JP2955838B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 method for forming an element isolation film using trenches in element isolation regions having different widths. The present invention relates to a method for forming an element isolation region of a semiconductor device, which is suitable for high integration by improving the flatness of an insulating film.

[0002]

2. Description of the Related Art In general, in an integrated circuit, a LOCOS method for forming a field oxide film on a field region of a silicon substrate is frequently used as one of methods for insulating the active regions of the silicon substrate from each other.

In such a general LOCOS method, a pad oxide film and a nitride film are sequentially deposited on the entire surface of a single crystal silicon substrate, and patterning is performed so that the nitride film remains only in the active region. After implanting channel stop ions into the field region using the nitride film as a mask,
A single crystal silicon substrate is heat-treated in an oxidizing atmosphere to form a field oxide film on a field region of the single crystal silicon substrate.

However, in such an integrated circuit to which the LOCOS method is applied, a bird's beak phenomenon of a field oxide film occurs in a boundary region between a field region and an active region, and the bird's beak phenomenon occurs in the active region and the bird's beak phenomenon occurs. Decrease. Furthermore, while the field oxide film is formed, the active region is reduced by the side diffusion of the channel stop ions, the junction capacitance between the active region and the diffusion layer is increased, and the junction leakage current is increased, thereby increasing the integration of the semiconductor device. There is a limit in responding to the change.

Also, since the thickness of the field oxide film depends on the size of the pattern in the isolation region, a field oxide film having a small pattern in the isolation region and a field oxide film having a large pattern in the isolation region are provided. Is formed under the same oxidation conditions, the thickness of the field oxide film having a small pattern in the isolation region becomes smaller than the thickness of the field oxide film having a large pattern in the isolation region. This is presumed to be because stress is concentrated at the edge of the pattern of the isolation region.

As another method, there is a method of forming a field oxide film in a field region by the above-described method and then implanting channel stop ions. But,
Even in such a method, the thickness of the field oxide film varies depending on the size of the pattern. Therefore, it is difficult for the field oxide film to compensate for the concentration of channel stop ions at the interface of the silicon substrate, and the insulating characteristics of the semiconductor device become unstable.

Accordingly, in order to efficiently cope with high integration of a semiconductor device, a new method for improving the insulation characteristics of a field region having a small pattern has been proposed. One of the methods is a trench isolation method in which a trench is formed in a field region of a single crystal silicon substrate to increase an effective channel length of a field transistor, thereby improving insulation characteristics of an isolation region.

This trench insulating method is a method in which a field region of a single crystal silicon substrate is anisotropically dry-etched, a trench is formed in the field region, and a polycrystalline silicon layer is buried in the trench and oxidized. Alternatively, in order to reduce the stress of the substrate due to oxidation, an insulating layer is deposited on the surface of the trench, and then the polysilicon layer is buried in the trench to oxidize the polysilicon layer.

FIG. 1 shows such a conventional trench insulating method.
It is as follows if it explains based on. As shown in FIG. 1A, an oxide film (not shown) is first formed on the entire surface of the single crystal silicon substrate 1, and then the oxide film is left in an active region by a normal photolithography and etching process. Removes an oxide film on a different field region to expose the surface of the single crystal silicon substrate 1 in that field region.

Then, the single-crystal silicon substrate 1 is anisotropically dry-etched to a predetermined depth using the oxide film left in the active region as a mask.
After the trenches 2 having different pattern sizes are formed in the field region, the oxide film is removed. Continuing, FIG.
As shown in (1), a pad oxide film 3 and a nitride film 4 are sequentially deposited on the entire surface of the single crystal silicon substrate 1 by a chemical vapor deposition method. After that, the nitride film 4 is left only on the pad oxide film 3 in the active region by a usual photolithography and etching process.

Next, the oxide film 5 is formed using a chemical vapor deposition method.
Is deposited on the nitride film 4 and the pad oxide film 3 to a thickness enough to bury the trench 2 having a small pattern. Thus, a depression is formed on the surface of the oxide film 5 on the trench 2 having a large pattern, but the surface of the oxide film 5 on the trench 2 having a small pattern is flattened. Thereafter, the photosensitive film 6 is formed only on the depression of the oxide film 5 on the trench having a large pattern by ordinary photolithography.

Next, as shown in FIG. 2C, the oxide film 5 is etched back using the photosensitive film 6 as a mask until the surface of the nitride film 4 is exposed. At this time, the oxide film 5 is completely buried in the trench of the small pattern, but the oxide film 5 partially remains in the trench of the large pattern.
As shown in FIG. 2D, after removing the photosensitive film 6, an oxide film 7 is deposited on the surfaces of the nitride film 4 and the oxide film 5 by a chemical vapor deposition method. At this time, a bent portion 8 exists on the surface of the oxide film 7.

Subsequently, a photosensitive film 9 is applied on the oxide film 7 to flatten the bent portion 8 of the oxide film 7. Next, as shown in FIG. 2E, the photosensitive film 9 and the oxide film 7 are formed.
At the same time etch back. Then, the nitride film 4 in the active region is removed, and the pad oxide film 2 is etched and the oxide films 5 and 7 are etched until the surface of the single crystal silicon substrate 1 is exposed. Therefore,
The active region and the field region of the single crystal silicon substrate 1 are actually flat.

However, when a silicon trench is formed by a conventional method, a micro-loading effect appears during etching of a narrow pattern and a wide pattern. That is, there is a problem in that a narrow trench is shallow, and a wide trench is formed deep, resulting in a difference in depth. In addition, in flattening the insulating film in the trench, a photosensitive film is formed as an auxiliary pattern and etched back to be removed, so that the etching selectivity between the photosensitive film and the insulating film must be similar. Difficult to do.

[0015]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problem, and it is an object of the present invention to provide a method of isolating a device using a trench by facilitating a trench forming step and embedding an insulating film in an insulating film filling step. It is intended to improve the flatness of the substrate.

[0016]

In order to achieve the above-mentioned object, a method of manufacturing a semiconductor device according to the present invention comprises forming a plurality of first trenches having the same width at regular intervals in each field region of a substrate. Performing a step of implanting a channel stop ion into a substrate below each of the first trenches; burying a first insulating film in each of the first trenches in a flat manner; Etching a substrate between the trenches to form a plurality of second trenches; and burying a second insulating film in the second trenches.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The present invention relates to etching of a silicon substrate in a case where the width of a trench formed in an element isolation region is not constant and different in a process of forming an element isolation region of a semiconductor device using a trench. First, regardless of the size of the isolation region, a trench having the same width is first formed, and an insulating film is buried in the trench. The second trench is formed to have a width, and an insulating film is buried in the second trench.

FIGS. 3 and 4 show a method of forming an element isolation film of a semiconductor device according to an embodiment of the present invention in the order of steps. First, as shown in FIG.
For example, an oxide film 12 of 1000 to 50 is formed thereon as an insulating film.
It is formed to a thickness of 00 angstroms. The oxide film 12 in the field region of the small pattern and the field region of the large pattern is selectively removed by a photolithography and etching process.

At this time, it is assumed that the pattern of the first field region B1 is small and the pattern of the second field region B2 is large. The active region A and the first and second field regions B1 and B2 are determined and the oxide film in the field region is removed. However, the oxide film 12 in the first field region B1 is entirely removed and the oxide film in the second field region B2 is removed. Reference numeral 12 denotes a pattern size of the first field region B1, which removes the oxide film 12 at a plurality of locations at regular intervals. Therefore,
The oxide film 12 remains in the active region A and the second region.
It remains in the field area B2. The oxide film may be removed at a plurality of locations in the first field.

Next, as shown in FIG. 3B, isotropic etching using a gas such as CH ₃ + O ₂ or anisotropic etching using a gas such as Cl ₂ or SF ₆ using the oxide film pattern as a mask. The substrate 11 exposed by
A plurality of first trenches 13 having the same width are formed in the element isolation region by etching to a depth of 000 to 5000 angstroms.

[0021] Subsequently, as shown in FIG. 2c, the oxide film 12 Pyro as a mask (H ₂ + O ₂₎ or the bottom of the trench by heat-treating the substrate at 800 to 950 ° C. in an oxidizing atmosphere such as water vapor Then, a pad oxide film 14 of 100 to 350 angstroms is formed on the inner wall. Next, channel stop ion implantation is performed using the oxide film 12 as a mask. For example, a channel stop for N- field region B, and ions such as BF ₂ 3
Ion implantation is performed at an acceleration voltage of 0 to 80 KeV and a dose of ² to 5E13 / cm ² to form a channel stop ion implantation layer in the semiconductor substrate 11 below the pad oxide film 14.

Next, as shown in FIG. 3D, the oxide film 12 and the pad oxide film 14 are removed by wet etching with a solution containing HF, or an insulating film, for example, an oxide film is directly removed without removal. After the trench is buried by being deposited on the substrate so as to be thicker than half the depth of the trench, the silicon substrate surface and the surface of the element isolation region are etched back by more than the deposition thickness so as to be horizontal. To form a first trench plug 16.

Next, as shown in FIG. 4E, after a photosensitive film 17 is applied on the substrate, the active region A and the plugs adjacent to the active region A of the first field region B1 and the second field are masked by photolithography. Then, the substrate in the other part of the second field region B2 is exposed. In the above embodiment, the photosensitive film 17 is left as described above, but may be left only in the active area and the large one field area. Alternatively, the photosensitive film may be left only in the active area.

As shown in FIG. 4F, the exposed substrate 11 is etched using the photosensitive film 17 as a mask. At this time, the first trench plug 16 in the second field region B2 also acts as a mask, and a second trench 18 having an actually equal width is formed in the second field region B2.

Next, as shown in FIG. 4g, after removing the photosensitive film, an oxide film 19, for example, is deposited as an insulating film so as to be deposited on the substrate so as to be thicker than half the depth of the second trench. And fill the trench. As shown in FIG. 4H, the second trench plug 20 is formed by etching back the oxide film 19 and flattening the surface of the silicon substrate and the surface of the element isolation region so as to be horizontal.

As a result, the first trench plug 16 buried in the trench of the first field region B1 which is relatively narrow
And a second field region B2 having a large proportion
An element isolation film composed of the first trench plug 16 and the second trench plug 20 embedded in the trench is formed.

Next, a method for forming an isolation film of a semiconductor device according to another embodiment of the present invention will be described with reference to FIG.
After performing the steps up to FIG.
Then, as shown in FIG. 5A, a pad oxide film 21 was formed on the entire surface of the substrate by forming an oxide film, for example, to a thickness of 100 to 500 Å by a thermal oxidation method or a vapor deposition method as an insulating film. Thereafter, a fluid oxide film is formed thereon as a fluid insulating film 22 to a thickness enough to fill the second trench 18 sufficiently.

Next, as shown in FIG. 5B, the fluid insulating film 22 is formed in an inert atmosphere containing N ₂ or Ar gas or Pyro (H ₂ + O ₂ ) or an oxidizing atmosphere such as steam or O _2. After heat treatment at 600 ° C. or more to make the surface bend gently flow, it is etched back and flattened so that the surface of the silicon substrate and the surface of the element isolation region are horizontal. An element isolation film composed of the first trench plug 16 embedded in the trench B1 and an element isolation film composed of the first trench plug 16 embedded in the trench of the second field region B2 and the fluid insulating film 22 having a large proportion are formed. I do.

[0029]

As described above, the present invention provides a micro-loading effect by forming a trench with the same width regardless of the size of the element isolation region during the substrate etching process for forming the trench in the element isolation region. Can be prevented, and the uniformity and reproducibility of the process can be improved. In addition, in the process of burying the insulating film in the trench and flattening, the microloading effect can be prevented by burying the insulating film by a consistent process of depositing and etching back the insulating film in the trench of the same width actually, Process uniformity and reproducibility can be improved.

[Brief description of the drawings]

FIG. 1 is a process sequence diagram showing a method for forming an element isolation film of a conventional semiconductor device.

FIG. 2 is a process sequence diagram showing a conventional method for forming an element isolation film of a semiconductor device.

FIG. 3 is a process sequence diagram illustrating a method for forming an element isolation film according to the first embodiment of the present invention.

FIG. 4 is a process sequence diagram illustrating a method for forming an element isolation film according to the first embodiment of the present invention.

FIG. 5 is a process sequence diagram showing a method for forming an element isolation film according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Semiconductor substrate 12, 19 Oxide film 13 First trench 14, 21 Pad oxide film 15 Channel stop ion implantation layer 16 First trench plug 17 Photosensitive film 18 Second trench 20 Second trench plug 22 Fluid insulating film A Active area B1 Element isolation region with a narrower ratio B2 Element isolation region with a wider ratio

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/76

Claims (3)

(57) [Claims] A first field region having a narrow width;
The method of manufacturing a semiconductor device for forming a field insulating film on the second field region has a width, a first trench that having a same width as the first field region, one formed in the first field region And the second
Forming two or more in the two-field region ; implanting channel stop ions into a substrate below each of the first trenches; burying a first insulating film in each of the first trenches flat; The first insulating film is formed in a second field region
Forming a first plurality of second trenches substrate is etched during the trench that is, forming a second insulating film on the entire surface of the substrate, wherein as the second trenches are filled The second insulation
Forming a flowable insulating film on the film, heat treating the flowable insulating film, etching back the flowable insulating film to form a surface of the substrate;
Flattening to the same height . 2. The step of forming the first trench includes forming an insulating film on a semiconductor substrate, leaving the insulating film on the entire surface of the active region, and leaving the insulating film at a constant width and a constant interval in the field region. 2. The method of claim 1, further comprising: patterning the insulating film; and etching the exposed substrate to a predetermined depth using the patterned insulating film as a mask. 3. The step of forming the second trench includes forming a mask over an active region, and exposing the mask using the mask and a first insulating layer embedded in the first trench as a mask. And etching the substrate portion.