Test piece protection method for preventing damage caused by laser bombardment

Abstract

The invention discloses a test piece protection method for preventing damage caused by laser bombardment. By constructing a ternary composite protection system of a hydrophobic polymer layer / an aluminum oxide surface layer / a CVD platinum layer, the problems of material projection and thermal damage in the laser thinning process are effectively solved. The method comprises the following specific steps: (1) marking a target thinning area of a test piece; (2) coating a 1000-1500nm hydrophobic polymer layer (polyethylene, polystyrene and the like); (3) depositing an aluminum oxide heat insulation layer by adopting an ALD technology; (4) preparing a high-reflectivity platinum protection layer through a CVD (chemical vapor deposition) process; and (5) after implementing laser bombardment, removing the protective layer in a lossless manner by using an organic solvent (methanol / acetone and the like). According to the invention, the low surface energy characteristic of the polymer layer inhibits wreckage adhesion; (2) local heat accumulation is dispersed by utilizing high heat conductivity of aluminum oxide; and (3) the direct effect of laser is reduced by means of the high reflectivity of the CVD platinum layer.

Description

Technical Field

[0001] This invention relates to the field of semiconductor test piece preparation, and more specifically to a method for protecting test pieces from damage caused by laser bombardment. Background Technology

[0002] In the field of analytical specimen preparation, thinning specimens to obtain ultrathin cross-sections suitable for transmission electron microscopy (TEM), scanning electron microscopy (SEM), or focused ion beam (FIB) analysis is a major technical approach for acquiring information about the internal structure of materials. Currently, the industry mainly uses two methods for specimen thinning preparation: manual grinding and laser processing.

[0003] Laser processing, as an advanced material micromachining technique, allows for selective thinning of specific areas of a sample through precise focusing of a high-energy laser beam. It is particularly suitable for detailed analysis requiring only localized thinning. This technology offers advantages such as non-contact processing, high positioning accuracy, and high processing efficiency, making it an indispensable tool in modern materials analysis laboratories. However, significant technical bottlenecks exist in laser processing, severely limiting its application in precision failure analysis.

[0004] First, the material ejection phenomenon during laser processing severely affects the surface integrity of the sample. When a high-energy laser beam bombards the sample surface, the ejected material particles (i.e., debris) gain high-speed motion due to photon kinetic energy transfer and are ejected outward along a parabolic trajectory. Based on the physical relationship between the laser incident angle and the kinetic energy gained by the debris, a significant proportion of the debris will re-enter the sample surface, and the incident positions are randomly distributed, scattered in the outer edge of the laser preparation area. These high-energy debris not only remain on the sample surface but also penetrate further into the sample to a certain depth, causing mechanical damage and material destruction to the original sample surface structure, such as… Figure 3 As shown. This secondary damage effect leads to unexpected microstructural variations on the surface of the specimen, making it impossible to obtain truly reliable raw data for subsequent material / fault analysis. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for protecting test pieces from damage caused by laser bombardment.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for protecting test pieces from damage caused by laser bombardment, the specific steps of which are as follows: S1: Marked area; Prepare a sample that needs to be protected, and designate a region in the sample as the laser thinning area, where the laser thinning area is smaller than the sample size; S2: Coated test piece; A hydrophobic polymer layer is prepared on the surface of the sample by coating, with a thickness of 1000-1500 nm; the hydrophobic polymer can be polyethylene. S3: Preparation of alumina surface layer; The sample coated with a layer of hydrophobic polymer in step S2 is placed in the ALD device to prepare an alumina surface layer on the surface of the hydrophobic polymer. S4: Preparation of CVD platinum layer; A CVD platinum layer is prepared on the surface of the sample with hydrophobic polymer layer + ALD alumina surface layer in step S3. S5: Laser Bombardment; The sample coated with a hydrophobic polymer layer, an ALD alumina surface layer, and a CVD platinum layer was placed under a laser device and bombarded in a specific area to obtain a special sample. S6: Organic solvent cleaning; The special sample obtained in step S5 is placed in an organic solution for surface cleaning. The hydrophobic polymer layer, ALD alumina surface layer, and CVD platinum layer on the special sample are cleaned away by the organic solution to obtain the final sample.

[0007] Preferably, in step S1, the thickness of the laser-thinned region is less than the thickness of the sample.

[0008] Preferably, in step S2, the hydrophobic polymer also includes polystyrene, polyester, and polyurethane.

[0009] Preferably, in step S3, the preparation process of coating the hydrophobic polymer layer is as follows: S3-1: Place the hydrophobic polymer on a stirrer with heating function and heat it to 50-60 degrees Celsius to improve its fluidity; S3-2: Coat the surface of the test piece with a fluid hydrophobic polymer; S3-3: Let the coated sample stand at room temperature for 10-15 minutes to complete the coating preparation.

[0010] Preferably, in step S6, the organic solvent is methanol, ethanol, isopropanol, or acetone.

[0011] Preferably, in step S4, the CVD platinum layer is prepared as follows: S4-1: VTIP is introduced into the CVD chamber and mixed with the carrier gas, so that VTIP is adsorbed layer by layer on the surface of ALD alumina. S4-2: VTIP undergoes a chemical reaction on the surface of ALD aluminum oxide to form a platinum film; S4-3: After the platinum film is adsorbed to the specified thickness, a CVD platinum layer is formed.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: through the design of a multi-layer composite protective structure, the problem of surface damage to the test piece caused by material blasting and thermal effects in traditional laser processing is effectively solved, and the accuracy and reliability of laser thinning preparation are significantly improved.

[0013] First, this invention employs a three-layer composite protective structure consisting of a hydrophobic polymer layer, an alumina surface layer, and a CVD platinum layer. Utilizing the low surface energy of hydrophobic polymers (such as polyethylene), it effectively reduces the adhesion and intrusion of material residues during laser bombardment. The alumina surface layer provides a high melting point and high thermal conductivity, rapidly dispersing localized heat generated by the laser and preventing thermal deformation of heat-sensitive materials. The CVD platinum layer exhibits high reflectivity and high corrosion resistance, significantly reducing the direct impact of laser energy on the sample. This triple protective effect fundamentally solves the problem of surface structure damage caused by laser processing.

[0014] Secondly, this invention prepares an alumina surface layer using precisely controlled ALD atomic layer deposition technology, achieving nanoscale thickness uniformity and density control. Combined with the excellent barrier performance of the CVD platinum layer, a highly efficient "interception net" is formed, which can effectively block more than 90% of material debris from secondary incidence, preventing debris from intruding into the interior of the specimen and causing hidden damage. This ensures the integrity of the original structure of the specimen surface and significantly improves the accuracy of subsequent material / fault analysis.

[0015] Furthermore, the present invention employs a post-processing technique that selectively removes the protective layer with an organic solution, achieving non-destructive separation between the protective layer and the substrate, thus avoiding new damage that may be introduced by traditional mechanical peeling. Attached Figure Description

[0016] Figure 1 Top view of the sample debris splashed onto the laser area; Figure 2 A frontal view of the sample debris splashed onto the laser area; Figure 3 A schematic diagram showing the test piece covered with three different surface layers. Detailed Implementation

[0017] To provide a further understanding of the purpose, structure, features, and functions of the present invention, detailed descriptions are provided below with reference to specific embodiments.

[0018] Please refer to the reference. Figure 1 The present invention provides a method for protecting test pieces from damage caused by laser bombardment.

[0019] To achieve the above objectives, the present invention adopts the following technical solution: a method for protecting test pieces from damage caused by laser bombardment, the specific steps of which are as follows: S1: Marked area; Prepare a sample that needs to be protected, and designate a region within the sample as the laser thinning area, where the laser thinning area is smaller than the sample size.

[0020] S2: Coated test piece; A hydrophobic polymer layer is prepared on the surface of the sample by coating, with a thickness of 1000-1500 nm; the hydrophobic polymer can be polyethylene.

[0021] Hydrophobic polymers also include polystyrene, polyester, and polyurethane.

[0022] The main reason for using hydrophobic polymers is that they are soluble in organic solvents.

[0023] S3: Preparation of alumina surface layer; The sample coated with a layer of hydrophobic polymer in step S2 is placed in the ALD device to prepare an alumina surface layer on the surface of the hydrophobic polymer.

[0024] The thickness of the alumina surface layer is 1-2 nm.

[0025] Alumina (ALD) is highly reactive and readily combines with different materials to form strong bonds, making it suitable for connecting two different materials.

[0026] S4: Preparation of CVD platinum layer; A CVD platinum layer is prepared on the surface of the sample containing the hydrophobic polymer layer + ALD alumina surface layer in step S3. The precursor chemical used in this invention is Vanadium(V) oxytriisopropoxide (VTIP), with the chemical formula OV(OCH(CH3)2)3. The preparation process of the CVD platinum layer is as follows: S4-1: VTIP is introduced into the CVD chamber and mixed with the carrier gas, so that VTIP is adsorbed layer by layer on the surface of ALD alumina. S4-2: VTIP undergoes a chemical reaction on the surface of ALD aluminum oxide to form a platinum film; S4-3: After the platinum film is adsorbed to the specified thickness, a CVD platinum layer is formed.

[0027] The CVD platinum layer has a dense structure and good thermal conductivity. It is also connected to the hydrophobic polymer layer by an ALD alumina layer, which allows it to adhere firmly to the surface of the sample.

[0028] S5: Laser Bombardment; The sample coated with a hydrophobic polymer layer, an ALD alumina surface layer, and a CVD platinum layer was placed under a laser device and bombarded in a specific area to obtain a special sample. S6: Organic solvent cleaning; The special sample obtained in step S5 is placed in an organic solution for surface cleaning. The hydrophobic polymer layer, ALD alumina surface layer, and CVD platinum layer on the special sample are cleaned away by the organic solution to obtain the final sample.

[0029] Specific implementation: This invention utilizes a hydrophobic polymer film as a protective layer on the surface of the test piece to protect the surface structure of the surrounding area from debris generated during the laser's localized thinning of the test piece. A relatively dense platinum layer is then prepared on the protective layer as a thermally conductive layer to effectively guide the heat generated by the laser preparation away from the target area, thus protecting the test piece structure. In addition, a bonding layer is introduced between the protective layer and the thermally conductive layer to ensure that the two layers adhere completely and are firmly bonded together.

[0030] The present invention has been described in the above-described embodiments; however, these embodiments are merely examples for implementing the present invention. It must be noted that the disclosed embodiments do not limit the scope of the present invention. Conversely, any modifications and refinements made without departing from the spirit and scope of the present invention are within the scope of patent protection of the present invention.

Claims

1. A method for protecting a test piece from damage caused by laser bombardment, characterized in that: The specific steps of the method are as follows: S1: Marked area; Prepare a sample that needs to be protected, and designate a region in the sample as the laser thinning area, where the laser thinning area is smaller than the sample size; S2: Coated test piece; A hydrophobic polymer layer is prepared on the surface of the sample by coating, with a thickness of 1000-1500 nm; the hydrophobic polymer can be polyethylene. S3: Preparation of alumina surface layer; The sample coated with a layer of hydrophobic polymer in step S2 is placed in the ALD device to prepare an alumina surface layer on the surface of the hydrophobic polymer. S4: Preparation of CVD platinum layer; A CVD platinum layer is prepared on the surface of the sample with hydrophobic polymer layer + ALD alumina surface layer in step S3. S5: Laser Bombardment; The sample coated with a hydrophobic polymer layer, an ALD alumina surface layer, and a CVD platinum layer was placed under a laser device and bombarded in a specific area to obtain a special sample. S6: Organic solvent cleaning; The special sample obtained in step S5 is placed in an organic solution for surface cleaning. The hydrophobic polymer layer, ALD alumina surface layer, and CVD platinum layer on the special sample are cleaned away by the organic solution to obtain the final sample.

2. The method for protecting a test piece from damage caused by laser bombardment as described in claim 1, characterized in that: In step S1, the thickness of the laser thinning region is less than the thickness of the test piece.

3. The method for protecting a test piece from damage caused by laser bombardment as described in claim 1, characterized in that: In step S2, the hydrophobic polymers also include polystyrene, polyester, and polyurethane.

4. The method for protecting a test piece from damage caused by laser bombardment as described in claim 1, characterized in that: In step S3, the preparation process of coating the hydrophobic polymer layer is as follows: S3-1: Place the hydrophobic polymer on a stirrer with heating function and heat it to 50-60 degrees Celsius to improve its fluidity; S3-2: Coat the surface of the test piece with a fluid hydrophobic polymer; S3-3: Let the coated sample stand at room temperature for 10-15 minutes to complete the coating preparation.

5. The method for protecting a test piece from damage caused by laser bombardment as described in claim 1, characterized in that: In step S6, the organic solvent is methanol, ethanol, isopropanol, or acetone.

6. The method for protecting a test piece from damage caused by laser bombardment as described in claim 1, characterized in that: In step S4, the preparation process of the CVD platinum layer is as follows: S4-1: VTIP is introduced into the CVD chamber and mixed with the carrier gas, so that VTIP is adsorbed layer by layer on the surface of ALD alumina. S4-2: VTIP undergoes a chemical reaction on the surface of ALD aluminum oxide to form a platinum film; S4-3: After the platinum film is adsorbed to the specified thickness, a CVD platinum layer is formed.

Images