JPH09264733A - Measuring method for flatness of high-temperature specimen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring method in which the flatness of a measuring face at a high-temperature specimen such as a bonding tool or the like for mounting of a semiconductor element is measured with good accuracy and stably by using an optical detector such as an interferometer or an optical displacement meter. SOLUTION: The flatness of a tip pressure face (a measuring face) 1a at a bonding tool (a high-temperature specimen) 1, for mounting of a semiconductor element, which is used in the temperature range of about 400 to 650 deg.C is measured by using an interferometer. At this time, the flatness is measured in a state that the high-temperature specimen 1 is situated inside a vacuum chamber 4. Since the high-temperature specimen 1 is situated in a vacuum atmosphere, a fluctuation in the heated air around the high-temperature specimen 1 is hardly generated, an air density distribution due to a fluctuation in the air in the measuring optical path of the interferometer is hardly changed, a measuring noise is reduced sharply, and the flatness of the tip pressure face can be measured with good accuracy and stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flatness measuring method for precision processed products or resin molded products in a high temperature state,
Especially, when mounting semiconductor elements such as ICs, TAB (Tape
The present invention relates to a flatness measuring method for a high temperature object, which is applied to the flatness measurement of a tip pressing surface of a bonding tool used as a crimping tool in a wireless bonding of an Automated Bondig method.

[0002]

2. Description of the Related Art As an example of measuring the flatness of an object in a high temperature state, a method for measuring the flatness of a tip pressing surface at a working temperature (400 to 650 ° C.) of the bonding tool for mounting a semiconductor element is disclosed in Japanese Patent Application Laid-Open No. Hei 5 (1999) -54. -326642. In this flatness measuring method, as shown in FIG. 5, a plurality of wires 52 made of a soft material such as gold each having the same diameter are arranged in parallel on a substrate 51 having a flat surface, and the plurality of wires 52 are arranged. The tip pressing surface 53a of the bonding tool 53 heated to the operating temperature is attached to the base 51.
The wire 52 is deformed along the distal end pressing surface 53a by pressing the wire 52 in a direction orthogonal to. Thereafter, the displacement amount of each wire 52 in the direction orthogonal to the base body 51 at room temperature is measured by a stylus displacement meter 54 as shown in FIG. 6, and the tip of the bonding tool 53 is indirectly pressed. The flatness of the surface 53a is obtained. The pressing surface of the tip of the bonding tool is polycrystalline diamond, single crystal diamond, diamond sintered body, C
It is made of a hard substance such as BN (cubic boron nitride), and the tip pressing surface is polished based on the measurement result of the flatness so as not to cause peeling between the electrodes of the semiconductor chip and the leads or defective bonding.

[0003]

However, in the above-mentioned conventional method for measuring the flatness of the high temperature object, since it is an indirect measuring method in which the shape of the measurement surface (tip pressing surface) is transferred onto a plurality of wires, There is a problem in that the transferred shape itself changes in shape from the high temperature state to the normal temperature state, the transferred shape and the measurement surface shape do not match, and the measurement accuracy decreases.

On the other hand, as a non-contact measuring method of flatness of a high temperature object, flatness of a hot rolled steel sheet is measured in a hot rolling line in the steel industry by using a semiconductor laser and a steel sheet for irradiating the steel sheet with laser light. To image the laser spot of
It is known to use an optical displacement gauge (displacement sensor) which is an optical detector for detecting the shape displacement information of the hot-rolled steel sheet by (position detecting element). However,
Conventionally, there is no suitable method for measuring the flatness of a high-temperature test object that requires a measurement accuracy of 0.1 μm or less.

The present invention has been made in view of such circumstances, and accurately and stably measures the flatness of an object in a high temperature state such as a TAB type bonding tool using an optical detector. An object of the present invention is to provide a method for measuring the flatness of a high temperature object, which is capable of performing the measurement.

[0006]

In order to achieve the above object, the invention of claim 1 irradiates the measurement surface with light from a light source and receives the reflected light to detect shape displacement information of the measurement surface. In the flatness measurement method for a high temperature object, which measures the flatness of the measurement surface of the high temperature object using an optical detector, perform the flatness measurement in a state where the high temperature object is placed in a vacuum atmosphere. It is characterized by. The invention of claim 2 uses the interferometer as the optical detector in the method for measuring flatness of a high temperature object according to claim 1, and aligns the optical axis between the interferometer and the measurement surface of the high temperature object. In order to achieve this, the high temperature subject is finely tilted, and the tilt of the measurement surface is adjusted.

Using an optical detector, the measurement surface of the object under high temperature (for example, the tip pressing surface of the bonding tool)
When measuring the flatness of, when the high temperature object is in the atmosphere, the heated air around the high temperature object is disturbed and fluctuates, and the air density distribution in the measurement optical path by the optical detector fluctuates. Measurement noise (measurement error) occurs in
Flatness cannot be measured accurately and stably. On the other hand, in the flatness measuring method according to the first aspect of the present invention, the high temperature object is subjected to a vacuum atmosphere (for example, the degree of vacuum: 1 milliTorr).
Since the flatness measurement is performed in a state of being positioned within 10 mm Torr), the fluctuation of the air density distribution due to the fluctuation of the air in the measurement optical path is almost eliminated, and the measurement noise is greatly reduced, and the flatness is reduced. The measurement can be performed accurately and stably.

A typical example of the optical detector is a combination of a semiconductor laser (light source) and a position detecting element (PSD), and displacement measurement (flatness measurement) is performed by a triangulation method or a light quantity detection method. The optical displacement meter and the interferometer are mentioned. As is well known, an interferometer obtains interference fringes according to the degree of unevenness of the measurement surface by light wave interference from the measurement surface (test surface) and a reference reference surface, and the flatness of the measurement surface is obtained based on this interference fringe. It measures the degree. When attempting to measure flatness with a measurement accuracy of 0.1 μm or less, the distance (working distance) between the optical displacement gauge head and the measurement surface is generally about 10 mm, while the distance between interferometers is about 10 mm. Is generally several tens of cm, which can be considerably longer than that of an optical displacement meter.

In the interferometer, the measurable area (flatness range) is on the order of several wavelengths (= several microns) of the used light wave, and the unevenness of the measurement surface is larger than this and the measurement surface is larger. If there is a height difference due to tilting, the pitch between adjacent interference fringes becomes too fine and measurement becomes impossible. For this reason, when measuring the flatness of the tip pressing surface when using the above-mentioned TAB method bonding tool using an interferometer (for example, at a high temperature of about 500 ° C.), heat the bonding tool from room temperature (room temperature). In the process, the tip pressing surface (measurement surface) is slightly tilted due to thermal deformation of the bonding tool itself, and if it is left as it is, it will deviate from the measurable area of the interferometer. It is necessary to adjust the inclination of the tip pressing surface and align the optical axis of the tip pressing surface, which is the measurement surface, with the interferometer.

Therefore, in the flatness measuring method according to the second aspect of the present invention, when the interferometer is used as the optical detector, the measurement is performed by thermal deformation of the object in the process of heating from room temperature to the predetermined measurement temperature. Even when the surface is slightly tilted,
The high-temperature object is finely tilted and the tilt of the measurement surface is adjusted to align the optical axis between the measurement surface of the high-temperature object and the interferometer, so the interferometer can be used to move out of the measurable range. The flatness measurement can be performed without the need.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the structure of a flatness measuring apparatus for a high temperature object used for carrying out the method of the present invention. Here, the case where the present invention is applied to the measurement of the flatness of the tip pressing surface of the TAB type bonding tool will be described.

As shown in FIG. 1, a flatness measuring apparatus for a high temperature object has an object support base 2 for supporting a bonding tool 1 which is a high temperature object through a heat insulating member (not shown) made of quartz glass, and a bonding tool. The plate-shaped movable table 3a, which has a square shape in a plan view, on which the subject support base 2 supporting the tool 1 is placed is shown in the front and back directions (X direction) in the drawing.
And a left-right direction (Y direction), respectively, and the tip pressing surface (measurement surface) 1a of the bonding tool 1 is inclined.
Tilt adjusting stage 3 for adjusting the tilt of the object, a vacuum chamber 4 for housing these, and an optical glass (quartz glass) having a flatness of 0.02 μm or less, which is arranged above the observation window 4a of the vacuum chamber 4. Parallel light is incident on the tip pressing surface (measurement surface) 1a of the bonding tool 1 through the observation window 4a, and the reflected light is received again through the observation window 4a, and the reflected light is detected according to the unevenness of the tip pressing surface 1a. And an interference fringe analysis unit 6 for obtaining a flatness profile in the measuring direction of the tip pressing surface 1a based on the interference fringe image. Has been done.

The bonding tool 1 itself arranged in the vacuum chamber 4 is heated by a heater wire (not shown) mounted in the heater mounting hole 1b, and the temperature thereof is the thermocouple mounted in the thermocouple mounting hole 1c. It is measured from the temperature conversion output (not shown).

Further, the subject tilt adjusting stage 3 is
As shown in FIG. 1, the fixed table 3b is provided at a total of 3 points including the fulcrum 3c and the advancing / retreating axes of the two electric actuators 3d.
The movable table 3a is supported on the upper side, and the movable table 3a can be tilted in each of the two directions by finely moving the shafts of the electric actuators 3d that move in the vertical direction in the drawing. The electric actuator 3d is a combination of a small motor, a gear head, and an advancing / retreating shaft. The tilt adjustment of the movable table 3a by the two electric actuators 3d can be remotely performed from the outside of the vacuum chamber 4. Similarly, heating control of the bonding tool 1 by the above-mentioned heater wire,
Also, temperature measurement with a thermocouple can be performed from outside the vacuum chamber 4.

The interferometer head section 5 is shown in FIG.
As shown in, the optical system of the Fizeau interferometer is constructed. In this head unit 5, the light from the light source 5a is
The light passes through the half mirror 5b and is collimated by the collimator lens 5c. The reference reference surface 5d arranged in front of the collimator lens 5c is a half mirror and is a highly precise flat surface. The light reflected by the reference reference surface 5d returns toward the light source 5a, is reflected by the half mirror 5b, and enters the industrial TV camera 5f via the lens 5e.

On the other hand, the light passing through the reference reference surface 5d, passing through the observation window 4a of the vacuum chamber 4 and arriving at the tip pressing surface 1a of the bonding tool 1 is also reflected and returned toward the light source 5a, and the half mirror 5b and The light enters the industrial TV camera 5f through the lens 5e. At this time, the reference reference surface 5d
The reflected light from the front surface and the reflected light from the tip pressing surface 1a, which is the measurement surface, interfere with each other in two wavefronts, and the tip pressing surface 1
Interference fringes corresponding to the unevenness of a are generated. The interference fringes are picked up by the industrial TV camera 5f, the interference fringe image is given to the interference fringe analysis unit 6, and the interference fringes analysis unit 6 measures the flatness profile of the tip pressing surface 1a in the measurement direction. Has become.

The flatness profile of the tip pressing surface 1a of the bonding tool 1 was measured by the following procedure using the flatness measuring device having the above-mentioned structure. In this example, the distance between the interferometer head portion 5 (the position of the reference reference surface 5d) in FIG. 1 and the tip pressing surface 1a of the bonding tool 1 located in the vacuum chamber 4 is about 200 mm. The distance between the pressing surface 1a and the observation window 4a of the vacuum chamber 4 is about 100 mm.

[Procedure 1] First, the movable table 3 of the subject tilt adjusting stage 3 set in the vacuum chamber 4
The subject support base 2 supporting the bonding tool 1 is placed on a. A heater wire and a thermocouple (not shown) are attached to the mounting holes 1b and 1c of the bonding tool 1, respectively.

[Procedure 2] Atmosphere, normal temperature (25 ° C.)
Prior to the flatness measurement in 1., the optical axes of the interferometer head 5 and the tip pressing surface 1a of the bonding tool 1 are aligned.
That is, when the reference reference surface 5d of the interferometer head portion 5 and the tip pressing surface 1a which is the measurement surface are substantially parallel to each other, the industrial TV
Since the interference fringes are observed by the camera 5f, the tilt of the bonding tool 1 is adjusted by the subject tilt adjusting stage 3 so as to obtain the interference fringes, and the optical axis is aligned.

[Procedure 3] The flatness profile of the rectangular tip pressing surface 1a of the bonding tool 1 at room temperature is measured by the interferometer head unit 5 and the interference fringe analyzing unit 6 whose optical axes are aligned.

[Procedure 4] Next, the inside of the vacuum chamber 4 is decompressed to maintain a predetermined degree of vacuum, while the bonding tool 1 (tip pressing surface 1a) is heated to its operating temperature and maintained at this temperature. Here, since the operating temperature of the bonding tool 1 is generally in the range of about 400 to 650 ° C., the degree of vacuum in the vacuum chamber 4 has an effect of reducing the above-mentioned fluctuation of air that causes a decrease in accuracy of flatness measurement. It may be set in the range of 1 mmTorr to 10 mmTorr so as to be obtained. In this example, the flatness profile at a use temperature of 500 ° C. is to be measured, and the degree of vacuum is set to 5 mmTorr.

[Procedure 5] The tip pressing surface 1 is caused by the thermal deformation of the bonding tool 1 itself caused by the heating in the procedure 4.
Since a is inclined and the parallel relationship of the interferometer head 5 with respect to the reference reference plane 5d is deviated, a vacuum atmosphere, high temperature (5
Prior to the flatness measurement at (00 ° C.), the tilt of the tip pressing surface 1a is adjusted by using the specimen tilt adjusting stage 3 to align the optical axes of the interferometer head 5 and the tip pressing surface 1a in a high temperature state. To do.

[Procedure 6] After the optical axis alignment, the temperature is set to 500.
The flatness profile of the rectangular tip pressing surface 1a of the bonding tool 1 at 0 ° C. is measured. In this example, the flatness measurement at room temperature was performed in steps 2 and 3 above, but if only the flatness profile at high temperature is required,
Of course, the above steps 2 and 3 are unnecessary.

A concrete example of the measurement result of the flatness profile of the rectangular tip pressing surface 1a of the bonding tool 1 in a high temperature state is shown in FIG. FIG. 3 shows a flatness profile of the tip pressing surface at a temperature of 500 ° C. For comparison, FIG. 4 shows the flatness profile of the tip pressing surface at room temperature (25 ° C.).

As can be seen from FIGS. 3 and 4, the flatness of the tip pressing surface at a high temperature of 500 ° C. is 0.05 μm in this example in the same manner as the flatness measurement at room temperature shown in FIG.
Stable measurement was possible with a measurement accuracy of m or less. And
Regarding this bonding tool, the tip pressing surface forming a convex surface at room temperature changes to a concave surface at a high temperature of 500 ° C., and the flatness at room temperature (about 0.95 μm: maximum and minimum values of unevenness) It is possible to know that the flatness (about 0.4 μm) in a high temperature state is smaller than that of the bonding tool and is excellent as a bonding tool. According to the method of the present invention, it is possible to accurately judge the quality of the bonding tool. You can

FIG. 2 is a schematic diagram showing another structural example of the flatness measuring apparatus for a high temperature object used for carrying out the method of the present invention. Here, a case will be described in which an optical displacement meter is used as an optical detector instead of the interferometer to measure the flatness of the tip pressing surface of the TAB type bonding tool.

As shown in FIG. 2, this flatness measuring apparatus for a high temperature object is a bonding tool 1 which is a high temperature object.
Object support base 2 for supporting the object support via a heat insulating member (not shown) made of quartz glass, a vacuum chamber 8 accommodating the object support base 2 and having a radiant heat cutoff filter 7 attached as a window portion, and the radiant heat cutoff. An optical displacement meter 9 arranged above the filter 7 and the optical displacement meter 9
And a drive device 10 for driving in the measurement direction.

As the radiant heat cutoff filter 7, an optical filter (for example, quartz glass) which transmits only the laser light source light from the optical displacement meter 9 and its reflected light is used. The infrared rays of the radiant heat are in a wavelength range longer than that of the light from the laser light source, and thus are reflected or absorbed by the radiant heat blocking filter 7. The distance between the optical displacement meter 9 and the tip pressing surface 1a of the bonding tool 1 located in the vacuum chamber 4 is set to about 10 mm in order to measure the flatness with a measurement accuracy of 0.1 μm or less. ing.

When the flatness profile of the tip pressing surface 1a of the bonding tool 1 is measured by using the flatness measuring device having the above-mentioned structure, as shown in FIG. 1a (measurement surface) is an optical displacement meter 9
The bonding tool 1 is mounted so that the tip pressing surface 1a of the bonding tool 1 is parallel to the moving direction of the optical displacement meter 9 driven by the drive device 10. Then, the bonding tool 1 is heated to a working temperature of, for example, 500 ° C., the inside of the vacuum chamber 8 is maintained at, for example, a vacuum degree of 5 mmTorr, and the driving device 10 moves the optical displacement meter 9 in the direction of the arrow shown in the drawing to cause laser The displacement amount of the tip pressing surface 1a, that is, the flatness is measured by scanning the tip pressing surface 1a with light and detecting the reflected light.

As described above, since the flatness measurement is performed while the bonding tool 1 at a high temperature of 500 ° C. is positioned in the vacuum atmosphere, the fluctuation of the air density distribution due to the fluctuation of the air in the measurement optical path is performed. Since the noise is almost eliminated, the measurement noise is drastically reduced, and the flatness can be measured accurately and stably. Further, when the distance between the optical displacement meter 9 and the measurement surface needs to be close to about 10 mm as in this example, the radiant heat cutoff filter 7 is used to radiate the radiant heat from the bonding tool 1 which is a high temperature object. Is blocked, and the optical displacement meter 9 does not malfunction due to heat damage.

[0031]

As described above, according to the method of measuring the flatness of a high temperature object according to the present invention, an optical detector such as an interferometer or an optical displacement meter is used to measure 400 to 65 degrees.
When measuring the flatness of the measurement surface of a high temperature test object such as a bonding tool for mounting a semiconductor element used in a temperature range of about 0 ° C., the flatness measurement is performed while the high temperature test object is placed in a vacuum atmosphere. As a result, fluctuations in the heated air around the high temperature subject are hardly generated, and there is almost no fluctuation in the air density distribution due to fluctuations in the air in the measurement optical path of the optical detector. Is greatly reduced, and the flatness can be measured accurately and stably.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a flatness measuring apparatus for a high temperature object used for carrying out a method of the present invention.

FIG. 2 is a configuration diagram schematically showing another configuration example of the flatness measuring apparatus for a high temperature object used for carrying out the method of the present invention.

FIG. 3 is a view showing a result of measuring flatness of a pressing surface of a bonding tool tip at a temperature of 500 ° C.

FIG. 4 is a diagram showing a measurement result of flatness of a pressing surface of a bonding tool tip at room temperature (25 ° C.).

FIG. 5 is a diagram for explaining a conventional technique.

FIG. 6 is a diagram for explaining a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Bonding tool (high temperature test object) 1a ... Tip pressing surface (measurement surface) 1b ... Heater mounting hole 1c ... Thermocouple mounting hole 2 ... Test object support stand 3 ... Test object tilt adjusting stage 3a ... Movable table 3d ... Electric actuator Four
... vacuum chamber 4a ... observation window 5 ... interferometer head 5a ... light source 5b
... Half mirror 5c ... Collimator lens 5d ... Reference reference plane 5e ... Lens 5f ... Industrial TV camera 6 ...
Interference fringe analysis unit 7 ... Radiant heat blocking filter 8 ... Vacuum chamber 9 ... Optical displacement meter 10 ... Driving device

Claims (2)

[Claims] 1. A flatness of a measurement surface of a high temperature object is measured by using an optical detector which irradiates a measurement surface with light from a light source and receives reflected light to detect shape displacement information of the measurement surface. A method for measuring flatness of a high temperature object to be measured, characterized in that the flatness measurement is performed in a state where the high temperature object is positioned in a vacuum atmosphere. 2. An interferometer is used as the optical detector,
The flatness of the high temperature object according to claim 1, wherein the high temperature object is finely tilted to adjust the tilt of the measurement surface in order to align the optical axis between the interferometer and the measurement surface of the high temperature object. Degree measuring method.