JP2005201908A - Micro material testing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micro material testing apparatus capable of directly and highly accurately measuring and evaluating dynamic characteristics of micro materials in original form, and a dynamic characteristic evaluation method thereby. <P>SOLUTION: A sample stage part of a scanning probe microscope 2 is provided with a micro tension/compression testing mechanism 3 provided with both an actuator for loading a micro test piece 1 with a tensile or compressive load and a means for detecting the load on the micro test piece 1. Micro distortion of the test piece 1 due to the tensile or compressive load is measured through the use of a sample surface observation system of the scanning probe microscope 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a micromaterial testing apparatus for measuring the mechanical properties of a micromaterial, for example, its mechanical properties with high accuracy, and a mechanical property evaluation method using the same.

  Advances in semiconductor processing technology have led to higher integration and higher performance of electronic devices used in micromachines, etc. In order to improve the reliability of these micro devices, high-precision mechanical characteristics are required. It is important to measure and evaluate. In addition, in order to evaluate the mechanical properties of silicon-based micromaterials configured as protective films and functional thin films for these devices, it is necessary to measure the properties of the devices under minute dimensions and apply the data obtained in the design to these devices. is there. However, this silicon-based micromaterial, such as a semiconductor silicon-based thin film or a diamond-like carbon thin film (DLC), has a very small dimensional configuration, and it is extremely difficult to evaluate its mechanical characteristics with high accuracy.

  Conventionally, the bimetal method, the vibration lead method, etc. have been proposed as methods for measuring the mechanical properties of these micromaterials, but the bimetal method has to assume the Poisson's ratio when determining the Young's modulus. There is a problem, and in the vibration reed method, Young's modulus can be measured accurately, but Poisson's ratio cannot be measured. In contrast, the tensile test method is also an effective test method for Poisson's ratio measurement, but because there is a limit on the sample size, highly accurate strain measurement is possible for this type of ultra-small sample. There was a disadvantage that it was not possible.

  In addition, silicon-based thin film materials, diamond-like carbon thin films (DLC), which are used as protective films and functional thin films for electronic parts and the like and cannot retain their shapes, and polymer thin films for micromachines are described above. In order to evaluate this thin film material, it is necessary to evaluate it by computer simulation using physical property values of other materials.

  Thus, with the conventional technology, the mechanical properties of micromaterials cannot be measured with high accuracy, and the reliability of measured values cannot be expected, especially for thin film materials that cannot retain their shape by themselves. There was a problem.

  The present invention is to solve the above-mentioned problems in response to the nanotechnology era, and provides a micromaterial testing apparatus that can directly measure and evaluate the mechanical properties of micromaterials in their original form with high accuracy.

  The micromaterial testing apparatus according to the present invention includes a means for mounting a micro test piece having a micro line pattern having at least a plurality of concavo-convex lines parallel to each other on the surface of a stage portion of a scanning probe microscope, An actuator for applying a tensile or compressive load to the micro-test specimen formed, a means for detecting the load applied to the test specimen by the actuator, and / or a probe or stage part on the surface of the micro-line pattern. A scanner that scans in the XYZ-axis direction, and a means that measures the strain of the micro test piece from the mechanical / electromagnetic interaction between the micro line pattern and the probe by scanning the scanner with a load applied to the test piece by the actuator The Young's modulus of the minute test piece is calculated from the outputs of the load detection means and the strain measurement means.

  Preferably, the micro line pattern is a line pattern formed in a lattice shape, and the strain measuring means measures both the longitudinal strain and the lateral strain of the micro test piece, and the Young's modulus and Poisson's ratio of the micro test piece are measured. Both are calculated.

  More preferably, the actuator has two functions for fine movement and coarse movement.

  According to the conventional technique, as described above, the mechanical characteristics of the micromaterial used in the micromachine or the like cannot be accurately measured. However, according to the present invention, the mechanical properties of the micromaterial can be directly measured and evaluated with high accuracy in its original form. By measuring the mechanical characteristics with high accuracy, it can be used in a very wide range such as designing a micromachine using a micromaterial, designing and simulating a device / electronic component coated with a micromaterial thin film.

BEST MODE FOR CARRYING OUT THE INVENTION

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In this embodiment, a tensile load is applied to the sample and the mechanical properties of the sample are measured. However, it is also possible to measure by applying a compressive load in the same manner.

  First, a method for measuring the mechanical properties of a sample using one embodiment of the micromaterial testing apparatus according to the first invention will be described with reference to FIG. Hereinafter, this example is referred to as a first example. FIG. 1 is an explanatory diagram of the first embodiment. In this embodiment, the sample for measuring the mechanical properties is a micro thin film material such as a semiconductor silicon thin film or a compound semiconductor thin film, and the shape is maintained even when used in a micromachine or the like.

  In FIG. 1, reference numeral 2 schematically shows a part of the housing of the scanning probe microscope. In this embodiment, the present invention is applied to an atomic force microscope that measures the shape of the surface of a sample with high precision by detecting an atomic force acting between a probe (probe) 21 and a test piece 1. It is. In this example, a scanner 22 using voice coil actuators 23, 23 ′, 23 ″ is used, and a probe 21 is cantilevered by a cantilever 24 attached to the lower side of the scanner 22. Is precisely scanned in the three-dimensional (XYZ axis) direction. Of course, the probe can be scanned even if a piezo-type scanner is used.

  In the present embodiment, the micro-tension test mechanism 3 provided in the sample stage portion below the probe 21 is provided, and the test piece 1 is fixed on the mechanism 3. The test piece 1 includes a bridge portion 11 having a very small width, and a surface of the bridge portion 11 is provided with a minute lattice-like line pattern 12 serving as a mark.

  First, when a tensile load P is applied to the test piece 1 by the micro tensile test mechanism 3, a stress σ is generated in the bridge portion 11. In this state, the change in the line pattern 12 is observed by the sample surface observation system of the scanning probe microscope 2 to measure the minute longitudinal strain ε and lateral strain ε ′ of the test piece 1 due to the tensile load P. At this time, by observing the line pattern 12 at the same time as applying the tensile load P, the longitudinal strain ε and the lateral strain ε ′ of the bridge portion 11 can be measured quickly and accurately.

  In this embodiment, the distortion of the bridge portion 11 of the micro sample by the scanning probe microscope 2 is measured by the following procedure. By scanning with the scanner 22, the probe 21 is placed on the surface of the bridge portion 11 of the test piece 1. In this state, the probe 21 is scanned in the X and Y directions by the scanners 23, 23 ″. The scanning of the scanner 22 in the Z-axis direction is controlled so that the interatomic force acting between them is constant. The amount of feedback in the Z-axis direction corresponding to the position in the XY-axis direction is detected as an output voltage of the scanner 22, and this is output on the screen as a three-dimensional image via the arithmetic unit, that is, the surface of the bridge unit 11, that is, The change of the line pattern 12 is observed.

  In this embodiment, an atomic force acting between the probe 21 and the test piece 1 is used. However, a mechanical current and an electromagnetic force such as a tunnel current and a magnetic force acting between the probe 21 and the test piece 1 are used. It is also possible to measure and detect the distortion of the line pattern 12 by taking in the feedback amount using the action.

  Then, the stress σ, the longitudinal strain ε, and the lateral strain ε ′ measured as described above are substituted into the following formulas 1 and 2, and the Young's modulus E and Poisson's ratio ν, which are the mechanical characteristics of the sample, are calculated.

  E = σ / ε (Equation 1)

  ν = − (ε ′ / ε) (Equation 2)

  A specific example of the test piece 1 will be described with reference to FIGS. The test piece 1 is made of a silicon-based micromaterial such as a semiconductor silicon-based thin film or a compound semiconductor thin film, and retains its shape even when used in a micromachine.

2A is a plan view of the test piece 1, and B is an enlarged perspective view of the line pattern 12. FIG. As shown in FIG. 2A, the test piece 1 has an overall size configuration of, for example, a length L ₁ of 27 mm, a width W ₁ of 13 mm, and a thickness of 0.5 mm. 10 is provided, and a very narrow bridge portion 11 is provided to span the space portion 10.

The bridge portion 11 is a target portion for measuring the mechanical properties of the sample, the size is the size of the actual use of the sample, as shown in FIGS. 2A and 3, for example, a length L ₂ 3 mm, width W ₂ is 0.3 mm, thickness t is 20 μm (0.02 mm), and a fine grid-like line pattern 12 serving as a gauge point is provided at the center of the surface. FIG. 3 shows an enlarged perspective view of the bridge portion 11.

Further, the test piece 1 is provided with holes 14 and 14 'engaged with a chuck for a tensile test, which will be described later, on both ends, and the holes 14 and 14' are about 3 mm square. As shown in Figure 2B, the line pattern 12, the dimensions _{W 3} of the line portion 13 and the interval 20 [mu] m, the thickness t 'of the line portion 13 is made extremely fine pattern structure 200 nm (0.0002 mm) .

  Next, the tensile test mechanism 3 provided in the sample stage portion of the scanning probe microscope 2 will be described with reference to FIG. FIG. 4 shows a plan view of the tensile test mechanism 3. The tensile test mechanism 3 includes chuck portions 30 and 30 ′ that hold the test piece 1, and projecting portions 31 and 31 ′ that engage with the holes 14 and 14 ′ of the test piece 1 on the upper surface. It has. The chuck portions 30 and 30 ′ include the function of the sample stage portion for the scanning probe microscope 2.

  Reference numerals 32 and 32 ′ denote piezoelectric element actuators for applying a tensile load to the test piece 1 via the chuck portion 30, a fine movement actuator 32 that applies ultrafine movement to the chuck portion 30, and a coarse movement actuator 32 that moves greatly. The fine movement actuator 32 and the coarse movement actuator 32 ′ are selectively used according to the mechanical characteristics of the test piece 1 or according to the measurement purpose. That is, when measuring the test piece 1 having a high strength, the coarse movement actuator 32 'is used, and when measuring the test piece 1 having a low strength, the fine movement actuator 32 is used.

  Reference numeral 33 denotes a load cell that detects a tensile load P applied to the bridge portion 11 of the test piece 1, and reference numeral 34 denotes a differential displacement meter. When the tensile test mechanism 3 is used, the chuck portions 30 are moved by engaging the holes 14 and 14 'of the test piece 1 with the projecting portions 31 and 31' and operating the actuators 32 and 32 '. It moves and pulls the bridge part 11 in the axial direction.

  Next, a method for measuring the mechanical properties of a sample using one embodiment of the micromaterial testing apparatus according to the second invention will be described with reference to FIG. Hereinafter, this example is referred to as a second example. FIG. 5 is an explanatory diagram of the second embodiment. In this embodiment, the test piece 1 for measuring mechanical properties is a micromaterial such as a diamond-like carbon thin film (DLC) or a polymer thin film for micromachine. In this embodiment, a sample that cannot be measured in the first embodiment described above can be measured. That is, when used in a micromachine or the like, it is used as a laminated protective film or functional thin film, and the shape itself is not maintained.

  In this embodiment, the description of the same configuration as in the first embodiment is omitted. As shown in FIG. 5, the bridge portion 11 of the test piece 1 is used as a substrate, the sample 11 ′ is placed on the surface, and the tip of the probe 21 of the scanning probe microscope 2 is a hard sharp indenter. Is a diamond indenter.

First, in the same manner as in the first embodiment, the tensile load P is applied to the bridge portion 11 by the micro tensile test mechanism 3 to obtain the longitudinal strain ε and the stress σ of the sample 11 ′. By substituting into, the combined Young's modulus E _{1 + 2} of the sample 11 ′ and the substrate 11 is calculated.

The previously measured Young's modulus _{E 2} of the substrate 11 in the first embodiment, the synthetic Young's modulus _{E 1 + 2,} the thickness _{t 1} of the specimen 11 'shown in FIG. 6, and the thickness _{t 2} of the substrate 11 in equation 4 below Substituting and calculating the Young's modulus E ₁ of the sample 11 ′. FIG. 6 shows an enlarged perspective view of the bridge portion 11 and the sample 11 ′. Thickness t ₁ of the specimen 11 'in this embodiment is 0.3 [mu] m, other dimensions configuration is the same as the first embodiment.

E _{1 + 2} = σ / ε (Equation 3)

E _{1 + 2} = (t ₁ · E ₁ + t ₂ · E ₂ ) / (t ₁ + t ₂ ) (Equation 4)

  Since the sample 11 ′ used in this example is very thin, the shapes of the upper and lower surfaces when the tensile load P is applied are different, and the lateral strain ε ′ cannot be measured by the same method as in the first example. . Therefore, the method described below is performed.

  The scanner 22 of the scanning probe microscope 2 is scanned in the Z-axis direction, the tip of the probe 21 is pushed into the sample 11 ′, the pushing load P ′, and the depth of the indentation 50 on the surface of the sample 11 ′ formed thereby. Measure h. In this embodiment, the indentation test is performed four times in order to increase the reliability, and the slope (dP ′ / dh) 71 of the test curve 70 performed for the fourth time is determined from FIG. 7. FIG. 7 is a graph showing the relationship between the pushing load P ′ and the pushing amount h.

  The depth h of the indentation 50 is measured by applying the laser beam 27 irradiated from the laser diode 25 to the cantilever 24 and sensing the reflected beam 27 ′ by the photodetector 26 in a state where the indentation load P ′ is applied. To do. The indentation load P ′ is calculated from the spring constant of the cantilever 24 and the amount of deflection.

Further, the area A ′ of the indentation 50 is measured by the area measuring means. The area measuring means is made of software for processing the image of the indentation 50 using the scanning probe microscope 2 and measuring the area A ′ from the image. Then, the slope (dh / dP ′) and the area A ′ are substituted into the following formula 5 to calculate the synthetic Young's modulus Er of the indenter (made of diamond) 21 and the sample 11 ′. Then, the synthetic Young's modulus Er, the Young's modulus E ₁ of the sample 11 ′ derived from the above, the Poisson's ratio νi of the indenter and the Young's modulus Ei measured in advance are substituted into Equation 6 below, and the Poisson's ratio ν _{1 of the} sample 11 ′. Is calculated.

Formula 5

Equation 6

  In the apparatus in the two embodiments described above, the scanner 22 of the scanning probe microscope 2 scans the probe 21, but the scanner 22 may scan the sample stage portion, and even in that case, the present invention is also applicable. It is natural to obtain the effect of.

Explanatory drawing of a 1st Example is shown. Explanatory drawing of a test piece is shown. The enlarged view of the bridge | bridging part of a 1st Example is shown. The top view of a tension test mechanism is shown. Explanatory drawing of a 2nd Example is shown. The bridge part of a 2nd Example and the enlarged view of a sample are shown. The graph of the relationship between indentation load P 'and indentation amount h is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Test piece 2 Scanning probe microscope 3 Micro tensile test mechanism 21 Probe 32 Actuator 50 Indentation

Claims (3)

  Means for placing a micro test piece having a micro line pattern having a plurality of parallel concave and convex lines on the surface thereof on the stage of a scanning probe microscope, and a tensile or compressive load on the placed micro test piece A means for detecting a load applied to the test piece by the actuator, a scanner for scanning both or one of the probe and the stage unit on the surface of the minute line pattern in the XYZ axis direction, And means for scanning the scanner in a state where a load is applied to the test piece by the actuator, and measuring the strain of the micro test piece from the mechanical / electromagnetic interaction between the micro line pattern and the probe. And the Young's modulus of the minute test piece is calculated from the outputs of the load detection means and the strain measurement means. Micro material testing apparatus according to claim.   The micro line pattern is a line pattern formed in a lattice shape, and the strain measuring means measures both the longitudinal strain and the lateral strain of the micro test piece, and the Young's modulus and Poisson's ratio of the micro test piece Both of these are calculated, The micromaterial test apparatus of Claim 1 characterized by the above-mentioned.   The micromaterial testing apparatus according to claim 1 or 2, wherein the actuator has two functions for fine movement and coarse movement.

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