Micro-beam bending strength online detection system based on thermal driving, manufacturing method and application

Abstract

The invention discloses a micro-beam bending strength online detection system based on thermal driving, a manufacturing method and application, and belongs to the field of micro-electro-mechanical systems. The online detection system comprises an on-chip testing machine and an on-chip tested sample, the on-chip testing machine mainly comprises a thermal driving loading actuator, a double-beam heat insulation structure, a V-shaped amplification lever, a region-of-interest positioning marking structure and a double-hammer structure, and the on-chip tested sample mainly comprises a rigid blocky structure, a bending test beam and an elastic suspension folding beam. According to the on-chip testing machine, energy loading and releasing are conducted by means of heating of the resistance beam of the on-chip testing machine, full-automatic online bending breaking strength detection and test result extraction after power-on can be achieved, and the on-chip testing machine can be used for monitoring the deep etching releasing technology and predicting the reliability of an MEMS device structure.

Description

Technical Field

[0001] The invention belongs to the field of micro-electromechanical systems (MEMS), and specifically discloses an online detection system for micro-beam bending strength based on thermal drive, a manufacturing method and an application thereof. Background Art

[0002] Micro-electromechanical system (MEMS) is an advanced technology that integrates microelectronics and mechanical engineering, and is mainly used to manufacture miniaturized sensors and actuators. Compared with traditional devices, MEMS devices have the advantages of small size, light weight, low energy consumption, small inertia, high resonant frequency, short response time, high sensitivity and easy integration. They are widely used in consumer electronics, automotive industry, chemical industry, medicine and even professional fields with extreme environments. Products manufactured based on this technology include pressure gauges, gyroscopes, catalytic sensors, electrostatic brake light projection displays, etc.

[0003] The deep etching and release (DRIE) process, one of the main means of manufacturing movable structures in MEMS technology, has different degrees of uneven etching surfaces in the actual manufacturing process. The existence of this phenomenon will directly lead to randomly distributed microcracks or microdamage defects on the side walls of the movable structure during the etching process, thereby affecting the actual fracture strength of the microstructure and causing more serious process reliability problems. Therefore, it is very important to extract the fracture strength of the microstructure manufactured by the DRIE process to achieve quality monitoring and reliability testing of the process. Among them, the bending fracture strength of the microbeam is one of the most important parameters.

[0004] At present, there are many common methods for extracting the bending fracture strength of materials, including the four-point bending test used in traditional off-chip testing machines and the equal-strength cantilever beam concentrated force bending used in on-chip testing machines. The traditional four-point bending test cannot achieve the fixation, clamping and loading of micron-scale structures, and the equal-strength cantilever beam concentrated force bending used in on-chip testing machines cannot accurately characterize the process quality of deep etching release because it cannot obtain the clear starting position of the etching crack (surface or inside the sample) through the test. At the same time, for the on-chip bending fracture strength test, the common loading method is to apply a displacement load through the probe station probe, which has positioning deviations and cannot rule out the possibility that accidental errors in the manual operation of the probe will cause significant damage to the device structure. The above methods all have certain limitations for the process quality monitoring of the deep etching process and the reliability prediction of the device structure, so it is necessary to propose a measurement method that can avoid the above-mentioned limitations. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention proposes an online detection system, manufacturing method and application of micro-beam bending strength based on thermal drive. The online detection system can be taped out together with functional devices to obtain test sample structures. The newly designed on-chip tester in the detection system relies on its own resistance beam heating to load and release energy, and can realize fully automatic online detection of bending fracture strength and test result extraction after power-on, which can be used to monitor deep etching release process and predict the reliability of MEMS device structure.

[0006] The present invention adopts the following technical solution:

[0007] A micro-beam bending strength online detection system based on thermal drive, comprising: an on-chip testing machine and an on-chip tested sample;

[0008] The on-chip test machine comprises: two heat-driven loading actuators, two double-beam heat-insulating structures, a V-shaped amplifying lever, an area of ​​interest positioning mark structure, a double hammer structure and two pairs of first fixed anchor points, all of which are symmetrical about the midline of the on-chip test machine; the heat-driven loading actuator is composed of a plurality of groups of parallel V-shaped heat-driven beams, the two ends of each group of V-shaped heat-driven beams are connected to a pair of first fixed anchor points, and the middle corners of each group of V-shaped heat-driven beams are connected to each other; one end of the double-beam heat-insulating structure is connected to the inner side of the middle corner of the V-shaped heat-driven beam, and the other end is connected to one end of the V-shaped amplifying lever; one side of the area of ​​interest positioning mark structure is connected to the middle part of the V-shaped amplifying lever, and the other side is connected to the double hammer structure; the double hammer structure comprises two conical hammers;

[0009] The on-chip test sample includes: two rigid block structures, a bending test beam, two elastic suspension folding beams, two third fixed anchor points, and two fourth fixed anchor points, all of which are symmetrical about the midline of the on-chip test sample; the two ends of the bending test beam are connected to the two rigid block structures and are opposite to the double hammer structure; the two third fixed anchor points are located on a side of the bending test beam away from the double hammer structure with a gap, and are located in the middle of the two conical hammers; one end of the elastic suspension folding beam is connected to the rigid block structure, and the other end is connected to the fourth fixed anchor point.

[0010] Furthermore, each heat-driven loading actuator is composed of 10 groups of V-shaped heat-driven beams with equal width, length and spacing.

[0011] Furthermore, the double-beam thermal insulation structure is composed of two slender beams parallel to each other, and the portion between the two slender beams is hollow.

[0012] Furthermore, the middle portion of the region of interest positioning mark structure contains three rectangular grooves of the same size and the same spacing.

[0013] Furthermore, the two conical hammer heads in the double hammer head structure are in an arc shape, and the groove portion between the two conical hammer heads is in an isosceles trapezoid shape.

[0014] Furthermore, the on-chip tester also includes two second fixed anchor points, which are located on two lateral sides of the double hammer structure.

[0015] Furthermore, the structural shapes of the first and fourth fixed anchor points may be square, rectangle or parallelogram; the structural shape of the second fixed anchor point is rectangular; the structural shape of the third fixed anchor point is an arc-shaped head and a rectangular tail.

[0016] Furthermore, the elastic suspension folding beam is composed of a plurality of elastic beams parallel to each other connected in series.

[0017] A method for manufacturing a micro-beam bending strength online detection system based on thermal drive, comprising the following steps of manufacturing an on-chip test machine:

[0018] Performing photolithography and anisotropic etching on the front side of the silicon wafer to form fixed anchor points, including first to fourth fixed anchor points;

[0019] Photolithography and wet etching are performed on the glass surface to form shallow grooves, and then metal is sputtered in the shallow grooves and the interconnection metal pattern is peeled off to obtain an anti-lateral drilling electrode;

[0020] Anodic bonding is performed on the silicon wafer and the glass wafer, and the anti-lateral drilling electrode on the glass is pressed into the fixed anchor point area of ​​the silicon wafer;

[0021] The back side of the silicon wafer is thinned by a wet etching process, and a SiO2 layer is deposited on the back side of the silicon wafer as a hard mask;

[0022] A groove structure having the same thickness as the hard mask is formed on the back side of the silicon wafer by photolithography and etching processes to serve as a silicon surface electrode region;

[0023] Depositing metal on the silicon surface electrode region to obtain a metal electrode, which serves as a voltage loading point for a heat-driven loading actuator;

[0024] Through photolithography and deep etching release processes, the movable structure is released to obtain an on-chip test machine.

[0025] Furthermore, the silicon wafer is an N-type single crystal silicon wafer with a resistivity of 0.001-0.003Ω·cm; three metals, Ti, Pt and Au, are sputtered in shallow grooves on the glass surface.

[0026] An application of a micro-beam bending strength online detection system based on thermal drive in the static four-point bending fracture strength detection of micro-beams includes the following steps:

[0027] The thermal drive loading actuator is powered on, and the thermal drive voltage is increased from 0V to the preset value in sequence to control the loading deflection of the double hammer structure; under different thermal drive voltages, static bending loading is performed on the bending test beam to observe the static bending deformation of the bending test beam;

[0028] If the bending test beam does not bend and break, first power off the thermal drive loading actuator. After the thermal drive loading actuator returns to room temperature, power on the hot zone loading actuator again until the bending test beam breaks successfully, and record the voltage value at this time.

[0029] The loading deflection is read by the image sub-pixel edge analysis measurement system, and the read loading deflection and the corresponding voltage value are brought into the COMSOL simulation model for simulation to obtain the static bending fracture strength of the bending test beam.

[0030] The beneficial effects achieved by the present invention are as follows:

[0031] 1) The online detection system of the present invention can eliminate the human-induced accidental error operation defects of the traditional four-point bending test beam and realize a new type of fully automatic test;

[0032] 2) The online detection system of the present invention avoids the error caused by the Joule heat generated when the thermal drive loading actuator end is powered on to the actual loading deflection by introducing a double-beam thermal insulation structure;

[0033] 3) The online detection system of the present invention directly realizes the reading of loading deflection by introducing a positioning mark structure of the region of interest through an image sub-pixel edge analysis measurement method, thereby improving the measurement accuracy;

[0034] 4) The online detection system of the present invention can achieve successful positioning and clamping of the tested sample on the loaded sheet by introducing a rigid block structure and an elastic suspension folding beam on both sides of the bending test beam;

[0035] 5) The online detection system of the present invention can perform a static four-point bending test on the bending test beam of the micro-scale structure;

[0036] 6) The online detection system of the present invention can perform process monitoring on the bending test beam and reliability prediction of the device structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a structural schematic diagram of an online detection system for micro-beam bending strength based on thermal drive in an embodiment of the present invention.

[0038] Description of reference numerals:

[0039] 1: Hot drive loading actuator;

[0040] 2: Double beam insulation structure;

[0041] 3: V-shaped amplification lever;

[0042] 4: Region of interest positioning marker structure;

[0043] 5: Double hammer structure;

[0044] 6: Rigid block structure;

[0045] 7: Bending test beam;

[0046] 8: Elastic suspension folding beam;

[0047] 9: first fixed anchor point;

[0048] 10: second fixed anchor point;

[0049] 11: the third fixed anchor point;

[0050] 12: Fourth fixed anchor point.

[0051] Figure 2 It is a side view of an online detection system for micro-beam bending strength based on thermal drive in an embodiment of the present invention.

[0052] Figures 3A-3H It is a manufacturing flow chart of the on-chip test machine in the embodiment of the present invention.

[0053] Description of reference numerals:

[0054] 31: Silicon wafer;

[0055] 32: Anti-lateral undermining electrode;

[0056] 33: Glass pieces;

[0057] 34: fixed anchor point;

[0058] 35: hard mask;

[0059] 36: silicon surface electrode area;

[0060] 37: Metal electrode;

[0061] 38: Movable structure. DETAILED DESCRIPTION

[0062] In order to make the above features and advantages of the present invention more obvious and easy to understand, the following embodiments are specifically cited and described in detail with reference to the accompanying drawings. Those skilled in the art can understand the structure, advantages and effects of the present invention from the contents disclosed in the following embodiments. The present invention can also be implemented or applied by other different specific examples, and the details in this specification can also be based on different viewpoints and applications, and various modifications and changes can be made to the details without departing from the concept and scope of the present invention.

[0063] This embodiment discloses an online detection system for micro-beam bending strength based on thermal drive, including: an on-chip testing machine and an on-chip tested sample, the structure of which is as follows: Figure 1 and Figure 2 shown.

[0064] The on-chip test machine includes: two heat-driven loading actuators 1, two double-beam insulation structures 2, a V-shaped amplification lever 3, a region of interest (RIO) positioning mark structure 4, a double hammer structure 5, two pairs of first fixed anchor points 9, and two second fixed anchor points 10. The overall structure of the on-chip test machine is symmetrical about the center line. For ease of description, the direction of the center line is called the vertical direction, and the perpendicular direction thereof is called the horizontal direction.

[0065] The thermal drive loading actuator 1 is composed of 10 groups of V-shaped thermal drive beams of equal width, length and spacing, all of which are in the micrometer range. The middle corners of each group of V-shaped thermal drive beams are connected to each other. In order to ensure that the output displacement of the thermal drive loading actuator 1 is always in the horizontal direction, two groups of thermal drive loading actuators 1 are symmetrically distributed on both sides of the on-chip test machine about the midline. The vertical ends of the thermal drive loading actuator 1 are connected to the two first fixed anchor points 9, and the inner side of the middle position is connected to the double-beam thermal insulation structure 2.

[0066] One side of the double-beam thermal insulation structure 2 is connected to the heat-driven loading actuator 1, and the other side is connected to the V-shaped amplifying lever 3. In order to avoid the error caused by the Joule heat generated when the heat-driven loading actuator 1 is powered on to the actual loading deflection of the V-shaped amplifying lever 3, the double-beam thermal insulation structure 2 is composed of two parallel slender beams, and the part between the two slender beams is hollowed out to avoid the generation of Joule heat.

[0067] The region of interest positioning mark structure 4 is connected to the lower side of the middle part of the V-shaped magnifying lever 3, and the middle of the region of interest positioning mark structure 4 contains three rectangular grooves of the same size and the same spacing. The lower side of the region of interest positioning mark structure 4 is connected to the double hammer structure 5. The double hammer structure 5 includes two arc-shaped conical hammers, and the groove part between the two conical hammers is in the shape of an isosceles trapezoid. In order to limit the lateral movement of the double hammer structure 5 during the movement process, two rectangular second fixed anchor points 10 are distributed on both sides of the structure.

[0068] The on-chip test sample includes: two rigid block structures 6, a bending test beam 7, two elastic suspension folding beams 8, two third fixed anchor points 11 and two fourth fixed anchor points 12, which are symmetrical about the midline of the on-chip test sample (coinciding with the midline of the on-chip test machine).

[0069] The bending test beam 7 is arranged horizontally, with the upper side facing the double hammer structure 5, and two third fixed anchor points 11 are symmetrically distributed on the lower side and located in the middle of the two conical hammers. When the double hammer structure 5 is not driven, there is a gap between the double hammer structure 5 and the bending test beam 7, and there is a certain gap between the bending test beam 7 and the third fixed anchor point 11. The structural shape of the third fixed anchor point 11 is an arc-shaped head and a rectangular tail. A rigid block structure 6 is connected to each of the two lateral ends of the bending test beam 7. The elastic suspension folding beam 8 is a plurality of repetitive reciprocating structures formed by connecting a plurality of parallel elastic beams in series, the upper end of the elastic suspension folding beam 8 is connected to the rigid block structure 6, and the lower end is connected to the fourth fixed anchor point 12. The design of the rigid block structure 6 and the elastic suspension folding beam 8 can realize the positioning and clamping of the bending test beam 7 on the sheet.

[0070] This embodiment also discloses a method for manufacturing a micro-beam bending strength online detection system based on thermal drive, which mainly includes the steps of manufacturing an on-chip test machine. The manufacturing process is as follows: Figures 3A-3H As shown, the process used is based on the standard bond deep etch release process, and the main steps include:

[0071] (1) Figure 3A As shown, the silicon wafer 31 is an N-type single crystal silicon wafer with a resistivity of 0.001-0.003Ω·cm and a thickness of 400μm. The silicon wafer 31 is anisotropically etched by photolithography and ASE with an etching depth of 4μm (in other embodiments, the etching depth can be selected in the range of 4-12μm according to actual needs) to form a step, thereby forming an anchor point 34 on the front side of the silicon wafer 31, including the first to fourth fixed anchor points.

[0072] (2) Figure 3B As shown, the glass sheet 33 is made of 7740 with a thickness of 500±10μm. A shallow groove is prepared on the surface of the glass sheet 33 by photolithography and BHF wet etching process. The depth of the shallow groove is PVD sputtered metal Ti / Pt / Au, thickness The interconnect metal pattern is defined by a lift-off process to prepare an anti-lateral footing electrode 32.

[0073] (3) Figure 3C As shown, the obtained silicon wafer 31 and glass wafer 33 are anodically bonded, and the anti-lateral undercutting electrode 32 on the glass wafer 33 is pressed into the anchor point 34 area.

[0074] (4) Figure 3D As shown, the back side of the silicon wafer 31 is thinned by a KOH wet etching process, and the remaining thickness is 60 μm.

[0075] (5) Figure 3EAs shown, a layer of SiO2 film is PVD sputtered on the back of the silicon wafer 31 as a hard mask 35, and its thickness is To ensure the loading of large current.

[0076] (6) Figure 3F As shown, a groove structure having the same thickness as the hard mask 35 is formed on the back side of the silicon wafer 31 by combining photolithography, dry etching and wet etching to serve as a silicon surface electrode region 36 .

[0077] (7) Figure 3G As shown, metal aluminum is deposited on the silicon surface electrode region 36 to form a metal electrode 37, which serves as a voltage loading point of the thermal drive loading actuator 1. The thickness of the electrode metal 37 is About, refer to the actual thickness of the hard mask 35 mentioned above.

[0078] (8) Figure 3H As shown, the structure is released by photolithography and DRIE dry etching process to obtain a suspended movable structure 38, which is each structure except the anchor points in the on-chip test machine and the on-chip test sample.

[0079] This implementation case also discloses an application of an online detection system for micro-beam bending strength based on thermal drive, which is used to detect the static four-point bending fracture strength of the micro-beam, and includes the following steps:

[0080] 1) The thermal drive loading actuator is powered on through the silicon surface electrode area, and the thermal drive voltage is increased from 0V to the corresponding design value (the thermal drive voltage range is within 0 to 10V), thereby controlling the loading deflection of the double hammer structure;

[0081] 2) Under different thermal drive voltages, static bending loading is performed on the bending test beam to observe the static bending deformation of the bending test beam;

[0082] 3) If the bending test beam does not bend and break, first power off the thermal drive loading actuator, wait for the thermal drive loading actuator to return to room temperature, that is, after the system is adjusted to be stable, power on the thermal drive loading actuator again, and the thermal drive voltage changes by 0.5V each time until the bending test beam breaks successfully, and record the voltage value at this time;

[0083] 4) The loading deflection under the corresponding voltage is read by the image sub-pixel edge analysis measurement system, and the loading deflection and the corresponding voltage value obtained above are brought into the established mechanical-electrical-thermal coupling integrated model, and the whole process of static four-point bending is simulated in COMSOL simulation software, so as to obtain the deformation of the bending test beam corresponding to different voltage values ​​and different loading deflections and its corresponding static bending fracture strength. In this example, the static bending fracture strength of the bending test beam is about 1.2Gpa.

[0084] The present invention adds a detection area containing the system on a silicon wafer with functional devices, and manufactures the functional devices and the detection system through an improved SOG (silicon on glass) process. After the overall process is completed, the static four-point bending fracture strength of the sample is tested by the system to obtain the process-related mechanical characteristic parameters of the functional device in real time and online.

[0085] The above embodiments are only used to describe the technical solution of the present invention, but not to limit it. The structural features and characteristics that belong to common knowledge are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical concept of the present invention, several deformations and improvements can be made to the structure of the on-chip test machine, which should also be considered to be included in the protection scope of the present invention. The protection scope of the present invention shall be based on the scope defined by the claims.

Claims

1. An online detection system for micro-beam bending strength based on thermal drive, characterized in that: include: On-chip tester and on-chip test sample; The on-chip test machine comprises: two heat-driven loading actuators, two double-beam heat-insulating structures, a V-shaped amplifying lever, an area of ​​interest positioning mark structure, a double hammer structure and two pairs of first fixed anchor points, all of which are symmetrical about the midline of the on-chip test machine; the heat-driven loading actuator is composed of a plurality of groups of parallel V-shaped heat-driven beams, the two ends of each group of V-shaped heat-driven beams are connected to a pair of first fixed anchor points, and the middle corners of each group of V-shaped heat-driven beams are connected to each other; one end of the double-beam heat-insulating structure is connected to the inner side of the middle corner of the V-shaped heat-driven beam, and the other end is connected to one end of the V-shaped amplifying lever; one side of the area of ​​interest positioning mark structure is connected to the middle part of the V-shaped amplifying lever, and the other side is connected to the double hammer structure; the double hammer structure comprises two conical hammers; The on-chip test sample includes: two rigid block structures, a bending test beam, two elastic suspension folding beams, two third fixed anchor points, and two fourth fixed anchor points, all of which are symmetrical about the midline of the on-chip test sample; the two ends of the bending test beam are connected to the two rigid block structures and are opposite to the double hammer structure; the two third fixed anchor points are located on a side of the bending test beam away from the double hammer structure with a gap, and are located in the middle of the two conical hammers; one end of the elastic suspension folding beam is connected to the rigid block structure, and the other end is connected to the fourth fixed anchor point.

2. The micro-beam bending strength online detection system based on thermal drive according to claim 1 is characterized in that: Each heat-driven loading actuator is composed of 10 groups of V-shaped heat-driven beams with equal width, length and spacing.

3. The micro-beam bending strength online detection system based on thermal drive according to claim 1 is characterized in that: The double-beam insulation structure is composed of two slender beams parallel to each other, and the part between the two slender beams is hollow.

4. The micro-beam bending strength online detection system based on thermal drive according to claim 1 is characterized in that: The middle portion of the region of interest positioning marker structure contains three rectangular grooves of the same size and the same spacing.

5. The micro-beam bending strength online detection system based on thermal drive according to claim 1 is characterized in that: The two conical hammer heads in the double hammer head structure are in arc shape, and the groove part between the two conical hammer heads is in an isosceles trapezoid shape.

6. The micro-beam bending strength online detection system based on thermal drive according to claim 1 is characterized in that: The on-chip tester also includes two second fixed anchor points located on two lateral sides of the double hammer head structure.

7. The micro-beam bending strength online detection system based on thermal drive according to claim 1 is characterized in that: The elastic suspension folding beam is composed of a plurality of elastic beams which are parallel to each other and connected in series.

8. A method for manufacturing a micro-beam bending strength online detection system based on thermal drive according to any one of claims 1 to 7, characterized in that: The steps of manufacturing a test-on-chip machine include: Performing photolithography and anisotropic etching on the front side of the silicon wafer to form fixed anchor points, including first to fourth fixed anchor points; Photolithography and wet etching are performed on the glass surface to form shallow grooves, and then metal is sputtered in the shallow grooves and the interconnection metal pattern is peeled off to obtain an anti-lateral drilling electrode; Anodic bonding is performed on the silicon wafer and the glass wafer, and the anti-lateral drilling electrode on the glass is pressed into the fixed anchor point area of ​​the silicon wafer; The back side of the silicon wafer is thinned by a wet etching process, and a SiO2 layer is deposited on the back side of the silicon wafer as a hard mask; A groove structure having the same thickness as the hard mask is formed on the back side of the silicon wafer by photolithography and etching processes to serve as a silicon surface electrode region; Depositing metal on the silicon surface electrode region to obtain a metal electrode, which serves as a voltage loading point for a heat-driven loading actuator; Through photolithography and deep etching release processes, the movable structure is released to obtain an on-chip test machine.

9. The manufacturing method according to claim 8, characterized in that: The silicon wafer is an N-type single crystal silicon wafer with a resistivity of 0.001-0.003Ω·cm; three metals, Ti, Pt and Au, are sputtered in shallow grooves on the glass surface.

10. An application of the micro-beam bending strength online detection system based on thermal drive according to any one of claims 1 to 7 in the detection of static four-point bending fracture strength of micro-beams, comprising the following steps: The thermal drive loading actuator is powered on, and the thermal drive voltage is increased from 0V to the preset value in sequence to control the loading deflection of the double hammer structure; static bending loading is performed on the bending test beam under different thermal drive voltages to observe the static bending deformation of the bending test beam; If the bending test beam does not bend and break, first power off the thermal drive loading actuator. After the thermal drive loading actuator returns to room temperature, power on the hot zone loading actuator again until the bending test beam breaks successfully, and record the voltage value at this time. The loading deflection is read by the image sub-pixel edge analysis measurement system, and the read loading deflection and the corresponding voltage value are brought into the COMSOL simulation model for simulation to obtain the static bending fracture strength of the bending test beam.

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