KR20020057532A - Method of fabricating a structure of silicon wafer using wet etching - Google Patents

Abstract

PURPOSE: A method for fabricating a structure of a silicon wafer by a wet etch method is provided to form a structure having complicated shape or various etch depths through a simple and inexpensive method, by using an etch barrier pattern which disappears just before the etch process is finished or at the time to finish the etch process. CONSTITUTION: The etch barrier pattern is formed in a predetermined region on an etch region of the silicon wafer so that the shape of the structure is varied and the (111) surface of the structure having a protruded convex corner is not corroded. The silicon wafer is exposed to an etch solution to etch the silicon wafer.

Description

Method of fabricating a structure of silicon wafer using wet etching}

The present invention relates to a method for manufacturing a structure of a silicon wafer using wet etching, and to easily prepare a structure having a complex shape by using an etching prevention pattern, and to provide a wet etching method for manufacturing a structure having various etching depths in one process. It relates to a method for manufacturing a structure of a used silicon wafer.

Silicon is widely used as a basic material in various fields including the semiconductor field due to its electrical characteristics. In particular, various shapes of structures may be formed by using silicon wet etching, which may obtain an etching surface having a special angle by using an etching selectivity between (100) and (111) surfaces of a silicon wafer having a growth axis of 100. In recent years, the use of silicon is also widely used in the field of micro machining (Micro Elecro-Mechanical Systems, MEMS) and optical devices (Optic devices).

The wet etching of silicon has a fast etching speed and the surface roughness (Ra) of the etching surface is controlled up to several nm (10 ^-9 m), and it is possible to form a special angle etching surface due to the crystal structure of silicon. It is very wide and uses the etch ratio of each crystal plane, so it is easy to etch a simple rectangular shape or deep depth. However, the process is very complicated to produce structures with complex shapes or varying depths. In general, a structure in which convex corners are formed is formed using a compensation pattern, and structures having various depths are formed by performing a plurality of repeated processes.

1 is a schematic view showing a wet etching process of a conventional silicon wafer, (a) of Figure 1 is a wet etching so that the etch width is different, Figure 1 (b) is a wet etching so that each etching depth is different will be. In this case, the bottom surface etched in FIGS. 1 to 7 is a (100) plane, the inclined side is a (111) plane, and an arrow indicates the progress of the process.

The wet etching of the silicon wafer is performed by depositing an etching mask, such as SiO ₂ or SiNx, on the (100) surface of the silicon wafer, removing a mask having a predetermined width for wet etching, and then exposing the silicon wafer to an etchant.

Referring to (a) of FIG. 1, when wet etching a silicon wafer, the (100) plane is etched at a high speed, and the (111) plane is etched very slowly. The etching rate of the (111) plane is about 10 to 100 times the difference occurs. Therefore, since the etching mask is removed less, in the region A having less exposure to the etching liquid, the etching surface consisting of the (111) plane forms a strong etching-stop wall to form a V-groove. Therefore, although etching is not continuously performed in the depth direction, etching in the depth direction is continuously performed by etching the (100) plane in the region B where the etchant is exposed.

Referring to FIG. 1B, when the structure is formed to have various depths, the etching process of the etching mask and the etching process of the silicon wafer should be repeated. Although not shown, a photoresist pattern which is usually used as an etching prevention layer is illustrated. The process is run several times.

FIG. 2 is a schematic diagram for explaining convex corners and concave corner corners in a structure manufactured by wet etching of a silicon wafer. FIG.

Referring to FIG. 2, when the crossing angles formed by the etch planes formed by the (111) planes cross each other are viewed from the top, the corner C, which is 90 degrees, is a concave corner, and the intersection angle is 270 degrees ( D) is a convex corner.

FIG. 3 is a schematic diagram for describing a phenomenon of etching at the convex corner and the concave corner when the wet etching process for manufacturing the structure of FIG. 2 is performed. In FIG. 3, the thick solid line is the (111) plane, and the small square is the silicon atom existing on the (111) plane.

Referring to FIG. 3, on the (111) plane of the silicon wafer, as shown in (a) of FIG. 3, an atomic layer is not etched one by one, but a kink etched while being skewed as shown in (b) of FIG. 3 appears. The reason is that deposition and etching are theoretically performed with less energy in the deposition and etching mechanisms where atoms are attached or vice versa.

Referring to (c) of FIG. 3, in the concave corner, although new crystal planes are formed by connecting the kinks indicated by the dotted lines, the etching progresses continuously to prevent the (111) plane from being etched. The corner C by continually exists.

However, referring to (d) of FIG. 3, in the convex corner, new crystal planes, which are also indicated by dotted lines connecting the kinks, are etched at a high speed to continuously erode the etch barrier of the (111) plane. That is, when wet etching a silicon structure, the wet etching proceeds in the convex corner, and thus the corner (D) due to the intersection of the (111) planes cannot be maintained due to the etching of the etchant unlike the intended. . Therefore, in order to maintain the convex corner in a desired shape, a compensation pattern is generally formed in the etching mask to reinforce the convex corner.

FIG. 4 is a schematic diagram illustrating an etching process when wet etching is performed after forming a compensation pattern.

Referring to FIG. 4, in order to maintain the convex corner in a desired shape, an effect of reinforcing the convex corner is obtained by additionally forming a compensation pattern on the etching mask.

However, in the case of using the compensation pattern, since the shape of the compensation pattern is changed when the model of the structure is changed, it is necessary to go through the process of finding the optimal compensation pattern through simulation in advance. The use of compensation patterns becomes difficult.

In particular, even when fabricating a structure having a complex shape having various depths as shown in (b) of FIG. 1, an optimum compensation pattern must also be found by using simulation, and thus, expensive silicon wafer wet etching simulation software must be used. There is a problem such as undergoing trial and error, repeating the etching process.

Accordingly, the present invention provides a method for manufacturing a structure of a silicon wafer using wet etching, which can produce a structure having a complex shape or various etching depths simply and inexpensively without undergoing various processes or repetitive processes.

1 is a schematic view showing a wet etching process of a conventional silicon wafer;

2 is a schematic diagram illustrating convex and concave corners in structures fabricated by wet etching of a silicon wafer;

3 is a schematic view for explaining a phenomenon of etching in the convex corner and concave corner when the wet etching process for manufacturing the structure of FIG.

4 is a schematic diagram illustrating an etching process when wet etching is performed after forming a compensation pattern;

5 is a schematic view comparing a conventional wet etching process and a wet etching process according to the present invention;

Figure 6 is a schematic diagram showing an example of applying an anti-etching pattern according to the present invention to produce a structure having a different etching depth, respectively; And

7 is a schematic diagram for comparing a structure manufactured by a conventional wet etching process and a structure manufactured by a wet etching process according to the present invention.

In the method of manufacturing a structure of a silicon wafer using the wet etching of the present invention for achieving the above technical problem, the shape of the structure, the silicon so that the (111) surface of the structure having a protruding convex corner is prevented from being eroded The silicon wafer may be etched by forming an anti-etching pattern in a predetermined area on the region to be etched and then exposing the silicon wafer to an etchant.

In this case, it is preferable to form the etch stop pattern so that the etch stop pattern disappears at least until the end of the etching process.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 5 is a schematic view comparing a conventional wet etching process and a wet etching process according to the present invention. FIG. 5A is a schematic diagram illustrating an etching process when wet etching is performed by forming only an etching mask, and FIG. 5. (B) is schematic diagrams showing the etching progress when the etching prevention pattern is formed and then wet etching.

Referring to FIG. 5A, while the wet etching is performed, the (100) surface is rapidly etched and deeply etched downward, but the (111) surface is very slowly etched and slightly under the etching mask. Under Cut is showing.

However, referring to FIG. 5B, since the (100) plane is rapidly etched between the etch stop patterns but the (111) plane is slow, the V-shaped groove is formed and the etching is stopped in the depth direction. Therefore, the etching depth in the case of etching using the etching prevention pattern is lower than the etching depth in the case of etching using only the etching mask. At this time, although the speed is slow as time passes, as the etching of the (111) plane proceeds, the etch stop pattern gradually decreases, and eventually the etch stop pattern is lost due to the penetration of the etchant. On the other hand, the material of the etching prevention pattern may be the same as or different from the etching mask.

Here, in the case where the shape of the etch stop pattern is linear, the width W _p of the etch stop pattern for removing the etch stop pattern immediately before or after the etch stop is equal to the etch rate of the (100) plane and the (111) plane. It is determined by Equation 1 to be described later using the ratio.

Here, W _p is the width of the etching prevention pattern, R ₁₁₁ is the etching speed of the (111) plane, R ₁₀₀ is the etching speed of the (100) plane, D is the final etching depth according to the etching process using only the conventional etching mask, h is the depth of the V-shaped groove formed when the etching prevention pattern is formed and then etched, and α is a process variable and changes depending on the process temperature, the type of etchant, the concentration of the etchant, and the like.

In Equation 1, Is the etch width of the (111) plane during the wet etching process, and multiply by 2 is because the (111) plane is etched on both sides of the etch stop pattern. Therefore, if the first term on the right side is defined as the width of the etch stop pattern, it will be in the form of a sharp mountain, that is, a V-shaped groove. In the wet etching process using the present invention, it takes a certain time to completely disappear the traces of the etching prevention pattern. However, since the required time takes longer as the depth of the V-shaped groove formed by the etch stop pattern is deeper, the width of the etch stop pattern should be reduced by (α × h).

For example, assuming that the etching ratio between the (100) plane and the (111) plane is 70: 1 and the etching depth of the (100) plane is 140 μm, the (100) plane is etched to a depth of 140 μm during the (111) plane. ) The surface is etched 2㎛. Therefore, the width of the etch stop pattern in this case is determined to be 4 μm or less, that is, 4 μm− (α × h).

6 is a schematic diagram illustrating an example of applying an etch stop pattern according to the present invention to produce a structure having a different etching depth.

Referring to FIG. 6, in the case of forming structures having different etching depths, in the region E having the lowest etching depth, the gap F between the etching prevention patterns is narrowed to form a densely formed region, and the etching depth is medium. ), The gap x 'between the etch stop patterns is formed by slightly increasing the gap between the etch stop patterns than the region E having the lowest etch depth. This is because the narrower the interval (x or x ') between the etch stop patterns, the smaller the V-groove is formed, and as a result, the etch depth is lower. At this time, the interval x 'between the etch stop patterns for forming the etch depth to the middle should be smaller than the gap x ″ formed in the region G formed only of the etch mask without the etch stop pattern.

As such, by adjusting the depth of etching using the interval of the etch stop pattern, a complicated structure having different heights of etching may be manufactured by only one wet etching.

7 is a schematic diagram for comparing a structure manufactured by a conventional wet etching process and a structure manufactured by a wet etching process according to the present invention.

In Figure 7 (a) is the shape of the structure to be manufactured, (b) is a wet etching by forming only the pattern of the etching mask in order to manufacture the structure of (a) and (c) is the etching mask pattern of (b) And wet etching by forming a compensation pattern, and (d) is a wet etching by forming an etching mask pattern of (b) and an etching prevention pattern according to an embodiment of the present invention.

Referring to Figure 7 (a), there is a protruding convex corner in the structure.

Referring to the structure formed by (b) of Figure 7, it can be seen that the protruding convex corner of Figure 6 (a) is not manufactured in the form to be prepared due to the penetration of the etchant. In addition, referring to FIG. 7C, when the compensation pattern is simulated, a shape of the structure may be obtained to a certain degree, but a lot of trial and error may be required to obtain an optimal compensation pattern.

However, according to FIG. 7D, it can be seen that the structure having the same shape as that of FIG. 7A is manufactured by using the etching prevention pattern.

As described above, according to the method of fabricating a silicon wafer using wet etching, the etching prevention pattern disappears immediately before or after the end of the etching process, thereby simplifying and inexpensively without undergoing various processes or repetitive processes. Structures with complex shapes or various etching depths can be produced.

In addition, by accurately implementing the shape of the structure to be manufactured can improve the reliability of the various devices using the silicon structure.

The present invention is not limited to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

Claims (4)

A method of fabricating a structure of a silicon wafer using wet etching; By varying the shape of the structure, and forming an anti-etching pattern in a predetermined area on the area to be etched of the silicon wafer to prevent erosion of the (111) surface of the structure having a protruding convex corner, and then the silicon wafer Method for producing a structure of a silicon wafer using wet etching, characterized in that for etching the silicon wafer by exposure to an etchant. The method of claim 1, wherein the etching prevention pattern is formed such that the etching prevention pattern disappears at least until the end of the etching process. 3. The width of the etch stop pattern when the etch stop pattern is linear. Method for producing a structure of a silicon wafer using a wet etching, characterized in that calculated by. Here, Wp is the width of the etching prevention pattern, R ₁₁₁ is the etching speed of the (111) plane, R ₁₀₀ is the etching speed of the (100) plane, D is the final etching depth according to the conventional etching process, h is the etching prevention The depth of the V-groove formed when the pattern is formed and then etched, α is a process variable. The wet etching method of claim 1, wherein a plurality of the etch stop patterns are formed, and when the etch depth of the structure is low, the spacing between the etch stop patterns is narrower than when the etch depth of the structure is high. Structure manufacturing method of silicon wafer using etching.