JP2008170160A - Specimen for bending fatigue detection, and bending fatigue test method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a specimen for bending fatigue detection that does not directly handle a minute test piece and accurately applies a load to a certain position of the test piece, in a bending fatigue test of a micro material. <P>SOLUTION: The specimen 6 for bending fatigue detection is used for testing a fatigue to the bending of the micro material. The specimen 6 for bending fatigue detection comprises the test piece 1 of a cantilever shape, an abutting section 5 that can abut on the tip of the test piece 1, a central member 2 for applying displacement to the test piece 1, and a frame member 4 for fixing test piece 1 and the micro material except the central member 2. A base end 7 of the test piece 1 displaces relatively in the vertical direction with respect to the abutting section 5, thereby putting the test piece 1 into the bent state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a specimen for detecting bending fatigue of a micromaterial and a bending fatigue testing method using the specimen for detecting bending fatigue.

  At present, the development and production of micromachines or MEMS are progressing by micromachining, which is an application of semiconductor microfabrication technology. In micromachines, structures such as cantilever beams, bridges, and membranes with micro / nanometer dimensions are formed. Sensors and actuators that actively use deformations of these structures, and electrical devices for controlling or detecting these deformations There are many micromachine devices in which circuit elements are integrated on the same device.

  As a result, materials that have not been used as mechanical elements, such as silicon and silicon compounds, or metal or organic films deposited on substrates, have been used as structural members for micromachine devices. And exercise determine the function of the device. In addition, destruction due to deformation and fatigue due to repeated loads affect the reliability of the device. In particular, when a device is commercialized, high reliability is required, and it is necessary to clarify the fatigue phenomenon of the structure in order to avoid a decrease in device function due to the deterioration of the structure.

Conventionally, a mechanical fatigue test using a bending test such as three-point bending or four-point bending has been used. As a fatigue test method for micromaterials to which this is applied, there is a method of measuring a fatigue life by producing a cantilever-shaped micro test piece and applying a load repeatedly to the free end of the test piece. For example, Patent Document 1 discloses a fatigue test apparatus in which a microscale cantilever is fixed in a vertical position for the purpose of avoiding deformation due to the influence of gravity. The invention of Patent Document 2 is a test apparatus that can alternately apply compression-tensile stress to the produced cantilever.
JP-A-2005-249590 Japanese Patent Laid-Open No. 2005-37361

  By the way, the target micromaterial for the test apparatus is very small, and the error when attaching the test piece to the test apparatus or the deviation of the load point position under repeated load is relatively large as the test piece becomes smaller. Become. In order to measure the generated minute displacement and the applied bending stress with high accuracy, it is preferable to apply a load to the same position and keep this state. On the other hand, a mechanical gripping method is generally used as a method for fixing a small specimen, but it is difficult to apply it to micromaterials, and in a fatigue test over a long period of time, the gripping condition under the same conditions is used. It is difficult to guarantee.

  An object of the present invention is to provide a highly accurate and reliable test body for detecting bending fatigue that does not require alignment and the like that cause uncertainty in bending fatigue testing of micromaterials. An object of the present invention is to provide an excellent test method using a fatigue detection specimen.

In order to solve this problem, the present invention provides a bending fatigue detection test body for testing fatigue against bending of a micromaterial, a substrate including a film made of the micromaterial, and the micromaterial. By processing a film made of the above, a cantilever-shaped test piece having a free end on the tip side, and a contact with the tip of the test piece formed by processing the micromaterial and the substrate A possible contact portion, a fixing portion for fixing the bending fatigue detection specimen when testing fatigue against the bending, and a tip portion of the test piece and the contact portion for performing the fatigue test. And a transition imparting portion for imparting a relative displacement between the contact portions.
In the case of such a specimen for detecting bending fatigue, the tip of the cantilever-shaped specimen is applied by applying a transition to the transition applying section in a state where the specimen for detecting bending fatigue is fixed by the fixing section. The test piece is brought into contact with the contact portion to induce bending deformation. As a result, a fatigue test in which the test piece is in a bent state is performed. However, in this test specimen for detecting bending fatigue, alignment that causes uncertainty in the conventional bending fatigue test of micromaterials is unnecessary. Become.

  According to a second aspect of the present invention, in the test body for detecting bending fatigue according to the first aspect, the test piece is formed of a film formed on a silicon substrate. Thereby, the fatigue test of the film formed on the silicon substrate can be performed.

  According to a third aspect of the present invention, in the bending fatigue detection test body according to the first or second aspect, a measurement unit that electrically detects a change in a state generated in the test piece.

According to a fourth aspect of the present invention, there is provided a bending fatigue test method for testing using the bending fatigue detection specimen according to the first or second aspect.
With the test piece for bending fatigue detection fixed at the fixed part, the tip of the cantilever-shaped test piece is brought into contact with the contact part by applying a transition to the transition imparting part. A bending fatigue test method characterized by inducing bending deformation in the test piece.

When using the test specimen for detecting bending fatigue of the present invention, in a bending fatigue test of a micromaterial, a minute test piece is not directly handled, and a load can be accurately applied to a predetermined position of the test piece. Positioning that causes uncertainty in the bending fatigue test of materials becomes unnecessary.
And in the bending fatigue test using the test body for detecting bending fatigue according to the present invention, the alignment work of the minute test piece is omitted, so that complicated procedures are reduced and the work efficiency can be increased. Further, unlike a conventional test, since a minute test piece is not directly handled, there is an effect that damage to the test piece before the test can be avoided.
Furthermore, since the contact part of the test piece is provided inside the test body for detecting bending fatigue, when a load is repeatedly applied to the test piece, the load can always be applied to the correct position of the test piece. it can.
According to the third aspect of the invention, since the material to be tested is formed on the surface of the test piece and the wiring to be electrically inspected is formed, it is possible to easily detect an abnormality in the wiring due to the action of an external force.

FIG. 1 is a perspective view showing a configuration of a test specimen for detecting bending fatigue of a micromaterial according to the present invention. FIG. 2 is a cross-sectional view taken along line AA ′ in FIG. FIG. 2B is a diagram showing a state after the deformation, and FIG.
The test body 6 for detecting bending fatigue includes a cantilever-shaped test piece 1, a central member 2 that holds the test piece 1, a beam member 3 that is connected to the central member 2, and a frame that is connected to the beam member 3. A member 4 and a contact portion 5 located on the tip side of the test piece 1 are provided.
In the case of this embodiment, the test piece 1 is arranged in the uppermost layer so as to protrude from the block-shaped central member 2 at the center of the bending fatigue detection test body 6 to the left and right. The central member 2 is connected to a frame member 4 located on the outer periphery of the central member 2 by four beam members 3. The frame member 4 includes a pair of contact portions 5 at positions facing the left and right test pieces 1, and the contact portions 5 are stepped so as not to apply a bending load to the test piece 1 in the initial stage.
As shown in FIG. 2, the test piece 1 is fixed to the central member 2 at the base end portion 7. The contact portion 5 is stepped so as to be located slightly below the test piece 1 and is not in contact with the test piece 1 in the initial state. The central member 2 functions as a transition imparting portion for imparting a displacement to the test piece 1, and the frame member 4 is one of fixing portions for fixing the micromaterial other than the test piece 1 and the central member 2. It functions as a part.
2B, when the central member 2 is relatively displaced in the direction of the arrow 8 and the frame member 4 is relatively displaced in the direction of the arrow 9, the tip of the test piece 1 is brought into contact with the contact portion 5. On the other hand, it moves relatively up and down and comes into contact. In this case, the four beam members 3 arranged on the object serve as a guide portion, and the relative movement becomes accurate.
As shown in FIG. 1 and FIG. 2, by arranging two test pieces 1 at two symmetrical positions of the central member 2 to form a symmetrical shape, the central member 2 is kept in a balanced state until one of them is broken. Moving. Then, the fatigue test is performed by bringing the tip of the cantilever-shaped test piece 1 into contact with the contact portion 5 and inducing bending deformation in the test piece 1 so that the test piece 1 is in a bent state. .

Next, an example of a manufacturing process of the bending fatigue detection test body 6 when single crystal silicon is used as a test material will be described with reference to FIG.
A single crystal silicon substrate 10 having a thickness of 350 μm is prepared as a starting material for the test body 6 for detecting bending fatigue. Further, an SOI wafer in which an active layer 11 of single crystal silicon having a thickness of 10 μm is bonded by a silicon oxide film 12 is prepared as a micromaterial to be a test material. A resist 13 is applied to the active layer 11 and patterned by photolithography (see FIG. 3A). Using this resist 13 as a mask material, reactive ion etching with sulfur hexafluoride gas is performed on the active layer 11 to determine the shapes of the test piece 1 and the beam member 4. Thereafter, the resist 13 used as a mask material is removed with acetone (see FIG. 3B).
Next, the SOI wafer is thermally oxidized at 1100 ° C. to form a silicon oxide film 14 on the entire surface, and the back surface is patterned by photolithography (see FIG. 3C). The silicon substrate is etched with an aqueous potassium hydroxide solution, and when the remaining amount becomes about 100 μm, the chemical solution is changed to a predetermined aqueous solution and etching is continued (see FIG. 3D). By changing the chemical solution, etching up to the silicon oxide film 12 between the silicon substrate 10 and the active layer 11 can be performed in a reproducible state without excess or deficiency. Finally, the silicon oxide films 12 and 14 on the wafer surface and the lower side of the test piece are removed by etching with a mixed solution of hydrofluoric acid and ammonium fluoride, thereby completing the test body 6 for detecting bending fatigue (see FIG. 3 (e)).
By processing the micro material by such a method, the cantilever-shaped test piece 1 having a free end at the tip side is formed, and the micro material and the silicon substrate 10 are processed, thereby the test piece. The abutting portion 5 that can abut on the tip portion of 1 is formed.

When a material other than silicon is used as a test piece, a silicon substrate is previously thermally oxidized to form a silicon oxide film on the surface, and then a film to be a test material is formed on the upper surface by vapor deposition / sputtering or the like. Processing of the formed test material can be performed in the same process as FIGS. 3A to 3B, and processing of the silicon substrate can be performed in the same process as FIGS. 3C to 3D. However, the silicon oxide film 14 formed on the entire surface in FIG. 3C is substituted with a silicon nitride film, a metal film, an organic film, or the like.
By using such a test body, a fatigue test of the test piece 1 made of a silicon oxide film, a silicon nitride film, a metal film, an organic film or the like can be performed.
Next, a bending fatigue test apparatus will be described. 4 is a front view, and FIG. 5 is a perspective view of the entire bending fatigue test apparatus. FIG. 4 shows a view as seen from the arrow 15 in FIG. However, for ease of explanation, in FIG. 4, a set of lasers 29 and optical sensors 26 for detecting displacement is omitted, and in FIG.
4 and 5, the bending fatigue test apparatus 50 includes a holder 16 for fixing the test body 6 for detecting bending fatigue. The holder 16 is attached to an actuator (not shown) that is driven in the vertical direction, and the actuator is attached to the actuator holder 17. The actuator holder 17 is attached to the XYZ stage 18 via four bolts. The XYZ stage 18 is fixed on a base 19, and the base 19 is installed on a vibration isolation table 20. Two side support members 21 made of a flat plate are attached on the base 19, and an upper support member 22 made of a flat plate is attached to the upper portion of the side support member 21.

  The bending fatigue test apparatus 50 includes a force sensor 23 composed of a laminated piezoelectric body, and a square columnar block 24 at the tip of the force sensor 23. The force sensor 23 is fixed to the upper support member 22 with an adhesive. The lower surface of the block 24 is set to be smaller than the upper surface of the central member 2, and alignment is performed using the XYZ stage 18 so that the block 24 is arranged directly above the central member 2. Note that the force sensor 23 may be a load cell, a strain gauge type sensor according to the load cell, or the like in addition to the laminated piezoelectric body.

  A prism mirror 25 (shown as 25a and 25b in FIGS. 5 and 6) having a right-angled isosceles triangular prism with a 45-degree slope mirror coating is placed on the upper support material 22 and at a position with the force sensor 23 as an axis of symmetry. It is fixed with an adhesive. An optical sensor 26 composed of a two-divided photodiode and a circuit is attached to an XY stage 28 via a fixed member 27 made of a flat plate, and the XY stage 28 is fixed to the base 19.

Next, a bending fatigue test method for the bending fatigue detection test body 6 using the bending fatigue test apparatus 50 will be described in detail.
A circular or square hole or recess is provided in the center of the holder 16, and when the bending fatigue detection test body 6 is fixed, only the frame member 4 contacts the holder 16 and is disposed on the hole or recess. The central member 2 can move freely in the vertical direction. A portion of the frame member 4 that contacts the holder 16 functions as a fixing portion for fixing the bending fatigue detection test body 6.
After fixing the test body 6 for detecting bending fatigue to the holder 16, the central member 2 and the block 24 are opposed to each other using the XYZ stage 18, and the central member 2 and the block 24 are brought into contact by moving the XYZ stage 18 upward. . The contact point is specified by the point at which the detection value from the force sensor 23 increases rapidly.

The actuator holder 17 is used to fix an actuator that is driven in the vertical direction to the XYZ stage 18, but may be omitted depending on the form of the actuator. In this embodiment, a voice coil motor is used for the actuator. The actuator may be a piezoelectric element that generates displacement by an electric signal.
The actuator can reciprocate in the vertical direction, is connected to a signal generator (not shown), and is driven by a control signal from the signal generator. The drive of the actuator is transmitted to the bending fatigue detection test body 6 through the holder 16, and the frame member 4 is driven in the vertical direction. When the center member 2 is restrained from being displaced upward by the force sensor 23 and the frame member 4 is driven above the contact point, the center member 2 is positioned between the center member 2 and the frame member 4 or between the contact portion 5 of the test piece and the base member 2. A relative displacement occurs between the ends 7.

6A and 6B are diagrams showing a method of detecting the displacement generated in the frame member 4 in the bending test, FIG. 6A is a view seen from above, and FIG. 5B is a front view.
The laser light oscillated from the laser 29 passes through the optical path 30 and is incident on the prism mirror 25a, bent to the optical path 31, and applied to the bending fatigue detection test body 6. The reflected light from the bending fatigue detection specimen 6 enters the prism mirror 25 b through the optical path 32 and enters the optical sensor 26 through the optical path 33. As shown in FIG. 6, a prism mirror 25a, 25b are placed together as viewed from the top 45 ^o, with tilted 45 ^o when viewed from the front. The optical path difference caused by the vertical displacement of the bending fatigue detection specimen 6 is converted into an electrical signal by the optical sensor 26 and detected.

  The displacement can also be measured by manufacturing a strain gauge at the base of the beam member 3 by a semiconductor process.

  Next, a second embodiment of the test body for detecting bending fatigue will be described. FIG. 7 shows a specimen 34 for detecting bending fatigue according to the second embodiment. That is, the two test pieces 35 are fixed to the frame member 36, the abutting portion 37 is provided on the opposing central member 38, and the base end portion 39 is a connecting portion between the test piece 35 and the frame member 36. The central member 38 functions as a transition imparting portion for imparting displacement to the contact portion 37, and the frame member 36 functions as a part of a fixing portion for fixing the bending fatigue detection test body 34. To do.

  In the bending fatigue detection test body 6 or the bending fatigue detection test body 34, a metal material as a test material is formed on the test piece 1 such as silicon, and a change in an electric signal due to bending fatigue is measured, whereby a material is obtained. It is also possible to detect abnormalities that occur in

FIG. 8 is a diagram of a test piece on which a metal wiring for detecting an abnormality is formed. FIG. 8A shows a wiring pattern formed on the test piece, and FIG. 8B shows a test piece protruding in a U-shape. A wiring pattern is formed thereon. In this case, the test body for detecting bending fatigue includes a measuring unit that electrically detects a change in the state generated in the test piece.
Specifically, a U-shaped wiring pattern 40 made of a metal film and an electrode pad 41 for taking out an electric signal to the outside are formed on the test piece 1 or the test piece 35. The electrode pad 41 is formed on the central member 2 (when the test piece 1 is supported by the central member 2) or the frame member 4 (when the test piece 1 is supported by the frame member 4). By measuring the electrical resistance of the wiring pattern 40 through the electrode pad 41, the electrical deterioration of the wiring material due to the bending fatigue test can be measured.
The present invention is not limited to the description of the embodiment of the invention. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims.

FIG. 1 is a perspective view of a test body for detecting bending fatigue of a cantilever in an embodiment of the present invention. FIG. 2 is a cross-sectional view of the specimen in FIG. FIG. 3 is a process diagram of a bending fatigue detection specimen. FIG. 4 is a front view of a part of the bending fatigue test apparatus. FIG. 5 is a perspective view of the entire bending fatigue test apparatus. FIG. 6 is a conceptual diagram showing irradiation of a laser beam for measuring the displacement amount of the specimen. FIG. 7 is a perspective view showing a second embodiment of a test body for detecting bending fatigue according to the present invention. FIG. 8 shows a cantilever test piece on which a wiring pattern is formed.

Explanation of symbols

1, test piece 2, central member 3, beam member 4, frame member 5, contact portion 6, bending fatigue detection test body 7, proximal end portion 16, holder 17, actuator holder 18, XYZ stage 23, force sensor 24 , Block 25, prism mirror 26, optical sensor 29, lasers 30, 31, 32, 33, optical path 34, test body 50 for detecting bending fatigue, bending fatigue test apparatus

Claims (4)

In a test specimen for detecting bending fatigue, which tests fatigue for bending of micromaterials,
A substrate comprising a film made of the micromaterial;
By processing the film made of the micromaterial, a cantilever-shaped test piece having a free end on the tip side, and
An abutting portion formed by processing the micromaterial and the substrate, the abutting portion being able to abut on a tip portion of the test piece;
When testing fatigue against the bending, a fixing portion for fixing the bending fatigue detection specimen,
In order to perform the fatigue test, a bending fatigue detection test body having a displacement imparting portion for imparting a relative displacement between a tip portion of the test piece and the contact portion. In the specimen for bending fatigue detection according to claim 1,
The test piece for detecting bending fatigue, wherein the test piece is formed of a film formed on a silicon substrate. In the specimen for bending fatigue detection according to claim 1 or 2,
A test body for detecting bending fatigue, comprising a measuring section for electrically detecting a change in a state generated in the test piece. In a bending fatigue test method for testing using the bending fatigue detection specimen according to claim 1 or 2,
In the state where it is fixed by the fixed part, the tip of the cantilever-shaped test piece is brought into contact with the abutting part by imparting a transition to the transition-giving part, and the cantilever-shaped test piece is bent and deformed. A bending fatigue test method characterized by inducing.

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