JP4037275B2 - Surface shape measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface shape measuring apparatus such as a probe microscope that measures a hole or groove shape using a probe (probe).
[0002]
[Prior art]
In recent years, semiconductors have been further miniaturized, and an atomic force microscope which is a kind of probe microscope having atomic resolution is expected as a shape measurement as an evaluation of a fine shape. Atomic Force Microscope (AFM) is the inventor of STM G. Since it was devised by Binnig et al., It is expected to be a means for observing the surface shape of a novel insulating material, and research has been conducted. The principle is that the atomic force acting between the detection tip having a sufficiently sharp tip and the sample is measured as the displacement of the spring element to which the detection tip is attached, and the displacement of the spring element is kept constant while the sample surface is kept constant. , And the shape of the sample surface is measured using a control signal for keeping the amount of displacement of the spring element constant as shape information.
[0003]
As the displacement detection means of the spring element, there are an optical system and a self-detection system that detects a deformation strain of the spring element as an electric signal.
[0004]
As an example of using the so-called interferometry itself as an optical method, Journal of Vacuum Science Technology A6 (2) p266 Mar / Apr 1988 (Non-patent Document 1) irradiates a spring element with a laser beam and shifts the position of the reflected light. Journal of Applied Physics 65 (1), 1 p164 January 1989 (Non-Patent Document 2) has been reported as an example of an optical lever method in which a light detection element detects a displacement signal. At present, the optical lever method is mainly used as a detection method of the probe microscope. Also, as a type of so-called self-detecting type that captures the amount of deflection of the cantilever as a change in resistance value, so-called self-detecting type, Japanese Patent Application Laid-Open No. 2000-111563 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2001-337025 (Patent) There are those described in Document 2).
[0005]
A probe microscope is called an atomic force microscope if a probe placed at a position opposite to the sample receives an atomic force from the sample, and various probes generated from the sample are called a magnetic force microscope if it is a magnetic force. The force can be detected and the state of the sample can be observed. As the structure of the probe microscope, when the observation sample is small, the sample is mainly arranged on the side of the fine movement mechanism that moves in three dimensions, which incorporates a piezoelectric element that deforms when a voltage is applied. There is a need to observe semiconductor-related wafer samples without making them small. Therefore, there is a probe microscope having a configuration in which a displacement detection system is provided on the fine movement mechanism side. As a basic operation, the probe microscope operates the fine movement mechanism in the plane and moves the probe configured in the spring element in the plane with respect to the sample surface, thereby deforming the spring element by the physical force acting between the sample and the probe. The surface shape and state of the sample are visualized based on the result of moving the fine movement mechanism in the vertical direction.
[0006]
A probe used in a probe microscope is formed at the tip of a cantilever member called a cantilever as shown in FIG. 2, and has a quadrangular shape mainly as shown in FIG. The material is silicon and is processed using anisotropic etching techniques. Usually, since the height of the probe formed at the tip is as low as about 1 to 2 μm, the cantilever is attached to the probe microscope so that the cantilever base does not hit the sample surface. On the other hand, in the probe having the above shape, when a hole or groove formed of a semiconductor or the like, particularly when the aspect ratio (height / width) is large or deep, or when the sample angle is larger than the probe's shape angle, An appropriate shape measurement cannot be performed (FIG. 4). On the other hand, there have been devised ones in which the probe shape is further processed into a rod shape, or another material such as tungsten or carbon is formed on the probe tip (FIG. 5). A shape having a large aspect ratio can be measured by the rod-shaped probe, but depending on the angle relationship between the rod-shaped probe and the sample tilt with respect to the sample and Z-direction tracking, the probe is placed on the shape-shaped side wall as shown in FIG. In the meantime, the bottom of the shape is not reached and correct measurement cannot be performed. Although it is conceivable to manage the angle when manufacturing the rod-shaped probe, it is not a little when attached to the apparatus, and an angle change occurs. Also in the sample, an angle change occurs depending on the sample stage on which the sample is mounted, the flatness of the sample surface, and the angle of the surface. There are those with a mechanism for adjusting the angle of the sample and those with a mechanism for adjusting the probe side (see Patent Documents 3, 4 and 5). However, just adjusting the angle with respect to the sample surface can measure the sample surface even if the rod-shaped probe is tilted with respect to the Z-direction movement. Will come into contact with the side surface and accurate shape measurement will not be possible.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-111563
[Patent Document 2]
Japanese Patent Laid-Open No. 2001-337025
[Patent Document 3]
Japanese Patent Laid-Open No. 2002-31589 (FIG. 6)
[0010]
[Patent Document 4]
Japanese Patent Laid-Open No. 5-28545 (FIGS. 1 and 13)
[0011]
[Patent Document 5]
JP-A-4-359105 (FIG. 1)
[0012]
[Patent Document 6]
JP-A-10-288618
[0013]
[Non-Patent Document 1]
Journal of Vacuum Science Technology A6 (2) p266 Mar / Apr 1988
[0014]
[Non-Patent Document 2]
Journal of Applied Physics 65 (1), 1 p164 January 1989
[0015]
[Problems to be solved by the invention]
The present invention provides a surface shape measuring apparatus capable of performing appropriate measurement on a measurement object having a large aspect ratio (height / width or height), and in particular, an interatomic device that is a high-resolution surface shape measuring apparatus. The purpose is to provide a probe microscope such as a force microscope or a magnetic force microscope.
[0016]
[Means for Solving the Problems]
The present invention provides an angle correction mechanism on the sample side and the probe side, and angle correction provided on at least one of the sample side and the probe side according to the measurement result of the sample with a known angle and the degree of inclination of the sample to be actually measured. It was decided to measure the shape by correcting the angle between the probe and the sample by the mechanism.
[0017]
(Function)
In the present invention, by taking the above-mentioned means, it is possible to reduce the contact of the rod-shaped probe against the side wall of the measurement object and reach the bottom surface with respect to the measurement object having a large aspect ratio (height / width or height). Since the measurement is performed with correction, it is possible to perform an appropriate measurement within a range in which the length of the probe is allowed even for a sample shape having a large aspect ratio.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a shape measuring apparatus for measuring a sample shape using a probe, provided with an angle correction mechanism on both the sample side and the probe side , the measurement result of a sample with a known angle, and the degree of inclination of the sample actually measured. Therefore, the angle was corrected by the angle correction mechanism and the shape was measured. Note that a tilt stage corresponding to two directions of X and Y may be used as the tilt correction mechanism of the sample. The angle correction mechanism may be a mechanism using a piezoelectric element that deforms when voltage is applied, a mechanism that uses a material that deforms when heat is applied, a mechanism that uses a material that deforms when magnetized, mechanism deformed by application of magnetic force, or may be using any of the mechanisms caused the deformation by the gas applied. It is even better if the surface shape measuring device is a probe microscope that observes the shape and physical state of the sample surface having high sensitivity and high resolution.
In addition, the angle correction mechanism provided on the probe side uses a self-detecting cantilever that detects, as an electrical signal, the amount of strain deformed by the force received from the shape and physical state of the sample surface as a probe. A configuration in which a mechanism capable of correcting the angle of the cantilever portion by applying a voltage may be added.
A sample in which a silicon substrate is manufactured by anisotropic etching may be used as a sample having a known angle.
The procedure for correcting the angle is as follows. A sample with a known angle is placed at a predetermined position on a sample stage on which the sample to be measured is mounted. The sample stage is mounted via a two-direction angle correction mechanism configured on a mechanism (electrical or manual stage) that can move in the plane. In this embodiment, a commercially available sample having a known angle can be installed at the end of the sample stage. (Angle 54.7 ° ± °) Hereinafter, the correction procedure of the present invention will be described with reference to FIG.
[0019]
In FIG. 1, a cantilever 4 is fixed to the tip of a fine movement mechanism 1 made of a piezoelectric element that finely positions a probe in three dimensions through a probe inclination correction mechanism 2 that changes the inclination of the probe and a cantilever fixing base 3. The correction mechanism unit 2 can correct the inclination in the X and Y directions. The cantilever is fixed by bonding (not shown), mechanical fixing to a screw, fixing using a magnet, vacuum suction, or the like. The other end of the fine movement mechanism is fixed to the housing. A rod-like probe 5 is formed at the tip of the cantilever 4. Then, the sample 6 is arranged at a position facing the rod-shaped probe 5. Since a simple structure can be obtained, a self-detecting cantilever in which a rod-like probe 5 is formed is used in this embodiment. When the optical lever mechanism is used, a small optical lever mechanism is formed at the tip of the fine movement mechanism, and a probe tilt correction mechanism section is configured between the fine movement mechanism and the small optical lever mechanism. Further, when the laser light source of the optical lever mechanism and the photo detector part for detecting reflected light are separated, the position of the photo detector part or the reflection mirror is corrected by the tilt of the probe.
[0020]
First, the inclination of the probe is corrected with respect to the Z direction that the probe follows.
1. The flat part of the upper surface where the angle shape of the sample 6 having a known angle is not present is measured. (FIG. 1a) The inclination of the angle correction sample is corrected by the angle correction mechanism on the sample stage side so that the flat portion on the upper surface having no angle shape can be measured horizontally. (Fig. 1b)
3. The known angle shape portion 7 is measured. (Fig. 1c)
4). The probe side angle correction mechanism 2 corrects the probe side angle so that the angle can be measured appropriately. (Fig. 1d)
With the above operation, the tilt of the probe is corrected with respect to the Z direction that the probe follows.
Next, the tilt correction of the sample to be measured is performed.
5. Measure the flat part of the upper surface without the shape of the object to be measured. (Fig. 1e)
6). The inclination of the sample 8 to be measured is corrected by the angle correction mechanism on the sample stage side so that the flat portion of the upper surface having no shape can be measured horizontally, and then the groove shape 9 to be measured is measured. (Fig. 1f)
Through the above operation, the inclination of the sample and the probe can be corrected, and the probe appropriately follows the sample shape with respect to the sample shape to be measured.
[0021]
Next, the apparatus configuration of the present embodiment will be described. In this embodiment, the probe side is configured to scan in three dimensions in the X, Y, and Z directions with respect to the sample. Of course, in the present invention, X, Y, Z three-dimensional scanning may be performed on the sample side, or a combination of scanning in the X, Y, or Z direction on the sample side and Z, X, Y scanning on the probe side is possible. That is easy to say. Most of the samples to be observed in the semiconductor field have a wafer shape, and most of them have a large diameter of 100, 200, or 300 mm. From this point, it is conceivable to scan the sample side with a moving means such as an X, Y stage to measure the sample over a wide range, but for measuring a fine shape, the probe side is scanned in three dimensions X, Y, Z. The type is considered valid.
[0022]
The sample stage on which the sample is mounted is configured via an X, Y, Z stage, and a sample side angle correction stage. The X and Y stages are used for moving the sample to the observation target position on the sample with respect to the probe. The Z stage is used to bring the probe close to the measurable position with respect to the sample surface. In the atomic force microscope, this means that the probe is brought close to the force area. Further, in terms of the device configuration, the Z stage may be configured on the fine movement mechanism side that scans the probe. A probe is formed at a position facing the sample, and the probe is fixed to a fine movement mechanism that scans the probe in three dimensions with respect to the sample surface via a probe fixing mechanism and a probe angle correction mechanism. In the present embodiment, a hollow cylindrical fine movement mechanism using a piezoelectric element material that deforms when a voltage is applied is used. Further, although the fine movement mechanism has a hollow cylindrical shape, a triaxial independent fine movement mechanism is effective in consideration of an arc error at the probe tip. However, in the case of fine part measurement, the scanning area is small and the arc error can be ignored. In this embodiment, a hollow cylindrical shape whose rigidity is relatively increased when the arc error is small is used. In order to improve the dimensional accuracy, it is effective to monitor the displacement by combining the fine movement mechanism with other displacement detection means (capacitance type displacement sensor, etc.) or perform feedback control (closed loop control). It is well known that there is. On the other hand, the fine movement mechanism is mechanically fixed to the main body arm with a fixing screw via the housing. The structure of the present embodiment includes a sample positioning mechanism (X, Y stage), an optical microscope for specifying the position of the sample, a focus adjustment of the optical microscope, and a mechanism for positioning the sample at a position where the probe can be measured (Z stage). ) Is configured on the X and Y stages. A fine movement mechanism that scans the optical microscope and the probe in three dimensions (X, Y, Z) is disposed at a position facing the sample via an arm. And the said member is comprised on the anti-vibration mechanism for preventing the vibration from a floor via a plate. The probe microscope apparatus described in, for example, Japanese Patent Laid-Open No. 10-288618 (Patent Document 6) has a structure that is entirely covered with a soundproof cover for preventing external acoustic noise from entering. The mechanism that is characteristic of was added.
[0023]
In addition, in order to manage the angle when the probe is manufactured, the probe angle correction mechanism is a mechanism using a piezoelectric element in consideration of the fact that a large angle difference does not occur when the probe is attached and a rigid surface. The displacement of the piezoelectric element may change due to a creep phenomenon when a voltage is applied. In order to strictly manage the displacement, it is necessary to control the capacity. Moreover, it is necessary to perform control (closed loop control) in combination with a displacement sensor. In this embodiment, the piezoelectric element is a laminated one. As the probe angle adjustment mechanism, if the device configuration can be driven to reduce the adjustment amount, a piezoelectric element having a small amount of displacement but less creep and a good linearity can be used. When the amount of displacement is required, it can be achieved by combining a magnifying mechanism with the piezoelectric element, but care must be taken not to cause a decrease in rigidity.
[0024]
【The invention's effect】
In the present invention, the tip of the probe reaches the bottom surface of the measurement object with respect to the measurement object having a large aspect ratio (height / width or height) by correcting the sample inclination and the probe inclination, and the depth and height are mainly used. It is possible to provide an effective surface shape measuring device that enables shape measurement to be performed, which makes it possible to relatively easily measure the shape of semiconductor device structures that are becoming more miniaturized without cutting the cross section and observing with a microscope. There is an effect that becomes possible. In addition, using the result, it is possible to obtain an effect that the processing condition of the semiconductor or the like and the evaluation of the finish can be accurately evaluated.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of the present invention.
FIG. 2 is a diagram showing a typical cantilever.
FIG. 3 shows a typical cantilever probe.
FIG. 4 is a diagram showing shape measurement by a typical probe.
FIG. 5 shows a typical cantilever bar probe.
FIG. 6 is a view showing a state in which the tip of a rod-shaped probe is in contact with a side wall of a shape measurement target.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Fine moving element 2 ... Probe inclination correction mechanism part 3 ... Cantilever fixed base 4, 10 ... Cantilever 5 ... Rod-shaped probe 6 ... Sample with known angle 7 ... Known angle shape 8 ... Samples 9, 12, 13 ... Groove and hole shape 11 ... Probe

Claims (3)

In a surface shape measuring apparatus for measuring the shape of a measurement target sample having a measurement target portion having a large aspect ratio,
A rod-shaped probe provided at the tip of the cantilever;
A first angle correction mechanism for adjusting the horizontal position of the sample provided on the sample side;
A second angle correction mechanism for adjusting an angle with respect to the Z axis of the rod-shaped probe provided on the probe side ;
A reference sample having a planar portion and a known angle shape portion;
With
The first angle correction mechanism corrects the horizontal position of the reference sample based on the measurement result of the flat portion of the reference sample,
Correcting the angle of the rod-shaped probe with respect to the Z- axis based on the measurement result of the known angle shape portion of the reference sample whose horizontal position is corrected by the second angle correction mechanism ;
The surface shape measurement apparatus, wherein the first angle correction mechanism corrects the horizontal position of the measurement target sample again based on the measurement result of the flat portion of the measurement target sample . A detection mechanism for detecting a physical quantity of an atomic force or the like received from the sample,
A coarse movement mechanism for performing rough positioning by relatively moving the sample and the detection mechanism three-dimensionally and a fine movement mechanism for performing fine positioning, and observing the shape or physical state of the sample surface. Item 2. The surface shape measuring apparatus according to Item 1.   The surface shape measuring apparatus according to claim 1, wherein the probe has a cylindrical or polygonal bar shape.

Images