JP3950622B2 - Reference wafer for nanotopography evaluation and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a wafer for use as a reference for measuring the micro unevenness (Nanotopogrphy) on the surface of the silicon wafer that occurs during the manufacture of the silicon wafer, and the surface has a certain spatial wavelength and height (wave height). The present invention relates to a nanotopography evaluation reference wafer having minute irregularities, and further relates to a manufacturing method thereof.
[0002]
[Prior art]
Minute unevenness (Nanotopogrphy) of several hundred nm or less generated during the planarization process of the silicon wafer is a problem in the CMP process of the device process. For this reason, measurement of minute irregularities on the surface of the silicon wafer is performed in the wafer manufacturing process.
[0003]
Magic mirror (measurement device that measures the parallel brightness of a halogen lamp to a silicon wafer and measures the brightness of the reflected light) or SQM (ADE) An argon ion laser is incident on the workpiece obliquely and specular reflection light is detected by a detector.At this time, the inclination of the workpiece surface is obtained from the deviation from the regular reflection position, and the height of the minute irregularities is measured). in use.
[0004]
In the measurement by these measuring apparatuses, an arbitrary silicon wafer that has been subjected to planarization processing is used as a target management wafer, and variations among days, batches, and specific apparatuses are only managed.
[0005]
However, such management only manages the relative variation between the above-mentioned days, batches, and devices based on a single silicon wafer that happens to be selected. High reliability has not been obtained. For this reason, it has become necessary to supply a silicon wafer having fine irregularities as a reference, thereby calibrating the absolute value of the measured value. Although there exists a standard wafer having a certain level difference, since the wafer does not have a constant spatial wavelength and height (wave height) on the surface, it is not possible to calibrate periodicity and inclination.
[0006]
By the way, in recent years, in the planarization of a silicon wafer, a local etching apparatus for locally etching a silicon wafer by active species generated in plasma has been used. FIG. 1 is a sectional view showing a general local etching apparatus 200.
[0007]
This local etching apparatus 200 discharges SF6 (sulfur hexafluoride) gas or the like with the plasma generator 100 to generate F active species and the like, and this F active species gas G is transferred from the nozzle portion 101 to silicon on the chuck 120. By spraying on the surface Wa of the wafer W, a portion thicker than the reference thickness value (hereinafter referred to as “relative thickness portion”) in the surface Wa portion is locally etched.
[0008]
Specifically, the moving speed of the chuck 120, that is, the relative speed of the nozzle portion 101 is decreased with respect to the thick relative thick portion, and the injection time of the F activated species gas G is lengthened. Is to flatten the entire surface Wa of the silicon wafer W by increasing the relative speed of the nozzle portion 101 and shortening the spray time of the F activated species gas G.
[0009]
[Problems to be solved by the invention]
In view of the above-mentioned problems, the present invention is a silicon wafer that serves as a reference when measuring minute irregularities on the surface, and has a predetermined constant spatial wavelength and height formed on the surface by relative scanning of local etching. It is an object of the present invention to provide a nanotopography evaluation reference wafer having minute irregularities and to provide a manufacturing method for manufacturing this evaluation reference wafer. Another object of the present invention is to use the evaluation reference wafer to calibrate the measuring instrument so that the evaluation of the measurement result is equivalent in any measuring instrument and can be managed by this. . Furthermore, it is an object of the present invention to provide a reference wafer for evaluation based on a certain standard for a micro unevenness measuring device on the surface of a silicon wafer that does not have a calibration means at present.
[0010]
[Means for Solving the Problems]
In the present invention, the etching shape is superimposed by moving local etching at a constant speed and at a constant width, and minute etching traces are formed on the wafer surface with a constant period and a constant height. Further, at that time, the etching traces are formed such that the period thereof coincides with the interval of the linear scanning, and the height depends on the speed. In this specification, the term wave height is used, which means that the minute irregularities with periodicity are compared to waves on the water surface, and in such waves, the difference in height from the bottom of the wave to the top of the wave is meant. It is used as something to do.
[0011]
[0012]
More specifically, the above problem is solved by the following means. That is,
The solution of the first invention is that the spatial wavelength is 0.5 mm or more and 20 mm or less by the relative scanning of the local etching in which the shape formed by etching in the Y direction is repeated at constant intervals in the X direction , and the wave height is A reference wafer for nanotopography evaluation, characterized in that fine irregularities of 1 nm to 200 nm are formed .
[0013]
[0014]
[0015]
Solutions of the second invention, a silicon wafer having undergone at least double-side polishing step, using the X-Y stage, X, either direction Y is allowed to step movement of constant width, the other direction By moving the region of local etching by moving linearly, by changing the step width of the XY stage, depending on the spatial wavelength of minute irregularities, and changing the speed of the linear movement By making the wave height of the micro unevenness dependent , the micro unevenness for nanotopography evaluation where the spatial wavelength is 0.5 mm or more and 20 mm or less and the wave height is 1 nm or more and 200 nm or less on the silicon wafer. production side of Nanotopogurafu I evaluation criteria wafer, and forming by the relative scan of the local etching It is.
[0016]
[0017]
[0018]
[0019]
In these inventions, a predetermined gas in the discharge tube is ejected from the nozzle portion during the plasma generation process, and the nozzle portion of the discharge tube is moved at a constant speed along the surface of the wafer. As a result, the surface of the silicon wafer is locally etched by the activated species gas sprayed from the nozzle portion, thereby processing and forming minute irregularities having a certain period and wave height on the silicon wafer.
[0020]
By moving the local etching at a constant speed and a constant width, minute etching marks, that is, minute irregularities are formed on the wafer surface with a constant period and wave height. At this time, the period of the minute unevenness coincides with the interval of the linear scanning, and the wave height depends on the speed. Produce a nanotopography evaluation reference wafer with minute irregularities having a spatial wavelength (period) of 0.5 mm or more and 20 mm or less, and a wave height of 1 nm or more and 200 nm or less, and apply this to an optical measuring device for wafer surface measurement and calibration. Check the measured values.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0022]
FIG. 2 is a schematic configuration diagram showing a manufacturing apparatus for manufacturing a nanotopography evaluation reference wafer according to an embodiment of the present invention, that is, a local etching apparatus. As a result, minute irregularities are formed on the wafer surface by local etching.
[0023]
The local etching apparatus includes a plasma generator 1, a gas supply device 3, and an XY drive mechanism 5. The plasma generator 1 is an apparatus for generating an activated species gas G containing neutral radicals by plasma discharge of gas in an alumina discharge tube, and includes a microwave oscillator 10 and a waveguide 11. The microwave oscillator 10 is a magnetron and can oscillate a microwave M having a predetermined frequency.
[0024]
The waveguide 11 is for propagating the microwave M oscillated from the microwave oscillator 10 and is extrapolated to the alumina discharge tube 2.
[0025]
A reflection plate (short plunger) 12 that reflects the microwave M to form a standing wave is attached inside the left end of the waveguide 11. Further, in the middle of the waveguide 11, a stub tuner 13 that performs phase matching of the microwave M and an isolator 14 that bends the reflected microwave M toward the microwave oscillator 10 in the 90 ° direction (surface direction in FIG. 2). And are attached.
[0026]
The alumina discharge tube 2 is a cylindrical body having a nozzle portion 20 at a lower end portion, and a supply pipe 30 of the gas supply device 3 is connected to the upper end portion.
[0027]
The gas supply device 3 is a device for supplying gas into the alumina discharge tube 2, and has an SF 6 (sulfur hexafluoride) gas cylinder 31, which is connected via a valve 32 and a flow rate controller 33. It is connected to the supply pipe 30.
[0028]
By adopting such a configuration, the plasma generator 1 supplies gas to the alumina discharge tube 2 from the gas supply device 3 and oscillates the microwave M from the microwave oscillator 10 to cause plasma discharge in the alumina discharge tube 2. The activated species gas G generated by the plasma discharge is injected from the nozzle unit 20.
[0029]
When the silicon wafer W is disposed on the chuck 40 in the chamber 4, the silicon wafer W is attracted by the electrostatic force of the chuck 40. A vacuum pump 41 is attached to the chamber 4, and the inside of the chamber 4 can be evacuated by the vacuum pump 41. Further, a hole 42 is formed in the center of the upper surface of the chamber 4, and the nozzle portion 20 of the alumina discharge tube 2 is externally inserted into the chamber 4 through the hole 42. An O-ring 43 is mounted between the hole 42 and the alumina discharge tube 2 so that the space between the hole 42 and the alumina discharge tube 2 is kept airtight. A duct 44 is provided around the nozzle portion 20 inserted into the hole 42, and the reaction product gas at the time of etching can be discharged to the outside of the chamber 4 by driving the vacuum pump 45.
[0030]
The XY drive mechanism 5 is disposed in such a chamber 4 and is supported from below the chuck 40.
[0031]
The XY drive mechanism 5 moves the chuck 40 in the left-right direction of FIG. 2 by the X drive motor 50, and the chuck 40 and the X drive motor 50 are integrated with each other by the Y drive motor 51 in the front and back direction of FIG. Move to. That is, the nozzle unit 20 can be moved relative to the silicon wafer W in the XY direction by the XY drive mechanism 5.
[0032]
Next, a method of forming the wafer surface micro unevenness according to this embodiment using the local etching apparatus will be described. The valve 32 of the gas supply device 3 is opened, and the SF6 gas in the cylinder 31 flows out to the supply pipe 30 and is supplied to the alumina discharge tube 2. At this time, the opening degree of the valve 32 is adjusted, and the flow rate of the SF6 gas is adjusted to 300 SCCM (Standard Cubic CentiMeter).
[0033]
In parallel with the SF6 gas supply operation, the microwave oscillator 10 is driven. Then, the SF6 gas is plasma-discharged by the microwave M, and an active species gas G containing F (fluorine) radicals (neutral active species) that are neutral radicals is generated. As a result, the activated species gas G is guided to the nozzle portion 20 of the alumina discharge tube 2 and is sprayed from the opening 20a of the nozzle portion 20 toward the silicon wafer W side.
[0034]
In this state, a local etching process is performed. The XY drive mechanism 5 is driven by the control computer 49, and the chuck 40 that has attracted the silicon wafer W is moved in a zigzag manner in the XY direction. FIG. 3 is an explanatory diagram for explaining a scanning state of the nozzle unit 20 by a locus viewed from the upper surface of the silicon wafer W. As shown in FIG. 3, the nozzle portion 20 is moved in a zigzag shape (rectangular wave shape) relative to the silicon wafer W.
[0035]
At this time, the speed of the nozzle unit 20 is repeatedly moved in the Y direction at a constant speed in the opposite direction, and is stepped in the X direction at regular intervals S in accordance with the reversal of the repetition. As a result, the surface of the silicon wafer W is etched in accordance with a constant scanning speed in the Y direction at every interval S in the X direction. In the above-described local etching, an example in which SF6 gas is used is shown, but NF3 or CF4 gas can be used.
[0036]
FIG. 4 is a diagram showing the state of etching as viewed from the Y direction. In this figure, the horizontal direction indicates the X-axis direction, and the vertical direction indicates the Z direction. (A) is formed on the silicon wafer when the shapes formed by etching in the Y direction are overlapped at equal intervals in the X direction. (B) is a partially enlarged view of this shape.
[0037]
When the nozzle unit 20 scans the surface of the silicon wafer W in the Y direction at a constant speed, the shape indicated by the thick curve e in (a) is formed by one scan. Since this shape is repeated at regular intervals S in the X direction, a shape in which these shapes are finally overlapped is formed on the silicon wafer W. As shown in the enlarged view (b), the overlapped shape hits a minute wave, and the pitch is equal to the feed interval S in the X direction. In other words, the region where the etching overlaps continuously generates minute irregularities on the surface of the silicon wafer W after the etching.
[0038]
At this time, when the period of the micro unevenness is 20 mm or less and the wave height (the difference in height from the wave top to the wave bottom) is in the range of 1 nm to 200 nm, Y is calculated from the maximum etching amount of single etching scan. Determine the speed of the direction.
[0039]
In addition, this invention is not limited to the said embodiment, A various deformation | transformation and change are possible within the range of the summary of invention. For example, although downstream plasma is used in the above embodiment, RIE can also be used. In this case as well, although there is a difference in the plasma generation method, it is possible to manufacture a silicon wafer having a constant wave height and period by processing the etching shape at every calculated interval using XY driving.
[0040]
When a silicon wafer manufactured according to the above embodiment and having a constant period and a set value wave height is used as a wafer for confirming a measurement value of the measuring device or for calibrating the measuring device, the measuring device has a stable reliability. Can be obtained. Examples are shown below.
[0041]
【Example】
Example 1
In a local etching apparatus using downstream plasma, the pitch width is set to 2 mm, 4 mm, and 5 mm with SF6 gas, gas flow rate 300 SCCM, microwave traveling wave, and output 300 W, and the velocity in the Y direction is constant (80 mm / sec, 40 mm / sec, 80 mm / sec), and the silicon wafer was etched. The processing amount was measured by a silicon wafer flatness measuring device before and after processing. In addition, after processing, the height (wave height) of the unevenness on the processed silicon wafer was evaluated by a stylus type step measuring device. FIG. 5 is a table showing the processing results obtained thereby.
[0042]
Example 2
As a conventional method, the micro unevenness of the product wafer was evaluated by a nanotopography evaluation apparatus that was not calibrated by the reference wafer and a nanotopography evaluation apparatus that was calibrated by the reference wafer obtained by the present invention. The result is shown in FIG. The height (wave height) ha of the unevenness a of the nanotopography evaluation apparatus calibrated by the reference wafer according to the present invention is substantially the same as the reference value (absolute value) b by the stylus type step measuring apparatus, whereas On the other hand, it can be seen that there is an error in the height (wave height) of the irregularities in the height (wave height) hc of the irregularities c obtained by the conventional method.
[0043]
【The invention's effect】
Until now, it has been impossible to control the minute uneven nanotopology remaining on the silicon wafer. However, according to the method of the present invention using the local etching method, it is possible to control the minute unevenness remaining on the processed silicon wafer by the pitch width and scanning speed of the XY stage. For this reason, it is possible to supply a wafer with a certain standard as a standard sample to a micro unevenness measuring device on the surface of a silicon wafer that does not have a calibration means at present, and the effect of improving the reliability of the absolute value Play.
[0044]
According to the present invention, there is provided a silicon wafer serving as a reference when measuring minute unevenness on a surface, and a nanotopography evaluation reference wafer having minute unevenness having a predetermined spatial wavelength and wave height on the surface. There is an effect that can be. Further, by using this evaluation reference wafer for calibration of the measuring instrument, it is possible to make the evaluation of the measurement result equivalent in any measuring instrument, and further, it is possible to manage by this. In addition, there is an effect that a wafer having a certain standard can be supplied to a micro unevenness measuring apparatus on the surface of a silicon wafer which does not have a calibration means at present.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a general local etching apparatus 200. FIG.
FIG. 2 is a schematic configuration diagram showing a manufacturing apparatus for manufacturing a nanotopography evaluation reference wafer according to an embodiment of the present invention, that is, a local etching apparatus.
FIG. 3 is an explanatory diagram for explaining a scanning state of the nozzle unit 20 by a locus viewed from the upper surface of the silicon wafer W;
FIG. 4 is a view showing a state of etching viewed from the Y direction.
FIG. 5 is a table showing the processing results of Examples.
FIG. 6 is a diagram showing the result of evaluating the micro unevenness of a product wafer according to the prior art and the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,100 Plasma generator 2 Alumina discharge tube 3 Gas supply apparatus 4 Chamber 5 XY drive mechanism 10 Microwave oscillator 11 Waveguide 13 Stub tuner 14 Isolator 20, 101 Nozzle part 20a Opening 30 Supply pipe 31 Cylinder 32 Valve 33 Flow controller 40, 120 Chuck 41, 45 Vacuum pump 42 Hole 43 O-ring 44 Duct 49 Control computer 50 X drive motor 51 Y drive motor G Active species gas M Microwave W Silicon wafer Wa Surface

Claims (2)

By the relative scanning of local etching in which the shape formed by etching in the Y direction is repeated at regular intervals in the X direction, the surface has minute irregularities with a spatial wavelength of 0.5 mm to 20 mm and a wave height of 1 nm to 200 nm. A reference wafer for nanotopography evaluation characterized by being formed . A silicon wafer that has undergone at least a double-side polishing process is used for an area of local etching by using a XY stage, moving in a step with a constant width in either X or Y direction, and moving in a straight line in the other direction. At this time,
By changing the step width of the XY stage, the spatial wavelength of the minute irregularities is made dependent,
By changing the speed of the linear movement, by making the wave height of the micro unevenness dependent ,
On the silicon wafer, a minute unevenness for nanotopography evaluation having a spatial wavelength of 0.5 mm to 20 mm and a wave height of 1 nm to 200 nm is formed by relative scanning of local etching. A method of manufacturing a reference wafer for nanotopography evaluation.

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