JP2021194740A - Manufacturing method of MEMS device and MEMS device - Google Patents

Abstract

To provide a manufacturing method of a MEMS device having high reliability to wiring, while suppressing increase of a line width which may cause crosstalk; and to provide a MEMS device.SOLUTION: Wiring 25 has a lower side surface line part 35, a step line part 36 and an upper side surface line part 37 formed on a lower side surface 29, an inclined plane 32 and an upper side surface 30, respectively. In an etching mask, a line width of an inclined mask part corresponding to the step line part 36 is set wider than a line width corresponding to the lower side surface line part 35 and the upper side surface line part 37.SELECTED DRAWING: Figure 3A

Description

The present invention relates to a method for manufacturing a MEMS device such as an optical deflector (Micro Electro Mechanical Systems) and a MEMS device.

In the optical deflector manufactured as a MEMS device, wiring is formed on the surface side in order to supply a drive voltage to the piezoelectric actuator. Since the surface side of the optical deflector has a step due to the lamination of the piezoelectric film layer or the like, the wiring has an inclined line portion on the surface of the inclined surface of the step.

On the other hand, the wiring of the MEMS device is manufactured by using photolithography in the same manner as the semiconductor element.

US Pat. In the method, in the portion where the width tends to be narrowed, the patterning line of the photomask for the portion is made into a curved line or a polygonal line so that the desired line width is secured even if the constriction occurs.

Patent Document 2 discloses a semiconductor device that prevents the surface from becoming uneven due to wiring. According to the semiconductor device, a groove is formed on the surface and wiring is at least partially embedded in the groove so that the surface is smoothed. In that case, the wiring will pass through the step of the groove when entering and exiting the groove, and the wiring is likely to be broken. As a countermeasure, in Patent Document 2, in wiring, the line width of a predetermined line portion including a step is made wider than the line width of the line portions before and after the step.

Patent Document 3 discloses a semiconductor device having a step on the surface side and wiring extending through an inclined surface of the step. In the semiconductor device, the wiring is thickened (increasing the line width or wiring thickness) at the shoulder portion, that is, the end portion on the inclined surface side of the upper surface that has climbed up the inclined surface to prevent disconnection. ..

It should be noted that widening the line width over the entire line is effective as a countermeasure against disconnection. However, this increases the capacitance between the wiring and the board and increases crosstalk. Therefore, it is desirable that the line width on the surface side of the MEMS device is as narrow as possible within the range in which disconnection can be prevented. Further, connecting the substrate to the ground for crosstalk suppression increases the complexity of the configuration and the cost.

Japanese Unexamined Patent Publication No. 62-280890 Japanese Patent No. 3895507 Japanese Unexamined Patent Publication No. 2009-2503035

When manufacturing a MEMS device using photolithography, the present inventor generates scattered light on an inclined surface on the surface side of the MEMS device, and etches for the secondary exposure of the photoresist by the scattered light. It was found that sometimes the line width is reduced in and near the inclined surface, which is likely to lead to disconnection.

Patent Documents 1 to 3 do not disclose patterning that copes with scattered light from an inclined surface during photolithography.

That is, Patent Document 1 deals with the reduction of the line width due to over-etching and side etching even though the patterning is normal. The wiring of Patent Document 1 does not narrow only the line portion of the inclined surface, but widens the entire length of the wiring. This leads to an increase in crosstalk.

The wiring of the MEMS device of Patent Document 2 is wide on the surface of the step as the side wall of the groove. However, the grooves are formed to at least partially embed the wiring that causes the bumps for smoothing the surface of the MEMS device. That is, if the depth of the groove is larger than the thickness of the wiring or the width of the groove is larger than the line width, the location of the groove may be dented from the surroundings, which hinders the smoothing of the surface of the MEMS device. In other words, the width of the groove is approximately equal to the line width. At such a step in the groove, scattered light that leads to the secondary exposure of the photoresist does not occur.

Patent Document 3 widens the shoulder portion, that is, the line portion at the end portion of the upper surface on the inclined surface side in the wiring. It does not widen the line portion on the inclined surface in the wiring.

An object of the present invention is to provide a method for manufacturing a MEMS device and a MEMS device having high reliability in terms of wiring, while suppressing an increase in line width that causes crosstalk.

The method for manufacturing a MEMS device of the present invention is as follows.
A substrate portion having an inclined surface which is a surface of an upper surface, a lower surface, and a step between the upper surface and the lower surface, and wiring extending between the upper surface and the lower surface. It is a manufacturing method of a MEMS device equipped with
The first step of forming a metal film having a thickness smaller than the step as a material for the wiring on the substrate portion.
The second step of applying the photoresist on the surface of the metal film and
The line width of the stepped mask portion including the inclined mask portion on the inclined surface and the upper and lower extending mask portions extending from the inclined surface to the upper surface and the lower surface, respectively, is the inclined mask portion. A third step of patterning the photoresist so as to be wider than the line width of the upper surface mask portion and the lower surface mask portion extending on the upper surface and the lower surface, respectively, to form an etching mask. When,
The fourth step of etching the metal film with the etching mask to form the wiring, and
To prepare for.

According to the present invention, in the etching mask in the third step, the line width of the step mask portion is wider than the line width of the lower surface mask portion and the upper surface mask portion. As a result, in the etching of the metal film in the fourth step, even if the photoresist is secondarily exposed by the scattered light from the inclined surface, the metal film of the wiring has a sufficient line width, and the inclined surface and its neighboring surface are secured. It is possible to prevent disconnection of the upper wiring.

According to the present invention, since the increase in the wiring width is limited to the range of the inclined surface, it is possible to omit the installation of the ground wire for connecting the substrate to the ground.

Preferably, in the method for manufacturing a MEMS device of the present invention.
The boundary between the step mask portion and the lower surface mask portion is separated from the lower end of the inclined surface in the line direction by a length of 1.6 times or more the step.

According to this configuration, a wide wiring range can be appropriately set in the line direction.

Preferably, in the method for manufacturing a MEMS device of the present invention.
The boundary between the step mask portion and the lower surface mask portion is 1.6 times the step in the line direction from the lower end of the inclined surface, and is set in advance as an alignment deviation in the patterning. It is more than the length of the sum of.

According to this configuration, the wide wiring range can be appropriately set in the line direction in consideration of the misalignment in patterning.

Preferably, in the method for manufacturing a MEMS device of the present invention.
Both ends of the line width of the step mask portion are separated from both ends of the line width of the lower surface mask portion to the outside in the line width direction by a length of 0.6 times or more the step.

According to this configuration, the line width of a wide wiring range can be appropriately set.

Preferably, in the method for manufacturing a MEMS device of the present invention.
Both ends of the line width of the step mask portion are set in advance as 0.6 times the step and an alignment deviation in the patterning from both ends of the line width of the lower surface mask portion to the outside in the line width direction. It is more than the length of the sum with a certain set value.

According to this configuration, the line width of a wide wiring range can be appropriately set in consideration of the misalignment in patterning.

Preferably, in the method for manufacturing a MEMS device of the present invention.
The photoresist is a positive type and is
The inclined surface has a plurality of semi-cylindrical side surfaces arranged along the longitudinal direction of the inclined surface with exposed crystals of the piezoelectric film of PZT.
In the semi-cylindrical side surface, the position where the scattered light is collected from the semi-cylindrical side surface in the exposure step in the third step is located on the side edge of the lower extending mask portion of the step mask portion. Has a shape.

According to this configuration, it is possible to form a constricted portion in the wiring by utilizing the scattered light from the semi-cylindrical side surface portion of the inclined surface and prevent the wiring from peeling off from the lower surface.

Preferably, in the method for manufacturing a MEMS device of the present invention.
The substrate portion has a common substrate under the upper surface and the lower surface, and further below the upper surface, there is a laminated portion laminated on the substrate and including a piezoelectric film layer. is doing.

According to this configuration, it can be appropriately implemented as a method for manufacturing a MEMS device provided with a piezoelectric membrane layer.

Preferably, in the method for manufacturing a MEMS device of the present invention.
The MEMS device is a MEMS optical deflector.

According to this configuration, it can be appropriately implemented as a method for manufacturing an optical deflector of a MEMS device.

The MEMS device of the present invention is
A substrate portion having an inclined surface which is a surface of an upper surface, a lower surface, and a step between the upper surface and the lower surface, and wiring extending between the upper surface and the lower surface. It is a MEMS device equipped with
The wiring is
A stepped line portion including an inclined extending portion on the inclined surface and an upper and lower extending portions extending from the inclined surface to the upper surface and the lower surface, respectively.
An upper surface line portion and a lower surface line portion extending from the step line portion and extending on the upper surface and the lower surface, respectively.
Equipped with
The wiring has a thickness smaller than the step over the entire length, and has a thickness smaller than that of the step.
The line width of the wiring is wider in the step line portion than in the upper surface line portion and the lower surface line portion.

According to the MEMS device of the present invention, it is possible to prevent disconnection of wiring while suppressing crosstalk.

It is a front view of a light deflector. It is a figure which shows the extension state of the wiring in A2 of FIG. It is a schematic diagram of the wiring structure on an inclined surface. It is a schematic diagram of the wiring structure as a 1st comparative example. It is a schematic diagram of the wiring structure as a 2nd comparative example. It is a schematic diagram of the wiring structure as a 3rd comparative example. It is explanatory drawing of the crosstalk in a MEMS device. It is a schematic explanatory drawing which shows the manufacturing method of a light deflector in the order of a process. It is the schematic explanatory drawing of the manufacturing method of the optical deflector which shows the process which follows the process of FIG. 5A in the process order. It is an analysis figure of the reach range of the scattered light in the cross section of a multilayer board. It is a top view explaining the reach range of the scattered light in the width direction of a wiring due to an inclined surface. It is an electron micrograph of an inclined surface. It is a figure which shows the wiring structure which has the constriction part generated by the scattered light from the semi-cylindrical side surface. It is an electron micrograph when it investigated that the constriction part was actually formed in the wiring by scattered light in a predetermined prototype. It is sectional drawing of the part corresponding to the constricted part of FIG. 9A in a multilayer board.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Needless to say, the present invention is not limited to the embodiments. The present invention can be variously modified and implemented within the scope of its technical idea. The same components are given the same reference numerals throughout the drawing.

(MEMS device)
FIG. 1 is a front view of the optical deflector 10. Here, for convenience of explaining the configuration, a three-axis coordinate system is defined. The peripheral contour of the optical deflector 10 is rectangular when viewed from the front of the optical deflector 10. The X-axis and the Y-axis are parallel to the long side and the short side of the optical deflector 10, respectively. The Z axis is parallel to the thickness direction of the optical deflector 10.

FIG. 1 shows the optical deflector 10 in a state when the operation is stopped. When the optical deflector 10 is activated, the movable portion of the optical deflector 10 is displaced from the state shown in FIG.

The MEMS optical deflector 10 includes a mirror portion 11, torsion bars 12a, 12b, inner piezoelectric actuators 13a, 13b, a movable frame 14, outer actuators 15a, 15b, and a fixed frame 16.

The mirror portion 11 is located at the center of the light deflector 10 and is circular in this example. The incident beam Bi is incident on the center O of the mirror portion 11 from a light source (not shown). The mirror portion 11 has a first rotation axis 22y and a second rotation axis orthogonal to each other at the center O due to the operation of the inner piezoelectric actuator 13 (general term for the inner piezoelectric actuators 13a and 13b) and the outer actuator 15 (general term for the outer actuators 15a and 15b). It swings back and forth around two 22x axes. As a result, the incident beam Bi is reflected by the mirror unit 11 to become the scanning beam Bs, and is emitted from the mirror unit 11. The scanning beams Bs are raster-scanned in the irradiated area.

The inner piezoelectric actuators 13a and 13b are arranged on both sides of the mirror portion 11 in the X-axis direction and are coupled to each other on the first rotation axis 22y to form an annular body. The annular body has a semicircle on both sides in the Y-axis direction and a straight contour in the middle, and surrounds the mirror portion 11.

The movable frame 14 has the same shape as the inner piezoelectric actuator 13 (general term for the inner piezoelectric actuators 13a and 13b) and surrounds the inner piezoelectric actuator 13.

The torsion bars 12a and 12b project from the mirror portion 11 in opposite directions in the Y-axis direction and extend along the first rotation axis 22y. Each torsion bar 12 (general term for torsion bars 12a and 12b) is coupled to the inner circumference of the movable frame 14 at the tip and to the inner piezoelectric actuator 13 at the intermediate portion.

The outer actuators 15a and 15b are arranged on each side in the X-axis direction with respect to the movable frame 14, and are interposed between the movable frame 14 and the fixed frame 16. The outer actuator 15 (general term for the outer actuators 15a and 15b) is composed of a plurality of cantilever 18s connected in series in an array of meander patterns. Each connecting portion 24 connects the cantilever 18s adjacent to each other in the X-axis direction to each other.

Each cantilever 18 has a dedicated piezoelectric film layer 60 (FIG. 5A), and a driving voltage is applied to the piezoelectric film layer 60 to bend the cantilever 18 in the Z-axis direction. Drive voltages having opposite phases are applied to the cantilever 18s adjacent to each other in the X-axis direction. As a result, the amount of displacement in the Z-axis direction between both ends of each cantilever 18 is added, and the movable frame 14 is reciprocated around the rotation axis parallel to the X-axis with a large deflection angle.

The electrode pads 20a and 20b are formed on the short side of the fixed frame 16. The light deflector 10 is enclosed in a package (not shown) and used. At that time, each electrode pad 20 (general term for the electrode pads 20a and 20b) is connected to the corresponding electrode on the package side by a bonding wire (not shown). Each electrode pad 20 is connected to the inner piezoelectric actuator 13 and the movable frame 14 via the wiring 25 (FIG. 2) in the optical deflector 10 to supply a drive voltage.

The operation of the light deflector 10 will be briefly described. The inner piezoelectric actuator 13 reciprocates the mirror portion 11 around the first rotation shaft 22y at a resonance frequency (for example, about 1.6 kHz) via the torsion bar 12. The outer actuator 15 reciprocates the movable frame 14 around a rotation axis parallel to the X axis at a non-resonant frequency (eg, 60 Hz). As a result, the mirror portion 11 reciprocates around the second rotation shaft 22x and the first rotation shaft 22y, respectively. When the mirror portion 11 faces the front while the optical deflector 10 is operating, the second rotation axis 22x and the first rotation axis 22y are parallel to the X axis and the Y axis, respectively.

Both the inner piezoelectric actuator 13 and the outer actuator 15 are unipolar type piezoelectric actuators.

(Internal wiring)
FIG. 2 is a diagram showing an extended state of the wiring 25 in A2 of FIG. A2 includes cantilever 18s adjacent to each other in the X-axis direction and a connecting portion 24 between them.

In FIG. 2, in order to make it easy to understand the extending state of the wiring 25 as the internal wiring, the coating layer on the surface side is peeled off in the Z-axis direction (stacking direction), and the wiring 25 is shown in an exposed state.

The cantilever 18 is raised from the connecting portion 24. As a result, the lower surface 29 as the surface of the connecting portion 24 is lower than the upper surface 30 as the surface of the cantilever 18. Then, an inclined surface 32 as a step is formed between the lower surface 29 and the upper surface 30.

(Wiring structure)
FIG. 3A is a schematic diagram of the wiring structure on the inclined surface 32. 3B-FIG. 3D is a schematic diagram of a wiring structure as a comparative example.

In FIG. 3A, the wiring 25 has a lower surface line portion 35, a step line portion 36, and an upper surface line portion 37 extending from each surface of the lower surface 29, the inclined surface 32, and the upper surface 30, respectively. .. In other words, the lower surface line portion 35 and the upper surface line portion 37 extend from the upper and lower ends of the step line portion 36 to the lower surface 29 and the upper surface 30.

The step line portion 36 has a lower extending portion 36a, an inclined extending portion 36b, and an upper extending portion 36c in order from the lower surface line portion 35 to the upper surface line portion 37. FIG. 3A includes an enlarged portion of the step line portion 36.

In order to clarify the range of the lower extending portion 36a, the inclined extending portion 36b, and the upper extending portion 36c in the step line portion 36, the boundary lines 38a, 38b, 38c, 38d are shown in FIG. 3A. There is. The boundary line 38a is a line that separates the lower surface line portion 35 and the lower extending portion 36a. The boundary line 38b extends along the lower end of the inclined surface 32 and separates the lower extending portion 36a and the inclined extending portion 36b. The boundary line 38c extends along the upper end of the inclined surface 32 and separates the inclined extending portion 36b and the upper extending portion 36c. The step line portion 36 partitions the upper extending portion 36c and the upper surface line portion 37.

The line width W of the lower surface line portion 35 and the upper surface line portion 37 is a standard value Ws. On the other hand, the line width W of the step line portion 36 is an enlarged value Wb (Wb ≧ Ws or Wb> Ws>) which is equal to or larger than the standard value Ws. The standard value Ws is set as a value that keeps the crosstalk caused by the wiring 25 at -20 dB or less (see (Table 1) described later) while avoiding the disconnection of the wiring 25 on the horizontal plane. Wb is set to a value equal to or higher than Ws as a value for preventing disconnection of the wiring 25 on the inclined surface 32.

3B and 3C are wiring structure diagrams of the first comparative example and the second comparative example, respectively. In the first comparative example, the line width is set to Ws having a monospaced font as a whole. In the second comparative example, the line width is wide Wb at the extending portion of the end portion of the surface of the upper surface 30 on the inclined surface 32 side, and the other extending portion is standard Ws. The first comparative example (FIG. 3B) is a wiring structure in a conventional general MEMS device. The second comparative example (FIG. 3C) is, for example, the wiring structure disclosed in Patent Document 3.

A ground wire 42 is further added to the wiring structure of FIG. 3C. The ground wire 42 is not disclosed in Patent Document 3. The ground wire 42 has a role of connecting the substrate 45 of the semiconductor device or the MEMS device to the ground and preventing crosstalk.

(Crosstalk)
FIG. 4 is an explanatory diagram of crosstalk in the MEMS device 44. The MEMS device 44 includes a substrate 45, an input side aluminum wiring 46 and an output side aluminum wiring 47 laminated on the surface of the substrate 45. The input-side aluminum wiring 46 and the output-side aluminum wiring 47 extend on the surface of the substrate 45 in parallel with each other. The substrate 45 includes an SOI (Silicon on Insulator) 50 and oxide film layers 51a and 51b formed on the front surface side and the back surface side of the SOI 50.

The input-side aluminum wiring 46 and the output-side aluminum wiring 47 face the SOI 50 with the oxide film layer 51a of the substrate 45 interposed therebetween. As a result, a crosstalk circuit 53 via the substrate 45 is generated between the input side aluminum wiring 46 and the output side aluminum wiring 47. The crosstalk circuit 53 is composed of a series circuit of a capacitor 54a, a resistor 55 and a capacitor 54b. In the crosstalk circuit 53, the portions of the oxide film layer 51a directly below the input side aluminum wiring 46 and the output side aluminum wiring 47 act as capacitors 54a and 54b, and the SOI 50 acts as a resistance 55.

The capacitance of the capacitors 54a and 54b is proportional to the line width W of the input side aluminum wiring 46 and the output side aluminum wiring 47. Further, the electric power consumed by the resistor 55 is proportional to the current Ict flowing through the input side aluminum wiring 46 and the output side aluminum wiring 47. In order to reduce crosstalk, it is desirable to reduce the line width W as much as possible.

As shown in FIG. 3B, in order to prevent disconnection of the wiring 25 on the inclined surface 32, uniformly widening the line width of the wiring 25 over the entire length of the wiring 25 is a countermeasure against disconnection on the inclined surface 32. Excellent, but increases crosstalk. On the contrary, narrowing the width uniformly is excellent as a countermeasure against crosstalk, but it tends to cause disconnection. Further, as shown in FIG. 3C, setting the voltage of the substrate 45 to 0 V with the ground wire 42 complicates the structure of the MEMS device 44 and increases the cost.

The following (Table 1) shows the relationship between the signal frequency of the input side aluminum wiring 46, the line width W of the input side aluminum wiring 46 and the output side aluminum wiring 47, and the amount of crosstalk. The amount of crosstalk is defined as the signal power of the input side aluminum wiring 46a ÷ the signal power of the input side aluminum wiring 46b.

From the above (Table 1), it is understood that if the amount of crosstalk at 20000 Hz is to be suppressed to −20 dB or less, the line width W ≦ 10 μm needs to be set.

(Production method)
5A and 5B are schematic explanatory views of a method for manufacturing the optical deflector 10. In the manufacturing method, the steps are carried out in the order of STEP numbers. Each cross-sectional view of FIGS. 5A and 5B is, for example, a cross-sectional view in the range of the inclined surface 32 of FIG.

In STEP 1, a multilayer plate 58 is prepared. The multilayer board 58 includes a substrate 45 and a laminated portion 57 laminated on the surface of the substrate 45. The multilayer plate 58 corresponds to the substrate portion of the present invention. The laminated portion 57 includes a lower electrode layer 59, a piezoelectric film layer 60, and an upper electrode layer 61 in this order from the bottom. The material of the piezoelectric film layer 60 is, for example, PZT (lead zirconate titanate).

In STEP2, the lower surface 29, the upper surface 30 and the inclined surface 32 are formed by etching. The inclined surface 32 constitutes a step between the lower surface 29 and the upper surface 30.

In STEP 3, an interlayer insulating film 63 and an aluminum film layer 65 as a metal film are sequentially formed on the surface side of the multilayer plate 58.

In STEP 4, a positive photoresist 66 is formed on the aluminum film layer 65. The surfaces of the photoresist 66 are aligned at the same height.

In STEP 5, the photomask 69 is aligned parallel to the surface of the multilayer plate 58 so as to face the multilayer plate 58. Then, the surface of the multilayer plate 58 is exposed to UV light (ultraviolet light) 71 via the exposure pattern 70 of the photomask 69. Further, the exposure pattern 70 includes shading and exposure patterning necessary for forming the wiring 25. The patterning includes a patterning line that determines the line width of the wiring 25.

In STEP 6, the photoresist 66 is developed. As a result, the region of the photoresist 66 exposed in STEP 5 is removed, and the unexposed region becomes an etching mask. In STEP 6, the aluminum film layer 65 is further etched from the surface side of the multilayer plate 58 using this etching mask. As a result, the wiring 25 is formed between the lower surface 29 and the upper surface 30 through the inclined surface 32.

STEP 6b of FIG. 5B points out a problem of the etching mask 67 (photoresist 66 after development) after development of STEP 6 of the prior art. The figure of STEP6b is not a cross-sectional view but a plan view. For reference, the scattered light 75 is also shown in STEP 5.

According to the inventor's knowledge, in STEP 5, the UV light 71 is reflected by the inclined surface 32 and becomes scattered light 75 and is emitted to the surroundings, and some of the scattered light 75 is directly above the wiring 25 which should be shielded from light. The photoresist 66 of the above is exposed. As a result, an extremely thin narrowed portion 74 is formed in the etching mask 67 of the corresponding portion of the wiring 25 on the inclined surface 32 side of the upper surface 30. The narrowed portion 74 causes the generation of the cut portion 41 in FIG. 3B in the subsequent etching of the aluminum film layer 65.

A method for dealing with such scattered light 75 will be described below. In the plan view of STEP6b, the lines A6a-A6a indicate the position of the cross section of STEP6. Further, the line A6b-A6b indicates the position of the cross section of FIG. 6A below. U1 and U2 will be described with reference to FIG. 6B.

(Countermeasures against scattered light)
FIG. 6A is an analysis diagram of the reach of the scattered light 75 in the cross section of the multilayer plate 58. FIG. 6A is also a cross section of A6b-A6b of FIG. 5B. In FIG. 6A, the etching mask 67 covers the entire surface of the multilayer plate 58.

In FIG. 6A, the definition of each symbol is as follows. La1 to La4 are the lengths in the horizontal direction (horizontal direction) in the cross section, and Ls is the lengths in the vertical direction (vertical direction) in the cross section.

Rl: The distance that the scattered light 75 can reach with a predetermined intensity or higher. The starting point of Rl is the lower end of the inclined surface 32.
Cu: Upward extension line of the inclined surface 32 Ls: A length within the range of the step La1: Rl of the inclined surface 32 and on the upper surface 30 side from the upper end of the inclined surface 32. La1 is set including the setting value La4 described later.
La2: Length of inclined surface 32 La3: = Rl
La4: A preset value as a misalignment of the wiring 25 in the line direction in patterning of the wiring 25 in patterning.
Ls: Length (step) of the inclined surface 32 in the vertical direction

The following (Equation 1) holds.
Intensity of scattered light 75 = La2 ÷ 2, π, Rl ... (Equation 1)

Assuming that Rl is the reach of the scattered light 75 of −20 dB (= 0.1) with respect to the intensity of the UV light 71, (Equation 1) becomes as follows (Equation 2).
Rl = La2 ÷ 2 ・ π ÷ 0.1 = La2 × 1.6 ... (Equation 2)

Assuming that the inclination angle of the inclined surface 32 is 45 to 60 °, La2≈Ls. In other words, in order to form the etching mask 67 for ensuring the line width to be equal to or higher than the standard value Ws, despite the reduction of the line width of the wiring 25 on the lower surface 29 due to the scattered light 75. The boundary line 38a needs to be set at a position separated from the lower end of the inclined surface 32 toward the lower surface 29 by 1.6 · Ls (= La3) or more along the wiring 25 in the extending direction of the wiring 25.

Desirably, in consideration of the misalignment of the wiring 25 in the line direction in patterning, the boundary line 38a has a length of 1.6 · Ls (= La3) from the lower end of the inclined surface 32 in the line direction of the wiring 25 and La4. It is necessary to set the distance more than the sum length of.

FIG. 6B is a plan view illustrating the reach of the scattered light 75 in the width direction of the wiring 25 due to the inclined surface 32. In FIG. 6B, the definition of each symbol is as follows.
U1: Straight line 78 passing through one side edge of the etching mask 67 on the inclined surface 32: Intersection point Rw between U1 and the boundary line 38b: Distance at which the scattered light 75 from the intersection point 78 can reach at a predetermined intensity or higher.
U2: Rw from the intersection 78 on the boundary line 38b, the inner position

The following (Equation 3) holds.
Intensity of scattered light 75 = La2 ² ÷ 4 ・ π ・ Rw ² ... (Equation 3)

Assuming that Rw is the reach of the scattered light 75 of −20 dB (= 0.1) with respect to the intensity of the UV light 71, (Equation 3) is converted as follows (Equation 4).
Rw = √ ((La) ² ÷ 4 ・ π ÷ 0.1) = La2 × 0.6 ... (Equation 4)

Assuming that the inclination angle of the inclined surface 32 is 45 to 60 °, La2≈Ls. In other words, in order to make the line width of the wiring 25 on the lower surface 29 equal to or more than the standard value Ws despite the decrease in the line width of the etching mask 67 between the boundary line 38a and the boundary line 38b due to the scattered light 75. It is necessary to set U1 at a position separated from U2 by 0.6 · Ls (= La3) or more on the outer side along the boundary line 38b.

Further, considering the misalignment of the wiring 25 in the line width direction in patterning, the width of the etching mask 67 between the boundary line 38a and the boundary line 38b due to the scattered light 75 is reduced, but the width of the etching mask 67 is reduced on the lower surface 29. In order to make the line width of the wiring 25 equal to or more than the standard value Ws, the U1 has 0.6 · Ls (= La3) outward along the boundary line 38b from the U2 and the alignment of the wiring 25 in the line width direction in patterning. It is necessary to set the deviation at a position separated by the length of the sum of the preset values (the set value in the line width direction may be equal to the above-mentioned set value La4 in the line direction). be.

(Another embodiment)
FIG. 7 is an electron micrograph of the inclined surface 32. Since the piezoelectric film layer 60 is exposed on the inclined surface 32, the semi-cylindrical side surface 82, which is a semi-cylindrical surface of each crystal of PZT of the piezoelectric film layer 60, is exposed instead of a flat surface. The inclined surface 32 has a plurality of semi-cylindrical side surfaces 82 arranged in the extending direction of the boundary line with the lower surface 29 (in the longitudinal direction of the inclined surface 32).

The semi-cylindrical side surface 82 exposed on the semi-cylindrical side surface 82 has the same dimensions and the same shape as the PZT crystal of the piezoelectric film layer 60. In the semi-cylindrical side surface 82, the light collection position of the scattered light 75 from the semi-cylindrical side surface 82 in the exposure step in STEP 5 is located on the side edge of the lower extending mask portion of the step mask portion of the etching mask 67. Has a shape. By utilizing the light collecting position of the scattered light 75, it is possible to form a constricted portion 85 (FIG. 8) in the lower extending portion 36a, which helps prevent the stepped line portion 36 of the wiring 25 from peeling off.

FIG. 8 is a diagram showing a wiring structure having a constricted portion 85 generated by scattered light 75 from the semi-cylindrical side surface 82.

The scattered light 75 from the semi-cylindrical side surface 82 is focused on a specific portion of the side edge of the lower extending portion 36a of the step line portion 36 of the wiring 25. As a result, as shown in FIG. 8, a groove 86 is formed at the location. Then, between the grooves 86 on both sides in the width direction, a constricted portion 85 is formed, and the line width is reduced. The significance of the constricted portion 85 and the groove 86 will be described below.

FIG. 9A is an electron micrograph of a predetermined prototype when it is investigated that the constricted portion 85 is actually formed in the wiring 25 by the scattered light 75. In the prototype, an aluminum wiring 25 having a line width of 40 μm was created with a target of a remaining line width of 5 μm. It was confirmed from FIG. 9A that the constricted portion 85 was formed.

FIG. 9B is a cross-sectional view of a portion of the multilayer plate 58 corresponding to the constricted portion 85 of FIG. 9A. The cross-sectional view corresponds to the cross-sectional view in the step of removing the etching mask 67 after STEP 6 of FIG. 5B and then covering the surface with the insulating film 91.

In FIG. 9B, the insulating film 91 has entered the grooves 86 on both sides of the constricted portion 85. The insulating film 91 covers the surface of the wiring 25, enters the groove 86, and is fixed to the side edge of the wiring 25, and the insulating film 91 firmly fixes the wiring 25 to the lower surface 29. As a result, even when the piezoelectric film layer 60 operates during the operation of the optical deflector 10, the wiring 25 is prevented from being peeled off from the surface of the lower surface 29. This increases the reliability of the optical deflector 10. In addition, since the area of the aluminum wiring is reduced by the amount of the constricted portion 85, it also contributes to the improvement of crosstalk.

(Variations and supplementary explanations)
The first step and the second step of the present invention correspond to STEP 3 and STEP 4 of the embodiment, respectively. The third step of the present invention corresponds to STEP 5 and the first half of STEP 6 of the embodiment. The fourth step of the present invention corresponds to the latter half of STEP 6 of the embodiment.

The metal film of the present invention corresponds to the aluminum film layer 65 of the embodiment. The material of the metal film of the present invention is not limited to aluminum. It may be another metal containing less than 6% of other metals such as Cu and Nd in aluminum.

In the embodiment shown in FIG. 5A and the like, the film thickness of the oxide film layer 51a is 300 nm or more, preferably 1000 nm. The film thickness of the wiring 25 is preferably 500 nm. Further, when the film thickness of the wiring 25 is 500 nm, it is desirable that the wiring thickness (diameter) is 1 μm or more per 1 μA of the current amount. The line width of the wiring 25 is preferably 20 μm or less for the electrode pad.

The manufacturing method to which the manufacturing method of the present invention is applied is not limited to the optical deflector 10 of the embodiment. The manufacturing method is applicable regardless of the presence or absence of the piezoelectric film layer of the MEMS device.

In the embodiment, the step line portion 36 includes an upper extending portion 36c. In the present invention, the step line portion does not have to include the upper extending portion 36c.

In the optical deflector 10 manufactured by the manufacturing method of the embodiment, the line width W of the wiring 25 is not set to a wide enlarged value Wb over the entire length, and only the lower surface 29 and the extending portion in the vicinity thereof are expanded. The value is Wb. Therefore, the ground wire 42 shown in FIG. 3D can be omitted to suppress crosstalk.

In the embodiment, UV light 71 is used as the exposure light in photolithography. In the present invention, other exposure light may be used instead of the UV light 71.

10 ... Optical deflector (MEMS device), 25 ... Wiring, 29 ... Lower surface, 30 ... Upper surface, 32 ... Inclined surface, 35 ... Lower surface line portion, 36 ... Step line portion, 36a ... Lower extending portion, 36b ... Inclined extending portion, 36c ... Upper extending portion, 37 ... Upper surface line portion, 57 ... Laminated Part, 58 ... multilayer plate, 59 ... lower electrode layer, 60 ... piezoelectric film layer, 61 ... upper electrode layer, 65 ... aluminum film layer, 66 ... photoresist, 67 ... Etching mask, 69 ... Photomask, 71 ... UV light, 75 ... Scattered light, 82 ... Semi-cylindrical side surface, 85 ... Constriction, 86 ... Groove.

Claims (9)

A substrate portion having an inclined surface which is a surface of an upper surface, a lower surface, and a step between the upper surface and the lower surface, and wiring extending between the upper surface and the lower surface. It is a manufacturing method of a MEMS device equipped with
The first step of forming a metal film having a thickness smaller than the step as a material for the wiring on the substrate portion.
The second step of applying the photoresist on the surface of the metal film and
The line width of the stepped mask portion including the inclined mask portion on the inclined surface and the upper and lower extending mask portions extending from the inclined surface to the upper surface and the lower surface, respectively, is the inclined mask portion. A third step of patterning the photoresist so as to be wider than the line width of the upper surface mask portion and the lower surface mask portion extending on the upper surface and the lower surface, respectively, to form an etching mask. When,
The fourth step of etching the metal film with the etching mask to form the wiring, and
A method for manufacturing a MEMS device, which comprises. In the method for manufacturing a MEMS device according to claim 1.
A method for manufacturing a MEMS device, wherein the boundary between the step mask portion and the lower surface mask portion is separated from the lower end of the inclined surface in the line direction by a length of 1.6 times or more the step. .. In the method for manufacturing a MEMS device according to claim 2.
The boundary between the step mask portion and the lower surface mask portion is 1.6 times the step in the line direction from the lower end of the inclined surface, and is set in advance as an alignment deviation in the patterning. A method for manufacturing a MEMS device, which is characterized by being separated by a sum of lengths or more. In the method for manufacturing a MEMS device according to any one of claims 1 to 3.
Both ends of the line width of the step mask portion are separated from both ends of the line width of the lower surface mask portion to the outside in the line width direction by a length of 0.6 times or more the step. How to make the device. In the method for manufacturing a MEMS device according to claim 4.
Both ends of the line width of the step mask portion are set in advance as 0.6 times the step and an alignment deviation in the patterning from both ends of the line width of the lower surface mask portion to the outside in the line width direction. A method for manufacturing a MEMS device, characterized in that it is separated from a certain set value by a sum length or more. In the method for manufacturing a MEMS device according to any one of claims 1 to 5.
The photoresist is a positive type and is
The inclined surface has a plurality of semi-cylindrical side surfaces arranged along the longitudinal direction of the inclined surface with exposed crystals of the piezoelectric film of PZT.
In the semi-cylindrical side surface, the position where the scattered light is collected from the semi-cylindrical side surface in the exposure step in the third step is located on the side edge of the lower extending mask portion of the step mask portion. A method for manufacturing a MEMS device, which comprises having a shape. In the method for manufacturing a MEMS device according to any one of claims 1 to 6.
The substrate portion has a common substrate under the upper surface and the lower surface, and further below the upper surface, there is a laminated portion laminated on the substrate and including a piezoelectric film layer. A method for manufacturing a MEMS device, characterized in that it is used. In the method for manufacturing a MEMS device according to claim 7.
The method for manufacturing a MEMS device, wherein the MEMS device is a MEMS optical deflector. A substrate portion having an inclined surface which is a surface of an upper surface, a lower surface, and a step between the upper surface and the lower surface, and wiring extending between the upper surface and the lower surface. It is a MEMS device equipped with
The wiring is
A stepped line portion including an inclined extending portion on the inclined surface and an upper and lower extending portions extending from the inclined surface to the upper surface and the lower surface, respectively.
An upper surface line portion and a lower surface line portion extending from the step line portion and extending on the upper surface and the lower surface, respectively.
Equipped with
The wiring has a thickness smaller than the step over the entire length, and has a thickness smaller than that of the step.
A MEMS device characterized in that the line width of the wiring is wider in the step line portion than in the upper surface line portion and the lower surface line portion.

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