JP2008264902A - Silicon structure and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon structure and its manufacturing method, compatibly suppressing both occurrence of the sticking phenomenon and generation of waste etc. from dicing. <P>SOLUTION: The silicon structure 100 is configured so that its overlayer 30 is formed on a base layer 12 with an intermediate layer 14 interposed. The overlayer 30 has three sections, i.e. a movable part 18, a stationary part 16, and a dicing region 20. As an intermediate layer 14a in a projected shaped is formed on a substrate directly under the movable part, there is no risk of the movable part being stuck to the substrate. Because the intermediate layer in the dicing region 20 has been removed, laser dicing is conducted, and generation of the waste etc. is suppressed. Thus suppressing occurrence of the sticking phenomenon and suppressing the generation of the waste etc. from dicing are performed compatibly. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a silicon structure constituting an acceleration sensor, an angular velocity sensor, and the like, and a method for manufacturing the silicon structure.

  A technique for manufacturing a silicon structure that functions as various sensors by processing a silicon substrate to form a fixed part and a movable part has been developed. This technology often uses an SOI substrate in which an upper layer of silicon, an intermediate layer of silicon oxide, and a base layer are stacked. In the manufacturing process of the silicon structure, the intermediate layer located immediately below the upper layer in the range to be the movable part is removed by wet etching to produce a movable part in which the upper layer is separated from the base layer. A sticking phenomenon in which the upper layer and the base layer are attracted by the surface tension and the upper layer and the base layer stick together is likely to occur.

  In order to suppress the occurrence of the sticking phenomenon, a method for suppressing sticking between the upper layer and the base layer forming the movable part by leaving a protruding oxide film projecting toward the movable part immediately below the movable part is proposed. Has been. This is disclosed in Patent Document 1.

JP 2001-102597 A

In the manufacturing process of a silicon structure, a plurality of silicon structures are often manufactured from one SOI substrate. Therefore, a process for dicing the SOI substrate is required. Dust is easily generated in the process of dicing the SOI substrate. When dust is generated, the generated dust tends to hinder the operation of the silicon structure.
If the method of dicing by irradiating the base layer with laser (method of dicing the base layer by irradiating the laser to grow a fragile modified layer in the base layer in the direction perpendicular to the base layer) Can be suppressed. However, if a silicon oxide intermediate layer remains on the surface of the base layer during laser dicing, the base layer cannot be diced with a laser. In order to perform laser dicing, it is necessary to remove the silicon oxide intermediate layer from the surface of the base layer at a position along the dicing line.
However, in order to suppress the occurrence of the sticking phenomenon, a silicon oxide protrusion protruding toward the upper layer is left immediately below the upper layer constituting the movable part, and the silicon oxide is exposed from the surface of the base layer at a position along the dicing line. It is difficult to achieve both removal of the intermediate layer.

  FIG. 2 shows an example of a silicon structure. The silicon structure is manufactured using an SOI substrate in which the upper layers 16 and 18 of silicon, the intermediate layer 14 of silicon oxide, and the base layer 12 are stacked. FIG. 22 shows a dicing line, which manufactures a plurality of silicon structures from one SOI substrate by dicing one SOI substrate. Each silicon structure includes a fixed portion in which the upper layer 16 is fixed to the base layer 12 through the intermediate layer 14 and a movable portion (in which the intermediate layer immediately below is removed and free from the base layer 12). The upper layer) 18 is provided. The upper layer 18 separated from the base layer 12 is connected to and supported by the upper layer 16 fixed to the base layer 12 via the intermediate layer 14 at a position not shown, and is a position separated from the base layer 12. Maintained in relationship. A plurality of holes are formed in the upper layer 18 constituting the movable part, and the intermediate layer 14 immediately below the upper layer 18 constituting the movable part is removed by the entry of the etching agent from the holes.

FIG. 17A shows a cross section of a conventional silicon structure 200. The silicon structure 200 finishes the etching of the intermediate layer 14 with the silicon oxide protrusions 14a protruding toward the upper layer 18 remaining immediately below the upper layer 18 that is separated from the base layer 12 and constitutes the movable portion. 1 shows a silicon structure manufactured in Since the silicon oxide protrusions 14 a are formed immediately below the upper layer 18 that becomes the movable portion, the upper layer 18 does not stick to the base layer 12. However, if the etching of the intermediate layer 14 is completed with the silicon oxide protrusions 14a remaining, the silicon oxide intermediate layer 14 remains on the surface of the base layer 12 in the range along the dicing line 22 (dicing region 20). Therefore, the base layer 12 cannot be laser diced.
FIG. 17B shows a cross-sectional view of a silicon structure 300 manufactured by etching the intermediate layer 14 until the silicon oxide intermediate layer 14 is completely removed in the dicing region 20. If the intermediate layer 14 is etched until the silicon oxide intermediate layer 14 is completely removed in the dicing region 20, the silicon oxide intermediate layer immediately below the upper layer 18 that becomes the movable portion is completely removed, and the protrusion 14 a remains. I can't let you. It is not possible to prevent the occurrence of a sticking phenomenon in which the upper layer 18 constituting the movable part sticks to the base layer 12.
In the conventional technique, it is difficult to achieve both the suppression of the occurrence of the sticking phenomenon by leaving the protrusions 14a and the dicing region 20 to completely remove the silicon oxide intermediate layer 14 and enable dicing with a laser. It is.

  In the present invention, the protrusion 14a for suppressing the occurrence of the sticking phenomenon remains, and on the other hand, in the dicing region 20, the intermediate structure that can interfere with laser dicing can be completely removed. The purpose is to provide. Another object of the present invention is to provide a silicon structure having a structure that can be manufactured by the method.

The method for manufacturing a silicon structure of the present invention relates to a method for manufacturing a plurality of silicon structures by dicing a single SOI substrate in which an upper layer of silicon, an intermediate layer of silicon oxide, and a base layer are stacked. The manufacturing method includes a first etching step in which an upper layer is removed by anisotropic etching within a range extending along a dicing line for dicing the SOI substrate into a plurality of silicon structures. In addition, the first layer is removed by anisotropic etching at the same time as removing the upper layer in the range in which the fixed portion and the movable portion forming the silicon structure are separated and in the minute range distributed in the contour of the movable portion. A second etching step is provided for thinning the intermediate layer exposed in the etching step. Further, the intermediate layer is isotropically etched from the range where the upper layer was removed in the first etching step and the second etching step, the intermediate layer in the range where the upper layer was removed in the first etching step, the fixed portion and the movable portion. At the same time as the intermediate layer in the range to be separated is completely removed, in the contour of the movable part, the silicon oxide protrusions that protrude toward the upper layer and remain below the upper layer remain between the adjacent minute ranges. A third etching step for removing the intermediate layer. Further, the method includes a step of dicing the base layer by irradiating the base layer with a laser along the dicing line from which the intermediate layer has been removed.
The upper layer material is silicon and the intermediate layer material is silicon oxide, but the base layer material is not limited.

In this method, first, the upper layer of a range (dicing region) extending along the dicing line is removed by etching. Next, the upper layer in the range where the fixed part and the movable part are separated and the minute range which is dispersedly arranged in the outline of the movable part is removed by etching. By the latter etching, the intermediate layer in the dicing region is also etched and thinned.
Next, the intermediate layer is etched. The intermediate layer etching step is completed in a state in which a protruding portion that protrudes toward the upper layer but does not reach the upper layer remains immediately below the upper layer serving as the movable portion. Since the intermediate layer of the dicing region is thinned prior to etching the intermediate layer, even if the intermediate layer etching step is finished with the protrusion remaining directly under the upper layer that becomes the movable part, The intermediate layer in the dicing area can be completely removed.
In the silicon structure manufactured through the above steps, the upper layer sticks to the base layer because there is a protruding portion that does not reach the upper layer but protrudes toward the upper layer immediately below the upper layer constituting the movable portion. There is nothing. Further, since the intermediate layer of silicon oxide is completely removed in the dicing region, the base layer can be laser-diced in the dicing region. The occurrence of the sticking phenomenon can be suppressed, and the generation of dust accompanying dicing can be suppressed.

  The silicon structure realized by the present invention includes a base layer, a fixed portion formed of a silicon layer supported on the surface of the base layer via an intermediate layer of silicon oxide, and extending from the fixed portion. The movable part is formed of a silicon layer free from the base layer. In the case of the silicon structure realized in the present invention, the base layer is exposed at least in the range along the outer periphery of the silicon structure, and a plurality of silicon layers constituting the movable part reach the back surface from the front surface. Through-holes are formed, and on the back surface of the silicon layer, a silicon oxide protrusion that protrudes from the base layer toward the silicon layer and does not reach the silicon layer remains.

  The fixing portion is supported on the substrate via the intermediate layer. The silicon layer constituting the movable part is separated from the base layer, and the upper layer constituting the movable part can be displaced with respect to the base layer. The upper layer constituting the movable part extends from the fixed part and is supported by the base layer via the fixed part. Since the silicon oxide protrusions that do not reach the silicon layer remain between the upper layer and the base layer that constitute the movable part, the upper layer and the base layer that constitute the movable part do not stick to each other. In the silicon structure of the present invention, the base layer is exposed in a region where dicing is performed to separate a plurality of silicon structures, and laser dicing can be performed.

  In the silicon structure of one embodiment of the present invention, the fixed electrode is formed in the fixed portion, and the movable electrode is formed in the movable portion. When the fixed electrode and the movable electrode are made to face each other, a capacitor can be formed by both of them, and the magnitude of the physical quantity by which the movable part is moved can be detected using the change in capacitance.

  According to the present invention, in a silicon structure such as an acceleration sensor or a yaw rate sensor, it is possible to suppress the occurrence of a sticking phenomenon and suppress the generation of dust accompanying dicing. Such a silicon structure can be manufactured.

(First embodiment)
FIG. 2 is a perspective view of the silicon structure 100 of this embodiment. This perspective view is common to the conventional silicon structures 200 and 300 shown in FIG. FIG. 1 shows a cross section taken along line II in FIG. The silicon structure 100 is manufactured using an SOI substrate on which upper layers 16 and 18 of silicon, an intermediate layer 14 of silicon oxide, and a base layer 12 are stacked.
The upper layer 16 constituting the fixing portion is fixed to the base layer 12 via the intermediate layer 14. The upper layer 18 constituting the movable part extends from the upper layer 16 constituting the fixed part at a position not shown.
A plurality of holes 18a are formed in the upper layer 18 constituting the movable part, and has a mesh structure. The intermediate layer 14 immediately below the upper layer 18 constituting the movable portion is removed by the etching agent that has entered through the plurality of holes 18a. The upper layer 18 constituting the movable part is separated from the base layer 12. 1 and FIG. 2, the number of holes 18a formed in the movable portion 18 is different, but in FIG. 1, a large number of holes are drawn for easy understanding.
In the dicing region 20 extending along the dicing line 22, the silicon oxide intermediate layer 14 is completely removed, and the base layer 12 can be diced by irradiating a laser along the dicing line 22.
The silicon structure 100 operates as a yaw rate sensor. That is, if the upper layer 18 constituting the movable part is vibrated in the X direction, the upper layer 18 is displaced in the Y direction in the figure when the silicon structure 100 rotates around the Z axis in the figure. By detecting the amount of displacement, the angular velocity around the Z axis can be detected.

  FIG. 1 shows a cross-sectional view of the silicon structure 100. The silicon structure 100 is formed of an SOI substrate in which an upper layer 30 of a silicon single crystal is laminated on a silicon single crystal base layer 12 with an intermediate layer 14 of silicon oxide interposed therebetween. As shown in FIG. 2, the upper layer 30 is separated into an upper layer 18 that constitutes a movable portion and an upper layer 16 that constitutes a fixed portion. In the dicing region 20, the upper layer 30 is removed. The upper layer 30 is also removed in the region between the upper layer 18 constituting the movable part and 16 constituting the fixed part. The upper layer 30 is also removed from the hole 18 a formed in the movable portion 18.

  The back surface of the upper layer 16 constituting the fixing portion is fixed to the base layer 12 via the intermediate layer 14. On the back surface of the upper layer 18 constituting the movable portion, the intermediate layer 14 is removed with the protrusions 14a remaining. The protrusion 14 a does not reach the upper layer 18. The upper layer 18 is free from the base layer 12 and can be displaced with respect to the base layer 12. The protrusions 14a are formed at beam-shaped intersections extending between the through holes 18a shown in FIG. When the upper layer 18 is displaced toward the base layer 12, the protrusion 14 a comes into contact with the intersection of the beam shape, so that the base layer 12 does not stick to the upper layer 18. In the dicing area, the intermediate layer 14 is completely removed. In the region 28 where the upper layer 16 constituting the fixed portion and the upper layer 18 constituting the movable portion are separated, the intermediate layer 14 is completely removed. Since the intermediate layer 14 is completely removed in the dicing region 20, the base layer 12 can be laser-diced. It is possible to achieve both suppression of the sticking phenomenon and generation of dust.

A method for manufacturing the silicon structure 100 is shown in FIGS. An SOI substrate is prepared in which the upper layer 30 is laminated on the surface of the base layer 12 via the intermediate layer 14 (FIG. 3).
Next, an oxide film 24 is formed on the upper layer 30 by using thermal oxidation or CVD (FIG. 4).
Next, a pattern of the first resist film 26 is formed on the oxide film 24 by photolithography (FIG. 5). The first resist film 26 is formed only in a region where the upper layer 30 is desired to remain.
Next, the oxide film 24 in a range not covered with the first resist film 26 is removed by dry etching (FIG. 6).
Next, the remaining first resist film 26 is removed by ashing or acid cleaning (FIG. 7).
Next, the 2nd resist film 36 is apply | coated and the pattern opened only by the dicing area | region 20 is formed (FIG. 8).
Next, using the second resist film 36 as a mask, the upper layer 30 of the dicing region 20 is dry-etched to expose the intermediate layer 14 in the dicing region 20 (FIG. 9). The Bosch method can be used for dry etching. Since the dicing region 20 is usually a large area, needle-like residues due to oxygen precipitates or the like are likely to be generated in the upper layer 30 during etching, but in this embodiment, the second resist film 36 is used as a mask. Since carbon is supplied from the second resist film 36, generation of needle-like residues can be prevented.
Next, the second resist film 36 is removed by ashing (FIG. 10).
Next, the upper layer 30 is etched again using the patterned oxide film 24 as a mask. At this time, the upper layer 30 in the range 28 separating the fixed portion 16 and the movable portion 18 and the range of the through hole 18 a formed in the movable portion 18 is etched. At this time, the intermediate layer 14 in the dicing region 20 is also etched and thinned. (FIG. 11). In FIG. 11, the thinned intermediate layer is indicated by 14b.
Next, the oxide film 24 and the intermediate layer 14 are wet-etched with a chemical solution such as HF. A chemical solution such as HF enters the through hole 18a and the like and reaches the intermediate layer. At this time, since the intermediate layer 14b in the dicing region 20 is thinned in the process of FIG. 11, the etching process of the intermediate layer 14 is performed in a state where the sticking prevention protrusion 14a remains immediately below the movable portion 18. Even when the process is completed, the intermediate layer 14 in the dicing region 20 can be completely removed (FIG. 12).
Next, the intermediate layer removal process from the step of FIG. 11 to the step of FIG. 12 is shown in FIGS. In FIGS. 13 to 16, the intermediate layer 14 is shown enlarged for easy understanding.
FIG. 13 is an enlarged view of the intermediate layer 14 in the process of FIG. The intermediate layer 14 immediately below the through hole 18a is removed by etching. On the back surface of the upper layer extending between the through holes 18a, the intermediate layer is etched laterally. Below the cross point of the beam shape extending in a cross shape, the intermediate layer is etched from the four side surfaces close to the through hole. The intermediate layer is gradually reduced by etching (FIGS. 14 to 15), and the intermediate layer in the dicing region 20 is completely removed (FIG. 16). At this time, the protrusion 14a remains below the intersection of the beam shape extending in a cross shape.

  By the manufacturing method described above, the intermediate layer in the dicing region can be completely removed with the intermediate layer for suppressing sticking left immediately below the movable part. In the manufacturing process of the silicon structure, it is possible to suppress the occurrence of the sticking phenomenon and suppress the generation of dust accompanying dicing.

  The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

1 shows a cross-sectional view of a silicon structure 100 of the present invention. A perspective view of a silicon structure 100 is shown. A method for manufacturing the silicon structure 100 will be described. A method for manufacturing the silicon structure 100 will be described. A method for manufacturing the silicon structure 100 will be described. A method for manufacturing the silicon structure 100 will be described. A method for manufacturing the silicon structure 100 will be described. A method for manufacturing the silicon structure 100 will be described. A method for manufacturing the silicon structure 100 will be described. A method for manufacturing the silicon structure 100 will be described. A method for manufacturing the silicon structure 100 will be described. A method for manufacturing the silicon structure 100 will be described. The removal process of an intermediate | middle layer is shown. The removal process of an intermediate | middle layer is shown. The removal process of an intermediate | middle layer is shown. The removal process of an intermediate | middle layer is shown. (A) and (B) show a prior art silicon structure.

Explanation of symbols

12: base layer 14, 14a, 14b: intermediate layer 16: fixed part 18: movable part 18a: through hole, through hole forming position 20: dicing region 22: dicing line 24: oxide film 26: first resist film 28: fixed 30: upper layer, silicon layer 36: second resist film 100, 200, 300: silicon structure

Claims (3)

A method of manufacturing a plurality of silicon structures by dicing a single SOI substrate in which an upper layer of silicon, an intermediate layer of silicon oxide, and a base layer are laminated,
A first etching step of removing the upper layer by anisotropic etching in a range extending along a dicing line for dicing the SOI substrate into a plurality of silicon structures;
At the same time that the upper layer is removed by anisotropic etching in a range in which the fixed portion and the movable portion forming the silicon structure are separated and in a minute range that is dispersedly arranged in the contour of the movable portion, A second etching step of thinning the intermediate layer exposed in the first etching step;
The intermediate layer isotropically etched from the range where the upper layer was removed in the first etching step and the second etching step, and the intermediate layer in the range where the upper layer was removed in the first etching step; The intermediate layer in a range separating the fixed part and the movable part is completely removed, and at the same time, it projects toward the upper layer and does not reach the upper layer between adjacent minute ranges in the outline of the movable part. A third etching step for removing the intermediate layer until the silicon oxide protrusion remains.
A method of manufacturing a silicon structure, comprising: a step of dicing the base layer by irradiating the base layer with a laser along a dicing line from which the intermediate layer has been removed. A silicon structure,
The base layer,
A fixed portion of silicon supported on the surface of the base layer via an intermediate layer of silicon oxide;
A movable part of silicon extending from the fixed part and free from the base layer;
The base layer is exposed at least in the range along the outer periphery of the silicon structure,
A plurality of through holes reaching from the front surface to the back surface are formed in the silicon layer constituting the movable part,
2. A silicon structure according to claim 1, wherein a protruding portion of silicon oxide that protrudes from the base layer toward the silicon layer and does not reach the silicon layer remains on the back surface of the silicon layer constituting the movable portion. A fixed electrode is formed on the fixed part,
A movable electrode facing the fixed electrode is formed on the movable part,
3. The silicon structure according to claim 2, wherein a magnitude of a physical quantity by which the movable portion is moved is detected using a change in capacitance between the fixed electrode and the movable electrode.

Images