JP2022080357A - Pressure stage using pneumatic pressure bellows - Google Patents

Abstract

To provide a submicron accuracy 6 degree of freedom pressure stage which does not include a parallel link mechanism using a pressurized air pressure bellows and a sliding part with optical non-contact attitude measurement, is excellent in the cleanliness and has 1,000 N or greater of thrust in order to solve such a problem that an elastic deformation due to pressure accumulates on a conventional multi-axis stage in a semiconductor junction device which requires precise alignment, and lubrication oil required for a sliding portion causes contamination of a junction interface.SOLUTION: Six or more pneumatic bellows are directly connected to the stage, the bellows having the small diameter is used for horizontal positioning, and the bellows having the large diameter is vertically installed to secure the pressure thrust. The rigidity of the stage is adjusted with the number of crests and plate thickness of the bellows, the bellows thrust with the pneumatic pressure is aligned with a necessary stage movement distance. The high-speed attitude measurement with the submicron accuracy is performed with laser interferometer measurement and microscopic image processing using convergent light, and the stage control is performed with the parallel pressure feedback to the plurality of bellows.SELECTED DRAWING: Figure 1

Description

The present invention relates to a pressurization stage using a pneumatic bellows, and particularly to a submicron precision pressurization alignment mechanism including a tilt required for a wafer joining device or a nanoimplant device in the field of semiconductor manufacturing, for example.

In recent years, in the wafer bonding process required for manufacturing 3D ICs, it is necessary to adjust the relative positional deviation of the wafer on the submicron order at a high temperature of about 400 ° C. and then pressurize ton-order. Further, an infrared imaging chip using a hetero semiconductor material requires a process of high-density bonding of an infrared photodiode array and a readout IC at a chip level with a pixel pitch of a dozen μm. In the above joining process, heating (~ 300 ° C), pressurization (~ 1,000N) or ultrasonic application is performed while controlling not only the horizontal position but also the parallelism (gap) between the wafers in a clean atmosphere. There is a need.

For example, in a chip-level bonding process for manufacturing a VGA (640x520 pixel) infrared image sensor with a chip area of about 1 cm ² , alignment accuracy ± 1 micron and parallelism ± 100 microradians (□ 1 cm 2 gaps at both ends of the chip). The difference is within 1 μm), and it is necessary to pressurize several hundred N and apply ultrasonic waves. (Non-Patent Document 1)

In the conventional joining device configuration, a pneumatic actuator using a torque control AC servomotor or an air cylinder has been used as a vertical drive mechanism, and a bearing stage has been used as a horizontal drive mechanism. For example, in the AC Servo Actuator, Jameme Sewing Industry Co., Ltd., located at 1463 Hazamamachi, Hachioji-shi, Tokyo, is developing a precision pressurization control servo press device with a pressurization capacity of up to 30 kN. As for pneumatic actuators, Sumitomo Heavy Industries, Ltd., located at 2-1-1 Osaki, Shinagawa-ku, Tokyo, produces a mechanism with a positioning control mechanism on a pneumatic cylinder using air bearings under the trademark "Airsonic". ing. (Patent Document 1)

As a joining device for electronic components and semiconductor modulars, a cross roller guide is used as a means of alignment in the plane direction for the Adwells FA1000 ultrasonic high-precision flip-tip bonder located at 8-140 Katanawa, Nakagawa City, Fukuoka Prefecture. Using the X, Y stage and rotation mechanism used, a pneumatic actuator using an air cylinder is used in the Z direction. In addition, the WI-1000 type vacuum wafer joining device of Bondtech Co., Ltd. located at 77 Kisshoin Ishihara Nishimachi, Minami-ku, Kyoto Prefecture, uses an electric linear actuator in the Z direction. The Z-direction actuator is provided with a linear encoder and a strain gauge to ensure submicron-accuracy positioning accuracy. (Patent Document 2)

As a mechanism for maintaining parallelism between chips or wafers, for example, a spherical bearing type copying mechanism manufactured by Adwells or a piezo stage manufactured by Bondtech Co., Ltd. is used. It is used for joining. However, the copying mechanism has problems of accuracy of copying operation and change with time. Further, since the piezo stage has a short stroke (up to several tens of μm), it is necessary to combine it with a conventional mechanical coarsening mechanism that combines a bearing stage with a roller or a ball screw. In particular, in high temperature and high load equipment in a clean atmosphere, which is required for semiconductor process equipment, it is complicated to deal with the heat resistance and load bearing of the piezo element, and the prevention of contamination by the lubricating oil required for the bearing stage. become.

In a conventional serial link stage in which a linear or rotary stage using a bearing guide and a ball screw is superposed for the required degree of freedom, an elastic deformation of about 1 μm is unavoidable on each axis due to a radial or axial load of about 1,000 N. For example, when compression or tensile stress is applied to the roller guide stage, deformation of about 0.5 μm / 1,000 N occurs. (Non-Patent Document 2) The deformation rate of a ball screw or a roller screw with higher rigidity used as a feed screw mechanism used to drive a stage is 1 μm / 1,000 N even when a relatively large lead screw with a shaft diameter of 40 mm is used. It becomes more than a degree. (Non-Patent Document 3)

It is possible to reduce hysteresis such as backlash by using an optical linear or rotary encoder for each axis and improve the repetitive positioning accuracy to the submicron level, but due to the moment load that cannot be grasped by the measurement of each axis. Twisting (yawing, pitching, rolling) of each axis is assumed. In the stage for precision alignment, control of 3 axes (x, y, z) in the vertical and horizontal directions, rotation (θ: yawing) and tilting (α: rolling, β: pitching) in total 6 axes including parallelism. Needs. In the serial link stage, elastic deformation due to pressurization accumulates between the six drive mechanisms, causing a positional shift of several μm that cannot be grasped at each axis level. Therefore, in order to secure the positioning accuracy of the submicron under the load application condition, it is necessary to measure the spatial absolute coordinates of the target stage and perform feedback control.

In the control method of the multi-axis stage, the 6-axis stage using the parallel mechanism is called the Stewart platform or Hexapod, and has been put into practical use as a highly rigid 6-axis stage. In this case, six variable length rods hold the stage via a ball joint or a universal joint. Hexapods have a limited stroke compared to bearing-type stages, but by controlling the lengths of the six rods that support the stage in parallel, displacement errors at the link connection and backlash errors. The position and tilt of the stage can be set promptly without the accumulation of. The length of the six arms and the stage position coordinates are represented by polynomial functions including trigonometric functions, but with the development of computers and software, the calculation of the arm length required to move to the desired stage position (reverse kinematics) Is no longer a major obstacle.

However, even if the length of each of the six rods can be controlled with submicron accuracy by using a linear actuator with an optical linear scale, it is difficult to maintain the stage position with submicron accuracy. This is because it is difficult to suppress the elastic deformation of the rod and the joint portion to the submicron level or less under a load condition of about 1,000 N. Further, the backlash of the joint portion causes hysteresis at the time of switching the expansion and contraction, so that it is necessary to apply a pressurization, but the lubricity and the load range are restricted. Therefore, in order to obtain a large load and submicron level stage accuracy, it is necessary to measure the absolute coordinates of the target stage and perform feedback control as in the serial link stage.

Robot hands that have appropriate strength and structural softness and can operate with delicate force are required for medical use and semiconductor processing equipment.
The pneumatic drive mechanism is suitable for force control (Stiffness Control) because it generates a driving force proportional to the pressure. Since the pneumatic drive mechanism has less contamination and a simple structure, a manipulator with a parallel mechanism using a pneumatic cylinder and a ball joint has been manufactured for medical use. In particular, the upper limit of thrust is determined by the supply pressure, so safety is high. (Non-Patent Document 4)

With a similar mechanism, a 6-axis stage (Hexapod) using a pneumatic cylinder and a universal joint can be easily envisioned. However, in the case of a pneumatic cylinder, if an air bearing is used to reduce sliding friction, an air gap of a dozen μm is formed and the rigidity in the direction perpendicular to the axis is lowered. Further, it is necessary to use a universal ball joint using a bearing for the joint portion or a ball joint having a sliding surface, which deteriorates environmental resistance such as elastic deformation and high temperature.

Pneumatic bellows, like pneumatic cylinders, have the ability to convert pressure into force or displacement. In addition, the bellows does not require a ball joint or a universal joint because it has a spring action even when displaced in the axial direction. Since it does not have a sliding mechanism in the axial direction, hysteresis due to friction does not occur. Usually, in order to avoid buckling, an exoskeleton or an endoskeleton is used in combination, and the skeleton is used under tension. (Non-Patent Document 5) A drive mechanism for force control that imitates a living body is called soft robotics, and is becoming a major field of robot research. (Non-Patent Document 6)

For applications in the semiconductor field, a pressurizing mechanism using a pneumatic bellows and an elastic hinge has also been proposed. By arranging an elastic hinge around the pneumatic bellows, the displacement direction is limited only to the axial direction of the pneumatic bellows without a sliding mechanism such as a cylinder, and by incorporating a linear encoder, load cell, etc. , Longitudinal positioning is possible. (Patent Document 3) By attaching this uniaxial pneumatic actuator to three stages perpendicular to the axial direction, it is possible to drive up and down and tilt. Further, a stage capable of rotation is shown in addition to the above-mentioned vertical and tilting drive by combining three orthogonal two-axis actuator units. (Patent Document 4)

The inventors have achieved an accuracy of several tens of nm by combining a high-precision and high-speed position sensor and a linear pneumatic servo valve with high-speed response characteristics in a uniaxial pneumatic positioning mechanism using a metal molded bellows and an elastic hinge. did. In this method, the pressure supplied to the flexible bellows is feedback-controlled by an electropneumatic actuator using position information from an optical linear scale or a laser interferometer. In this system, the pressure-displacement characteristic of the stage is set to about 300 [㎛] for a differential pressure of 400 [kPa]. At this time, the natural frequency formed by the mass of the moving part and the spring constant of the hinge is about 60 [Hz]. Position measurement is performed with a cycle of 0.1 msec using a laser interferometer (RLU10 manufactured by Renishaw), the control signal is calculated by the measurement control software MATLAB Simulink xPC Target, and the electropneumatic system uses a nozzle flapper type 3-way servo valve with a 16-bit DAC. Output to the actuator. (Non-Patent Document 7)
Furthermore, a low fluid noise servo valve using a voice coil motor with low hysteresis was adopted to improve the pressure control characteristics. The static position accuracy reaches 1 nm for the stage stroke of ± 1250 μm. (Non-Patent Document 8)

Metal molded bellows are usually manufactured by deforming a thin metal plate such as stainless steel into a corrugated shape, but there are some restrictions due to its structure. One is the expansion / contraction stroke, which should be set within ± several% of the natural length from the viewpoint of life. Another constraint is buckling, which causes deformation at right angles to the axial direction above a certain pressure. The pressure P _cr at which buckling occurs is generally expressed by Eq. 1). (Non-Patent Document 9)
P _cr = 2π f _i / (N ² q) ・ ・ ・ Equation 1)
However, f _i is the elastic modulus per bellows, N is the number of bellows, and q is the pitch per bellows.

That is, the critical pressure is proportional to the elastic modulus per mountain and inversely proportional to the square of the number of mountains. The elastic modulus per pile of bellows is proportional to the circumference and proportional to the cube of the plate thickness of bellows. Since the thrust is proportional to the effective area of the bellows, the thrust at the buckling limit is roughly proportional to the cube of the bellows diameter and the bellows plate thickness. Therefore, it is important to adjust the plate thickness, bellows diameter, and number of peaks (bellows length) while considering the required stroke, buckling limit, and spring constant for stable stage drive using metal molded bellows. ..

Regarding the minimum stroke required for joining the wafer or chip, the positional deviation at the start of alignment is about 200 μm from the positioning accuracy of the transfer robot, and the stroke required for joining is about several mm for securing a gap during transfer of the wafer. Therefore, by using a metal molded bellows having a natural length of about 100 mm, a stroke of several mm required for the joining device can be secured.

In the joining process, after positioning, pressurization is performed while monitoring the misalignment. First, in the positioning process, the stage position is determined by the balance condition between the thrust due to the air pressure supplied to the bellows and the spring action of the bellows or the springs installed in parallel. In order to ensure positioning accuracy, the rigidity of the stage is adjusted by bellows and springs, and the range and accuracy of the air pressure that can be controlled by the electropneumatic actuator match the stage position and accuracy, and then the required pressurization direction is used. It is necessary to secure the thrust.

In recent non-contact optical distance measurement systems, products have been announced that allow an angular deviation of the target surface of about ± 0.3 to ± 3 ° or more instead of limiting the measurement span to several mm. For example, an optical fiber interference distance meter (attocube, IDS3010, Eglfinger Weg 2, using convergent light and the reflection intensity vibration principle of a Fabry-Perot type resonator formed between the end face of the optical fiber collimator and the target surface)
85540 Haar, Germany) and a multi-color laser coaxial displacement meter (Keyence, CL-3000 series, 1-3-14 Higashinakajima, Higashiyodogawa-ku, Osaka) using chromatic aberration of the lens are on the market, and the stage is precisely adjusted. If the range is the range of position and angle adjustment associated with the alignment process, the position information (x, y, z, θ, α, β) of the stage as a rigid body is measured with submicron accuracy and at time intervals of 0.1 msec or less. can do.

Pneumatic control systems need to control pressure at a speed sufficiently faster than the system's natural frequency. In order to avoid hysteresis due to magnetic materials, nozzle flapper valves and linear linear acting valves using air-core solenoids are available from MOOG (400 Jamison Road Elma, New York, 14059 USA) and 241-1 Hirako-cho, Owariasahi-shi, Aichi. Developed by the company, a product with a cutoff frequency of about 400Hz has been put on the market.

As mentioned above, in the parallel link system system, inverse kinematic control by a computer is required, but due to the development of robot-related technology and 3D measurement technology, it is mechanically simpler and more accurate than the conventional serial link stage. An environment is being set up to realize a system with excellent output load. Also, in the field of soft robotics where the force can be adjusted, the air pressure control method with excellent safety and cleanliness is attracting attention.

Japanese Unexamined Patent Publication No. 2004-144196 Japanese Patent Application Laid-Open No. 2007-141972 Japanese Unexamined Patent Publication No. 2014-199106 Japanese Unexamined Patent Publication No. 2014-199215

Mutsuro Ogura, Katsuhiko Nishida, Hironobu Murai, "High resolution, wide dynamic range USB3 Vision compatible InGaAs near infrared camera" Video Information Industrial February 2017 p.21-24. Atsushi Matsumoto Soichiro Kato "Characteristic Analysis of Linear Guides for Machine Tools" Proceedings of the 2004 Annual Meeting of the Japan Society for Precision Engineering Spring Conference A75 Jiro Otsuka, Takashi Osawa, Shigeo Fukada "Study on Planetary Roller Screws" Journal of Precision Engineering JSPE-53-08 '87 -08-1203 Yasuhiro Hayakawa, Sadao Kawamura, Takeo Goto, Katsuaki Nagai "Development of a rotary drive mechanism for a robot manipulator using a pneumatic bellows with a sensing function" Journal of the Robotics Society of Japan, Vol. 14, No. 2 (March 1996) Kiyohito Shimizu, Shinichi Hirai, Sadao Kawamura "Prototype of Bellows Tube Pneumatic Group Actuator" 19th Robotics Society of Japan Academic Lecture (September 18-20, 2001) 1G1 Aaron Fishman1, Martin Stephen Garrad, Andrew Hinitt1, Plinio Zanini, Tim Barker and Jonathan Rossiter'A Compliant Telescopic Limb with Anisotropic Stiffness', Front. Robot. AI, 01 February 2017 | https://doi.org/10.3389/frobt. 2016.00080 Toshinori Fujita, Kazutoshi Sakaki, Satomi Miyazaki, Keiichi Miyazaki "Control method and nanopositioning of fine movement stage driven by pneumatic bellows" Proceedings of Japan Fluid Power Systems Society September 2017 Toshinori Fujita "Ultra-precision positioning technology by pneumatic servo control for the semiconductor industry" Measurement and control Vol. 54, No. 9, September 2015 EJMA "Standards of The Expansion Joint Manufacturers Association, Inc." Eighth Edition EXPANSION JOINT MANUFACTURERS ASSOCIATION, Aug. 1, 200

In view of the problems in each of the above-mentioned conventional examples, the present invention realizes a high-precision 6-axis pressurizing stage having excellent cleanliness and environmental resistance without including a sliding portion by a parallel link mechanism using a pneumatic bellows. .. At that time, the bellows are spatially arranged in consideration of the buckling limit, and a configuration that satisfies the alignment accuracy, stroke, and load required for the semiconductor wafer or the semiconductor chip joining device is clarified by using a relatively inexpensive metal molded bellows. ..

In stage control assuming a submicron level and pressurization of about 1,000 N or more, it is necessary to consider all the components as elastic bodies and consider the elastic strain due to the load. Therefore, in order to control the spatial position and orientation on the submicron order, feedback control based on the three-dimensional spatial measurement of the stage is required for any stage configuration. In the present invention, a serial link having a conventional feedback mechanism for each axis by feedback-controlling the air pressure in parallel at a sufficiently fast measurement interval for a plurality of metal flexible bellows having both a spring action and a pneumatic cylinder action. Achieves higher rigidity and controllability.

Metallic flexible bellows have the potential for buckling, which is facilitated by tilting and lateral loading. Normally, an exoskeleton or an endoskeleton is used in combination to avoid buckling, but at that time, since a movable joint portion is involved, contamination by lubricating oil, deformation of bearings, or hysteresis due to backlash occurs. Therefore, it is necessary to design so that buckling does not occur in the operating range without using the movable joint portion. Further, since the buckling limit pressure condition becomes low when a load orthogonal to the axial direction of the bellows is applied, it is desirable that the stage is driven along the bellows axis.

The thrust generated in the bellows is the value obtained by multiplying the effective area of the bellows by the air pressure applied. For example, when 1 atmosphere of air is applied to a bellows having a cross-sectional area of 100 cm ² , the thrust becomes approximately 1,000 N. In the Weber joining device, the main required load is the vertical (y) direction, which is necessary for alignment adjustment in the horizontal (x, z), rotation (θ: yawing) and tilting (α: rolling, β: pitching) directions. The load is only enough to correct the stress component due to the angle deviation in the vertical direction, and is estimated to be about 1/100 to 1/1000 of the vertical load. Further, in order to realize the alignment adjustment accuracy at the submicron level, it is advantageous to reduce the diameter of the bellows and reduce the driving force generated with respect to the air pressure which is a control parameter. Therefore, in order to secure the alignment accuracy while ensuring the compressive thrust at the time of joining, it is effective to make the diameter of the bellows driven in the vertical direction larger than that of the bellows driven in the horizontal direction or the rotational direction.

The range of air pressure that can be controlled by the electropneumatic actuator is approximately -0.5 to 3 atm, and the upper limit is the buckling limit pressure of the bellows. In general, the analog amount setting is limited to a resolution of about 14 to 16 bits (16,384 to 65,536). Therefore, as the pressure response of the stage for realizing the stage position control with submicron accuracy, about 1 mm / atmospheric pressure is appropriate. In addition, the thrust in the vertical direction needs to be about 1,000 N / atmospheric pressure. Therefore, in addition to the diameter of the bellows, it is necessary to optimally design the thickness, shape, natural length, presence / absence of juxtaposed springs, etc. of the bellows. At that time, it is desirable to independently control the positioning that requires accuracy and the elevating function that requires thrust.

When the stage is regarded as a rigid body, its degrees of freedom are 6 axes (x, y, z, θ, α, β), so in order to measure the position and angle of the stage, use a distance meter. The distance between the side of the rigid body (stage) and the support (frame) may be measured at three points in the horizontal direction and three points in the side direction. In the joining process, it is necessary to evaluate and minimize the relative misalignment of the two chips. In particular, the misalignment during pressurization causes a decrease in yield. Therefore, it is necessary to calculate the misalignment of the alignment mark by image processing and perform stage position correction in real time including pressurization.

When carrying in the sample, a gap of about several mm is required to allow the robot hand to be inserted. On the other hand, the range required for precise alignment depends on the positioning accuracy of the chip transfer robot or the like, but is within ± 200 μm. The initial parallelism of the weber can also be within ± 1/1000 radians (~ 0.06 °). Therefore, it is possible to limit the working distance range to about 1 mm in the highly accurate spatial distance measurement required for alignment.

In order to achieve the above object, the present invention uses a plurality of pneumatic bellows, and controls the air pressure introduced into the bellows with positive and negative pressures within a range in which buckling does not occur in the bellows, thereby forming a cylinder, a ball joint, or the like. It is a pressure stage using a pneumatic bellows that controls the spatial posture and thrust without using the sliding part of.
We propose a 6-axis pressurizing stage characterized in that the effective cross-sectional area, elastic constant and natural length of the bellows are changed according to different thrusts and strokes corresponding to the specifications of vertical, horizontal and rotational directions.

After satisfying these basic configurations, the present invention further
By installing the bellows with a large effective area in the vertical direction and installing the bellows with a small effective cross-sectional area in the horizontal direction of the stage or shallowly with respect to the horizontal plane, the thrust in the vertical direction is secured and the positioning accuracy is improved. The pressurizing stage according to claim 1, wherein the pressurizing stage is also proposed.

Also in the present invention, after satisfying the above basic configuration, the bellows having a number of pneumatic bellows more redundant than the degree of freedom of the stage, the tensile stress is applied to the bellows having a small effective cross-sectional area, and the compressive stress is applied to the bellows having a large effective cross-sectional area. The pressurizing stage according to claim 1, wherein the bellows is prevented from buckling while increasing the vertical thrust.

Also in the present invention, after satisfying the above basic configuration, the stage has more bellows than the degree of freedom 6 when the stage is regarded as a rigid body, and the surface distribution of the pressure thrust of the stage is adjusted. The pressurizing stage according to claim 1 is also proposed.

Further, in the present invention, the position and orientation of the stage in the three-dimensional space including the center coordinates, rotation, and tilt are detected by the non-contact position sensor, and pressure positioning is performed by controlling the pressure supplied to the pneumatic bellows. The pressurizing stage according to claim 1 is also proposed.

In the conventional drive mechanism using a ball screw and a bearing stage, a sliding portion exists regardless of the serial link or the parallel link, and the use of lubricating oil is unavoidable. The metal molded bellows used in the present invention has the characteristics of a pneumatic cylinder and an elastic hinge, and has no sliding portion. Therefore, there is no dust generation due to friction and no contamination by lubricating oil. The metal molded bellows is also a product used for vacuum piping, and has excellent cleanliness and heat resistance.

The pressurizing device requires sufficient thrust in the vertical direction, while it requires submicron level accuracy in the horizontal and tilting directions. On the other hand, the set air pressure is appropriately set in the range of -0.5 atm to 3 atm (0.3 MPa) in consideration of the buckling of the bellows, the air source pressure, and the capacity of the vacuum exhaust pump. For an electropneumatic actuator that generates air pressure by an electric signal, it is desirable to assume a slight pressure setting error of about 1 / 1,000 to 1 / 10,000 of the set air pressure range due to hysteresis or disturbance. Therefore, it is necessary to match the pressure setting range by the electropneumatic actuator with the stroke and thrust required for the stage. That is, in order to control a minute positional displacement, it is necessary to adjust a small force. Therefore, in order to secure the required thrust in the pressurizing direction by using a bellows with a small diameter that has a small thrust with respect to the set pressure, Use a large-diameter bellows. In addition, by adjusting the spring constant of the bellows and optimizing the rigidity of the stage by adjusting the natural length of the bellows and the plate thickness of the bellows, the necessary and sufficient stage movement amount is secured in the pressure setting range by the electropneumatic actuator. be able to.

Further, by adjusting the connection angle of the bellows and the moving direction of the stage carried by the bellows, the thrust for each stage degree of freedom can be adjusted, the positioning accuracy can be improved, and the thrust in the pressurizing direction can be secured. When a large-diameter bellows is installed in the vertical direction, horizontal misalignment due to a change in bellows thrust is unlikely to occur. In addition, by installing a bellows with a small diameter horizontally, precise positioning can be performed by fine thrust adjustment. Furthermore, by setting the bellows with a small diameter at a shallow angle from the stage surface, precise height adjustment is possible even in the vertical direction.

When using a number (6) of bellows equal to the degree of freedom of a rigid body, the small-diameter bellows for positioning must generate both compressive and tensile stresses. A bellows with a small diameter has a low buckling limit pressure, which limits the set pressure range. Further, as an electropneumatic actuator, it is essential to generate positive pressure and negative pressure. Therefore, the number of bellows that is larger than the degree of freedom of the rigid body is arranged, compressive stress is generated in the vertical drive bellows with a large effective cross-sectional area, the vertical thrust is increased, and the bellows with a small diameter for positioning is the natural length. Tensile stress is constantly generated by stretching the bellows or keeping the inside of the bellows on the vacuum side. While preventing buckling of the positioning bellows, the set pressure can be controlled only on the positive pressure side.

In general, small-diameter semiconductor wafers tend to have a high center and a low periphery in the polishing process. Therefore, in order to perform uniform joining, it is necessary to make the thrust at the periphery larger than that at the center. Therefore, it is possible to adjust the surface distribution of the pressurizing stage by increasing the number of vertical drive bellows in the central portion and the peripheral portion.

By detecting the position and orientation of the stage in the three-dimensional space including center coordinates, rotation, and tilt with a non-contact position sensor and controlling the pressure supplied to the pneumatic bellows, 6 axes of the stage can be added without accumulation of errors. Pressure positioning is possible. As the non-contact position sensor, various methods such as optical measurement and a method of measuring pressure and impedance changes due to proximity effect can be used. In optical measurement, a laser interferometer that measures the phase difference between the reference light and the reflected light from the target, a method that measures the phase difference of the reflected wave of the Fabric Perot resonator formed between the reference mirror and the target, or a collection. A method using chromatic aberration of an optical lens is composed of an optical system using an optical fiber, and has an accuracy of several nm to submicron.

A triangulation type laser displacement meter can also be used when the required stage accuracy is about 2 to 3 μm. There is a correlation between the measurement accuracy and the allowable angle deviation, and it is necessary to consider the expected rotation amount of the stage when selecting the optical distance measuring instrument. Further, a method of detecting a pressure change depending on the distance between the air discharge hole and the facing surface, a capacitance manometer, an inductive displacement measurement system, and the like, such as an air micrometer, can be selected according to the required accuracy and operating environment. When joining between wafers and chips, it is necessary to perform real-time image deviation measurement using alignment marks and adjust the position of the stage during pressurization. In that case, it is possible to omit the horizontal rangefinder. Is.

FIG. 3 is a schematic configuration diagram of a pneumatic bellows stage in which a pneumatic bellows actuator is held on a bottom surface and a side surface perpendicular to the bottom surface. FIG. 3 is a schematic view including a partial cross section of a pneumatic bellows actuator used in the pneumatic bellows stage of the embodiment of FIG. It is a schematic block diagram of a pneumatic bellows stage which made it possible to adjust a pressure distribution by adding a redundant number of pneumatic actuators in the center to the configuration of FIG. 1. FIG. 3 is a schematic configuration diagram of a pneumatic bellows stage in which a load and a buckling limit are improved by adding a pneumatic actuator having a large diameter in the center to the configuration of FIG. 1. It is a schematic block diagram of a pneumatic bellows stage by a pneumatic bellows actuator held only on the bottom surface. FIG. 5 is a schematic configuration diagram of a pneumatic bellows stage in which a load and a buckling limit are improved and positioning accuracy is improved by adding a pneumatic actuator having a large diameter in the center to the configuration of FIG. FIG. 1 shows an example in which the redundancy of the horizontal drive bellows is increased. The horizontal drive bellows has the advantage of being able to prevent buckling due to tensile stress. A schematic diagram of the stage when the pneumatic bellows shown in FIG. 5 is replaced with a spring damper is shown. FIG. 8 shows a calculation example of the stage stiffness matrix (A) and the spring drag matrix (B). FIG. 8 shows a calculation example of the stage transient response to the initial displacement in the x direction (horizontal). FIG. 8 shows a calculation example of the stage transient response to the initial displacement in the y direction (vertical). A schematic diagram of the stage when the pneumatic bellows shown in FIG. 6 is replaced with a spring damper is shown. FIG. 12 shows a calculation example of the stage stiffness matrix (A) and the spring drag matrix (B). Is shown. FIG. 12 shows a calculation example of the stage transient response to the initial displacement in the x direction (horizontal). FIG. 12 shows a calculation example of the stage transient response to the initial displacement in the y direction (vertical). A schematic diagram of the stage when the pneumatic bellows shown in FIG. 1 is replaced with a spring damper is shown. FIG. 16 shows a calculation example of the stage stiffness matrix (A) and the spring drag matrix (B). FIG. 16 shows a calculation example of the stage transient response to the initial displacement in the x direction (horizontal). FIG. 16 shows a calculation example of the stage transient response to the initial displacement in the y direction (vertical). A schematic diagram of the stage when the pneumatic bellows shown in FIG. 7 is replaced with a spring damper is shown. FIG. 20 shows a calculation example of the stage stiffness matrix (A) and the spring drag matrix (B). FIG. 20 shows a calculation example of the stage transient response to the initial displacement in the x direction (horizontal). FIG. 20 shows a calculation example of the stage transient response to the initial displacement in the y direction (vertical). A schematic diagram of an ultrasonic bonding device using the pneumatic bellows configuration of FIG. 1 is shown. A schematic diagram of a semiconductor wafer thermocompression bonding apparatus using the pneumatic bellows configuration of FIG. 7 is shown.

Hereinafter, a configuration example of a pressurizing device in which a metal bellows having 6 degrees of freedom (6DOF) or more of the stage is directly attached to the stage to secure the thrust and accuracy required for a wafer or a chip joining device will be shown. In the case of the rod length control type hexapod, 6 telescopic rods or 7 strings are required to control the position of the stage having 6 degrees of freedom. Adding more control axes is effective in avoiding dead center, but there is a risk that excessive internal stress will be generated in the controlled object due to control errors due to constraints on the combination of expansion and contraction lengths. .. On the other hand, in the case of force control in which the actuator has a spring constant according to the present invention, the equilibrium position is determined so that the elastic energy of a plurality of springs is minimized regardless of the number of actuators, so that the redundancy of the actuator hinders controllability. There is no such thing.

There are welding molds and molding molds for metal bellows. Both are used for vacuum equipment that requires moving parts and alignment in accordance with the vacuum flange standard. Molded bellows are cheaper than welded bellows and are often used for vacuum coarsely ground pipes and connection between vacuum chambers. For example, Mirapro Co., Ltd. (1100 Anadaira, Sutama-cho, Hokuto-shi, Yamanashi), Osaka Rasen Kanko Kogyo Co., Ltd. (3-12-33 Hime-ri, Nishiyodogawa-ku, Osaka), Irie Koken Co., Ltd. (3-1 Marunouchi, Chiyoda-ku, Tokyo) -1 International Building 813), Tropical Flexible Pipe Industry Co., Ltd. (5-9 Shinden Kitamachi, Daito City, Osaka Prefecture) and other companies have prepared standard sizes in advance. In the present invention, a stainless molded bellows having moderate elasticity is used.

Table 1 shows the specifications of the bellows that satisfy the vertical stroke of 8 mm and the horizontal stroke of ± 1 mm as the specifications required when these metal molded bellows are diverted to the pressure stage as pneumatic bellows. It is possible to design metal molded bellows with various thrusts depending on the plate thickness, diameter, and shape of the mountain. Assuming that the thrust of the elevating bellows is 600 to 1800 N per atmosphere, the flange nominal diameter corresponds to 65 A to 150 A, and the buckling limit is 0.2 to 0.7 MPa. For example, the maximum thrust of a pressurizing device using three elevating bellows (Table 1: # 65-1) with an effective area of 58.5 cm ² and a buckling pressure of 0.2 MPa is 3,600 N (600 N x 2 atm x 3).

In the case of a small-diameter bellows (Table 1: # ^25-2 ) used for the positioning bellows, the effective area is 12.5 cm and the buckling pressure is 0.08 Ma, which is 1 atm or less. Therefore, in order to prevent buckling, it is necessary to use it in the range of about ± 0.5 atm including negative pressure. It is also effective to increase the buckling pressure by increasing the shape and thickness of the bellows. For example, it is possible to prevent buckling by enlarging the bellows diameter (Table 1: # 50-2) to increase the bellows spring constant and holding it in a state where tensile stress is generated in a configuration with redundancy. can.

The bellows spring constants shown in Table 1 above indicate the repulsive force when displaced by 1 mm in the axial direction and the axial perpendicular direction. For example, since the spring constant in the axial direction of the descending bellows (Table 1: # 65-1) is 16.4 N / mm, the air pressure is about 3 KPa to drive 1 mm. When moving the stage in the horizontal direction, the spring constant in the direction perpendicular to the axis of the bellows installed in the vertical direction is added as a drag force. For example, the accuracy of the pressure that can be set by an electropneumatic actuator with a pressure range of ± 0.5 atm (1 atm is 0.1 MPa) is several tens of Pa, so in order to improve the positioning accuracy of the pressurizing stage, the thickness of the bellows It is effective to adjust the shape and shape, or to install a spring so that the product of the rigidity of the entire stage and the required stroke is about the same as the thrust of the bellows. In Reference 7, an elastic hinge is installed in parallel with the metal bellows so that a displacement of 300 [㎛] can be obtained with respect to 400 [kPa] in the control of one axis.

In Table 1, metal bellows having various spring constants can be selected by changing the plate thickness and the shape of the mountain even if they have the same nominal diameter. For example, in a bellows with a nominal diameter of 65 A, the buckling pressure increases from 0.2 to 0.51 MPa by increasing the plate thickness from 0.2 to 0.4 mm, and the spring constant increases from 16.4 to 94.7 N / mm depending on the plate thickness. is doing. The spring constant in the direction perpendicular to the axis of the elevating bellows is a resistance to the horizontal displacement of the 6-degree-of-freedom stage, so by selecting an appropriate metal bellows, with respect to the horizontal, vertical and rotational directions without additional springs. , The required resistance and stroke can be designed.

FIG. 1 shows a schematic diagram of a 6-DOF pressurization stage using a metallic flexible bellows based on the present invention. On the bottom of the hexagonal aluminum alloy elevating stage 1 with a side of 223 mm and a thickness of 20 mm, three thick pneumatic bellows 2 for vertical drive (Table 1: # 65-1) are placed on the side of the stage. Three thin horizontal drive pneumatic bellows 3 (Table 1: # 25-2) are arranged at positions offset from the center of the above. Each of the bellows 3 in the horizontal direction is fixed to a wall surface (not shown) orthogonal to the bellows axis. The three pneumatic bellows 2 for vertical drive mainly control the Z direction and tilt (α: rolling, β: pitching), and the three horizontal bellows 3 mainly control the X, Y directions and Z. Controls the rotation direction (θ: yawing) around the axis. The offset distance from the center of the stage gives the rotational torque around the Z axis. By making the diameter of the vertical bellows larger than that of the horizontal bellows, the thrust required for the pressurizing device is secured, and by reducing the diameter of the horizontal and rotational bellows, the horizontal output with respect to the applied pressure. Is reduced and the positioning accuracy is improved.

The axes of the three horizontal drive bellows 3 are approximately orthogonal to the three vertical drive axes. Therefore, the expansion and contraction of the bellows in the horizontal direction causes the stage to move in the horizontal direction with almost no vertical movement. However, in the arrangement shown in FIG. 1, since the bellows shaft is installed away from the central axis of the stage, translational movement and rotational movement occur at the same time due to expansion and contraction of each bellows. Therefore, in the case of translational motion only, it is necessary to adjust the pressure so as to cancel the rotational motion. Further, when the three horizontal drive bellows 3 are extended at the same time, the elevating stage 1 rotates clockwise.

The Z direction and tilt of the elevating stage 1 are measured by the vertical distance sensors 4 arranged at three locations on the upper surface of the stage, and the horizontal distance sensors 5 are arranged at three locations on the side surface of the stage in the X and Y directions and the rotation direction around the Z axis. Measured by.

FIG. 2 is a partial cross-sectional view showing the inside of the pneumatic bellows 2 for driving in the vertical direction. The upper flange 2-1 and the stainless flexible bellows 2-2 and the lower flange 2-3 are airtightly welded. Inside the lower flange, a cylindrical block provided with air introduction holes 2-4 and air discharge holes 2-5 is provided. The cylindrical block reduces the volume inside the bellows to improve the time response of pneumatic control. The upper gap of the cylinder also has a function of limiting the deformation range within the design stroke of the pneumatic bellows 2 for driving in the vertical direction. In order to reduce the internal volume of the cylindrical block, it is desirable that the stage is driven along the bellows axis and the displacement of the bellows in the orthogonal direction is small.

In FIG. 3, a pneumatic bellows 6 for vertical drive (Table 1: # 65-1) is added to the central portion. Since the pneumatic bellows has a spring action and a force control action by pneumatic pressure, even if a number of elevating stages 1 having a mechanical degree of freedom of 6 or more are connected, they are not over-constrained. By increasing the number of pneumatic bellows for vertical drive, it is possible to correct the warp in the semiconductor wafer joint and finely adjust the start position of the joint surface.

In FIG. 4, the number of bellows for driving in the vertical direction is the same as in FIG. 3, and the number of bellows is set to four. Three thin vertical drive pneumatic bellows 2 (Table 1: # 25-2) in charge of operation and horizontal drive pneumatic bellows 3 (Table 1: # 25-2) in charge of horizontal movement and rotation. An example of arranging is shown. By reducing the diameter of the bellows for horizontal and tilting motions, the thrust for pressure control is reduced, enabling precise positioning and tilting control. Generally, by increasing the diameter of the bellows, the elastic constant per mountain increases in proportion to the diameter. Further, since the thrust is proportional to the effective area of the bellows, the buckling limit thrust increases in proportion to the cube of the bellows diameter. On the contrary, if the diameter of the bellows is reduced, the buckling limit pressure is reduced, but positive pressure is applied to the thick central vertical drive pneumatic bellows 6, and the small diameter vertical drive bellows 2 is depressurized. By adjusting the pressure so that tension is always applied, buckling can be prevented. Alternatively, buckling can be prevented even under positive pressure by increasing the thickness of the thin pneumatic bellows 2 for vertical drive 2 and extending it in advance from the natural length to generate tensile stress.

Further, in FIG. 4, two alignment microscopes 7 are used instead of the horizontal distance sensors 5 arranged in FIGS. 1 and 3. By detecting the center coordinates of the two alignment marks 8 by image processing, it is possible to detect the rotation in the horizontal direction (X, Y) and around the Z axis. As a digital camera used for an alignment microscope, for example, a general-purpose CMOS camera can be used by binning from a Toshiba Terry M160 located in 4-7-1 Asahigaoka, Hino-shi, Tokyo and limiting the number of pixels to about VGA (640x520 pixels). A frame rate of about 500 fps can be secured. With the parallel layer processing technology, the mark position can be detected with a time delay of about several msec, and in-situ observation and control at the time of joining becomes possible. The resolution using the x20x objective lens is about 1 μm.

FIG. 5 shows a case where a hexapod using a conventional telescopic linear actuator and a universal joint is replaced with a metal flexible bellows. In this configuration, six diagonal pneumatic bellows 9 (Table 1: # 50-2) with a slightly larger diameter make up three pairs, and the angle between the bellows 9 and the normal of stage 1 is approximately 30 °. Yes, as shown by the broken line in the figure, the axes of each bellows pair intersect at three points above the stage. The bottom of each bellows pair is placed in contrast to a position rotated 45 ° from the line segment formed by the center of the stage, with the point where the axes of the bellows pair intersect is projected onto the bottom surface (not shown). .. The configuration of FIG. 5 has an advantage that the fixing surface of the bellows is flat and the shapes of the bellows and the fixing jig are all the same, so that the design and arrangement are easy. On the other hand, if the height H of the stage is α with respect to the length L of the bellows, then H = L · cos (α) <1 and the bellows required to obtain the same stroke. The length becomes longer. On the other hand, since the thrust in the vertical direction is cos (α) times, the limit thrust considering buckling is disadvantageous by cos (α) ^ 2. The thrust at the working pressure (~ 0.2MPa) at the buckling limit pressure of 0.28MPa of the diagonal pneumatic bellows 9 is 268Nx2, and if the angle between the bellows and the normal of the stage is 30 °, the thrust from the six bellows is , 2,800N.

FIG. 6 shows an example in which a thick central vertical drive pneumatic bellows 6 (Table 1: # 100-2) for carrying a vertical load is added in FIG. By pressurizing the central vertical drive pneumatic bellows 6, the pressure on the peripheral diagonal pneumatic bellows 9 can be reduced or maintained in a pre-stretched position to generate tensile stress, and the buckling limit can be generated. Can be alleviated. Further, since the diagonal pneumatic bellows 9 does not require thrust in the vertical direction, it is installed shallower than the stage (the angle between the bellows and the normal of the stage is ~ 60 °) as compared with FIG. 5, and the effective diameter is set. Also uses a small bellows (Table 1: # 25-2). That is, by reducing the diameter of the bellows for alignment adjustment and adjusting the mounting angle, buckling is prevented, the stage drive amount per set pressure is suppressed, and precise alignment is possible. Since the buckling limit of the thick central vertical drive pneumatic bellows 6 (Table 1: # 100-2) is about 0.3 MPa and the working pressure is about 0.2 MPa, the maximum thrust of the stage is about 2,000 N.

FIG. 7 shows an example using four horizontal bellows. In the case of a parallel link stage using strings, it is known that the degree of freedom of the system + 1 string is required, but the pressure of the thin bellows with low buckling pressure is set below atmospheric pressure or tension is applied in advance. As a result, it becomes a tension state, and buckling can be avoided even with a long bellows. Therefore, it is possible to secure a longer stroke in the horizontal direction than the configuration shown in FIG. Further, the bellows long in the horizontal direction is advantageous in terms of service life even for deformation perpendicular to the axial direction due to the raising and lowering of the stage.

Regarding the controllability of the parallel link stage using the pneumatic bellows, the stage displacement with respect to a constant load and the stage displacement with respect to the driving pressure to each pneumatic bellows are called pychrono (http://projectchrono.org/pychrono/), which is a rigid body motion. It was evaluated by a simulation program. The actual pneumatic bellows has an elastic hinge action that generates expansion and contraction or thrust with respect to pressure, and at the same time, at both ends of the bellows, generates drag with respect to the inclination of the bellows. That is, the metal flexible bellows can be modeled as a spring damper whose connection portions at both ends are fixed by elastic hinges and a linear actuator that generates a force in the spring direction by pneumatic pressure. However, this time, the spring constant of the hinge part was ignored, and the calculation was made assuming that the linear spring damper is connected to the universal joint that does not generate torque. Therefore, the lateral stage rigidity is underestimated.

Pneumatic bellows As an evaluation of stage controllability, sufficient stress is generated for 6 degrees of freedom as a rigid body of the stage for driving each pneumatic bellows (there is no dead center). The vertical thrust can be increased compared to other degrees of freedom. There is as little interaction as possible between the stress on the stage and the driving force on the pneumatic bellows, especially the normal stress component with high working strength and other stress components that require minute force control, and the tensile stress from the viewpoint of buckling. A state in which (negative) is generated is desirable. From these points of view, the spring damper model corresponding to the pneumatic bellows arrangement of FIGS. 5, 6, 1 and 7 was analyzed.

FIG. 8 shows a schematic diagram corresponding to a pneumatic bellows stage in a hexapod arrangement, which corresponds to FIG. The stage is a disk with a mass of 7 kg, a diameter of 400 mm, and a thickness of 20 mm, and a spring damper with a free length of 100 mm is placed 30 ° from the outer circumference of the disk to the normal of the stage surface. The projection angle was arranged at ± 30 °. The height of the stage is 77mm. The spring constant was 14,700 N / m, which corresponds to Table 1: # 50-2, and the damping constant was assumed to be 10 N / (m / s). Furthermore, in order to evaluate the rigidity of the stage, the drag force when rotated 1 mm in the x, y, and z directions and 1 ° around each axis was calculated. FIG. 9 shows a calculation example of the stage stiffness matrix (A) and the spring drag matrix (B) in FIG. In this figure, the y direction is represented by the vertical axis, the left front is represented by the x axis, and the right front is represented by the z axis.

X-axis (A), Y-axis (B), Z-axis (C), X-axis rotation (D), and Y-axis rotation, respectively, after being displaced by 1 mm in the x and y directions in FIGS. 10 and 11, respectively. (E), the calculation result of the free vibration waveform of the stage around the Z axis (F) is shown. In FIG. 10, a damping vibration having a period of 5 Hz in the horizontal direction (x direction (A)) and a period of 15 Hz in the vertical direction (y direction (B)) was obtained in FIG. When the initial conditions are given only in the x direction, the amplitude in the y and z directions is about 10 ^-5 (Fig. 10 (B), (C)), and the rotation is about 0.2 ° in the z axis direction (Fig. 10 (F)). )) Ancillary vibration is occurring. On the other hand, when the initial condition is given only in the y direction, only vertical (y-axis, FIG. 11B) vibration is observed. This corresponds to the fact that in FIG. 9, in the second row of the stage stiffness matrix element (A) corresponding to the displacement in the y direction, only the second column corresponding to force exists.

In FIG. 9, positive corresponds to compressive stress and negative corresponds to tensile stress. In FIG. 9A, the drag in the vertical direction (y) is -53.2 N / mm, whereas the drag in the horizontal direction (x, z) is -17.7 N / mm. Further, with respect to the displacement in the horizontal direction, a torque of ± 3.2 N is generated around the x and z axes, indicating that the rotational force is generated parasitically. In FIG. 9B, the drag generated by each spring has different polarities of about -11.4 N / mm for vertical (y) displacement and ± 6 N / mm for horizontal displacement. Force is being generated. FIG. 9B shows that when stress corresponding to each row is generated at the same time, the stage moves and rotates in the direction of 6 degrees of freedom up to x, y, ---, and rotZ, respectively.

FIG. 12 corresponds to FIG. 6 in which a large-diameter pneumatic bellows (Table 1: # 100-2) is placed in the center and thin bellows (Table 1: # 25-2) are placed in the periphery in addition to the hexapod arrangement. The schematic diagram of the pneumatic bellows stage is shown. By increasing the height of the fixed point of the peripheral bellows, the mounting angle of the peripheral bellows is set shallow (~ 30 ° from the horizontal plane), and the thrust in the horizontal direction (x, z) and the vertical direction (y) in the peripheral bellows is almost the same. It is set equally. That is, the alignment adjustment is performed by the peripheral bellows, and the pressurization is performed by using the bellows in the central portion, so that the alignment accuracy in the horizontal, rotational, and tilting directions can be improved while maintaining the thrust in the vertical direction.

FIG. 13 shows a calculation example of the stage stiffness matrix (A) and the spring drag matrix (B) in FIG. The second row and second column (-23 N / mm) of the stage stiffness matrix (A) show the stiffness in the vertical direction, which is larger than the stiffness in the horizontal direction (-7.3 N / mm). In the spring drag matrix (B), compressive stress (~ 200N) is generated in advance in the central bellows (sp0) and tensile stress (~ -90N) is generated in the peripheral bellows (sp1-sp6) using the redundancy of the system. As such, by setting the free length or air pressure, the peripheral bellows can be biased to the tension mode and buckling of the thin bellows can be prevented. Further, by adding a thick bellows having a large limit buckling pressure in the vertical direction, the thrust in the vertical direction can be enhanced. 14 and 15 show a calculation example of the stage transient response to the initial displacement in the x and y directions in FIG. The vibration mode is similar to FIGS. 10 and 11.

FIG. 16 shows an analysis example of the pneumatic bellows pressurizing device corresponding to FIG. Three thick bellows (Table 1: # 65-1) are installed in the vertical direction, and three thin bellows (Table 1: # 25-2) are installed in the horizontal direction at 30 ° from the center of the stage. The spring constants were 16400 N / mm and 2500 N / mm, respectively. FIG. 17 shows a calculation example of the stage stiffness matrix (A) and the spring drag matrix (B) in FIG. Compared to FIG. 9, since the rigidity (49) in the y direction is larger than the rigidity (3.7) in the x direction and no torque is generated in the z-axis direction with respect to the displacement in the x direction, each axis is independent. Highly sex. However, for example, in the case of moving in the x direction as shown in the first column of FIG. 17 (B) or in the case of rotating only in the vertical direction (rotY) as shown in the fifth column of FIG. 17 (B). In addition to the horizontally installed sp1-sp3, it is necessary to adjust the vertically installed sp1vt-sp3vt. Therefore, it is necessary to control the set pressures of the six bellows in parallel even when moving only in the plane direction.

In FIGS. 18 and 19, damped vibrations having a period of 5 Hz were obtained in both the horizontal direction (x direction) and the vertical direction (y direction). When the initial conditions are given only in the x direction, the amplitudes in the y (FIG. 18 (B)) and z directions (FIG. 18 (C)) are about ^10-5 and ^10-9 , and the rotation is x (FIG. 18 (FIG. 18 (C)). D)) Ancillary vibrations of about ^10-5 are generated around the axis and about ^10-3 are generated around the y-axis. The accompanying vibration is suppressed by two orders of magnitude or more as compared with FIG. 10 according to the arrangement of hexapods. Further, when the initial condition is given only in the y direction, only vertical (y-axis, FIG. 19 (B)) vibration is observed as in FIG. 10. This corresponds to the fact that also in FIG. 17, the matrix element in the second row corresponding to the displacement in the y direction exists only in the second column corresponding to forcey. A rigid body constrained to a plane has a degree of freedom (DOF) of 3 and can be positioned by three springs, which must be subjected to both compressive and tension. In fact, in FIG. 17B, the signs of the drag force of the spring due to the displacement in each axial direction are mixed.

FIG. 20 shows a schematic view of the stage when the pneumatic bellows shown in FIG. 7 is replaced with a spring damper. By adding one redundancy in the horizontal direction, tension can be applied to the spring in advance. In fact, in the spring drag matrix (B) of FIG. 21, all the drags of force_sp1a, force_sp1b, force_sp2a, and force_sp2b corresponding to the horizontal direction can be set to negative (tension). 22 and 23 show a calculation example of the stage transient response to the initial displacement in the x-direction and the y-direction. No incidental vibrations in other directions occur with respect to the free vibrations having an initial amplitude of 1 mm in the x direction (FIG. 22 (A)) and the y direction (FIG. 23 (B)). In fact, the off-diagonal term of the stage stiffness matrix (A) in FIG. 21 has many zero components, which facilitates positioning control. Further, in this configuration, since the horizontal bellows can be regarded as a string, it is possible to select a bellows having a small diameter and a long stroke without fear of buckling.

The air pressure setting range by the electropneumatic actuator is appropriate from vacuum to the buckling limit of about 3 atm, and the setting accuracy is limited to about 1/1000 to 1 / 10,000 of the pressure range. Therefore, in the direction of determining the positioning accuracy of the pressurizing device, the diameter of the bellows is optimized, and the horizontal stage rigidity and generated thrust in the horizontal direction are taken into consideration, and the horizontal stage movement range within the settable pressure range is the minimum necessary ( ~ 1 mm or less) is desirable. On the other hand, in the pressurizing direction, it is necessary to increase the diameter of the bellows and set the bellows axis vertically to secure the necessary thrust. Also in that case, it is necessary to adjust the vertical spring constant of the bellows or add a coil spring or the like, considering that the vertical positioning accuracy is proportional to the vertical spring constant.

Hereinafter, an ultrasonic bonding device based on the pneumatic bellows arrangement shown in FIG. 1 will be described with reference to an embodiment of the present invention in the case where the ultrasonic bonding device is configured more specifically. Stoppers and columns 11 are provided at three locations on the side surface of the elevating stage 1, and the base plate 10 and the upper plate 12 are connected to each other. The elevating stage 1 is sandwiched by using the recess in the central part, and the horizontal movable range of the stage is limited to ± 1 mm and the vertical stroke is limited to 8 mm.

Laser interference type vertical distance sensors 4 are installed at three locations on the upper plate 12 to measure and control the vertical and tilting directions. Further, a horizontal distance sensor 5 using a triangular survey type laser range finder is provided on the side surface (three places) of the support column 11 to measure and control the stage position and rotation in the horizontal direction. Normally, air actuators use a sliding mechanism such as a cylinder to limit the stroke only in the vertical direction, but by actively controlling the distance between the sides in six directions, the position and posture of the stage can be uniquely determined. No sliding mechanism is required.

An ultrasonic horn 13 is provided on the elevating stage 1, and a sample adsorption stage 14 is provided on the lower surface of the upper plate 12. A 4-axis manipulator 15 is used for introducing the semiconductor chip. First, the elevating stage 1 is lowered to the lower limit of the stopper, and the two semiconductor chips are adsorbed and fixed while reversing the directions of the ultrasonic horn 13 and the sample adsorption stage 14.

An infrared microscope 16 is provided on the upper plate 12. When the gap between the two semiconductor chips becomes about 20 μm, the alignment mark of each semiconductor chip is confirmed at multiple positions using an infrared microscope 16, and the center position of the alignment mark provided on each chip is confirmed. Control the horizontal drive bellows so that they match.

While confirming and fine-tuning the alignment position, the elevating stage 1 is raised, the fluctuation of force vs. displacement is measured, and when the samples overlap, ultrasonic vibration is started. Further, the load (pressure of the bellows for driving in the vertical direction) is increased, and the displacement based on the bump deformation of a predetermined value (up to 2 μm) is measured and controlled by using the vertical distance sensors 4 at three locations.

At least two alignment marks are required to align the horizontal position and the angle of rotation of the two chips with the alignment marks. There are a method of moving the infrared microscope 16 on the XY stage 17 to measure the deviation of a plurality of alignment marks, and a method of simultaneously capturing a plurality of images to measure the position and the angle of rotation. Simultaneous measurement of multiple images is advantageous for kinematic control that requires high-speed position sampling, but for chip sizes smaller than the imaging chip of infrared cameras, optical systems such as split imaging are available. You will need it. When performing image analysis of the alignment mark using an infrared microscope, the control by the horizontal distance sensor 5 provided on the side surface of the elevating stage 1 is controlled by the field of view of the objective lens having a relatively high magnification (~ x20). A relatively inexpensive triangular survey type laser rangefinder 5 is used because the accuracy (up to ± 50 μm) at which an alignment mark image can be inserted is sufficient.

A semiconductor wafer joining device based on the pneumatic bellows arrangement shown in FIG. 7 is shown in FIG. 25. The hatched portion shows a partial cross section. The pneumatic bellows arrangement shown in FIG. 7 has an advantage that the wafer carry-in route can be widely taken because the horizontal drive bellows 3 are arranged symmetrically on both sides. The displacement of the horizontal drive bellows 3 is set to ± 4 mm in the direction orthogonal to the axis of the bellows. Therefore, a taper is provided in the direction of the tip of the block to reduce the pneumatic capacity inside the bellows.

In the case of wafer joining, it is necessary to raise the wafer temperature to about 300 ° C. Therefore, the sample adsorption stage 14 and the lower sample heating stage 20 have a structure in which a metal plate incorporating a sheath heater or the like is insulated with a ceramic spacer or the like. At that time, a part of the elevating stage 1, the vertical and horizontal driving bellows is also heated. The heat resistance of the bellows drive portion is about 100 to 150 ° C. when Baitton or Teflon O-ring 21 is used for the base seal portion, and about 300 ° C. when the welded seal structure does not use the O-ring. Further, since the bellows is made of a thin stainless steel plate having a relatively poor thermal conductivity, a temperature difference of 100 ° C. or more can be provided between the portion in contact with the stage surface and the base portion. That is, it has much heat resistance as compared with a stage using a high load bearing in which the use of lubricating oil is unavoidable and a piezoelectric element having a restriction on the curry point. In addition, it is easy to maintain a clean environment with little influence of dust generation due to sliding.

The upper plate is provided with three vertical distance sensors 4 and two infrared microscopes 16. The sample adsorption stage 14 is provided with a conical opening corresponding to the alignment mark position, and the silicon 6-inch wafer 19 placed on the lower heating stage is observed through the compound semiconductor wafer 18 having a diameter of 4 inches. .. By measuring the center position of each alignment mark with two infrared microscopes 16, the amount of rotation in the horizontal (X, Y) direction and the vertical (Z) direction can be calculated.

Since each of the three vertical bellows 2 generates normal stress proportional to the injection pressure, it is possible to perform a copying operation with a constant pressure at three points after contacting the wafer, and to control the six degrees of freedom of the stage. It is also possible to join with a certain gap. For example, when performing a wafer or chip bonding with alignment using silver paste or silver nanopaste, it can be applied when it is desired to keep the gap (paste thickness) between the wafers constant.

As described above, in a chip or wafer joining device that requires a load of several hundred to tens of thousands of N, a 6-DOF alignment pressurizing stage using a pneumatic bellows that is inexpensive and can withstand a clean environment while limiting the stroke required for joining. Was realized. Depending on the required alignment accuracy, various non-contact distance measuring devices including image recognition processing can be used. The 6 degrees of freedom required for table attitude control are measured at the same time, and the pressure on 6 or more pneumatic bellows is calculated and output in a reverse kinematics manner. Since the natural frequency of the stage is about 100 Hz, the position accuracy of submicron or less can be ensured by measuring the posture of the stage at a time interval of 1 msec, preferably 100 μS, and controlling the air pressure.

It should be noted that the embodiments disclosed this time are exemplary in all respects and are not restrictive. The scope of the present invention is not limited to the embodiments disclosed here, but includes all modifications within the scope indicated by the claims or within the scope equivalent to the claims. Is intended.

1: Elevating stage 2: Pneumatic bellows for vertical drive 2-1: Elevating stage 2-2: Pneumatic bellows for vertical drive 2-3: Pneumatic bellows for horizontal drive 2-4: Vertical distance sensor 2 -5: Horizontal distance sensor 3: Horizontal drive pneumatic bellows 4: Vertical distance sensor 5: Horizontal distance sensor 6: Central vertical drive pneumatic bellows 7: Alignment microscope 8: Alignment mark 9: Diagonal pneumatic bellows
10: Base plate
11: Stopper and support
12: Top plate
13: Ultrasonic horn
14: Sample adsorption stage
15: 4-axis manipulator
16: Infrared microscope
17: XY stage
18: 4 inch Weber
19: 6 inch Weber
20: Lower sample heating stage
21: O-ring
22: Spring

Claims (5)

Pressurization using a pneumatic bellows, which uses a plurality of pneumatic bellows and controls the spatial posture and thrust by controlling the pneumatic pressure introduced into the bellows with positive and negative pressures within a range in which buckling does not occur in the bellows. On stage;
Six or more of the bellows are directly connected to the stage for vertical, horizontal and rotational position and force control corresponding to 6 degrees of freedom when the stage is considered rigid;
It has a simultaneous and parallel air pressure feedback mechanism to the bellows;
The spatial arrangement, effective cross-section, elastic constant and natural length of the bellows are changed according to different thrusts and strokes corresponding to the specifications of vertical, horizontal and rotational directions;
A 6-DOF pressurization stage featuring. The positioning accuracy was improved by installing the bellows with a large effective area in the vertical direction and installing the bellows with a small effective cross section in the horizontal direction of the stage or shallowly with respect to the horizontal plane.
The 6-DOF pressurization stage according to claim 1. It has more than 6 degrees of freedom of the pneumatic bellows when the stage is regarded as a rigid body, and generates tensile stress in the bellows having a small effective cross-sectional area and compressive stress in the bellows having a large effective cross-sectional area. Preventing buckling of the bellows while increasing vertical thrust;
The 6-DOF pressurization stage according to claim 1. Having more of the bellows than 6 degrees of freedom when the stage is considered rigid; adjusting the surface distribution of the pressurized thrust of the stage;
The pressurizing stage according to claim 1. Pressurized positioning is performed by detecting the position and orientation of the stage in the three-dimensional space including the center coordinates, rotation, and tilt with the non-contact position sensor or the alignment mark position;
The 6-DOF pressurization stage according to claim 1.

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