Measuring and testing – Specimen stress or strain – or testing by stress or strain... – By loading of specimen
Reexamination Certificate
2002-01-28
2003-12-30
Noori, Max (Department: 2855)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
By loading of specimen
Reexamination Certificate
active
06668662
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a viscoelasticity measuring device to measure viscoelasticity properties and particularly to a viscoelasticity measuring device to measure viscoelasticity properties by imparting a displacement profile to a sample presser.
2. Description of the Related Art
Conventionally, there have been various methods proposed to measure viscoelasticity. As a means for conducting a measurement of static viscoelasticity, there are, for example, a stress relaxation measuring method in which a certain strain is imparted to a sample to measure a changing stress, a creep measuring method in which a certain stress is imparted to a sample to measure a changing strain, a stress/strain measuring method in which a certain strain speed is imparted to a sample, etc.
As a means for conducting a dynamic viscoelasticity measurement, there are Torsion-pendulum method (ISO6721 part 2, JIS K7244-2), Flexural vibration—Resonance-curve method (ISO6721-3), Tensile vibration—Non-resonance method (ISO6721-4), Flexural vibration—Non-resonance method (ISO6721-5), Shear vibration—Non-resonance method (ISO6721-6), Torsional vibration—Non-resonance method (ISO6721-7), and so on.
These measuring processes are being used in the field of semiconductor manufacturing; for example, in the measurement of the viscoelasticity properties of an abrasive cloth used for polishing semiconductor wafers or the like.
Such abrasive cloths used for polishing semiconductor wafers are in general made of polymeric materials of various properties and structures, including polyester non-woven cloths or foam polyurethane sheets.
The mechanical properties and particularly viscoelastic behaviors of such abrasive cloths can seriously affect the distribution of pressure exerted to materials to be polished (such as semiconductor wafers) to such an extent it is known that the materials, structures and viscoelastic properties after aging of the abrasive cloths influences the abrasive accuracy of the materials to be polished.
Therefore, abrasive cloths have so far been subjected to various viscoelasticity measurements.
Conventionally and in general, the viscoelasticity measurement of the abrasive cloths used for polishing the semiconductor wafers or the like was conducted on the basis of the measurement of hourly change in their deformation, that is, a creep deformation of the abrasive cloths was measured under a certain load thereof.
In the static measurement, however, it was impossible to realize conditions for imparting a forced displacement in an extremely short time and eliminating the conditions in an extremely short time in the static measurement and to conduct measurements under repeated loads other than stable vibrations in the creep measurement.
On the other hand, the behaviors of the abrasive cloths observed at the time of actual abrasion works are repeated in the form of forced displacement and recovery. Therefore, a means for measuring the viscoelasticity of the abrasive cloths under the condition similar to the actual behaviors of the abrasive cloth during the abrasion operation has long been wished for.
As one means for measuring the viscoelastic behaviors of abrasive cloths used for polishing semiconductor wafers or the like, the forced displacement measuring method may be considered. Therefore, the case of conducting measurements by the forced displacement measuring methods will be explained referring to
FIG. 5
, which shows the general structure of the conventional measuring device.
In the figure, the numeral
21
denotes a stage which is adapted to vertically move and support a sample
22
thereon. Above the sample
22
, there is provided a rod
23
with an upper end portion thereof secured and a lower end face thereof attached with a load cell
24
. Upon the upper surface of the sample
22
, there is provided a presser
25
adapted to press the sample
22
, the presser having an upper end portion adapted to contact the load cell
24
.
Further, the stage
21
is attached with a stand
26
, which has a tip portion provided with a laser displacement meter
27
to indicate the displacement of the sample
22
by measuring the displacement of the presser
25
.
Then, the above arrangement is adapted to obtain viscoelastic properties by placing the sample
22
on the stage
21
and the presser
25
on the sample
22
. At this time, care is to be taken to bring the upper portion of the presser
25
into contact with the load cell
24
. Thus arranged, the laser displacement meter
27
is subjected to an origin correction such that the resultant position is defined as an origin thereof.
Thereafter, the stage
21
is vertically reciprocated to displace the same such that the measurement is started. The displacement of the sample is measured by the laser displacement meter
27
. In addition, the load generated by the displacement and applied to the sample
22
by the presser is measured by the load cell
24
.
Then, the stress generated in the sample is sought in addition to obtaining the displacement. More specifically, the measurement result of the viscoelasticity properties of the abrasive cloth used for polishing the semiconductor wafer is shown in FIG.
6
.
As will be understood from the
FIG. 6
, the viscoelasticity properties of the abrasive cloth indicates that an increased displacement causes an increased stress to such an extent that the stress reducing to nil will not reduce the displacement to nil.
In this connection, there is a problem that the
FIG. 5
device compresses the sample (the abrasive cloth) but will not cause no immediate displacement the moment a load is applied due to a problem of accuracy concerning the speed and position controls of the vertical stage reciprocation because of the vertical mechanism used in the stage.
Particularly, as the stress increase is limited at the time of the compression (or displacement), there remains a technical problem that the result is different from the viscoelastic properties under the actual use conditions.
In this way, the device fails to offer the displacement profile equal to that under a condition similar to the actual use conditions with the result that the technical problem means it is impossible to measure viscoelastic properties under a condition close to the actual use conditions.
SUMMARY OF THE INVENTION
The present invention is directed to solving the above described technical problems and to provide a viscoelasticity measuring device which imparts a desired displacement profile to a sample such that its viscoelastic behaviors under a use condition close to the actual use conditions.
The viscoelasticity measuring device according to the present invention which imparts a sample a predetermined displacement to measure a resultant displacement and stress comprises a presser to impart displacements to a sample; a rod to convey the displacements to the presser; a control jig kept in contact with an upper end portion top of the rod and adapted to move to impart a desired displacement to the rod; a load cell which detects a load exerted to the sample to detect a stress generated in the sample; and a displacement sensor to detect the displacement of the sample; the displacements imparted to the sample being defined in accordance with a configuration and a moving speed of the control jig.
In this way, as the displacement imparted to the sample is defined by the configuration of the control jig and its moving direction, the movement of the control jig will impart the displacement profile to the sample.
Therefore, the elimination of vertical movement as done in a stage in the conventional device will minimizes the adverse effect of inertia such that precise speed and position controls are ensured. As a result, it is possible to impart a desired displacement to the sample and measure viscoelastic behaviors under conditions close to actual use conditions.
Here, it is preferred that a predetermined displacement is imparted to the sample by defining a desired configuration to be imparted to the sample
Isogai Hiromichi
Kojima Katsuyoshi
Masunaga Takayuki
Foley & Lardner
Noori Max
Toshiba Ceramics Co. Ltd.
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