A PtW / Pt composite material strain film and preparation method thereof

Abstract

A PtW / Pt composite strain film and its preparation method belong to the field of thin film sensor design and production technology. The strain film comprises a PtW layer and a Pt layer; wherein the PtW layer has a thickness of 30 to 100 nm, the Pt layer has a thickness of 300 to 2000 nm, and the thickness ratio of the PtW layer to the Pt layer is 1:(10 to 20). The mass percentage of W in the PtW layer is 6 to 8%. The present invention utilizes a PtW and Pt double-layer thin film structure. The PtW layer enhances the adhesion of Pt to the oxide insulating layer, inhibits high-temperature aggregation of Pt, maintains the integrity and uniformity of the Pt film, and maintains the strain sensitivity coefficient and high-temperature stability of the Pt film, enabling accurate strain measurement at 1000°C. Simultaneously, the thickness ratio of the PtW layer to the Pt layer, as well as the W content in the PtW layer, is strictly controlled to optimize the high-temperature performance of the film and ensure accurate strain measurement at high temperatures.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film sensor design and production, and in particular relates to a PtW / Pt composite material strain film and a preparation method thereof. Background Art

[0002] As a core component of the aerospace industry, aircraft engines hold a crucial position in the field. Operating in harsh environments for extended periods, aircraft engines are susceptible to failures such as fractures due to uneven internal stress distribution. Therefore, real-time monitoring of the stress levels within the engine's main internal structures is crucial to prevent cracking and other potential engine failures caused by excessive stress.

[0003] The devices used in stress monitoring are mainly resistance strain gauges. The strain gauges attached to the surface of the object being measured will deform accordingly with the deformation of the object being measured, and the resistance will change accordingly. The magnitude of the strain can be measured by testing the resistance. Resistance strain gauges mainly include the following three types: foil resistance strain gauges, wire resistance strain gauges, and thin film resistance strain gauges. Among them, thin film strain gauges can be directly made on the surface of the object being measured. The strain gauges made in this way do not need to be pasted with adhesives, which can avoid the influence of adhesives on test results and the restrictions on test conditions, and do not damage the structure of the object being measured. At the same time, thin film resistance strain gauges have the characteristics of small size, fast response speed, high sensitivity, stable performance, and long service life, which can meet the working requirements in harsh environments. Therefore, thin film strain gauges are widely used in aerospace component monitoring.

[0004] In thin-film strain gauges, the strain layer is crucial, and the choice of material determines its performance. Existing strain layer materials primarily include PdCr and NiCr. However, no known material can stably operate thin-film strain gauges at 1000°C. Therefore, research into new materials for strain-resistant thin films is needed to enable stable operation at higher temperatures. Research has revealed that both PtW and Pt, as metallic materials, possess strong high-temperature resistance. PtW alloys exhibit high strain sensitivity at room temperature (PtW8 (92 / 8 wt.%) alloy has a strain sensitivity of 4 at room temperature). However, this sensitivity decays rapidly with increasing temperature, rendering them inoperable at 1000°C. Pt metal, while exhibiting a high strain sensitivity at high temperatures (3.88 at 600°C), agglomerates above 800°C, rendering it inoperable. Therefore, to enable strain-resistant thin films to operate at 1000°C, a composite material must be designed that maintains high strain sensitivity while maintaining high-temperature stability. Summary of the Invention

[0005] The present invention aims to address the problems of the prior art and propose a PtW / Pt composite strain film and its preparation method. The PtW / Pt composite strain film of the present invention can accurately measure strain at 1000°C and has good high-temperature stability.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A PtW / Pt composite material strain film, comprising a PtW layer and a Pt layer formed on the PtW layer; wherein the PtW layer has a thickness of 30 to 100 nm, the Pt layer has a thickness of 300 to 2000 nm, and the thickness ratio of the PtW layer to the Pt layer is 1:(10 to 20); and the mass percentage of W in the PtW layer is 6 to 8%.

[0008] A method for preparing a PtW / Pt composite material strain film comprises the following steps:

[0009] Step 1: Surface treatment of substrate:

[0010] The ceramic substrate was cleaned by ultrasonic cleaning in acetone, anhydrous ethanol, and deionized water in sequence, and the substrate was dried using a nitrogen gun after cleaning;

[0011] Step 2: Preparation of strained film:

[0012] The strained film is deposited on the substrate treated in step 1 by magnetron sputtering, and then the film is patterned using a hard mask. The specific process is as follows: under a backside vacuum of 5×10 -5 Under the conditions of Pa, a PtW layer with a thickness of 30 to 100 nm is first sputtered using a PtW target material with a purity of 99.99%, and then a Pt layer with a thickness of 300 to 2000 nm is sputtered using a Pt target material with a purity of 99.99%; the mass percentage of W in the PtW target material is 6 to 8 wt%;

[0013] Step 3: Aging treatment of the strain film:

[0014] Since the straining is carried out in an atmospheric environment at 1000°C, the strained film needs to be aged in advance to eliminate structural defects and optimize and stabilize device performance. The strained film prepared in step 2 is annealed in an atmospheric environment at a temperature of 1000°C for 1 hour.

[0015] The present invention provides a PtW / Pt composite material strain film, which adopts a PtW and Pt double-layer film structure, and strictly controls the thickness ratio of the PtW layer to the Pt layer, as well as the W content in the PtW layer. The thickness of the PtW layer is 30 to 100 nm, and the thickness of the Pt layer is 300 nm to 2000 nm. The thickness ratio of the PtW layer to the Pt layer is 1:(10 to 20). Setting the PtW layer thickness to above 30 nm can form a continuous film, improve the adhesion of the Pt layer grown on it, and alleviate the phenomenon of Pt agglomeration at high temperatures. The Pt layer thickness is controlled within 2000 nm to facilitate the control of the resistance value of the strain film to a moderate value. Due to the extremely large temperature coefficient of resistance of the Pt material, if the resistance of the strain film is very small, the resistance change caused by strain will also decrease. The resistance change caused by temperature under high temperature conditions will cover the resistance change caused by strain, making it impossible to measure strain. Therefore, the film resistance value has a crucial influence on strain measurement. The thickness of the PtW layer needs to be smaller than the thickness of the Pt layer so that the overall sensitivity factor of the strain film is more affected by the Pt layer, thereby maintaining high-temperature stability and accurate testing under high temperatures. The W content in the PtW layer is strictly controlled at 6-8%. The low W content, primarily composed of Pt, ensures that the PtW layer shares a similar structure with the overlying Pt layer, resulting in excellent adhesion of the Pt grown on the PtW. Furthermore, W readily forms tungsten oxide during the sputtering process, which forms a strong interfacial bond with the substrate, effectively enhancing the adhesion of the PtW layer to the insulating layer. This in turn inhibits high-temperature Pt aggregation, maintaining the integrity and uniformity of the Pt layer. This ensures a high strain sensitivity coefficient and high-temperature stability for the overlying Pt film, enabling accurate strain measurement at 1000°C.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention provides a PtW / Pt composite material strain film. After high-temperature testing at 1000°C, the Pt film has an intact appearance and does not experience shedding or agglomeration. This indicates that the PtW / Pt composite film structure of the present invention effectively improves the adhesion of Pt and prevents Pt agglomeration at high temperatures, allowing the Pt film to maintain integrity and uniformity at high temperatures. This ensures that the Pt film has a large strain sensitivity coefficient at room temperature and a strain sensitivity coefficient at 1000°C, achieving accurate measurement of strain from room temperature to 1000°C.

[0018] 2. The present invention provides a PtW / Pt composite strain film, which adopts a double-layer film structure of PtW and Pt. The PtW layer can enhance the adhesion of Pt on the oxide insulating layer, inhibit high-temperature agglomeration of Pt, maintain the integrity and uniformity of the Pt film, and keep the strain sensitivity coefficient and high-temperature stability of the upper Pt film, thereby realizing accurate measurement of strain at 1000°C. At the same time, the thickness ratio of the PtW layer and the Pt layer, as well as the W content in the PtW layer, are strictly controlled to optimize the high-temperature performance of the film and ensure accurate measurement of strain of the film at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 These are the curves showing the change in resistance of the PtW / Pt composite material strain film obtained in the example with strain at different temperatures; where (a) is room temperature, (b) is 200°C, (c) is 400°C, (d) is 600°C, (e) is 800°C, and (f) is 1000°C. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0021] Example

[0022] To test the high-temperature strain performance of the PtW / Pt composite strain film of the present invention, the strain film was fabricated on a high-temperature resistant ceramic substrate. The specific process is as follows:

[0023] Step 1: ultrasonically clean the ceramic substrate in acetone, anhydrous ethanol, and deionized water for 5 minutes in sequence, and then dry the substrate with a nitrogen gun;

[0024] Step 2: Deposit a PtW film on the substrate treated in step 1 by magnetron sputtering, and then pattern it using a hard mask. The specific process is as follows: -5 Under the conditions of 1.5 wt. Pa, a PtW8 (92 / 8 wt.%) target with a purity of 99.99% was used to sputter a PtW layer with a thickness of 65 nm. The sputtering pressure was 0.77 Pa, the sputtering power was 70 W, the sputtering atmosphere was argon, and the argon flow rate was 20 sccm.

[0025] Step 3: deposit a Pt film on the PtW film using magnetron sputtering, and then pattern the film using a hard mask. The specific process is as follows: -5 Under the conditions of Pa, a Pt target with a purity of 99.99% was used to sputter a Pt layer with a thickness of 700 nm. The sputtering pressure was 0.77 Pa, the sputtering power was 80 W, the sputtering atmosphere was argon, and the argon flow rate was 20 sccm.

[0026] Step 4: annealing the strained film obtained in step 3 in an atmospheric environment at an annealing temperature of 1000° C., an annealing time of 1 h, and a heating rate of 5° C. / min. After annealing, the film is cooled to room temperature at a cooling rate of 5° C. / min.

[0027] The strain film after annealing in step 4 is subjected to a high-temperature strain test, and a high-temperature platinum paste is used to connect the leads, and the leads are made of platinum wire. The strain test uses a cantilever beam method, fixes one end of the sample, and applies strain at the other end to deform the substrate, and the film deforms accordingly and produces a change in resistance. The strain is tested by testing the change in resistance. The high-temperature strain test requires placing the cantilever beam in a high-temperature furnace, selecting different temperature points, and adjusting the cantilever beam to gradually increase the strain after the temperature stabilizes. In the embodiment, 6 different temperature points within the range of room temperature-1000°C are selected, namely room temperature, 200°C, 400°C, 600°C, 800°C, and 1000°C. After the temperature of each temperature point stabilizes, 7 points are selected at equal intervals within the range of 0-400 microstrain, and 50 points are continuously tested at each strain point. The arithmetic mean is taken as the resistance value of the film at that temperature and strain. The test results are as follows. Figure 1 From the test results, it can be found that the PtW / Pt composite strain film can detect the change of strain well at different temperatures, and the strain sensitivity coefficient gradually decreases with increasing temperature. The device can work stably in an environment of 1000℃, and the strain sensitivity coefficient at 1000℃ is 2.0.

[0028] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A PtW / Pt composite strain film, characterized in that: The strained film includes a PtW layer and a Pt layer formed on the PtW layer; wherein the thickness of the PtW layer is 30 to 100 nm, the thickness of the Pt layer is 300 nm to 2000 nm, and the thickness ratio of the PtW layer to the Pt layer is 1:(10 to 20); the mass percentage of W in the PtW layer is 6 to 8%.

2. A method for preparing a PtW / Pt composite strain film, characterized in that: The following steps are involved: Step 1: Surface treatment of substrate: Clean and dry the substrate; Step 2: Preparation of strained film: The strained film was deposited on the substrate treated in step 1 by magnetron sputtering and then patterned. The specific process was as follows: -5 Under the conditions of Pa, a PtW target is first used to sputter a PtW layer with a thickness of 30 to 100 nm, and then a Pt target is used to sputter a Pt layer with a thickness of 300 to 2000 nm; the mass percentage of W in the PtW target is 6 to 8 wt%; Step 3: Aging treatment of the strain film: The strained film obtained in step 2 is annealed in an atmospheric environment at an annealing temperature of 1000° C. and an annealing time of 1 h.

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