JP2009229161A - Method and device for evaluating adhesion of pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for evaluating adhesion of a pattern for quantitatively measuring the adhesion without generating a shear in the fine pattern, in evaluating the adhesion between the fine pattern, such as a resist pattern and a light shielding film pattern of a photomask used for producing semiconductors, and a base substrate. <P>SOLUTION: In the method of evaluating adhesion of the pattern by measuring the adhesion of the pattern formed on the surface of a substrate by scanning while keeping a probe disposed on a cantilever of an atomic force microscope away from the surface of the substrate, the probe is configured with a base for installing the probe to the cantilever and a tip for contacting the pattern, and the base and the tip form a neck, wherein the base makes a continuous sloping face in the vertical direction from the cantilever toward the neck, and the tip has a shape in which the maximum width of the side contacting the side face of the pattern is the same width as the width of the neck or larger. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides adhesion between a fine pattern having a width of several tens of nanometers to several hundreds of nanometers such as a fine resist pattern used for manufacturing a semiconductor or a photomask and a light-shielding film pattern of the photomask, and a substrate provided with those patterns. The present invention relates to a method for quantitatively measuring pattern adhesion, and an evaluation apparatus for measuring pattern adhesion.

  In order to realize high integration and ultraminiaturization of semiconductor elements that progress from a half pitch of 65 nm to 45 nm, in photolithography, as a high resolution technique in an exposure apparatus, a high NA with a high numerical aperture of a projection lens is used. The development of photolithographic technology, immersion exposure technology that exposes a medium with a high refractive index between the projection lens and the object to be exposed, exposure technology with modified illumination, etc. are rapidly progressing. For masks, increasingly fine patterns of resist and thin films are required. In order to obtain high-quality semiconductors and photomasks, the adhesion of these fine patterns to the substrate on which the pattern is formed is important, and a quantitative and direct method for evaluating the adhesion of fine patterns is required. ing.

  Conventionally, as a method for evaluating the adhesion of a resist pattern or a thin film pattern provided on a semiconductor substrate or photomask substrate to a substrate, a cross-cut method or a scratch method is generally known.

  The cross-cut method is shown in Japanese Industrial Standard K5600-5-6, scratching the surface of the thin film sample in a grid pattern, applying an adhesive tape thereon, then peeling the adhesive tape, This is a method of counting the number of peeled cells and the remaining state of peeling and evaluating the number. This method is simple and easy, and is a representative method for evaluating adhesion. However, although the cross-cut method can be qualitatively evaluated, it is not suitable for quantitative evaluation and is not suitable for evaluating the adhesion of a fine pattern of micrometer or less.

  The scratch method has long been known as a method for evaluating the adhesion of a thin film such as an insulating film, and the surface of the thin film is scratched using an indenter, and the indentation load at the time when peeling occurs is used as the adhesion strength. It measures the vertical load (critical load) and horizontal force (horizontal load) at the time of interface fracture or deformation of a thin film sample, and quantifies the strength of adhesion at the interface.

In recent years, for the purpose of measuring a finer pattern, an atomic force microscope (hereinafter referred to as AFM) having a probe provided at one end of a cantilever called a cantilever is used as a probe. A fine pattern adhesion measuring method called a nano scratch method in which a certain weight is applied and a sample surface is scanned with a probe has been proposed (see, for example, Patent Document 1). Alternatively, the AFM probe probe is moved away from the substrate surface and scanned in a non-contact manner, the side surface of the resist line pattern on the substrate is brought into contact with the probe, and the resist is applied by the horizontal force (horizontal load) of the probe. An adhesion force measurement method called DPAT (Direct Peeling Method with Atomic Force Microscope Tip) method for peeling and examining adhesion has been proposed (see Non-Patent Document 1). FIG. 6 is a schematic side view of a conventional probe 61 used for measuring the adhesion force described in Non-Patent Document 1, and the radius of curvature of the tip of the conical probe is about 8 nm.
JP 2006-294904 A A. Kawai, et al. , Microelectronic Engineering, 83 (2006) 659-662.

  However, in the nano-scratch method as described in the above-mentioned Patent Document 1, there is often a large deviation between information obtained by measurement and defective product information that is considered to be caused by peeling of the thin film. In some cases, sufficiently satisfactory measurement information could not be obtained. In addition, the DPAT method described in Non-Patent Document 1 is such that when the side surface of the fine pattern on the surface of the substrate to be measured is in contact with the probe and pressure is applied to the pattern, the pattern is peeled off from the substrate. Before peeling and falling, the resist itself was sheared by the probe, and there was a problem that accurate adhesion data could not be obtained.

  Therefore, the present invention has been made in view of the above problems. That is, the object of the present invention is to cause shearing or the like in the fine pattern in the evaluation of adhesion between a fine pattern such as a resist pattern used in semiconductor manufacturing and a light-shielding film pattern of a photomask and the underlying substrate on which the pattern is formed. It is providing the pattern adhesiveness evaluation method which measures adhesiveness quantitatively, and the evaluation apparatus which measures the adhesiveness of a pattern.

  In order to solve the above-described problem, a pattern adhesion evaluation method according to the invention of claim 1 is a method in which a probe provided on a cantilever of an atomic force microscope is moved away from the substrate surface and scanned in a non-contact manner. In the method for evaluating adhesion of a pattern, the side surface of the pattern formed on the surface is brought into contact with the probe, and the pattern is peeled from the substrate by the horizontal force of the probe to measure the adhesion. And a base part for attaching the probe to the cantilever and a tip part contacting the pattern, the base part and the tip part form a neck part, and the base part is perpendicular to the neck part from the cantilever The tip portion has a shape in which the maximum width on the side in contact with the side surface of the pattern is equal to or larger than the width of the neck portion.

  The pattern adhesion evaluation method according to the invention of claim 2 is the pattern adhesion evaluation method according to claim 1, wherein the tip of the probe has a rectangular parallelepiped shape, a cubic shape, a spherical shape, a cylindrical shape, It is characterized in that it is any one of a prismatic shape, a truncated cone shape having a large bottom surface facing the substrate, a polygonal truncated cone shape, and a flare shape.

  A pattern adhesion evaluation method according to a third aspect of the present invention is the pattern adhesion evaluation method according to the first or second aspect, wherein the probe is made of silicon, silicon nitride, silicon carbide, polysilicon or carbon. It is characterized by being made of any one material selected from the group consisting of nanotubes, sapphire and diamond.

  The pattern adhesion evaluation method according to the invention of claim 4 is the pattern adhesion evaluation method according to any one of claims 1 to 3, wherein the pattern is a resist line pattern or a dot pattern. It is characterized by this.

  The apparatus for evaluating adhesion of a pattern according to the invention of claim 5 scans the probe provided on the cantilever of the atomic force microscope away from the substrate surface in a non-contact manner, and the side surface of the pattern formed on the substrate surface The pattern adhesiveness evaluation apparatus according to any one of claims 1 to 4, wherein the probe is brought into contact with each other, and the pattern is peeled off from the substrate by a horizontal force of the probe to measure the adhesiveness. The probe described in the pattern adhesion evaluation method is used.

  The present invention expands the tip shape of the probe tip and increases the contact area with the pattern to be measured, so that when the probe pressure is applied to the side of the pattern, damage to the pattern itself is reduced and shearing is reduced. In this evaluation method, the pattern is peeled off or peeled off from the substrate without causing a collapse, and the adhesion of the pattern is quantified and measured. According to the pattern adhesion evaluation method of the present invention, it becomes possible to quantitatively measure the adhesion / peeling characteristics to a substrate such as a resist pattern, and improve process conditions such as pattern formation and cleaning before pattern formation. It becomes easy to optimize the conditions, and the quality can be improved and the yield rate can be improved.

  Moreover, according to the fine pattern adhesion evaluation apparatus of the present invention, an evaluation apparatus capable of easily measuring the fine pattern adhesion by a simple method is obtained.

  Hereinafter, a fine pattern adhesion evaluation method and a fine pattern adhesion evaluation apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic side view of a side in contact with a probe pattern used in the pattern adhesion evaluation method of the present invention, and illustrates six types of probes 11a, 11b, 11c, 11d, 11e, and 11f. . The scanning direction of the probe is a direction perpendicular to the paper surface. In the schematic side view of FIG. 1, each probe is composed of a base portion 12a, 12b, 12c, 12d, 12e, and 12f and a tip portion 13a, 13b, 13c, 13d, 13e, and 13f that comes into contact with a sample that is an object to be measured. Has been. The base and the tip form necks 14a, 14b, 14c, 14d, 14e and 14f.

  The wide upper end side (upper side in the drawing) of the base of each probe shown in FIG. 1 is the side attached to the cantilever. The base of the probe used in the present invention forms an inclined surface that is continuous in the vertical direction from the cantilever to the neck. The tip portions 13a, 13b, 13c, 13d, 13e, and 13f of each probe have a shape that is widened so that a contact area with a pattern to be measured (not shown) is increased, and the side surface of the pattern The maximum width of the side in contact with the neck is the same as or larger than the width of the neck. In the example shown in FIG. 1, the probe shown in FIGS. 1 (d) and (e) shows a case where the maximum width of the tip is the same as the width of the neck, and FIGS. 1 (a), 1 (b) and 1 (c). , (F) shows the case where the maximum width of the tip is larger than the width of the neck.

  The shape of the base of the probe used in the present invention is a conical shape, a pyramid shape, or the like, which is the same shape as that of a conventional AFM probe, up to the neck portion. In the present invention, the boundary between the base portion and the tip portion of the probe is referred to as a neck portion, and the shape of the probe in the longitudinal direction changes with the neck portion as a boundary. The maximum width on the side in contact with the side surface is the same as or larger than the width of the neck.

  As shown in FIG. 1, the tip of the probe used in the present invention has a rectangular parallelepiped shape (13b), a cubic shape, a spherical shape (13c), a cylindrical shape (13d), a prismatic shape (13e), and the substrate. Any one of a truncated cone shape (13a), a polygonal truncated cone shape, and a flare shape (13f) having a large bottom surface on the facing side is used. When the shape of the tip is a truncated cone shape, a polygonal truncated cone shape, or a flare shape, as shown in FIGS. 1 (a) and 1 (f), a wider substrate having a larger bottom surface on the side facing the substrate is used. This is more preferable because it increases the possibility of increasing the contact area with the side surface. In the case of a sphere, the sphere of the present invention also includes a substantially spherical shape in which the cross section of the neck that serves as a contact point with the base is a flat surface. In any of the above shapes, in order to increase the contact area between the tip of the probe and the pattern, the size of the tip of the probe can be selected arbitrarily.

  The probe used in the present invention is made of silicon, silicon nitride, silicon carbide, polysilicon, carbon nanotubes, sapphire, diamond, or the like at the base and tip of the probe. The length of the probe base is about 3 μm to 30 μm, and the length of the tip of the probe is about 10 μm to 20 μm. Since the neck of the probe is the name of the boundary between the base and tip of the probe, no particular length is required. For example, when the shape of the probe base is conical, the radius of the cross section of the neck is about 30 nm to 500 nm.

  The base and tip of the probe used in the present invention are manufactured by processing each separately, and then integrated through the neck by bonding, or by processing one material, the base and neck A probe having a tip can be obtained.

  FIG. 2 shows a measurement principle diagram (FIG. 2 (a)) as an example of an AFM type fine pattern adhesion evaluation apparatus used in the fine pattern adhesion evaluation method of the present invention, and the vicinity of the measurement probe. A schematic diagram (FIG. 2B) is shown. As shown in FIG. 2A, when a small probe 21 having a cantilever structure is gradually brought closer to the sample substrate 22, an attractive force or a repulsive force acts between them at a certain distance, and the probe 21 is provided. The cantilever 23 is distorted. The distortion is detected by the optical sensor 25 due to the change in the reflection angle of the laser beam 24 applied to the back surface of the cantilever 23 so that the distortion amount of the cantilever 23 becomes constant when the probe 21 is scanned on the surface of the sample substrate 22. The distance between the probe 21 and the sample substrate 22 is controlled. The scanning of the surface of the sample substrate 22 (X direction, Y direction) and the control of the distance between the probe 21 and the sample substrate 22 (Z direction) are performed by the piezo scanner 26, and the voltage applied to each scanner is analyzed. Thus, an image of the surface of the sample substrate 22 is obtained. When the probe is moved to a predetermined position of the pattern to be measured, the adhesion is measured.

  FIG. 3 is a schematic diagram for explaining a method for evaluating the adhesion of a pattern using the above-described fine pattern adhesion evaluation apparatus. In FIG. 3, parts other than the probe and the substrate provided with the pattern are omitted. As shown in FIG. 3 (a), the probe 31 used for the measurement has a sloped surface in the vertical direction toward the substrate 34, which is the sample to be measured, in the same manner as the probe shown in FIG. 1 (b). The tip 31 of the probe 31 has a neck near the tip 33, and the tip 33 of the probe 31 has a rectangular parallelepiped shape. The probe 31 is arranged so that one plane having the maximum area of the rectangular parallelepiped tip portion 33 is parallel to the side surface of the pattern 32. Next, the probe 31 is moved in the horizontal direction (arrow in FIG. 3A) and brought into contact with the side surface of the pattern 32 to apply a horizontal force (horizontal load). At this time, the tip of the probe 31 is separated from the surface of the substrate 34 on which the pattern 32 is formed. If the tip of the probe 31 is in contact with the surface of the substrate 34, the influence of the force in the vertical direction in addition to the force in the horizontal direction must be taken into account, and the analysis of the adhesion measurement data is more complicated. Because it becomes.

When the force applied to the pattern 32 from the probe 31 exceeds a certain limit, the pattern 32 peels off from the substrate 34 or peels and falls down, whereby the adhesion force of the pattern 32 can be measured. According to the pattern adhesion evaluation method of the present invention, the pattern 32 can be peeled off from the substrate without shearing, and highly reliable adhesion data can be obtained.
Hereinafter, the present invention will be described in more detail with reference to examples.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

<Measurement sample>
A chromium oxide / chromium nitride two-layer sputtered film was formed on a quartz substrate to form a chromium blank, and a negative electron beam resist NEB-22 (manufactured by Sumitomo Chemical Co., Ltd.) was applied thereon with a film thickness of 400 nm. The blanks provided with this resist film were subjected to electron beam drawing and developed to form a large number of square dot resist patterns having sides of 200 nm to 500 nm.

<Evaluation of peeling properties>
L-trace (manufactured by SII NanoTechnology Co., Ltd.) was used as an AFM apparatus for evaluating peeling properties. As the probe provided on the cantilever of this AFM apparatus, a probe having a cylindrical and flared probe tip shape shown in FIGS. 1 (d) and 1 (f) was used. The cylindrical probe has a base length of 20 μm, a neck radius of 200 nm, a cylindrical tip radius of 200 nm, and a length of 15 μm. The flared probe has a base length of 20 μm, a neck radius of 200 nm, a flared tip with a maximum width of 300 nm, an overhang of 20 nm, and a length of 15 μm. Both the cylindrical probe and the flare probe are manufactured by integrating silicon as a material.

  For comparison, a conventional probe having a conical probe tip shape (trade name: SI-DF40P (Seiko Instruments)) shown in FIG. 6 was used. The conventional probe has a length of 14 μm, a cone angle of about 30 °, and a tip curvature radius of 8 nm. A conventional conical probe is also made of silicon.

  Next, using a cantilever equipped with each of the above-mentioned probes, first, an enlarged image of the resist pattern was observed by AFM, and a resist pattern shape image for adhesion evaluation was obtained.

Subsequently, the tip of the probe is moved to a position 1 μm away from the edge of the resist pattern, and the probe is separated from the quartz substrate surface and scanned in a non-contact manner under the following conditions. The side of the probe is brought into contact with the tip of the probe, and the resist pattern is peeled and collapsed with the horizontal force of the probe, and the frictional curve at that time is measured to determine the force when the pattern collapses. The value was defined as adhesion. The force (adhesion force) required to collapse the resist pattern when using the flare probe shown in FIG. 1 (f) was 100 to 5000 nN.
Scanning distance: 2μm
Scanning speed: 400nm / sec
Scanning angle (with respect to the side of the pattern): 90 degrees Distance between the probe tip and the sample surface: 30 nm

  Next, AFM observation was performed to obtain a resist pattern shape image. FIG. 4 is an enlarged plan view of a resist pattern on a chrome blank photographed by the above AFM apparatus using the probe having the flare-shaped probe shape shown in FIG. It is. FIG. 4A shows a state of a pattern (indicated by an arrow) before the probe is scanned in the upward direction on the paper surface, and FIG. 4B shows a collapsed pattern from the original position after the pattern is scanned. A slight deviation is observed.

  Similarly, the resist pattern can be collapsed even with the cylindrical probe shown in FIG. 1D, and the force (adhesion force) required for collapsing the resist pattern at that time is the same as in the case of the flare probe described above. Almost the same, 100 to 5000 nN.

  On the other hand, FIG. 5 shows a shape image of a resist pattern when the conventional probe shown in FIG. 6 having a sharp tip shape is used. FIG. 5A shows a state of a pattern (indicated by an arrow) before the probe is scanned in the upward direction on the paper surface, and FIG. 4B shows a state after the pattern is scanned. When a conventional probe is used, as shown in FIG. 4B, the resist pattern is cut by scanning the probe, and the resist pattern cannot be collapsed. Could not get.

It is a side surface schematic diagram of the probe used for the adhesiveness evaluation method of the pattern of this invention. FIG. 3 is a diagram illustrating a measurement principle as an example of an AFM type pattern adhesion evaluation apparatus used in the pattern adhesion evaluation method of the present invention, and a schematic view around a measurement probe. It is a schematic diagram explaining the method of evaluating the adhesiveness of a pattern using the adhesiveness evaluation apparatus of the pattern of this invention. It is the plane enlarged photograph by AFM when the resist pattern on a chrome blank is scanned with the probe used for the adhesiveness evaluation method of this invention shown in FIG.1 (f). It is the plane enlarged photograph by AFM when the resist pattern on chrome blanks is scanned with the conventional probe shown in FIG. It is a side surface schematic diagram of the probe used for the conventional adhesion force measurement.

Explanation of symbols

11a, 11b, 11c, 11d, 11e, 11f Probes 12a, 12b, 12c, 12d, 12e, 12f Probe bases 13a, 13b, 13c, 13d, 13e, 13f Probe tips 14a, 14b, 14c, 14d, 14e, 14f Probe neck 21 Probe 22 Sample substrate (measurement object)
23 Cantilever 24 Laser beam 25 Optical sensor 26 Piezo scanner 27a X and Y axis scanning system 27b Z axis servo system 28 Computer 29 Preamplifier 30 Monitor 31 Probe 32 Pattern (object to be measured)
33 Probe tip 34 Substrate 61 Conventional probe

Claims (5)

The probe provided on the cantilever of the atomic force microscope is scanned away from the substrate surface in a non-contact manner, the side surface of the pattern formed on the substrate surface is brought into contact with the probe, and the horizontal direction of the probe is adjusted. In the pattern adhesion evaluation method of measuring adhesion by peeling the pattern from the substrate with force,
The probe is composed of a base for attaching the probe to the cantilever and a tip that contacts the pattern, and the base and the tip form a neck,
The base portion has a continuous inclined surface in a vertical direction from the cantilever toward the neck portion,
The tip end portion has a shape in which the maximum width on the side contacting the side surface of the pattern is the same as or larger than the width of the neck portion.   The shape of the tip of the probe is any one of a rectangular parallelepiped shape, a cubic shape, a spherical shape, a cylindrical shape, a prism shape, and a truncated cone shape, a polygonal truncated cone shape, and a flare shape having a large bottom surface on the side facing the substrate. The pattern adhesiveness evaluation method according to claim 1, wherein the pattern has a seed shape.   2. The probe according to claim 1, wherein the probe is made of any one material selected from the group consisting of silicon, silicon nitride, silicon carbide, polysilicon, carbon nanotube, sapphire, and diamond. 2. The method for evaluating adhesiveness of the pattern according to 2.   The pattern adhesiveness evaluation method according to claim 1, wherein the pattern is a resist line pattern or a dot pattern. The probe provided on the cantilever of the atomic force microscope is scanned away from the substrate surface in a non-contact manner, the side surface of the pattern formed on the substrate surface is brought into contact with the probe, and the probe in the horizontal direction In a pattern adhesion evaluation device that measures the adhesion by peeling the pattern from the substrate with force,
A pattern adhesion evaluation apparatus using the probe according to the pattern adhesion evaluation method according to claim 1.