CN112730006B - Preparation method of pore surface ion channel contrast sample - Google Patents

Abstract

The invention relates to a method for preparing a hole surface ion channel contrast sample in the micronano-scale size range. The polished surface (8) of the hole surface ion channel contrast sample (3) is subjected to at least one focused ion beam (5) Pre-polishing, at least one cross-type focused ion beam (5) rough polishing, at least one cross-type focused ion beam (5) fine polishing, until the polished surface (8) of the hole surface ion channel contrast sample (3) is removed Scratch and amorphous layer deposition on. The present invention can not only make fixed-point samples for the specified area of the ion channel contrast sample on the hole surface, but also have no stress residue, no abrasive pollution, no parallel scratches, no amorphous layer deposition, etc. features. The invention has high image definition when performing ion channel contrast (ICC) test, and can clearly and accurately observe information such as grain structure, size, distribution, defect and the like.

Description

A kind of preparation method of hole surface ion channel contrast sample

technical field

The invention relates to the technical field of electron microscope standard value testing, in particular to a method for preparing a hole surface ion channel contrast sample in the micronano-scale size range.

Background technique

Focused ion beam scanning electron microscope is a device that combines high-resolution electron microscopic imaging system and fast and accurate ion beam processing system to provide fast and efficient material characterization, analysis and processing. The electron beam of the focused ion beam scanning electron microscope is mainly used for material micro-area imaging, and its direction is perpendicular to the horizontal plane downward; the ion beam of the equipment is mainly used for material micro-area processing, and its fixed inner angle with the horizontal plane is 38° . The focused ion beam scanning electron microscope can polish the micro-nano polished surface, and the polishing direction can be rotated and adjusted to be parallel to the polished surface according to the position of the polished surface of the sample.

When the accelerated and focused ion beam bombards the surface of a flat crystal sample, the crystal orientation will directly affect the scattering direction and depth of the incident ions. The energy of the secondary electrons excited by the incident ions is less than 50eV, and they are only excited within a depth of less than 10 nanometers. Only secondary electrons can escape from the surface of the sample. Therefore, differences in the scattering direction and depth of incident ions caused by crystals with different orientations will significantly affect the yield of secondary electrons, so that the secondary electrons excited by the ion beam received by the detector The intensity of the signal changes, thus forming the ion channel contrast (ICC for short). In polycrystalline materials, the orientation of each crystal grain is different from the included angle of the incident ion beam, showing different ion channel contrast. Therefore, ion channel contrast can quickly and accurately observe information such as grain shape, size, distribution, defects, etc., and has high energy and strong contrast, which is an effective means of material characterization.

Ion Channel Contrast (ICC) generally selects the polishing area according to the purpose of detection. Factors such as the selection of accelerating voltage and beam current will seriously affect the imaging quality of the ion channel contrast, or even fail to image. In the prior art, mechanical polishing and argon ion beam milling are generally used to prepare ion channel contrast samples. The surface crystal structure of the ion channel contrast sample prepared by mechanical polishing is damaged by stress, and the abrasive is difficult to remove when it is buried in the pores, and there is an amorphous layer deposited, which covers the ion channel contrast and cannot obtain a clear ion channel contrast image. ; The argon ion beam milling method is also commonly used to prepare ion channel contrast samples. This method is suitable for the preparation of large-area observation targets, and cannot be used to prepare samples for specified micro-areas; the ion channel lining prepared by conventional focused ion beam polishing High-precision samples can achieve precise sample preparation, but there are tiny parallel scratches on the surface of the prepared samples, which seriously affect the imaging effect of ion channel contrast after being magnified and imaged by electron beam scanning. Therefore, the imaging quality of the ion channel contrast sample prepared by the above method is not satisfactory. Moreover, these two sample preparation methods can only prepare the surface of the ion channel contrast sample by polishing, but cannot prepare the specified internal area, so the applicability of the above two methods is limited.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method that overcomes the deficiencies of the prior art, is used for polishing the internal micro-nano structure of the ion channel contrast sample, and can clearly observe information such as grain structure, size, distribution, and defects. , a preparation method for improving the imaging quality of ion channel contrast specimens on the hole surface. The technical solution adopted by the present invention to solve the technical problem is: a preparation method of the hole surface ion channel contrast sample, a, using conductive glue to paste the hole surface ion channel contrast sample 3 on the surface of the focused ion beam scanning electron microscope On the stage 2, b. Open the door of the sample chamber of the focused ion beam scanning electron microscope, and put the rotating shaft 6 firmly connected with the stage 2 into the sample stage 1 in the sample chamber of the focused ion beam scanning electron microscope, Close the door of the sample chamber, and evacuate the sample chamber to a negative pressure of 1×10 ^-3 ~ 1×10 ^-5 Pa, adjust the three-dimensional axis coordinates of the sample stage 1 of the focused ion beam scanning electron microscope, so that the ion channel contrast of the hole surface The sample preparation area 7 of the sample 3 is moved to the intersection point of the electron beam 4 and the focused ion beam 5 of the focused ion beam scanning electron microscope, c, adjust the inclination angle of the rotation axis 6, so that the polishing direction of the focused ion beam 5 is in line with the hole surface The upper surface of the ion channel contrast sample 3 is vertical, and the length, width and depth of the sample preparation area 7 are cut with the operating software that comes with the focused ion beam scanning electron microscope, and the polished surface 8 of the ion channel contrast sample 3 on the hole surface is Perform at least one focused ion beam pre-polishing, d, adjust the rotation angle of the rotation axis 6, perform at least one cross-type focused ion beam 5 rough polishing on the polished surface 8 of the hole surface ion channel contrast sample 3, e, adjust the rotation axis 6 rotation angle, the polished surface 8 of the ion channel contrast sample 3 on the hole surface is finely polished with a cross-type focused ion beam 5 at least once, until the scratches on the polished surface 8 of the ion channel contrast sample 3 on the hole surface are removed and amorphous layer deposition.

The technical problem to be solved by the present invention can be further solved by the following technical scheme: the fixed inner angle between the inclined plane of the sample stage 1 parallel to the horizontal plane and the horizontal plane is 45°; The vacuum negative pressure is 1×10 ^-3 , 1×10 ^-4 Pa or 1×10 ^-5 Pa; the pre-polishing is to adjust the inclination angle of the rotation axis 6 so that the distance between the focused ion beam scanning electron microscope sample stage 1 and the horizontal plane The inclination angle is 7°, that is, the inner angle between the stage 2 and the horizontal plane is 52°, so as to meet the requirement that the polishing direction of the ion beam 5 is perpendicular to the upper surface of the ion channel contrast sample 3 on the hole surface; The polished surface 8 of the ion channel contrast sample 3 was pre-polished with a focused ion beam at least once, the accelerating voltage of the pre-polishing was 30kV, the ion beam current was 5nA, and the pre-polishing time was 5min; At least one focused ion beam pre-polishing is performed on the polished surface 8 of the pre-polished sample preparation area 7, and the sample preparation width a of the pre-polished sample preparation area 7 is at least 1.3 times of the sample preparation depth b; the polished surface 8 of the hole surface ion channel contrast sample 3 is at least Perform a cross-type focused ion beam rough polishing to adjust the inclination angle of the rotation axis 6, so that the inclination angle between the focused ion beam scanning electron microscope sample stage 1 and the horizontal plane is 0°, and adjust the rotation axis 6 to +40°, -40° °, and adjust the focused ion beam polishing direction to be parallel to the polishing surface 8, the acceleration voltage of rough polishing is 30kV, the ion beam current is 3.2nA, and the rough polishing time is 2min; the polished surface 8 of the ion channel contrast sample 3 on the hole surface Perform at least one cross-type focused ion beam fine polishing to adjust the rotation axis 6 to +40°, -40°, and adjust the focused ion beam polishing direction to be parallel to the polishing surface 8. The acceleration voltage for fine polishing is 5kV, and the ion beam current is 1nA , the fine polishing time is 3min; the focused ion beam is gallium focused ion beam, xenon ion beam, oxygen ion beam or argon ion beam. During the process of adjusting the rotation axis 6 to +40° and -40°, the movement track surface of the stage 2 and the ion channel contrast sample 3 on the hole surface is a conical surface.

The carrier of the pore surface ion channel contrast sample in the present invention is selected from the prior art nickel-cobalt lithium manganate ternary material, integrated circuit material, biomedical material, new energy material or metal material, preferably integrated circuit material. In the process of chip design and processing, there are micro-nano-level defects inside the product, such as foreign matter, corrosion, oxidation and other problems. This method can be used to accurately locate cutting and polishing, prepare cross-sectional samples of defect positions, and then use SEM to observe the cross-sectional structure of the material and Material, fixed-point analysis of chip structure defects, so as to formulate integrated circuit design solutions faster and more accurately. The method is of great significance for shortening the research and development cycle, saving research and development costs, and improving the preparation process.

The working principle of the present invention is as follows: the accelerated and focused ion beam is used to bombard the sample, and the energy of the ion beam is transferred to the sample to form an ion channel contrast sample.

The focused ion beam of the present invention is gallium focused ion beam, xenon ion beam, oxygen ion beam or argon ion beam. On the one hand, in the process of focused ion beam polishing, due to the differences in the grain orientation and surface roughness of the sample, the sample preparation of the prior art focused ion beam polishing only proceeds to the pre-polishing stage. At this time, the polished surface of the sample A series of parallel scratches that remain after pre-polishing with focused ion beams tend to be formed. The shape of such parallel scratches is similar to a hanging curtain, which is called "curtain effect". When there is a "curtain effect" in the polished area, it will directly affect the scattering direction and depth of incident ions, change the relative orientation of the ion beam and the sample surface, reduce the yield of secondary electrons, and affect the ion channel contrast imaging. On the other hand, amorphous deposits are generated during focused ion beam polishing, and these amorphous deposits are deposited on the polished surface of ion channel contrast specimens. Due to the low energy of the secondary electrons excited by the incident ions, the ion channel contrast (ICC) only occurs within a few nanometers of the sample surface, and the amorphous deposits will greatly reduce the escape of secondary electrons. Therefore, the imaging quality of the ion channel contrast image will be seriously affected.

In order to overcome the shortcomings of the existing technology and improve the imaging quality of the ion channel contrast sample, the ion channel contrast sample is first pre-polished to remove various scratches with obvious bumps in the polished area. At this time, there is a "curtain effect" in the polished area. And the deposition of amorphous layer substances will have a serious impact on ion channel contrast imaging. In view of these phenomena, the tilt angle between the focused ion beam scanning electron microscope sample stage 1 and the horizontal plane is restored to 0°, and the rotation angle of the rotation axis is changed by adjusting the spatial angle relationship between the rotation angle of the rotation axis and the polishing direction of the focus ion beam For a specific ±40°, change the polishing direction of the focused ion beam at the same time, so that the polishing direction of the focused ion beam in three-dimensional space is parallel to the polishing surface, reduce the ion beam current, reduce the polishing time, and rough polish the polishing surface; Cross-type focused ion beam rough polishing to remove parallel scratches on the polished surface; further reduce the accelerating voltage and ion beam current, increase the polishing time, change the rotation angle of the rotation axis to a specific ±40°, and change the polishing direction of the focused ion beam , satisfying that the focused ion beam polishing direction in three-dimensional space is parallel to the polishing surface, the polishing surface is cross-polished, and the amorphous deposition deposited on the polishing surface is removed, thereby eliminating the "curtain effect". The present invention selects the Helios focused ion beam scanning electron microscope produced by Thermo Fisher Scientific Corporation. The so-called "adjusting the three-dimensional axis coordinates of the sample stage of the focused ion beam scanning electron microscope", "adjusting the inclination angle of the rotation axis of the sample stage of the focused ion beam scanning electron microscope", "adjusting the sample stage of the focused ion beam scanning electron microscope" The angle of rotation of the axis of rotation" are inherent features of the focused ion beam scanning electron microscope.

Due to the adoption of the above-mentioned technical scheme, the present invention has the following beneficial effects: Compared with the preparation method of the prior art, by adjusting the spatial angle relationship between the rotation angle of the rotation axis and the focused ion beam polishing direction, the angle of the rotation axis and the focused ion beam polishing can be changed. Direction, acceleration voltage, ion beam current, and polishing time are used for cross-polishing, which can not only perform fixed-point sample preparation for the inside of the ion channel contrast sample, but also the prepared ion channel contrast sample has no stress residue, no abrasive pollution, No parallel scratches, no amorphous layer deposition, etc., removes the parallel scratches on the surface of the ion channel contrast sample and the amorphous state deposited on the sample surface, thereby eliminating the "curtain effect" of the prior art, and greatly Improving the imaging quality of ion channel contrast images. The invention has high image definition when performing ion channel contrast (ICC) test, and can clearly observe information such as grain structure, size, distribution, defect and the like. The invention intuitively characterizes the homogeneity of the material coating layer and the distribution of doping elements, the microstructure and defects in the semiconductor material, etc., and plays a key technical support role in analyzing and optimizing the preparation process of the material.

Description of drawings

The present invention will be described in further detail below in conjunction with accompanying drawing and specific embodiment of the present invention:

Fig. 1 is a schematic structural view of the present invention, reference numerals 7 and 8 are enlarged views of the sample preparation area 7 of the hole surface ion channel contrast sample 3, wherein a is the sample preparation width of the sample preparation area 7, and b is the sample preparation area 7 sample preparation depth;

Fig. 2 is a schematic diagram of focused ion beam pre-polishing of the present invention (that is, a schematic diagram of the direction of action of the focused ion beam);

Fig. 3 is a schematic diagram of cross-type focused ion beam rough polishing and fine polishing of the present invention (that is, a schematic diagram of the direction of action of the focused ion beam);

Fig. 4 is the sample imaging figure of ion channel contrast of the hole surface of the present invention;

Fig. 5 is a sectional view along A-A of Fig. 4 .

Detailed ways

Embodiment 1: referring to Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, the ion channel contrast sample 3 of the present invention is pasted on the focused ion beam scanning electron microscope stage 2, and the stage 2 is rotated The axis 6 is connected to the sample stage 1, and the coordinates of the three-dimensional axis of the sample stage of the focused ion beam scanning electron microscope equipment are adjusted so that the sample preparation area 7 of the ion channel contrast sample is located at the intersection of the electron beam 4 and the ion beam 5, and the rotation is adjusted The axis 6 cuts the rectangular sample preparation area 7 and polishes the polished surface 8 to prepare the ion channel contrast sample 3 on the hole surface.

First, use conductive glue to paste the longitudinal axis of symmetry of the ion channel contrast sample on the hole surface coincident with or parallel to the axis of longitudinal symmetry of the stage, and make it possible to cut the rectangular sample preparation area afterwards. At 7 o'clock, make its polished surface 8 protrude about 1mm from the end face of the stage inclined at 45°; secondly, open the door of the sample chamber of the focused ion beam scanning electron microscope, and the rotating shaft that is firmly connected with the stage is automatically passed through the sample stage. The bolts of the belt are tightly connected to the sample stage, and the rotation axis is in the initialization state of 0°. At this time, the object stage, the rotation axis and the sample stage form a rigid body and are in the initialization state synchronously with the rotation axis. Close the door of the sample chamber and put The sample chamber is evacuated to a negative pressure of 1×10 ^-3 Pa, 1×10 ^-4 Pa or 1×10 ^-5 Pa, and the coordinates of the three-dimensional axis of the sample stage of the focused ion beam scanning electron microscope are adjusted to make the ion channel contrast test on the hole surface The sample preparation area is moved to the intersection of the electron beam and the focused ion beam of the focused ion beam scanning electron microscope, and the tilt angle of the rotation axis is adjusted so that the tilt angle between the focused ion beam scanning electron microscope sample stage and the horizontal plane is 7°, Even if the stage and the ion channel contrast sample have been increased by 7° under the state of inclination of 45°, the inner angle between the stage and the horizontal plane is 52° at this time, and the fixed inner angle between the ion beam and the horizontal plane is 38° (the angle between the ion beam and the surface plane of the ion channel contrast sample is 90°), to meet the requirement that the focused ion beam polishing direction is perpendicular to the upper surface of the ion channel contrast sample; again, use the focused ion beam The operating software that comes with the beam scanning electron microscope cuts the length, width a, and depth b of the sample preparation area 7, and performs focused ion beam pre-polishing on the polished surface of the sample. The accelerating voltage for pre-polishing is 30kV, and the gallium focused ion beam current is 5nA . The polishing time is 5 minutes. The width a of the sample preparation area is at least 1.3 times greater than the depth b, so as to obtain a relatively smooth polished surface of the ion channel contrast sample. After the pre-polishing of the focused ion beam is completed, adjust the inclination angle of the rotation axis 6, Make the inclination angle between the focused ion beam scanning electron microscope sample stage 1 and the horizontal plane 0°; then, use the gallium ion beam to perform cross-type focused ion beam rough polishing on the polished surface of the ion channel contrast sample, and the accelerating voltage is 30kV, The gallium ion beam current is 3.2nA, rotate the rotation axis firmly connected with the stage to +40°, adjust the polishing direction of the focused ion beam to be parallel to the polishing surface at this time, and the polishing time is 2min, and fasten to the stage Rotate the connected rotation axis by -40°, adjust the focused ion beam polishing direction to be parallel to the polishing surface, and the polishing time is 2 minutes. Repeat the above steps until the parallel scratches on the polishing surface of the ion channel contrast sample are removed; finally, use a low acceleration voltage The gallium ion beam performs cross-type focused ion beam fine polishing on the polished surface of the ion channel contrast sample, the acceleration voltage is 5kV, the gallium ion beam current is 1nA, and the rotation axis firmly connected with the stage is rotated to +40°, Adjust the focused ion beam polishing direction to be parallel to the polishing surface at this time, and the polishing time is 3 minutes. Rotate the rotation axis tightly connected to the stage by -40°, and adjust the focused ion beam polishing direction to The polished surfaces are parallel, and the polishing time is 3 minutes to remove the amorphous deposits on the surface of the polished surface of the ion channel contrast sample, thereby eliminating the "curtain effect". The rotating shaft is firmly connected to the stage, and when the rough polishing and fine polishing rotate -40°, +40°, the inner angle between the stage 2 and the horizontal plane is always 45° (that is, the inclination angle of the rotating axis 6 is adjusted so that The tilt angle between the focused ion beam scanning electron microscope sample stage 1 and the horizontal plane returns to the initialization state when it is 0°). The maximum length of the polishing surface 8 in this embodiment is 1 mm.

The above-mentioned embodiments are further detailed descriptions of the present invention, and it should not be considered that the above-mentioned embodiments have exhausted all the embodiments of the present invention. For those skilled in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction, replacement, and exchange can also be made, which should be regarded as belonging to the protection scope of the claims of the present invention.

Claims (1)

1. A preparation method of a pore surface ion channel contrast sample is characterized by comprising the following steps: a. b, pasting a hole surface ion channel contrast sample (3) on an object stage (2) of the focused ion beam scanning electron microscope by using conductive adhesive, opening a sample chamber door of the focused ion beam scanning electron microscope, and placing a rotating shaft (6) fixedly connected with the object stage (2) into a sample stage in a sample chamber of the focused ion beam scanning electron microscope(1) Closing the door of the sample chamber, and vacuumizing the sample chamber to 1 × 10 ^-3 ～1×10 ^-5 Pa, adjusting the three-dimensional axial coordinates of a sample stage (1) of the focused ion beam scanning electron microscope, moving a sample preparation area (7) of the hole surface ion channel contrast sample (3) to the intersection point of an electron beam (4) and the focused ion beam (5) of the focused ion beam scanning electron microscope, c, adjusting the inclination angle of a rotating shaft (6), enabling the polishing direction of the focused ion beam (5) to be vertical to the upper surface of the hole surface ion channel contrast sample (3), cutting the length, the width a and the depth b of the sample preparation area (7) by using operating software carried by the focused ion beam scanning electron microscope, and pre-polishing the polished surface (8) of the hole surface ion channel contrast sample (3) by the focused ion beam (5) at least once, d, adjusting the rotation angle of the rotating shaft (6), roughly polishing the polished surface (8) of the aperture surface ion channel contrast sample (3) by at least one time of crossed focused ion beam (5), e, adjusting the rotation angle of the rotating shaft (6), finely polishing the polished surface (8) of the aperture surface ion channel contrast sample (3) by at least one time of crossed focused ion beam (5) until scratches and amorphous layer deposition on the polished surface (8) of the aperture surface ion channel contrast sample (3) are removed, vertically placing the object stage (2) into a fixed inner included angle of 45 degrees between an inclined plane of the sample stage (1) parallel to the horizontal plane and the horizontal plane through the rotating shaft (6), the vacuum negative pressure is 1 multiplied by 10 ^-3 、1×10 ^{- 4} Pa or 1X 10 ^-5 Pa，

The pre-polishing is to adjust the inclination angle of a rotating shaft (6), to ensure that the inclination angle between a sample stage (1) of the focused ion beam scanning electron microscope and the horizontal plane is 7 degrees, namely to ensure that the inner included angle between an object stage (2) and the horizontal plane is 52 degrees, to meet the requirement that the polishing direction of a focused ion beam (5) is vertical to the upper surface of a hole surface ion channel contrast sample (3), the pre-polishing of the focused ion beam is carried out on the polishing surface (8) of the hole surface ion channel contrast sample (3) at least once, the acceleration voltage of the pre-polishing is 30kV, the ion beam current is 5nA, the pre-polishing time is 5min,

at least one time of pre-polishing by focused ion beams is carried out on a polished surface (8) of the hole surface ion channel contrast sample (3), the sample preparation width a of a pre-polished sample preparation area (7) is at least 1.3 times of the sample preparation depth b, at least one time of crossed type rough polishing by focused ion beams is carried out on the polished surface (8) of the hole surface ion channel contrast sample (3) to adjust the inclination angle of a rotating shaft (6), the inclination angle between a sample stage (1) of a focused ion beam scanning electron microscope and the horizontal plane is 0 degrees, the rotating shaft (6) is adjusted to be +40 degrees and-40 degrees, adjusting the polishing direction of a focused ion beam to be parallel to a polishing surface (8), wherein the acceleration voltage of rough polishing is 30kV, the ion beam current is 3.2nA, the rough polishing time is 2min, performing crossed focused ion beam finish polishing on the polishing surface (8) of an aperture ion channel contrast sample (3) at least once to adjust a rotating shaft (6) to +40 degrees and-40 degrees, adjusting the polishing direction of the focused ion beam to be parallel to the polishing surface (8), the acceleration voltage of finish polishing is 5kV, the ion beam current is 1nA, the finish polishing time is 3min, and the focused ion beam is gallium focused ion beam, xenon ion beam, oxygen ion beam or argon ion beam.

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