CN113218755B - A system for biaxial tensile testing of nanoscale films and method of making the same - Google Patents

Abstract

The invention provides a system for biaxial tensile testing of nano-scale thin films and a manufacturing method thereof, belonging to the technical field of microelectronic mechanical system processing. The system utilizes a uniquely designed on-chip testing machine structure and a probe for microelectronic process detection and analysis The on-chip testing machine includes two tensile structures arranged perpendicular to each other; each tensile structure includes a probe loading structure, two wheel-shaped loading and reversing structures, A movable frame, an elastic beam, a tensile beam, two deformation scales, two pointers and two suspended folding beams. The system can be used to explore the failure law of thin film materials at the nanoscale, and can also be used to monitor the quality of thin film preparation processes.

Description

A system for biaxial tensile testing of nanoscale films and method of making the same

technical field

The invention belongs to the technical field of micro-electromechanical systems (MEMS) processing, relates to a system for biaxial tensile testing of nano-scale thin films and a manufacturing method thereof, and is particularly applied to exploring the destruction law of thin-film materials at nano-scale.

Background technique

Failure behavior occurs when the structure is subjected to external loads exceeding a critical value. Judging whether a structure will fail under a certain external load is an important issue, because the structure will face the challenge of possible failure from the initial manufacturing to the final use. To solve this problem, the theory of elasticity and strength was established. The elastic mechanics is responsible for calculating the internal stress of the structure caused by the external load, and the strength theory is responsible for judging whether the material will fail under a certain stress state, so the strength theory is also called the material fracture criterion (criteria). The fracture criterion of the material needs to be established on the basis of a large number of experiments. The experiment usually requires biaxial tensile testing of the material sample to extract the different internal stress conditions when the material is damaged. The current conventional biaxial tensile testing machines are only suitable for testing specimens with dimensions of millimeters and above. With the rapid development of micro-nano processing technology and the continuous emergence of MEMS/NEMS devices, the research on the destruction law of materials at the micro-nano scale has become the core basic work affecting the development of the industry. For micro-nano-scale samples, due to the difficulties in fastening, loading, and detection, there is still a lack of corresponding detection methods. Therefore, it is necessary to propose a more reasonable method to perform biaxial tensile test on micro-nano-scale samples to extract the biaxial stress at the time of fracture, so as to study the failure law of materials at the micro-nano scale.

SUMMARY OF THE INVENTION

It can be seen from the above analysis that the traditional biaxial tensile testing machine cannot extract the biaxial stress when the micro-nanoscale film sample breaks. The purpose of the present invention is to propose a method for extracting the biaxial stress when the nanoscale film sample breaks. The system and its manufacturing method utilize a system combining a newly designed on-chip testing machine structure and a probe station for microelectronic process detection and analysis to extract the biaxial stress when the nanoscale film is fractured. This method can be used to explore the failure law of thin film materials at the nanoscale, and can also be used to monitor the quality of thin film preparation processes.

The technical scheme adopted in the present invention is as follows:

A system for biaxial tensile testing of nanoscale films, comprising an on-chip testing machine and a probe station for applying a load force to the on-chip testing machine, the on-chip testing machine comprising two mutually perpendicular tensile structures; Each tensile structure includes a probe loading structure, two wheel-shaped loading and reversing structures, a movable frame, an elastic beam, a tensile beam, two deformation variable scales, two pointers and two suspension folding beams; The needle loading structure is used to undertake the probe loading of the probe station; the two wheel-shaped loading reversing structures are located on the symmetrical sides of the probe loading structure, and both include a wheel-shaped structure and several spoke beams. Both sides are connected to the probe loading structure, and opposite sides are connected to the two forearm beams of the movable frame, and the spoke beams connect the wheel-shaped structure to the first anchor point of the wheel-shaped axis; The two front arm beams extending in the direction of the shape loading reversing structure and the two rear arm beams deviating from this direction, the rear ends of the two forearm beams and the front ends of the two rear arm beams are fixed to each other, and the two forearm beams and the two rear arm beams are symmetrically distributed. , the inside of the rear ends of the two rear arm beams are provided with the two deformation variable scales; one end of the two suspension folding beams is respectively connected to both sides of the movable frame, and the other ends are respectively fixed on the two second anchor points; the elastic beams are vertically connected Two rear arm beams of the movable frame; the tensile beam includes a vertical beam and a cross beam, the vertical beam is arranged in parallel in the middle of the two rear arm beams of the movable frame, one end of which is connected to the middle part of the elastic beam, and the other end is connected to the middle of the elastic beam. One side of a square film sample is connected; the middle part of the beam is vertically connected to the vertical beam, and the two pointers are provided at both ends; the two pointers are respectively used to mark the scales of the two deformation variable scales; The two adjacent sides of the film sample that are not connected by the tensile beams of the two tensile structures are fixedly connected to the two third anchor points respectively.

Further, the probe loading structure has a V-shaped loading port, which can ensure the accuracy of the loading position and the direction of the loading force.

Further, the distance between the two rear arm beams of the movable frame is narrower than the distance between the two forearms, the forearm beam and the rear arm beam on each side are connected by a shoulder beam perpendicular to it, and one end of the suspension folding beam is specifically Attached to the shoulder beam.

Further, the spoke beams of the wheel-shaped loading reversing structure are evenly distributed circumferentially around the first anchor point.

Further, two adjacent suspension folding beams of the two tensile structures are connected to the same second anchor point.

Further, the first anchor point is a diamond or circular section anchor point, the second anchor point is a square section anchor point, and the third anchor point is a rectangular section anchor point.

Further, the four vertices of the square of the thin film sample all contain the same triangular notches, and the shape design can make the inner test area in a uniform stress state and with a high stress level.

Further, the thickness of the thin film sample is in the order of nanometers, and the length and width are in the order of micrometers.

A method of manufacturing a system for biaxial tensile testing of nanoscale films, comprising manufacturing an on-chip testing machine and a probe station, wherein the steps of manufacturing the on-chip testing machine include:

(1) using photolithography and etching to form a bonding anchor point on the front side of the silicon wafer, the anchor point includes a first anchor point, a second anchor point and a third anchor point;

(2) depositing a thin film material on the front side of the silicon wafer, according to the plane shape and size of the thin film sample, using photolithography and etching or etching to form a thin film sample pattern;

(3) Use photolithography and wet etching to form shallow grooves on the glass sheet, then sputter metal on the glass sheet, and then use a peeling process to form anti-footing metal electrodes;

(4) anodic bonding the silicon wafer and the glass wafer processed through the above steps;

(5) Use wet etching to thin the silicon wafer to the designed thickness;

(6) Using photolithography and deep etching to partially etch through the silicon wafer from the back surface to release the movable structure and the thin film sample, the movable structure is the entire silicon structure except the anchor point, and the on-chip testing machine is obtained.

Further, an N-type single crystal silicon wafer is selected as the silicon wafer, and the resistivity is 0.001-0.003 Ω·cm; the silicon is dry-etched by ASE to form a bonding anchor point.

Further, PVD, CVD, ALD or electroplating methods are used to deposit thin film material on the front side of the silicon wafer.

Further, three metals of Ti, Pt and Au were sputtered on the glass sheet.

In order to extract the biaxial stress when the nano-scale thin film sample is broken, the invention designs a corresponding on-chip testing machine structure, and proposes an on-chip testing machine combined with a probe station for microelectronic process detection and analysis to extract the nano-scale thin film test. A system of biaxial stress at sample fracture. The elastic beam is used to measure the tensile force on the end of the film specimen. The deformation variable scale is used to record the deformation information of the elastic beam. The suspension folding beam group is used to support the entire suspension structure to ensure the support stability of the on-chip testing machine during the manufacturing and testing process. The wheel-shaped loading reversing structure is used to convert the push force of the probe into the pull force on the thin film sample. A load force is applied to the on-chip testing machine by using the probe of the probe station until the film sample in the on-chip testing machine breaks, and the reading of the deformation variable scale in the on-chip testing machine is recorded; The biaxial uniform tensile load received can be obtained by using finite element simulation tools such as ANSYS to obtain the internal biaxial stress at the time of fracture. The invention also provides a manufacturing method of the system, which adds a thin film deposition and photolithography on the basis of the standard process of bonding deep etch release to realize the structure manufacturing of the on-chip test machine, and combines the manufactured on-chip test machine with the probe manufactured by using the existing technology. The system can be obtained after the needle table is assembled and used. Compared with the existing biaxial tensile testing methods and systems, it has the following advantages: 1) biaxial tensile testing of nanoscale film samples can be carried out; 2) the method is simple and does not require large precision instruments; 3) it can Process quality monitoring of the thin film preparation process.

Description of drawings

FIG. 1 is a schematic structural diagram of an on-chip testing machine in an embodiment of the present invention.

In the figure: 101-probe loading structure, 102-wheel-shaped loading and reversing structure, 1021-wheel-shaped structure, 1022-spoke beam, 103-first anchor point, 104-movable frame, 1041-forearm beam, 1042- Backarm beam, 1043-Shoulder beam, 105-Suspension folding beam, 106-Second anchor point, 107-Elastic beam, 108-Extension beam, 1081-Vertical beam, 1082-Beam, 109-Deformation variable scale, 110- Pointer, 111 - Third Anchor Point, 201, 202 - Probe Station Probe, 300 - Thin Film Specimen.

FIG. 2 is a side view of the on-chip testing machine in the embodiment of the present invention.

3 is a schematic diagram of the displacement of each part of the on-chip testing machine in the embodiment of the present invention when the biaxial tensile test of the film is performed.

4A-4F are manufacturing flow charts of the on-chip testing machine in the embodiment of the present invention.

In the picture: 1-silicon wafer, 2-anchor point, 3-film sample, 4-glass piece, 5-anti-footing electrode, 6-movable structure.

Detailed ways

In order to make the technical solutions of the present invention more obvious and easy to understand, specific embodiments are given and described in detail below with reference to the accompanying drawings.

This embodiment discloses a system for biaxial tensile testing of nanoscale films, including an on-chip testing machine and a probe station for applying a load force to the on-chip testing machine. The on-chip testing machine includes two mutually perpendicularly arranged Tensile structure, these two tensile structures are exactly the same, but the direction is different, as shown in Figure 1 and Figure 2. One of the tensile structures will be mainly described below. For the same two specific structures in one tensile structure, only one of the structures will be marked. 1, each tensile structure includes a probe loading structure 101, two wheel-shaped loading reversing structures 102, a movable frame 104, an elastic beam 107, a tensile beam 108, two deformation variable scales 109, Two hands 110 and two hanging folding beams 105 .

Among them, the probe loading structure 101 is used for receiving the loading of the probe 201 of the probe station, and the probe loading structure 101 has a V-shaped loading port, which can ensure the accuracy of the loading position and the direction of the loading force. The two wheel-shaped loading reversing structures 102 are located on symmetrical sides of the probe loading structure 101, and both include a wheel-shaped structure 1021 and several spoke beams 1022, and opposite sides of the two wheel-shaped structures 1021 are connected to the probe loading structure 101. , the opposite sides are connected to the two forearm beams 1041 of the movable frame 104, the spoke beams 1022 connect the wheel-shaped structure 1021 to the first anchor point 103 of the wheel-shaped axis (the anchor point of diamond-shaped section), and the spoke beams 1022 wrap around The first anchor points 103 are evenly distributed in the circumferential direction. The movable frame 104 includes the two front arm beams 1041 extending toward the direction of the two wheel-shaped loading reversing structures 102 and two rear arm beams 1042 facing away from the direction. The distance between the two rear arm beams 1042 is narrower than the distance between the two front arms, The forearm beam 1041 and the rear arm beam 1042 on each side are connected and fixed by a shoulder beam 1043 perpendicular to it. The two forearm beams 1041 and the two rear arm beams 1042 are respectively symmetrically distributed. There are scales 108 of the two deformation variables. One end of the two suspension folding beams 105 is respectively connected to the shoulder beam 1043, and the other end is respectively fixed to the two second anchor points 106 (square section anchor points). The elastic beam 107 is vertically connected to the two rear arm beams 1042 of the movable frame, and has a certain elasticity. The tensile beam 108 includes a vertical beam 1081 and a transverse beam 1082, the vertical beam 1081 is arranged in parallel in the middle of the two rear arm beams 1042 of the movable frame 104, one end of which is connected to the middle of the elastic beam 107, and the other end is connected to a One side of the square film sample 300; the middle part of the beam 1082 is connected to the vertical beam 1081, and the two pointers 110 are provided at both ends. The two pointers 110 are respectively used to mark the scales of the two deformation scales 109 . The two adjacent sides of the film sample 300 that are not connected by the tensile beams 108 of the two tensile structures are respectively fixedly connected to the two third anchor points 110 (anchor points of rectangular cross-section). The four vertices of the square of the thin film sample 300 all contain the same triangular notches, and the shape is designed so that the inner test area is in a state of uniform stress and a high stress level. The thickness of the thin film sample 300 is in the order of nanometers, and the length and width are in the order of micrometers.

The arrows in Fig. 3 show the displacement directions of each part when the on-chip testing machine performs the biaxial tensile test of the film, taking one of the tensile structures as an example to illustrate. When the probe 201 is applied, the probe loading structure 101 is forced to move upward, the wheel-shaped loading reversing structure 102 on the left rotates counterclockwise, and the right one rotates clockwise, changing the moving direction, so that the movable frame 104 moves downward, and then The elastic beam 107 is driven to move downward, and the stretching beam 108 is further driven by the elastic beam 107 to stretch the lower edge of the film sample 300 . During the stretching process, the displacements of the tensile beam 108 and the rear arm beam 1042 are different, resulting in relative displacement, that is, the position indicated by the pointer 110 on the deformation variable scale 109 will change due to the relative displacement, and the reading of the deformation variable scale can reflect The amount of tensile force applied to the film sample. The greater the tensile force, the greater the relative displacement, and the greater the scale indicated by the pointer 110. By applying a load thrust to the tensile structure on the two axes, the readings of the two deformation variable scales when the film sample is broken are recorded. After processing the test data, the breaking of the film sample 300 on the two axes can be measured. stress data.

The manufacturing process of the on-chip testing machine of the above system is shown in Figures 4A-4F. The process adopted is based on the standard process of bonding deep etch release. The main steps include:

(1) As shown in Figure 4A, the silicon wafer 1 is an N-type single crystal silicon wafer with a thickness of 400 μm and a resistivity of 0.001 to 0.003 Ω·cm. The silicon wafer 1 and 4 μm are etched by ASE dry method, and steps are carved to form all the Anchor point 2, including the first anchor point, the second anchor point and the third anchor point;

Al在进行深刻蚀时对硅有足够高的选择比，湿法腐蚀Al，形成Al薄膜试样3；(2) As shown in FIG. 4B, Al is sputtered,

Al has a high enough selectivity ratio to silicon during deep etching, and Al is wet-etched to form Al thin film sample 3;

溅射Ti/Pt/Au，

剥离，形成防footing电极5，作用为在最后刻蚀时不会出现footing效应，保证刻蚀质量；(3) As shown in FIG. 4C, the glass sheet 4 is selected from B33, the thickness is 500 μm, and the BHF wet etching glass sheet 4,

Sputtering Ti/Pt/Au,

Peel off to form an anti-footing electrode 5, which is used to prevent the footing effect during the final etching and ensure the etching quality;

(4) As shown in FIG. 4D , the silicon wafer 1 and the glass wafer 4 are anodic bonded;

(5) KOH wet etching to thin the silicon wafer 5, the remaining thickness is 60±5μm;

(6) As shown in FIG. 4F , the silicon wafer 5 is deeply etched by the ASE dry method, and the movable structure and the thin film sample are released to obtain the entire on-chip testing machine structure.

The on-chip testing machine manufactured above was tested by a probe station. As shown in FIG. 1, the probe station probes 201 and 202 are used to apply load thrusts at the V-shaped loading ports of the probe loading structures 101 of the two tensile structures to push the wheel-shaped loading reversing structure to rotate (see FIG. 1). 3), so as to convert the pushing force into tensile force to pull the film sample, until the film sample is broken as observed by the optical microscope, and record the readings d ₁ and d ₂ of the deformation variable scale 109 of the two tensile structures at this time. Then the static simulation of the ANSYS finite element simulation tool can be used to obtain the biaxial stress inside the thin film sample when it breaks. The two ends of the thin film sample are connected with the anchor points of the rectangular section, so zero displacement constraints are imposed, and the other two ends are subjected to The biaxial uniform tensile force loads q ₁ and q ₂ can be calculated using equations (1) and (2):

Among them, E is the Young's modulus of single crystal silicon, l is the half length of the elastic beam, w is the width of the elastic beam, t is the thickness of the elastic beam, and A is the cross-sectional area of the thin film sample.

Repeating the above process for many times, by applying different load thrusts at the V-shaped loading ports of the probe loading structures 101 of the two tensile structures, the biaxial tension of the film sample when it breaks under different biaxial tensile force combinations can be obtained. Axial stress.

利用溅射方法制备的铝薄膜在断裂时内部的双轴应力。但需要说明的是，本发明方法适合提取经过其他加工工艺制造的纳尺度薄膜断裂时的双轴应力。本领域的技术人员应当理解，在不脱离本专利实质的范围内，保持本专利中利用片上试验机与微电子工艺检测分析用探针台相结合这个特征外，可对结构做一定的变化和修改，其制造方法也不限于本实施例中的制造流程。本发明的保护范围应以权利要求所述为准。An application of the method of the present invention is described above through an embodiment, that is, the extraction thickness is

Biaxial stress inside the aluminum film prepared by sputtering method at fracture. However, it should be noted that the method of the present invention is suitable for extracting the biaxial stress when the nanoscale films manufactured by other processing techniques are fractured. It should be understood by those skilled in the art that, within the scope of not departing from the essence of this patent, and maintaining the feature of combining the on-chip testing machine and the probe station for microelectronic process detection and analysis in this patent, certain changes and modifications to the structure can be made. Modification, its manufacturing method is also not limited to the manufacturing flow in this embodiment. The protection scope of the present invention should be based on the claims.

Claims (10)

1. A system for biaxial tensile testing of nanoscale films, comprising an on-chip testing machine and a probe station for applying a load force to the on-chip testing machine, wherein the on-chip testing machine comprises two mutually perpendicular Arranged tensile structures; each tensile structure includes a probe loading structure, two wheel-shaped loading reversing structures, a movable frame, an elastic beam, a tensile beam, two deformation variable scales, two pointers, and two suspensions Folding beam; wherein, the probe loading structure is used to undertake the probe loading of the probe station; the two wheel-shaped loading reversing structures are located on the symmetrical sides of the probe loading structure, and both include a wheel-shaped structure and a number of spoke beams. The opposite sides of the wheel-shaped structure are connected to the probe loading structure, and the opposite sides are connected to the two forearm beams of the movable frame, and the spoke beams connect the wheel-shaped structure to the first anchor point of the wheel-shaped axis; The moving frame includes the two forearm beams extending in the direction of the two-wheel-shaped loading reversing structure and two rear arm beams deviating from this direction, the rear ends of the two forearm beams and the front ends of the two rear arm beams are fixed to each other, and the two forearm beams and the two rear beam beams are fixed to each other. The rear arm beams are symmetrically distributed, and the two deformation variable scales are arranged on the inner sides of the rear ends of the two rear arm beams; one end of the two suspension folding beams is respectively connected to both sides of the movable frame, and the other end is respectively fixed to the two second anchor points The elastic beam is vertically connected to the two rear arm beams of the movable frame; the tensile beam includes a vertical beam and a cross beam, the vertical beam is arranged in parallel in the middle of the two rear arm beams of the movable frame, and one end thereof is connected to the elastic beam The middle part of the beam is connected to one side of a square film sample at the other end; the middle part of the beam is vertically connected to the vertical beam, and the two pointers are provided at both ends; the two pointers are used to mark the two pointers respectively. The scale of the deformation variable scale; the two adjacent sides of the film sample that are not connected by the tensile beams of the two tensile structures are fixedly connected to the two third anchor points respectively. 2. The system of claim 1, wherein the probe loading structure has a V-shaped loading port. 3. The system according to claim 1, wherein the distance between the two rear arm beams of the movable frame is narrower than the distance between the two forearms, and the forearm beam and the rear arm beam on each side pass perpendicular to it. A shoulder beam is connected, and one end of the suspended folding beam is specifically connected to the shoulder beam. 4. The system of claim 1, wherein the spoke beams of the wheel-shaped load reversing structure are uniformly distributed circumferentially about the first anchor point. 5. The system of claim 1, wherein two adjacent suspension folded beams of the two tensile structures are connected to the same second anchor point. 6. The system of claim 1, wherein the first anchor point is a diamond or circular section anchor point, the second anchor point is a square section anchor point, and the third anchor point is a rectangular section anchor point. 7 . The system of claim 1 , wherein the four vertices of the square of the thin film sample all contain the same triangular notches, and the shape is designed so that the inner test area is in a state of uniform stress and a high stress level. 8 . 8. A method of manufacturing a system for biaxial tensile testing of nanoscale films, comprising manufacturing a probe station and the on-chip testing machine according to any one of claims 1-7, wherein a method of manufacturing the on-chip testing machine Steps include: (1) using photolithography and etching to form a bonding anchor point on the front side of the silicon wafer, the anchor point includes a first anchor point, a second anchor point and a third anchor point; (2) depositing a thin film material on the front side of the silicon wafer, according to the plane shape and size of the thin film sample, using photolithography and etching or etching to form a thin film sample pattern; (3) Use photolithography and wet etching to form shallow grooves on the glass sheet, then sputter metal on the glass sheet, and then use a peeling process to form anti-footing metal electrodes; (4) anodic bonding the silicon wafer and the glass wafer processed through the above steps; (5) Use wet etching to thin the silicon wafer to the designed thickness; (6) Using photolithography and deep etching to partially etch through the silicon wafer from the back surface to release the movable structure and the thin film sample, the movable structure is the entire silicon structure except the anchor point, and the on-chip testing machine is obtained. 9 . The method of claim 8 , wherein the silicon wafer is an N-type single crystal silicon wafer with a resistivity of 0.001-0.003 Ω·cm; and three metals of Ti, Pt and Au are sputtered on the glass wafer. 10 . 10. The method of claim 8, wherein the silicon is dry-etched by ASE to form bonding anchors; and the thin film material is deposited on the front surface of the silicon wafer by PVD, CVD, ALD or electroplating.

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