first field insulating film 53, the conductor film 54, and the second field insulating film 55 formed on the side wall of the trench. Here, the second
The field insulating film 55 can be formed by an oxide film.

Referring to FIG. 16, after etching the nitride film 52 and the oxide film 51, a gate oxide film 56 and a gate electrode 57 are sequentially formed on the entire structure. Finally, the joining area 5
8 are formed in the active region by ion implantation.

Referring again to FIG. 16, a semiconductor device according to another embodiment of the present invention includes a semiconductor substrate 50 having a trench, a first field insulating film 53 formed on a sidewall of the trench, and a first field insulating film. The conductive film 54 is formed on the conductive film 53 and fills a part of the trench, and the second field insulating film 55 is formed on the conductive film 54 and fills the remaining part of the trench. The thickness of the conductor film 54 is preferably formed to be equal to or longer than the Debye distance.

In this case, the first field insulating film 53
The conductor film 54 is formed of a nitride film or an oxide film.
A single crystal silicon film, a polycrystalline silicon film, an amorphous silicon film, or a combination thereof can be formed into a stacked structure. Further, the second field insulating film 55 can be formed by an oxide film.

The semiconductor device further includes a gate insulating film 56 formed on the entire structure, a gate electrode 57 formed on the gate insulating film 56, and a junction region 58 formed in the active region by ion implantation.

Unlike the conventional field oxide film embedded with only an insulating film, as shown in FIG. 11 or FIG. 16, the field oxide film according to the present invention is embedded not only with an insulating film but also with a conductor film. It is. Therefore, the effect of the electric field due to the potential difference between the semiconductor substrate and the adjacent junction region is reduced by the movement of carriers in the conductor film,
The potential increase in the depletion region adjacent to the channel region and the field region can be effectively prevented.

FIG. 17 is a simulation drawing showing a potential distribution using equipotential lines according to the distance from the center of the channel region and the depth from the surface of the semiconductor substrate in FIG. FIG. 17 shows an equipotential surface when the potential of the junction region adjacent to the channel region is higher than the potential of the semiconductor substrate. Compared to FIG. 7, it can be seen that the channel region is less susceptible to the potential change of the junction region because the interval between the equipotential lines is wide and the slope of the equipotential lines is gentle in the field region. Therefore, it is possible to prevent the device characteristics such as the threshold voltage from being changed by the potential change of the adjacent device and the junction region.

The present invention described above is not limited by the above-described embodiments and the accompanying drawings, and various substitutions and modifications may be made without departing from the scope of the technical idea of the present invention.
Modifications and alterations are apparent to those skilled in the art to which the present invention pertains.

[0043]

According to the present invention as described above, it is possible to suppress a decrease in element characteristics due to interference between adjacent elements due to a small distance between elements. In addition, since it is possible to stabilize the device characteristics while facilitating the high integration process and the development of the high integration device by alleviating the obstacle factor of the increase in the integration degree of the device, it is possible to reduce the difficulty of developing the high value-added device. As a technology, it can be used as a basic technology for manufacturing a low-cost, high-value-added semiconductor device having excellent characteristics.

[Brief description of the drawings]

FIG. 1 is a plan view showing a conventional DRAM cell structure.

FIG. 2 is a sectional view taken along line AA ′ of FIG.

FIG. 3 is a cross-sectional view at one stage of a conventional semiconductor device manufacturing process.

FIG. 4 is a cross-sectional view at one stage of a conventional semiconductor device manufacturing process.

FIG. 5 is a cross-sectional view at one stage of a conventional semiconductor device manufacturing process.

FIG. 6 is a cross-sectional view at one stage of a conventional semiconductor device manufacturing process.

FIG. 7 is a simulation drawing showing a potential distribution using an equi-potential line in FIG. 6;

FIG. 8 is a cross-sectional view at one stage of a semiconductor device manufacturing process according to an embodiment of the present invention.

FIG. 9 is a cross-sectional view at a stage of a semiconductor device manufacturing process according to an embodiment of the present invention.

FIG. 10 is a cross-sectional view illustrating a step in a semiconductor device manufacturing process according to an embodiment of the present invention.

FIG. 11 is a cross-sectional view illustrating a step in a semiconductor device manufacturing process according to an embodiment of the present invention.

FIG. 12 is a cross-sectional view illustrating a step in a semiconductor device manufacturing process according to another embodiment of the present invention.

FIG. 13 is a cross-sectional view illustrating a step in a semiconductor device manufacturing process according to another embodiment of the present invention.

FIG. 14 is a cross-sectional view illustrating a step in a semiconductor device manufacturing process according to another embodiment of the present invention.

FIG. 15 is a cross-sectional view illustrating a step in a semiconductor device manufacturing process according to another embodiment of the present invention.

FIG. 16 is a cross-sectional view illustrating a step in a semiconductor device manufacturing process according to another embodiment of the present invention.

FIG. 17 is a simulation drawing showing a potential distribution using equipotential lines in FIG. 16;

[Explanation of symbols]

 40, 50 Semiconductor substrate 41, 51 Oxide film 42, 52 Nitride film 43, 45, 53, 55 Element isolation insulation film 44, 54 Conductor film 46, 56 Gate insulation film 47, 57 Gate electrode 48, 58 Junction region

Claims (20)

[Claims] In a semiconductor device including an active region including a junction region and a channel region and a field region formed with a field oxide film for device isolation, a semiconductor structure having a trench in the field region is provided. A first step of providing, a second step of forming a first field insulating film in the trench, a third step of forming a conductor film on the first field insulating film and filling a part of the trench, Forming a second field insulating film on the conductor film and filling the remaining portion of the trench. 2. The semiconductor device according to claim 1, wherein said conductor film is made of any one of a single-crystal silicon film, a polycrystalline silicon film, and an amorphous silicon film, or a combination thereof. Forming method. 3. The method according to claim 2, wherein the conductive film has a thickness greater than a Debye distance. 4. The method according to claim 2, wherein the first field insulating film is formed of one of a nitride film and an oxide film. 5. The method of claim 4, wherein the first field insulating film is formed on sidewalls and lower portions of the trench through a deposition process. 6. The method according to claim 1, wherein the second field insulating film is an oxide film. 7. A first step of providing a semiconductor substrate, a sixth step of sequentially forming an oxide film and a nitride film on the semiconductor substrate, and a step of forming a mask defining a field region on the nitride film. Forming a trench by etching a part of the nitride film, the oxide film and the semiconductor substrate to form a trench; and removing the mask by a nine step. The method for forming a semiconductor device according to claim 4, wherein 8. The method according to claim 6, wherein the first field insulating film is formed on an exposed portion of the semiconductor substrate inside the trench by performing an oxidation process. 9. A tenth step of forming a conductive layer inside the trench and on the semiconductor structure, a third step, a chemical mechanical polishing step,
8. The method according to claim 7, further comprising the step of: exposing the oxide film by performing any one of an etch-back process and an etch-back process. 10. The fourth step includes, after the third step, a twelfth step of forming a second field insulating film on the entire structure, and one of a chemical mechanical polishing process and an etch back process. 10. The method of claim 9, further comprising: a thirteenth step of leaving the second field insulating film in a remaining portion of the trench, and a fourteenth step of etching the nitride film and the oxide film. . 11. After the fourth step, a fifteenth step of forming a gate insulating film on the entire structure, a sixteenth step of forming a gate electrode on the gate insulating film, and performing ion implantation The method according to claim 7, further comprising the step of: forming a junction region in the active region. 12. After the second step, anisotropic etching (a
2. The method according to claim 1, further comprising an eighteenth step of performing nisotropic etching so that the first field oxide film remains substantially only on sidewalls of the trench. 13. A semiconductor device including an active region including a junction region and a channel region, and a field region in which a field oxide film for element isolation is formed, wherein the semiconductor substrate has a trench in the field region. A first field insulating film formed in the trench, a conductive film filling a part of the trench, and a conductive film formed on the conductive film and filling the remaining part of the trench. Semiconductor device comprising a second field insulating film. 14. The semiconductor device according to claim 13, wherein said conductor film is made of any one of a single-crystal silicon film, a polycrystalline silicon film, and an amorphous silicon film, or a combination thereof. . 15. The method according to claim 14, wherein the conductive film has a thickness greater than a Debye distance. 16. The method according to claim 13, wherein the conductive film is formed on a sidewall of the trench. 17. The method according to claim 13, wherein the conductive film is formed on sidewalls and lower portions of the trench. 18. The semiconductor device according to claim 14, wherein the first field insulating film is formed of one of a nitride film and an oxide film. 19. The semiconductor device according to claim 13, wherein the second field insulating film is an oxide film. 20. The semiconductor device according to claim 20, further comprising a gate insulating film formed on the entire structure, a gate electrode formed on the gate insulating film, and a junction region formed in the active region by ion implantation. 14. The semiconductor device according to 13.