JP5048633B2 - Manufacturing method of MEMS sensor - Google Patents

Description

  The present invention relates to a method for manufacturing a MEMS sensor having an anti-sticking structure.

  In a MEMS (Micro-Electro-Mechanical Systems) sensor, for example, a movable portion and a fixed portion are formed by finely processing an SOI layer constituting an SOI (Silicon on Insulator) substrate. This fine sensor is used as an acceleration sensor, a pressure sensor, a vibration gyro, or a micro relay.

  By the way, as described in the following patent document, in the MEMS sensor, a convex portion is formed on the lower surface of the movable portion (a surface facing the support substrate) to prevent sticking between the movable portion and the support substrate. Measures are taken.

Conventionally, when an attempt is made to form the convex portion using an SOI substrate having a laminated structure of a support substrate (silicon substrate), an oxide insulating layer (SIO ₂ layer) and an SOI layer (silicon substrate), for example, the following patent document also discloses: As described, when the oxide insulating layer (SiO ₂ layer) interposed between the movable part and the support substrate is removed by etching, the movable part is arranged so that the oxide insulating layer is not completely removed. The oxide insulating layer is left in a convex shape on the lower surface of the movable part.

However, the manufacturing method described above cannot easily and accurately form the convex portion on the lower surface of the movable portion. In particular, the convex portions cannot be formed properly unless various conditions such as the width of the movable portion, the film thickness of the oxide insulating layer, and the etching rate are adjusted with high accuracy comprehensively. In addition, there is a problem that the yield tends to decrease. In addition, since the movable part has to be formed wide, miniaturization of the MEMS sensor cannot be promoted.
JP 2001-102597 A JP 2004-294401 A

  Therefore, the present invention solves the above-described conventional problems, and in particular, an object of the present invention is to provide a MEMS sensor capable of forming a sticking prevention structure more easily and more accurately than the conventional one.

The manufacturing method of the MEMS sensor in the present invention is as follows:
(A) A first substrate and a second substrate are prepared, respectively, and a convex sticking prevention portion is formed on a surface of the first substrate facing the second substrate in a region to be a movable portion. Process,
(B) Next to the step (a), a step of forming an oxide insulating layer on at least one of the opposing surfaces of the first substrate or the second substrate;
(C) Next to the step (b), the step of bonding the first substrate and the second substrate;
(D) Next to the step (c) , processing the first substrate to form at least the movable part;
(E) After the step (d), the oxide insulating layer located between the movable part and the second substrate is removed to form a space between the movable part and the second substrate. Process,
It is characterized by having.

  In the present invention, as shown in the above step (a), a sticking prevention portion is formed in advance on the surface of the first substrate facing the second substrate, and then, in the step (b), the oxide insulation is formed. In the step (c) of forming a layer, the first substrate and the second substrate are bonded. After that, it is the same as the conventional process. Conventionally, for example, a convex sticking prevention portion is formed so as to leave a part of the oxide insulating layer from the state of the SOI substrate in which the first substrate and the second substrate are bonded via the oxide insulating layer. Was. On the other hand, in the present invention, the first substrate and the second substrate are prepared separately, and before the bonding, the sticking prevention portion is formed on the single first substrate. It is possible to form the sticking prevention portion more easily and with higher accuracy than in the past. Also, in the present invention, unlike the conventional case, since there is no restriction to form the movable part wide for forming the sticking prevention part, the manufacturing method can contribute to miniaturization of the MEMS sensor.

In the step (d), the first substrate is separated into the movable part and the fixed part that constitute the sensor part,
In the step (a), it is preferable that the sticking prevention portion is formed on the entire facing surface of the sensor portion. In this case, the sticking prevention part is also formed in the fixing part. Although the formation of the anti-sticking part on the fixed part is not particularly necessary, the anti-sticking part can be easily formed by restricting the formation of the anti-sticking part only to the area that becomes the movable part and the entire surface facing the sensor part. Can be formed.

  In the present invention, it is preferable that the sticking preventing portion is formed in a dot shape or a lattice shape.

  In the present invention, in the step (b), it is preferable to form an oxide insulating layer on the surface of the second substrate formed with a flat surface. Accordingly, the oxide insulating layer can be formed easily and with a substantially constant thickness, and a space with a substantially constant height can be appropriately formed between the movable portion and the second substrate.

Further, in the present invention, in the step (a), instead of the step of forming a convex sticking prevention portion on the surface of the first substrate facing the second substrate in the region that becomes the movable portion. The sticking prevention portion can be formed on the facing surface of the second substrate at a position facing at least the movable portion.

  In the present invention, in the step (a), it is preferable that the opposing surface is etched to form the convex sticking prevention portion made of the same material as the substrate. Thereby, the said convex sticking prevention part can be formed easily. Further, in the step of removing the oxide insulating layer, it is possible to appropriately leave the convex sticking prevention portion formed of the same quality as the first substrate on the opposing surface of the movable portion.

Further, in the present invention, in the step (a), instead of the step of forming a convex sticking prevention portion on the surface of the first substrate facing the second substrate in the region that becomes the movable portion. The sticking preventing portion may be formed in a concave shape on the surface of the first substrate facing the second substrate in a region that becomes at least a movable portion .

  According to the MEMS sensor manufacturing method of the present invention, it is possible to form the anti-sticking structure more easily and more accurately than the conventional method.

  FIG. 1 is a process diagram showing a method for manufacturing the MEMS sensor of this embodiment. Each process drawing of FIG. 1 is shown with sectional drawing cut | disconnected and shown from the thickness direction.

  In the process of FIG. 1A, a first substrate 1 made of silicon and a second substrate 2 made of silicon constituting a MEMS sensor are prepared individually.

  As shown in FIG. 1A, a plurality of convex sticking preventing portions 4 are formed on the lower surface (the surface facing the second substrate 2) 1a of the first substrate 1 by etching. The sticking prevention unit 4 may be formed at least on the lower surface of the region serving as the movable unit 5. In this embodiment, the sticking prevention unit 4 is also formed on the lower surface of the region serving as the fixed unit 6. .

  In FIG. 1A, the fine convex sticking preventing portion 4 is formed by etching the lower surface 1a of the first substrate 1. Therefore, the sticking prevention unit 4 is formed of the same silicon as the first substrate 1. Thereby, the sticking prevention part 4 can be formed easily. The convex sticking prevention portion 4 can be formed of a material different from that of the first substrate 1 and the second substrate 2. For example, convex portions of different materials can be formed on the lower surface 1a of the first substrate 1 by sputtering. At this time, it is necessary to form the convex portion with a material that is not removed together with the oxide insulating layer 3 in the step of removing the oxide insulating layer 3 in FIG.

  In the step of FIG. 1A, an alignment key may be formed on the lower surface 1a of the first substrate 1, for example, separately from the formation of the sticking prevention portion 4. For example, a concave alignment key is formed on the lower surface 1a. Note that the alignment key is formed at a position away from the region to be the sensor unit 7 composed of the movable unit 5 and the fixed unit 6.

  Next, in the step of FIG. 1B, the surface of the first substrate 1 is thermally oxidized to form an oxide insulating layer 3. Note that the oxide insulating layer 3 may be formed by sputtering, CVD, or the like, but it is preferable to form the oxide insulating layer 3 by thermal oxidation.

  Next, in the step shown in FIG. 1C, the first substrate 1 and the second substrate 2 are bonded. As a bonding method, room temperature bonding, thermocompression bonding, or the like can be used.

  In the step of FIG. 1C, the upper surface 1b of the first substrate 1 is ground until it reaches a predetermined thickness. For example, CMG or CMP, or CMG and CMP are performed on the upper surface 1b of the first substrate 1.

  1C, the alignment key (not shown) described above is exposed from the upper surface 1b of the first substrate 1.

  Subsequently, in the process shown in FIG. 1D, the first substrate 1 is separated into a movable part 5 and a fixed part 6 constituting the sensor part 7 using deep RIE (Deep RIE). In this embodiment, the first substrate 1 around the sensor unit 7 is left as the frame 8.

  In the present embodiment, the positions where the movable portion 5 and the fixed portion 6 are formed can be adjusted with high accuracy by the alignment key.

  1D, the oxide insulating layer 3 between the sensor unit 7 and the second substrate 2 is removed by an isotropic etching process using wet etching or dry etching. In FIG. 1D, the oxide insulating layer 3 to be removed is indicated by a dotted line.

  At this time, since the convex sticking prevention portion 4 formed on the lower surface 5a of the movable portion 5 is formed of silicon that is the same quality as the movable portion 5, it remains without being removed together with the oxide insulating layer 3. In this embodiment, the convex sticking prevention portion 4 is also left on the lower surface 6 a of the fixing portion 6.

  Then, by removing the oxide insulating layer 3 between the movable part 5 and the second substrate 2, a space 9 can be formed between the movable part 5 and the second substrate 2.

  Further, as shown in FIG. 1D, since the frame body 8 is formed wide, a part of the oxide insulating layer 3 interposed between the frame body 8 and the second substrate 2 is partially eroded. Left behind. Therefore, the frame 8 is fixed to the second substrate 2 via the oxide insulating layer 3.

  The movable portion 5 is provided with a thin elastic support portion (not shown) formed from the first substrate 1 and a wide anchor portion (not shown). The elastic support portion also floats from the surface of the second substrate 2 like the movable portion 5, but the anchor portion is connected to the second substrate 2 via the oxide insulating layer 3 like the frame body 8. Fixedly supported. Therefore, the movable part 5 and the elastic support part can be appropriately maintained in a state of floating inside from the surface of the second substrate 2.

  Further, as shown in FIG. 1D, a wide anchor portion (not shown) formed from the first substrate 1 is also connected to the fixed portion 6. The anchor portion is fixedly supported on the second substrate 2 via the oxide insulating layer 3 in the same manner as the frame body 8. Therefore, even if the oxide insulating layer 3 between the fixing portion 6 and the second substrate 2 is removed as shown in FIG. 1D, the fixing portion 6 is floated from the surface of the second substrate 2. Can be properly maintained.

  The movable portion 5 is a region that is displaced in response to a physical quantity change. For example, the MEMS sensor shown in FIG. 1D is an acceleration sensor, and the movable portion 5 is displaced by receiving a force (inertial force) accompanying the acceleration. The acceleration can be detected based on the capacitance changed between the movable part 5 and the fixed part 6 due to the displacement of the movable part 5.

  In the present embodiment, a convex sticking prevention portion 4 is formed on the lower surface 5 a of the movable portion 5. For this reason, even when a strong physical quantity in the downward direction is added to the movable part 5 and the movable part 5 comes into contact with the surface of the second substrate 2, the contact area between the movable part 5 and the second substrate 2 is effective. Therefore, the sticking that the movable part 5 is attracted to the surface of the second substrate 2 can be appropriately prevented.

A characteristic configuration of the present embodiment will be described.
In the present embodiment, as shown in FIG. 1A, the first substrate 1 and the second substrate 2 are separately prepared as a single unit, and a convex shape is formed in advance on the lower surface 1a of the first substrate 1. The sticking prevention part 4 is formed. Subsequently, the oxide insulating layer 3 is formed in the step of FIG. 1B, and the first substrate 1 and the second substrate 2 are bonded in the step of FIG. 1C. After that, it is the same as the conventional process. Conventionally, for example, the sticking prevention portion is formed so as to leave a part of the oxide insulating layer from the state of the SOI substrate in which the first substrate and the second substrate are bonded via the oxide insulating layer. . On the other hand, in the present embodiment, the first substrate 1 and the second substrate 2 are prepared separately, and the sticking preventing portion 4 is attached to the single first substrate 1 before joining them. Therefore, the sticking prevention portion 4 can be formed more easily and with higher accuracy than in the prior art. Also, in the present embodiment, unlike the prior art, there is no restriction to form the movable part wide for forming the sticking prevention part 4, so that the manufacturing method can contribute to miniaturization of the MEMS sensor. .

  In FIG. 1B after the step of FIG. 1A, the oxide insulating layer 3 is formed on the surface of the first substrate 1, but the surface of the second substrate 2 is oxidized as shown in FIG. The insulating layer 3 can be formed.

  At this time, since the upper surface 2a (the surface facing the first substrate 1) 2a of the second substrate 2 is a flat surface, the oxide insulating layer 3 can be formed on the upper surface 2a with a simple and substantially constant thickness. Then, as shown in FIG. 2B, the first substrate 1 and the second substrate 2 are bonded by room temperature bonding or the like, and the upper surface 1b of the first substrate 1 is subjected to a grinding process. In FIG. 2B, the oxide insulating layer 3 formed on the lower surface and side surfaces other than the upper surface 2a of the second substrate 2 is removed in the drawing, but if there is no problem as a product, the oxide insulating layer 3 is left. It is also possible.

  After the step of FIG. 2B, the step of FIG. 1D is performed. In FIG. 2A, since the oxide insulating layer 3 can be formed with a substantially constant thickness, the removal of the oxide insulating layer 3 in the step of FIG. 1D results in a substantially constant height between the movable portion 5 and the second substrate 2. The space 9 can be formed.

  Further, as shown in FIG. 1B, when the oxide insulating layer 3 is formed by thermally oxidizing the surface of the first substrate 1, the width and height of the convex sticking prevention portion 4 are as shown in FIG. ) Is slightly smaller than after the formation of the sticking prevention portion 4. On the other hand, when the second substrate 2 side is thermally oxidized as shown in FIG. 2A, the convex anti-sticking portion 4 formed on the first substrate 1 can be maintained in the size after formation. .

  In the present embodiment, the oxide insulating layer 3 can be formed on both the first substrate 1 and the second substrate 2.

  In another embodiment of FIG. 3, instead of FIGS. 1 and 2, the sticking prevention unit 4 is formed on the upper surface 2 a of the second substrate 2 (the surface facing the first substrate 1). Thereafter, steps similar to those shown in FIGS. 1B to 1D (or FIGS. 2A and 2B instead of FIGS. 1B and 1C) may be performed. In the form shown in FIG. 3, all the formed sticking prevention portions 4 are left as they are.

  In another embodiment of FIG. 4, the concave sticking prevention portion 10 is formed on the lower surface 5 a of the movable portion 5. In FIG. 4, the concave sticking prevention portion 10 is also formed on the lower surface 6 a of the fixing portion 6. However, as in FIG. 1D, the formation of the sticking prevention portion 10 on the lower surface 6 a of the fixing portion 6 is essential. Not.

  Thus, even when the sticking prevention unit 10 is concave, when the movable unit 5 is applied with a strong physical quantity in the downward direction and the movable unit 5 contacts the surface of the second substrate 2, Since the contact area between the second substrates 2 can be made very small, sticking can be prevented appropriately.

  The planar form of the sticking prevention unit will be described with reference to FIGS. 5, 6, and 8. FIG. 5 is a schematic view of the MEMS sensor of the present embodiment as viewed from above, and FIG. 6 is a partially enlarged cross-sectional view of the MEMS sensor taken along the line AA in FIG.

  The MEMS sensor in FIG. 5 is an acceleration sensor. As shown in FIGS. 5 and 6, the fixing portion 20 extends from the anchor portion 21 in the illustrated X direction, and extends in the illustrated Y direction from both side surfaces of the supporting arm portions 22 and 23. And a plurality of fixed electrodes 24 and 25 arranged at predetermined intervals in the X direction in the figure. As shown in FIG. 6, the anchor portion 21 is fixedly supported on the second substrate 29 via the oxide insulating layer 30.

  The movable portion 26 includes fixed electrodes 24 and 25 and movable electrodes 27 and 28 arranged alternately in the X direction. In FIG. 5, illustration of an elastic support portion and an anchor portion that are provided continuously with the movable portion 26 is omitted.

  The movable part 26 and the fixed part 20 constitute a sensor part 35. As shown in FIG. 5, a frame 32 is formed around the sensor unit 35 with a space therebetween. As shown in FIG. 6, the frame body 32 is fixedly supported on the second substrate 29 via the oxide insulating layer 30.

  As indicated by a dotted line in FIG. 5, a large number of dot-like (dot-like) sticking prevention portions are formed in plan view. These sticking prevention parts 31 are formed, for example, on the lower surface of the first substrate (the surface facing the second substrate) for forming the sensor unit 35 and the frame body 32.

  The sticking prevention units 31 illustrated in FIG. 5 are scattered throughout the entire sensor unit 35. Among the sticking prevention parts 31, the sticking prevention part 31 formed on the lower surface of the movable part 26 and the fixed part 20 is left as shown in FIG. 6, and the other sticking prevention parts 31 are left in the step of FIG. Removed.

  In FIG. 5, a large number of sticking prevention portions 31 are regularly arranged, but may be formed at random. Further, in the step of forming the sticking prevention part 31, the movable part 26 can be controlled by appropriately regulating the interval between the sticking prevention parts 31 and the size of each sticking prevention part 31 without specifying the region to be the movable part 26. It is possible to reliably form (leave) the sticking prevention portion 31 on the lower surface of the substrate.

  Incidentally, as shown in FIG. 6, the anchor portion 21 is a portion that is fixedly supported on the second substrate 29 via the oxide insulating layer 30, so that the lower surface (second portion) of the anchor portion 21 is secured to ensure a wide bonding area. The surface facing the substrate 29 is preferably a flat surface. Therefore, if the region of the anchor portion 21 can be specified in advance in the step of forming the sticking prevention portion 31, it is preferable to restrict the sticking prevention portion 31 from being formed in the region that becomes the anchor portion 21.

  5 and 6, the sticking prevention portion 31 may be formed in a concave shape as shown in FIG.

Further, as shown in FIG. 7, the sticking preventing portion 40 can be formed in a lattice shape in a plan view. At this time, in the step of forming the sticking prevention part 40, without specifying the region to be the movable part 26, by appropriately regulating the interval between the narrow strips, the width of the narrow strips, etc. It is possible to reliably form (leave) the sticking prevention portion 40 on the lower surface of the movable portion 26. The lattice-like sticking prevention portion 40 shown in FIG. 7 may be convex or concave.
The shape of the sticking prevention unit may be other than that shown in FIGS.

  The MEMS sensor of this embodiment is applicable to all physical quantity sensors other than the acceleration sensor.

Process drawing (cross-sectional view) of the MEMS sensor in this embodiment, The process drawing (sectional drawing) of the MEMS sensor in this embodiment which changed a part of FIG. 1, The process drawing (sectional drawing) of the MEMS sensor in this embodiment which changed a part of FIG. 1, Sectional drawing of the MEMS sensor of another this embodiment, The schematic diagram which looked at the MEMS sensor of this embodiment from the plane, The partial expanded sectional view of the MEMS sensor cut | disconnected in the height direction from the AA line of FIG. The schematic diagram which looked at the MEMS sensor of another this embodiment different from FIG. 5 from the plane,

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st board | substrate 2, 29 2nd board | substrate 3, 30 Oxide insulation layer 4, 10, 31, 40 Sticking prevention part 5, 26 Movable part 6, 20 Fixed part 7, 35 Sensor part 8, 32 Frame 9 Space 21 Anchor Club

Claims (8)

(A) A first substrate and a second substrate are prepared, respectively, and a convex sticking prevention portion is formed on a surface of the first substrate facing the second substrate in a region to be a movable portion. Process,
(B) Next to the step (a), a step of forming an oxide insulating layer on at least one of the opposing surfaces of the first substrate or the second substrate;
(C) Next to the step (b), the step of bonding the first substrate and the second substrate;
(D) Next to the step (c) , processing the first substrate to form at least the movable part;
(E) After the step (d), the oxide insulating layer located between the movable part and the second substrate is removed to form a space between the movable part and the second substrate. Process,
A method for manufacturing a MEMS sensor, comprising: In the step (d), the first substrate is separated into the movable part and the fixed part constituting the sensor part,
The method of manufacturing a MEMS sensor according to claim 1, wherein in the step (a), the sticking prevention portion is formed on the entire facing surface of the sensor portion.   3. The method for manufacturing a MEMS sensor according to claim 1, wherein, in the step (a), the sticking prevention portion is formed in a dot shape in a plan view.   3. The method for manufacturing a MEMS sensor according to claim 1, wherein in the step (a), the sticking prevention portion is formed in a lattice shape in a plan view.   5. The method for manufacturing a MEMS sensor according to claim 1, wherein, in the step (b), an oxide insulating layer is formed on an opposing surface of the second substrate formed as a flat surface. In the step (a), instead of the step of forming a convex anti-sticking portion on the surface of the first substrate that faces at least the movable portion facing the second substrate, the anti-sticking portion 5. The method of manufacturing a MEMS sensor according to claim 1, wherein at least a surface of the second substrate is formed at a position facing the movable portion.   The method for manufacturing a MEMS sensor according to claim 1, wherein in the step (a), the convex surface is formed by etching the facing surface to form the convex sticking prevention portion made of the same material as the substrate. In the step (a), instead of the step of forming a convex anti-sticking portion on the surface of the first substrate that faces at least the movable portion facing the second substrate, the anti-sticking portion The method for manufacturing a MEMS sensor according to claim 1, wherein the first substrate is formed in a concave shape on a surface facing at least the second substrate in a region to be a movable portion of the first substrate .

Images