JP2013053340A - Method for forming inorganic film having segment structure on friction contact surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming an inorganic film constituted of segments each having a uniform shape and height, and a round edge part, on a friction contact surface.SOLUTION: The method for forming an inorganic film constituted of segments includes: a step of forming a metal layer 40 for forming a mask on a film deposition surface; a step of forming projection parts of the metal layer 40 at respective groove positions partitioning segments by applying etching to the metal layer 40; a step of mounting on a substrate holder constituting a negative electrode so that the film deposition surface, on which the projection parts 40 are formed, may be exposed, and depositing an inorganic film composed of segments 7 whose edge parts opposing to the projection parts 40 are round, on the film deposition surface between the projection parts 40 by using a plasma CVD method; and a step of removing the projection parts 40. Since the edge part of each segment is round, when being brought into contact with a preloaded contact member, the contact pressure is made uniform over whole segment, and breakage does not occur at the edge part.

Description

  The present invention relates to a method of forming an inorganic film such as diamond-like carbon (DLC) in a segment shape on a surface in frictional contact, and is intended to improve the wear resistance of the frictional contact surface.

The ultrasonic motor is a friction drive type motor that drives a slider by bringing the slider into contact with a stator excited by ultrasonic waves, and is widely used as an AF driving motor for a camera.
FIG. 7 schematically shows a configuration of a surface acoustic wave linear motor which is a kind of ultrasonic motor. In this motor, the substrate 10 made of a piezoelectric material constitutes a stator, and when a high frequency voltage is applied to the interdigitated electrode 11 on the substrate 10, the surface acoustic wave 12 is excited on the substrate 10, and the surface of the substrate 10. Vibrates along an elliptical orbit. When the slider 20 is brought into contact with the substrate 10, the horizontal component of vibration is transmitted to the slider 20 via a frictional force, and the slider 20 obtains a driving force 22 opposite to the traveling direction of the surface acoustic wave 12.
In order to increase the frictional force (driving force) applied to the slider 20, a preload 21 is applied to the slider 20, and the slider 20 has a contact surface with the substrate 10 having a diameter of about 10 μm as shown in FIG. A silicon slider having a large number of protrusions 23 is used.

However, in the friction drive type ultrasonic motor, there is a problem that wear on the friction contact surface (friction drive surface) between the stator and the slider shortens the life of the motor.
In order to reduce this wear, the use of a DLC film of wear resistant material has been studied. The DLC film has high hardness among amorphous carbon films, and has excellent tribological characteristics such as a low friction coefficient and wear resistance, and the demand for the DLC film is expanding as a protective film for mechanical parts.
However, as shown in FIG. 9 (a), the single DLC film deposited on the base material is cracked when the base material is deformed, and is easy to peel off. A DLC film having a structure divided into a plurality of segments by vertical and horizontal grooves like a grid pattern (this structure film is referred to as a “segment structured DLC (S-DLC) film”) is formed. There is a need.

  Patent Document 1 below discloses a method of forming an S-DLC film on a stator or slider of an ultrasonic motor using a tungsten wire wire mesh as a “mesh mask” as shown in FIG. In this method, a wire mesh of tungsten wire is used as a mesh electrode (cathode) 30, and a film formation surface of a stator (or slider) 122 is mounted on the wire mesh, and plasma is generated using support portions 31a, 31b, and 31c. Plasma CVD is carried out by placing it inside the CVD apparatus so as to face the anode, and an S-DLC film is formed on the friction drive surface of the stator or slider.

Fig.11 (a) shows the shape of the S-DLC film | membrane formed with this method measured using the non-contact roughness measuring device, and FIG.11 (b) has shown the cross-sectional shape.
As exaggeratedly shown in FIG. 12, the protrusions 70 corresponding to the segments of the S-DLC film are not uniform in height and shape. Therefore, the contact area between the slider 20 and the stator 10 is reduced, and the slider 20 There is a problem that the frictional force (driving force) acting on the lowering is reduced.
The reason why the shape and height of the protrusions are non-uniform is considered to be that when the stator 10 and the mesh mask 30 are brought into close contact with each other, the mask wire bends, and the distance between the stator and the wire varies depending on the position of the mask. It is done.

Accordingly, the inventors of the present invention have developed a method for forming an S-DLC film by a photolithography process without using a mesh mask.
In this method, as shown in FIG. 13, first, a Cr layer that enhances adhesion to DLC is vapor-deposited as an intermediate layer 13 on a piezoelectric (LiNbO ₃ ) substrate 10 to further form a cross finger electrode. For this purpose, an Al layer 14 is formed, and a photoresist layer 15 is formed thereon (FIG. 13A). Next, unnecessary portions of the photoresist 15 are removed by exposure and development, and the Al layer 14 and the Cr layer 13 not covered with the photoresist are removed by etching (FIG. 13B). Next, the photoresist is removed with an organic solvent, and the Al layer on the film formation surface on which the S-DLC film is formed is removed by etching, leaving only the intermediate layer 13 (FIG. 13C). Next, a DLC film is formed on the film formation surface (FIG. 13D). With this film formation, an S-DLC film in which the DLC film 71 placed on the intermediate layer 13 constitutes a segment is obtained.

The S-DLC film formed by this method is hereinafter referred to as “S-Cr / DLC film”.
Fig.14 (a) shows the shape of the S-Cr / DLC film | membrane measured using the non-contact roughness measuring device, and FIG.14 (b) has shown the cross-sectional shape. As is clear from FIG. 14, the height and shape of the protrusions corresponding to the segments of the S-Cr / DLC film are uniform.

Patent Document 2 below discloses a method of accurately forming an inorganic film having a segment structure including an S-DLC film on a general substrate using a photolithography process.
In this method, as shown in FIG. 15, a photoresist layer 5 is formed on the substrate 2 (FIG. 15A), exposed and developed to remove the photoresist in the region corresponding to the segment, and the segment Photoresist protrusions 6 are formed on the base material 2 at positions corresponding to the grooves that define (FIG. 15B). Next, the DLC film 7 is formed on the base material 2 by a method such as a plasma CVD method. At this time, the DLC film 7 is formed on the exposed upper surface of the substrate 2 and the top and side surfaces of the protrusion 6 (FIG. 15C). Next, this base material 2 is immersed in a commercially available resist stripping solution, an organic solvent, or the like to remove the resist protrusions 6. The resist is removed by swelling, destruction or dissolution with these solutions. A groove 4 is formed in the trace of the protruding portion 6 (FIG. 15D).

  FIG. 16 shows the S-DLC film on the substrate 2 formed in this way, and the groove 4 surrounds the periphery of the segment 3. FIG. 17 shows a cross section of the groove 4. When the resist protrusion 6 is removed, the DLC film formed on the side surface of the protrusion 6 is separated at the boundary with the DLC film formed on the substrate 2, so that the side surface of the segment 3 has an inclination angle α To have.

JP 2007-236094 A JP 2010-7112 A

  However, as shown in FIG. 19 (a), the protrusion 71 constituting the segment of the S-Cr / DLC film has a uniform shape and height compared to the protrusion 70 of the S-DLC film in FIG. Although a stable contact area can be ensured between the slider 20 and the stator 10, the corner of the tip of the protrusion 71 is not round like the protrusion 70. This is clear when FIG. 11 and FIG. 14 are compared.

  Thus, when the edge part of the segment of the inorganic film formed on the friction contact surface is angular, as shown in FIG. 18, when a high contact preload is applied to the contact member 90 that contacts the surface of the segment 80 (b ), The end portion of the segment 80 is greatly elastically deformed, and stress is concentrated on the end portion of the segment 80 to increase the contact pressure (c), which may cause damage to the end portion of the segment 80.

Further, in the ultrasonic motor, if the edge portion of the projection of the S-DLC film is not rounded, the slider 20 is placed on the edge side surface of the projection 71 as shown in FIG. Since the end portions come into contact with each other and a force in the direction opposite to the driving direction acts on the slider 20, the driving characteristics of the ultrasonic motor are deteriorated.
Further, as shown in FIG. 17, even when the side surface of the segment 3 is inclined and the segment 3 has a trapezoidal cross section, the end portion of the slider contacts the edge portion of the segment 3. Since a force in the direction opposite to the driving direction is received, a reduction in driving characteristics of the ultrasonic motor is inevitable.

  The present invention was devised in view of such circumstances, and a method for forming an inorganic film having a segment structure composed of segments having a uniform shape and height and rounded edges on a frictional contact surface. The purpose is to provide.

The present invention relates to a method for forming an inorganic film having a segment structure in which the edge portion of a segment is rounded on a film-forming surface of a frictional contact surface, the mask-forming metal comprising a conductive metal on the film-forming surface. A metal layer forming step for forming a layer, a mask forming step for etching the metal layer to form a protrusion of the metal layer at a position to become a groove for partitioning the segment, and a film formation in which the protrusion of the metal layer is formed Place the electrode on the substrate holder that constitutes the electrode so that the surface is exposed, and use the physical vapor deposition method or the chemical vapor deposition method to form the edge facing the projection on the film-forming surface between the projections It is characterized by comprising a film forming step for forming an inorganic film having a rounded portion with a predetermined shape, and a mask removing step for removing protrusions of the metal layer.
When an inorganic film is deposited on the surface on which the mask protrusion is formed by physical vapor deposition or chemical vapor deposition, the solid angle of the incident plasma is reduced near the protrusion, so that it is close to the protrusion. The amount of carbon ions reaching the location is less than the amount of carbon ions reaching the location away from the protrusion. As a result, the edge of the formed segment is rounded. The curvature of this roundness varies depending on the thickness of the deposited inorganic film.

In the inorganic film forming method of the present invention, the inorganic film may be a DLC film.
By this forming method, an S-DLC film composed of segments having a uniform shape and height and rounded edges is obtained.

In the inorganic film forming method of the present invention, it is desirable to form an inorganic film using a plasma CVD method in the film forming step.
The mask protrusion made of the metal layer serves as an auxiliary electrode when the plasma CVD method is performed, and contributes to the stabilization of the plasma.

Further, in the inorganic film forming method of the present invention, the curvature of the roundness of the edge portion facing the protrusion can be changed by changing the thickness of the metal layer and changing the height of the protrusion.
Since ions entering the hole surrounded by the protrusion of the metal mask are pulled toward the metal layer when a metal layer (electrode) exists in the vicinity, the effective solid angle of ion incidence near the metal layer is narrow. Thus, the closer to the metal layer, the thinner the generated film. This “effective solid angle for ion incidence” becomes narrower as the height of the protrusion becomes higher. Therefore, by increasing the height of the protrusion (thickness of the metal layer), the edge of the segment is rounded. The curvature of increases.

  In the inorganic film forming method of the present invention, Cu or Al can be used as a metal layer for mask formation.

In the inorganic film forming method of the present invention, it is desirable to form an intermediate layer having high adhesion to the inorganic film on the film forming surface prior to the metal layer forming step.
When the intermediate layer is interposed, the segment of the formed inorganic film is firmly attached to the film formation surface.

Moreover, in the inorganic film forming method of the present invention, when forming the S-DLC film, it is desirable to form a Cr layer as an intermediate layer.
The Cr layer improves the adhesion of the DLC film.

In addition, the inorganic film forming method of the present invention is suitable as a method for forming an S-DLC film on the friction drive surface of the stator or mover of the ultrasonic motor.
This S-DLC film can improve the wear resistance of the ultrasonic motor without impairing the driving force of the ultrasonic motor, and can extend the life of the ultrasonic motor.

  By the forming method of the present invention, an inorganic film having a segment structure composed of segments having a uniform shape and height and rounded edges can be formed on the friction contact surface. Since this inorganic film does not concentrate stress on the end portion of the segment, the end portion of the segment is hardly damaged and has high durability.

The figure which shows the formation process of the S-DLC film | membrane of this invention The figure which shows the environment of DLC film formation of FIG.1 (d) The figure which shows the shape and sectional drawing of the segment of the S-DLC film | membrane formed by the method of FIG. The figure explaining the reason why the edge part of the segment formed by the method of FIG. 1 is rounded Figure showing the results of wear experiments The figure which shows the contact state of the segment with which the edge part was round, and a contact member Diagram showing the structure of a surface acoustic wave linear motor Diagram showing friction drive surface of slider Illustration of S-DLC film The figure which shows the formation method of the conventional S-DLC film | membrane The figure which shows the shape and sectional drawing of the segment of the S-DLC film | membrane formed by the method of FIG. The figure which shows the contact state of the segment of the S-DLC film | membrane formed by the method of FIG. 10, and a slider. The figure which shows the formation method of the conventional S-Cr / DLC film | membrane The figure which shows the shape and sectional drawing of the segment of the S-Cr / DLC film | membrane formed by the method of FIG. The figure which shows the formation method of the S-DLC film | membrane using the conventional photolithography process The figure which shows the S-DLC film | membrane formed by the method of FIG. Sectional drawing of the groove | channel of the S-DLC film | membrane formed by the method of FIG. The figure which shows the contact state of the segment with which the edge part was square, and a contact member The figure which shows the contact state of the segment of the S-Cr / DLC film | membrane formed by the method of FIG. 13, and a slider.

FIG. 1 shows a procedure for forming an S-DLC film on a piezoelectric (LiNbO ₃ ) substrate of a stator of an ultrasonic motor using the inorganic film forming method of the present invention.
First, an intermediate layer 13 made of a chromium (Cr) layer having high adhesion to the DLC film is formed on the substrate 10 by vapor deposition or the like, and a mask forming metal layer 40 made of a copper (Cu) layer is vapor deposited thereon. Etc. Here, the thickness of the intermediate layer 13 is set to about 0.1 μm, and the thickness of the mask forming metal layer 40 is set to about 4 μm. On the mask forming metal layer 40, a photoresist layer 15 was formed by spin coating (FIG. 1A).

Next, exposure and development were performed to leave a portion of the photoresist 15 corresponding to the groove between the segments, and to remove the photoresist 15 in the region corresponding to the segments. Then, the Cu layer portion of the metal layer 40 exposed by removing the photoresist 15 was removed by etching (FIG. 1B).
When the photoresist 15 on the remaining metal layer 40 is removed, a mask made of a mesh-like metal layer (projection) 40 is formed (FIG. 1C).

Next, a hydrocarbon gas is ionized by plasma discharge by plasma CVD, carbon ions are accelerated by an electric field, and a film formation surface of the substrate 10 placed on a substrate holder that also serves as a cathode, that is, a mask metal layer The DLC film 7 having a thickness of about 0.4 μm was formed by colliding with the surface on which the (projection) 40 was formed (FIG. 1D).
The detailed formation conditions of the DLC film 7 are shown in FIG.
The mask metal layer 40 serves as an auxiliary electrode during plasma CVD, and contributes to plasma stabilization.

Next, the mesh-like metal layer 40 and the DLC film 7 adhering to the metal layer are removed by wet etching with a ferric chloride aqueous solution, and an S-DLC film composed of segments 7 with rounded edges is obtained. (FIG. 1 (e)).
FIG. 3A shows the shape of the S-DLC film formed by this method measured using a non-contact roughness measuring instrument, and FIG. 3B shows the cross-sectional shape thereof.

  In this method, a mask of the metal layer 40 that is in close contact with the substrate 10 (via the intermediate layer 13) is formed by a photolithography process, and the S-DLC film is formed using this mask. As can be seen from the above, the shape and height of each segment of the S-DLC film are uniform.

In addition, as shown in FIG. 4A, in the segment formation region surrounded by the protrusion 40 of the metal layer, it is adjacent to the protrusion 40 as compared to the solid angle α ₁ of the incident plasma at the center of the region. The solid angle α ₂ of the incident plasma at the position is small. In addition, since the incident amount of plasma tends to decrease as the angle of incidence of plasma incident on the surface of the segment formation region deviates from a right angle, the amount of carbon ions reaching this formation region is the position adjacent to the protrusion 40. Decreases rapidly.

Further, since ions entering the segment formation region surrounded by the protrusions 40 of the metal layer are pulled toward the metal layer 40 when the metal layer (electrode) 40 exists in the vicinity, the ions enter the vicinity of the metal layer. The effective solid angle of plasma is narrower than the solid angle α ₂ shown in FIG. 4A, and the generated film becomes thinner as the metal layer 40 is approached. This “effective solid angle of the incident plasma” becomes narrower as the height of the protrusion 40 becomes higher.

Therefore, as shown in FIG. 4B, the edge portion of the segment 81 is rounded, and this roundness becomes more noticeable as the thickness of the segments 82 and 83 increases.
The roundness of the edge portion remains in the segment 83 even after the protrusion 40 and the DLC film 84 attached to the protrusion 40 are removed, as shown in an enlarged view in FIG.
Further, the “effective solid angle of incident plasma” generated when ions are pulled by the metal layer (electrode) becomes narrower as the height of the protrusion 40 becomes higher. (Thickness) can be controlled to change the curvature of the roundness of the edge portion of the segment.

FIG. 5 shows the results of an experiment for examining the wear state of the segment structure DLC film.
In this experiment, in order to simulate friction drive, a slider cut out from a silicon wafer was forcibly rubbed against a stator having a segment structure DLC film formed on the friction drive surface, and the state of change in the segment structure DLC film was observed. . The state of the segment structure DLC film after the slider is linearly moved 200 times while the preload on the slider is set to be constant (10 N) is observed.
FIG. 5A shows a state after the experiment of the S-DLC film obtained by the method of FIG. 1 (state after cleaning the dirt), and FIG. 5B shows an experiment of the S-Cr / DLC film. The subsequent state (the state after cleaning the dirt) is shown.
As can be seen from FIG. 5, the S-DLC film formed by the method of FIG. 1 has less scratches and wear than the S-Cr / DLC film.

  FIG. 6 shows a state where the contact member 90 is in contact with the frictional contact surface on which the rounded S-DLC film is formed on the edge portion of the segment 83 (a). In this case, even if the contact member 90 is brought into contact with the friction contact surface with a high contact preload (b), the elastic deformation of the end portion of the segment 83 is suppressed, and the contact pressure becomes uniform throughout the segment (c). Therefore, breakage of the segment 83 can be avoided.

  As described above, the inorganic film forming method of the present invention can form an inorganic film such as an S-DLC film having a uniform shape and height and having a rounded segment at the edge portion. The segment of the S-DLC film formed by this method does not hinder the driving of the slider as compared with the segment of the S-Cr / DLC film, so that the driving force of the ultrasonic motor is not impaired, and damage due to wear is small. .

In this example, the S-DLC film is formed on the friction drive surface of the stator or slider of the ultrasonic motor. However, in the present invention, the S-DLC film is applied to a continuously variable transmission having a friction contact surface. The present invention can also be applied to the formation, and can also be applied to the case where inorganic films such as SiO ₂ and Al ₂ O ₃ formed on various friction contact surfaces are formed into a segment structure.

Here, although Cu is used as the material for the mask-forming metal layer, aluminum (Al) may be used.
Here, the Cr layer is used as the intermediate layer for improving the adhesion of the DLC film, but Ti, Si, or the like may be used. Further, the intermediate layer may not be provided.
Here, the DLC film is formed by plasma CVD, but other physical vapor deposition or chemical vapor deposition may be used for forming the inorganic film.

  The inorganic film forming method of the present invention can form a highly durable segment structure inorganic film on the friction contact surface, and is widely used in many products having a friction contact surface such as an ultrasonic motor and a continuously variable transmission. can do.

2 Base material 3 Segment 4 Groove 5 Photoresist 6 Photoresist protrusion 7 DLC film 10 Piezoelectric substrate (stator)
DESCRIPTION OF SYMBOLS 11 Cross finger electrode 12 Surface acoustic wave 13 Intermediate layer 14 Al layer 15 Photoresist 20 Slider 21 Preload 22 Driving force 23 Protrusion 30 Mesh electrode 31a Support part 31b Support part 31c Support part 40 Metal layer for mask formation 70 Protrusion 71 DLC film Projection 81 Segment 82 Segment 83 Segment 84 DLC film adhering to projection 90 Contact member 122 Stator (or slider)

Claims (8)

A method of forming an inorganic film having a segment structure in which the edge portion of a segment is rounded on a film formation surface of a friction contact surface,
A metal layer forming step of forming a metal layer for mask formation made of a conductive metal on the film-forming surface;
A mask forming step of etching the metal layer to form a protrusion of the metal layer at a position to be a groove partitioning the segment;
It is placed on a substrate holder that constitutes an electrode so that the film-forming surface on which the protrusion of the metal layer is formed is exposed, and the protrusion of the protrusion is formed using physical vapor deposition or chemical vapor deposition. A film forming step of forming an inorganic film having a thickness in which an edge portion facing the protrusion is rounded in a predetermined shape on a film forming surface in between;
A mask removing step of removing the protrusion of the metal layer;
An inorganic film forming method comprising:   The inorganic film forming method according to claim 1, wherein the inorganic film is a DLC film.   3. The inorganic film forming method according to claim 1, wherein the inorganic film is formed using a plasma CVD method in the film forming step.   4. The method of forming an inorganic film according to claim 1, wherein the thickness of the metal layer is changed, the height of the protrusion is changed, and the curvature of the edge portion facing the protrusion is rounded. A method for forming an inorganic film, characterized in that:   5. The inorganic film forming method according to claim 1, wherein Cu or Al is used as the metal layer.   6. The inorganic film forming method according to claim 1, wherein an intermediate layer having high adhesion to the inorganic film is formed on the film formation surface prior to the metal layer forming step. An inorganic film forming method.   7. The inorganic film forming method according to claim 6, wherein a Cr layer is formed as the intermediate layer when the inorganic film is a DLC film.   The inorganic film forming method according to claim 2, wherein the friction contact surface on which the DLC film is formed is a friction driving surface of a stator or a mover of an ultrasonic motor.