JP4400331B2 - Wafer shape evaluation method and management method - Google Patents

Description

  The present invention relates to a shape evaluation method for evaluating the shape of a wafer represented by a silicon wafer.

  Conventionally, a silicon wafer used as a semiconductor substrate is generally grown by growing a cylindrical semiconductor single crystal ingot by a Czochralski (CZ) method or a floating zone (FZ) method. After a semiconductor single crystal ingot is cut into a thin plate (slicing) to produce a wafer, the resulting wafer is chamfered to chamfer the outer periphery of the wafer in order to prevent cracking and chipping of the wafer, A lapping process for adjusting the flatness, an etching process for etching the wafer to remove processing distortion of the wafer, a polishing process for further improving the surface roughness and flatness of the etched wafer to make a mirror surface, and a wafer A cleaning process to remove abrasives and foreign substances adhering to the It is produced. This semiconductor wafer manufacturing process shows the main processes, and other processes such as a heat treatment process can be added or the order of the processes can be changed.

  In recent years, semiconductor devices have been highly integrated due to dramatic advances in semiconductor device technology, and quality requirements for semiconductor wafers serving as semiconductor device substrates have become more stringent. For example, in the manufacture of a semiconductor device, the process of forming a resist pattern using KrF excimer laser light (wavelength = 0.248 μm), which is ultraviolet light, as a light source on the semiconductor wafer manufactured as described above is usually 20 times to Taking a DRAM (dynamic random access memory) as an example, a 256 Mbit DRAM currently mass-produced has a resist pattern of 0.13 μm. As device patterns are further miniaturized in accordance with the recent higher integration and higher performance of semiconductor integrated circuits, further improvements in resist pattern dimensional accuracy and overlay accuracy are desired. Quality requirements for semiconductor wafers on which semiconductors are formed are becoming more stringent.

  For example, as the device pattern becomes finer as described above, even if there is a very small undulation in the semiconductor wafer, an error occurs in the device pattern in the photolithography process, and the yield of the semiconductor device is increased. The problem of incurring a drop occurred. On the other hand, in order to reduce the manufacturing cost due to the effective use of semiconductor wafers, a flat semiconductor wafer is manufactured to the vicinity of the outermost periphery of the wafer main surface (below the chamfered portion) so that devices can be formed over a wide area on the wafer. Is desired.

  One of important characteristics required for a semiconductor wafer to be a substrate for such a semiconductor device is the shape quality of the semiconductor wafer. As the shape quality of semiconductor wafers, in general, diameter, thickness, parallelism, flatness, warpage, relatively long-period irregularities called bows, warps, etc., waviness that is irregularities with a period of several mm, surface roughness, etc. There are various parameters. Recently, among the parameters relating to the shape quality, there are many cases in which quality called global flatness based on the back surface or front surface or site flatness is regarded as important as an index of flatness.

  In particular, as an index of flatness, the global flatness of the back surface reference is called GBIR (Global Back Ideal Range), which has one reference surface in the wafer surface, and the maximum and minimum position displacement widths relative to this reference surface. It is usually defined and corresponds to TTV (total thickness deviation), which is a conventional customary specification.

  The back-side reference site flatness is called SBIR (Site Back Ideal Range) and corresponds to LTV that has been used quite frequently in the past. This SBIR is the sum of the absolute values of the maximum displacement amounts on the + side and − side from the focal plane in the site when the back surface of the wafer is the reference plane and the plane including the center point of the site is the focal plane at each site. Is evaluated for each site. Usually, an 8-inch wafer (diameter 200 mm) or the like is evaluated in an area where the site size is about 20 mm × 20 mm. However, the size of this site can be changed according to the diameter or specification of the wafer.

  In addition, the surface-based site flatness is called SFQR (Site Front Last Squares Range), and the in-site plane calculated by the least square method is used as the reference plane within the set site. Each site is evaluated by the sum of absolute values of the maximum displacement amounts on the + side and − side.

  Further, in Patent Document 1, the surface shape quality of the semiconductor wafer is determined by measuring the vertical displacement of the semiconductor wafer, performing differential twice, and calculating the standard deviation of the obtained double differential value as smoothness. A method for evaluation is disclosed. By utilizing such an evaluation method, the shape quality of the semiconductor wafer can be evaluated in more detail.

  However, when evaluating the shape quality of a semiconductor wafer using the index as shown above, if the design rule in the device manufacturing process is up to 0.18 μm, the shape quality is sufficient by satisfying the standard. Although it was possible to make a semiconductor wafer, with the recent high integration of semiconductor devices, as the design rules become stricter, such as 0.13 μm and 0.09 μm, it is a semiconductor wafer that satisfies the above indices. Even when the device is actually formed, there may be a problem such as a decrease in yield.

  For example, many processing apparatuses such as an exposure machine are used in the device manufacturing process. However, a defocus defect may occur when a wafer for forming a device is held in each processing apparatus and processed. If such a defocus failure occurs in the device manufacturing process, the device cannot be formed with high accuracy, and this has been considered as one of the causes of decreasing the yield. Accordingly, in the device manufacturing process, compatibility and matching between the wafer holding chuck installed in each processing apparatus such as an exposure machine and the shape of the wafer are important.

  In recent years, a chuck having a very high flatness has been developed as a chuck installed in each processing apparatus. For this reason, when attracting a wafer using a high flatness chuck, in order to prevent the occurrence of the above-described defocus failure, the thickness variation of the wafer is made uniform or the flatness is improved. It is requested to do.

  However, for example, even if the semiconductor wafer has a uniform thickness variation, it is excellent in thickness uniformity and flatness when evaluated with the above-described index such as SFQR. However, when it is actually attracted to a chuck having a high flatness such as an exposure machine, a defocus failure may occur in the peripheral portion of the wafer and the yield may be reduced in the device manufacturing process. In addition, in order to investigate the cause of defocus failure despite the excellent thickness uniformity of the wafer, even if the wafer shape is evaluated by various conventional evaluation methods, The cause could not be detected or identified.

  For this reason, the wafer shape is evaluated by using parameters other than the above-described index such as SFQR, and a wafer that does not cause a problem such as a defocus failure even with specifications based on strict design rules can be accurately determined. It has been desired to establish an evaluation method that can identify the cause when a focus failure occurs.

JP-A-11-287630

  Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to quantitatively obtain effective information about the shape quality of a wafer that could not be confirmed conventionally from a viewpoint different from that of SFQR and the like. Accordingly, it is an object of the present invention to provide a wafer shape evaluation method capable of accurately evaluating a wafer shape based on a certain standard.

In order to achieve the above object, according to the present invention, there is provided a method for evaluating the shape of a wafer, wherein the surface shape of the wafer is measured by scanning the surface and / or the back surface of the wafer along the wafer radial direction. Calculating a reference line from a predetermined region of the measured surface shape data, and obtaining a local slope representing a difference in the thickness direction between the calculated reference line and the surface shape data, and / or or shape evaluation method of wafer and evaluating the back surface shape Ru are provided.

  Thus, the surface shape of the front and / or back surface of the wafer is measured along the wafer radial direction, a reference line is calculated from the measured surface shape data, and the difference in the thickness direction between the reference line and the surface shape data is calculated. By obtaining the local slope that represents the wafer shape and evaluating the wafer shape, quantitative information on the shape quality of the wafer is obtained quantitatively from a different point of view from the conventional SFQR index, etc. Can be evaluated accurately. Therefore, according to the present invention, for example, it is possible to accurately determine a wafer in which a problem such as a defocus failure as described above occurs, or to accurately specify the cause of a defocus failure or the like. Furthermore, since the shape of the front surface and the back surface of the wafer can be evaluated separately, the wafer shape can be evaluated more accurately.

At this time, the shape evaluation of the wafer, said it is rather preferable to perform the outer peripheral portion of the wafer, in particular the shape evaluation of the wafer, preferably be performed outside the region from the position of 10mm from the outer peripheral edge of the wafer Yes.
Defocusing failure or the like that occurs when the wafer is held on a high flatness chuck mainly occurs at the outer peripheral portion of the wafer, so it is important to evaluate the shape of the outer peripheral portion of the wafer. Therefore, if the wafer shape evaluation is performed in the outer periphery of the wafer, particularly in the region outside the position of 10 mm from the outer peripheral edge of the wafer, the wafer shape can be accurately and efficiently evaluated. For example, it is possible to determine a wafer in which a defocus failure occurs and to identify the cause thereof with extremely high accuracy.

Also, measurement of the surface shape of the wafer, the wafer is not preferable be carried out in a non-adsorbed state.
In the present invention, the wafer surface shape can be measured in a non-adsorbed state of the wafer, whereby the displacement of the wafer shape can be confirmed from the local slope determined on the wafer front surface and / or back surface, It is possible to accurately evaluate the shape of a wafer that causes a problem in the device manufacturing process.

Moreover, the measurement of the surface shape of the wafer, it is not preferable that the surface and / or back surface of the wafer carried out by scanning below 1mm intervals.
Since the finer the interval of scanning the front and / or back of the wafer, the better the accuracy of the evaluation can be made. By scanning the front and / or back of the wafer at intervals of 1 mm or less in this way, The wafer shape can be evaluated with sufficiently good measurement accuracy.

In the present invention, the calculation of the reference line, the least squares method, simple average, Ru can be accomplished using any of the methods of the moving average.
Thus, the reference line can be easily calculated from a predetermined area of the surface shape data by using any one of the method of least squares, simple average, and moving average, and the reference line calculated in this way If the local slope is obtained using, the shape of the wafer can be evaluated with high accuracy.

Furthermore, the area of the surface shape data to calculate the said reference line, it is not preferable that the area within the range of 10mm~5mm outer peripheral edge of the wafer.
Thus, by setting the area of the surface shape data for calculating the reference line to an area within the range of 10 mm to 5 mm from the outer peripheral edge of the wafer, the outer area of the wafer, particularly the area outside the position 10 mm from the outer peripheral edge of the wafer. The local slope can be obtained with high accuracy. Further, if the reference line is calculated in such a region, for example, when the wafer is attracted to the chuck, the local slope can be obtained on the assumption that the influence of the component whose wafer shape is corrected by the adsorption is removed. Therefore, it becomes possible to perform more accurate shape evaluation.

Further, according to the shape evaluation method of the wafer of the present invention, after measuring the surface shape of the wafer, it is rather preferable to perform the removal of the long wavelength components and / or measurement noise on the surface shape data the measurement, the when the removal of the long wavelength component, Ki de be done by applying the method of least squares approximation or high-pass filter, also the removal of the measurement noise, Ru can be performed by applying a moving average or low pass filter.

  Thus, in the present invention, by removing the long wavelength component and / or measurement noise after measuring the surface shape of the wafer, for example, even if a long period of undulation is present in the wafer to be evaluated, The wafer shape can be accurately evaluated. At this time, the removal of the long wavelength component can be easily performed by applying a least square method approximation or a high-pass filter, and the measurement noise can be easily removed by applying a moving average or a low-pass filter.

In this case, it is not preferable to carry out over the shape evaluation of the wafer wafer the entire circumference.
By performing wafer shape evaluation over the entire circumference of the wafer in this way, the shape of the entire circumference of the wafer can be accurately evaluated based on a certain standard, and the shape of the wafer can be grasped in more detail. .

Further, when measuring the surface shape of the wafer, the surface and / or the back surface of the wafer is scanned in a non-contact manner using a displacement meter equipped with a laser oscillator and an automatic focusing mechanism, or a capacitive displacement meter. by, it is not preferable to perform the measurement of the wafer surface shape.
In the present invention, when measuring the surface shape of the wafer, the surface shape of the wafer is measured by using the displacement meter having the laser oscillator and the automatic focusing mechanism or the capacitance type displacement meter. The surface shape of the front surface and / or back surface of the wafer can be measured with very high accuracy and speed. Furthermore, since the wafer surface shape can be measured without bringing the displacement meter into contact with the wafer, the wafer surface shape can be easily and stably measured without causing scratches or contamination on the wafer to be evaluated. .

According to the present invention, there is provided a management method for performing quality control of a wafer and / or process management of a process for manufacturing a wafer based on the wafer shape evaluation result obtained by the wafer shape evaluation method of the present invention. Ru can be provided.
As described above, based on the evaluation result obtained by the wafer shape evaluation method of the present invention, for example, a wafer satisfying a predetermined standard is selected, or a local etching process such as plasma etching is performed so that the wafer has a desired shape. If the quality of the wafer is controlled by performing typical processing, the yield in the next process such as the device manufacturing process can be improved. Accumulation of the results of the shape evaluation method of the present invention makes it possible to grasp the capability of the wafer manufacturing process and to easily find abnormalities in the manufacturing process. Thus, the wafer can be manufactured very stably.

  As described above, according to the present invention, effective information on the shape quality of a wafer is quantitatively obtained from a viewpoint different from the conventionally used index such as SFQR, and the wafer shape is accurately determined on a certain standard. Can be evaluated. Therefore, for example, it is possible to accurately determine a wafer in which a problem such as a defocus failure occurs, or to accurately specify the cause of the defocus failure or the like. Further, by performing wafer quality control and wafer manufacturing process management based on the wafer shape evaluation results obtained by the shape evaluation method of the present invention, the yield can be improved in subsequent processes, or wafer manufacturing can be performed. Can be performed very stably.

Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to these.
As a result of repeated investigations on the cause of defocus failure that occurs when a wafer having excellent thickness uniformity and flatness is attracted to a chuck for holding a high flatness wafer, It has been discovered that the cause of this is the warp component of a wafer having a shorter spatial wavelength than the bow and warp present in the periphery of the wafer. In the present invention, a warp component of a wafer having a spatial wavelength shorter than that of bow or warp is defined as a local slope.

  Normally, if the wafer thickness is uniform, the wafer shape is corrected when the back surface of the wafer is attracted to a high flatness chuck, so that the occurrence of a defocusing defect can be suppressed. However, for example, if there is a local slope in the periphery of the wafer, the wafer periphery cannot be adsorbed to the chuck even if the wafer thickness is uniform, so that the wafer shape cannot be corrected. It became clear that a defocus failure occurred.

  However, since the local slope existing in the peripheral portion of the wafer cannot be quantitatively evaluated by the conventional indexes such as GBIR and SBIR for evaluating the flatness of the wafer, the wafer having a defocus defect or the like is generated. In order to identify and identify the cause, it is necessary to develop a new shape evaluation method that can quantitatively determine the position and size of the local slope existing on the wafer.

  Therefore, as a result of intensive studies and studies on the wafer shape evaluation method capable of quantitatively grasping such a local slope, the present inventors have found that the surface and / or the back surface of the wafer is aligned along the wafer radial direction. If the surface shape of the wafer is measured by scanning and a reference line is calculated from a predetermined area of the measured surface shape data, the local slope existing on the wafer is determined in the thickness direction difference between the reference line and the surface shape data. As a result, it was found that the wafer shape can be accurately evaluated based on a certain standard, thereby completing the present invention.

Hereinafter, the wafer shape evaluation method of the present invention will be described.
First, a shape evaluation apparatus for performing the wafer shape evaluation method of the present invention will be described with reference to the drawings, but the present invention is not limited to this. FIG. 5 is a schematic explanatory view showing the main configuration of an example of a wafer shape evaluation apparatus, and FIG. 7 is a schematic explanatory view showing another example of a wafer shape evaluation apparatus.

  As the shape evaluation apparatus used in the wafer shape evaluation method of the present invention, for example, the shape evaluation apparatus 11 shown in FIG. 5 can be used. The shape evaluation device 11 is a device that can measure the surface shape of the wafer 6 and calculate a reference line from a predetermined region of the measured surface shape data to obtain a local slope. For example, the surface shape of the wafer 6 A surface shape measuring means 1 for measuring the measured surface shape data, a storage means 2 for storing the measured surface shape data, and an arithmetic processing means 3 for calculating a reference line and a local slope using the stored surface shape data. It is what you have.

  In this shape evaluation apparatus 11, the surface shape measuring means 1 may be any device as long as it can accurately measure the surface shape of the wafer 6. For example, as shown in FIG. A wafer 6 can be mounted on the surface 7 in a non-adsorptive manner, and a displacement meter 8 can be used to measure the displacement (surface shape) in the vertical direction of the front or back surface of the wafer. By using such a surface shape measuring means 1, for example, as shown in FIG. 6, the displacement gauge 8 is scanned along the radial direction of the front surface or the back surface of the wafer 6, so that the surface shape of the front surface or the back surface of the wafer is obtained. Data can be obtained with high accuracy.

  Further, as another form of the surface shape measuring means, a part of the wafer 6 is held by the wafer support 9 as in the shape evaluation apparatus 12 shown in FIG. The surface shape measuring means 4 for measuring the surface shapes of the front and back surfaces of the wafer by the displacement meter 10 can be used. By using such a surface shape measuring means 4, for example, as shown in FIG. 8, two displacement gauges 10 on the front and back sides are scanned along the radial direction of the front and back surfaces of the wafer 6, respectively. The surface shape data of the back surface can be obtained with high accuracy. In such a surface shape measuring means 4, the wafer support 9 can hold the wafer at a position that does not interfere with the measurement of the surface shape, for example, by holding a part of the wafer main surface or the outer periphery of the wafer. In addition, the surface shape of the wafer can be measured with the wafer in a non-adsorbed state.

  At this time, the displacement meter 8 or the displacement meter 10 is provided with, for example, a laser oscillator, an automatic focusing mechanism including a CCD (Charge Coupled Device) camera, an automatic focusing circuit, etc., and the surface shape of the wafer in a non-contact state with the wafer. It is preferable to use one capable of measuring If it is a displacement meter equipped with such a laser oscillator and an automatic focusing mechanism, for example, a laser beam (for example, a HeNe laser) is irradiated at a predetermined interval perpendicularly to the front surface and / or back surface of the wafer 6, The deviation of the distance from the pre-calibrated reference point can be measured by automatically focusing the reflected image of the laser beam irradiated from the wafer by the automatic focusing mechanism, so that the front and / or back surface of the wafer can be measured. The shape can be measured quickly and with high accuracy. In addition, since such a displacement meter can measure the surface shape of the wafer without contacting the wafer, the surface shape can be easily and stably measured without causing scratches or contamination on the wafer to be evaluated. be able to.

  Furthermore, as another form of the surface shape measuring means for measuring the surface shape of the wafer, for example, a capacitance type flatness measuring device which is a capacitance type displacement meter (thickness meter) sensor is used. You can also. By using such a capacitance type displacement meter, the surface shape of the front surface and / or the back surface of the wafer can be measured quickly and stably with high accuracy without contact as described above. As such a capacitance type flatness measuring device, a commercially available non-contact wafer thickness, flatness, BOW / WARP measuring device, for example, Ultra gauge 9900 manufactured by ADE, etc. can be used.

  In the shape evaluation apparatus 11 (or the shape evaluation apparatus 12), the storage means 2 and the arithmetic processing means 3 include, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like. It can be incorporated into the computer 5 provided. The computer 5 inputs, for example, wafer surface shape data output from the displacement meter 8 and stores it in the storage means 2, and uses a RAM as a work area, a predetermined analysis program built in the ROM, that is, the arithmetic processing means 3. , And a reference line can be calculated from the surface shape data previously stored by the CPU, or a local slope can be obtained from a difference in the thickness direction between the reference line and the surface shape data.

Next, the wafer shape evaluation method of the present invention will be described in detail with reference to the drawings. FIG. 1 is a flowchart showing an example of the shape evaluation method of the present invention.
In the shape evaluation method of the present invention, first, the surface shape of the front surface and / or back surface of the wafer is measured (step A in FIG. 1). For example, the surface shape measuring means 1 of the shape evaluation apparatus 11 shown in FIG. 5 is used to place the wafer 6 on the sample stage 7 in a non-adsorptive state and scan the displacement meter 8 along the radial direction of the wafer. The surface shape of the front surface (or back surface) of the wafer 6 is measured, and the measured surface shape data of the wafer is sequentially stored in the storage means 2.

  Further, for example, when the surface shape measuring means 4 shown in FIG. 7 is used when measuring the surface shape of the wafer, the surface shapes of the front surface and the back surface of the wafer held in a non-adsorbed state can be obtained with two displacement meters 10. The surface shape data of the front surface and the back surface of the wafer can be obtained.

  At this time, the surface shape of the wafer can be measured with a high precision by scanning the front surface and / or back surface of the wafer at a fine measurement interval with a displacement meter. Shape evaluation can be performed with excellent accuracy. For example, by setting the wafer scanning interval to 1 mm or less, particularly about 0.05 mm, the surface shape of the wafer can be measured with excellent measurement accuracy.

  Thus, by measuring the surface shape of the wafer using the surface shape measuring means 1 shown in FIG. 5, for example, surface shape data of the wafer surface as shown in FIG. 2 can be obtained. The surface shape data shown in FIG. 2 is obtained by placing a wafer having a diameter of 300 mm in a non-adsorption state, and scanning a displacement meter in a radial direction from −150 mm to 150 mm at intervals of 0.05 mm with respect to the wafer center. Measured. In the surface shape data of FIG. 2, long-period waviness and measurement noise are observed.

  In the present invention, the sign (plus / minus) of the surface shape data changes to plus or minus depending on whether the main surface of the wafer to be measured is the front surface or the back surface. Which symbol is used is arbitrary, and it is sufficient that the direction in which the shape of the wafer is changed can be evaluated without making a mistake when evaluating the wafer shape.

  Moreover, in this invention, when evaluating the shape of a wafer, it is preferable to exclude the area | region of about 0.5 mm-2 mm from the outer peripheral end of a wafer. In general, a chamfering process is performed on the outer peripheral portion of a semiconductor wafer in order to prevent the wafer from being chipped. Therefore, as shown in FIG. 9, a chamfered portion is formed at the outer peripheral end of the wafer. The width of the chamfered portion varies depending on the wafer manufacturing method, but is usually about 300 to 500 μm. Conventionally, when measuring the shape of a wafer, in order to exclude the shape of the chamfered portion of the wafer from the object of measurement, a region excluding the chamfered portion of the wafer, for example, a region excluding about 3 mm or 2 mm from the outer peripheral edge of the wafer is used. Measurements are often made. However, in recent years, it has been desired to perform evaluation up to the vicinity of the boundary between the wafer main surface and the chamfered portion. Therefore, under the present circumstances, it is preferable to evaluate the wafer shape by excluding a region (measurement exclusion region) of about 0.5 mm to 2 mm from the outer peripheral edge of the wafer including the chamfered portion. Can be evaluated.

  Next, by removing long wavelength components and / or measurement noises from the wafer surface shape data measured by the surface shape measuring means and stored in the storage means, the arithmetic processing means 3 performs, for example, as shown in FIG. Data can be obtained (step B in FIG. 1). The data shown in FIG. 3 shows the wafer surface in the range of 120 to 148 mm from the wafer center, with the area from the wafer outer edge to 2 mm after removing the long wavelength component and the measurement noise. This shows the surface shape data.

  In the present invention, it is not always necessary to remove such a long wavelength component and measurement noise. However, by removing the long wavelength component and measurement noise in this way, local changes existing on the wafer are eliminated. Can be measured accurately, and the wafer shape can be evaluated with higher accuracy.

  At this time, the method of removing the long wavelength component and the measurement noise from the surface shape data is not particularly limited. For example, the removal of the long wavelength component can be easily performed by applying a least square method approximation or a high-pass filter. The measurement noise can be easily removed by performing a moving average operation of about 1 to 2 mm, a low-pass filter, or the like.

  After removing the long wavelength component and the measurement noise from the surface shape data in this way, a reference line is calculated from a predetermined region of the surface shape data obtained using the arithmetic processing means 3 (step of FIG. 1). C). The reference line can be easily calculated from a predetermined region of the surface shape data by using a method such as a least square method, a simple average, or a moving average.

  At this time, the area of the surface shape data for calculating the reference line is preferably an area within a range of 10 mm to 5 mm from the outer peripheral edge of the wafer, for example, an area of 10 to 5 mm from the outer peripheral edge of the wafer, or 10 to 7 mm. What is necessary is just to calculate a reference line from the surface shape data in a region or a region of 7 to 5 mm. By calculating the reference line from the surface shape data of such a region, the local slope existing in the outer periphery of the wafer, particularly in the region outside 10 mm from the outer peripheral edge of the wafer, can be obtained with high accuracy. Further, by calculating the reference line in this manner, for example, when the wafer is attracted to the chuck, the local slope can be obtained assuming that the influence of the component whose wafer shape is corrected by the adsorption is removed. More accurate shape evaluation can be performed.

  Then, a difference in the thickness direction between the reference line calculated in this way and the surface shape data measured by the surface shape measuring means is obtained by using the arithmetic processing means 3, for example, as shown in FIG. It is possible to measure a local slope having a spatial wavelength shorter than bow or warp (step D in FIG. 1).

  By measuring the local slope of the wafer in this way, the shape of the wafer from a different point of view from the conventionally used indexes such as GBIR and SFQR, particularly in the outer peripheral portion of the wafer such as the region outside the outer peripheral edge of the wafer. Effective information about the wafer shape can be obtained quantitatively, and the shape quality of the wafer, which could not be confirmed in the past, can be accurately evaluated based on a certain standard. In the above description, the case where the shape of the surface of the wafer is mainly evaluated is described as an example. However, the shape evaluation method of the present invention is not limited to the surface of the wafer but also the back surface of the wafer and the front and back surfaces of the wafer. The shape on both sides can also be accurately evaluated.

  Furthermore, in the wafer shape evaluation method of the present invention, the evaluation of the shape in the radial direction of the wafer can be performed radially over the entire circumference of the wafer. Accordingly, the shape of the entire circumference of the wafer can be accurately evaluated based on a certain standard, and the shape of the wafer can be grasped in more detail. For example, the shape evaluation in the wafer radial direction is performed about 360 to 400 times within the wafer surface at intervals of 1 ° or less of the wafer center angle, so that the shape of the entire circumference of the wafer can be evaluated with a very high accuracy in a map diagram. For example, it is possible to accurately grasp the abnormal value in the wafer surface and the position and size of the inflection point.

  As described above, if the shape of the wafer, particularly the shape of the outer peripheral portion of the wafer, is evaluated by the shape evaluation method of the present invention, it is possible to detect, for example, a wafer shape that causes a problem in the device manufacturing process with high accuracy. It becomes. For this reason, it has become possible to accurately determine a wafer in which a defocus failure or the like occurs in a device manufacturing process, which has been difficult in the past, and to specify the cause of the defocus failure or the like. As a result, the device manufacturing process Yield can be improved.

  In the shape evaluation method of the present invention, the wafer to be evaluated is mainly a semiconductor wafer, but other shapes such as a quartz substrate can also be evaluated. In the present invention, the local slope obtained as described above can be used as an analysis parameter for various experimental data. In addition to the above-mentioned local slope, a flat surface such as SFQR as used conventionally can be used. By combining with other evaluation parameters such as degree and surface roughness, the shape of the wafer can be evaluated in more detail.

  Furthermore, according to the present invention, there is provided a management method for performing quality control of a wafer and / or process management of a process for manufacturing a wafer based on a wafer shape evaluation result obtained by the wafer shape evaluation method of the present invention. Can be provided.

  As described above, based on the evaluation result obtained by the shape evaluation method of the present invention, for example, a wafer satisfying a predetermined standard is selected, or a local etching process such as plasma etching is performed so that the wafer has a desired shape. If the quality of the wafer is controlled by processing, the yield in the next process such as the device manufacturing process can be greatly improved. In particular, if a wafer having a shape suitable for the device manufacturing process is selected and only the wafer is supplied to the device manufacturing process, a very stable device can be formed.

  Furthermore, if the evaluation results obtained by the shape evaluation method of the present invention are accumulated, the capability of the wafer manufacturing process can be grasped, and an abnormality in the wafer manufacturing process can be easily compared by comparing the evaluation results. You can also find it. Therefore, it becomes possible to precisely manage the wafer manufacturing process, and to manufacture a stable wafer.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
Example 1
First, a silicon single crystal having a diameter of 300 mm was pulled by the CZ method, and the obtained single crystal was sliced, chamfered, lapped, and polished to produce a silicon wafer. Next, using the shape evaluation apparatus 11 as shown in FIG. 5, the produced silicon wafer having a diameter of 300 mm is placed on the sample stage 7 without suction, and the surface of the wafer is scanned in the radial direction by the displacement meter 8. The obtained surface shape data of the wafer surface was stored in the storage means 2 of the computer 5.

  Subsequently, the surface shape data stored in the storage unit 2 is subjected to a moving average of 2 mm by using the arithmetic processing unit 3 to remove measurement noise, and after applying a least square method approximation to remove long wavelength components. The reference line was calculated from the area of 10 mm to 5 mm from the outer peripheral edge of the silicon wafer using the method of least squares. The result is shown in FIG.

  Thereafter, the local slope of the outer peripheral portion of the wafer was measured by obtaining the difference between the reference line and the surface shape data in a region outside the position 10 mm from the outer peripheral edge of the silicon wafer. The result is shown in FIG.

  As shown in FIG. 4, an inflection point was observed in the vicinity of 7 mm from the outer peripheral edge of the wafer manufactured in Example 1, and it was confirmed that the local slope gradually increased from that point. It was done.

(Example 2 and comparative example)
Next, a silicon single crystal having a diameter of 200 mm was pulled up by the CZ method, and a silicon wafer was produced by performing the same treatment as in Example 1 above. Next, using the shape evaluation apparatus 12 as shown in FIG. 7, the produced silicon wafer having a diameter of 200 mm is held on the wafer support 9, and the front and back surfaces of the wafer are scanned in the radial direction with the displacement meter 10. The obtained wafer front and back surface shape data were stored in the storage means 2 of the computer 5.

  Subsequently, similarly to Example 1, the arithmetic processing means 3 is used to remove the measurement noise by performing a moving average of 2 mm on the surface shape data of the wafer front and back surfaces, and to apply a least square method approximation to obtain a long wavelength. After removing the components, a reference line was calculated using a method of least squares from an area of 10 mm to 5 mm from the outer peripheral edge of the silicon wafer.

  Then, the local slope of the outer peripheral part in the surface of a wafer and a back surface was measured by calculating | requiring the difference of a reference line and surface shape data in the area | region outside the position of 10 mm from the outer peripheral edge of a silicon wafer. Then, the measurement of the local slope as described above was performed in eight directions within the wafer surface, and the shape of the outer peripheral portion of the wafer was evaluated (Example 2). The result is shown in FIG.

  Next, with respect to the silicon wafer on which the local slope was measured, the thickness uniformity in the eight directions within the wafer surface was determined by SFQR used in the past, and the shape of the outer peripheral portion of the wafer was evaluated (comparative example). The result is shown in FIG.

As shown in FIG. 10, as a result of evaluating the shape of the wafer by the shape evaluation method of the present invention, the local slope increases in the outer peripheral portion in the directions (c) and (d) of the wafer, and the shape of the wafer is abnormal. It was confirmed that there is. Therefore, it was found that this silicon wafer is highly likely to become defective in the device manufacturing process.
On the other hand, when the thickness uniformity of the wafer was evaluated by SFQR, no abnormality was observed in the shape of the wafer as shown in FIG.

  In addition, this invention is not limited to the said embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

It is the flowchart which showed an example of the shape evaluation method of the wafer which concerns on this invention. It is the graph which showed the surface shape data of the wafer surface. It is the graph which showed the surface shape data after performing the removal of a long wavelength component, and the removal of measurement noise. It is the graph which showed the local slope of the wafer measured by the present invention. It is a schematic explanatory drawing which shows an example of the shape evaluation apparatus used with the wafer shape evaluation method of this invention. It is explanatory drawing explaining the measurement of the surface shape data of the wafer by the displacement meter of the shape evaluation apparatus of FIG. It is a schematic explanatory drawing which shows another example of the shape evaluation apparatus used with the wafer shape evaluation method of this invention. It is explanatory drawing explaining the measurement of the surface shape data of the wafer by the displacement meter of the shape evaluation apparatus of FIG. It is a schematic explanatory drawing which represented the shape of the outer peripheral part of a wafer roughly. It is a result figure which shows the result of having evaluated the shape of the wafer outer peripheral part in Example 2 by the shape evaluation method of this invention. It is a result figure which shows the result of having evaluated the shape of the wafer outer peripheral part by SFQR in the comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Surface shape measuring means, 2 ... Memory | storage means, 3 ... Arithmetic processing means,
4 ... Surface shape measuring means, 5 ... Computer, 6 ... Wafer,
7 ... Sample stage, 8 ... Displacement meter, 9 ... Wafer support,
DESCRIPTION OF SYMBOLS 10 ... Displacement meter 11, 12, ... Shape evaluation apparatus.

Claims (10)

A method of evaluating the shape of a wafer, wherein the surface shape of the wafer is measured by scanning the front surface and / or back surface of the wafer along the wafer radial direction, and the measured surface shape data is obtained from the outer peripheral edge of the wafer. By calculating a reference line from a region within a range of 10 mm to 5 mm and obtaining a local slope representing a difference in the thickness direction between the calculated reference line and the surface shape data, the surface shape and / or the back surface of the wafer A method for evaluating a shape of a wafer, wherein the shape is evaluated in a region outside a position 10 mm from the outer peripheral edge of the wafer. 2. The wafer shape evaluation method according to claim 1 , wherein the measurement of the surface shape of the wafer is performed in a non-adsorbed state of the wafer. 3. The wafer shape evaluation method according to claim 1, wherein the wafer surface shape is measured by scanning the front surface and / or back surface of the wafer at intervals of 1 mm or less. The calculation of the reference line, the least squares method, a simple average, a wafer shape evaluation method according to any one of claims 1 to 3, characterized suggested to use a moving average or a method . After measuring the surface shape of the wafer, wafer according to any one of claims 1 to 4, characterized in that the removal of the long wavelength components and / or measurement noise on the surface shape data the measurement Shape evaluation method. 6. The wafer shape evaluation method according to claim 5 , wherein the removal of the long wavelength component is performed by applying a least square method approximation or a high pass filter. 6. The wafer shape evaluation method according to claim 5 , wherein the measurement noise is removed by applying a moving average or a low-pass filter. Wafer shape evaluation method according to any one of claims 1 to 7, characterized in that over the shape evaluation of the wafer wafer the entire circumference. When measuring the surface shape of the wafer, the front surface and / or the back surface of the wafer is scanned in a non-contact manner using a displacement meter equipped with a laser oscillator and an automatic focusing mechanism, or a capacitive displacement meter. the shape evaluation method of the wafer according to any one of claims 1 to 8, characterized in that the measurement of the wafer surface shape. Based on the wafer shape evaluation result obtained by the wafer shape evaluation method according to any one of claims 1 to 9 , the wafer quality control and / or the process control of the wafer manufacturing process is performed. Management method.

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