JP3136654B2 - Shallow trench formation method - 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 forming a shallow trench, and more particularly to a method for forming an element isolation structure by selectively removing a buried material in a flattened alignment portion by using a resist pattern. The present invention relates to a method of forming a shallow trench that can be used for forming a shallow trench.

[0002]

2. Description of the Related Art Conventionally, isolation between elements of a semiconductor device such as an IC, LSI, or VLSI is usually performed by a selective oxide film (LOCOS) formed by selectively oxidizing a surface portion of a semiconductor substrate. However, with the miniaturization and ultra-high integration of semiconductor integrated circuits, bird's beaks 12 occur in the LOCOS film 11 formed by the conventional selective oxidation method, so that the dimensional conversion difference 13 becomes large (see FIG. 3). It has become. For this reason, it is becoming difficult to cope with miniaturization of elements. Therefore, attention has been paid to a trench isolation method in which bird's beak does not occur, and therefore, a dimensional conversion difference is very small.

[0003] The trench isolation technique is disclosed in, for example, Japanese Patent Application Laid-Open No. 57-176742 or Japanese Patent Application Laid-Open No. Sho 60-5.
As disclosed in Japanese Patent No. 3045, the semiconductor substrate 1
(Groove) 2 is formed on the surface of the
Is embedded by an embedding material 3 such as a SiO ₂ insulating film by bias ECR-CVD (see FIG. 4). However, according to such a technique, as shown in FIG.
Since the alignment mark trench 4 for positioning such as mask alignment is also buried and flattened, alignment light may not be detected accurately, and there is a problem that accurate mask alignment becomes extremely difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a shallow trench is formed by selectively removing an embedding material such as an insulating film in an alignment mark portion.
It is an object of the present invention to provide a shallow trench manufacturing method capable of performing accurate alignment and thus efficiently manufacturing a ULSI by a highly reliable process.

[0005]

According to the first aspect of the present invention, a trench is formed in a surface portion of a substrate, and then the trench is formed .
A wrench is embedded with an embedding material, and then the embedding material formed outside the trench at the time of the embedding is subjected to horizontal etching with respect to the embedding material in order to increase the groove width on the trench. the filler material of the alignment portion in the trench except trench out by masking a shallow trench forming method of removing the filler material of the trenches outside and the alignment portion in the trenches, the alignment
The trench is formed so that the bottom is narrower than the opening of the groove.
The embedding material of the above-mentioned alignment portion trench leaves the side wall portion.
And is removed .

[0006] In the invention of claim 1 of the present application, the embedding material
Is preferred to be embedded by bias ECR-CVD.
It is a new thing.

In the invention of claim 1 of the present application, an oxide film such as a pad SiO ₂ film and an oxidation-resistant film such as a poly-Si film are formed on a substrate in this order, and a buried material is formed up to the oxidation-resistant film. It is preferable that the oxide film and the oxidation-resistant film are removed after the filling and the layer formed by bias ECR-CVD is projected from the substrate surface.

[0008]

According to the invention of claim 1 of the present application,
The groove shape of the alignment trench is smaller than that of the groove opening.
The bottom has a narrow shape (see FIG. 2B showing Example 2 described later).
See the example), and the embedding material of the alignment portion trench is
It is removed leaving the side wall .

As a result, according to the invention of claim 1 of the present application, for example , the inside of the alignment boundary is protected by the resist mask and removed by anisotropic etching by RIE, so that the filling material of the alignment portion trench is reduced. Side wall
By removing the portion while leaving the portion, it is possible to prevent the etching surface of the tapered portion of the alignment portion trench from being roughened by the side wall portion . That is, the alignment mark
The wrench slopes (sidewalls) can be wet etched in a short time
Can be removed, and the edge of the tapered portion of the alignment trench is removed.
Roughness of the chin surface can be prevented.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the invention according to the present application will be described below with reference to the drawings. However, needless to say, the present invention is not limited to the embodiments described below. Example 1

[0011] EXAMPLE 1 This example is a reference example, the manufacture of semiconductor devices, particularly very fine, the manufacture of integrated semiconductor integrated circuit device
In addition, a shallow trench element isolation structure and a shallow trench for mask alignment are formed.

[0012] Hereinafter, with reference to FIG. 1 (a) ~ (f) , a description will be given of an embodiment of a shallow trench forming method of the reference example.

In this embodiment, first, as shown in FIG. 1A, a pad SiO ₂ film and an etching stop film of an etch-back stopper are formed as an oxide film 5 on a Si semiconductor substrate which is a substrate 1 in this embodiment. Poly-6 as
An Si film is formed. Next, a trench 2 and an alignment portion trench 4 are formed on the surface of the semiconductor substrate 1 by anisotropic etching such as a dry etching method using RIE. Next, after performing inner wall oxidation, the bias ECR-CV
By D, as shown in FIG. 1B, the filling material 3 such as an insulating film made of SiO ₂ , the trench 2 and the alignment portion trench 4 are filled without excess or shortage. 3a is an insulating film grown outside the trench, that is, in the active region.

Next, as shown in FIG. 1C, the insulating film is etched in the horizontal direction by bias ECR-CVD under the condition that the flat surface is not etched, so that the insulating film 3 in the trench 2 is surely masked. A place necessary for forming the film 8 is secured on the trench 2 and in the vicinity thereof, that is, a margin 7 is obtained. When performing horizontal etching,
The etching conditions in the horizontal direction are set so that the deposition amount remains so that the Si substrate 1 itself is not etched, and the SiO ₂ (the SiO ₂ up to the dotted line in FIG. 1C) is removed by etching back. I do. This etch back is denoted by reference numeral 3.
Indicated by 0.

Next, as shown in FIG. 1D, the buried material 3 which is an insulating film in the trench 2 is masked with a photoresist film 8. At this time, patterning is performed so that the burying material 3 which is an insulating film in the alignment portion trench 4 is exposed. Then, as shown in FIG. 1E, both the insulating film 3a outside the trench 2 and the filling material (insulating film) 3 inside the alignment portion trench 4 are anisotropically etched by RIE using the resist film 8 as a mask. It is removed by etching. In this anisotropic etching of SiO ₂ , for example, the supply gas is CHF ₃ (75 SCCM) / O ₂ (8S
CCM), RF bias power 0.20 W / cm ² ,
It can be performed under the condition of a pressure of 0.05 Torr.
Thereafter, the resist film 8 is peeled off, and the poly-Si of the etching stop layer 6 and the pad SiO ₂ film of the oxide film 5 are removed by a usual wet etching method.

In this manner, as shown in FIG. 1F, the burying material (insulating film) 3 in the alignment portion trench 4 is completely removed without leaving the alignment portion 4 flattened. Since a structure is obtained, alignment light can be sufficiently detected, and thus accurate alignment can be performed.

Embodiment 2 This embodiment embodies the invention of claim 1 of the present application, and is similar to Embodiment 1 which is the above-described reference example, in the case of manufacturing a miniaturized semiconductor device. The present invention is embodied in forming a shallow trench for mask alignment.

FIGS. 2 (a) to 2 (f) show claims 1 of the present application.
Is a cross-sectional views sequentially showing the steps of an embodiment of a shallow trench forming method according to.

First, as shown in FIG. 2A, a pad SiO ₂ film as an oxide film 5 and a poly-Si film as an oxidation-resistant film 6 of an etch-back stopper are formed on a Si semiconductor substrate which is the substrate 1 in this embodiment. Form. Next, a trench 2 and an alignment portion trench 4 are formed on the surface of the semiconductor substrate 1 by isotropic etching such as a dry etching method using RIE. Regarding this trench formation, in the current dry etching technique, a trench having a large width is used as shown in FIG.
And, as shown in the alignment portion trench 4 of FIG. 2A, a taper is formed. That is,
The shape of the groove of the punch 4 is such that the bottom is narrower than the opening of the groove.
Become. Next, after performing inner wall oxidation, the bias ECR-C
As shown in FIG. 2B, the trench 2 and the alignment portion trench 4 are buried by VD with a burying material 3 such as an insulating film made of SiO ₂ . 3a is an insulating film grown outside the trench, that is, in the active region.

Next, as shown in FIG. 2C, the insulating film is etched in the horizontal direction by bias ECR-CVD under the condition that the flat surface is not etched, so that the insulating film 3 in the trench 2 is surely masked. A place necessary for forming the film 8 is secured on the trench 2 and in the vicinity thereof. That is, a toll margin 7 is obtained. When performing horizontal etching,
The Si substrate 1 itself Sets the horizontal etching conditions as deposited amount so as not to etch remains that amount, remove that amount of SiO ₂ (SiO ₂ up to the dotted line in FIG. 2 (c)) is etched back I do. The part for the etch back is indicated by reference numeral 30.

Next, as shown in FIG. 2D, the insulating film 3 in the trench 2 is masked with the photoresist film 8 and, at the same time, the SiO ₂ insulating film 3 of the alignment portion trench 4 is formed of SiO _{2 in} the tapered portion of the trench 4. ₂ is masked to the inside of the alignment portion trench 4 so as to protect the portion ₂ . This photoresist mask is particularly designated by reference numeral 80. This is Figure 5
As shown in (c), when removing the insulating film 3 by RIE,
Since the selectivity between the insulating film SiO ₂ and the substrate Si is not infinite, it is to prevent the etch surface of the tapered portion of the wide trench from being roughened. That is, after the formation of the resist mask, as shown in FIG. 2E, the insulating material 3a outside the trench 2 and the filling material 3 other than the tapered portion inside the alignment portion trench 4 are etched by using the resist film 8 as a mask. Are removed by performing anisotropic etching by RIE under the same conditions as in the first embodiment. This allows the alignment unit
The embedded material of the punch 4 is removed leaving the side wall portion. The embedding material remaining in the tapered portion of the alignment portion trench 4 is indicated by reference numeral 30. Next, the resist film is peeled off, and the embedding material 30 (S) remaining in the tapered portion of the alignment portion trench 4 is removed.
The iO ₂ film is removed by wet etching using HF or the like. In this case, most of the SiO ₂ is RI
The etching time can be shortened because it is removed in advance by E, so that the etched surface of the tapered portion of the trench 4 is not roughened. If the trench 4 having a tapered portion as shown in FIG. 5B is etched by conventional etching means as it is, the tapered portion becomes rough as shown in FIG. This is not shown in this example. Further, the etching stop layer 6
2 (f) is obtained by removing the poly-Si and the pad SiO ₂ film of the oxide film by the usual wet etching method.

As described above, since the insulating film 3 in the alignment portion trench 4 is completely removed by etching, alignment light can be normally detected, and accurate alignment can be performed.

[0023]

As described above, according to the first aspect of the present invention, accurate alignment can be performed.
ULSI can be efficiently manufactured by a highly reliable process. In addition, the dry etching technique for forming the shallow trench can also achieve the effect of preventing the roughness of the etched surface of the tapered portion which may occur in a wide portion.

[Brief description of the drawings]

FIG. 1 is a sectional view showing Example 1 (Reference Example) in the order of steps.

FIG. 2 is a sectional view showing Example 2 (a specific example according to the present invention) in the order of steps.

FIG. 3 is a diagram illustrating a problem of LOCOS.

FIG. 4 is a diagram showing a problem of a conventional bias ECR-CVD method.

FIG. 5 is a diagram showing a problem solved by the invention of claim 1 of the present application.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 substrate 2 trench 3 filling material (SiO ₂ ) 4 alignment portion trench 5 pad SiO ₂ film 6 poly-Si film 7 allowance 8 photoresist 30 filling material left on side wall (tapered portion)

Claims (1)

(57) [Claims] 1. A trench is formed in a surface portion of a substrate, and then the trench is filled with a filling material, and a groove width on the trench is increased by the filling material formed outside the trench at the time of filling. Etching is performed in the horizontal direction with respect to the burying material, and then the burying material in the trenches other than the alignment portion trench is masked to remove the burying material outside the trench and in the alignment portion trench. A method for forming a trench, wherein the alignment portion trench has a bottom portion which is smaller than an opening portion of the groove.
It is formed in a narrow shape, and fills the alignment section trench.
A method for forming a shallow trench, wherein the filling material is removed leaving a side wall portion .