Stress sensor material

Abstract

Provided is a stress sensor material advantageous for a high gauge factor and low power consumption in a stress sensor. The stress sensor material contains, in atomic%, 0.1-50% of Ge, 10-99% of Te, and 5% or less of As.

Description

Stress Sensor Materials

[0001] The present invention relates to a stress sensor.

[0002] There is a demand for higher performance and smaller size of sensors that detect stress (stress sensors), and the development of stress sensor materials with higher performance is required. For example, the gauge factor is known as an index that determines the detection sensitivity of a stress sensor, and stress sensor materials with higher gauge factors are required. Known stress sensor materials include metal materials and semiconductor materials. However, many metal materials have a small gauge factor of about 2. Furthermore, although semiconductor materials such as Si and Ge exhibit a relatively large gauge factor compared to metal materials, it is difficult to further improve the gauge factor, and there are problems such as large fluctuations in characteristics due to anisotropy (Patent Documents 1 and 2).

[0003] JP2019-204874A JP10-270201A

[0004] In recent years, there has been a demand for stress sensors that not only have improved detection sensitivity but also have low power consumption.

[0005] In view of the above, an object of the present invention is to provide a stress sensor material that has a high gauge factor and is advantageous for reducing the power consumption of the stress sensor.

[0006] An embodiment of a stress sensor material that solves the above problems will be described.

[0007] The stress sensor material of aspect 1 is characterized by containing, in atomic percent, 0.1% to 50% of Ge, 10% to 99% of Te, and 5% or less of As.

[0008] The stress sensor material of the second embodiment is preferably the same as that of the first embodiment, and contains, in atomic percent, 0.1% to 89.9% of Mn+Cu+W+Sn+Bi.

[0009] The stress sensor material of aspect 3 is characterized by containing, in atomic percent, 10% to 99% of Te, 5% or less of As, and 0.1% to 50% of Si.

[0010] In the stress sensor material of the fourth aspect, in the third aspect, the atomic ratio of Ge / Te is preferably 0.5 or less.

[0011] The stress sensor material of aspect 5 is characterized by containing, in atomic percent, 10% to 99% of Te, 5% or less of As, and 0.1% to 90% of Mn+Cu+W+C+Al+In+Sn+Bi.

[0012] In the stress sensor material of the sixth aspect, in the third aspect, it is preferable that the atomic ratio of Ge / Te is 0.5 or less.

[0013] The stress sensor material of Aspect 7 is any one of Aspects 1 to 6, and preferably has a gauge factor of 3 or more at a strain of 0.1%.

[0014] The stress sensor material of Aspect 8 is any one of Aspects 1 to 7, wherein the electrical resistivity at 25±2° C. is 1.0×10 ５ It is preferably Ωcm or less.

[0015] The stress sensor material of Aspect 9 is preferably a thin film in any one of Aspects 1 to 8.

[0016] According to the present invention, it is possible to provide a stress sensor material that has a high gauge factor and is advantageous for reducing the power consumption of the stress sensor.

[0017] 1 and 2 are a schematic cross-sectional view and a schematic top view of the stress sensor, respectively.

[0018] Preferred embodiments will be described below, but the following embodiments are merely examples and the present invention is not limited to the following embodiments.

[0019] (Stress Sensor Material A) In one embodiment, the stress sensor material of the present invention is characterized by containing, in atomic percent, 0.1% to 50% Ge, 10% to 99% Te, and 5% or less As. The reasons for specifying the composition as described above and the content of each component are explained below. In the following explanation, "%" means "atomic percent" unless otherwise specified. In addition, in the present invention, "x + y + z + ..." means the total content of each component. Here, each component does not necessarily have to be contained as an essential component, and it is acceptable for there to be components that are not contained (content 0%). Furthermore, "x + y + z + ... A% to B%" includes, for example, cases such as "x = 0%, y + z + ... A% to B%" and "x = 0%, y = 0%, z + ... A% to B%."

[0020] Ge is a component that increases the gauge factor of the stress sensor material. The Ge content is preferably 0.1% to 50%. More specifically, the lower limit of the Ge content is preferably 0.1% or more, 0.2% or more, 0.5% or more, 1% or more, and particularly 2% or more, and the upper limit of the Ge content is preferably 50% or less, 49% or less, particularly 45% or less, 40% or less, less than 40%, 35% or less, and particularly 30% or less. If the Ge content is too low, the gauge factor tends to be small. If the Ge content is too high, the electrical resistivity increases, making it difficult to detect changes in the electrical resistance or current of the stress sensor due to strain, and a high-resolution electrical resistance or current measuring device is required. Furthermore, the need for an amplifier circuit tends to increase the power consumption of the stress sensor. In addition to the above, manufacturing costs tend to increase.

[0021] Te is a component constituting the stress sensor material. The Te content is preferably 10% to 99%. More specifically, the lower limit of the Te content is preferably 10% or more, 12% or more, 15% or more, and particularly preferably 20% or more, and the upper limit of the Te content is preferably 99% or less, 98% or less, 97% or less, 95% or less, 94% or less, 90% or less, or less than 90%, and particularly preferably 88% or less. If the Te content is too low, the amorphous state tends to become unstable. If the Te content is too high, the amorphous state tends to become unstable.

[0022] From the viewpoint of stabilizing the amorphous state of the stress sensor material, the lower limit of the Ge+Te content (total amount of Ge and Te) is preferably 10.1% or more, 20% or more, and particularly 30% or more. Also, from the viewpoint of reducing the electrical resistivity, the upper limit of the Ge+Te content is preferably 100% or less, and particularly 99.9% or less.

[0023] As is a component that easily stabilizes the amorphous state of the stress sensor material. However, because As is a toxic component, from the perspective of reducing the burden on the environment, it is preferable that the As content be 5% or less, less than 5%, 4.9% or less, 4.5% or less, 3% or less, 1% or less, and particularly that it be substantially free of As. In this specification, "substantially free of As" means that it is not intentionally included in the raw materials, and does not exclude contamination at the impurity level. Objectively, it refers to a content of each component being less than 0.1%.

[0024] Mn, Cu, W, Sn, and Bi increase the gauge factor of the stress sensor material and reduce its electrical resistivity, thereby facilitating detection of strain-induced changes in electrical resistance or current of the stress sensor, and are effective components in reducing the power consumption of the stress sensor. The content of Mn+Cu+W+Sn+Bi (the total amount of Mn, Cu, W, Sn, and Bi) is preferably 0% to 89.9%, and particularly preferably 0.1% to 89.9%. More specifically, the lower limit of the content of Mn+Cu+W+Sn+Bi is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more. The upper limit of the content of Mn+Cu+W+Sn+Bi is preferably 89.9% or less, less than 89.9%, 80% or less, 75% or less, 70% or less, and particularly preferably 65% ​​or less. If the content of these components is too high, the amorphous state tends to become unstable. The preferred contents of each of Mn, Cu, W, Sn and Bi are as follows:

[0025] The Mn content is preferably 0% to 89.9%. More specifically, the lower limit of the Mn content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the Mn content is preferably 89.9% or less, less than 89.9%, 80% or less, 75% or less, 70% or less, and particularly preferably 65% ​​or less.

[0026] The Cu content is preferably 0% to 89.9%. More specifically, the lower limit of the Cu content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the Cu content is preferably 89.9% or less, less than 89.9%, 80% or less, 75% or less, 70% or less, and particularly preferably 65% ​​or less.

[0027] The W content is preferably 0% to 89.9%. More specifically, the lower limit of the W content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the W content is preferably 89.9% or less, less than 89.9%, 80% or less, 75% or less, 70% or less, and particularly preferably 65% ​​or less.

[0028] The Sn content is preferably 0% to 89.9%. More specifically, the lower limit of the Sn content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the Sn content is preferably 89.9% or less, less than 89.9%, 80% or less, 75% or less, 70% or less, and particularly preferably 65% ​​or less.

[0029] The Bi content is preferably 0% to 89.9%. More specifically, the lower limit of the Bi content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the Bi content is preferably 89.9% or less, less than 89.9%, 80% or less, 75% or less, 70% or less, and particularly preferably 65% ​​or less.

[0030] Among the above components, W and Bi have a significant effect of reducing electrical resistivity. Therefore, from the viewpoint of particularly reducing electrical resistivity, the lower limit of the W+Bi content (total amount of W and Bi) is preferably 0% or more, 0.1% or more, 1% or more, and particularly 3% or more. From the viewpoint of stabilizing the amorphous state, the upper limit of the W+Bi content is preferably 89.9% or less, less than 89.9%, 80% or less, 70% or less, and particularly 65% ​​or less.

[0031] Among the above components, Mn, Cu, and W have a significant effect of reducing electrical resistivity. Therefore, from the viewpoint of particularly reducing electrical resistivity, the lower limit of the content of Mn+Cu+W (total amount of Mn, Cu, and W) is preferably 0% or more, 0.1% or more, 1% or more, and particularly preferably 3% or more. From the viewpoint of stabilizing the amorphous state, the upper limit of the content of Mn+Cu+W is preferably 89.9% or less, less than 89.9%, 80% or less, 70% or less, and particularly preferably 65% ​​or less.

[0032] Al and Si are components that increase the gauge factor of the stress sensor material. The Al+Si content (total amount of Al and Si) is preferably 0% to 89.9%. More specifically, the lower limit of the Al+Si content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly 0.5% or more, and the upper limit of the Al+Si content is preferably 89.9% or less, less than 89.9%, 80% or less, 75% or less, 70% or less, and particularly 65% ​​or less. If the content of these components is too high, the amorphous state tends to become unstable. Furthermore, the electrical resistivity tends to increase. The preferred contents of each of the Al and Si components are as follows:

[0033] The Al content is preferably 0% to 89.9%. More specifically, the lower limit of the Al content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the Al content is preferably 89.9% or less, less than 89.9%, 80% or less, 75% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, and particularly preferably 20% or less.

[0034] The Si content is preferably 0% to 89.9%. More specifically, the lower limit of the Si content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the Si content is preferably 89.9% or less, 80% or less, 75% or less, 70% or less, 60% or less, 50% or less, 40% or less, and particularly preferably 30% or less.

[0035] From the viewpoint of particularly reducing the electrical resistivity of the stress sensor material, the upper limit of the content of Ge+Te+Al+Si (the total amount of Ge, Te, Al, and Si) is preferably 100% or less, particularly 99.9% or less. The lower limit of the content of Ge+Te+Al+Si is not particularly limited, but is preferably, for example, 10.1% or more, 20% or more, particularly 30% or more.

[0036] Other components may include, for example, at least one selected from V, Nb, and Mo. The V+Nb+Mo content (total amount of V, Nb, and Mo) is preferably 0% to 89.9%. More specifically, the upper limit of the V+Nb+Mo content is preferably 89.9% or less, less than 89.9%, 80% or less, 70% or less, 65% or less, 50% or less, and particularly 30% or less. The lower limit of the V+Nb+Mo content may be 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly 0.5% or more. If the content of these components is too high, the amorphous state tends to become unstable. The preferred contents of each of the V, Nb, and Mo components are as follows:

[0037] The V content is preferably 0% to 89.9%. More specifically, the upper limit of the V content is preferably 89.9% or less, less than 89.9%, 80% or less, 70% or less, 65% or less, 50% or less, and particularly preferably 30% or less. The lower limit of the V content may be 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more.

[0038] The Nb content is preferably 0% to 89.9%. More specifically, the upper limit of the Nb content is preferably 89.9% or less, less than 89.9%, 80% or less, 70% or less, 65% or less, 50% or less, and particularly preferably 30% or less. The lower limit of the Nb content may be 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more.

[0039] The Mo content is preferably 0% to 89.9%. More specifically, the upper limit of the Mo content is preferably 89.9% or less, less than 89.9%, 80% or less, 70% or less, 65% or less, 50% or less, and particularly preferably 30% or less. The lower limit of the Mo content may be 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more.

[0040] For example, the stress sensor material of this embodiment preferably contains, in atomic percent, 0.1% to 50% Ge, 20% to 90% Te, and 5% or less As. It also preferably contains, in atomic percent, 0.1% to 50% Ge, 20% to 90% Te, 5% or less As, and 0.1% to 75% Mn+Cu+W+Sn+Bi. It also preferably contains, in atomic percent, 0.1% to 50% Ge, 20% to 90% Te, 5% or less As, and 0.1% to 75% Al+Si.

[0041] (Stress Sensor Material B) In one embodiment, the stress sensor material of the present invention is characterized by containing, in atomic percent, 10% to 99% Te, 5% or less As, and 0.1% to 90% Si. The reasons for specifying the composition as described above and the content of each component are explained below. Note that in the description of this embodiment, descriptions of components that overlap with those of stress sensor material A may be omitted. Furthermore, components not described in the description of this embodiment may adopt the preferred configurations described in the description of stress sensor material A.

[0042] In this embodiment, Te is a component constituting the stress sensor material. The Te content is preferably 10% to 99%. More specifically, the lower limit of the Te content is preferably 10% or more, 12% or more, 15% or more, and particularly 20% or more, and the upper limit of the Te content is preferably 99% or less, 98% or less, 97% or less, 95% or less, 94% or less, 90% or less, or less than 90%, and particularly 88% or less. If the Te content is too low, the amorphous state tends to become unstable. If the Te content is too high, the amorphous state tends to become unstable.

[0043] In this embodiment, As is a component that easily stabilizes the amorphous state of the stress sensor material. However, since As is a toxic component, from the viewpoint of reducing the burden on the environment, it is preferable that the As content be 5% or less, less than 5%, 4.9% or less, 4.5% or less, 3% or less, 1% or less, and particularly that As is substantially absent.

[0044] In this embodiment, Si is a component that particularly tends to increase the gauge factor of the stress sensor material. The Si content is particularly preferably 0.1% to 90%. More specifically, the lower limit of the Si content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.7% or more, 0.8% or more, and particularly preferably 1% or more, and the upper limit of the Si content is preferably 90% or less, 80% or less, 70% or less, 65% or less, 60% or less, 55% or less, 50% or less, 40% or less, and particularly preferably 30% or less. If the content of these components is too high, the electrical resistivity tends to be high.

[0045] In this embodiment, particularly from the viewpoint of reducing electrical resistivity, the Ge content is preferably 0% to 5%. More specifically, the upper limit of the Ge content is preferably 5% or less, 2% or less, 1% or less, or 0.1% or less, and it is particularly preferable that Ge is substantially not contained.

[0046] In this embodiment, the atomic ratio Ge / Te is preferably 0.5 or less, 0.2 or less, 0.1 or less, and particularly preferably less than 0.03. A stress sensor material that satisfies the above atomic ratio is likely to achieve both a high gauge factor and low electrical resistivity. The lower limit of the atomic ratio Ge / Te is not particularly limited, but may be, for example, 0 or more, particularly 0.0001 or more.

[0047] For example, the stress sensor material of this embodiment preferably contains, in atomic %, 10% to 99% Te, 5% or less As, 0.1% to 90% Si, and 0% to 5% Ge, more preferably 20% to 99% Te, 5% or less As, 0.1% to 30% Si, and 0% to 2% Ge, and particularly preferably 20% to 99% Te, 5% or less As, 0.1% to 30% Si, and substantially no Ge.

[0048] (Stress Sensor Material C) In one embodiment, the stress sensor material of the present invention is characterized by containing, in atomic percent, 10% to 99% Te, 5% or less As, and 0.1% to 90% Mn+Cu+W+C+Al+In+Sn+Bi. The reasons for specifying the composition as above and the content of each component are explained below. Note that in the description of this embodiment, descriptions of components that overlap with stress sensor material A or B may be omitted. Furthermore, components not described in the description of this embodiment may adopt the preferred configurations described in the description of stress sensor material A or B.

[0049] In this embodiment, Te is a component constituting the stress sensor material. The Te content is preferably 10% to 99%. More specifically, the lower limit of the Te content is preferably 10% or more, 12% or more, 15% or more, and particularly 20% or more, and the upper limit of the Te content is preferably 99% or less, 98% or less, 97% or less, 95% or less, 94% or less, 90% or less, or less than 90%, and particularly 88% or less. If the Te content is too low, the amorphous state tends to become unstable. If the Te content is too high, the amorphous state tends to become unstable.

[0050] In this embodiment, As is a component that easily stabilizes the amorphous state of the stress sensor material. However, since As is a toxic component, from the viewpoint of reducing the burden on the environment, it is preferable that the As content be 5% or less, less than 5%, 4.9% or less, 4.5% or less, 3% or less, 1% or less, and particularly that As is substantially absent.

[0051] In this embodiment, Mn, Cu, W, C, Al, In, Sn, and Bi increase the gauge factor of the stress sensor material and reduce its electrical resistivity, thereby facilitating detection of strain-induced changes in electrical resistance or current of the stress sensor, and are effective components for reducing the power consumption of the stress sensor. The content of Mn+Cu+W+C+Al+In+Sn+Bi (the total content of Mn, Cu, W, C, Al, In, Sn, and Bi) is preferably 0.1% to 90%. More specifically, the lower limit of the content of Mn+Cu+W+C+Al+In+Sn+Bi is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more. The upper limit of the content of Mn+Cu+W+C+Al+In+Sn+Bi is preferably 90% or less, 80% or less, and particularly preferably 60% or less. If the content of these components is too high, the amorphous state tends to become unstable. The preferred contents of each of Mn, Cu, W, C, Al, In, Sn and Bi are as follows:

[0052] The Mn content is preferably 0% to 90%. More specifically, the lower limit of the Mn content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the Mn content is preferably 90% or less, 80% or less, 70% or less, and particularly preferably 65% ​​or less.

[0053] The Cu content is preferably 0% to 90%. More specifically, the lower limit of the Cu content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the Cu content is preferably 90% or less, 80% or less, 70% or less, and particularly preferably 65% ​​or less.

[0054] The W content is preferably 0% to 90%. More specifically, the lower limit of the W content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the W content is preferably 90% or less, 80% or less, 70% or less, and particularly preferably 65% ​​or less.

[0055] C is a component that is particularly effective in increasing the gauge factor and in decreasing the electrical resistivity. The C content is preferably 0% to 90%. More specifically, the lower limit of the C content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the C content is preferably 90% or less, 80% or less, 70% or less, and particularly preferably 65% ​​or less.

[0056] The Al content is preferably 0% to 90%. More specifically, the lower limit of the Al content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the Al content is preferably 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, and particularly preferably 20% or less.

[0057] The In content is preferably 0% to 90%. More specifically, the lower limit of the In content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the In content is preferably 90% or less, 80% or less, 70% or less, and particularly preferably 65% ​​or less.

[0058] The Sn content is preferably 0% to 90%. More specifically, the lower limit of the Sn content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the Sn content is preferably 90% or less, 80% or less, 70% or less, and particularly preferably 65% ​​or less.

[0059] The Bi content is preferably 0% to 90%. More specifically, the lower limit of the Bi content is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly preferably 0.5% or more, and the upper limit of the Bi content is preferably 90% or less, 80% or less, 70% or less, and particularly preferably 65% ​​or less.

[0060] In this embodiment, particularly from the viewpoint of reducing electrical resistivity, the Ge content is preferably 0% to 5%. More specifically, the upper limit of the Ge content is preferably 5% or less, 2% or less, 1% or less, or 0.1% or less, and it is particularly preferable that Ge is substantially not contained.

[0061] In this embodiment, the atomic ratio Ge / Te is preferably 0.5 or less, 0.2 or less, 0.1 or less, and particularly preferably less than 0.03. A stress sensor material that satisfies the above atomic ratio is likely to achieve both a high gauge factor and low electrical resistivity. The lower limit of the atomic ratio Ge / Te is not particularly limited, but may be, for example, 0 or more, particularly 0.0001 or more.

[0062] In this embodiment, C, In, and Sn are components that are particularly likely to increase the gauge factor of the stress sensor material. It is particularly preferable that the content of C+Si+In+Sn (the total amount of C, In, and Sn) is 0.1% to 90%. More specifically, the lower limit of the content of C+Si+In+Sn is preferably 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and particularly 0.5% or more, and the upper limit of the content of C+In+Sn is preferably 90% or less, 80% or less, 70% or less, and particularly 65% ​​or less. If the content of these components is too high, the amorphous state tends to become unstable.

[0063] For example, the stress sensor material of this embodiment preferably contains, in atomic %, 10% to 99% Te, 5% or less As, 0.1% to 90% Mn+Cu+W+C+Al+In+Sn+Bi, and 0% to 5% Ge; more preferably 10% to 99% Te, 5% or less As, 0.1% to 90% Mn+Cu+W+C+Al+In+Sn+Bi, and 0% to 2% Ge; and it is particularly preferable that the stress sensor material contains 10% to 99% Te, 5% or less As, and 0.1% to 90% Mn+Cu+W+C+Al+In+Sn+Bi, with substantially no Ge.

[0064] The stress sensor material of the present invention preferably has a gauge factor of 3 or more, 4 or more, 5 or more, and particularly 10 or more at a strain of 3%. The upper limit of the gauge factor at a strain of 3% is not particularly limited, but may be, for example, 10,000 or less, 5,000 or less, 1,000 or less, and particularly 500 or less. The stress sensor material of the present invention also preferably has a gauge factor of 3 or more, 4 or more, 5 or more, and particularly 10 or more at a strain of 0.1%. The upper limit of the gauge factor at a strain of 0.1% is not particularly limited, but may be, for example, 10,000 or less, 5,000 or less, 1,000 or less, and particularly 500 or less. From the viewpoint of suppressing damage to thin film samples during measurement, the strain amount used to calculate the gauge factor is preferably 5% or less, 3% or less, and particularly 1% or less. By having the above-described gauge factor, the stress sensor material of the present invention can be suitably used as a stress sensor. The gauge factor refers to the resistance change rate at 25±2°C divided by the strain amount. The amount of strain can be determined by measuring the amount of bending or the amount of elongation of the thin film. The amount of elongation of the thin film can be measured using a micrometer, calipers, laser measuring instrument, etc. The rate of resistance change can be measured using a multimeter, semiconductor parameter analyzer, etc. Note that when using a multimeter, a DC power source must be connected and voltage must be applied. The amount of bending can be measured using a micrometer, calipers, laser measuring instrument, etc., or can be approximated from the amount of deflection or radius of curvature. Specifically, the amount of bending can be calculated from the amount of deflection using the following formula (1): where ε is the strain, T is the thickness (mm) of the test piece to which the stress sensor 10 is attached, t is the thickness (mm) of the stress sensor 10, d is the amount of deflection (mm), and l is the length (mm) of the SK material to which the stress sensor 10 is attached.

[0065] ε=(4×(T+t)×d) / l ２ Formula (1)

[0066] The material of the test piece to which the stress sensor is attached is preferably metal or resin, but is not limited to these. The thickness of the test piece is preferably 0.01 mm or more, 0.02 mm or more, 0.03 mm or more, and particularly 0.05 mm or more. There is no particular upper limit, but 25 mm or less, 20 mm or less, 10 mm or less, 1 mm or less, and particularly 0.5 mm or less are preferred. If the thickness is too small, the measurement error is likely to be large. If the thickness is too large, the device for applying strain is likely to be expensive.

[0067] The gauge factor can be calculated from the obtained strain amount and resistance change rate using the following formula (2): where K is the gauge factor, R １ is the electrical resistance value (Ω) after applying tensile stress, R ０ indicates the initial electrical resistance (Ω), and ε indicates the strain.

[0068] K = ((R １ -R ０ ) / R ０ ) / ε=(ΔR / R) / ε Formula (2)

[0069] The strain ε can also be approximately calculated from the radius of curvature using the following formula (3): ε=t / 2ρ (3) where ρ represents the radius of curvature (mm) of the stress sensor 10.

[0070] The stress sensor material of the present invention has an electrical resistivity of 1.0×10 at 25±2° C. ５ Ωcm or less, 1.0×10 ４ Ωcm or less, 3.5×10 ３ Ωcm or less, 3×10 ３ Ωcm or less, 2.5×10 ３ Ωcm or less, 2×10 ３ Ωcm or less, 10 ２ Preferably, the electrical resistivity is 80 Ωcm or less, 70 Ωcm or less, 50 Ωcm or less, and particularly preferably 10 Ωcm or less. This makes it easier to detect changes in the electrical resistance or current of the stress sensor due to strain. In addition, since an amplifier circuit is not required, the power consumption of the stress sensor can be reduced. There is no particular restriction on the lower limit of the electrical resistivity, but for example, 10 －６ Ωcm or more, 2 x 10 -６ Ωcm or more, especially 3×10-５ The electrical resistivity may be Ωcm or more. The electrical resistivity can be determined by measuring the electrical resistance value and the film thickness. The electrical resistance value can be measured using a multimeter, a semiconductor parameter analyzer, or the like. The film thickness can be measured using a step gauge, fluorescent X-ray analysis, or the like.

[0071] The stress sensor material of the present invention is preferably used as a thin film. The film thickness of the thin film is preferably 1 nm to 5000 nm. More specifically, the lower limit of the film thickness is preferably 1 nm or more, 2 nm or more, 5 nm or more, 10 nm or more, 30 nm or more, and particularly preferably more than 50 nm, and the upper limit of the film thickness is preferably 5000 nm or less, 4000 nm or less, and particularly preferably 1000 nm or less. If the film thickness is too small, the electrical resistance value tends to increase. If the film thickness is too large, the gauge factor tends to decrease.

[0072] The stress sensor material of the present invention can be suitably used in stress sensors. Examples of suitable stress sensors include pressure sensors, barometric pressure sensors, strain sensors, strain gauges, acceleration sensors, and angular velocity sensors. In particular, the material can be suitably used in piezo-resistive pressure sensors.

[0073] The stress sensor material of the present invention can be produced, for example, as follows. First, raw materials are mixed to obtain the desired composition. Next, the mixed raw materials are placed in a quartz glass ampoule that has been heated and evacuated, and the ampoule is sealed with an oxygen burner while evacuating. Next, the sealed quartz glass ampoule is kept at approximately 650°C to 1000°C for 6 to 12 hours. After that, the ampoule is rapidly cooled to room temperature to obtain a bulk stress sensor material.

[0074] The raw materials may be elemental raw materials (Cu, Ge, Te, etc.) or compound raw materials (GeTe ４ etc.) and oxide raw materials (GeO ２ These may also be used in combination.

[0075] Next, by depositing a film using the above-mentioned bulk stress sensor material as a target, a thin film made of the stress sensor material can be obtained.

[0076] A thin film having the above-described composition can also be formed by a multi-sputtering method using a pure element M target (Ge, Te, Mn, Cu, W, C, Al, Si, In, Sn, and Bi), a binary alloy target, or a ternary or higher alloy target, adjusting the cathode output during film formation to adjust the components. For example, a Ge-Te precursor containing Ge and Te may be prepared, and then a thin film may be formed by co-sputtering using the Ge-Te precursor in combination with a pure element M target (Mn, Cu, W, C, Al, Si, In, Sn, and Bi).

[0077] The method for producing the thin film is not particularly limited, and a sputtering method, a vacuum deposition method, or an ion plating method can be used as a PVD method. Alternatively, a CVD (Chemical Vapor Deposition) method, an ALD (Atomic Layer Deposition) method, or the like may be selected. In particular, the sputtering method is preferred because it allows for easy composition control and film thickness control.

[0078] The thin film of the stress sensor material of the present invention is not limited to an amorphous state, but may be in a crystalline state or a state in which amorphous and crystalline are mixed.

[0079] (Stress sensor element) Fig. 1 is a schematic cross-sectional view of a stress sensor, and Fig. 2 is a schematic top view of the stress sensor. The stress sensor 10 includes a substrate 1, a thin film 2 disposed on a main surface of the substrate 1, and an electrode 3 disposed on the main surface of the thin film 2.

[0080] The substrate 1 is preferably in the form of a film. The thickness of the substrate 1 is not particularly limited, but is preferably, for example, 1 μm to 1000 μm, 5 μm to 500 μm, and particularly 10 μm to 100 μm. The material of the substrate 1 is not particularly limited, and examples that can be used include polyimide, polydimethylsiloxane (PDMS), and polyethylene terephthalate (PET).

[0081] The thin film 2 is a thin film made of the above-mentioned stress sensor material. The thickness of the thin film 2 is preferably 1 nm to 5000 nm. More specifically, the lower limit of the thickness of the thin film 2 is preferably 1 nm or more, 2 nm or more, 5 nm or more, 10 nm or more, 30 nm or more, and particularly preferably more than 50 nm, and the upper limit of the thickness of the thin film 2 is preferably 5000 nm or less, 4000 nm or less, and particularly preferably 1000 nm or less.

[0082] The electrode 3 can be made of an inorganic material. For example, it is preferable to use a metal material or a ceramic material as the inorganic material. The metal material is preferably at least one selected from gold, copper, aluminum, tungsten, titanium, and platinum. The ceramic material is preferably tungsten nitride or titanium nitride, but is not limited to these.

[0083] The thickness of the electrode 3 can be designed as appropriate. The thickness of the electrode 3 is preferably, for example, 1 nm or more, 10 nm or more, and particularly 100 nm or more. There is no particular upper limit to the thickness of the electrode 3, but it is preferably 1000 nm or less, 500 nm or less, and particularly 200 nm or less. If the thickness of the electrode 3 is too small, poor contact is likely to occur. If the thickness of the electrode 3 is too large, the manufacturing cost is likely to increase.

[0084] To prevent the electrode 3 from diffusing into the thin film 2, a barrier layer (not shown) may be formed below the electrode 3. The barrier layer is preferably made of at least one material selected from the group consisting of tantalum, tantalum nitride, titanium nitride, tungsten nitride, and molybdenum nitride, but is not limited to these.

[0085] The thickness of the barrier layer can be designed as appropriate. The thickness of the barrier layer is preferably, for example, 100 nm or less, 50 nm or less, 10 nm or less, and particularly preferably 5 nm or less. There is no particular lower limit to the thickness of the barrier layer, but it is preferably 0.1 nm or more, 0.5 nm or more, and particularly preferably 1 nm or more. If the thickness of the barrier layer is too large, the electrical resistance tends to be high. If the thickness of the barrier layer is too small, the electrode 3 tends to diffuse into the thin film 2.

[0086] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0087] Tables 1 to 6 show Examples 1 to 46 of the present invention and Comparative Examples 1 to 3.

[0088]

[0089]

[0090]

[0091]

[0092]

[0093]

[0094] (Configuration 1: Examples 1 to 12) Samples of Examples 1 to 12 were prepared as follows. First, a quartz glass ampoule was heated and evacuated, and then raw materials were mixed so that the composition ratio of Ge and Te was the value shown in Tables 1 and 2, and placed in the quartz glass ampoule. Next, the quartz glass ampoule was sealed with an oxygen burner. Next, the sealed quartz glass ampoule was placed in a melting furnace, and the temperature was raised to 650°C to 1000°C at a rate of 10°C to 40°C / hour, and then held for 6 to 12 hours. During this holding time, the quartz glass ampoule was turned upside down to stir the molten material. Finally, the quartz glass ampoule was removed from the melting furnace and rapidly cooled to room temperature to obtain a Ge-Te precursor.

[0095] Next, the following thin film samples were fabricated by Ar co-sputtering using a pure metal target (in this embodiment, a pure element target selected from Mn, Cu, and W) and a Ge—Te precursor as targets. The composition was adjusted by appropriately changing the cathode output during film formation.

[0096] (Composition analysis sample) SiO with a thickness of 725 μm ２A thin film with a thickness of 200 nm was formed on a Si / substrate to obtain a thin film sample for composition analysis. Using the obtained thin film sample, composition analysis of the thin film made of the stress sensor material was performed by energy dispersive X-ray spectroscopy (EDX). The results are shown in Tables 1 and 2.

[0097] (Gauge factor and electrical resistivity measurement sample) A thin film with a thickness of 200 nm and a width of 5 mm was formed on a 50 μm thick polyimide substrate (polyimide film), and electrodes (Au films) were formed on the main surfaces of the thin film to obtain a thin film sample for measuring the gauge factor and electrical resistivity. The electrodes had a thickness of 150 nm and a distance between the electrodes of 2 mm.

[0098] The gauge factor was calculated from the strain and resistance change rate by measuring the change in current when tensile stress was applied to the thin film sample. Specifically, a DC power supply, a tensile test jig, and a multimeter were connected in series, and tensile stress was applied until the strain amount reached 3%, at which point the resistance change rate was measured. The strain amount was measured by measuring the elongation of the thin film with a micrometer. The resistance change rate was measured using a multimeter. The gauge factor was calculated from the obtained strain amount and resistance change rate using the following formula (4). Here, K is the gauge factor, R is １ is the electrical resistance value (Ω) after applying tensile stress, R ０ indicates the initial electrical resistance (Ω), and ε indicates the strain.

[0099] K = ((R １ -R ０ ) / R ０ ) / ε=(ΔR / R) / ε Equation (4) The electrical resistivity at 25°C±2°C was calculated from the electrical resistance value and film thickness of the thin film sample. Specifically, the current value when a DC voltage of 1 V was applied to the thin film sample was measured with a multimeter and converted into an electrical resistance value. Next, the film thickness was measured with a step gauge, and the electrical resistivity was calculated using the following equation (5). Here, ρ is the electrical resistivity (Ωcm), R is the electrical resistance (Ω), and A is the cross-sectional area (cm ２ ), L indicates length (cm).

[0100] ρ=RA / L Formula (5)

[0101] Comparative Example 1 Using pure Cu metal as a target, a Cu thin film sample for measuring the gauge factor was prepared by Ar sputtering in the same manner as in Examples 1 to 12. The gauge factor and electrical resistivity at 25°C ± 2°C of the obtained thin film sample were measured in the same manner as in Examples 1 to 12.

[0102] Gauge factor, electrical resistivity ρ at 25°C ± 2°C, and electrical resistivity log at 25°C ± 2°C １０ The values ​​of ρ are shown in Tables 1 and 2. As shown in Tables 1 and 2, Examples 1 to 12 had a large gauge factor of 3 or more at a strain of 3%. ２ Less than Ωcm (log １０ The gauge factor of Comparative Example 1 was as small as 3% at a strain of 3%, which was disadvantageous in improving detection sensitivity.

[0103] (Configuration 2: Examples 13 to 29) The samples of Examples 13 to 29 were prepared as follows. First, a quartz glass ampoule was heated and evacuated, and then raw materials were mixed so that the Ge and Te composition ratios were as shown in Tables 3 and 4, and placed in the quartz glass ampoule. Next, the quartz glass ampoule was sealed with an oxygen burner. Next, the sealed quartz glass ampoule was placed in a melting furnace, and the temperature was raised to 650 to 1000°C at a rate of 10 to 40°C / hour, and then held for 6 to 12 hours. During this holding time, the quartz glass ampoule was turned upside down to stir the molten material. Finally, the quartz glass ampoule was removed from the melting furnace and rapidly cooled to room temperature to obtain a Ge-Te precursor.

[0104] Next, the following thin film samples were fabricated by Ar co-sputtering using a pure element target (in this embodiment, any one selected from Cu, W, Al, Si, Sn, and Bi) and a Ge—Te precursor as targets. The composition was adjusted by appropriately changing the cathode output during film formation.

[0105] (Composition analysis sample) SiO with a thickness of 725 μm ２ A thin film with a thickness of 200 nm was formed on a Si / substrate to obtain a thin film sample for composition analysis. Using the obtained thin film sample, composition analysis of the thin film made of the stress sensor material was performed by energy dispersive X-ray spectroscopy (EDX). The results are shown in Tables 3 and 4.

[0106] (Gauge factor and electrical resistivity measurement sample) A thin film with a thickness of 200 nm and a width of 5 mm was formed on a 50 μm thick polyimide substrate (polyimide film), and electrodes (W films) were formed on the main surfaces of the thin film to obtain a thin film sample for measuring the gauge factor and electrical resistivity. The electrodes had a thickness of 150 nm and a distance between the electrodes of 2 mm.

[0107] The gauge factor was calculated from the strain and resistance change rate by measuring the change in current when a tensile stress was applied to a thin film sample. Specifically, a DC power supply, a bending strain test jig, and a multimeter were connected in series, and bending stress was applied until the strain reached 0.1%. The resistance change rate was then measured. More specifically, the stress sensor was attached to SK material FGSM0.1 (Misumi Group Holdings, Inc.) using strain gauge adhesive CC-33A (Kyowa Electronics Co., Ltd.) with finger pressure for at least 40 seconds. After leaving the sample stationary for at least 72 hours, bending stress was applied to the attached SK material to generate a 0.1% strain in the stress sensor. The current change at this time was measured using a multimeter DMM6500 (Keithley), and the resistance change rate was calculated. The strain was calculated using the following equation (6): Here, ε is the strain, T is the thickness of the SK material (mm), t is the thickness of the stress sensor 10 (mm), d is the deflection displacement (mm), and l is the length (mm) of the SK material to which the stress sensor 10 is attached. The gauge factor was calculated from the obtained strain amount and resistance change rate using the following formula (7). Here, K is the gauge factor, R １ is the electrical resistance value (Ω) after applying tensile stress, R ０ indicates the initial electrical resistance (Ω), and ε indicates the strain.

[0108] ε=(4×(T+t)×d) / l ２ Equation (6) K=((R １ -R０ ) / R ０ ) / ε=(ΔR / R) / ε Formula (7)

[0109] The electrical resistivity at 25°C ± 2°C was calculated from the electrical resistance value and film thickness of the thin film sample. Specifically, the current value when a DC voltage of 1 V was applied to the thin film sample was measured with a multimeter and converted into an electrical resistance value. Next, the film thickness was measured with a step gauge, and the electrical resistivity was calculated using the following formula (8). Here, ρ is the electrical resistivity (Ωcm), R is the electrical resistance (Ω), and A is the cross-sectional area (cm ２ ), L indicates length (cm).

[0110] ρ=RA / L Formula (8)

[0111] (Comparative Examples 2 and 3) Using pure Cu metal and pure Si element targets, Cu thin film samples and Si thin film samples for gauge factor measurement were prepared by Ar sputtering in the same manner as in Examples 13 to 29. The Cu thin film sample was designated Comparative Example 2, and the Si thin film sample was designated Comparative Example 3. The gauge factor and electrical resistivity at 25°C ± 2°C of the obtained thin film samples were measured in the same manner as in Examples 13 to 29.

[0112] Gauge factor at strain of 0.1%, electrical resistivity ρ at 25°C ± 2°C, and electrical resistivity log at 25°C ± 2°C １０ The values ​​of ρ are shown in Tables 3 and 4. As shown in Tables 3 and 4, Examples 13 to 29 had a large gauge factor of 3 or more at a strain of 0.1%. The electrical resistivity was 3.5×10 ３ Less than Ωcm (log １０ The gauge factor of Comparative Example 2 was small (ρ was 4.54 Ω cm or less), which was advantageous in that it did not require a high-resolution measuring device and made it easy to detect changes in electrical resistance or current due to strain. Furthermore, since changes in electrical resistance or current due to strain could be easily detected, an amplifier circuit was not required, which was advantageous in terms of reducing power consumption. On the other hand, the gauge factor of Comparative Example 2 was small (less than 3), which was disadvantageous in terms of high detection sensitivity. Furthermore, the electrical resistivity of Comparative Example 3 was 2.0 × 10 ５ Ωcm (log １０However, the resistance ρ was large (5.30 Ωcm), which was disadvantageous in terms of ease of detecting changes in electrical resistance or current due to strain. Furthermore, since changes in electrical resistance or current due to strain were difficult to detect, an amplifier circuit was required, which was disadvantageous in terms of reducing power consumption.

[0113] (Mode 3: Examples 30 to 46) The samples of Examples 30 to 46 were prepared as follows. First, the following thin film samples were prepared by Ar co-sputtering using a pure element target (in this embodiment, any one selected from C, Si, In, and Sn) and a Te pure element target. The composition was adjusted by appropriately changing the cathode output during film formation. The preparation of composition analysis samples and composition analysis of thin films made of stress sensor materials were performed in the same manner as in Mode 2. In addition, the preparation of gauge factor / electrical resistivity measurement samples and the measurement of gauge factor and electrical resistivity at 25°C ± 2°C were also performed in the same manner as in Mode 2.

[0114] Gauge factor at strain of 0.1%, electrical resistivity ρ at 25°C ± 2°C, and electrical resistivity log at 25°C ± 2°C １０ The values ​​of ρ are shown in Tables 5 and 6. As shown in Tables 5 and 6, Examples 30 to 46 had a large gauge factor of 3 or more at a strain of 0.1%. The electrical resistivity was 5.7 × 10 ４ Less than Ωcm (log １０ The resistance change due to strain is small (ρ is 4.75 Ω cm or less), which is advantageous in that it does not require high-resolution measuring equipment and makes it easy to detect changes in electrical resistance or current due to strain. Furthermore, since changes in electrical resistance or current due to strain can be easily detected, an amplifier circuit is no longer necessary, which is advantageous in terms of reducing power consumption.

[0115] The stress sensor material of the present invention can be suitably used in stress sensors, such as pressure sensors, barometric pressure sensors, strain sensors, strain gauges, velocity sensors, and angular velocity sensors.

[0116] REFERENCE SIGNS LIST 1 substrate 2 thin film 3 electrode 10 stress sensor

Claims

1. A stress sensor material containing, in atomic percent, 0.1% to 50% Ge, 10% to 99% Te, and 5% or less As.

2. The stress sensor material according to claim 1, containing, in atomic percent, 0.1% to 89.9% of Mn+Cu+W+Sn+Bi.

3. A stress sensor material containing, in atomic percent, 10% to 99% Te, 5% or less As, and 0.1% to 90% Si.

4. The stress sensor material according to claim 3, wherein the atomic ratio of Ge / Te is 0.5 or less.

5. A stress sensor material containing, in atomic percent, 10% to 99% Te, 5% or less As, and 0.1% to 90% Mn+Cu+W+C+Al+In+Sn+Bi.

6. The stress sensor material according to claim 5, wherein the atomic ratio Ge / Te is 0.5 or less.

7. The stress sensor material according to any one of claims 1 to 5, which has a gauge factor of 3 or more at a strain of 0.1%.

8. Electrical resistivity at 25±2°C is 1.0×10 ５ The stress sensor material according to any one of claims 1 to 5, which has a resistivity of Ωcm or less.

9. The stress sensor material according to any one of claims 1 to 5, which is a thin film.

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