JP5152468B2 - Crystal substrate etching method - Google Patents

Description

  The present invention relates to a method for etching a crystal substrate in which recesses having different depths are simultaneously formed by anisotropically etching a crystal substrate having a (100) plane or (110) plane crystal surface orientation.

  A recess including a through-hole provided in a crystal substrate used for a micro device or the like can be formed by anisotropic etching (wet etching) through a mask having an opening that opens in a parallelogram. .

  However, when performing microfabrication by anisotropically etching a narrow region of the substrate, even if the mask is provided with an opening that opens in the narrow region, a recess that opens in the narrow region is formed due to the characteristics of anisotropic etching. There is a problem that can not be.

  For this reason, there is a method for manufacturing a microdevice in which a mask is provided with a correction pattern (elongated portion) that is gradually etched together with the substrate to widen the opening area of the opening, and a minute through hole is formed in the substrate by this correction pattern. Yes (see, for example, Patent Document 1).

JP-A-11-227197 (page 6, FIG. 5)

  Here, in order to form fine recesses having different depths in the crystal substrate, the recesses having different depths can be formed by different etching processes, but one recess having a deep or shallow depth was formed. Later, when forming the other recess, one of the recesses must be protected with a protective film or the like so as not to be etched. Thus, in order to form a protective film in the middle of an etching process, work, such as washing | cleaning of etching liquid, is needed, and there exists a problem that manufacturing cost will become high cost.

  Further, as a method of forming recesses having different depths in the crystal substrate, a second correction pattern for forming deep recesses is provided on the mask, and the crystal substrate is deeply etched anisotropically using the second correction pattern. After forming the recess in the middle of the depth direction (first etching step), a first correction pattern for forming a shallow recess is provided, and the crystal substrate is formed using the first correction pattern and the second correction pattern. By anisotropic etching (second etching step), a method of simultaneously forming recesses having different depths can be mentioned.

  However, in anisotropic etching of a crystal substrate, the etching rate (etching speed) varies depending on the environment such as the temperature of the etching solution and the components of the etching solution, so that it remains in the first etching step. The length of the second correction pattern used in the second etching process varies. For this reason, when the second etching step is performed, the wall surface position of the deep recess using the second correction pattern cannot be controlled with respect to the wall surface position of the shallow recess using the first correction pattern. There is a problem that variations occur in the wall surface position of the deep recess. In addition, when etching is performed until the wall surface position of the deep recess becomes a desired position in the second etching step in the state where the length of the remaining second correction pattern varies, the first recess There is a problem in that the wall surface position cannot be controlled, and the wall surface position of the first concave portion varies. In particular, when recesses with different depths communicate with the crystal substrate and are formed in steps, the recesses with different depths cannot be formed in different etching processes, and the crystal substrate is changed multiple times as described above. Recesses with different depths must be formed simultaneously by isotropic etching, and such a problem appears remarkably.

  In view of such circumstances, an object of the present invention is to provide a method for etching a crystal substrate that can easily and accurately form recesses having different depths.

The present invention for solving the above-described problems provides a mask having an opening on the surface of a crystal substrate having a crystal plane orientation of (100) or (110) on the surface, and the mask and the substrate together with the substrate from the start portion to the end portion. Etching of crystal substrate to form recesses having different depths by providing a correction pattern that gradually etches until the opening area of the opening is widened and anisotropically etching the crystal substrate a plurality of times through the mask In the method, as the correction pattern, a first thick film portion used when forming the first concave portion which is the concave portion, and a surface of the crystal substrate which is thinner than the first thick film portion and which is thinner than the first thick film portion. A first thin film provided on the start portion side and used for forming a first correction pattern including a first thin film portion to be covered and a second concave portion deeper than the first concave portion. And the part A second correction pattern comprising a second thick film portion that is thicker than the thin film portion and has the same length as the first thick film portion, and the second correction pattern includes the second correction pattern. A first etching step in which etching is performed halfway in the depth direction of the second recess using the thin film portion; and the first thin film portion and the second thin film portion are formed by thinning the entire mask. And removing the film simultaneously, and using the second thick film portion of the second correction pattern, etching is started in the middle of the depth direction of the second recess to form the second recess. And a second etching step of forming the first recess by using the first thick film portion of the first correction pattern.
In this aspect, since the relative wall surface positions of the first concave portion and the second concave portion having different depths can be controlled without being affected by variations in the etching rate, the concave portions having different depths can be easily formed. In addition, it can be formed with high accuracy. In addition, since the first thin film portion and the second thin film portion can be simultaneously removed by the removing process, the manufacturing process can be simplified and the cost can be reduced. Furthermore, a protective film or the like is not necessary and manufacturing costs can be reduced as compared with the case where recesses having different depths are formed in a crystal substrate by another etching process.

  Here, the mask may be formed adjacent to the first recess so as to communicate with the second recess. According to this, the recessed part from which the depth which cannot be formed in another etching process can be formed easily and with high precision.

  Further, as the first thick film portion and the second correction pattern, a region other than the start portion on the outer periphery is surrounded by a plane along the (111) plane of the crystal plane orientation of the crystal substrate, and the start It is preferable to form such that the corner portion having an angle smaller than 180 degrees is not defined other than the portion. According to this, it is possible to easily and accurately form the recesses having different desired depths in the narrow width region without starting etching from the region other than the start portion of the correction pattern.

Hereinafter, the present invention will be described in detail based on embodiments.
(Embodiment 1)
FIG. 1 is a cross-sectional view of a crystal substrate according to Embodiment 1 of the present invention. As shown in FIG. 1, the crystal substrate 1 of the present embodiment is formed of a silicon single crystal substrate whose surface crystal plane orientation is (110) plane. The crystal substrate 1 is formed with a first recess 2 having a shallow depth in the thickness direction of the crystal substrate 1 and a second recess 3 deeper than the first recess 2. In the present embodiment, the first recess 2 and the second recess 3 do not communicate with each other and are provided at positions separated by a predetermined distance.

  Here, the etching method of the crystal substrate 1 in which the first recess 2 and the second recess 3 having different depths are formed in the crystal substrate 1 of the present embodiment by anisotropic etching will be described in detail. 2 to 5 are plan views showing the method for etching a crystal substrate according to Embodiment 1 of the present invention, and FIGS. 6 and 7 are cross-sectional views taken along the line AA ′ of FIGS.

As shown in FIGS. 2 and 6A, a mask 10 is formed on the surface of the crystal substrate 1. As a material of the mask 10, for example, silicon dioxide (SiO ₂ ), silicon nitride (SiN), or the like can be used. As a mask forming method, for example, a silicon single crystal substrate is thermally oxidized to form a mask made of silicon dioxide on its surface, or a mask made of silicon dioxide or silicon nitride by sputtering, CVD, or the like. The method of forming is mentioned.

  Further, by patterning the mask 10, a first opening 11 for forming the first recess 2 and a second opening 12 for forming the second recess 3 are provided, and the openings 11, 12 are provided. A correction pattern 20 is provided.

  The correction pattern 20 is provided in the first opening 11 to form the first recess 2 and the first correction pattern 21 is provided in the second opening 12 to form the second recess 3. 2 correction patterns 22.

  The first correction pattern 21 covers the first opening 11, is removed in a subsequent removal step, and the first thin film portion 30 exposing the first opening 11 and the first thin film portion 30. The second thick film portion 31 also has a large thickness.

  The first thick film portion 31 is gradually etched together with the crystal substrate 1 from the start portion 21a to the end portion 21b to widen the opening area of the first opening portion 11, and a region other than the outer periphery of the start portion 21a is formed. The crystal substrate 1 is surrounded by a plane along the (111) plane of the crystal plane orientation. In addition, the first thick film portion 31 is provided on the outer periphery other than the start portion 21a so that corner portions having an angle smaller than 180 degrees are not defined.

  The first thick film portion 31 is provided with such a length that the first concave portion 2 can be formed with a predetermined depth and width when the crystal substrate 1 is anisotropically etched in a second etching step described later. It has been.

  The second correction pattern 22 is gradually etched together with the crystal substrate 1 from the start portion 22a to the end portion 22b to widen the opening area of the second opening portion 12, and the region other than the outer periphery start portion 22a is a crystal. The substrate 1 is surrounded by a plane along the (111) plane of the crystal plane orientation. Further, the second correction pattern 22 is provided so that corners with an angle smaller than 180 degrees are not defined on the outer periphery other than the start portion 22a.

  The second correction pattern 22 includes a second thin film portion 32 on the start portion 22a side and a second thick film portion 33 that is thicker than the second thin film portion 32 on the end portion 22b side. It has been.

The second thin film portion 32 is provided with a length that remains when the crystal substrate 1 is anisotropically etched in a first etching step described later. Further, the length L ₂ of the second thick film portion 33 is provided to be the same length as the length L ₁ of the first thick film portion 31 of the first correction pattern 21.

  The first correction pattern 21 and the second correction pattern 22 are formed by forming the mask 10 over the entire surface of the crystal substrate 1 and then etching the mask 10 through a resist provided in a predetermined shape on the mask 10. By doing so, it can be formed in a predetermined shape. The first thin film portion 30 and the first thick film portion 31 of the first correction pattern 21, the second thin film portion 32 and the second thick film portion 33 of the second correction pattern 22, etc. are resists. The mask 10 can be formed by etching a plurality of times while changing the shape.

  Next, as shown in FIGS. 3 and 6B, the crystal substrate 1 is anisotropically etched through the mask 10, so that the second recess 3 is etched halfway in the depth direction (first step). 1 etching step).

  Here, anisotropic etching is performed using the difference in etching rate of the crystal substrate 1 made of a silicon single crystal substrate. In this embodiment, since the crystal substrate 1 is composed of a silicon single crystal substrate having a plane orientation (110), the etching rate of the (111) plane is about 1 / compared with the etching rate of the (110) plane of the silicon single crystal substrate. It is performed using the property of being 180. That is, when the silicon single crystal substrate is immersed in an alkaline solution such as aqueous potassium hydroxide (KOH) or tetramethylammonium hydroxide (TMAH), the first (111) plane perpendicular to the (110) plane is gradually eroded. Then, a second (111) plane appears at an angle of 70.53 degrees with the first (111) plane and at an angle of 37.5 degrees with the (110) plane. By this anisotropic etching, precision processing is performed based on a parallelogram formed by two first parallel surfaces (111) and two second parallel surfaces (111). It can be carried out.

  In the present embodiment, since the first opening 11 forming the first recess 2 is covered with the first correction pattern 21, the first recess 2 side of the crystal substrate 1 is not etched, Only the second recess 3 side of the crystal substrate 1 is etched. In the first etching step, etching is performed halfway in the depth direction of the second concave portion 3 using the second thin film portion 32 provided on the start portion 22a side of the second correction pattern 22.

  In such a second thin film portion 32 (second correction pattern 22), the region other than the start portion 22a where the outer peripheral anisotropic etching is started is all in the first (111) crystal plane orientation of the crystal substrate 1. ) Plane and a plane along the second (111) plane. For this reason, the second thin film portion 32 is gradually etched from the start portion 22a without gradually starting etching from a region other than the start portion 22a, so that the opening area of the second opening portion 12 is gradually widened. It has become.

  Further, in the first etching process, the second thin film portion 32 of the second correction pattern 22 is not completely removed, and the second thin film portion 32 remains after the first etching process is completed. Do as follows. That is, the second thin film portion 32 needs to be formed in advance so that the length of the second thin film portion 32 is longer than the length at which the second recess 3 has a desired depth in the first etching step. Note that the second recess 3 having a desired depth in the first etching step can be defined by calculating backward from the depth of the second recess 3 formed by etching in the second etching step described later. .

  Next, as shown in FIGS. 4 and 7A, the entire mask 10 is thinned, and the second thin film portion 30 of the first correction pattern 21 and the second correction pattern 22 remain. The thin film portion 32 is simultaneously removed (removal step). In the present embodiment, the entire surface of the mask 10 is thinned by etching the surface side of the mask 10 in the thickness direction, and the second thin film portion 32 remaining in the first thin film portion 30 and the first etching step. And at the same time.

  At this time, since the first thick film portion 31 and the second thick film portion 33 are formed thicker than the first thin film portion 30 and the second thin film portion 32, the first thick film portion 31. The second thick film portion 33 is not removed, and the first thick film portion 31 and the second thick film portion 33 are formed in the first correction pattern 21 and the second correction pattern 22, respectively. As a result, the first opening 11 in which the first thick film portion 31 is formed opens in the region where the first recess 2 is formed.

  As described above, in the present embodiment, the first thin film portion 30 and the second thin film portion 32 are simultaneously removed by thinning the entire mask 10, and the first thick film portion 31 and the second thin film portion 32 are removed. Since the thick film portion 33 is formed, the manufacturing process can be simplified and the cost can be reduced.

  Next, as shown in FIGS. 5 and 7B, the first recess 2 and the second recess 3 are simultaneously formed by anisotropically etching the crystal substrate 1 through the mask 10 ( Second etching step).

Specifically, the first concave portion 2 is formed by anisotropically etching the crystal substrate 1 using the first thick film portion 31 of the first correction pattern 21. Simultaneously, the crystal substrate 1 is anisotropically etched using the second thick film portion 33 of the second correction pattern 22 so that the second recess 3 is further deeply etched to form the second recess 3. . At this time, since the length L2 of the _second thick film portion 33 is formed with the same length as the length L1 of the _first thick film portion 31, the etching is performed at a desired timing (control by time). , The position of the terminal portion 22b of the second thick film portion 33 (the second wall surface position of the first concave portion 2) with respect to the position of the terminal portion 21b of the first thick film portion 31 (the second wall surface position). The wall surface position of the recess 3 can be controlled to a desired position.

  That is, in anisotropic etching (wet etching), the etching rate varies depending on the environment such as the temperature of the etching solution and the components of the etching solution. For example, when the second correction pattern having a uniform thickness is provided, The length of the second correction pattern remaining in the first etching process varies. For this reason, when etching is performed in the second etching step, the wall surface position of the second recess 3 using the second correction pattern with respect to the wall surface position of the first recess 2 using the first correction pattern. Cannot be controlled, and the wall surface position of the second recess 3 will vary. Further, when the wall surface position of the second recess 3 is etched to a desired position in the state where the length of the second correction pattern remaining in the first etching process varies, the wall surface position of the first recess 2 Cannot be controlled, and the wall surface position of the first recess 2 will vary.

  As described above, in the present invention, the first concave portion 2 and the second concave portion 3 are obtained by anisotropically etching the crystal substrate 1 using the first correction pattern 21 and the second correction pattern 22. The relative wall surface position can be controlled. Thereby, the 1st recessed part 2 and the 2nd recessed part 3 from which the depth differs in the crystal substrate 1 can be formed easily and with high precision.

(Other embodiments)
As mentioned above, although Embodiment 1 of this invention was demonstrated, the basic composition of this invention is not limited to what was mentioned above. For example, in Embodiment 1 described above, a silicon single crystal substrate whose surface crystal plane orientation is a (110) plane is exemplified as the crystal substrate 1, but the present invention is not particularly limited thereto. A silicon single crystal substrate having a plane orientation of (100) may be used, or a material other than the silicon single crystal substrate, for example, a glass substrate, a glass epoxy substrate, a ceramic substrate, or the like may be used.

  In the first embodiment described above, the first concave portion 2 and the second concave portion 3 are provided in the crystal substrate 1 at a predetermined interval, and the first concave portion 2 and the second concave portion 3 do not communicate with each other. However, the present invention is not limited to this. For example, the first recess 2 and the second recess 3 may be provided adjacent to each other so that a step is formed. Even in such a case, the crystal substrate 1 can be formed easily and with high accuracy by performing anisotropic etching a plurality of times using the correction pattern 20 similar to that of the first embodiment described above.

  Furthermore, in the first embodiment described above, the crystal substrate 1 is provided with the first recess 2 and the second recess 3 having different depths. However, the present invention is not limited to this, and for example, the second recess 3 May be a through-hole penetrating the crystal substrate 1 in the thickness direction. For example, in the case where the second concave portion formed of the through hole is formed, the second correction pattern 22 may be provided on both surfaces of the crystal substrate 1 and anisotropic etching may be performed from both surfaces of the crystal substrate 1. .

  Moreover, in Embodiment 1 mentioned above, although the recessed part of the 2 types of depth of the 1st recessed part 2 and the 2nd recessed part 3 was formed in the crystal substrate 1, it is not limited to this in particular, For example, You may make it form the recessed part from which 3 or more types of depth differs. For example, when forming three types of concave portions having different depths, the first correction pattern 21 similar to that of the first embodiment described above is provided as the first correction pattern for forming the shallowest concave portion, and the intermediate depth is set. The second correction pattern 22 similar to that of the first embodiment described above is provided as the second correction pattern for forming the concave portion, and the terminal portion side is the second correction pattern 22 as the third correction pattern for forming the deepest concave portion. A third thin film portion formed with the same thickness and length and having a thickness thinner than that of the second thin film portion 32 on the tip side is used. Then, after the first anisotropic etching of the crystal substrate 1 is performed, the thickness of the entire mask is reduced so as to remove the third thin film portion, and then the first etching is performed in the same manner as in the first embodiment described above. By performing the etching step and the second etching step, three types of recesses having different depths can be formed. It should be noted that the same operation may be performed for four or more types of recesses.

  The above-described etching method of the crystal substrate 1 can be used, for example, when forming a member constituting the MEMS such as a microdevice such as a liquid jet head.

It is sectional drawing of the crystal substrate which concerns on Embodiment 1 of this invention. It is a top view which shows the etching method of the crystal substrate which concerns on Embodiment 1 of this invention. It is a top view which shows the etching method of the crystal substrate which concerns on Embodiment 1 of this invention. It is a top view which shows the etching method of the crystal substrate which concerns on Embodiment 1 of this invention. It is a top view which shows the etching method of the crystal substrate which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the etching method of the crystal substrate which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the etching method of the crystal substrate which concerns on Embodiment 1 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Board | substrate, 2 1st recessed part, 3 2nd recessed part, 10 Mask, 11 1st opening part, 12 2nd opening part, 20 Correction pattern, 21 1st correction pattern, 22 2nd correction pattern, 30 1st thin film part, 31 1st thick film part, 32 2nd thin film part, 33 2nd thick film part

Claims (3)

A mask having an opening is provided on the surface of the crystal substrate having a crystal plane orientation of (100) plane or (110) plane, and the opening is gradually etched together with the substrate from the start portion to the end portion. A correction pattern for expanding the opening area of the crystal substrate, and anisotropically etching the crystal substrate a plurality of times through the mask, thereby forming recesses having different depths,
As the correction pattern, a first thick film portion used when forming the first concave portion that is the concave portion, and a first thin film that is thinner than the first thick film portion and covers the surface of the crystal substrate And a second thin film portion provided on the start portion side, the second thin film portion being used when forming a second concave portion deeper than the first concave portion. A second correction pattern comprising a second thick film portion that is thicker than the two thin film portions and has the same length as the first thick film portion,
A first etching step in which etching is performed halfway in the depth direction of the second concave portion using the second thin film portion of the second correction pattern; Removing the thin film portion and the second thin film portion simultaneously, and etching from the middle of the second concave portion in the depth direction using the second thick film portion of the second correction pattern And a second etching step of forming the second recess and forming the first recess using the first thick film portion of the first correction pattern. A method for etching a crystal substrate.   2. The crystal substrate etching method according to claim 1, wherein the mask is formed adjacent to each other so that the first recess and the second recess communicate with each other.   As the first thick film portion and the second correction pattern, a region other than the start portion on the outer periphery is surrounded by a plane along the (111) plane of the crystal plane orientation of the crystal substrate, and other than the start portion 3. The method for etching a crystal substrate according to claim 1, wherein a corner portion having an angle smaller than 180 degrees is not defined.

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