JPH11312661A - Formation of high aspect ratio trench - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a high aspect ratio trench, which forms the trench structure having a very high aspect ratio in substrate processing in a free shape. SOLUTION: A step difference 3 is formed in substrate 1. A mask 2, having the material with the etching rate which is different from the etching rate of the substrate 1 is formed as a film on the entire surface, including a step difference 3 of the substrate 1 on which the step difference 3 is formed. The film of the material equivalent to the substrate 1 with regard to the etching rate is formed and filled in the step difference 3, wherein the film of the mask 2 is formed, and a film 4 is formed. The substrate 1 is polished from the surface, and the film 4 and the mask 2 at the uppermost layer are removed. Thus, the surface of the substrate 1 is expoased. The mask 2 is etched tot he required depth and removed.

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 trench having a high aspect ratio, and more particularly to a method for forming a trench having a very high aspect ratio in a substrate in a free form in processing a substrate.

[0002]

2. Description of the Related Art A conventional example of a trench forming method will be described with reference to FIG. An etching technique is used in the conventional trench formation shown in FIG. The trench etching in this case employs a reactive ion etching (RIE) technique or an inductive coupling plasma (ICP) technique, and the wet etching uses silicon (11).
0) Adopt vertical anisotropic etching with a KOH aqueous solution using a substrate. Hereinafter, a specific description will be given.

Referring to FIG. 3A, reference numeral 1 denotes a trench 1
1 shows a cross section of the substrate on which to be formed. In this case, a silicon substrate is used as the substrate 1. FIG. 3B shows a state where a mask indicated by reference numeral 2 is formed on the surface of the silicon substrate 1 in FIG. 3A. As shown in FIG. 3C, the silicon substrate 1 on which the mask 2 shown in FIG. 3B is formed has a portion corresponding to the width of the trench 11 where the trench 11 is to be formed. Is removed to expose the etching region 21. By performing an etching process on the silicon substrate 1 in this state, the trench 11 is formed.
The etching progresses from the etching region 21 exposed by removing the mask 2 to be formed, and the trench 11 can be formed. In this case, since silicon is used as the substrate material and the mask material is silicon oxide whose surface is oxidized, the mask processing of the silicon oxide mask 2 can be performed by applying photolithography technology.

The silicon substrate 1 is etched by employing the above-described RIE technique or ICP technique as dry etching, and employing a KOH aqueous solution as a wet method.

[0005]

When the dry etching technique is employed in the above-described trench 11 etching technique for the silicon substrate 1, there is a limit to the ratio of the depth to the width of the trench 11, that is, the aspect ratio. The limit is 40: 1, and it is difficult to make it larger. When wet etching is adopted, the shape of the trench 11 to be formed is restricted, and the trench 11 having a free planar shape cannot be formed.

SUMMARY OF THE INVENTION The present invention provides a method for forming a high aspect ratio trench capable of forming a trench having a high aspect ratio with a free planar shape and solving the above-mentioned problem.

[0007]

Means for Solving the Problems Claim 1: A step 2 formed on a substrate 1 and a mask 2 made of a material having an etching rate different from the etching rate of the substrate 1 on the entire surface including the step 3 of the substrate 1 on which the step 3 is formed. Is formed, and a film 4 of a material equivalent to the substrate 1 with respect to an etching rate is formed and filled in the step 3 on which the mask 2 is formed, and the uppermost film 4 and the mask 2 are removed to remove the surface of the substrate 1. A method for forming a trench having a high aspect ratio in which the mask 2 is exposed and etched to a desired depth and removed is configured.

Claim 2: In the method for forming a high aspect ratio trench according to claim 1, prior to filling the film 4 of a material equivalent to the substrate 1 with respect to the etching rate into the step 3, the step 3 is formed. The method for forming a high aspect ratio trench for removing the mask 2 formed at the bottom of the trench was constructed. Further, in the third aspect of the present invention, a high aspect ratio trench forming method is provided in which the mask 2 is entirely removed.

Further, claim 4: claims 1 to 3
In the method for forming a high aspect ratio trench described in any one of the above, a high aspect ratio trench forming method in which the substrate 1 is formed of a silicon substrate is provided. In a fifth aspect of the present invention, in the method of forming a high aspect ratio trench, the mask 2 comprises a high aspect ratio trench forming method comprising silicon oxide.

[0010] Claim 6: Claims 4 and 5
In the method for forming a high aspect ratio trench described in any one of the above, the film 4 constitutes a method for forming a high aspect ratio trench formed of silicon, particularly polycrystalline silicon.

[0011]

An embodiment of the present invention will be described with reference to FIG. (Step 1) Referring to FIG. 1A, a substrate 1 having a step indicated by 3 is prepared as a substrate. That is, the prepared substrate 1 is subjected to a vertical dry etching process, and the step 3 is formed by forming a groove having a required width from the surface thereof to a required depth. The step 3 has a depth of, for example, 200 μm and a width of 20 μm. Preferably, a silicon substrate is used as the substrate 1.

(Step 2) Referring to FIG. 1B, FIG.
A thin film of the mask 2 is formed on the entire surface including the step 3 of the substrate 1 having the step 3 in FIG.
In this case, as a material for forming the mask 2, a specific etching solution or etching gas used is used.
A material whose etching rate is significantly different from the etching rate of the substrate 1 is selected. In this embodiment, the mask 2 is filled to a thickness of 1 μm. When a silicon substrate is used as the substrate 1, the mask 2 is made of silicon oxide.

(Step 3) Referring to FIG. 1C, a photolithography technique is applied to the substrate 1 to remove the mask 2 formed on the bottom of the step 3. (Step 4) Referring to FIG. 1D, the mask 2
In particular, a film 4 of the same material as that of the substrate 1 is formed and filled between the thin film surfaces in the step 3 by a low pressure CVD apparatus. Alternatively, in general, a material equivalent to the material constituting the substrate 1 with respect to the etching rate is selected as the material constituting the film 4, and the film is filled. When the substrate 1 is a silicon substrate, the film 4 is filled with polycrystalline silicon to a thickness of 10 μm.

(Step 5) Referring to FIG. 1E, the surface of the substrate 1 is covered with a mask 2, and a film 4 is covered thereon as an uppermost layer. Here, the substrate 1 in this state is polished from the surface to remove the uppermost film 4 and the mask 2, thereby exposing the surface of the substrate 1. FIG. 1E shows a state where the surface of the substrate 1 is exposed.

When the substrate 1 is a silicon substrate, the surface of the silicon substrate 1 is exposed by polishing the surface of the silicon substrate 1 to remove the uppermost film 4 and the mask 2 of silicon oxide. (Step 6) Referring to FIG. 1 (f), finally, an etching solution or an etching gas for selectively etching only the mask 2 with respect to the substrate 1 and the film 4 in the step 3 connected thereto. Is applied, and the mask 2 is etched to a desired depth and removed. FIG. 1F shows a state where the mask 2 is entirely removed by etching. When the substrate 1 is a silicon substrate, an aqueous solution of hydrogen fluoride is used as an etchant, and the substrate 1 is impregnated with the aqueous solution of hydrogen fluoride and selectively etched, so that a high aspect ratio 200 having a width of 1 μm and a depth of 200 μm is eventually obtained. : 1 trench 11 is formed.
FIG. 1G is a perspective view of the silicon substrate 1 in which the trench 11 having a high aspect ratio is formed.

In the embodiment shown in FIG. 1, when the substrate 1 is made of a silicon substrate, the entire structure of the trench 11 can be made of the same material, which is suitable for achieving electrical conduction. Also, the trench 11 is formed only by the first substrate processing.
Can be determined, and there is no restriction on the formation of the depth. In the above embodiment, in step 3, step 3
After removing the mask 2 formed on the bottom of the film, a film 4 was formed in step 4, and the substrate 1 and the film 4 were mechanically bonded to each other. When the substrate 1 is formed of a silicon substrate, the substrate 1 and the film 4 are electrically coupled by this. here,
Referring to FIG. 2, when Step 4 and subsequent steps are performed in a state where Step 3 is omitted and the mask 2 is formed at the bottom of the step 3, a trench-formed silicon substrate in which the substrate 1 and the thick film 4 are not electrically coupled is formed. 1 is configured.

[0017]

As described above, according to the present invention, a free plane can be obtained by using a selective etching technique capable of deeply digging a narrow gap and a substrate processing technique having a high patterning property. A trench having a very high aspect ratio can be formed. And the depth of the trench can be determined only by the first substrate processing,
There is no restriction on the depth formation. In addition, the width of the trench is controlled by the film thickness of a substance having a higher etching rate than that of the substrate, and various methods having high patterning properties are used to form a step on the substrate that determines the final trench pattern. Therefore, a trench having a free plane shape and a high aspect ratio can be formed. Further, when the substrate is formed of a silicon substrate, the entire trench structure can be formed of the same material, which is suitable for achieving electrical conduction.

[Brief description of the drawings]

FIG. 1 illustrates an embodiment.

FIG. 2 is a diagram illustrating another embodiment.

FIG. 3 illustrates a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 11 Trench 2 Mask 21 Etching area 3 Step 4 Film

Claims (6)

[Claims] 1. A step is formed on a substrate, and a mask made of a material having an etching rate different from the etching rate of the substrate is formed on the entire surface including the step of the substrate having the step formed therein. A high aspect ratio film is formed by filling a film of a material equivalent to a substrate with respect to an etching rate, removing a top layer film and a mask to expose a substrate surface, and etching and removing the mask to a desired depth. Specific trench forming method. 2. A method for forming a trench having a high aspect ratio according to claim 1, wherein a mask formed at the bottom of the step is filled with a film of a material equivalent to a substrate with respect to an etching rate. A method for forming a high aspect ratio trench, characterized by removing the trench. 3. The method of forming a high aspect ratio trench according to claim 1, wherein the mask is entirely removed. 4. The method of forming a high aspect ratio trench according to claim 1, wherein the substrate is formed of a silicon substrate. Method. 5. The method for forming a high aspect ratio trench according to claim 4, wherein the mask is made of silicon oxide. 6. The method for forming a high aspect ratio trench according to claim 4, wherein the film is made of silicon, particularly polycrystalline silicon. .