A method for preparing quartz glass plane TEM samples using FIB

Abstract

The present invention provides a method for preparing a quartz glass flat TEM sample using FIB, which belongs to the field of semiconductor manufacturing technology. The method comprises the following steps: S1, sample pretreatment; S2, FIB etching; S3, wedge correction: by using the U-shaped cutting tilt angle method, gradually adjusting the cutting angle and intensity of the ion beam, reducing the wedge degree of the wedge-shaped sample slice in step S2, and preparing a sample slice with an initial observation area; S4, fine polishing: introducing the back-cutting technology, by manipulating the nanomanipulator and tungsten welding technology, the observation area is separated from the sample slice to form an independent TEM sample; S5, sample post-processing. The present invention solves the problems of thick amorphous layer, large damage and low efficiency generated in the sample preparation process in the prior art by optimizing the ion beam parameters and processing steps and introducing improved back-cutting technology, thereby improving the preparation efficiency and quality of TEM samples.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a method for preparing a quartz glass plane TEM sample by adopting FIB. Background Art

[0002] Quartz glass, a common optical and electronic material, presents numerous challenges in preparing transmission electron microscopy (TEM) samples due to its high hardness and low conductivity. While traditional mechanical grinding and ion thinning methods can produce samples that meet requirements to a certain extent, they suffer from long preparation cycles, complex operations, and significant sample damage. Especially when preparing planar samples, the material's hardness and brittleness can easily lead to defects such as cracks and fractures during the preparation process, severely impacting sample quality and observability.

[0003] As an emerging micro-nano processing technology, focused ion beam technology (FIB) has the advantages of high precision, high efficiency, and non-contact processing, providing new possibilities for the preparation of high-quality quartz glass planar TEM samples.

[0004] Among existing quartz glass planar TEM sample preparation technologies, FIB (Fiber Injection Blade) is widely used due to its high precision and non-contact processing advantages, as shown in invention patent application number 201910003403.4. The steps for preparing TEM samples using FIB include sample pretreatment, FIB etching, and sample post-processing.

[0005] The pretreatment stage mainly involves the fixation of the sample and the enhancement of its conductivity, such as using conductive glue to fix the sample on the sample stage and performing gold spraying to improve the conductivity of the sample.

[0006] During the FIB etching stage, the traditional approach is to directly etch the sample using a focused ion beam to remove unwanted areas and create the desired observation area. However, due to the high hardness and low conductivity of quartz glass, traditional FIB etching methods often face problems such as excessive energy leading to significant sample damage and difficult to control beam spot size, resulting in low preparation precision.

[0007] Post-processing typically involves cleaning and purging the prepared TEM sample to remove residual FIB etching products and impurities. However, because samples prepared using traditional methods may suffer from damage and uneven thickness, post-processing often fails to fully repair these issues, impacting the quality and performance of the final sample.

[0008] Currently, traditional FIB preparation methods still have some problems, such as excessively high ion beam energy leading to significant sample damage, and difficulty controlling the ion beam spot size, resulting in low sample preparation precision. Therefore, it is necessary to improve and optimize traditional FIB preparation methods to meet the needs of TEM sample preparation for difficult-to-process materials such as quartz glass. Summary of the Invention

[0009] In view of the above problems, the present invention provides a method for preparing a planar TEM sample of quartz glass using FIB.

[0010] The method for preparing a quartz glass planar TEM sample using FIB comprises the following steps:

[0011] S1. Sample pretreatment: Fix the quartz glass sample on the sample stage and perform gold spraying on the quartz glass sample to enhance conductivity;

[0012] S2, FIB etching: Use FIB technology to etch the quartz glass sample to obtain a wedge-shaped sample slice with an initial observation area;

[0013] S3, wedge correction: by using the U-shaped cutting tilt angle method, gradually adjust the cutting angle and intensity of the ion beam to reduce the wedge shape of the wedge-shaped sample slice in step S2, and obtain a sample slice with an initial observation area;

[0014] S4, Fine Polishing: Introducing the inverted cutting technology, through the manipulation of nanomanipulators and tungsten welding technology, the observation area is separated from the sample slice to form an independent TEM sample;

[0015] S5. Sample post-processing: The TEM sample prepared in step S4 is purged and cleaned to remove the amorphous layer and damaged layer on the surface, thereby obtaining the quartz glass plane TEM sample.

[0016] The present invention provides a method for preparing a planar quartz glass TEM sample using FIB. During sample pretreatment, the conductivity of the quartz glass sample is enhanced to reduce charge accumulation and electron beam damage. For wedge-shaped sample slices after FIB treatment, a U-shaped cutting tilt angle method is first proposed to reduce the wedge shape. Combined with a back-cutting technique, the parallelism of the sample is further improved, avoiding imaging errors caused by sample unevenness. Finally, purging and cleaning processes are performed to ensure the cleanliness of the sample surface and reduce damage caused by electron beam irradiation, thereby improving the final imaging quality.

[0017] Preferably, in step S1, the fixing of the quartz glass sample on the sample stage specifically includes the following steps: fixing the quartz glass sample on the sample stage with conductive C glue, and bonding the sample to the sample stage with conductive Cu glue. Since the conductivity of quartz glass is poor, the sample is wrapped with conductive Cu glue.

[0018] Preferably, in step S1, the gold spraying treatment specifically includes the following steps: performing gold spraying treatment on the fixed quartz glass sample, leaving only the target processing area unsprayed with gold, so as to enhance conductivity.

[0019] Preferably, in step S2, the FIB etching specifically includes the following steps:

[0020] S201. Perform precise tungsten layer deposition. Set the electron beam voltage to 2 kV and the current to 6.4 nA. Plate a 0.3 μm thick tungsten layer on the target processing area of ​​the quartz glass sample as a protective layer. The tungsten layer protects the sample surface from damage during subsequent ion beam processing, thereby improving processing accuracy.

[0021] S202. Tilt the sample stage to 52°, set the ion beam energy to 10-20 keV, and continue ion beam deposition. Precise ion beam energy control can reduce damage to the quartz glass sample, ensure cutting accuracy, and maintain the microstructural integrity of the sample.

[0022] S203, setting the voltage and current of the ion beam to a low beam current of 30 kV and 2.5 nA, respectively, to machine deep pits in the upper and lower adjacent areas of the tungsten layer in the vertical direction;

[0023] S204, performing Cross-Sectional Shaping (CCS) refinement on the upper and lower edges of the tungsten layer when the sample stage tilt angle is 50° and 54°, respectively, to obtain a wedge-shaped sample slice with an initial observation area.

[0024] Preferably, in step S3, the U-shaped cutting tilt angle method specifically includes the following steps: when the sample stage returns to the 0° position, cutting the wedge-shaped sample slice into a cantilever beam shape; then, adjusting the tilt angle of the sample stage from 0° to -10°, and continuing to thin the wedge-shaped sample slice to obtain a sample slice with an initial observation area.

[0025] The U-shaped cutting tilt angle method can effectively reduce the thickness of the other side of the wedge-shaped sample slice after processing by precisely controlling the angle of the sample stage and the parameters of the ion beam. It can also precisely control the cutting and thinning process of the wedge-shaped sample slice, effectively reduce the wedge shape of the wedge-shaped sample slice, and obtain a thinner and more uniform sample slice.

[0026] Preferably, in step S3, during the thinning process, the tilt angle is set to ±1.5°, the thinning voltage is maintained at 25-30 kV, and the sample is finely polished by using a method of gradually reducing the ion beam current.

[0027] Through precise control of the tilt angle and ion beam current, high-precision thinning of wedge-shaped sample slices is achieved, which not only improves processing accuracy and preparation efficiency, but also optimizes sample morphology and reduces sample damage. By setting the tilt angle, the interaction between the ion beam and the sample surface is precisely controlled, thereby achieving a more uniform and fine polishing effect.

[0028] Further preferably, when the thickness of the wedge-shaped sample slice is greater than 200 nm, the ion beam current is 0.23 nA; when the thickness of the wedge-shaped sample slice is 100-200 nm, the ion beam current is 80 pA; when the thickness of the wedge-shaped sample slice is 80-100 nm, the ion beam current is 40 pA.

[0029] The method of gradually reducing the ion beam current for different thicknesses avoids excessive processing when the sample approaches the target thickness, reduces ion beam damage to the sample surface, maintains the microstructural integrity of the sample, and can complete the thinning process more effectively and efficiently.

[0030] Preferably, in step S3, the thickness of the prepared sample slice is 80-100 nm, which is suitable for TEM observation, ensuring the penetration of the electron beam and meeting the requirements of high-resolution imaging.

[0031] In order to further improve the quality of the sample and the observation effect, the sample was finely polished by gradually reducing the ion beam voltage. The specific steps include the following: when the wedge-shaped sample slice is less than 100 nm, it is first thinned under the conditions of 5 kV and 15 pA, and then further thinned under the conditions of 2 kV and 9 pA until the tungsten layer gradually becomes thinner and has good light transmission under the conditions of 3 kV, ensuring that the impurities in the amorphous layer have been removed and the sample is finely polished.

[0032] Preferably, in step S3, an in-situ nanomanipulator and a gas injection system (GIS) are simultaneously combined to precisely control the cutting and thinning process of the sample.

[0033] Preferably, in step S4, the inverted cutting technology specifically includes the following steps: after completing the wedge correction in step S3, adjust the relative position of the nanomanipulator and the sample slice, rotate the nanomanipulator 180°, cut off the wedge-shaped part of the sample slice with an ion beam, and then adjust the sample slice and the copper column to the same plane, use tungsten material to weld them, and then cut off the cantilever arm to obtain a TEM sample.

[0034] Preferably, in step S5, the purging and cleaning treatment specifically includes the following steps: tilting the sample stage to ±3°, setting the ion beam voltage to 5 kV and the current to 15 pA, purging the front and rear surfaces of the TEM sample obtained in step S4 for 30 s each, and repeating the purging 2 to 3 times; then continuing to tilt the sample stage to ±5°, setting the ion beam voltage to 2 kV and the current to 9 pA, and purging the front and rear surfaces of the TEM sample for 10 to 60 s each.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The method for preparing planar quartz glass TEM samples using FIB provided by the present invention improves sample preparation efficiency. The present invention uses an improved undercutting technique to quickly and accurately prepare high-quality planar quartz glass TEM samples, reducing preparation time.

[0037] 2. The method provided by the present invention for preparing a planar quartz glass TEM sample using FIB reduces sample damage. By optimizing the FIB parameters and etching process, the present invention reduces sample damage and improves sample quality and stability.

[0038] 3. The method provided by the present invention for preparing planar quartz glass TEM samples using FIB improves the thickness uniformity of the samples. The present invention uses an improved undercutting technique to achieve precise control of sample thickness, avoiding the problem of uneven sample thickness in traditional methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a planar TEM sample image of the quartz glass prepared in Example 1. DETAILED DESCRIPTION

[0040] The technical scheme of the present invention is further described below through examples. The raw materials used in the examples can be purchased from the market or prepared by conventional methods.

[0041] Example 1

[0042] A method for preparing a quartz glass planar TEM sample using FIB comprises the following steps:

[0043] S1. Sample pretreatment: The quartz glass sample is fixed on the sample stage with conductive C glue, and the sample is adhered to the sample stage with conductive Cu glue. Since the conductivity of quartz glass is poor, the sample is wrapped with conductive Cu glue; then the fixed quartz glass sample is sprayed with gold using an ion sputtering instrument, leaving only the target processing area without gold spraying to enhance conductivity.

[0044] S2, FIB etching: In the FIB equipment, the quartz glass sample is initially cut by precisely controlling the focused ion beam, which specifically includes the following steps:

[0045] S201, performing precise tungsten layer deposition, setting the electron beam voltage to 2 kV and the current to 6.4 nA, and depositing a tungsten layer with a thickness of 0.3 μm on the target processing area of ​​the quartz glass sample as a protective layer;

[0046] S202, tilting the sample stage to 52°, setting the energy of the gallium ion source ion beam to 10-20 keV, and continuing ion beam deposition to reduce damage to the quartz glass sample and ensure cutting accuracy;

[0047] S203, setting the voltage and current of the ion beam to a low beam current of 30 kV and 2.5 nA, respectively, to machine deep pits in the upper and lower adjacent areas of the tungsten layer in the vertical direction;

[0048] S204, performing Cross-Sectional Shaping (CCS) refinement on the upper and lower edges of the tungsten layer when the sample stage tilt angle is 50° and 54°, respectively, to obtain a wedge-shaped sample slice with an initial observation area.

[0049] S3. Wedge correction: Due to the hard and brittle nature of quartz glass, a wedge-shaped sample is formed after initial cutting. In order to reduce the wedge-shaped degree of the wedge-shaped sample slice in step S2, the in-situ nanomanipulator and gas injection system (GIS) are combined to accurately control the cutting and thinning process of the sample. Specifically, the following steps are included:

[0050] When the sample stage returns to the 0° position, the wedge-shaped sample slice is cut into a cantilever beam shape; then, the tilt angle of the sample stage is adjusted from 0° to -10°, and the wedge-shaped sample slice is continued to be thinned. During the thinning process, the tilt angle is set to ±1.5°, the thinning voltage is maintained at 30 kV, and the sample is finely polished by gradually reducing the ion beam current. That is, when the thickness of the wedge-shaped sample slice is greater than 200 nm, the ion beam current is 0.23 nA; when the thickness of the wedge-shaped sample slice is 100-200 nm, the ion beam current is 80 pA; when the thickness of the wedge-shaped sample slice is 80-100 nm, the ion beam current is 40 pA; a sample slice with a thickness of 80-100 nm and an initial observation area is obtained;

[0051] In order to further improve the quality of the sample and the observation effect, the sample was finely polished by gradually reducing the ion beam voltage. The specific steps include the following: when the wedge-shaped sample slice is less than 100 nm, it is first thinned under the conditions of 5 kV and 15 pA, and then further thinned under the conditions of 2 kV and 9 pA until the tungsten layer gradually becomes thinner and has good light transmission under the conditions of 3 kV, ensuring that the impurities in the amorphous layer have been removed and the sample is finely polished.

[0052] S4. Fine polishing: Introduce the reverse cutting technology, and separate the observation area from the sample slice by manipulating the nanomanipulator and tungsten welding technology. Specifically, it includes the following steps: After completing the wedge correction in step S3, adjust the relative position of the nanomanipulator and the sample slice, rotate the nanomanipulator 180°, use the ion beam to cut off the wedge-shaped part of the sample slice, and then adjust the sample slice and the copper column to the same plane, use tungsten material for welding, and then cut off the cantilever arm to obtain the TEM sample.

[0053] S5. Sample post-processing: The TEM sample prepared in step S4 is purged and cleaned to remove the amorphous layer and damaged layer on the surface, specifically comprising the following steps: tilting the sample stage to ±3°, setting the ion beam voltage to 5 kV and the current to 15 pA, purging the front and back surfaces of the TEM sample prepared in step S4 for 30 s each, and repeating the purging 2 to 3 times; then further tilting the sample stage to ±5°, setting the ion beam voltage to 2 kV and the current to 9 pA, purging the front and back surfaces of the TEM sample for 60 s each, stopping at any time according to the actual situation of the sample, retaining the original structure and characteristics of the sample, and preparing the quartz glass plane TEM sample.

[0054] The prepared quartz glass plane TEM sample was tested. Figure 1 As shown, the prepared quartz glass plane TEM sample meets the observation requirements through TEM observation. If necessary, steps S3 to S5 can be repeated to improve the observation effect.

[0055] It should be understood that the above embodiments are only intended to illustrate the present invention and are not intended to limit the scope of protection of the present invention. In addition, it should be understood that after reading the contents of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A method for preparing a quartz glass flat TEM sample using FIB, characterized in that: The following steps are involved: S1. Sample pretreatment: Fix the quartz glass sample on the sample stage and perform gold spraying on the quartz glass sample; S2, FIB etching: Use FIB technology to etch the quartz glass sample to obtain a wedge-shaped sample slice with an initial observation area; S3, wedge correction: by using the U-shaped cutting tilt angle method, gradually adjust the cutting angle and intensity of the ion beam to reduce the wedge shape of the wedge-shaped sample slice in step S2, and obtain a sample slice with an initial observation area; S4, Fine Polishing: Introducing the inverted cutting technology, through the manipulation of nanomanipulators and tungsten welding technology, the observation area is separated from the sample slice to form an independent TEM sample; S5, sample post-processing: purging and cleaning the TEM sample prepared in step S4 to remove the amorphous layer and damaged layer on the surface, thereby obtaining the quartz glass plane TEM sample; In step S3, the U-shaped cutting tilt angle method specifically includes the following steps: when the sample stage returns to the 0° position, the wedge-shaped sample slice is cut into a cantilever beam shape; then, the tilt angle of the sample stage is adjusted from 0° to -10°, and the wedge-shaped sample slice is continued to be thinned to obtain a sample slice with an initial observation area.

2. The method for preparing a quartz glass planar TEM sample using FIB according to claim 1, characterized in that: In step S1, the quartz glass sample is fixed on the sample stage, which specifically includes the following steps: fixing the quartz glass sample on the sample stage with conductive C glue, and bonding the sample to the sample stage with conductive Cu glue. Since the conductivity of quartz glass is poor, the sample is wrapped with conductive Cu glue.

3. The method for preparing a quartz glass planar TEM sample using FIB according to claim 1, characterized in that: In step S1, the gold spraying treatment specifically includes the following steps: performing gold spraying treatment on the fixed quartz glass sample, leaving only the target processing area unsprayed with gold.

4. The method for preparing a quartz glass planar TEM sample using FIB according to claim 1, characterized in that: In step S2, the FIB etching specifically includes the following steps: S201, performing precise tungsten layer deposition, setting the electron beam voltage to 2 kV and the current to 6.4 nA, and depositing a tungsten layer with a thickness of 0.3 μm on the target processing area of ​​the quartz glass sample as a protective layer; S202, tilt the sample stage to 52 degrees, set the energy of the ion beam to 10-20 keV, and continue ion beam deposition to reduce damage to the quartz glass sample and ensure cutting accuracy; S203, setting the voltage and current of the ion beam to a low beam current of 30 kV and 2.5 nA, respectively, to machine deep pits in the upper and lower adjacent areas of the tungsten layer in the vertical direction; S204, performing Cross-Sectional Shaping on the upper and lower edges of the tungsten layer when the sample stage tilt angle is 50° and 54°, respectively, to obtain a wedge-shaped sample slice with an initial observation area.

5. The method for preparing a planar TEM sample of quartz glass using FIB according to claim 1, wherein: In step S3, during the thinning process, the tilt angle is set to ±1.5°, the thinning voltage is maintained at 25-30 kV, and the sample is finely polished by gradually reducing the ion beam current.

6. The method for preparing a planar TEM sample of quartz glass using FIB according to claim 5, wherein: When the thickness of the wedge-shaped sample slice is greater than 200 nm, the ion beam current is 0.23 nA; when the thickness of the wedge-shaped sample slice is 100-200 nm, the ion beam current is 80 pA; when the thickness of the wedge-shaped sample slice is 80-100 nm, the ion beam current is 40 pA.

7. The method for preparing a planar TEM sample of quartz glass using FIB according to claim 1, wherein: In step S3, the sample is finely polished by gradually reducing the ion beam voltage, which specifically includes the following steps: when the wedge-shaped sample slice is less than 100 nm, it is first thinned under the conditions of 5 kV and 15 pA, and then further thinned under the conditions of 2 kV and 9 pA until the tungsten layer gradually becomes thinner and has good light transmittance under the condition of 3 kV, ensuring that the impurities in the amorphous layer have been removed and the sample is finely polished.

8. The method for preparing a quartz glass planar TEM sample using FIB according to claim 1, characterized in that: In step S4, the inverted cutting technology specifically includes the following steps: after completing the wedge correction in step S3, adjust the relative position of the nanomanipulator and the sample slice, rotate the nanomanipulator 180°, use an ion beam to cut off the wedge-shaped part of the sample slice, and then adjust the sample slice and the copper column to the same plane, use tungsten material to weld them, and then cut off the cantilever arm to obtain a TEM sample.

9. The method for preparing a planar TEM sample of quartz glass using FIB according to claim 1, wherein: In step S5, the purging and cleaning treatment specifically includes the following steps: tilting the sample stage to ±3°, setting the ion beam voltage to 2~5 kV and the current to 9~15 pA, purging the front and back surfaces of the TEM sample prepared in step S4 for 10~30 s respectively, and repeating the purging 2~3 times; then further tilting the sample stage to ±5°, setting the ion beam voltage to 2 kV and the current to 9 pA, and purging the front and back surfaces of the TEM sample for 30~60 s respectively.

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