A polysilicon piezoresistance coefficient test structure and method

Abstract

A polysilicon piezoresistive coefficient test structure, including a polysilicon resistor, a film, a substrate, and a cavity; wherein: the polysilicon resistor is located on the film to ensure that each resistor is only subjected to a single stress component, the film is a silicon or silicon oxide film, and an external force acts on the film to change the resistance value of the polysilicon resistor through the stress and piezoresistive effect of the film; the substrate is a silicon wafer and is the base member of the test structure. A test method for a polysilicon piezoresistive coefficient test structure, by applying external stress to the test structure or changing the temperature over time, the film stress changes, the polysilicon resistor resistance value changes, and the piezoresistive coefficient component corresponding to the resistor can be calculated through the change in the resistance value of a single resistor. Advantages of the invention: The polysilicon piezoresistive coefficient test structure and method described in the invention realize accurate and effective testing of the polysilicon piezoresistive coefficient in the field of MEMS sensors, solves the shortcomings of traditional solutions, and improves accuracy and reliability.

Description

Technical Field

[0001] The present invention relates to the field of sensors, and in particular to a polysilicon piezoresistive coefficient testing structure and method. Background Art

[0002] In the field of MEMS sensors, many devices work using the piezoresistive effect of semiconductor materials. The so-called piezoresistive effect is a physical phenomenon in which the resistivity of a material changes under the action of an external force. The parameter that characterizes the piezoresistive effect is the piezoresistive coefficient of the material. In the MEMS industry, the more commonly used piezoresistive materials are mainly single-crystal silicon and polycrystalline silicon. The piezoresistive coefficient of single-crystal silicon materials is mainly related to the intrinsic properties of the material, such as doping and crystal orientation. Moreover, the piezoresistive coefficient of single-crystal silicon materials is known and predictable. The piezoresistive coefficient of polycrystalline silicon materials is related to the size, direction, boundary, and growth direction of polycrystalline silicon grains, and these parameters are all related to the polycrystalline silicon manufacturing process. At present, there is no effective test method to test the piezoresistive coefficient of polycrystalline silicon. At present, there is only one method to evaluate the direction of polycrystalline silicon grains through XRD technology, which cannot give the value of the piezoresistive coefficient. Summary of the invention

[0003] The purpose of the present invention is to overcome the current deficiencies and to provide a polysilicon piezoresistive coefficient testing structure and method.

[0004] The present invention provides a polysilicon piezoresistive coefficient test structure, which is characterized in that: the polysilicon piezoresistive coefficient test structure comprises a polysilicon resistor 1, a film 2, a substrate 3, and a cavity 4;

[0005] Among them: the polysilicon resistor 1 is located on the film 2 to ensure that each resistor is only subjected to a single stress component. The film 2 is a silicon or silicon oxide film. The external force acts on the film 2, and the resistance value of the polysilicon resistor 1 is changed through the stress and piezoresistive effect of the film 2. The substrate 3 is a silicon wafer, the base member of the test structure, and the cavity 4 is a rectangular structure. A certain pressure is maintained inside, and the pressure in the sealed cavity 4 is known.

[0006] The film 2 is a square suspended film with a side length of L; the polysilicon resistor 1 is located at a position where the diagonal of the square film is 1 / 4 of the side length from the nearest fixed point, and the direction of the polysilicon resistor 1 is parallel to a diagonal line.

[0007] The number of the polysilicon resistors 1 is 2 to 8.

[0008] The polysilicon resistor 1 is in the shape of a strip resistor or a cross resistor. Since the cross angle of the cross resistor is 90 degrees, different piezoresistance coefficient components can be measured on the same resistor according to different electrical configurations. The cross resistor has 4 electrical connections, namely 5, 6, 7, and 8. Connecting different resistor connection terminals will test different piezoresistance coefficient components on the same resistor. For example, if 5 and 7 are connected, the longitudinal piezoresistance component π can be tested. l ; 6, 8 connections can test the lateral piezoresistance coefficient component π t .

[0009] A test method for a polysilicon piezoresistive coefficient test structure, characterized in that: by applying external stress to the test structure or changing the temperature, the stress on the film 2 changes, and due to the piezoresistive effect of the polysilicon resistor 1, the resistance value of the polysilicon resistor changes. Due to the special position of the resistor, each resistor is only affected by a single stress component, and the piezoresistive coefficient component corresponding to the resistor can be calculated through the change in the resistance value of the single resistor.

[0010] Test structure and technology for measuring two piezoresistance coefficient components of doped polysilicon separately. This technology involves establishing a square suspended film with at least two resistors, each of which must be diagonally oriented in the square and located in a special position to ensure that each resistor is only affected by lateral or longitudinal stress. The resistor direction is at a 45-degree angle to the side of the square and is located on the diagonal. There are four resistors, each with a suitable position, and other numbers of resistors can be used to compensate for process tolerances. The cross-type resistor structure, with cross-type resistors placed in suitable positions, can provide sensitivity. There can be four cross-type resistors to increase the accuracy and reliability of process tolerances. The suspended film is on a sealed chamber, and the pressure in the sealed chamber is known. Introduction to piezoresistance coefficient:

[0011] The so-called piezoresistive effect of semiconductors refers to the phenomenon that when a semiconductor is subjected to stress, its resistivity changes due to the change in carrier mobility. The piezoresistance coefficient is a specific parameter that characterizes the piezoresistive effect. It indicates the rate of change of resistance under stress.

[0012] In polysilicon resistors, there are three types of stress: longitudinal stress, transverse stress and tangential stress. Fig. 9 The resistance changes as shown in formula 1,

[0013]

[0014] where π l,t,s is the longitudinal, lateral and tangential piezoresistance coefficient of polysilicon, σ l,t,s is the longitudinal, transverse and tangential stress of polysilicon. When the piezoresistance effect is applied in the MEMS field, the tangential piezoresistance coefficient is usually not considered, so Formula 1 is simplified to Formula 2:

[0015]

[0016] It can be seen that the change in resistance is only related to the transverse and longitudinal stresses, so in specific applications, we need to measure the transverse and longitudinal piezoresistance coefficients.

[0017] Advantages of the present invention:

[0018] The polysilicon piezoresistance coefficient testing structure and method described in the present invention realize accurate and effective testing of the piezoresistance coefficient of polysilicon in the field of MEMS sensors, solve the shortcomings of traditional solutions, and improve accuracy and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0020] Figure 1 This is a schematic diagram of the test structure of polysilicon resistor piezoresistance coefficient;

[0021] Figure 2 is a cross-sectional view of a polysilicon test structure;

[0022] Figure 3 is a schematic diagram of the resistor position;

[0023] Figure 4 Schematic diagram of a film subjected to high pressure or low temperature treatment;

[0024] Figure 5 Schematic diagram of a film subjected to low pressure external force or high temperature treatment;

[0025] Figure 6 It is a schematic diagram of the dual resistance test structure;

[0026] Figure 7 It is a schematic diagram of the cross-type resistance test structure;

[0027] Figure 8 It is a schematic diagram of a cross-type resistor;

[0028] Fig. 9 Schematic diagram of stress direction in polysilicon resistors. DETAILED DESCRIPTION

[0029] Example 1

[0030] The present invention provides a polysilicon piezoresistive coefficient test structure, which is characterized in that: the polysilicon piezoresistive coefficient test structure comprises a polysilicon resistor 1, a film 2, a substrate 3, and a cavity 4;

[0031] Among them: the polysilicon resistor 1 is located on the film 2 to ensure that each resistor is only subjected to a single stress component. The film 2 is a silicon or silicon oxide film. The external force acts on the film 2, and the resistance value of the polysilicon resistor 1 is changed through the stress and piezoresistive effect of the film 2. The substrate 3 is a silicon wafer, the base member of the test structure, and the cavity 4 is a rectangular structure. A certain pressure is maintained inside, and the pressure in the sealed cavity 4 is known.

[0032] The film 2 is a square suspended film with a side length of L; the polysilicon resistor 1 is located at a position where the diagonal of the square film is 1 / 4 of the side length from the nearest fixed point, and the direction of the polysilicon resistor 1 is parallel to a diagonal line.

[0033] There are two polysilicon resistors 1.

[0034] The polysilicon resistor 1 is in the shape of a strip resistor or a cross resistor. Since the cross angle of the cross resistor is 90 degrees, different piezoresistance coefficient components can be measured on the same resistor according to different electrical configurations. The cross resistor has 4 electrical connections, namely 5, 6, 7, and 8. Connecting different resistor connection terminals will test different piezoresistance coefficient components on the same resistor. For example, if 5 and 7 are connected, the longitudinal piezoresistance component π can be tested. l ; 6, 8 connections can test the lateral piezoresistance coefficient component π t .

[0035] A test method for a polysilicon piezoresistive coefficient test structure, characterized in that: by applying external stress to the test structure or changing the temperature, the stress on the film 2 changes, and due to the piezoresistive effect of the polysilicon resistor 1, the resistance value of the polysilicon resistor changes. Due to the special position of the resistor, each resistor is only affected by a single stress component, and the piezoresistive coefficient component corresponding to the resistor can be calculated through the change in the resistance value of the single resistor.

[0036] Test structure and technology for measuring two piezoresistance coefficient components of doped polysilicon separately. This technology involves establishing a square suspended film with at least two resistors, each of which must be diagonally oriented in the square and located in a special position to ensure that each resistor is only affected by lateral or longitudinal stress. The resistor direction is at a 45-degree angle to the side of the square and is located on the diagonal. There are four resistors, each with a suitable position, and other numbers of resistors can be used to compensate for process tolerances. The cross-type resistor structure, with cross-type resistors placed in suitable positions, can provide sensitivity. There can be four cross-type resistors to increase the accuracy and reliability of process tolerances. The suspended film is on a sealed chamber, and the pressure in the sealed chamber is known. Introduction to piezoresistance coefficient:

[0037] The so-called piezoresistive effect of semiconductors refers to the phenomenon that when a semiconductor is subjected to stress, its resistivity changes due to the change in carrier mobility. The piezoresistance coefficient is a specific parameter that characterizes the piezoresistive effect. It indicates the rate of change of resistance under stress.

[0038] In polysilicon resistors, there are three types of stress: longitudinal stress, transverse stress and tangential stress. Fig. 9 The resistance changes as shown in formula 1,

[0039]

[0040] where π l,t,s is the longitudinal, lateral and tangential piezoresistance coefficient of polysilicon, σ l,t,s is the longitudinal, transverse and tangential stress of polysilicon. When the piezoresistance effect is applied in the MEMS field, the tangential piezoresistance coefficient is usually not considered, so Formula 1 is simplified to Formula 2:

[0041]

[0042] It can be seen that the change in resistance is only related to the transverse and longitudinal stresses, so in specific applications, we need to measure the transverse and longitudinal piezoresistance coefficients.

[0043] Example 2

[0044] The present invention provides a polysilicon piezoresistive coefficient test structure, which is characterized in that: the polysilicon piezoresistive coefficient test structure comprises a polysilicon resistor 1, a film 2, a substrate 3, and a cavity 4;

[0045] Among them: the polysilicon resistor 1 is located on the film 2 to ensure that each resistor is only subjected to a single stress component. The film 2 is a silicon or silicon oxide film. The external force acts on the film 2, and the resistance value of the polysilicon resistor 1 is changed through the stress and piezoresistive effect of the film 2. The substrate 3 is a silicon wafer, the base member of the test structure, and the cavity 4 is a rectangular structure. A certain pressure is maintained inside, and the pressure in the sealed cavity 4 is known.

[0046] The film 2 is a square suspended film with a side length of L; the polysilicon resistor 1 is located at a position where the diagonal of the square film is 1 / 4 of the side length from the nearest fixed point, and the direction of the polysilicon resistor 1 is parallel to a diagonal line.

[0047] The number of the polysilicon resistors 1 is 4.

[0048] The polysilicon resistor 1 is in the shape of a strip resistor or a cross resistor. Since the cross angle of the cross resistor is 90 degrees, different piezoresistance coefficient components can be measured on the same resistor according to different electrical configurations. The cross resistor has 4 electrical connections, namely 5, 6, 7, and 8. Connecting different resistor connection terminals will test different piezoresistance coefficient components on the same resistor. For example, if 5 and 7 are connected, the longitudinal piezoresistance component π can be tested. l ; 6, 8 connections can test the lateral piezoresistance coefficient component π t .

[0049] A test method for a polysilicon piezoresistive coefficient test structure, characterized in that: by applying external stress to the test structure or changing the temperature, the stress on the film 2 changes, and due to the piezoresistive effect of the polysilicon resistor 1, the resistance value of the polysilicon resistor changes. Due to the special position of the resistor, each resistor is only affected by a single stress component, and the piezoresistive coefficient component corresponding to the resistor can be calculated through the change in the resistance value of the single resistor.

[0050] Test structure and technology for measuring two piezoresistance coefficient components of doped polysilicon separately. This technology involves establishing a square suspended film with at least two resistors, each of which must be diagonally oriented in the square and located in a special position to ensure that each resistor is only affected by lateral or longitudinal stress. The resistor direction is at a 45-degree angle to the side of the square and is located on the diagonal. There are four resistors, each with a suitable position, and other numbers of resistors can be used to compensate for process tolerances. The cross-type resistor structure, with cross-type resistors placed in suitable positions, can provide sensitivity. There can be four cross-type resistors to increase the accuracy and reliability of process tolerances. The suspended film is on a sealed chamber, and the pressure in the sealed chamber is known. Introduction to piezoresistance coefficient:

[0051] The so-called piezoresistive effect of semiconductors refers to the phenomenon that when a semiconductor is subjected to stress, its resistivity changes due to the change in carrier mobility. The piezoresistance coefficient is a specific parameter that characterizes the piezoresistive effect. It indicates the rate of change of resistance under stress.

[0052] In polysilicon resistors, there are three types of stress: longitudinal stress, transverse stress and tangential stress. Fig. 9 The resistance changes as shown in formula 1,

[0053]

[0054] where π l,t,s is the longitudinal, lateral and tangential piezoresistance coefficient of polysilicon, σ l,t,s is the longitudinal, transverse and tangential stress of polysilicon. When the piezoresistance effect is applied in the MEMS field, the tangential piezoresistance coefficient is usually not considered, so Formula 1 is simplified to Formula 2:

[0055]

[0056] It can be seen that the change in resistance is only related to the transverse and longitudinal stresses, so in specific applications, we need to measure the transverse and longitudinal piezoresistance coefficients.

[0057] Example 3

[0058] The present invention provides a polysilicon piezoresistive coefficient test structure, which is characterized in that: the polysilicon piezoresistive coefficient test structure comprises a polysilicon resistor 1, a film 2, a substrate 3, and a cavity 4;

[0059] Among them: the polysilicon resistor 1 is located on the film 2 to ensure that each resistor is only subjected to a single stress component. The film 2 is a silicon or silicon oxide film. The external force acts on the film 2, and the resistance value of the polysilicon resistor 1 is changed through the stress and piezoresistive effect of the film 2. The substrate 3 is a silicon wafer, the base member of the test structure, and the cavity 4 is a rectangular structure. A certain pressure is maintained inside, and the pressure in the sealed cavity 4 is known.

[0060] The film 2 is a square suspended film with a side length of L; the polysilicon resistor 1 is located at a position where the diagonal of the square film is 1 / 4 of the side length from the nearest fixed point, and the direction of the polysilicon resistor 1 is parallel to a diagonal line.

[0061] The number of the polysilicon resistors 1 is 8.

[0062] The polysilicon resistor 1 is in the shape of a strip resistor or a cross resistor. Since the cross angle of the cross resistor is 90 degrees, different piezoresistance coefficient components can be measured on the same resistor according to different electrical configurations. The cross resistor has 4 electrical connections, namely 5, 6, 7, and 8. Connecting different resistor connection terminals will test different piezoresistance coefficient components on the same resistor. For example, if 5 and 7 are connected, the longitudinal piezoresistance component π can be tested. l ; 6, 8 connections can test the lateral piezoresistance coefficient component π t .

[0063] A test method for a polysilicon piezoresistive coefficient test structure, characterized in that: by applying external stress to the test structure or changing the temperature, the stress on the film 2 changes, and due to the piezoresistive effect of the polysilicon resistor 1, the resistance value of the polysilicon resistor changes. Due to the special position of the resistor, each resistor is only affected by a single stress component, and the piezoresistive coefficient component corresponding to the resistor can be calculated through the change in the resistance value of the single resistor.

[0064] Test structure and technology for measuring two piezoresistance coefficient components of doped polysilicon separately. This technology involves establishing a square suspended film with at least two resistors, each of which must be diagonally oriented in the square and located in a special position to ensure that each resistor is only affected by lateral or longitudinal stress. The resistor direction is at a 45-degree angle to the side of the square and is located on the diagonal. There are four resistors, each with a suitable position, and other numbers of resistors can be used to compensate for process tolerances. The cross-type resistor structure, with cross-type resistors placed in suitable positions, can provide sensitivity. There can be four cross-type resistors to increase the accuracy and reliability of process tolerances. The suspended film is on a sealed chamber, and the pressure in the sealed chamber is known. Introduction to piezoresistance coefficient:

[0065] The so-called piezoresistive effect of semiconductors refers to the phenomenon that when a semiconductor is subjected to stress, its resistivity changes due to the change in carrier mobility. The piezoresistance coefficient is a specific parameter that characterizes the piezoresistive effect. It indicates the rate of change of resistance under stress.

[0066] In polysilicon resistors, there are three types of stress: longitudinal stress, transverse stress and tangential stress. Fig. 9 The resistance changes as shown in formula 1,

[0067]

[0068] where π l,t,s is the longitudinal, lateral and tangential piezoresistance coefficient of polysilicon, σ l,t,s is the longitudinal, transverse and tangential stress of polysilicon. When the piezoresistance effect is applied in the MEMS field, the tangential piezoresistance coefficient is usually not considered, so Formula 1 is simplified to Formula 2:

[0069]

[0070] It can be seen that the change in resistance is only related to the transverse and longitudinal stresses, so in specific applications, we need to measure the transverse and longitudinal piezoresistance coefficients.

Claims

1. A polysilicon piezoresistive coefficient test structure, characterized in that: The polysilicon piezoresistive coefficient test structure comprises a polysilicon resistor (1), a film (2), a substrate (3), and a cavity (4); The polysilicon resistor (1) is located on the film (2) to ensure that each resistor is only subjected to a single stress component. The film (2) is a silicon or silicon oxide film. When an external force acts on the film (2), the resistance value of the polysilicon resistor (1) is changed through the stress and piezoresistive effect of the film (2). The substrate (3) is a silicon wafer, which is the base member of the test structure. The cavity (4) is a rectangular parallelepiped structure, and a certain pressure is maintained inside. The pressure in the sealed cavity (4) is known. The film (2) is a square suspended film with a side length of L. The position of the polysilicon resistor (1) is located at a position where the diagonal of the square film is 1 / 4 of the side length of the nearest fixed point, and the direction of the polysilicon resistor (1) is parallel to a diagonal line. There are 2 to 8 polysilicon resistors (1). The shape of the polysilicon resistor (1) is a strip resistor or a cross-type resistor. Since the cross-type resistor has a cross angle of 90 degrees, different piezoresistance coefficient components can be measured on the same resistor according to different electrical configurations.

2. A method for testing the polysilicon piezoresistance coefficient test structure according to claim 1, characterized in that: Testing method: By applying external stress to the test structure or changing the temperature, the stress on the film (2) changes. Due to the piezoresistive effect of the polysilicon resistor (1), the resistance value of the polysilicon resistor changes. Due to the special position of the resistor, each resistor is only affected by a single stress component. The piezoresistive coefficient component corresponding to the resistor can be calculated through the change in the resistance value of a single resistor.

3. The method for testing a polysilicon piezoresistance coefficient test structure according to claim 2, characterized in that: The test structure and technology for measuring the two piezoresistance coefficient components of doped polysilicon separately include the establishment of a square suspended film with at least two resistors, each of which must be in the diagonal direction of the square and located in a special position to ensure that each resistor is only affected by lateral or longitudinal stress. The direction of the resistor is 45 degrees to the side length of the square and is located on the diagonal.

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