JP2009269120A - Silicon structure manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon structure manufacturing structure for easily forming a recess of a high aspect ratio, which has a step formed therein, with high precision. <P>SOLUTION: The silicon structure manufacturing method has: a mask pattern forming step of forming a mask pattern 2 having formed therein a plurality of opening portions 21a to 21f, 22 different in dimension W or shape; an etching step of simultaneously performing anisotropic dry etching of a base material 1 exposed to the opening portions 21a to 21f, 22, in depth directions d1, d2 to form initial recesses 11, 12 having the mutually different depths d1, d2; an oxidized portion forming step of oxidizing internal surfaces of the initial recesses 11, 12, and oxidizing the whole of the base material 1 left as partitions 1w between the initial recesses 11, 12, to thereby form oxidized portions; and an oxidized portion removing step of removing the oxidized portions to form the recess 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a silicon structure.

Conventionally, a device (Micro Electro Mechanical System: MEMS) having a new function by fusing micro mechanical parts and electronic parts is known. In MEMS, products for the market such as automobile parts (airbag sensors, etc.), inkjet heads, image projection devices, etc. are mass-produced mainly by forming minute mechanical structures on silicon (Si) wafers. . In MEMS, there is a demand for further miniaturization and higher performance of these devices.
For example, a mechanical detection unit of an acceleration sensor or an angular velocity sensor is mainly composed of a comb-like beam structure formed on a substrate. To reduce the size and performance of these sensors, increase the width of the groove formed by etching the Si substrate and the aspect ratio (depth / groove width, depth / hole diameter) between the hole diameter and depth. There is a need to.

As a method for forming a hole or groove having a high aspect ratio by etching on a Si substrate, a method of switching a material gas supplied to a chamber for each etching process is disclosed (for example, see Patent Document 1). Patent Document 1 discloses a dry etching technique in which two steps of (1) plasma etching with high anisotropy and (2) polymer-based thin film deposition are alternately performed.
US Pat. No. 5,501,893

However, in the conventional technique, when forming a multi-stage groove (trench) having a high aspect ratio, a multi-stage hole (hole), or a multi-stage structure in which a trench and a hole are combined, the following is performed. There are challenges. With the conventional technique, it is extremely difficult to adjust the balance between the etching process (1) and the thin film deposition process (2). Therefore, the adjustment range (process margin) of various parameters in the manufacturing process becomes very narrow, and optimization of the manufacturing process becomes extremely difficult.
For example, when forming recesses such as holes and trenches by etching on a Si base material, the depth from the surface of the base material is formed when a bottom surface having a different depth is formed to form a step inside the recess. If they are different, the amount of reaching radicals and ions will be different. Therefore, the etching rate in the step (1) and the amount of the polymer-based thin film deposited in the step (2) vary depending on the location (position in the depth direction), and the optimum amount for the deep position in the depth direction of the recess. It is extremely difficult to deposit a thin film.

Further, the inventors have found that the following problems occur when forming the step of such a recess.
When the film thickness of the thin film deposited on the inner surface of the recess in the step (2) is too thin, the side wall of the portion is formed in a tapered shape in the step (1). On the other hand, when the thickness of the thin film deposited in the step (2) is too thick, the base material remains in a protruding shape at the step of the recess. In addition, when the bottom surface of the deepest part of the recess becomes rough in the process (1), the thin film is uniformly formed in the vicinity of the corner of the deepest part of the recess when the thin film is deposited in the process (2). It is not deposited, and the inner surface of the recess is also roughened in the step (1).
Therefore, with the conventional method, it is difficult to form a step with high processing accuracy in a high aspect ratio recess.

  Therefore, the present invention provides a method for manufacturing a silicon structure, which can easily form a high aspect ratio recess having a step inside with high processing accuracy.

  In order to solve the above-described problems, a method for manufacturing a silicon structure according to the present invention is a method for manufacturing a silicon structure in which a concave portion having a step in the depth direction is formed inside a base material made of silicon. A mask pattern forming step of forming a mask pattern having a plurality of openings having different dimensions or shapes, and anisotropic dry etching the substrate exposed in the plurality of openings simultaneously in the depth direction, An etching process for forming a plurality of initial recesses having different depths and oxidizing the inner surface of the plurality of initial recesses oxidizes the entire substrate remaining as a partition between each of the initial recesses. It has the oxidation part formation process which forms an oxidation part, and the oxidation part removal process which removes the said oxidation part and forms the said recessed part, It is characterized by the above-mentioned.

By manufacturing in this way, in an etching process, each initial stage recessed part from which the dimension or shape of an opening part differs in a base material is etched with a different etching rate. Thereby, the initial recess is formed at a plurality of different depths. At this time, each initial recess is formed in a state in which the base material constituting the inner surface of each initial recess remains as a partition wall separating the initial recesses between the initial recesses. In the oxidized portion forming step, the inner surface of each initial recess and the partition wall remaining between each initial recess are oxidized to become an oxidized portion. Further, the oxidized portion is removed in the oxidized portion removing step, and the entire shape of the concave portion is formed. As a result, the inner surface of the recess is smoothed, the partition between the initial recesses having different depths is removed, and one or more steps in the depth direction are formed inside the recess.
Therefore, according to the silicon structure manufacturing method of the present invention, a high aspect ratio recess having a step inside can be easily formed with high processing accuracy.

  In the method for manufacturing a silicon structure according to the present invention, the depth of the initial recess is controlled in the etching step by adjusting the size or the shape of the opening in the mask pattern forming step. And

By manufacturing in this way, the etching rate of the substrate can be increased by increasing the size of the opening of the initial recess in the etching process. Moreover, the dimension of the opening part of an initial recessed part can be made small, and the etching rate of a base material can be reduced. Further, the etching rate of the substrate can be adjusted by adjusting the shape of the opening of the initial recess.
Therefore, by adjusting the size or shape of the opening of the mask pattern to adjust the etching rate of each initial recess, and by controlling the depth of each initial recess, a step with a desired size and shape is increased inside the recess. It can be formed with high accuracy.

  In the method of manufacturing a silicon structure according to the present invention, the thickness of the partition between the initial recesses may be formed in the etching step by adjusting the interval between the openings in the mask pattern forming step. The thickness is adjusted to be completely oxidized in the process.

  By manufacturing in this way, the whole partition left between the initial recesses in the oxidized portion removing step can be oxidized and removed more reliably and easily.

  The method for manufacturing a silicon structure according to the present invention is characterized in that in the mask pattern forming step, the dimensions and shapes of a plurality of adjacent openings are formed uniformly.

  By manufacturing in this way, the depth of a plurality of adjacent initial recesses is formed uniformly. Then, by removing the partition between these initial recesses in the oxidation portion removing step, the bottom surface of the recess can be formed in a desired size and shape.

  Further, in the method of manufacturing a silicon structure according to the present invention, in the etching step, the opening located on the outermost side in the plan view among the plurality of openings is configured such that the base is the oxidation part. The thickness removed in the removing step is formed inside the recess rather than the inner surface of the recess.

  By manufacturing in this way, the base material on the inner surface of the initial recess is oxidized to the boundary of the region where the final recess is formed to become an oxidized portion. The oxidized portion is removed in the oxidized portion removing step. Therefore, the inner surface, the width dimension, the diameter dimension, etc. of the recess can be processed with high processing accuracy.

  Further, in the method for manufacturing a silicon structure according to the present invention, the depth of the initial concave portion is adjusted as the oxidized portion by adjusting the size or the shape of the opening in the mask pattern forming step. It is characterized in that it is formed shallower than the depth of the recess by the thickness removed in the oxidation part removing step.

  By manufacturing in this way, the base material on the bottom surface of the initial concave portion is oxidized to the boundary of the region where the final concave portion is formed to become an oxidized portion. The oxidized portion is removed in the oxidized portion removing step. Therefore, the bottom surface, depth, and the like of the recess can be processed with high processing accuracy.

  The method for manufacturing a silicon structure according to the present invention is characterized in that, in the mask pattern forming step, the shape of the opening is a groove shape or a hole shape.

  By manufacturing in this way, the groove-shaped initial recess and the hole-shaped initial recess can be formed at different depths in the etching step. Moreover, the width dimension of each opening part of a groove-shaped initial stage recessed part can be varied, and these can be formed in a different depth. Further, the diameters of the openings of the hole-shaped initial recesses can be made different to form them at different depths.

  The method for producing a silicon structure according to the present invention is characterized in that the oxidized portion forming step is performed by thermal oxidation by heating.

  By manufacturing in this way, the thickness of the oxidized portion on the inner surface of the initial recess can be made uniform. Further, the thickness of the oxidized portion can be controlled by adjusting the heating temperature, the heating time, and the like.

  The method for manufacturing a silicon structure according to the present invention is characterized in that the oxidized portion removing step is performed by wet etching.

  By manufacturing in this way, the oxidized portion can be removed with little influence on the shape of the recess. Therefore, the concave portion can be processed into a desired shape with high accuracy.

  The method for manufacturing a silicon structure according to the present invention is characterized in that the mask pattern is made of silicon oxide.

By manufacturing in this way, when etching a base material by anisotropic dry etching, a base material can be etched using the selectivity of a mask pattern and a base material. Therefore, it becomes possible to form a recessed part in multiple steps.
Further, the mask pattern can be removed together with the oxidized portion removing step. Therefore, the number of processes can be reduced and productivity can be improved.

<First embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In the following drawings, the scale is appropriately changed for each layer and each member so that each layer and each member can be recognized on the drawing.
In the present embodiment, a silicon structure used in a field such as MEMS (Micro Electro Mechanical System) is manufactured by forming multi-stage recesses (holes, trenches, etc.) having steps inside on a substrate made of silicon. A method will be described. Here, in order to manufacture a silicon structure having a recess having a step inside by etching the substrate, first, a mask pattern corresponding to the shape of the recess is formed on the surface of the substrate.

  1 to 3 are views showing a manufacturing process of the silicon structure according to the present embodiment. FIG. 1A is a cross-sectional view of the substrate and an enlarged plan view of the recessed portion forming region, and FIG. 1B is an enlarged plan view of the recessed portion forming region. 2A to 2C and 3A are cross-sectional views of the base material, and FIG. 2B is a cross-sectional view of the base material and an enlarged plan view of the recess.

(Mask pattern forming process)
As shown in FIG. 1 (a), first, the surface 1a of the substrate 1 made of silicon, to form, for example, a hard mask (mask pattern) 2 made of silicon oxide such as SiO _2. The hard mask 2 can be formed, for example, by thermally oxidizing the surface 1a of the substrate 1 or by forming a film on the surface 1a of the substrate 1 by a vacuum deposition method, a sputtering method, a CVD method, or the like. .
Next, a photoresist 3 is formed on the surface 2 a of the hard mask 2. Next, the photoresist 3 is exposed and developed and patterned. And the groove-shaped opening part 31 arrange | positioned by the substantially concentric annular shape by planar view, and the substantially circular hole-shaped opening part 32 by planar view are formed.

Here, as shown in FIG. 1B, the groove-shaped opening 31 forms a plurality of (for example, six) openings 31a to 31f adjacent in the width W direction in a substantially concentric annular shape. . The groove-shaped openings 31a to 31f are uniformly patterned so that the dimensions in the width W direction are substantially equal.
Further, an interval corresponding to the thickness Tw of the base material 1 left as a partition wall 1w (see FIG. 2C) is provided in the width W direction between the openings 31a to 31f and 32 in an etching process described later. Keep it.

When patterning the photoresist 3, the shape of the openings 31, 32, the dimension of the opening 31 in the width W direction, and the dimension of the opening 32 in the diameter R direction are adjusted as follows, for example.
First, the relationship between the depths d1 and d2 of the initial recesses 11 and 12 formed in the etching process to be described later, the size and shape of the openings 51 and 52 (see FIG. 2C), and the etching rate of the substrate 1. Adjust according to.
At this time, the depths d1 and d2 of the initial recesses 11 and 12 are larger than the depths D1 and D2 of the recesses 4 to be finally formed in the oxidized portion removing step described later (see FIG. 3A). ) Is adjusted to be shallow (inside the recess 4) by the thickness To1 of the substrate 1 to be removed.

Furthermore, the outer edge of the outermost opening 31f of the groove-shaped opening 31 formed substantially concentrically in a plan view is from the inner side surface 4a1 of the recess 4 (see FIG. 3B) that is finally formed. Also, the base material 1 is formed inside the recess 4 by a thickness To1 that is removed as the oxidized portion Ox. Further, the diameter R of the hole-shaped opening 32 is larger than the inner surface 4a2 of the step G1 of the recess 4 finally formed by a thickness To1 at which the base material 1 is removed as the oxidized portion Ox. Form inside.
That is, the shape of the openings 31 and 32, the dimension of the opening 31 in the width W direction, and the dimension of the opening 32 in the diameter R direction are the thickness of the substrate 1 from which the initial recesses 11 and 12 are removed as the oxidized portion Ox. It is adjusted to be smaller than the recess 4 (to the inside of the recess 4) by To1.

In this embodiment, the dimension of the recess 4 (see FIG. 3B) to be finally formed is as follows, for example. The diameter R1 of the opening 5 is about 60 μm, the inner diameter R2 of the step G1 is about 20 μm, the depth D1 to the bottom surface 4b1 on the upper side (shallow side) of the step G1 is about 40 μm, and the lower side (deep side) of the step G1. The depth D2 to the bottom surface 4b2 is about 60 μm.
At this time, adjustment of the shape of the openings 31 and 32 of the photoresist 3 shown in FIGS. 1A and 1B, the dimension of the opening 31 in the width W direction, and the dimension of the opening 32 in the diameter R direction are adjusted. Is performed as follows, for example.

First, with the target of the depths D1 and D2 of the recess 4 to be finally formed, the opening of the initial recess 11 is determined from the relationship between the size and shape of the openings 51 and 52 of the initial recesses 11 and 12, which will be described later, and the etching rate. 51, the dimension in the width W direction and the dimension in the diameter R direction of the opening 52 of the initial recess 12 are calculated.
Next, the thickness To of the oxidized portion Ox (see FIG. 3A) is set in the oxidized portion removing step described later, and the thickness To1 of the base material 1 removed from the inner surfaces of the initial recesses 11 and 12 is calculated. To do. The thickness To1 of the base material 1 removed as the oxidized portion Ox is about 0.45 times the thickness To of the oxidized portion Ox.

In the present embodiment, the thickness To of the oxidized portion Ox is set to about 4 μm, for example, and the thickness To1 of the substrate 1 to be removed is set to about 1.8 μm.
Then, the calculated dimensions of the openings 51 and 52 of the initial recesses 11 and 12 are reduced by the thickness To1 to be removed. The reduced size is set as the size of the openings 31 and 32 of the photoresist 3.
Thereby, the width W of the groove-shaped openings 31a to 31f of the photoresist 3 is adjusted to about 2.1 μm, and the diameter R of the hole-shaped opening 32 is adjusted to about 16.4 μm.

Further, from the thickness To1 of the base material 1 removed from the inner surfaces of the initial recesses 11 and 12, the thickness Tw of the base material 1 remaining as the partition wall 1w is determined in an etching process described later. Further, the thickness Tw of the partition wall 1w is determined so that the adjacent partition walls 1w are not buffered after oxidation in consideration of the thickness that is increased by being oxidized in the later-described oxidation portion forming step.
Here, the thickness Tw of the partition wall 1w is preferably less than twice the thickness To1 of the base material 1 to be removed. More preferably, the thickness is less than about 0.9 times the thickness To1 of the substrate 1 to be removed as the oxidized portion Ox.

In the present embodiment, the thickness Tw of the partition wall 1w remaining between the initial recesses 11a to 11f in the etching process described later is about 1.25 μm. And the space | interval of each width W direction of opening part 31a-31f, 32 is set to the space | interval of about 1.25 micrometers equal to thickness Tw.
Here, since the width W of each of the groove-shaped initial recesses 11a to 11f is set to about 2.1 μm, the center interval between the remaining partition walls 1w is adjusted to about 3.35 μm.

  Next, the hard mask 2 exposed in the openings 31 and 32 of the photoresist 3 is etched by dry etching to form openings 21 and 22 as shown in FIG. Thereby, the shapes and dimensions of the openings 31 and 32 of the photoresist 3 adjusted as described above and the shapes and dimensions of the openings 21 and 22 of the hard mask 2 are formed substantially the same. Here, as an etchant (etching gas) for dry etching, for example, a CF-based gas can be used.

Next, the photoresist 3 on the surface 2a of the hard mask 2 is removed, and the hard mask 2 is exposed as shown in FIG.
By the above, the hard mask 2 provided with the opening parts 21 and 22 which covers the surface 1a of the base material 1 and exposes the base material 1 in the formation region of the initial recesses 11 and 12 is formed.

(Etching process)
Next, as shown in FIG. 2C, the base material 1 exposed in the openings 21 and 22 of the hard mask 2 is anisotropically etched in the depth direction, so that the base material 1 has a plurality of substantially annular shapes. The groove-shaped initial recesses 11a to 11f and the substantially cylindrical hole-shaped initial recess 12 are collectively formed.
Here, for example, the substrate 1 is etched by anisotropic dry etching in which an etching step using fluorine gas such as SF6 and oxygen and a polymer deposition step using C4F8 gas are alternately performed.

And in the state which left the base material 1 as the partition 1w between each of the initial recessed parts 11a-11f, 12, several initial recessed parts 11a- from which the dimension and shape of opening part 51a-51f, 52 differ in the base material 1. 11f and 12 are formed together.
At this time, the substrate 1 is etched at different etching rates depending on the dimensions and shapes of the openings 51 and 52 of the initial recesses 11 and 12 by the microloading effect described later. The initial recesses 11 and 12 are collectively formed at different depths d1 and d2.

  Further, the openings 51 and 52 of the initial recesses 11 and 12 are formed to have substantially the same size and shape as the openings 21 and 22 of the hard mask 2. That is, it is formed in substantially the same size and shape as the openings 31 and 32 of the photoresist 3 adjusted as described above. Therefore, the depths d1 and d2 of the initial recesses 11 and 12 are controlled to a predetermined value.

  And the initial recessed parts 11 and 12 are formed smaller than the recessed part 4 finally formed by thickness To1 by which the base material 1 is removed as the oxidation part Ox in the process mentioned later. In other words, it is formed inside the recess 4 rather than the inner surface of the recess 4. In addition, the hard mask 2 formed as described above leaves the partition wall 1w between each of the initial recesses 11a to 11f and 12 with a thickness Tw that is completely oxidized in the oxidation portion forming process described later. In the present embodiment, the thickness 1w of the partition wall 1w is formed to be about 1.25 μm.

Further, each of the openings 21 a to 21 f of the hard mask 2 is formed in substantially the same shape and size as each of the openings 31 a to 31 f of the photoresist 3. Therefore, each of the openings 21a to 21f of the hard mask 2 is formed to have substantially the same dimension in the width W direction (see FIG. 1B). Moreover, all are formed in the substantially uniform annular | circular shaped uniform groove shape.
Therefore, the dimensions in the width W direction of the openings 51a to 51f of the plurality of adjacent initial recesses 11a to 11f are formed uniformly (substantially the same). As a result, each of the initial recesses 11a to 11f is etched at substantially the same etching rate, and is formed at substantially the same depth d1.

(Oxidation part formation process)
Next, after removing the hard mask 2 on the surface 1a of the substrate 1, the surface 1a of the substrate 1 and the partition walls are oxidized by oxidizing the substrate 1 on the inner surface including the bottom surface and the inner surface of the initial recesses 11 and 12. The whole 1w is oxidized to form an oxidized portion Ox having a predetermined thickness To as shown in FIG.
The oxidation of the inner surfaces of the initial recesses 11 and 12 can be performed by, for example, thermal oxidation in which the inner surfaces of the initial recesses 11 and 12 are heated to high temperatures to be oxidized. The thickness To of the oxidized portion Ox can be controlled by adjusting the temperature, the heating time, etc. in the thermal oxidation. In this embodiment, thermal oxidation is performed at a high temperature of, for example, 1000 ° C. or higher. Then, the base material 1 is oxidized by the thickness To1.

  In the present embodiment, the base material 1 on the inner surface of the initial recesses 11 and 12 is oxidized by about 1.8 μm for a thickness To1, and an oxidized portion Ox having a thickness To of about 4 μm is formed. And the dimension of the opening parts 51 and 52 of the initial stage recessed parts 11 and 12 in the width W direction, ie, the space | interval of the partition 1w, is set to about 0.57 micrometer. Further, the partition wall 1w is completely oxidized, and the thickness Tw is increased from about 1.25 μm to about 2.78 μm.

(Oxidation removal process)
Next, the oxidized portion Ox including the inner surfaces of the initial recesses 11 and 12 oxidized in the above-described steps and the partition wall 1w is removed to form the entire shape of the recess 4 as shown in FIG. . Here, the oxidation portion Ox is removed by wet etching using an etchant.
Thereby, the partition wall 1w that has isolated the initial recesses 11 and 12 is removed, and the depths D1 and D2 in the direction of the depths D1 and D2 are between the bottom surfaces 4b1 and 4b2 having different depths D1 and D2 from the surface 1a of the substrate 1. A step G1 is formed.
Through the above-described steps, the multi-stage recessed portion 4 having the step G1 on the inner side is formed in the base material 1.

Next, the operation of this embodiment will be described.
FIG. 4 is a graph showing the relationship between the size and shape of the openings 51 and 52 of the initial recesses 11 and 12 and the etching depths d1 and d2 when the substrate 1 is etched for a certain time in the above-described etching process. .
In FIG. 4, the vertical axis indicates the etching depths d1 and d2 of the initial recesses 11 and 12, and the predetermined etching depths d1 and d2 (100 μm or more) are represented as “1”. The horizontal axis is a logarithmic axis indicating the dimensions of the openings 51 and 52 of the initial recesses 11 and 12.
In FIG. 4, the solid line indicates data of the groove-shaped initial recess 11, and the broken line indicates data of the hole-shaped initial recess 12. The dimension of the groove-shaped initial recess 11 indicates the width W, and the dimension of the hole-shaped initial recess 12 indicates the diameter R.

As shown in FIG. 4, when the width W dimension of the groove-shaped initial recess 11 and the diameter R dimension of the hole-shaped initial recess 12 are equal, when the dimension is 100 μm or less, even with the same etching time, At a predetermined depth, the groove-shaped initial recess 11 has a deeper etching depth d1 than the hole-shaped initial recess 12.
That is, when the width W dimension and the diameter R dimension are equal, the etching rate of the groove-shaped initial recess 11 is larger than the etching rate of the hole-shaped initial recess 12.
Thus, the etching rate depends on the shapes of the openings 51 and 52 of the initial recesses 11 and 12.

Further, by increasing the width W dimension of the groove-shaped initial recess 11, the deeper initial recess 11 can be formed within a certain time. That is, the etching rate can be increased. Similarly, by increasing the diameter R dimension of the hole-shaped initial recess 12, the etching rate can be increased and the deeper initial recess 12 can be formed within a certain time.
In addition, by making the diameter R dimension of the hole-shaped initial recess 12 larger than the width W dimension of the groove-shaped initial recess 11 by a predetermined ratio, the depth of the hole-shaped initial recess 12 formed within a predetermined time is increased. The length d2 can be made deeper than the depth d1 of the groove-shaped initial recess 11.

  In the present embodiment, as described above, the width W of the groove-shaped openings 31a to 31f of the photoresist 3 is adjusted to about 2.1 μm, and the diameter R of the hole-shaped opening 32 is sufficiently larger than the width W. It is adjusted to a large size of about 16.4 μm. The openings 21 and 22 of the hard mask 2 are formed in the same size and shape, and the sizes and shapes of the openings 51 and 52 of the initial recesses 11 and 12 are also formed in the same manner.

  That is, the diameter R dimension of the opening 52 of the hole-shaped initial recess 12 is formed sufficiently larger than the width W dimension of the opening 51 of the groove-shaped initial recess 11. Thereby, the etching rate of the base material 1 in the hole-shaped initial recess 12 can be made larger than the etching rate of the groove-shaped initial recess 11. Then, by etching for a predetermined time, the depth d2 of the opening 52 of the hole-shaped initial recess 12 is formed to about 58.2 μm, and the depth d2 of the groove-shaped initial recess 11 is about 38.degree. It is formed to 2 μm.

  At this time, the base material 1 constituting the inner surface of the initial recesses 11a to 11f and 12 remains as a partition wall 1w that separates the initial recesses 11a to 11f and 12 between the initial recesses 11a to 11f and 12, Initial recesses 11a to 11f and 12 are formed. That is, the plurality of initial recesses 11 and 12 having different etching depths d1 and d2 are separated by the partition wall 1w and etched in an isolated state.

  Then, the inner surfaces of the initial recesses 11 and 12 and the partition wall 1w are oxidized to form an oxidized portion Ox, and the oxidized portion Ox is removed to form the entire shape of the recessed portion 4. At this time, the inner surface of the recess 4 is smoothed. Further, the partition wall 1w that separates the initial recesses 11 and 12 adjacent to each other in the surface 1a direction of the base material 1 is removed, and a step G1 in the depth D1 and D2 direction is formed inside the recess 4.

Here, for comparison with the present embodiment, FIGS. 8A to 8B and FIGS. 9A to 9C are cross-sectional views illustrating a conventional method for manufacturing a silicon structure.
In the conventional manufacturing method, as shown in FIG. 8, when the recess 10 having the bottom surfaces 401b and 402b having different depths is formed by etching the substrate 10, the boundary between regions having different depths (FIG. ) Part B).

  When irregularities are formed on the inner side surface 402a of the recess 40 as shown in FIGS. 8A to 8B at the boundary between regions having different depths, the following problems arise. For example, polymer deposition on the inner surface 402a may be hindered by the influence of the convex portion 402c of the inner surface 402a. In such a case, a thin film may not be formed on the inner surface 402a in the vicinity of the step G of the recess 40, or the thickness of the thin film in that portion may be reduced.

  Further, in the conventional manufacturing method, after forming the shape of the deepest portion of the concave portion 40, when the bottom surface 402b of the deepest portion of the concave portion 40 and the concave portion formation region 40A of the base material 10 are collectively etched, There is a problem like this. For example, the etching conditions are different between the bottom surface 402b at the deepest portion and the bottom surface 401b at a shallower position. For this reason, the adjustment width (process margin) of various parameters in the process of depositing the polymer is very narrow, and it is very difficult to make the film thickness uniform.

  As described above, when the thickness of the thin film deposited in the vicinity of the step G on the inner surface 402a of the recess 40 is too thin, the etching proceeds in the lateral direction (direction perpendicular to the depth direction), and the step of the recess 40 G corner C is etched. And as shown to Fig.9 (a), the inner surface 402a of the deepest part of the recessed part 40 will be formed in a taper shape.

  On the other hand, when the film thickness of the inner surface 402a of the recess 40 is too thick, the shadowed portion of the protrusion 402c is an anisotropic dry etching etching step as shown in FIG. May remain. In such a case, as shown in FIG. 9B, the base material 10 remains in a protruding shape at the step G of the recess 40.

  As shown in FIG. 9C, when the bottom surface 402b of the deepest portion of the recess 40 is roughened by etching, there are the following problems. For example, in the step of depositing the thin film, the polymer is not uniformly deposited in the vicinity of the deepest corner Cb (the boundary between the bottom surface 402b and the inner surface 402a) of the recess 40, and the inner surface 402a of the deepest portion of the recess 40 is also etched. It will be in a rough state.

  However, in the present embodiment, as shown in FIG. 2C, the plurality of initial recesses 11 and 12 having different etching depths d1 and d2 are separated by the partition walls 1w and etched in an isolated state. . Therefore, in the etching process, there is no boundary between regions having different depths as in the conventional case. Therefore, the problem in the conventional manufacturing method as shown in FIGS. 9A to 9C can be solved. Thereby, the initial recesses 11 and 12 can be formed with high aspect ratio and high accuracy.

Moreover, in the etching process, the base material 1 can be selectively etched in the depth direction by etching the base material 1 by anisotropic dry etching.
Further, the depths of the initial recesses 11 and 12 can be controlled by adjusting the size or shape of the openings 51 and 52 of the initial recesses 11 and 12.

That is, as shown in FIG. 4, the initial recesses formed within a predetermined time by increasing the width W and the diameter R of the openings 51 and 52 of the initial recesses 11 and 12 to increase the etching rate of the substrate 1. The depths d1 and d2 of 11 and 12 can be increased. In addition, the widths W and diameters R of the openings 51 and 52 of the initial recesses 11 and 12 are reduced to reduce the etching rate of the substrate 1, and the depth d1 of the initial recesses 11 and 12 formed within a predetermined time. , D2 can be made shallower. Moreover, the etching rate of the base material 1 can be adjusted by adjusting the shape of the openings 51 and 52 of the initial recesses 11 and 12 to either the groove shape or the hole shape.
Therefore, the step G1 having a desired size and shape can be formed with high accuracy inside the recess 4.

  In addition, since the initial recesses 11 and 12 having different depths d1 and d2 can be formed at a time, the number of steps can be reduced as compared with the conventional method, the process margin can be increased, and the manufacturing process can be facilitated. .

Also, the plurality of groove-shaped openings 21a to 21f of the hard mask 2 are substantially the same as the groove-shaped openings 31a to 31f of the photoresist 3 patterned so that the dimensions in the width W direction are substantially equal to each other. Shaped and dimensioned. Therefore, in the etching process, the sizes and shapes of the openings 51a to 51f of the plurality of adjacent initial recesses 11a to 11f are equally formed. Thereby, the depth of several adjacent initial stage recessed parts 11a-11f is formed equally.
Therefore, by removing the partition walls 1w between the groove-shaped initial recesses 11a to 11f in the oxidized portion removing step, the bottom surface 4b1 of the recess 4 can be formed in a desired size and shape.

In the oxidized portion forming step, the inner surfaces of the initial recesses 11 and 12 and the partition walls 1w remaining between the initial recesses 11a to 11f and 12 are oxidized to become oxidized portions Ox.
At this time, as shown in FIG. 2C, the initial recesses 11 and 12 are smaller than the inner surface of the recess 4 finally formed by the thickness To1 processed into the oxidized portion Ox of the substrate 1 ( Formed inside the recess 4).

Therefore, the base material 1 on the inner surface of the initial recesses 11 and 12 is oxidized to the boundary of the inner surface (the inner side surfaces 4a1 and 4a2 and the bottom surfaces 4b1 and 4b2) of the recesses 4 to be finally formed to become the oxidized portion Ox. . Then, the oxidized portion Ox is removed in the oxidized portion removing step. Therefore, the recess 4 can be processed with higher processing accuracy than before.
Further, by removing the oxidized portion Ox, the unevenness of the inner surface of the recess 4 can be smoothed, and it is possible to prevent the inner surface of the recess 4 from becoming rough as in the prior art.

  Further, in the etching process, the thickness of the partition wall 1w is adjusted to a thickness that is completely oxidized in the oxidized portion forming process. That is, the thickness Tw of the partition wall 1w is less than twice the thickness To1 of the base material 1 to be removed. The partition wall 1w is oxidized from both directions (the inner direction and the outer direction of the recess 4) in the recess oxidation step. Therefore, by setting the thickness Tw of the partition wall 1w to be less than twice the thickness To1 where the base material 1 is processed as the oxidized portion Ox, the oxidized portion Ox having the thickness To is formed on the inner surface of the recess 4. In this case, the partition wall 1w can be completely oxidized.

In the present embodiment, the thickness Tw of the partition wall 1w is set to about 1.25 μm, which is more preferably less than 0.9 times the thickness To1 of the base material 1 to be removed as the oxidized portion Ox. Thereby, the partition wall 1w can be completely oxidized in the oxidation part forming step.
Therefore, the partition wall 1w remaining between the initial recesses 11a to 11f, 12 can be more reliably and easily removed in the oxidation portion removing step.

Further, the thickness Tw of the partition wall 1w is determined so that the adjacent partition walls 1w are not buffered after oxidation in consideration of the thickness that is increased by being oxidized in the oxidation portion forming step.
In the present embodiment, the thickness Tw of the partition wall 1w before oxidation is set to a more preferable about 1.25 μm, and the center interval between the partition walls 1w is about 3.35 μm. The dimension in the width W direction of the openings 51a to 51f of the initial recesses 11a to 11f before oxidation is formed to be about 2.1 μm. Therefore, even when the thickness Tw of the partition wall 1w is increased to about 2.78 μm after oxidation, an interval of about 0.57 μm can be formed between the partition walls 1w. Thereby, the buffering between the partition walls 1w after oxidation can be prevented.

Further, by forming the oxidized portion Ox by thermal oxidation, the heating temperature, the heating time, and the like can be adjusted to control the thickness To of the oxidized portion Ox. Therefore, the thickness To of the oxidized portion Ox can be easily adjusted, and the oxidized portion Ox having a uniform thickness To can be formed on the inner surface of the recess 4. In addition, the thickness To of the oxidation part Ox becomes thicker than the thickness To1 of the base material 1 before oxidation.
Further, by performing the thermal oxidation at a temperature of, for example, 1000 ° C. or more, the plane orientation dependency when the base material 1 is oxidized to form the oxidized portion Ox can be minimized. Thereby, the thickness To of the oxidized portion Ox formed on the bottom surface of the initial concave portions 11 and 12 and the thickness To of the oxidized portion Ox formed on the inner surface of the initial concave portions 11 and 12 can be made equal. .

Further, in the oxidized portion removing step, the oxidized portion Ox is removed and the entire shape of the recess 4 is formed. Thereby, the inner surface of the recessed part 4 is smoothed.
Further, the partition wall 1w between the initial recesses 11 and 12 having different depths can be removed, and the step G1 in the depth direction can be formed inside the recess 4.

  Further, by oxidizing (processing) the inner surfaces of the initial recesses 11 and 12 and the partition wall 1w to form an oxidized portion Ox made of silicon oxide, the difference in material between silicon oxide and silicon can be reduced in the oxidized portion removing step. By utilizing this, the oxidized portion Ox can be selectively removed.

  Further, by defining the shapes and dimensions of the openings 51 and 52 of the initial recesses 11 and 12 by the hard mask 2 in the etching process, a region other than the formation region of the initial recesses 11 and 12 is protected by the hard mask 2 The substrate 1 can be etched. Thereby, the dimension and shape of the opening parts 51 and 52 of the initial stage recessed parts 11 and 12 and the thickness Tw of the base material 1 left as the partition 1w can be prescribed | regulated.

Further, by using the hard mask 2 made of silicon oxide, the hard mask 2 can be removed together with the removal of the oxidized portion Ox in the oxidized portion removing step. At this time, by performing the oxidized portion removing step by wet etching, the oxidized portion Ox and the hard mask 2 can be selectively removed collectively without substantially affecting the substrate 1.
Moreover, when etching the base material 1 by anisotropic dry etching, the recessed part 4 can be etched in steps using the selection ratio of the hard mask 2 and the base material 1. FIG. Therefore, it becomes possible to form the recessed part 4 in multistage shape.

As described above, according to the silicon structure manufacturing method of the present embodiment, the high aspect ratio concave portion 4 having the step G1 on the inside can be easily formed with high processing accuracy.
Therefore, silicon can be stably processed with high processing accuracy even in a complicated structure such as a multi-stage trench having a plurality of steps inside, a multi-stage hole, or a combination of a trench and a hole.

  In addition, since the shape of the concave portion 4 can be prevented from collapsing or becoming an unstable shape, silicon with good reproducibility can be processed. Furthermore, since process variations (variations in parameters and the like affecting production) in the etching process can be minimized, a large process margin (variation width of parameters in the production process) can be ensured. In addition, since silicon can be processed stably with high processing accuracy, the MEMS can be reduced in size, performance, and reliability.

<Second embodiment>
Next, a second embodiment of the present invention will be described with reference to FIGS. This embodiment is different from the silicon structure manufacturing method described in the first embodiment in that the recess 41 has a groove shape. Since the other points are the same as in the first embodiment, the same parts are denoted by the same reference numerals and description thereof is omitted.
FIG. 5A is a perspective sectional view of the recess 41 finally formed in this embodiment, and FIG. 5B is a plan view of the opening of the photoresist 3.

(Mask pattern forming process)
As shown in FIG. 5A, when forming the groove-shaped recess 41 having the step G11 on the inside, first, as in the first embodiment shown in FIG. A hard mask 2 is formed on 1 a and a photoresist 3 is formed on the surface of the hard mask 2.
Then, as shown in FIG. 5B, the photoresist 3 is patterned to form a plurality of groove-shaped openings 311a to 311f having substantially the same width W1, and a groove-shaped opening having a width W2 larger than the width W1. 321 is formed.

Between each of the openings 311 a to 311 f and 321, as in the first embodiment, an interval corresponding to the thickness Tw of the base material 1 left as a partition wall 1 w (see FIG. 2C) in the etching step is wide. Open in the W1 and W2 directions.
Further, the shapes and dimensions of the openings 311 and 322 are the same as in the first embodiment shown in FIG. 2C, the depth of the initial recess (not shown) formed in the etching process, and the dimensions and shapes of the openings. It adjusts according to the relationship between the etching rate of the base material 1, and.

  Similarly to the first embodiment, the depth of the initial concave portion is larger than the depths D11 and D21 of the concave portion 41 to be finally formed in the oxidized portion removing process described later (see FIG. 3A). As a reference), the thickness of the substrate 1 to be removed is adjusted to be smaller (inward) by the thickness To1.

As in the first embodiment, the outermost opening 311f of the plurality of adjacent openings 311 is formed with the base material 1 as the oxidized portion Ox rather than the opening 51 of the recess 41 that is finally formed. The thickness To1 to be removed is arranged inside the width W1 direction.
In addition, the openings 311 and 321 are formed such that the base material 1 is more oxidized than the opening 51 of the recess 41 finally formed in the extending direction of the openings 311 and 322 perpendicular to the width W1 and W2 directions. As shown in FIG.

In this embodiment, the width W3 of the opening 51 of the recess 41 finally formed is substantially equal to the diameter R1 of the opening 5 of the recess 4 of the first embodiment. Further, the inner width W4 of the step G11 of the recess 41 is made substantially equal to the inner diameter R2 of the step G1 of the recess 4 of the first embodiment.
Further, the width W1 of the opening 311 of the photoresist 3 is made substantially equal to the width W of the groove-shaped opening 31 of the first embodiment. Further, the width W2 of the opening 321 is made substantially equal to the diameter R of the hole-shaped opening 32 of the first embodiment. And the thickness Tw of the base material 1 left as the partition 1w in an etching process is also determined similarly to 1st embodiment.

  Next, as in the first embodiment shown in FIGS. 2A and 2B, the hard mask 2 is etched and the photoresist 3 is removed. Then, the hard mask 2 having openings (not shown) having substantially the same shape and dimensions as the openings 311 and 322 of the photoresist 3 is formed.

(Etching process)
Next, similarly to the first embodiment shown in FIG. 2C, the base material 1 exposed at the opening of the hard mask 2 is anisotropically etched in the depth direction, so that the base material 1 has a plurality of widths. A groove-shaped initial recess having the same W1 and an initial recess having a width W2 larger than the width W1 are collectively formed.
Accordingly, as in the first embodiment, the depth of the initial recess is controlled to a predetermined value by the microloading effect, and initial recesses having different widths W1, W2 are collectively formed at different depths. In the present embodiment, both the planar shapes of the openings of the initial recesses having the widths W1 and W2 are formed in a groove shape. The narrow opening W1 is formed in the same manner as the width W of the opening 51 in the first embodiment, and the wide opening W2 is formed in the same manner as the diameter R of the opening 52 in the first embodiment. . Therefore, as shown in FIG. 4, the difference between the depths d <b> 1 and d <b> 2 between the initial recesses 11 and 12 is larger than in the case of the combination of the groove-shaped initial recess 11 and the hole-shaped initial recess 12 of the first embodiment. Become.

  Moreover, the initial recessed part is formed inside the recessed part 41 rather than the recessed part 41 finally formed by the thickness To1 by which the base material 1 is removed as the oxidized part Ox, as in the first embodiment. In addition, the partition wall 1w remains between each of the initial recesses with a thickness Tw that is completely oxidized in an oxidation portion forming process described later. In addition, the width W1 direction dimension of each of the openings of the adjacent narrow initial recesses having the width W1 is formed to be substantially the same, and each is formed to have substantially the same depth.

(Oxidation part formation process)
Next, the base material 1 on the inner surface of the initial recess including the bottom surface and the inner surface of the initial recess is oxidized, and the oxidized portion Ox having a predetermined thickness To as in the first embodiment shown in FIG. Form.

(Oxidation removal process)
Next, the oxidized portion Ox including the inner surface of the initial recess and the partition wall 1w oxidized in the above process is removed in the same manner as in the first embodiment shown in FIG. Form.
Thereby, the level difference G11 of depth D11, D21 direction is formed between the bottom face 41b1, 41b2 from which the depth D11, D22 from the surface 1a of the base material 1 differs similarly to 1st embodiment.
Through the above steps, a groove-shaped recess 41 having a multistage structure having a step G11 on the inside is formed in the base material 1.

  Therefore, according to this embodiment, not only the same effect as the first embodiment can be obtained, but also the groove-shaped recess 41 can be formed. Moreover, the difference of the depth D11, D22 of the recessed part 41 can be made larger than 1st embodiment by making both the initial recessed parts from which width W1, W2 differs into groove shape.

<Third embodiment>
Next, a third embodiment of the present invention will be described with reference to FIGS. The present embodiment is different from the silicon structure manufacturing method described in the second embodiment in that a plurality of concave portions having different shapes and depths are formed. Since the other points are the same as those of the second embodiment, the same parts are denoted by the same reference numerals and description thereof is omitted.
6A and 6B are cross-sectional views showing the manufacturing process of this embodiment, where FIG. 6A shows an etching process, FIG. 6B shows an oxidized part forming process, and FIG. 6C shows an oxidized part removing process.

As shown in FIG. 6A, in this embodiment, as in the above-described embodiment, in the etching process, a plurality of initial stages in which the widths W5, W6, and W7 of the openings 512, 522, and 532 are different from each other in the base material 1. The recesses 112, 122, 132 are formed in a lump.
At this time, the width W5 is smaller than the width W6 and larger than the width W7. Further, each of the plurality of adjacent initial recesses 112a and 112b is formed to have substantially the same width W5. Similarly, each of a plurality of adjacent initial recesses 132a to 132d is formed with a substantially equal width W7.

  As a result, the depth d12 of the initial recess 112 is shallower than the depth d22 of the initial recess 122 and deeper than the depth d32 of the initial recess 132. Further, the depth d12 of each of the plurality of adjacent initial recesses 112a and 112b becomes substantially equal. Similarly, the depths d32 of the plurality of adjacent initial recesses 132a to 132d are substantially equal.

  Further, the thickness Tw1 of the partition wall 11w between each of the initial recesses 112a, 112b, and 122 and the thickness Tw2 of the partition wall 12w between each of the initial recesses 132a to 132d are similar to those in the above-described embodiment. It is determined that they are completely oxidized in the forming process and do not buffer each other.

  Next, as shown in FIG. 6B, the inner surfaces of the initial recesses 112, 122, and 132, the partition walls 11w and 12w, and the surface 1a of the substrate 1 are oxidized in the same manner as in the oxidized portion forming step of the above-described embodiment. Thus, the oxidized portion Ox having a thickness To is formed. At this time, the base material 1 between the initial concave portion 122 and the initial concave portion 132 is not completely oxidized and a part thereof remains.

Next, as shown in FIG. 6C, the oxidized portion Ox is removed in the same manner as in the oxidized portion removing step of the above-described embodiment. Thereby, the recessed part 42a which has the level | step difference G12 of depth D12 and D22 direction inside, and the recessed part 42b adjacent to the recessed part 42a can be formed in the base material 1. FIG.
Therefore, according to this embodiment, not only the same effects as those of the first and second embodiments can be obtained, but also the plurality of recesses 42a and 42b can be formed in a lump.

<Fourth embodiment>
Next, a fourth embodiment of the present invention will be described with reference to FIGS. In the present embodiment, a plurality of concave portions having different shapes and depths are formed in stages, the amount of oxidation of the base material is sufficiently increased, and a tapered concave portion is formed. This is different from the manufacturing method of the silicon structure described. Since the other points are the same as those of the first embodiment described above, the same parts are denoted by the same reference numerals and description thereof is omitted.
7A and 7B are cross-sectional views showing the manufacturing process of the present embodiment, where FIG. 7A shows an etching process, FIG. 7B shows an oxidized part forming process, and FIG. 7C shows an oxidized part removing process.

As shown in FIG. 7A, in this embodiment, the widths W8, W9, W10, and W11 of the openings 513, 523, 533, and 543 are formed in the base material 1 in the etching process, as in the above-described embodiment. A plurality of different initial recesses 113, 123, 133, and 143 are formed collectively.
At this time, the width W8 is the smallest, and the width W9, the width W10, and the width W11 are formed so as to increase stepwise.
Thereby, the depths d13, d23, d33, d43 of the initial recesses 113, 123, 133, 143 are formed to be deeper in this order.

  Further, the thickness of the base material 1 remaining as a partition wall between each of the adjacent initial recesses 113, 123, 133, and 143 is adjusted so as to be completely oxidized in the oxidation part forming step. Moreover, it adjusts so that the partition-shaped base materials 1 may not buffer after oxidation. Further, the intervals between the initial recesses 113, 123, 133, and 143 are adjusted according to the angle of the tapered inner surface 43a of the recess 43 that is finally formed. Further, the thickness of the base material 1 that is oxidized to become the oxidized portion Ox is set to be sufficiently large so that the inner side surface 43a of the concave portion 43 to be finally formed has a smooth taper shape.

Next, as in the above-described embodiment, the inner surfaces of each of the initial recesses 113, 123, 133, and 143, the base material 1 between them, and the surface 1a of the base material 1 are oxidized, and FIG. As shown in (b), an oxidized portion Ox is formed.
In addition, the base material 1 remaining as a partition between each of the adjacent initial recesses 113, 123, 133, and 143 is completely oxidized and becomes a part of the oxidized portion Ox.

Next, as shown in FIG. 7C, the oxidized portion Ox is removed in the same manner as in the oxidized portion removing step of the above-described embodiment. Thereby, the concave part 43 which has the smooth inner surface 43a of the taper shape of a desired angle inside, and the level | step difference G13 of the depth D13 direction can be formed in the base material 1. FIG.
Therefore, according to the present embodiment, not only the same effect as the first embodiment can be obtained, but also the tapered inner side surface 43a having a desired angle and the step G13 in the direction of the depth D13 can be formed collectively. Can do.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the first embodiment described above, the opening of the initial recess has two different dimensions and shapes, and one step is formed inside the recess. However, the opening of the initial recess has three or more different dimensions. -You may form the level | step difference of 2 steps or more by forming in a shape.
In the first embodiment described above, the hard mask is removed prior to the oxidation portion forming step. However, the inner surface of the initial recess and the partition may be oxidized without removing the hard mask.
Further, the step may be formed by combining hole-shaped initial recesses having different diameters.

It is a figure explaining the manufacturing process of the silicon | silicone structure which concerns on 1st embodiment of this invention, (a) is sectional drawing and a top view, (b) is an enlarged plan view. (A)-(c) is sectional drawing explaining the manufacturing process of the silicon | silicone structure which concerns on 1st embodiment of this invention. It is a figure explaining the manufacturing method of the silicon | silicone structure which concerns on 1st embodiment of this invention, (a) is sectional drawing, (b) is sectional drawing and a top view. It is a graph which shows the relationship between the etching depth of the base material which concerns on 1st embodiment of this invention, and the dimension and shape of the opening part of an initial stage recessed part. It is a figure explaining the manufacturing process of the silicon | silicone structure which concerns on 2nd embodiment of this invention, (a) is a perspective sectional view, (b) is a top view. (A)-(c) is sectional drawing explaining the manufacturing process of the silicon | silicone structure which concerns on 3rd embodiment of this invention. (A)-(c) is sectional drawing explaining the manufacturing process of the silicon | silicone structure which concerns on 4th embodiment of this invention. (A) And (b) is sectional drawing explaining the problem of the manufacturing method of the conventional silicon structure. (A)-(c) is sectional drawing explaining the problem of the manufacturing method of the conventional silicon structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material, 2 Hard mask (mask pattern), 4 Recessed part, 11, 12 Initial recessed part, 21 (21a-21f), 22 Opening part, 41 Recessed part, 42a, 42b Recessed part, 43 Recessed part, 1w Bulkhead, 11w, 12w Bulkhead , R, R1, R2 diameter (dimensions), To, To1 thickness, Tw, Tw1, Tw2 thickness, Ox oxidation part, 112, 122, 132 initial recess, 113, 123, 133, 143 initial recess, d1, d2 Depth, d12, d22, d32 depth, d13, d23, d33, d43 depth, G1, G11, G12, G13 step, W, W1-W11 width (dimensions)

Claims (10)

A method of manufacturing a silicon structure in which a concave portion having a step in the depth direction is formed inside a base material made of silicon,
A mask pattern forming step of forming a mask pattern having a plurality of openings having different dimensions or shapes;
Etching step of anisotropically dry etching the base material exposed in the plurality of openings simultaneously in the depth direction to form a plurality of initial recesses having different depths;
Oxidizing the inner surfaces of the plurality of initial recesses to oxidize the entire base material remaining as a partition between each of the initial recesses to form an oxidized part; and
Removing the oxidized portion to form the concave portion; and
A method for producing a silicon structure, comprising:   2. The method of manufacturing a silicon structure according to claim 1, wherein the depth of the initial recess is controlled in the etching step by adjusting the size or the shape of the opening in the mask pattern forming step. .   By adjusting the gap between the openings in the mask pattern forming step, the thickness of the partition between the initial recesses in the etching step is adjusted to a thickness that is completely oxidized in the oxidized portion forming step. The method for manufacturing a silicon structure according to claim 1, wherein:   4. The method of manufacturing a silicon structure according to claim 1, wherein in the mask pattern forming step, the dimensions and shapes of the plurality of adjacent openings are formed uniformly. 5.   In the mask pattern forming step, among the plurality of openings, the opening located on the outermost side in a plan view has a thickness corresponding to the thickness at which the base material is removed as the oxidized portion in the oxidized portion removing step, The method for manufacturing a silicon structure according to any one of claims 1 to 4, wherein the silicon structure is formed inside the recess rather than an inner surface of the recess.   By adjusting the size or the shape of the opening in the mask pattern forming step, the depth of the initial recess is the thickness by which the base material is removed as the oxidized portion in the oxidized portion removing step, The method for manufacturing a silicon structure according to claim 1, wherein the silicon structure is formed shallower than a depth of the recess.   7. The method of manufacturing a silicon structure according to claim 1, wherein, in the mask pattern forming step, the shape of the opening is a groove shape or a hole shape.   The method for manufacturing a silicon structure according to claim 1, wherein the oxidized portion forming step is performed by thermal oxidation by heating.   The method for manufacturing a silicon structure according to claim 1, wherein the oxidized portion removing step is performed by wet etching.   The method for manufacturing a silicon structure according to claim 1, wherein the mask pattern is made of silicon oxide.

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