JP4724604B2 - Sample measuring device - Google Patents

Description

  The present invention relates to a sample measuring apparatus for measuring light generated by irradiating a sample with energy rays.

  This type of sample measurement device (optical measurement device) performs physical property evaluation or analysis of a semiconductor element in a minute region of a sample using light (cathode luminescence) generated from the sample by irradiating the sample with an electron beam. is there.

  In this sample measuring apparatus, as shown in Patent Document 1, in order to collect cathodoluminescence, a condensing mirror portion is disposed so as to cover the sample, and an optical fiber or spectroscope incident outside the electron microscope is incident. The focus is formed on the slit.

However, since the condensing mirror part that is separate from the lens barrel part is provided between the lens barrel part (lens barrel body) of the electron microscope and the sample, the objective lens in the lens barrel part is naturally a condensing mirror. The distance from the sample-side tip of the objective lens to the sample (hereinafter simply referred to as the working distance (WD)) increases, and the spatial resolution of the sample measuring device deteriorates. is there.
JP 2003-157789 A

Therefore, the main point of the present invention is that the irradiation position of the energy beam can be easily adjusted within the focal point of the condensing mirror unit and that the position of the condensing mirror unit is prevented from being displaced due to vibration or the like, although the configuration is simple. This is an issue to be solved.

That is, the sample measurement device according to the present invention is a sample measurement device that measures light generated by irradiating a sample with an energy beam, the energy beam generator that generates the energy beam, and the energy beam generator generated by the energy beam generator . An energy beam control means for converging the energy beam, and the energy beam control means causes the energy beam to converge so that the axis thereof coincides with the axis of the energy beam control means; and the lens barrel unit And an energy beam path for passing the energy beam converged by the lens barrel portion and irradiating the sample with the energy beam, and a focal point on the axis of the channel. A mirror surface, and a light collecting mirror portion that collects light generated from the sample by the mirror surface, and the lens barrel portion and the light collecting mirror portion are detachable, The axis of the energy beam control means and the axis of the energy beam passage are positioned coaxially, and the focusing mirror is supported by the lens barrel so that the axis of the energy beam and the focal point coincide with each other. A positioning structure, wherein the positioning mechanism includes a convex portion formed at a lower end of the lens barrel portion, and a concave portion formed on the upper surface of the condenser mirror portion and formed substantially the same as the outer peripheral surface of the convex portion. It is characterized by comprising . Here, the light generated from the sample includes luminescence such as cathodoluminescence, photoluminescence, or electroluminescence.

If it is such, although it is a simple structure, it can adjust the irradiation position of an energy beam easily in the focus of a condensing mirror part, and can prevent position shift of a condensing mirror part by vibration etc. .

  Specifically, a lens barrel portion having the objective lens and the mirror surface is provided, and the lens barrel portion includes a lens barrel body and a condensing mirror portion supported by the lens barrel body. A cylinder main body includes the objective lens, and the condenser mirror unit passes an energy ray converged by the objective lens and irradiates the sample with the energy ray, and an axis of the passage The objective lens includes: the mirror surface having a focal point set on a line; and a concave portion into which the sample side end portion of the barrel main body is fitted, and the sample side end portion of the barrel main body is fitted into the concave portion. It is desirable that at least a part of is provided on the sample side with respect to the energy ray incident side end of the mirror surface. Here, “the lens barrel body has an objective lens” means that when the working distance is the distance from the sample-side tip of the objective lens to the sample, the lens barrel body has all of the objective lens. In other words, when the working distance is the distance from the portion other than the sample-side tip of the objective lens to the sample, it indicates that the lens barrel body includes at least a part of the objective lens including the portion.

  As another specific embodiment for providing at least a part of the objective lens closer to the sample side than the energy ray incident side end of the mirror surface, the objective lens and a mirror having the mirror surface are provided. At least one electrode that includes the barrel, the barrel having a barrel body and a collector mirror supported by the barrel body, and constituting the objective lens in the collector mirror Is considered to be formed.

  At this time, the condensing mirror unit has an energy beam path for passing the energy beam generated from the energy beam generating unit and irradiating the sample with the energy beam, and the inner wall of the energy beam channel has the energy beam channel. It is desirable that at least one electrode constituting the objective lens is formed.

  In order to significantly reduce the working distance, it is preferable that the condensing mirror unit is an electrode constituting the objective lens.

  As a specific configuration for facilitating the production of the condensing mirror part, it is desirable that the condensing mirror part is formed of aluminum and function as a grounded electrode of the objective lens. If this is the case, the working mirror (WD) can be greatly reduced because the condensing mirror portion also serves as an electrode constituting the objective lens.

  The sample measuring apparatus according to the present invention is a sample measuring apparatus that measures light generated by irradiating a sample with energy rays, and is an objective that converges the energy rays from the energy ray generating unit and irradiates the sample. A lens barrel having a lens and a mirror surface for condensing light generated from the sample, and the sample-side tip of the lens barrel is an electrode constituting an objective lens and light generated from the sample irradiated with energy rays And a mirror surface for condensing light.

  As a specific embodiment for reducing the working distance, the lens barrel portion includes a lens barrel main body and a light collecting mirror portion supported by the lens barrel main body. It is desirable that at least one electrode constituting the objective lens is formed.

  As a specific form of forming the objective lens, the condensing mirror unit has an energy beam path for passing the energy beam generated from the energy beam generating unit and irradiating the sample with the energy beam. It is conceivable that at least one electrode constituting the objective lens is formed on the inner wall of the energy beam passage.

  As described above, according to the present invention, since the working distance (WD) can be made as small as possible, it is possible to suppress the degradation of the spatial resolution of the sample measuring apparatus and perform highly accurate measurement. It becomes like this.

  An embodiment of the present invention will be described below with reference to the drawings.

  The sample measuring apparatus according to the present embodiment uses the light L (cathode luminescence) generated from the sample W by irradiating the electron beam EB, which is an energy beam, to the physical property evaluation or semiconductor element in the micro region of the sample W. As shown in FIG. 1, the sample stage 1 and the sample W placed on the sample stage 1 are irradiated with an electron beam EB, which is an energy beam, as shown in FIG. The electron beam irradiation device 2, the detection device 3 that is a light detection unit that splits and detects the luminescence L generated from the sample W by irradiation with the electron beam EB, and an output signal from the detection device 3 are received. And an information processing device 4 that performs a predetermined calculation process to evaluate (for example, stress measurement).

  First, the sample stage 1, the detection device 3, and the information processing device 4 will be described.

  The sample stage 1 is movable in the X-axis, Y-axis, and Z-axis directions. Further, in this embodiment, the sample stage 1 is illustrated in order to reduce the peak half-value width of the sample spectrum and obtain meaningful information from the spectrum. Further, a cooling means and a temperature control mechanism are provided so that the sample stage 1 and the sample W can be cooled to a predetermined temperature of several tens of K or less.

  The detection device 3 includes a spectroscopic unit 32 and a sensing unit 33. The spectroscopic unit 32 separates the luminescence L collected by the condensing mirror unit 24B, which will be described later, into monochromatic light, and is configured using, for example, a monochromator. The sensing unit 33 measures the intensity of each monochromatic light split into a plurality of wavelengths for each wavelength by the spectroscopic unit 32, and outputs an output signal having a current value (or voltage value) corresponding to the intensity of each monochromatic light. Output. In the present embodiment, the sensing unit 33 is configured using a photomultiplier (PMT), but the device to be used may be changed depending on the wavelength region to be measured. For example, in the infrared (from 1 μm), it is preferable to use a Ge detector, a Pbs detector, an infrared PMT, or the like. Further, a CCD may be used because of its excellent photoelectric conversion efficiency, dynamic range, and S / N. According to the CCD, it is possible to detect the spectrum collectively.

  The information processing apparatus 4 is a general-purpose or dedicated computer including a CPU, a memory, an input / output interface, an AD converter, an input unit, and the like. Then, when the CPU or its peripheral device operates based on a program stored in a predetermined area of the memory, the information processing device 4 receives an output signal from the detection device 3 and scans each measurement. Calculate the stress at the point.

  A specific calculation method is to receive the light intensity signal from the detection device 3, generate spectrum data that is data indicating a spectrum waveform, and smooth the spectrum waveform indicated by the spectrum data. Next, a differential operation is performed on the waveform obtained by smoothing, and the wavelength at the time when the obtained value is inverted from plus to minus is set as the peak wavelength. The peak wavelength may be obtained by fitting with a predetermined function. Then, the stress acting on the sample W is calculated based on the amount of displacement between the peak wavelength obtained from the sample W to be measured and the reference peak wavelength.

  The principle of this stress calculation will be briefly described. The relationship between the stress existing at the site irradiated with the electron beam EB of the measurement sample W and the peak wavelength obtained can be linearly approximated until the magnitude of the stress is about 10 GPa. It is indicated by (1).

ν _σ = ν ₀ + Π · σ (1)

Here, ν _σ is the peak wavelength of the measured spectrum, ν ₀ is the reference peak wavelength, σ is a tensor indicating the stress acting on the measurement sample W, and Π is called a PS (Piezo-Spectroscopic) coefficient. A position-independent tensor that depends only on. Ν ₀ and Π are stored as correlation data in a storage unit in the memory. Such correlation data is statistically obtained by applying a plurality of known stresses to a sample equivalent to the measurement sample W.

  Here, the reference peak wavelength is, for example, when measuring the residual stress of the sample W, from another equivalent sample where no residual stress exists, or from a portion where the residual stress does not exist in the sample W. It identifies from the acquired fluorescence spectrum waveform. On the other hand, for example, when it is desired to measure the internal stress generated due to the external force applied to the sample W, the reference peak wavelength is obtained from the fluorescence spectrum waveform obtained from the sample W in the state where no external force is applied. Identify. Data indicating the reference peak wavelength is stored, for example, in a storage unit set in a predetermined area of the memory.

  Next, the electron beam irradiation apparatus 2 will be described.

  The electron beam irradiation apparatus 2 is, for example, a scanning type, and an electron beam EB together with an electron gun 21 that is an energy beam generating unit and a lens mechanism that converges the electron beam EB emitted from the electron gun 21 to the measurement site of the sample W. An energy beam control means 22 comprising a scanning mechanism for scanning the light, a mirror surface 23 for condensing the light L emitted from the sample W through the electron beam EB, and a lens barrel 24 for holding them. And. In the present embodiment, the electron gun 21 is a thermal field emission type.

  Specifically, as shown in FIGS. 2 and 3, the lens barrel portion 24 includes a lens barrel main body 24A and a condensing mirror portion 24B supported by the lens barrel main body 24A.

  The lens barrel main body 24A is a cylindrical ceramic column having high resistance conductivity, and includes a flange portion 24A1 in which the electron gun 21 is provided, and a cylindrical portion 24A2 extending downward from the flange portion 24A1.

  The cylindrical portion 24A2 includes energy beam control means 22 on its inner wall (inner circumference). Specifically, on the inner wall of the cylindrical portion 24A2, a gun lens 221 for extracting electrons from the electron gun 21, an aperture electrode 222 for monitoring the electron dose, and an astigmatism for correcting astigmatism of the electron beam EB. A corrector (stigmeter) 223 and a deflector (deflector) 224 for polarizing the electron beam EB are formed in this order from the top, and further below the deflector (deflector) 224, an electron beam Two ring-shaped electrodes 2251 and 2252 constituting a part of an objective lens 225 that is an electrostatic lens for converging EB are formed.

  The gun lens 221 is a triode-type electrode, and the aperture electrode 222, the astigmatism corrector (stigmeter) 223, and the deflector (deflector) 224 each include eight electrode pieces arranged along the circumferential direction. Yes. In addition, each electrode and electrode piece is applied with a predetermined voltage by a power source (not shown) provided outside via the wiring 25, or is connected to the ground. The wiring 25 is connected to the electrode and the electrode piece through the inside of the cylindrical portion. Note that the wiring 25 is not shown in FIG.

  The two electrodes 2251 and 2252 constituting the objective lens 225 constitute a triode type electrode together with the condensing mirror portion 24B by attaching a condensing mirror portion 24B described later to the barrel main body 24A. . The two electrodes 2251 and 2252 are thin ring electrodes, and 0 V (ground) is connected to the upper electrode 2251, and an appropriate high voltage (voltage that can generate a necessary lens) is connected to the lower electrode 2252. ) Is applied. The manufacturing method is performed by performing ceramic metallization on the inner wall of the cylindrical portion 24A2, first forming the nickel layer 22a, and then forming the gold layer 22b thereon. The electrodes and electrode pieces constituting the gun lens 221, the aperture electrode 222, the astigmatism corrector (stigmeter) 223, and the deflector (deflector) 224 are also manufactured by the same process.

  The condensing mirror unit 24B is provided between the lens barrel body 24A and the sample W, collects the luminescence L generated from the sample W with a minimum loss, and guides it to the spectroscopic unit 32 described later. It has an energy beam path 24B1 for passing the converged electron beam EB and irradiating the sample W with the electron beam EB, and a mirror surface 23 having a focal point F set on the axis of the path 24B1. . Furthermore, the condensing mirror part 24B has a hole 24B2 for being fixedly supported by the barrel main body 24A by fastening with a plurality of (three in the present embodiment) bolts.

  Moreover, the condensing mirror part 24B is formed from aluminum. This is because if the condensing mirror portion 24B is formed of ceramics, light is scattered by agglomerates generated when the mirror surface 23 is cut. Since this point is formed of aluminum, no agglomeration occurs on the mirror surface 23. Further, the triode-type objective lens 225 is configured together with the two electrodes 2251 and 2252 constituting the objective lens 225 by connecting the condenser mirror portion 24B to the ground. As a result, the lowermost end (sample-side tip) of the objective lens 225 becomes the sample-side outlet of the energy beam passage 24B1. In other words, at least a part of the objective lens 225 (in this embodiment, the electrode on the most sample side among the electrodes constituting the objective lens 225) is connected to the electron beam incident side end portion 231 (the upper end portion of the mirror surface 23) of the mirror surface 23. ) On the sample side.

  The mirror surface 23 may be a parabolic mirror or an ellipsoidal mirror, but an ellipsoidal mirror is used in this embodiment. The ellipsoidal mirror 23 itself has the advantages of receiving and condensing light and can set the focal point F freely by the ellipsoid. On the other hand, the ellipsoidal mirror 23 has a disadvantage that the coupling with the spectroscopic unit 32 is not successful because the imaging magnification is determined by the mechanical arrangement condition. In order to solve this problem and simplify the optical axis adjustment, the luminescence L collected by the ellipsoidal mirror 23 is transferred to the spectroscopic unit 32 using the optical fiber 321. Here, the optical axis adjustment is performed by adjusting the light incident portion 321A of the optical fiber 321 by an adjustment mechanism (not shown) in conjunction with the focal point F of the ellipsoidal mirror 23.

  As shown in FIG. 3 in particular, the energy beam path 24B1 is for irradiating the sample W with the electron beam EB emitted from the lens barrel body 24A, and the electron beam EB passing through the energy beam path 24B1 W is irradiated. The energy beam path 24B1 is formed so that the irradiation position P where the sample W is irradiated with the electron beam EB that has passed passes into the focal point F of the condenser mirror portion 24B.

  Thus, the electron beam measuring apparatus according to the present embodiment supports the condensing mirror unit 24B on the barrel main body 24A so that the axis O and the focal point F of the energy beam EB coincide with each other. In this configuration, the relative position between the barrel main body 24A and the condensing mirror portion 24B is constant. In the present embodiment, the barrel main body 24A and the condensing mirror portion 24B are separable from each other, and therefore the positioning structure 5 is provided to integrally configure the lens barrel main body 24A and the condensing mirror portion 24B. Yes.

  The positioning structure 5 enables the lens barrel main body 24A and the condensing mirror portion 24B to be detachable, while the axis of the energy beam control means 22 and the axis of the energy beam passage 24B1 are positioned coaxially to thereby adjust the energy beam EB. The condensing mirror portion 24B is supported by the barrel main body 24A so that the axis O and the focal point F coincide with each other.

  The positioning structure 5 includes a convex structure provided on one of the lens barrel main body 24A and the condensing mirror portion 24B and a concave structure provided on the other and corresponding to the convex structure. A concave portion 24B4 is formed on the upper surface 24B3 of the mirror portion and into which the lower end portion of the lens barrel main body 24A is fitted. ing. Then, the outer peripheral surface of the lower end portion of the lens barrel main body 24A is fitted and embedded in the recess 24B4, and fastened with a plurality of (three in this embodiment) bolts to be fixedly supported on the lens barrel main body 24A. .

  The inner diameter of the recess 24B4 is substantially the same as the outer diameter of the outer peripheral surface of the lower end portion of the cylindrical portion 24A2 of the barrel main body 24A, and the depth thereof can be set arbitrarily. By specifying a tolerance between the outer diameter of the cylindrical portion 24A2 and the inner diameter of the concave portion 24B4, simply fitting them together and providing the lower end portion of the barrel main body 24A within the concave portion, the axis of the energy beam control means 22 and the aforementioned The axis of the energy beam EB and the focal point F are made to coincide with each other so as to be coaxial with the axis of the energy beam path 24B1.

  According to the electron beam measuring apparatus configured as described above, the working distance (WD) can be made as small as possible even if the electrode to which the high voltage of the objective lens 225 is applied is used as a reference. Deterioration of the spatial resolution of the measuring device can be suppressed, and high-precision measurement can be performed. Further, since the condensing mirror portion 24B is supported by the lens barrel main body 24A, it is not necessary to adjust the position of the condensing mirror portion 24B for each measurement, and the irradiation position of the electron beam EB is simple in structure. It is possible to easily adjust the position of P within the focal point F of the condensing mirror unit 24B and to prevent the positional deviation of the condensing mirror unit 24B due to vibration or the like. Therefore, since the irradiation position P of the electron beam EB is always within the focal point F, all the light L generated by being excited at the irradiation position P can be efficiently collected, and the decrease in the detection signal is suppressed as much as possible. Can do.

  This is particularly effective when the electron beam irradiation apparatus 2 is provided with a low acceleration voltage of 5 kV or less or an ultra-low acceleration voltage of 1 kV or less and is relatively susceptible to disturbance.

  Further, the positioning structure 5 is composed of the recess 24B4 and the lower end portion of the lens barrel main body 24A, and the lower end portion of the lens barrel main body 24A is fitted and embedded in the recess 24B4, so that the integration and positioning are performed. This can be done at the same time, eliminating the need for positioning.

  The present invention is not limited to the above embodiment.

  For example, regarding the provision of at least a part of the objective lens 225 closer to the sample side than the incident side end of the energy beam EB in the mirror surface 23, for example, as shown in FIG. 4, the energy beam path of the condensing mirror unit 24B By providing the objective lens 225 on the inner wall (inner circumference) of 24B1, at least a part of the objective lens 225 may be provided on the sample side with respect to the incident side end of the energy beam EB in the mirror surface 23. At this time, the condensing mirror part is formed of ceramics or the like, the grain boundary is suppressed as much as possible, the mirror surface is formed by evaporating metal or the like, and the metallization process is performed on the inner wall of the energy beam passage 34B1. The electrodes 2251, 2252, 2253 are prepared to provide the electrostatic lens 225.

  In addition, as shown in FIG. 5, a cylindrical convex portion 24A3 having an objective lens 225 formed on the inner wall thereof is provided at the lower end of the cylindrical portion 24A2 of the barrel main body 24A, and the upper surface 24B3 of the condensing mirror portion 24A is provided. By embedding the cylindrical convex portion 24A3 in the provided concave portion 24B4, at least a part of the objective lens 225 may be provided on the sample side with respect to the incident side end portion of the energy beam EB in the mirror surface 23.

  In the above embodiment, the positioning mechanism 5 is composed of the concave portion 24B4 provided on the upper surface 24B3 of the condensing mirror portion 24B and the outer peripheral surface of the lower end portion of the cylindrical portion 24A2 of the barrel main body 24A. In addition, as shown in FIG. 4, a cylindrical convex portion 24B5 formed on the condensing mirror portion upper surface 24B3 and defining the energy ray passage 24B1 on the inner peripheral surface, and an outer peripheral surface of the cylindrical convex portion 24B5 You may make it comprise from the internal peripheral surface of cylindrical part 24A2 of the barrel main body 24A formed substantially the same.

  Furthermore, in the above-described embodiment, the positioning structure is configured by the lower end portion and the concave portion of the cylindrical portion of the barrel main body. However, the positioning structure is not limited to this, and the condensing mirror portion is directly or indirectly supported by the barrel portion. Just do it. As one of the methods, a connecting member may be provided in addition to the lens barrel portion and the condensing mirror portion, and the lens barrel portion and the condensing mirror portion may be connected using this connecting member.

  Furthermore, in the said embodiment, although the ellipsoidal mirror was used as the mirror surface 23, it is not restricted to this, For example, you may use a parabolic mirror. In this case, when the light L from the sample W is reflected due to the characteristics of the parabolic mirror, it becomes parallel light. Therefore, as shown in FIG. 6, in order to collect the parallel light on the light incident portion 321A of the optical fiber 321. A convex lens 314 is provided between the condenser mirror portion 24B and the optical fiber 321.

  In addition, although the condensing mirror part of the said embodiment was shape | molded using aluminum, electromagnetic shielding materials, such as a permalloy, iron, a silicon steel plate, can be used for others. If it is such, the condensing mirror part including the energy beam path can be electromagnetically shielded until just before the sample.

  In addition, the energy line passage provided in the condensing mirror portion of the embodiment may be a differential exhaust aperture. In other words, when measuring biological samples, it is necessary to evacuate the interior of the lens barrel to a high vacuum while evacuating the chamber with the collector mirror and sample stage to a low vacuum. It may be made to function as an aperture for exhausting while maintaining the above.

  In addition, in the case of a composite apparatus that performs cathodoluminescence (CL) measurement and Raman spectroscopy or photoluminescence (PL) measurement, the mirror surface of the condensing mirror portion may be used for laser light irradiation.

  In addition, the measurement by cathode luminescence (CL) is not limited to the stress measurement, and an intensity image or a wavelength distribution image of a single wavelength band is acquired based on light by CL at a specific wavelength or a plurality of wavelengths. It is also possible to perform defect inspection such as crystal growth.

  Regarding the detection device, in the above-described embodiment, the spectroscopic unit and the sensing unit are provided. In addition, only the light in a single wavelength region is detected by the optical filter or the like without performing the spectroscopic unit. It may be derived to a detector.

  In addition, some or all of the above-described embodiments and modified embodiments may be combined as appropriate, and the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. .

1 is a schematic configuration diagram showing a sample measurement device (optical measurement device) according to an embodiment of the present invention. The expanded sectional view which mainly shows the lens-barrel main body and condensing mirror part in the embodiment. The partial expanded sectional perspective view of the lens-barrel main body and the condensing mirror part in the embodiment. The partial expanded sectional view which shows the lens-barrel main body in another embodiment, a condensing mirror part, and an objective lens. Furthermore, the elements on larger scale which show the lens-barrel main body in a different embodiment, a condensing mirror part, and an objective lens. The typical block diagram which shows the optical measuring device which concerns on other embodiment of this invention.

Explanation of symbols

EB: Energy beam (electron beam)
W ... Sample 21 ... Energy ray generator (electron gun)
225 ... objective lens 23 ... mirror surface 24 ... lens barrel part 24B ... condensing mirror part 24B1 ... energy beam passage 24A ... lens barrel body

Claims (2)

A sample measuring device for measuring light generated by irradiating a sample with energy rays,
An energy ray generating unit for generating energy rays;
A mirror that has energy beam control means for converging the energy beam generated by the energy beam generator, and that causes the energy beam control means to converge the energy beam so that its axis coincides with the axis of the energy beam control unit; A tube part;
An energy beam path provided between the lens barrel portion and the sample and passing through the energy beam focused by the lens barrel portion and irradiating the energy beam to the sample, and a focal point on the axis of the channel A collecting mirror part that collects the light generated from the sample by the mirror surface,
While allowing the lens barrel and the condensing mirror to be detachable, the axis of the energy beam control means and the axis of the energy beam passage are positioned coaxially so that the axis of the energy beam and the focal point are aligned. A positioning structure for supporting the light collecting mirror part in the lens barrel part so as to match,
Sample measurement in which the positioning mechanism is composed of a convex portion formed at the lower end of the barrel portion and a concave portion formed on the upper surface of the condenser mirror portion and formed substantially the same as the outer peripheral surface of the convex portion. apparatus.   The sample measuring apparatus according to claim 1, wherein the convex portion has an energy ray exit of the lens barrel portion, and the energy ray passage communicates with a bottom surface of the concave portion.