CN213023334U - Polysilicon piezoresistive coefficient test structure - Google Patents
Polysilicon piezoresistive coefficient test structure Download PDFInfo
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- CN213023334U CN213023334U CN202021224220.XU CN202021224220U CN213023334U CN 213023334 U CN213023334 U CN 213023334U CN 202021224220 U CN202021224220 U CN 202021224220U CN 213023334 U CN213023334 U CN 213023334U
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Abstract
A polysilicon piezoresistive coefficient test structure comprises a polysilicon resistor, a film, a substrate and a cavity; wherein: the polycrystalline silicon resistors are positioned on the film, each resistor is only under the action of a single stress component, the film is a silicon or silicon oxide film, external force acts on the film, and the resistance value of each polycrystalline silicon resistor is changed through the stress of the film and the piezoresistive effect; the substrate is a silicon wafer, the base piece of the test structure is a cuboid structure, a certain pressure is kept in the cuboid structure, and the pressure in the sealed cavity is known. The utility model has the advantages that: polycrystalline silicon piezoresistive coefficient test structure, in MEMS sensor field, realized accurate effectual test polycrystalline silicon's piezoresistive coefficient, solved the not enough of traditional scheme, promoted precision and reliability.
Description
Technical Field
The utility model relates to a sensor field, in particular to polycrystalline silicon piezoresistive coefficient test structure.
Background
In the field of MEMS sensors, many devices work by using the piezoresistive effect of semiconductor materials, which is a physical phenomenon that the resistivity of a material changes under the action of an external force, wherein the parameter characterizing the piezoresistive effect is the piezoresistive coefficient of the material. In the MEMS industry, the piezoresistive materials commonly used mainly include monocrystalline silicon and polycrystalline silicon, and the piezoresistive coefficient of the monocrystalline silicon material is mainly related to the intrinsic characteristics of the material, such as doping and crystal orientation. And the piezoresistive coefficient of the single crystal silicon material is known and can be predicted. The piezoresistive coefficient of polysilicon material is related to the size, direction, boundary, and growth direction of polysilicon grains, and these parameters are related to the polysilicon manufacturing process. There is currently no effective test method for measuring the piezoresistive coefficient of polysilicon. Currently, only a method for evaluating the grain orientation of polycrystalline silicon by XRD technology cannot give a numerical value of piezoresistive coefficient.
SUMMERY OF THE UTILITY MODEL
The utility model aims at overcoming the present not enough, provides a polycrystalline silicon piezoresistive coefficient test structure specially.
The utility model provides a polycrystalline silicon piezoresistive coefficient test structure, its characterized in that: the polysilicon piezoresistive coefficient test structure comprises a polysilicon resistor 1, a film 2, a substrate 3 and a cavity 4;
wherein: the polycrystalline silicon resistors 1 are positioned on the thin film 2, each resistor is only under the action of a single stress component, the thin film 2 is a silicon or silicon oxide thin film, external force acts on the thin film 2, and the resistance value of the polycrystalline silicon resistors 1 is changed through the stress and piezoresistive effect of the thin film 2; the substrate 3 is a silicon wafer, the base member of the test structure, the chamber 4 is a rectangular parallelepiped structure, a certain pressure is maintained inside, and the pressure in the sealed chamber 4 is known.
The film 2 is a square suspended film, and the side length is L; the position of the polysilicon resistor 1 is located at the position of the diagonal of the square film from the side length of the nearest fixed point 1/4, and the direction of the polysilicon resistor 1 is parallel to one diagonal.
The number of the polysilicon resistors 1 is 2-8.
The polysilicon resistor 1 is in a strip resistor or a cross resistor shape; because the cross angle of the cross-type resistor is 90 degrees, different piezoresistive coefficient components are measured on the same resistor according to different electrical configurations; the cross-type resistor has 4 electrical connections, 5, 6, 7 and 8 respectively, and different piezoresistive coefficient components can be tested on the same resistor by connecting different resistor connecting terminals. E.g. 5, 7 connections, the longitudinal piezoresistive component pi can be testedl(ii) a 6. 8 connection can test transverse piezoresistive coefficient component pit。
The stress of the film 2 is changed by external stress or temperature change of the test structure, the resistance value of the polysilicon resistor is changed due to the piezoresistive effect of the polysilicon resistor 1, each resistor is only affected by a single stress component due to the special position of the resistor, and the piezoresistive coefficient component corresponding to the resistor can be calculated through the change of the resistance value of the single resistor.
Test structures and techniques to separately measure 2 piezoresistive coefficient components of doped polysilicon. This technique consists in creating a square suspended membrane, at least 2 resistors, each of which must be square in the diagonal direction, in a specific position, ensuring that each resistor is affected only by transverse or longitudinal stresses. The resistance direction is 45 degrees from the square side and is on the diagonal. 4 resistors, each with a suitable position, may also be provided with other numbers of resistors in order to compensate for process tolerances. A cross-resistor structure, with cross resistors placed in appropriate locations, can provide sensitivity. There may be 4 cross-type resistors in order to increase the accuracy and reliability of process tolerances. The suspended membrane is on a sealed chamber, the pressure in which is known. Introduction of piezoresistive coefficients:
the piezoresistive effect of a semiconductor refers to a phenomenon in which when a semiconductor is subjected to a stress, its resistivity changes due to a change in carrier mobility. The piezoresistive coefficient is a specific parameter for characterizing the piezoresistive effect. Indicating the rate of change of resistance under stress.
In the polysilicon resistor, there are three stresses, longitudinal stress, lateral stress and tangential stress, see fig. 9. The resistance change is as in equation 1,
wherein pil,t,sIs the longitudinal, transverse and tangential piezoresistive coefficient, sigma, of polysiliconl,t,sThe stress is the longitudinal, transverse and tangential stress of the polysilicon. In the case of applying piezoresistive effect in the MEMS field, the tangential piezoresistive coefficient is usually not considered, so equation 1 is reduced to equation 2:
it can be seen that the change in resistance is related only to lateral and longitudinal stresses, so in a particular application we need to measure the piezoresistive coefficients in both the lateral and longitudinal directions.
The utility model has the advantages that:
polycrystalline silicon piezoresistive coefficient test structure, in MEMS sensor field, realized accurate effectual test polycrystalline silicon's piezoresistive coefficient, solved the not enough of traditional scheme, promoted precision and reliability.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and embodiments:
FIG. 1 is a schematic diagram of a polysilicon resistance piezoresistive coefficient test structure;
FIG. 2 is a cross-sectional view of a polysilicon test structure;
FIG. 3 is a schematic diagram of the resistor location;
FIG. 4 is a schematic view of a high pressure applied or low temperature processed film;
FIG. 5 is a schematic view of a low pressure force or high temperature processing film;
FIG. 6 is a schematic diagram of a dual resistance test structure;
FIG. 7 is a schematic diagram of a cross-type resistance test structure;
FIG. 8 is a schematic diagram of a cross-type resistor;
fig. 9 is a schematic diagram of stress direction in the polysilicon resistor.
Detailed Description
Example 1
The utility model provides a polycrystalline silicon piezoresistive coefficient test structure, its characterized in that: the polysilicon piezoresistive coefficient test structure comprises a polysilicon resistor 1, a film 2, a substrate 3 and a cavity 4;
wherein: the polycrystalline silicon resistors 1 are positioned on the thin film 2, each resistor is only under the action of a single stress component, the thin film 2 is a silicon or silicon oxide thin film, external force acts on the thin film 2, and the resistance value of the polycrystalline silicon resistors 1 is changed through the stress and piezoresistive effect of the thin film 2; the substrate 3 is a silicon wafer, the base member of the test structure, the chamber 4 is a rectangular parallelepiped structure, a certain pressure is maintained inside, and the pressure in the sealed chamber 4 is known.
The film 2 is a square suspended film, and the side length is L; the position of the polysilicon resistor 1 is located at the position of the diagonal of the square film from the side length of the nearest fixed point 1/4, and the direction of the polysilicon resistor 1 is parallel to one diagonal.
The number of the polysilicon resistors 1 is 4.
The polysilicon resistor 1 is in a strip resistor or a cross resistor shape; because the cross angle of the cross-type resistor is 90 degrees, different piezoresistive coefficient components are measured on the same resistor according to different electrical configurations; the cross-type resistor has 4 electrical connections, 5, 6, 7 and 8 respectively, and different piezoresistive coefficient components can be tested on the same resistor by connecting different resistor connecting terminals. E.g. 5, 7 connections, the longitudinal piezoresistive component pi can be testedl(ii) a 6. 8 connection can test transverse piezoresistive coefficient component pit。
The stress of the film 2 is changed by external stress or temperature change of the test structure, the resistance value of the polysilicon resistor is changed due to the piezoresistive effect of the polysilicon resistor 1, each resistor is only affected by a single stress component due to the special position of the resistor, and the piezoresistive coefficient component corresponding to the resistor can be calculated through the change of the resistance value of the single resistor.
Test structures and techniques to separately measure 2 piezoresistive coefficient components of doped polysilicon. This technique consists in creating a square suspended membrane, at least 2 resistors, each of which must be square in the diagonal direction, in a specific position, ensuring that each resistor is affected only by transverse or longitudinal stresses. The resistance direction is 45 degrees from the square side and is on the diagonal. 4 resistors, each with a suitable position, may also be provided with other numbers of resistors in order to compensate for process tolerances. A cross-resistor structure, with cross resistors placed in appropriate locations, can provide sensitivity. There may be 4 cross-type resistors in order to increase the accuracy and reliability of process tolerances. The suspended membrane is on a sealed chamber, the pressure in which is known. Introduction of piezoresistive coefficients:
the piezoresistive effect of a semiconductor refers to a phenomenon in which when a semiconductor is subjected to a stress, its resistivity changes due to a change in carrier mobility. The piezoresistive coefficient is a specific parameter for characterizing the piezoresistive effect. Indicating the rate of change of resistance under stress.
In the polysilicon resistor, there are three stresses, longitudinal stress, lateral stress and tangential stress, see fig. 9. The resistance change is as in equation 1,
wherein pil,t,sIs the longitudinal, transverse and tangential piezoresistive coefficient, sigma, of polysiliconl,t,sThe stress is the longitudinal, transverse and tangential stress of the polysilicon. In the case of applying piezoresistive effect in the MEMS field, the tangential piezoresistive coefficient is usually not considered, so equation 1 is reduced to equation 2:
it can be seen that the change in resistance is related only to lateral and longitudinal stresses, so in a particular application we need to measure the piezoresistive coefficients in both the lateral and longitudinal directions.
Example 2
The utility model provides a polycrystalline silicon piezoresistive coefficient test structure, its characterized in that: the polysilicon piezoresistive coefficient test structure comprises a polysilicon resistor 1, a film 2, a substrate 3 and a cavity 4;
wherein: the polycrystalline silicon resistors 1 are positioned on the thin film 2, each resistor is only under the action of a single stress component, the thin film 2 is a silicon or silicon oxide thin film, external force acts on the thin film 2, and the resistance value of the polycrystalline silicon resistors 1 is changed through the stress and piezoresistive effect of the thin film 2; the substrate 3 is a silicon wafer, the base member of the test structure, the chamber 4 is a rectangular parallelepiped structure, a certain pressure is maintained inside, and the pressure in the sealed chamber 4 is known.
The film 2 is a square suspended film, and the side length is L; the position of the polysilicon resistor 1 is located at the position of the diagonal of the square film from the side length of the nearest fixed point 1/4, and the direction of the polysilicon resistor 1 is parallel to one diagonal.
The number of the polysilicon resistors 1 is 8.
The polysilicon resistor 1 is in a strip resistor or a cross resistor shape; because the cross angle of the cross-type resistor is 90 degrees, different piezoresistive coefficient components are measured on the same resistor according to different electrical configurations; the cross-type resistor has 4 electrical connections, 5, 6, 7 and 8 respectively, and different piezoresistive coefficient components can be tested on the same resistor by connecting different resistor connecting terminals. E.g. 5, 7 connections, the longitudinal piezoresistive component pi can be testedl(ii) a 6. 8 connection can test transverse piezoresistive coefficient component pit。
The stress of the film 2 is changed by external stress or temperature change of the test structure, the resistance value of the polysilicon resistor is changed due to the piezoresistive effect of the polysilicon resistor 1, each resistor is only affected by a single stress component due to the special position of the resistor, and the piezoresistive coefficient component corresponding to the resistor can be calculated through the change of the resistance value of the single resistor.
Test structures and techniques to separately measure 2 piezoresistive coefficient components of doped polysilicon. This technique consists in creating a square suspended membrane, at least 2 resistors, each of which must be square in the diagonal direction, in a specific position, ensuring that each resistor is affected only by transverse or longitudinal stresses. The resistance direction is 45 degrees from the square side and is on the diagonal. 4 resistors, each with a suitable position, may also be provided with other numbers of resistors in order to compensate for process tolerances. A cross-resistor structure, with cross resistors placed in appropriate locations, can provide sensitivity. There may be 4 cross-type resistors in order to increase the accuracy and reliability of process tolerances. The suspended membrane is on a sealed chamber, the pressure in which is known. Introduction of piezoresistive coefficients:
the piezoresistive effect of a semiconductor refers to a phenomenon in which when a semiconductor is subjected to a stress, its resistivity changes due to a change in carrier mobility. The piezoresistive coefficient is a specific parameter for characterizing the piezoresistive effect. Indicating the rate of change of resistance under stress.
In the polysilicon resistor, there are three stresses, longitudinal stress, lateral stress and tangential stress, see fig. 9. The resistance change is as in equation 1,
wherein pil,t,sIs the longitudinal, transverse and tangential piezoresistive coefficient, sigma, of polysiliconl,t,sThe stress is the longitudinal, transverse and tangential stress of the polysilicon. In the case of applying piezoresistive effect in the MEMS field, the tangential piezoresistive coefficient is usually not considered, so equation 1 is reduced to equation 2:
it can be seen that the change in resistance is related only to lateral and longitudinal stresses, so in a particular application we need to measure the piezoresistive coefficients in both the lateral and longitudinal directions.
Claims (4)
1. A polysilicon piezoresistive coefficient test structure is characterized in that: the polycrystalline silicon piezoresistive coefficient test structure comprises a polycrystalline silicon resistor (1), a film (2), a substrate (3) and a cavity (4);
wherein: the polycrystalline silicon resistor (1) is positioned on the film (2) to ensure that each resistor is only subjected to the action of a single stress component, the film (2) is a silicon or silicon oxide film, external force acts on the film (2), and the resistance value of the polycrystalline silicon resistor (1) is changed through the stress and piezoresistive effect of the film (2); the substrate (3) is a silicon wafer, the base piece of the test structure is a cuboid structure, the cavity (4) is internally kept with certain pressure, and the pressure in the sealed cavity (4) is known.
2. The polysilicon piezoresistive coefficient test structure of claim 1, wherein: the film (2) is a square suspended film, and the side length is L; the position of the polysilicon resistor (1) is positioned at the position of the diagonal of the square film away from the side length of the nearest fixed point 1/4, and the direction of the polysilicon resistor (1) is parallel to one diagonal.
3. The polysilicon piezoresistive coefficient test structure of claim 1, wherein: the number of the polysilicon resistors (1) is 2-8.
4. The polysilicon piezoresistive coefficient test structure of claim 1, wherein: the polysilicon resistor (1) is in a strip resistor or a cross resistor shape; since the cross angle of the cross-type resistor is 90 degrees, different piezoresistive coefficient components are measured on the same resistor according to different electrical configurations.
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