JP2004119673A - Method and device for measuring warpage of semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring method for easily, stably and quantitatively measuring the warpage of a wafer without the need of special skill. <P>SOLUTION: Parallel light L having a prescribed width in the thickness direction of the wafer is projected from one side of the semiconductor wafer W. Parallel light L is received on the other side of the semiconductor wafer W. Thus, the warpage δ of the semiconductor wafer W is calculated by a difference between a light projection width h1 and a light reception width h2. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for measuring the amount of warpage of a semiconductor wafer (hereinafter, simply referred to as a “wafer”) that has warped after backside processing and a measuring apparatus used for the method.
[0002]
[Prior art]
There are mechanical or chemical means such as grinding, polishing, or etching as processing means applied to the back surface of the wafer in order to reduce the thickness of the wafer after the pattern formation processing on the front surface. When performing these processes, it is common to apply a protective tape to the surface of the wafer on which the pattern is formed, and then process the back surface of the wafer.
[0003]
In the grinding means, a process is performed in which the front surface of the wafer to which the protective tape is attached is suction-held by a chuck table and the back surface of the wafer is ground with a grindstone.
[0004]
[Problems to be solved by the invention]
When thin processing is performed on a wafer, the strength and rigidity of the wafer are reduced, and therefore, the wafer is easily affected by the pattern shape of the wafer surface and the mechanical influence from the coating film. As a result, warpage and distortion may occur.
[0005]
Therefore, it is desired to measure the generated warpage and distortion for quality control and the like, and various methods have been tried. However, when comparing measurement values measured by different methods, there is a large variation, and it is difficult to measure quantitatively.
[0006]
For example, a method was proposed in which an optical distance measurement sensor was placed above a horizontally placed wafer, and the distance from the sensor to the wafer surface was measured at each part of the wafer to measure warpage and distortion. It has been implemented.
[0007]
However, the measurement light irradiated due to the warpage or distortion of the wafer surface is irregularly reflected and cannot be captured properly, so that highly accurate measurement cannot be performed.
[0008]
The present invention has been made in view of such circumstances, and a measurement method capable of easily, stably, and quantitatively measuring the amount of warpage of a wafer without requiring special skills. And a measuring device.
[0009]
[Means for Solving the Problems]
The present invention has the following configuration to achieve the above object.
[0010]
That is, the invention according to claim 1 emits parallel light having a predetermined width in the thickness direction of the semiconductor wafer from one side of the semiconductor wafer, and receives the parallel light on the other side of the semiconductor wafer, It is characterized in that the amount of warpage of the semiconductor wafer is obtained based on the amount of received light.
[0011]
(Operation / Effect) The parallel light is blocked according to the amount of warpage of the semiconductor wafer, and the light receiving width is reduced by that amount. At this time, the amount of warpage of the semiconductor wafer can be obtained based on the light receiving width. Therefore, the amount of warpage of the semiconductor wafer can be quantitatively and accurately measured only by projecting parallel light onto the semiconductor wafer from the side.
[0012]
In addition, the measurement can be performed easily without a special technique and in a non-contact state that does not damage the semiconductor wafer. Further, useful data that can be used for quality control, analysis, and the like can be easily obtained.
[0013]
According to another aspect of the present invention, there is provided a measurement table on which a semiconductor wafer is placed, a projector for projecting parallel light having a predetermined vertical width from the side of the semiconductor wafer, and the other side of the semiconductor wafer for projecting the parallel light. And a calculating means for calculating a difference between the light emitting width and the light receiving width.
[0014]
(Function / Effect) A parallel light emitted from the light emitter is received by the light receiver with the semiconductor wafer placed on the measurement table interposed therebetween, and a difference between the light emission width and the light reception width is calculated by the calculating means. The method for measuring the amount of warpage of a semiconductor wafer according to item 1 can be suitably realized.
[0015]
A third aspect of the present invention is the semiconductor wafer warpage amount measuring apparatus according to the second aspect, wherein the measuring table is configured to be pivotable.
[0016]
(Operation / Effect) By rotating the measurement table and performing measurements at different rotational phases, it is possible to measure the magnitude and maximum value of the amount of warpage of the semiconductor wafer, as well as the direction and direction of the warpage. Therefore, it is possible to easily and accurately measure the amount of warpage of a semiconductor wafer at a desired rotation phase, obtain detailed data such as the direction, size, and distribution of the warp, and effectively utilize the data for various analyses. Can be.
[0017]
According to a fourth aspect of the present invention, in the device for measuring the amount of warpage of a semiconductor wafer according to the second aspect, the light emitter and the light receiver are arranged to face each other with the semiconductor wafer interposed therebetween, and the light emitter is arranged around the semiconductor wafer. And the light receiver are integrally rotated and moved.
[0018]
(Function / Effect) The semiconductor wafer mounted on the measurement table is rotated by integrally rotating the light emitter and the light receiver, which are disposed opposite to each other with the semiconductor wafer placed on the measurement table, around the semiconductor wafer. The magnitude and maximum value of the amount of warpage, as well as the direction and direction of the warpage can be measured. In addition, the amount of warpage can be measured while the semiconductor wafer is kept in a stable state without rotating the measurement table, and a more accurate amount of warpage can be measured.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.
[0020]
FIG. 1 is a perspective view showing an entire device for measuring the amount of warpage of a semiconductor wafer (hereinafter, simply referred to as “wafer”) according to the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a front view thereof.
[0021]
This warpage amount measuring apparatus includes a measurement table 2 on which a wafer W is placed on a flat base 1, a projector 3 and a light receiver 4 which are arranged opposite to left and right diagonal positions of the measurement table 2, It is configured by mounting an amplifier unit 5, a power supply unit 6, and the like. The measurement table 2 is pivotally supported by the bearing unit 7 so as to be rotatable around a vertical axis P, and can be freely rotated by hand with a knob 8 protruding from the upper surface of the table.
[0022]
The light projector 3 is configured to horizontally project parallel light (for example, laser light L or the like) having a predetermined vertical width (for example, 30 mm) and a predetermined horizontal width (for example, 2 mm) from the vertical light emitting port 3a. ing.
[0023]
The light receiver 4 is configured to receive the parallel light L from the light projector 3 at a vertically oriented light receiving port 4a. The light receiver 4 only needs to be able to detect the amount of change when the parallel light L from the light projector 3 is received. For example, a change in the light receiving width may be detected in units of pixels using a CCD line sensor, or an electromotive force that changes according to the amount of received light may be detected using a photoconductive cell such as a solar cell. It may be.
[0024]
Amplifier unit 5, as shown in FIG. 3, the light projection width h ₁ and warpage of the maximum value of the wafer W subjected to a difference operation with the light receiving width h ₂ detected by the light receiver 4 from the projector 3 δ is determined.
[0025]
Specifically, first, the wafer W to be measured is placed on the center of the measurement table 2, and the parallel light L emitted from the light projector 3 is sequentially detected by the light receiver 4 while rotating the measurement table 2. At this time, if the wafer W is warped, the light receiving width changes according to the light receiving position during one rotation of the wafer W, as shown in FIG.
[0026]
The amount of change in the light receiving width is sequentially input to the amplifier unit 5 shown in the block diagram of FIG. 5, and the input data is compared to detect a MIN value (minimum value) 5a of the light receiving width. That is, the light receiving width at the position where the amount of warpage of the wafer W is the maximum value is detected.
[0027]
The detected MIN value 5a is input to the subtractor 5c. The subtractor 5c further receives a reference value 5b, which is a preset light projection width from the light projector 3, performs a difference operation between the reference value 5b and the MIN value 5a, and obtains the maximum value δ of the amount of warpage of the wafer W. Is output.
[0028]
As the display of the amount of warpage, for example, a numerical value is displayed on a display device such as a monitor (not shown).
[0029]
When a photoconductive cell is used, an electromotive force corresponding to the amount of received light that changes due to the warpage of the wafer W is obtained in advance by an experiment or the like, and the obtained value is compared with an actually measured value detected by actual measurement to compare the two values. What is necessary is just to output the amount of warpage of the wafer W when the values match. In this case, the minimum value of the electromotive force is the maximum value of the amount of warpage of the wafer W.
[0030]
As described above, the parallel light emitted from the light emitter 3 disposed with the wafer W interposed therebetween is detected by the light receiver 4, and the difference between the reference value of the light emission width and the light reception width is calculated by the amplifier unit 5. In the contact state, the amount of warpage of the wafer W can be quantitatively and accurately measured.
[0031]
The present invention is not limited to the above embodiment, but can be modified as follows.
(1) In the above embodiment, the amount of warpage of the wafer W was measured without considering the thickness of the protective tape attached to the wafer W. The amount of warpage may be measured.
[0032]
For example, by measuring and inputting the thickness of the wafer W and the thickness of the protective tape in advance, the amount of warpage of the wafer W can be accurately calculated.
[0033]
(2) In the above embodiment, the measurement table 2 was turned by hand. However, the measurement table 2 was rotated at a constant speed by a rotation driving means such as a motor, and light was emitted at predetermined rotation phases to obtain a large number. You may comprise so that data may be acquired automatically. In this case, the rotational phase of the measurement table 2 is detected by a rotary encoder or the like, and the measured rotational phase is taken in as measurement data, so that not only the magnitude of the warp of the wafer W but also the direction and direction of the warp are measured. can do.
[0034]
In addition, instead of the measurement table 2, the projector 3 and the light receiver 4 may be configured to rotate integrally around the measurement table 2 in a state where they are opposed to each other.
[0035]
(3) In the above embodiment, only the maximum value δ of the amount of warpage of the wafer W is calculated and output, but the measurement data obtained by rotating the measurement table 2 by a predetermined angle is used. The information may be input to a desired information processing device, stored and stored, and output and displayed on a display device such as a monitor as needed.
[0036]
【The invention's effect】
As is apparent from the above description, according to the present invention, the amount of warpage of the semiconductor wafer can be quantitatively and accurately measured only by projecting parallel light from the side to the semiconductor wafer. The measurement can be easily performed without requiring any special technique and in a non-contact state that does not damage the semiconductor wafer. Further, it is possible to easily obtain the amount of warpage as useful data that can be used for quality control, analysis, and the like.
[Brief description of the drawings]
FIG. 1 is a perspective view of a warpage amount measuring device.
FIG. 2 is a plan view of the warpage amount measuring device.
FIG. 3 is a front view showing the concept of a warpage amount measurement mode.
FIG. 4 is a diagram showing the amount of warpage of a wafer.
FIG. 5 is a block diagram showing a configuration of an amplifier unit.
[Explanation of symbols]
2 ... measurement table 3 ... projector 4 ... photoreceiver W ... semiconductor wafer L ... parallel light _{h 1} ... projection width _{h 2} ... light-receiving width [delta] ... warpage (maximum value)

Claims (4)

A parallel light beam having a predetermined width is projected from one side of the semiconductor wafer in the thickness direction of the semiconductor wafer, and the parallel light beam is received by the other side of the semiconductor wafer. A method for measuring the amount of warpage of a semiconductor wafer, characterized in that: A measurement table on which a semiconductor wafer is placed;
A projector that projects parallel light having a predetermined vertical width from the side of the semiconductor wafer,
A light receiver for receiving the parallel light on the other side of the semiconductor wafer,
A device for measuring the amount of warpage of a semiconductor wafer, comprising: a calculating means for calculating a difference between a light emitting width and a light receiving width. An apparatus for measuring the amount of warpage of a semiconductor wafer according to claim 2,
An apparatus for measuring the amount of warpage of a semiconductor wafer, wherein the measurement table is configured to be pivotable. An apparatus for measuring the amount of warpage of a semiconductor wafer according to claim 2,
A semiconductor wafer warpage measuring device, wherein the light emitter and the light receiver are arranged opposite to each other with a semiconductor wafer interposed therebetween, and the light emitter and the light receiver are integrally rotated around the semiconductor wafer. .

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