JP7449784B2 - MEMS device manufacturing method and MEMS device - Google Patents

Description

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

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

On the other hand, wiring for MEMS devices is manufactured using photolithography, similar to semiconductor elements.

Patent Document 1 discloses a method for dealing with the problem that when forming wiring for a semiconductor device, the line width of the conductive thin film of the wiring is narrowed and reduced due to side etching, and the wiring becomes easily disconnected. In this method, the patterning line of the photomask for the part that is likely to become narrow due to constriction is made into a curved line or a broken line, so that even if the constriction occurs, the desired line width is ensured.

Patent Document 2 discloses a semiconductor device whose surface is prevented from becoming uneven due to wiring. According to the semiconductor device, a groove is formed in the surface, and the wiring is at least partially buried in the groove, so that the surface is smoothed. In that case, when the wiring goes in and out of the groove, it passes through the step of the groove, making it more likely to break. As a countermeasure for this, 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 predetermined line portion.

Patent Document 3 discloses a semiconductor device that has a step on the front side and wiring extends through the slope of the step. In this semiconductor device, the wiring is thickened (increased line width or wiring thickness) at the shoulder, that is, the end on the slope side of the upper surface that has gone up the slope, to prevent disconnection. .

Note that increasing the line width over the entire line is effective as a measure against disconnection. However, this increases the capacitance between the wiring and the substrate and increases crosstalk. Therefore, it is desirable that the line width on the front side of the MEMS device be as narrow as possible within a range that can prevent disconnection. Furthermore, connecting the board to ground in order to suppress crosstalk complicates the configuration and increases costs.

Japanese Unexamined Patent Publication No. 62-280890 Patent No. 3895507 JP2009-253035A

The present inventor discovered that when manufacturing a MEMS device using photolithography, scattered light is generated on the inclined surface on the front side of the MEMS device, and due to the secondary exposure of the photoresist by the scattered light, etching It was found that the line width sometimes decreases on and near sloped surfaces, which is highly likely to lead to wire breakage.

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

That is, Patent Document 1 deals with reduction in line width due to over-etching and side-etching even though patterning is normal. The wiring in Patent Document 1 is not made narrow only in the line portion of the inclined surface, but is made wide over 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 serving as the side wall of the trench. However, the groove is formed to at least partially bury the wiring that causes protrusions in order to smooth 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 too large than the line width, the groove will be recessed from its surroundings, which will impede smoothing of the surface of the MEMS device. In other words, the groove width is approximately equal to the line width. Such groove steps do not generate scattered light that leads to secondary exposure of the photoresist.

In Patent Document 3, in the wiring, the shoulder portion, that is, the line portion at the end on the slope side of the upper surface is made wider. In wiring, the line portion on the inclined surface is not made wider.

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

The method for manufacturing a MEMS device of the present invention includes:
a substrate portion having an upper surface, a lower surface, and an inclined surface that is a surface of a step between the upper surface and the lower surface; and a wiring extending between the upper surface and the lower surface; A method for manufacturing a MEMS device comprising:
A first step of forming a metal film having a thickness smaller than the step difference as a material for the wiring on the substrate part;
a second step of applying a photoresist on the surface of the metal film;
The line width of the stepped mask section, which is composed of an inclined mask section on the inclined surface and upper and lower extending mask sections extending from the inclined surface to the upper surface and the lower surface, respectively, is determined by the inclined mask section. a third step of forming an etching mask by patterning the photoresist so that the line width is 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; and,
a fourth step of etching the metal film using the etching mask to form the wiring;
Equipped with

According to the present invention, in the etching mask in the third step, the line width of the step mask portion is made wider than the line width of the lower surface mask portion and the upper surface mask portion. As a result, in the fourth step of etching the metal film, even if the photoresist is subjected to secondary exposure by scattered light from the inclined surface, the metal film of the wiring will have a sufficient line width, and the surface of the inclined surface and its vicinity will be This can prevent the upper wiring from breaking.

According to the present invention, since the increase in wiring width is limited to the range of the inclined surface, it is possible to omit the installation of a ground wire that connects the board 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 spaced apart from the lower end of the inclined surface in the line direction by a length that is 1.6 times or more the step difference.

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 part and the lower surface mask part is 1.6 times the step in the line direction from the lower end of the slope, and a set value preset as an alignment deviation in the patterning. are separated by at least the length of the sum of .

According to this configuration, it is possible to appropriately set a wide wiring range in the line direction, taking into account misalignment during 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 spaced from both ends of the line width of the lower surface mask portion outward in the line width direction by a length that is 0.6 times or more the step difference.

According to this configuration, the line width of the 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 outward in the line width direction from both ends of the line width of the lower surface mask portion, and an alignment deviation in the patterning. The distance is greater than the length of the sum of a certain setting value.

According to this configuration, it is possible to appropriately set the line width of the wide wiring range, taking into consideration misalignment during patterning.

Preferably, in the method for manufacturing a MEMS device of the present invention,
The photoresist is positive type,
The inclined surface has a plurality of semi-cylindrical side surfaces arranged along the longitudinal direction of the inclined surface, in which crystals of a PZT piezoelectric film are exposed,
The semi-cylindrical side surface is such that a condensing position of scattered light from the semi-cylindrical side surface in the exposure step in the third step is located at a side edge of the lower extending mask portion of the stepped mask portion. It has a shape.

According to this configuration, it is possible to form a constriction in the wiring by using scattered light from the semi-cylindrical side surface of the inclined surface, thereby preventing 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 has a laminated portion laminated on the substrate and including a piezoelectric film layer under the upper surface. are doing.

According to this configuration, it is possible to appropriately implement the method for manufacturing a MEMS device including a piezoelectric film 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 for a MEMS device.

The MEMS device of the present invention includes:
a substrate portion having an upper surface, a lower surface, and an inclined surface that is a surface of a step between the upper surface and the lower surface; and a wiring extending between the upper surface and the lower surface; A MEMS device comprising:
The wiring is
a stepped line portion consisting of an inclined extending portion on the inclined surface, and 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 stepped line portion and extending onto the upper surface and the lower surface, respectively;
Equipped with
The wiring has a thickness smaller than the step over the entire length,
The line width of the wiring is wider in the stepped line portion than in the upper surface line portion and the lower surface line portion.

According to the MEMS device of the present invention, disconnection of wiring can be prevented while suppressing crosstalk.

FIG. 3 is a front view of the optical deflector. FIG. 2 is a diagram showing an extended state of wiring at A2 in FIG. 1; FIG. 3 is a schematic diagram of a wiring structure on an inclined surface. FIG. 3 is a schematic diagram of a wiring structure as a first comparative example. FIG. 7 is a schematic diagram of a wiring structure as a second comparative example. FIG. 7 is a schematic diagram of a wiring structure as a third comparative example. FIG. 2 is an explanatory diagram of crosstalk in a MEMS device. FIG. 2 is a schematic explanatory diagram showing a method for manufacturing an optical deflector in order of steps. FIG. 5A is a schematic explanatory diagram of a method for manufacturing an optical deflector, showing the steps following the step in FIG. 5A in order. FIG. 3 is an analytical diagram of the reach range of scattered light in a cross section of a multilayer board. FIG. 3 is a plan view illustrating the reach range of scattered light in the width direction of the wiring due to the inclined surface. This is an electron micrograph of an inclined surface. FIG. 3 is a diagram showing a wiring structure having a constriction generated by scattered light from a semi-cylindrical side surface. This is an electron micrograph taken when investigating whether a constriction was actually formed in the wiring due to scattered light in a predetermined prototype. FIG. 9B is a cross-sectional view of a portion of the multilayer board corresponding to the constricted portion of FIG. 9A.

Embodiments of the present invention will be described below with reference to the drawings. It goes without saying that the present invention is not limited to the embodiments. The present invention can be implemented with various modifications within the scope of its technical idea. The same components are given the same reference numerals throughout the drawings.

(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 will be defined. The circumferential outline of the optical deflector 10 is rectangular when the optical deflector 10 is viewed from the front. The X-axis and Y-axis are parallel to the long side and 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 an inoperative state. When the optical deflector 10 is activated, the movable part of the optical deflector 10 is displaced from the state shown in FIG.

The MEMS optical deflector 10 includes a mirror section 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 optical deflector 10 and has a circular shape in this example. The incident beam Bi enters the center O of the mirror section 11 from a light source (not shown). The mirror part 11 is rotated by the operation of the inner piezoelectric actuator 13 (a generic term for the inner piezoelectric actuators 13a and 13b) and the outer actuator 15 (a generic term for the outer actuators 15a and 15b) to rotate a first rotation axis 22y and a second rotation axis that are perpendicular to each other at the center O. It reciprocates around two axes of 22x. As a result, the incident beam Bi is reflected at the mirror section 11, becomes a scanning beam Bs, and exits from the mirror section 11. The scanning beam Bs performs raster scanning in its irradiation area.

The inner piezoelectric actuators 13a and 13b are arranged on both sides of the mirror section 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 semicircular profile on both sides in the Y-axis direction and a straight line 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 protrude 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, 12b) is coupled to the inner periphery of the movable frame 14 at its tip, and coupled to the inner piezoelectric actuator 13 at its intermediate portion.

The outer actuators 15a and 15b are arranged on each side of the movable frame 14 in the X-axis direction, 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 cantilevers 18 connected in series in a meander pattern arrangement. Each connecting portion 24 connects cantilevers 18 adjacent to each other in the X-axis direction.

Each cantilever 18 has a dedicated piezoelectric film layer 60 (FIG. 5A), and when a driving voltage is applied to the piezoelectric film layer 60, it bends in the Z-axis direction. Drive voltages having mutually opposite phases are applied to cantilevers 18 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 at a large deflection angle.

The electrode pads 20a and 20b are formed on the short sides of the fixed frame 16. The optical deflector 10 is used while being enclosed in a package (not shown). At this time, each electrode pad 20 (general term for electrode pads 20a and 20b) is connected to a 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 wiring 25 (FIG. 2) in the optical deflector 10, and supplies a driving voltage.

The function of the optical deflector 10 will be briefly explained. The inner piezoelectric actuator 13 reciprocates the mirror portion 11 around the first rotation axis 22y via the torsion bar 12 at a resonance frequency (for example, about 1.6 kHz). The outer actuator 15 reciprocates the movable frame 14 around a rotation axis parallel to the X-axis at a non-resonant frequency (for example, 60 Hz). Thereby, the mirror part 11 reciprocates around the second rotation axis 22x and the first rotation axis 22y, respectively. During operation of the optical deflector 10, when the mirror section 11 faces straight ahead, the second rotation axis 22x and the first rotation axis 22y are parallel to the X axis and the Y axis, respectively.

Note that both the inner piezoelectric actuator 13 and the outer actuator 15 are unipolar piezoelectric actuators.

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

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

The cantilever 18 is protruded from the connecting portion 24. As a result, the lower surface 29 of the connecting portion 24 is lower than the upper surface 30 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 to 3D are schematic diagrams of wiring structures as comparative examples.

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 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 stepped 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. 3A includes an enlarged portion of the stepped line portion 36. FIG.

In order to clarify the ranges of the lower extending portion 36a, the inclined extending portion 36b, and the upper extending portion 36c in the stepped line portion 36, boundary lines 38a, 38b, 38c, and 38d are shown in FIG. 3A. There is. The boundary line 38a is a line that partitions 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 partitions 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 partitions the inclined extending portion 36b and the upper extending portion 36c. The stepped 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 set to a standard value Ws. On the other hand, the line width W of the stepped line portion 36 is set to an enlarged value Wb (Wb≧Ws or Wb>Ws>) that is greater than or equal to the standard value Ws. The standard value Ws is set as a value that maintains crosstalk caused by the wiring 25 to -20 dB or less (see (Table 1) described later) while avoiding disconnection of the wiring 25 on a horizontal plane. Wb is set to a value greater than or equal to Ws to prevent disconnection of the wiring 25 on the inclined surface 32.

3B and 3C are wiring structure diagrams of a first comparative example and a second comparative example, respectively. In the first comparative example, the line width is the same width Ws throughout. In the second comparative example, the line width is wide Wb in the extending portion of the end of the upper surface 30 on the inclined surface 32 side, and the line width is the standard Ws in the other extending portions. 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 connects the substrate 45 of the semiconductor device or the MEMS device to the ground, and has the role of preventing crosstalk.

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

The input aluminum wiring 46 and the output 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 is generated between the input aluminum wiring 46 and the output aluminum wiring 47 via the substrate 45. 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 under the input aluminum wiring 46 and the output aluminum wiring 47 act as capacitors 54a and 54b, and the SOI 50 acts as a resistor 55.

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

As shown in FIG. 3B, uniformly widening the line width of the wiring 25 over the entire length of the wiring 25 in order to prevent the wiring 25 from breaking on the slope 32 is a countermeasure against disconnection on the slope 32. Although it is excellent, it increases crosstalk. On the other hand, uniformly narrowing the width is an excellent measure against crosstalk, but it makes wire breakage more likely. Further, as shown in FIG. 3C, setting the voltage of the substrate 45 to 0V through the ground wire 42 complicates the structure of the MEMS device 44 and increases cost.

The following (Table 1) shows the relationship between the frequency of the signal 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 aluminum wiring 46a divided by the signal power of the input aluminum wiring 46b.

From the above (Table 1), it is understood that if the amount of crosstalk at 20,000 Hz is to be suppressed to -20 dB or less, it is necessary to make the line width W≦10 μm.

(Production method)
5A and 5B are schematic explanatory diagrams of a method of manufacturing the optical deflector 10. In this manufacturing method, the steps are performed in the numerical order of STEP. Each cross-sectional view in FIGS. 5A and 5B is, for example, a cross section in the range of the inclined surface 32 in FIG. 2.

In STEP 1, the multilayer board 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 board 58 corresponds to the substrate section 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 order from the bottom. The material of the piezoelectric film layer 60 is, for example, PZT (lead titanium zirconate).

In STEP 2, a lower surface 29, an upper surface 30, and an inclined surface 32 are formed by etching. The sloped 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 board 58.

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

In STEP 5, the photomask 69 is aligned parallel to the surface of the multilayer board 58 and facing the multilayer board 58. Then, the surface of the multilayer plate 58 is exposed to UV light (ultraviolet light) 71 through the exposure pattern 70 of the photomask 69. Further, the exposure pattern 70 includes light shielding 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 area of the photoresist 66 that was exposed in STEP 5 is removed, and the area that was not exposed becomes an etching mask. In STEP 6, the aluminum film layer 65 is further etched from the front surface side of the multilayer board 58 using this etching mask. As a result, wiring 25 is formed between lower surface 29 and upper surface 30 through inclined surface 32.

STEP 6b in FIG. 5B points out a problem with the etching mask 67 after development (photoresist 66 after development) in STEP 6 of the prior art. The diagram of STEP 6b is not a sectional view but a plan view. For reference, scattered light 75 is also shown in STEP5.

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

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

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

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

Rl: Distance that the scattered light 75 can reach with a predetermined intensity or more. Note that the starting point of Rl is the lower end of the inclined surface 32.
Cu: Upward extension line Ls of the inclined surface 32: Length within the step La1:Rl of the inclined surface 32, from the upper end of the inclined surface 32 to the upper surface 30 side. La1 is set including a setting value La4, which will be described later.
La2: Length of slope 32 La3:=Rl
La4: A setting value set in advance as a deviation in alignment of the wiring 25 in the line direction during patterning of the wiring 25 in the line direction.
Ls: Length of vertical inclined surface 32 (step)

The following (Formula 1) holds true.
Intensity of scattered light 75 = La2÷2・π・Rl... (Formula 1)

If Rl is the reaching distance of the scattered light 75 at -20 dB (=0.1) with respect to the intensity of the UV light 71, then (Formula 1) becomes the following (Formula 2).
Rl=La2÷2・π÷0.1=La2×1.6...(Formula 2)

If the angle of inclination of the inclined surface 32 is 45 to 60°, then La2≈Ls. In other words, in order to form the etching mask 67 for ensuring the line width of the wiring 25 on the lower surface 29 to be equal to or greater than the standard value Ws despite the reduction in 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 location 1.6·Ls (=La3) or more along the wiring 25 from the lower end of the inclined surface 32 toward the lower surface 29 in the extending direction of the wiring 25.

Preferably, in consideration of misalignment in the line direction of the wiring 25 during 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 must be set at a location that is at least the length of the sum of .

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

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

If Rw is the reach distance of the scattered light 75 of -20 dB (=0.1) with respect to the intensity of the UV light 71, then (Equation 3) is converted as shown in the following (Equation 4).
Rw=√((La) ² ÷4・π÷0.1)=La2×0.6...(Formula 4)

If the angle of inclination of the inclined surface 32 is 45 to 60°, then La2≈Ls. In other words, in order to make the line width of the wiring 25 on the lower surface 29 equal to or greater 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. In this case, U1 needs to be set at a location more than 0.6·Ls (=La3) away from U2 along the boundary line 38b.

Furthermore, considering the misalignment in the line width direction of the wiring 25 during patterning, even though the width of the etching mask 67 between the boundary line 38a and the boundary line 38b is reduced due to the scattered light 75, In order to make the line width of the wiring 25 equal to or greater than the standard value Ws, U1 must be 0.6·Ls (=La3) outward from U2 along the boundary line 38b and the alignment of the wiring 25 in the line width direction during patterning. It is necessary to set the distance at a location that is at least the length of the sum of the set value set in advance as the deviation (the set value in the line width direction may be equal to the set value La4 in the line direction described above). 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 PZT crystal 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 to the semi-cylindrical side surface 82 has the same dimensions and the same shape as the PZT crystal of the piezoelectric film layer 60. The semi-cylindrical side surface 82 is such that the condensing position of the scattered light 75 from the semi-cylindrical side surface 82 during the exposure process in STEP 5 is located at the side edge of the lower extending mask portion of the step mask portion of the etching mask 67. It has a shape. By utilizing the condensing position of the scattered light 75, it is possible to form a constricted portion 85 (FIG. 8) in the lower extending portion 36a, which is useful for preventing the step line portion 36 of the wiring 25 from peeling off.

FIG. 8 is a diagram showing a wiring structure having a constriction 85 generated by the 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 36 a of the stepped line portion 36 of the wiring 25 . As a result, a groove 86 is formed at the location, as shown in FIG. A constriction 85 is formed between the grooves 86 on both sides in the width direction, and the line width is reduced. The significance of the constricted portion 85 and the groove 86 will be explained next.

FIG. 9A is an electron micrograph taken to confirm that a constriction 85 is actually formed in the wiring 25 due to the scattered light 75 in a predetermined prototype. In this prototype, an aluminum wiring 25 with a line width of 40 μm was created, aiming at a remaining line width of 5 μm. It was confirmed from FIG. 9A that a constricted portion 85 was formed.

FIG. 9B is a cross-sectional view of a portion of the multilayer board 58 corresponding to the constricted portion 85 in FIG. 9A. This cross-sectional view corresponds to a step in which the etching mask 67 is removed after STEP 6 in FIG. 5B, and then the surface is coated with an insulating film 91.

In FIG. 9B, an insulating film 91 is inserted into the grooves 86 on both sides of the constricted portion 85. In FIG. Insulating film 91 covers the surface of wiring 25 and enters groove 86 to adhere to the side edge of wiring 25 , and insulating film 91 firmly adheres wiring 25 to lower surface 29 . As a result, even if piezoelectric film layer 60 operates during operation of optical deflector 10, wiring 25 is prevented from peeling off from lower surface 29. This increases the reliability of the optical deflector 10. Furthermore, since the area of the aluminum wiring is reduced by the constricted portion 85, it also contributes to improving crosstalk.

(Modifications 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 STEP5 and the first half of STEP6 of the embodiment. The fourth step of the present invention corresponds to the second 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. Other metals containing less than 6% of other metals such as Cu and Nd in aluminum may also be used.

In embodiments such as FIG. 5A, the thickness of the oxide film layer 51a is 300 nm or more, preferably 1000 nm. The 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 current. The line width of the wiring 25 is preferably 20 μm or less than 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 can be applied regardless of the presence or absence of a piezoelectric film layer of a MEMS device.

In the embodiment, the stepped line portion 36 includes an upper extending portion 36c. In the present invention, the stepped line portion does not need 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, but only the lower surface 29 and the extending portion in the vicinity thereof are enlarged. The value becomes Wb. Therefore, crosstalk can be suppressed by omitting the ground wire 42 shown in FIG. 3D.

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

DESCRIPTION OF SYMBOLS 10... Optical deflector (MEMS device), 25... Wiring, 29... Lower surface, 30... Upper surface, 32... Inclined surface, 35... Lower surface line part, 36... Step line part, 36a... Lower side extension part, 36b... Inclined extension part, 36c... Upper side extension part, 37... Upper surface line part, 57... Lamination 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 .

Claims (7)

a substrate portion having an upper surface, a lower surface, and an inclined surface that is a surface of a step between the upper surface and the lower surface; and a wiring extending between the upper surface and the lower surface; A method for manufacturing a MEMS device comprising:
A first step of forming a metal film having a thickness smaller than the step difference as a material for the wiring on the substrate part;
a second step of applying a photoresist on the surface of the metal film;
The line width of the stepped mask section, which is composed of an inclined mask section on the inclined surface and upper and lower extending mask sections extending from the inclined surface to the upper surface and the lower surface, respectively, is determined by the inclined mask section. a third step of forming an etching mask by patterning the photoresist so that the line width is 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; and,
a fourth step of etching the metal film using the etching mask to form the wiring;
Equipped with
The photoresist is positive type,
The inclined surface has a plurality of semi-cylindrical side surfaces arranged along the longitudinal direction of the inclined surface, in which crystals of a PZT piezoelectric film are exposed,
The semi-cylindrical side surface is such that a condensing position of scattered light from the semi-cylindrical side surface in the exposure step in the third step is located at a side edge of the lower extending mask portion of the stepped mask portion. A method for manufacturing a MEMS device characterized by having a shape . 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 part and the lower surface mask part is separated from the lower end of the inclined surface in a line direction by a length that is 1.6 times or more the step difference. . The method for manufacturing a MEMS device according to claim 2,
The boundary between the step mask part and the lower surface mask part is 1.6 times the step in the line direction from the lower end of the slope, and a set value preset as an alignment deviation in the patterning. A method for manufacturing a MEMS device, characterized in that the MEMS devices are separated by a length equal to or more than the sum of the lengths of the MEMS devices. In the method for manufacturing a MEMS device according to any one of claims 1 to 3,
A MEMS device characterized in that 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 outward in the line width direction by a length of 0.6 times or more the step difference. Method of manufacturing the device. 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 outward in the line width direction from both ends of the line width of the lower surface mask portion, and an alignment deviation in the patterning. A method for manufacturing a MEMS device, characterized in that the device is separated by a length equal to or more than the sum of a certain set value. In the method for manufacturing a MEMS device according to any one of claims 1 to 5 ,
The substrate portion has a common substrate under the upper surface and the lower surface, and further has a laminated portion laminated on the substrate and including a piezoelectric film layer under the upper surface. A method for manufacturing a MEMS device characterized by: The method for manufacturing a MEMS device according to claim 6 ,
A method for manufacturing a MEMS device, wherein the MEMS device is a MEMS optical deflector.