Pressurization stage using a pneumatic bellows

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

Technical Field

[0001] The present invention relates to a pressurizing stage using a pneumatic bellows, and particularly to a sub-micron precision pressurizing alignment mechanism including a wobble required for, for example, a wafer bonding apparatus or a nano-implant apparatus in the semiconductor manufacturing field.

Background Art

[0002] In recent years, in the wafer bonding process required for manufacturing three-dimensional ICs, it is necessary to perform pressure alignment on the order of tons after aligning and adjusting the relative displacement of wafers at the sub-micron order at a high temperature of about 400°C. Further, in an infrared imaging chip using a hetero-semiconductor material, a process of densely bonding an infrared photodiode array and a readout IC at a pixel pitch of a dozen or so μm at the chip level is required. In the above bonding process, it is necessary to perform heating (~300°C), pressurization (~1,000 N), or ultrasonic application while controlling the parallelism (gap) between wafers as well as the horizontal position in a clean atmosphere.

[0003] For example, in the chip-level bonding process for manufacturing a VGA (640 x 520 pixels) infrared imaging device with a chip area of about 1 cm 2 pressurization of several hundred N and ultrasonic application are required with an alignment accuracy of ±1 micron and a parallelism of ±100 microradians (the difference in gap within 1 μm at both ends of a 1 cm2 chip). (Non-Patent Document 1)

[0004] In the conventional bonding apparatus configuration, as the vertical drive mechanism, a pneumatic actuator using a torque control AC servo motor or an air cylinder has been used, and as the horizontal drive mechanism, a bearing stage has been used. For example, in the case of an AC servo actuator, Amano Sewing Machine Co., Ltd. located at 1463 Hazama-cho, Hachiōji City, Tokyo has developed a precision pressure control servo press device with a maximum pressure capacity of 30 kN. Also, in the case of a pneumatic actuator, Sumitomo Heavy Industries, Ltd. located at 2-1-1 Osaki, Shinagawa-ku, Tokyo produces a mechanism in which a positioning control mechanism is provided in a pneumatic cylinder using an air bearing under the trademark "Air Sonic". (Patent Document 1)

[0005] As a bonding apparatus for electronic components and semiconductor modules, in the FA1000 type ultrasonic high-precision flip chip bonder of Advantest Corporation located at 140 Katatsuna 8-chome, Nakaagawa City, Fukuoka Prefecture, as the alignment means in the plane direction, an X, Y stage using a cross roller guide and a rotation mechanism are used, and in the Z direction, a pneumatic actuator using an air cylinder is used. Also, in the WI-1000 type vacuum wafer bonding apparatus of Bondtech Corporation located at 77 Ishihara Nishimachi, Kōjōin, Minami-ku, Kyoto City, Kyoto Prefecture, an electric linear actuator is used in the Z direction. The above Z-direction actuator is provided with a linear encoder and a strain gauge, and positioning accuracy of sub-micron level is ensured. (Patent Document 2)

[0006] As a mechanism for maintaining the parallelism between chips or wafers, for example, a spherical bearing type imitation mechanism of Advantest Corporation or a piezo stage of Bondtech Corporation is used, and it is used for bonding semiconductor chips that require high-precision parallelism management. However, the imitation mechanism has problems with the accuracy of the imitation operation and changes over time. Also, since the piezo stage has a short stroke (~ several tens of μm), it is necessary to combine it with a conventional mechanical rough movement mechanism that combines a bearing stage and a roller or ball screw. In particular, in a high-temperature and high-load device in a clean atmosphere required in a semiconductor process apparatus, it becomes complicated to address issues such as overcoming the heat resistance and load resistance of the piezo element and preventing contamination by the lubricating oil required for the bearing stage.

[0007] In a conventional serial link stage in which linear or rotary stages using bearing guides and ball screws are stacked as many as the required degrees of freedom, elastic deformation of about 1 μm cannot be avoided for each axis due to a radial or axial load of about 1,000 N. For example, when a compressive or tensile stress is applied to a roller guide stage, deformation of about 0.5 μm / 1,000 N occurs. (Non-Patent Document 2) Further, the deformation rate in a ball screw or a roller screw having higher rigidity, which is used as a feed screw mechanism for driving the stage, is about 1 μm / 1,000 N or more even when a relatively large feed screw with a shaft diameter of 40 mm is used. (Non-Patent Document 3)

[0008] It is possible to reduce hysteresis such as backlash by using an optical linear or rotary encoder for each axis in combination and improve the repetitive positioning accuracy to the sub-micron level, but torsions (yawing, pitching, rolling) of each axis due to moment loads that cannot be grasped in the measurement of each axis are assumed. In a stage for precision alignment, including parallelism, six-axis control in the vertical and horizontal directions for three axes (x, y, z), rotation (θ: yawing), and tilt (α: rolling, β: pitching) directions is required. In a serial link stage, elastic deformation accompanying pressurization accumulates among six drive mechanisms, and a positional deviation of about several μm that cannot be grasped at each axis level occurs. Therefore, in order to ensure sub-micron positioning accuracy under load application conditions, it is necessary to measure the spatial absolute coordinates of the target stage and perform feedback control.

[0009] In the control method of a multi-axis stage, a 6-axis stage using a parallel mechanism is called a Stewart platform or a Hexapod, and has been put into practical use as a 6-axis stage with high rigidity. In this case, six variable-length rods hold the stage via ball joints or universal joints. Compared with a bearing-type stage, the stroke of the Hexapod is limited, but by simultaneously and parallelly controlling the lengths of the six rods supporting the stage, the position and tilt of the stage can be quickly set without cumulative errors due to displacement errors or backlash at the link connection part. The lengths of the six arms and the stage position coordinates are represented by polynomials including trigonometric functions, but with the development of computers and software, the calculation of the arm lengths required for moving to a desired stage position (inverse kinematics) no longer poses a major obstacle.

[0010] However, even if the lengths of each of the six rods can be controlled with sub-micron accuracy using linear actuators with optical linear scales, it is difficult to hold the stage position with sub-micron accuracy. This is because it is difficult to suppress elastic deformation of the rods and joint parts to below the sub-micron level under a load condition of about 1,000 N. In addition, backlash at the joint part causes hysteresis when switching between expansion and contraction, so pressure needs to be applied, which imposes restrictions on lubricity and load range. Therefore, in order to obtain a large-load and sub-micron-level stage accuracy, it is necessary to measure the absolute coordinates of the target stage and perform feedback control, similar to a serial link stage.

[0011] A robot hand that is moderately soft in terms of strength and structure and can operate with delicate force adjustment is required in medical applications and semiconductor processing equipment. Since the pneumatic drive mechanism generates a driving force proportional to pressure, it is suitable for stiffness control. Because the pneumatic drive mechanism has less contamination and a simple structure, a manipulator using a parallel mechanism with a pneumatic cylinder and a ball joint has been manufactured for medical use. In particular, since the upper limit of the thrust force is determined by the supply pressure, the safety is high. (Non-Patent Document 4)

[0012] By a similar mechanism, a 6-axis stage (Hexapod) using a pneumatic cylinder and a universal joint can also be easily assumed. However, in the case of a pneumatic cylinder, if an air bearing is used to reduce sliding friction, an air gap of more than ten micrometers is formed, and the stiffness in the direction perpendicular to the axis becomes low. In addition, it is necessary to use a universal joint with a bearing at the joint part or a ball joint having a sliding surface, and the environmental resistance performance such as elastic deformation and high temperature deteriorates.

[0013] The pneumatic bellows, like the pneumatic cylinder, has a function of converting pressure into force or displacement. In addition, since the bellows has a spring action also for the displacement in the axial direction, a ball joint or a universal joint is not required. Since there is no sliding mechanism in the axial direction, no hysteresis due to friction occurs. Usually, in order to avoid buckling, an outer skeleton or an inner skeleton is used in combination, and it is used in a state where tension is applied. (Non-Patent Document 5) A drive mechanism for force control imitating a living body is called soft robotics and is becoming a major field of robot research. (Non-Patent Document 6)

[0014] In the application to the semiconductor field, a pressurizing mechanism using a pneumatic bellows and an elastic hinge has also been proposed. By arranging the elastic hinge around the pneumatic bellows, the displacement direction is restricted only to the axial direction of the pneumatic bellows without a sliding mechanism such as a cylinder. Furthermore, by incorporating a linear encoder, a load cell, etc., longitudinal positioning is possible. (Patent Document 3) By attaching three of these uniaxial pneumatic actuators perpendicularly to the axis to a stage, up-and-down and pitching drives become possible. Also, by combining three units of a biaxial actuator unit with orthogonal axes, a stage capable of rotation in addition to the above up-and-down and pitching drives has been shown. (Patent Document 4)

[0015] The inventors 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 forming bellows and an elastic hinge. This is a system in which the pressure supplied to the flexible bellows is feedback-controlled by an electro-pneumatic actuator using position information from an optical linear scale or a laser interferometer. In this system, the pressure-displacement characteristics of the stage are set to about 300 [μm] with respect to a differential pressure of 400 [kPa]. At this time, the natural frequency formed by the mass of the movable part and the spring constant of the hinge is about 60 [Hz]. Position measurement was performed at a cycle of 0.1 msec using a laser interferometer (RLU10 manufactured by Renishaw), the control signal was calculated by measurement and control software MATLAB Simulink xPC Target, and output to an electro-pneumatic actuator using a nozzle flapper type three-way servo valve by a 16-bit DAC. (Non-Patent Document 7) Furthermore, a low-fluid-noise servo valve using a voice coil motor with less hysteresis was adopted to improve the pressure control characteristics. The static position accuracy has reached 1 nm with respect to the stroke of the stage of ±1250 μm. (Non-Patent Document 8)

[0016] Metal forming bellows are usually manufactured by deforming a thin metal plate such as stainless steel into a corrugated shape, but there are some structural constraints. One is the expansion and contraction stroke, which needs to be set within about ± several % of the natural length from the perspective of life. Another constraint is buckling. When the pressure exceeds a certain level, deformation occurs at a right angle to the axial direction. The pressure P cr is generally expressed by Equation 1). (Non-Patent Document 9) P cr =2πf i / (N 2 q) ··· Equation 1) However, f i is the elastic coefficient per corrugation of the bellows, N is the number of corrugations of the bellows, and q is the pitch per corrugation of the bellows.

[0017] That is, the critical pressure is proportional to the elastic coefficient per corrugation and inversely proportional to the square of the number of corrugations. Also, the elastic coefficient per corrugation of the bellows is proportional to the circumference and proportional to the cube of the bellows plate thickness. Since the thrust is proportional to the effective area of the bellows, the thrust at the buckling limit is generally 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 corrugations (bellows length) while considering the required stroke, buckling limit, and spring constant for stable stage driving using metal forming bellows.

[0018] Regarding the minimum required stroke during wafer or chip bonding, the positional deviation at the start of alignment is about the positioning accuracy of the transfer robot, ~200 μm, and the stroke required during bonding is about several mm for ensuring a gap during wafer transfer. Therefore, by using a metal forming bellows with a natural length of about 100 mm, a stroke of several mm required for the bonding apparatus can be ensured.

[0019] In the joining process, after positioning, pressure is applied while monitoring for misalignment. First, in the positioning process, the stage position is determined by the balance condition between the thrust force due to the air pressure supplied to the bellows and the spring action due to the bellows or a spring installed in parallel. To ensure positioning accuracy, it is necessary to adjust the rigidity of the stage with the bellows and spring, match the range and accuracy of the air pressure controllable by the electro-pneumatic actuator with the stage position and accuracy, and ensure the required thrust force in the pressurizing direction.

[0020] In recent non-contact optical distance measurement systems, instead of limiting the measurement span to several millimeters, products that allow an angular misalignment of the target surface of about ±0.3 to ±3° or more have been announced. For example, using converging light, an optical fiber interferometer distance meter (attocube, IDS3010, Eglfinger Weg 2, 85540 Haar, Germany) that uses the reflection intensity vibration principle of a Fabry-Perot type resonator formed between the end face of an optical fiber collimator and the target surface, and a multi-color laser coaxial displacement meter (Keyence, CL-3000 series, 1-3-14 Higashi-Nakajima, Toyotashi-ku, Osaka) that uses the chromatic aberration of a lens, etc. are on the market. If the precise adjustment range of the stage is within 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 can be measured with sub-micron accuracy and at time intervals of 0.1 msec or less.

[0021] In the air pressure control system, it is necessary to control the pressure at a speed sufficiently faster than the natural frequency of the system. To avoid hysteresis due to the magnetic material, nozzle flapper valves and linear direct acting valves using air-core solenoids have been developed by MOOG (400 Jamison Road Elma, New York, 14059 USA) and PSC Co., Ltd. located at 241-1 Higashi-Hiradocho, Owariasahi City, Aichi Prefecture, and products with a cut-off frequency of about 400 Hz are on the market.

[0022] In the above parallel link system, computer-aided inverse kinematic control is required. However, with the development of robot-related technologies and three-dimensional measurement technologies, the environment is becoming increasingly conducive to realizing a system that is mechanically simpler than conventional serial linkages and has excellent accuracy and output load. Also, in the field of soft robotics where force feedback can be adjusted, a pneumatic control method with excellent safety and cleanliness has attracted attention.

Prior Art Documents

Patent Documents

[0023]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Non-Patent Documents

[0024]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Non-Patent Document 7

Non-Patent Document 8

Non-Patent Document 9

Summary of the Invention

Problems to be Solved by the Invention

[0025] In view of the problems in the above-described conventional examples, the present invention realizes a high-precision 6-axis pressurizing stage that does not include a sliding part and has excellent cleanliness and environmental resistance by using a parallel link mechanism with pneumatic bellows. At that time, the spatial arrangement of the bellows is considered in view of the buckling limit, and a configuration that satisfies the alignment accuracy, stroke, and load required for a semiconductor wafer or semiconductor chip bonding apparatus is clarified using a relatively inexpensive metal-formed bellows.

[0026] In stage control assuming pressurization at the submicron level and of about 1,000 N or more, it is necessary to consider all components as elastic bodies and the elastic strain associated with the load. Therefore, in order to control the spatial position and orientation in the submicron order, feedback control based on three-dimensional space measurement of the stage is required for any configuration of the stage. In the present invention, by performing parallel feedback control of the air pressure at a sufficiently fast measurement interval for a plurality of metal flex bellows having both a spring action and a pneumatic cylinder action, higher rigidity and controllability than a serial link having a feedback mechanism for each axis in the prior art are realized.

[0027] Metal flex bellows may buckle, and this tendency is promoted by inclination and lateral load. Usually, in order to avoid buckling, an external skeleton or an internal skeleton is used in combination, but in that case, since it involves a movable joint part, contamination by lubricating oil, deformation of the bearing, or hysteresis due to backlash occurs. Therefore, it is necessary to design so that buckling does not occur within the operating range without using a movable joint part. Further, since the buckling limit pressure condition decreases when a load orthogonal to the axial direction of the bellows is applied, it is desirable that the stage be driven along the bellows axis.

[0028] The thrust generated in the bellows is a value obtained by multiplying the air pressure applied to the effective area of the bellows. For example, a cross-sectional area of 100 cm 2When 1 atm of air is pressurized to the bellows, the thrust force is approximately 1,000 N. In the wafer bonding apparatus, the mainly required load is in the vertical direction (y), and the loads required for alignment adjustment in the horizontal (x, z), rotational (θ: yawing), and pitching (α: rolling, β: pitching) directions are to correct the stress components due to the angular misalignment in the vertical direction, and are estimated to be about 1 / 100 to 1 / 1000 of the vertical load. Also, in order to achieve alignment adjustment accuracy at the sub-micron 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 the control parameter. Therefore, in order to ensure the alignment accuracy while ensuring the compression thrust during bonding, 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 or rotational directions.

[0029] The range of air pressure controllable by the electro-pneumatic actuator is generally about -0.5 to 3 atm, and its upper limit is the buckling limit pressure of the bellows. Also, generally, the setting of analog quantity has a limit of resolution of about 14 to 16 bits (16,384 to 65,536). Therefore, as the pressure response of the stage for realizing sub-micron accuracy stage position control, about 1 mm / atm is appropriate. Also, a thrust force of about 1,000 N / atm is required in the vertical direction. Therefore, in addition to the diameter of the bellows, it is necessary to optimally design the plate thickness, shape, natural length, and presence or absence of juxtaposed springs of the bellows. At that time, it is desirable to independently control the positioning requiring accuracy and the elevating function requiring thrust.

[0030] When the stage is regarded as a rigid body, its degrees of freedom are 6 axes (x, y, z, θ, α, β). Therefore, in order to measure the position and angle of the stage, the distance between the side of the rigid body (stage) and the support (frame) may be measured at 3 points in the horizontal direction and 3 points in the side direction using a distance meter. In the bonding process, it is necessary to evaluate and minimize the relative displacement of the two chips. In particular, the displacement during pressurization is the cause of the decrease in the stop. Therefore, it is necessary to calculate the displacement of the alignment mark by image processing and perform real-time stage position correction including during pressurization.

[0031] When the sample is carried in, a gap of about several millimeters into which the robot hand can be inserted is required. On the other hand, the range required for precise alignment depends on the positioning accuracy of a chip transfer robot or the like and is within about ±200 μm. Also, the initial parallelism of the wafer can be kept within ±1 / 1000 radian (~0.06°). Therefore, in the spatial distance measurement that requires high accuracy for alignment, it is possible to limit the operating distance range to about 1 mm.

Means for Solving the Problem

[0032] In order to achieve the above object, the present invention uses a plurality of pneumatic bellows, and controls the pneumatic pressure introduced into the bellows at a positive pressure and a negative pressure within a range where buckling does not occur in the bellows, thereby controlling the spatial attitude and thrust without using a sliding part such as a cylinder or a ball joint. A pressurizing stage using pneumatic bellows, comprising: A 6-axis pressurizing stage is proposed, 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 in the vertical, horizontal, and rotational directions respectively.

[0033] On the basis of satisfying such a basic configuration, the present invention further A bellows with a large effective area is installed vertically, and the mounting angle of the bellows with a small effective cross-sectional area is set shallowly in the horizontal direction of the stage or with respect to the horizontal plane, thereby ensuring the thrust in the vertical direction and improving the positioning accuracy. A pressurizing stage according to claim 1 is also proposed.

[0034] In the present invention, on the basis of satisfying the above basic configuration, it has a redundant number of pneumatic bellows compared to the degrees of freedom of the stage, generates a tensile stress in the bellows with a small effective cross-sectional area and a compressive stress in the bellows with a large effective cross-sectional area, enhances the vertical thrust, and prevents buckling of the bellows. A pressurizing stage according to claim 1 is also proposed.

[0035] The present invention also proposes a pressurizing stage according to claim 1, characterized in that, while satisfying the above basic configuration, it has a number of the bellows greater than the six degrees of freedom when the stage is regarded as a rigid body, and adjusts the surface distribution of the pressurizing thrust of the stage.

[0036] The present invention further proposes a pressurizing stage according to claim 1, characterized in that the position and orientation of the stage in the three-dimensional space including the center coordinates, rotation, and pitching are detected by a non-contact position sensor, and pressurizing positioning is achieved by controlling the pressure supplied to the pneumatic bellows.

Effect of the Invention

[0037] In the conventional drive mechanism using a ball screw and a bearing stage, regardless of whether it is a serial link or a parallel link, there is a sliding part, and the use of lubricating oil is inevitable. The metal forming bellows used in the present invention combines the characteristics of a pneumatic cylinder and an elastic hinge, and there is no sliding part. Therefore, there is no dust generation due to friction or contamination by lubricating oil. In addition, the metal forming bellows is also a product used in vacuum piping, and is excellent in cleanliness and heat resistance.

[0038] In the pressurizing device, sufficient thrust is required in the vertical direction, while sub-micron level accuracy is required in the horizontal direction and pitching direction. On the other hand, considering the buckling of the bellows, the air source pressure, and the capacity of the vacuum exhaust pump, the appropriate setting range of the set air pressure is about -0.5 atm to 3 atm (0.3 MPa). For an electro-pneumatic actuator that generates air pressure by an electric signal, it is desirable to assume a micro pressure setting error of about 1 / 1000 to 1 / 10000 of the set air pressure range due to hysteresis, disturbance, etc. Therefore, it is necessary to match the pressure setting range by the electro-pneumatic actuator with the required stroke and thrust of the stage. That is, to control minute position displacement, a small-diameter bellows with a small thrust relative to the set pressure is used because small force adjustment is required. To ensure the thrust required in the pressurizing direction, a large-diameter bellows is used. Also, by adjusting the spring constant of the bellows according to the natural length and plate thickness of the bellows and optimizing the rigidity of the stage, it is possible to ensure the necessary and sufficient stage movement amount within the pressure setting range by the electro-pneumatic actuator.

[0039] Furthermore, by adjusting the connection angle of the bellows and the moving direction of the stage borne by the bellows, the thrust for each stage degree of freedom can be adjusted, improving the positioning accuracy and ensuring the thrust in the pressurizing direction. When the large-diameter bellows is installed vertically, horizontal displacement accompanying changes in the bellows thrust is less likely to occur. Also, by installing the small-diameter bellows horizontally, precise positioning can be performed by minute thrust adjustment. Furthermore, by setting the small-diameter bellows at a shallow angle from the stage surface, precise height adjustment becomes possible even in the vertical direction.

[0040] When using a number (6) of bellows equal to the degrees of freedom of the rigid body, it is necessary to generate both compressive and tensile stresses in the bellows with a small positioning diameter. Since the bellows with a small diameter have a low buckling limit pressure, there are limitations in the set pressure range. Also, as an electro-pneumatic actuator, it is essential to generate positive and negative pressures. Therefore, arrange a number of bellows more than the degrees of freedom of the rigid body, generate compressive stress in the vertically driving bellows with a large effective cross-sectional area to enhance the vertical thrust, and either extend the bellows with a small positioning diameter beyond its natural length or keep the inside of the bellows on the vacuum side to constantly generate tensile stress. This prevents buckling of the positioning bellows and enables control of the set pressure only on the positive pressure side.

[0041] Generally, in the polishing process, small-diameter semiconductor wafers tend to be higher in the center and lower at the periphery. Therefore, in order to achieve a uniform bond, it is necessary to make the thrust at the periphery larger than that at the center. Thus, it becomes possible to adjust the surface distribution of the pressurizing stage by increasing the number of vertically driving bellows at the center and the periphery.

[0042] Detect the position and orientation of the stage in the three-dimensional space including the center coordinates, rotation, and tilt by a non-contact position sensor, and control the pressure supplied to the pneumatic bellows, so that 6-axis pressurized positioning of the stage can be achieved without error accumulation. As the non-contact position sensor, various methods such as optical measurement and methods for measuring pressure and impedance changes due to the 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 object, a method for measuring the phase difference of the reflected wave of the Fabry-Perot resonator formed between the reference mirror and the object, or a method using the chromatic aberration of the condenser lens, etc. are composed of an optical system using an optical fiber and have an accuracy of about several nm to sub-micron.

[0043] In addition, a laser displacement meter using a triangulation method can also be used when the required stage accuracy is about 2 to 3 μm. Generally, there is a correlation between the measurement accuracy and the allowable angular deviation, and the assumed rotation amount of the stage also needs to be considered in the selection of an optical distance measuring instrument. Furthermore, like an air micrometer, a method of detecting a pressure change based on the distance between an air discharge hole and an opposing surface, a capacitance manometer, an inductive displacement measurement system, etc. can also be selected according to the required accuracy and operating environment. In the bonding 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 also possible to omit the horizontal distance meter.

Brief Description of Drawings

[0044]

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[0045] Below, we will show an example of the configuration of a pressure device that has six degrees of freedom (6DOF) or more metal bellows directly attached to the stage to ensure the thrust and precision required for a wafer or chip bonding device. In the case of a hexapod with rod length control, six extendable rods or seven strings are required to control the position of a stage with six degrees of freedom. Adding more control axes is effective for avoiding dead points, but since constraints are imposed on the combination of extendable lengths, there is a risk of excessive internal stress being generated in the controlled object due to control errors. On the other hand, in the case of force control in which actuators have spring constants according to the present invention, the equilibrium position is determined so that the elastic energy of multiple springs is minimized, regardless of the number of actuators, so that actuator redundancy does not impede controllability.

[0046] Metal bellows are available in welded and formed types. Both types are used in vacuum equipment that requires moving parts or alignment, in compliance with vacuum flange standards. Formed bellows are less expensive than welded bellows and are widely used for vacuum rough-cut exhaust pipes and connecting vacuum chambers together. Standard sizes are available in advance from various companies, such as Mirapro Co., Ltd. (1100 Anahira, Suwamachi, Hokuto City, Yamanashi Prefecture), Osaka Rasenkan Kogyo Co., Ltd. (3-12-33 Himeri, Nishiyodogawa-ku, Osaka City), Irie Koken Co., Ltd. (813 Kokusai Building, 3-1-1 Marunouchi, Chiyoda-ku, Tokyo), and Nangoku Flexikan Kogyo Co., Ltd. (5-9 Nittakitamachi, Daito City, Osaka Prefecture). In the present invention, a stainless steel formed bellows with moderate elasticity is used.

[0047] When these metal forming bellows are diverted to the pressurizing stage as pneumatic bellows, the specifications required are shown in Table 1, which satisfy a vertical stroke of 8 mm and a horizontal stroke of ±1 mm. Metal forming bellows with various thrusts can be designed according to the plate thickness, diameter, and shape of the corrugations. When the thrust of the elevating bellows is 600 - 1800 N per atmosphere, the flange nominal diameter corresponds to 65A - 150A, and the buckling limit is 0.2 - 0.7 MPa. For example, the effective area is 58.5 cm 2 The maximum thrust of a pressurizing device using three elevating bellows (Table 1: #65 - 1) with an effective area of 58.5 cm

[0048] 2 and a buckling pressure of 0.2 MPa is 3,600 N (600 N x 2 atmospheres x 3 pieces). 2 In the case of the small - diameter bellows (Table 1: #25 - 2) used for positioning bellows, the effective area is 12.5 cm

[0049]

Table 1

[0050] The spring constants of the bellows listed in Table 1 above indicate the repulsive force when displaced by 1 mm in the axial direction and the direction perpendicular to the axis. For example, since the spring constant in the axial direction of the lifting bellows (Table 1: #65-1) is 16.4 N / mm, the air pressure required to drive it by 1 mm is approximately 3 KPa. When moving the stage horizontally, the spring constant in the direction perpendicular to the axis of the bellows installed vertically is added as a resistance force. For example, since the pressure accuracy that can be set by an electro-pneumatic actuator with a pressure range of ±0.5 atm (1 atm = 0.1 MPa) is several tens of Pa, in order to improve the positioning accuracy of the pressurized stage, it is effective to adjust the plate thickness and shape of the bellows, or to install a spring in parallel so that the product of the rigidity of the entire stage and the required stroke is approximately the same as the thrust of the bellows. In Reference 7, in the control of one axis, an elastic hinge is installed in parallel with a metal bellows so that a displacement of 300 [μm] can be obtained for 400 [kPa].

[0051] In Table 1, even for the same nominal diameter, by changing the plate thickness and the shape of the corrugations, metal bellows with various spring constants can be selected. For example, in the bellows with a nominal diameter of 65A, by increasing the plate thickness from 0.2 to 0.4 mm, the buckling pressure increases from 0.2 to 0.51 MPa, and the spring constant increases from 16.4 to 94.7 N / mm according to the plate thickness. Since the spring constant in the direction perpendicular to the axis of the lifting bellows serves as a resistance force against the horizontal displacement of the 6-degree-of-freedom stage, by selecting an appropriate metal bellows, it is possible to design the required resistance force and stroke for the horizontal, vertical, and rotational directions without an additional spring.

[0052] Figure 1 shows a schematic diagram of a six-degree-of-freedom pressurized stage using a metal flexible bellows according to the present invention. On the bottom surface of a lifting stage 1 made of an aluminum alloy with a hexagonal shape of 223 mm per side and a thickness of 20 mm, three thick pneumatic bellows 2 for vertical drive (Table 1: #65-1) are provided. Also, on the side surface of the stage, three thin pneumatic bellows 3 for horizontal drive (Table 1: #25-2) are arranged at positions offset from the center of the stage. The horizontal bellows 3 are each 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 pitching (α: rolling, β: pitching), and the three horizontal bellows 3 mainly control the X, Y directions and the rotational direction around the Z axis (θ: yawing). The offset distance from the stage center gives a 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 ensured, and by making the diameter of the horizontal and rotational bellows smaller, the horizontal direction output with respect to the applied pressure is reduced, improving the positioning accuracy.

[0053] The axes of the three pneumatic bellows 3 for horizontal drive are generally orthogonal to the three vertical drive axes. Therefore, due to the expansion and contraction of the horizontal bellows, the stage moves horizontally with almost no vertical movement. However, in the arrangement of Figure 1, since the bellows axes are installed away from the central axis of the stage, translational and rotational movements occur simultaneously due to the expansion and contraction of each bellows. Therefore, in the case of only translational movement, it is necessary to adjust the pressure to cancel the rotational movement. Also, when the three pneumatic bellows 3 for horizontal drive expand simultaneously, the lifting stage 1 rotates clockwise.

[0054] The Z direction and pitching of the lifting stage 1 are measured by vertical distance sensors 4 arranged at three locations on the upper surface of the stage, and the X, Y directions and the rotational direction around the Z axis are measured by horizontal distance sensors 5 arranged at three locations on the side surface of the stage.

[0055] Figure 2 is a partial cross-sectional view showing the inside of the pneumatic bellows 2 for vertical drive. The upper flange 2-1, the stainless-steel flexible bellows 2-2, and the lower flange 2-3 are hermetically welded. Inside the lower flange, a cylindrical block provided with an air introduction hole 2-4 and an air discharge hole 2-5 is provided. By reducing the volume inside the bellows with the cylindrical block, the time response of the pneumatic control is improved. 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 vertical drive. In order to reduce the internal volume by the cylindrical block, it is desirable that the stage be driven along the bellows axis and that there be little displacement in the direction orthogonal to the bellows.

[0056] In Figure 3, a pneumatic bellows 6 (#65-1 in Table 1) for vertical drive is added at the center. Since the pneumatic bellows has a spring action and a force control action by air pressure, even if more than 6 mechanical degrees of freedom of the lifting stage 1 are connected, it will not become overconstrained. By increasing the number of pneumatic bellows for vertical drive, it becomes possible to finely adjust the correction of warpage and the starting position of the bonding surface in semiconductor wafer bonding.

[0057] Figure 4 shows an example in which four bellows for driving in the vertical direction are used, the same as in Figure 3. Around the thick central pneumatic bellows 6 for vertical driving (Table 1: #125-2) that bears the vertical load, three thin pneumatic bellows 2 for vertical driving (Table 1: #25-2) responsible for pitching motion and pneumatic bellows 3 for horizontal driving (Table 1: #25-2) responsible for horizontal movement and rotation are arranged. By reducing the diameters of the bellows for horizontal and pitching motions, the thrust force against pressure control is decreased, enabling precise positioning and pitching control. Generally, by increasing the diameter of the bellows, the elastic constant per corrugation increases in proportion to the diameter. Also, since the thrust force is proportional to the effective area of the bellows, the buckling limit thrust force increases in proportion to the cube of the bellows diameter. Conversely, when the diameter of the bellows is decreased, the buckling limit pressure decreases. However, by applying positive pressure to the thick central pneumatic bellows 6 for vertical driving and keeping the pneumatic bellows 2 for vertical driving with a small diameter in a decompressed state and adjusting the pressure so that tension is always applied, buckling can be prevented. Alternatively, by increasing the plate thickness of the thin pneumatic bellows 2 for vertical driving and stretching it in advance from its natural length to generate tensile stress, buckling can be prevented even under positive pressure.

[0058] Also, in Figure 4, instead of the horizontal distance sensors 5 arranged in Figures 1 and 3, two alignment microscopes 7 are used. By detecting the center coordinates of the two alignment marks 8 through image processing, rotation around the horizontal direction (X, Y) and the Z axis can be detected. As a digital camera used for the alignment microscope, for example, by binning from M160 manufactured by Toshiba Terry at 4-7-1 Asahi-gaoka, Hino-shi, Tokyo-to and limiting the number of pixels to about VGA (640x520 pixels), a frame rate of about 500 fps can be ensured even with a general-purpose CMOS camera. By using parallel image layer processing technology, the mark position can be detected with a time delay of about several msec, enabling in-situ observation and control during bonding. Note that the resolution using a 20x objective lens is about 1 μm.

[0059] Figure 5 shows the case where a hexapod using a conventional telescopic linear actuator and a universal joint is replaced with a metal bellows. In this configuration, six diagonal pneumatic bellows 9 (Table 1: #50-2) with a slightly larger diameter form three pairs. The angle formed by the bellows 9 and the normal line of the stage 1 is approximately 30°. As shown by the dashed lines in the figure, the axes of each pair of bellows intersect at three points above the stage. The bottom of each pair of bellows is arranged in contrast at a position rotated 45° from the line segment formed by the center of the stage, with the point where the axes of the pair of bellows intersect projected onto the bottom surface (not shown) as the reference point. The configuration in Figure 5 has the advantage that the design and arrangement are easy because the fixed surface of the bellows is flat and the shapes of the bellows and the fixing fixtures are all the same. On the other hand, with respect to the length L of the bellows, if the height H of the stage and the angle between the bellows and the normal line of the stage is α, then H = L·cos(α) < 1, and the length of the bellows required to obtain the same stroke becomes longer. On the other hand, since the thrust in the vertical direction becomes cos(α) times, the critical thrust considering buckling is disadvantageous by cos(α)^2. The thrust at the operating pressure (~0.2 MPa) of the buckling limit pressure of the diagonal pneumatic bellows 9, which is 0.28 MPa, is 268 N x 2. If the angle between the bellows and the normal line of the stage is 30°, the thrust from the six bellows becomes 2,800 N.

[0060] Figure 6 shows an example in which, in Figure 5, a thick pneumatic bellows 6 for vertical drive in the central part (Table 1: #100-2) bearing a vertical load is added. By pressurizing the pneumatic bellows 6 for vertical drive in the central part, the pressure on the surrounding diagonal pneumatic bellows 9 can be reduced or maintained at a pre-stretched position to generate tensile stress, and the buckling limit can be relaxed. Also, since the diagonal pneumatic bellows 9 does not require a vertical thrust, compared to Figure 5, it is installed shallower with respect to the stage (the angle between the normal of the bellows and the stage is ~60°), and a bellows with a smaller effective diameter (Table 1: #25-2) is used. That is, by reducing the diameter of the alignment adjustment bellows and adjusting the mounting angle, while preventing buckling, the stage drive amount per set pressure can be suppressed, enabling precise alignment. Since the buckling limit of the thick pneumatic bellows 6 for vertical drive in the central part (Table 1: #100-2) is about 0.3 MPa and the operating pressure is about 0.2 MPa, the maximum thrust of the stage is about 2,000 N.

[0061] Figure 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 by setting the pressure of a thin bellows with a low buckling pressure below atmospheric pressure or applying a pre-tension, it becomes a tensile state, and buckling can be avoided even with a long bellows. Therefore, a longer stroke in the horizontal direction can be ensured compared to the configuration of Figure 1. Also, a long bellows in the horizontal direction is advantageous in terms of service life with respect to the deformation perpendicular to the axial direction accompanying the stage lifting and lowering.

[0062] Regarding the controllability of a parallel link stage using pneumatic bellows, the stage displacement with respect to a constant load and the stage displacement with respect to the driving pressure applied to each pneumatic bellows were evaluated using a rigid body motion simulation program called pychrono (http: / / projectchrono.org / pychrono / ). An actual pneumatic bellows generates expansion / contraction or thrust with respect to pressure, and at both ends of the bellows, there is an elastic hinge action that generates resistance with respect to the inclination of the bellows. That is, a metal flex bellows can be modeled as a spring-damper with its both-end connection parts fixed by elastic hinges, a linear actuator that generates a force in the spring direction by air pressure. However, in this case, the spring constant of the hinge part was ignored, and the calculation was made assuming that the linear spring-damper is connected to a universal joint that does not generate torque. Therefore, the lateral stage rigidity is underestimated.

[0063] As an evaluation of the controllability of the pneumatic bellows stage, regarding the driving of each pneumatic bellows, sufficient stress should be generated with respect to the six degrees of freedom of the stage as a rigid body (no dead points exist). The vertical thrust should be larger than the other degrees of freedom. There should be as little interaction as possible between the stress on the stage and the driving force applied to the pneumatic bellows, particularly between the large vertical stress component with high usage intensity and the other stress components that require fine force control. From the perspective of buckling, a state where tensile stress (negative) is generated is desirable, etc. From these viewpoints, the spring-damper models corresponding to the pneumatic bellows arrangements in FIGS. 5, 6, 1, and 7 were analyzed.

[0064] FIG. 8 shows a schematic diagram corresponding to FIG. 5 for a pneumatic bellows stage with a hexapod arrangement. The stage is a disk with a mass of 7 Kg, a diameter of 400 mm, and a thickness of 20 mm. Spring dampers with a free length of 100 mm are arranged at an angle of 30° from the outer circumference of the disk with respect to the stage surface normal, and the projection angle of the bottom surface of the paired spring dampers is ±30°. The height of the stage is 77 mm. The spring constant is assumed to be 14,700 N / m corresponding to Table 1:#50-2, and the damping constant is assumed to be 10 N / (m / s). Further, in order to evaluate the rigidity of the stage, the resistance forces when rotated by 1° around each axis and displaced by 1 mm in the x, y, and z directions were calculated. FIG. 9 shows a calculation example of the stage rigidity matrix (A) and the spring resistance matrix (B) in FIG. 8. In this figure, the y direction is the vertical axis, the front left is the x axis, and the front right is the z axis.

[0065] FIGS. 10 and 11 show the calculation results of the free vibration waveforms of the stage in the X axis (A), Y axis (B), Z axis (C), and around the X axis (D), Y axis (E), and Z axis (F) after displacement by 1 mm in the x and y directions, respectively. In FIG. 10, a damped vibration with a period of 5 Hz in the horizontal direction (x direction (A)) was obtained, and in FIG. 11, a damped vibration with a period of 15 Hz in the vertical direction (y direction (B)) was obtained. When the initial condition was given only in the x direction, the amplitudes in the y and z directions were about 10 -5 degrees (FIGS. 10 (B), (C)), and with respect to rotation, an accompanying vibration of about 0.2° in the z-axis direction (FIG. 10 (F)) occurred. On the other hand, when the initial condition was given only in the y direction, only the vibration in the vertical (y-axis, FIG. 11 (B)) was observed. This corresponds to the fact that in FIG. 9, only the second column corresponding to forcey exists in the second row of the stage rigidity matrix element (A) corresponding to the y-direction displacement.

[0066] Still, in Fig. 9, positive corresponds to compressive stress and negative corresponds to tensile stress. In Fig. 9(A), the resistance in the vertical direction (y) is -53.2 N / mm, while the resistance in the horizontal directions (x, z) is -17.7 N / mm. Also, with respect to the displacement in the horizontal direction, torques of ±3.2 N are generated around the x and z axes, indicating that a rotational force is parasitically generated. In Fig. 9(B), the resistance generated by each spring is -11.4 N / mm for the displacement in the vertical direction (y), and forces with different polarities of about ±6 N / mm are generated for the displacement in the horizontal direction. Fig. 9(B) also shows that when the stresses corresponding to each column are generated, the stage moves and rotates in the six degrees of freedom directions from x, y, ---, to rotZ, respectively.

[0067] Fig. 12 shows a schematic diagram of a pneumatic bellows stage corresponding to Fig. 6 in which, in addition to the hexapod arrangement, a large-diameter pneumatic bellows (Table 1: #100-2) is arranged in the center and thin bellows (Table 1: #25-2) are arranged around it. By raising the height of the fixed points of the peripheral bellows, the mounting angle of the peripheral bellows is set shallowly (from the horizontal plane to ~30°), and the thrusts in the horizontal directions (x, z) and the vertical direction (y) in the peripheral bellows are set to be approximately equal. That is, the alignment adjustment is performed by the peripheral bellows, and by using the bellows at the center for pressurization, it is possible to improve the alignment accuracy in the horizontal, rotational, and pitching directions while maintaining the thrust in the vertical direction.

[0068] Figure 13 shows a calculation example of the stage stiffness matrix (A) and the spring resistance matrix (B) in Figure 12. The second row and second column (-23 N / mm) of the stage stiffness matrix (A) represents the vertical stiffness, which is larger than the horizontal stiffness (-7.3 N / mm). By utilizing the redundancy of the system, in the spring resistance matrix (B), the free length or air pressure is set so that a compressive stress (~200 N) is generated in the central bellows (sp0) in advance and a tensile stress (~ -90 N) is generated in the peripheral bellows (sp1 - sp6), thereby biasing the peripheral bellows into the tension mode and preventing buckling of the thin bellows. Also, by adding thick bellows with a large critical buckling pressure in the vertical direction, the vertical thrust can be enhanced. Figures 14 and 15 show calculation examples of the stage transient response with respect to the initial displacements in the x and y directions in Figure 12. Regarding the vibration modes, they are similar to Figures 10 and 11.

[0069] Figure 16 shows an analysis example of the pneumatic bellows pressurizing device corresponding to Figure 1. 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 direction 30° from the center of the stage in the horizontal direction. The spring constants are set to 16400 N / mm and 2500 N / mm respectively. Figure 17 shows a calculation example of the stage stiffness matrix (A) and the spring resistance matrix (B) in Figure 16. Compared with Figure 9, the stiffness in the y direction (49) is larger than that in the x direction (3.7), and no torque in the z - axis direction is generated with respect to the displacement in the x direction, so the independence of each axis is high. However, for example, when moving in the x direction as shown in the first column of Figure 17(B) or when rotating only in the vertical direction (rotY) as shown in the fifth column of Figure 17(B), in addition to sp1 - sp3 installed horizontally, it is necessary to adjust sp1vt - sp3vt installed vertically. Therefore, it is necessary to control the set pressures of the six bellows in parallel even during movement only in the plane direction.

[0070] In Figures 18 and 19, damped vibrations with a period of 5 Hz were obtained both in the horizontal direction (x - direction) and the vertical direction (y - direction). When the initial condition was given only in the x - direction, the amplitudes in the y (Figure 18(B)) and z - directions (Figure 18(C)) were 10 -5and 10 -9 To some extent, regarding rotation, about 10 around the x-axis (Fig. 18(D)). -5 and about 10 around the y-axis -3 Some accompanying vibrations are occurring. The accompanying vibrations are suppressed by two or more digits compared to Fig. 10 according to the hexapod arrangement. Also, when the initial condition is given only in the y-direction, only vibrations perpendicular (y-axis, Fig. 19(B)) are observed as in Fig. 10. This corresponds to the fact that in Fig. 17, only the matrix elements in the second row corresponding to the y-direction displacement exist in the second column corresponding to forcey. The degrees of freedom (DOF) of a rigid body constrained in a plane are 3, and it can be positioned by three springs, but it is necessary to apply both compressive and tensile forces to the springs. In fact, in Fig. 17(B), the signs of the spring resistances due to displacements in each axial direction are mixed.

[0071] Fig. 20 shows a stage schematic diagram when the pneumatic bellows shown in Fig. 7 is replaced with a spring-damper. By adding one redundancy in the horizontal direction, pre-tension can be given to the spring. In fact, in the spring resistance matrix (B) of Fig. 21, the resistances of force_sp1a, force_sp1b, force_sp2a, force_sp2b corresponding to the horizontal direction can all be set negative (tension). Calculation examples of the stage transient response for initial displacements in the x-direction and y-direction are shown in Figs. 22 and 23. For free vibrations with an initial amplitude of 1 mm in the x-direction (Fig. 22(A)) and y-direction (Fig. 23(B)), no accompanying vibrations in other directions occur. In fact, there are many zero components in the off-diagonal terms of the stage stiffness matrix (A) in Fig. 21, which makes positioning control easier. Also, in this configuration, since the horizontal bellows can be regarded as a string, a bellows with a small diameter and a long stroke that is not prone to buckling can be selected.

[0072] The air pressure setting range by the pneumatic actuator is appropriately about 3 atmospheres from vacuum to the buckling limit, and the setting accuracy has a limit of about 1 / 1,000 to 1 / 10,000 of the pressure range. Therefore, in the direction of determining the positioning accuracy of the pressurizing device, it is desirable to optimize the bellows diameter, consider the horizontal stage rigidity and the generated thrust in the horizontal direction, and minimize the necessary horizontal movement range of the stage in the settable pressure range (~1 mm or less). On the other hand, in the pressurizing direction, it is necessary to increase the bellows diameter and set the bellows axis vertically to ensure the required thrust. Also in this case, considering that the positioning accuracy in the vertical direction is proportional to the spring constant in the vertical direction, it is necessary to adjust the spring constant of the bellows in the vertical direction or add a coil spring or the like.

[0073] Hereinafter, more specifically, regarding the embodiment of the present invention when configuring an ultrasonic bonding device, an ultrasonic bonding device based on the air pressure bellows arrangement shown in FIG. 1 is shown in FIG. 24. Stopper-cum-supports 11 are provided at three locations on the side surface of the lifting stage 1 to connect the base plate 10 and the upper plate 12. Using the recess in the central portion, the lifting stage 1 is sandwiched, and the horizontal movement range of the stage is limited to ±1 mm and the vertical stroke is limited to 8 mm.

[0074] On the upper plate 12, laser interferometer type vertical distance sensors 4 are installed at three locations to perform measurement and control in the vertical and pitching directions. Also, on the side surfaces (three locations) of the supports 11, horizontal distance sensors 5 using triangular surveying type laser distance meters are provided to measure and control the horizontal stage position and rotation. Usually, an air actuator restricts the stroke only in the vertical direction with a sliding mechanism such as a cylinder, but by actively controlling the distances on the six-direction side surfaces, it becomes possible to uniquely determine the position and posture of the stage, and the sliding mechanism becomes unnecessary.

[0075] Above the lifting stage 1, an ultrasonic horn 13 is provided, and on the lower surface of the upper plate 12, a sample adsorption stage 14 is provided. For the introduction of semiconductor chips, a 4-axis manipulator 15 is used. First, lower the lifting stage 1 to the lower limit of the stopper, and adsorb and fix two semiconductor chips while inverting the directions of the ultrasonic horn 13 and the sample adsorption stage 14 respectively.

[0076] An infrared microscope 16 is provided on the upper plate 12. When the gap between the two semiconductor chips reaches about 20 μm, use the infrared microscope 16 to confirm the alignment marks of each semiconductor chip at multiple positions, and control the horizontal drive bellows so that the center positions of the alignment marks provided on each chip coincide.

[0077] While checking and finely adjusting the alignment position, raise the lifting stage 1, measure the variation of force versus displacement, and start ultrasonic vibration when the samples overlap. Further increase the load (pressure of the vertical drive bellows), and measure and control the displacement based on the predetermined (~2 μm) bump deformation at three locations using the vertical distance sensors 4.

[0078] For the alignment of the horizontal positions and rotation angles of the two chips by the alignment marks, at least two alignment marks are required. There are a method of measuring the deviation of a plurality of alignment marks by moving the infrared microscope 16 with the XY stage 17 and a method of simultaneously taking a plurality of images to measure the position and rotation angle. Measuring a plurality of images simultaneously is advantageous for kinematic control that requires high-speed position sampling, but for chip sizes equal to or smaller than that of the imaging chip of the infrared camera, an optical system such as split imaging is required. In addition, when performing image analysis of the alignment marks using the infrared microscope, the control by the horizontal distance sensor 5 provided on the side surface of the lifting stage 1 only needs to be accurate enough (~±50 μm) for the alignment mark image to enter the field of view of an objective lens with a relatively high magnification (~x20), so a relatively inexpensive triangulation type laser distance meter 5 is used.

[0079] A semiconductor wafer bonding apparatus based on the pneumatic bellows arrangement shown in Fig. 7 is shown in Fig. 25. The hatched portion shows a partial cross section. In the pneumatic bellows arrangement shown in Fig. 7, since the horizontal drive bellows 3 are arranged symmetrically on both sides, there is an advantage that a wide wafer loading path can be taken. 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 tip direction of the block for reducing the pneumatic capacity inside the bellows.

[0080] In the case of wafer bonding, 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 lifting stage 1 and the vertical and horizontal drive bellows is also heated. The heat resistance of the bellows drive part is ~100 - 150°C when using a byteon or Teflon O-ring 21 at their base seal part, and about 300°C in the case of a welded seal structure without using an O-ring. Also, since the bellows are made of stainless steel thin plates with relatively poor thermal conductivity, a temperature difference of 100°C or more can be provided between the part in contact with the stage surface and the base. That is, it has much higher heat resistance compared to stages using high-load bearings where the use of lubricating oil is inevitable and piezoelectric elements with Curie point limitations. Also, it has less influence such as dust generation due to sliding and it is easy to maintain a clean environment.

[0081] Three vertical distance sensors 4 and two infrared microscopes 16 are provided on the upper plate. 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 4-inch compound semiconductor wafer 18. By measuring the center positions of the respective alignment marks with the two infrared microscopes 16, the rotation amounts in the horizontal (X, Y) directions and the vertical (Z) direction can be calculated.

[0082] The three vertical bellows 2 can generate vertical stress proportional to the injection pressure respectively. Therefore, after wafer contact, it is possible to perform a mimicking operation with a constant pressure at three points, and it is also possible to ensure a constant gap for bonding by controlling the six degrees of freedom of the stage. For example, when performing 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 wafers constant.

[0083] As described above, in a chip or wafer bonding device that requires a load of several hundred to several tens of thousands of N, while limiting the stroke required for bonding, a six-degree-of-freedom alignment pressurizing stage using a pneumatic bellows that is inexpensive and resistant to a clean environment has been realized. Depending on the required alignment accuracy, various non-contact distance measurement devices including image recognition processing can be used. Simultaneously measure the six degrees of freedom required for table attitude control, and calculate and output the pressure to six or more pneumatic bellows in an inverse dynamics manner. Since the natural frequency of the stage is about 100 Hz, the attitude of the stage is measured at a time interval of 1 msec, preferably 100 μS, and the air pressure is controlled to ensure a position accuracy of sub-micron or less.

[0084] It should be considered that all aspects of the embodiments disclosed this time are illustrative and not restrictive. The scope of the present invention is not limited to the embodiments disclosed this time, and it is intended that all modifications within the scope shown by the claims or within the scope equivalent to the claims are included.

Explanation of Signs

[0085] 1: Lifting stage 2: Pneumatic bellows for vertical drive 2-1: Lifting 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: Pneumatic bellows for horizontal drive 4: Vertical distance sensor 5: Horizontal distance sensor 6: Pneumatic bellows for vertical drive of the central part 7: Alignment microscope 8: Alignment mark 9: Diagonal pneumatic bellows 10: Base plate 11: Stopper and support column 12: Upper plate 13: Ultrasonic horn 14: Sample adsorption stage 15: 4-axis manipulator 16: Infrared microscope 17: XY stage 18: 4-inch wafer 19: 6-inch wafer 20: Lower sample heating stage 21: O-ring 22: Spring

Claims

1. A parallel link pressurization stage that uses a plurality of pneumatic bellows, controls the pneumatic pressure introduced into the bellows at positive and negative pressures within a range where buckling does not occur in the bellows, controls the spatial attitude and thrust, does not include a sliding part using pneumatic bellows, and has excellent cleanliness and environmental resistance; Six or more of these bellows are directly connected to the stage for position and force control in the vertical, horizontal, and rotational directions corresponding to six degrees of freedom when the stage is regarded as a rigid body; It has a simultaneous and parallel pneumatic pressure feedback mechanism to the bellows; The spatial arrangement, effective cross-sectional area, elastic constant, and natural length of the above-mentioned bellows are changed according to different thrusts and strokes corresponding to the specifications in the vertical, horizontal, and rotational directions respectively; In a six-degree-of-freedom pressurization stage characterized by; By installing the above-mentioned bellows with a large effective area for applying thrust in the vertical (pressurization) direction and setting the installation angle of the above-mentioned bellows with a small effective cross-sectional area for moving in the horizontal, rotational, and pitching directions shallowly in the stage horizontal direction or with respect to the horizontal plane, the positioning accuracy is improved; A pressurization stage characterized by.

2. Tension is applied to the horizontally long bellows with a small effective cross-sectional area, and thrust is generated in the vertically (pressurization) short bellows with a large effective cross-sectional area to enhance the vertical thrust while preventing buckling of the bellows; The pressurization stage according to Claim 1, characterized by.

3. Having more of the above-mentioned bellows than six degrees of freedom when the above-mentioned stage is regarded as a rigid body, and adjusting the surface distribution of the pressurization thrust of the above-mentioned stage; The pressurization stage according to Claim 1, characterized by.

4. Detecting the position and attitude of the above-mentioned stage in the three-dimensional space including the center coordinates, rotation, and pitch by a non-contact position sensor, and performing pressurization positioning by controlling the pressure supplied to the above-mentioned pneumatic bellows; The pressurization stage according to Claim 1, characterized by.

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