JP2007115870A - Wafer crack inspecting apparatus, crack inspecting method and wafer manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crack inspecting apparatus and a crack inspecting method for detecting a fault in a higher correlation with generation of crack in the device manufacturing step, and for realizing non-desctructive inspection. <P>SOLUTION: The wafer crack inspecting apparatus comprises a polarized displacement measuring device for inspecting at least the polarized element of the light incident to the wafer and transmitted therethrough. This polarized displacement measuring device measures intensity of the S polarized element and P polarized element of the wafer, and computes polarized displacement to determine whether a crack is generated in the wafer from the polarized displacement. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to inspection of occurrence of cracks such as silicon wafers, and more particularly to a wafer inspection apparatus and crack inspection method for wafers that are highly correlated with the occurrence of cracks in a device process.

In the semiconductor device manufacturing process, a large loss occurs when cracks occur in the silicon wafer of the material. For this reason, there is a high demand for wafers that are difficult to break during device manufacturing.
In semiconductor and liquid crystal manufacturing processes, especially dry etching, ion implantation, vapor deposition, etc., high temperature / rapid heating / quenching has progressed, and the number of manufacturing processes performed by vacuum and dry processing has increased. ing. In addition, silicon wafers and glass substrates as substrates have become larger in diameter, and data relating to the occurrence of cracks in the wafer is becoming more important.

Conventionally, a “selective etching method” is generally used as a method for evaluating whether or not cracking occurs in the wafer against these thermal shocks. This is a technique for observing the etching state by putting a silicon wafer into “hydrofluoric acid + nitric acid + acetic acid + water” or “chromic acid + hydrofluoric acid + nitric acid + acetic acid + water”.
However, this measurement method has a large variation in personal measurement such as the temperature of the acid and the procedure of the worker, and is a method that is not suitable in terms of the environment because it uses a strong acid. In addition, even a wafer that does not have a problem with this method may break in the device manufacturing process, and its evaluation capability is very inferior as a cracking inspection method.

  In addition, “X-ray topograph (XRT)” using X-rays is used as an improvement of the above-described drawbacks such as variations in measurement work. However, this method requires expensive equipment, requires the use of X-rays, and may have an influence on the surroundings, so that general evaluation is difficult. In addition, even in this method, even a wafer that is determined to have no problem may be broken in the device manufacturing process, and the evaluation ability is inferior.

  Conventionally, since there is no equipment that evaluates and inspects the easiness of wafer cracking in the process, small scratches, cracks, and chips on the wafer have been confirmed and removed with a microscope or an optical wafer edge inspection apparatus. However, a wafer that has been determined to be a non-defective product by the above-described equipment may be cracked during the process.

  As another method, for example, Patent Document 1 reveals a latent defect by applying an impact to the wafer from the outside using a steel ball even if an invisible defect is latent on the wafer. A method for discriminating defective products is disclosed. However, this method has a problem that a new scratch may occur on the wafer. For this reason, the wafer subjected to this inspection is difficult to make a product, and 100% inspection cannot be performed.

JP-A-6-29362

  The present invention has been made in view of such problems, and it is possible to detect defects that have a high correlation with the occurrence of cracks in the device manufacturing process, and to detect cracks in wafers that can be inspected nondestructively. An object is to provide an inspection apparatus and a crack inspection method.

  In order to achieve the above object, the present invention is a wafer crack inspection apparatus, comprising at least a polarization displacement measuring device for detecting a polarization component of light incident on and transmitted through a wafer, and the polarization displacement The measuring device measures the intensity of the S-polarized component and the P-polarized component of the wafer, calculates the amount of polarization displacement, and determines whether or not the wafer is cracked from the amount of polarization displacement. A feature of the wafer crack inspection apparatus is provided.

  With such a wafer crack inspection apparatus, data highly correlated with cracks generated during the process can be obtained, and the wafer crackability can be inspected more accurately. Further, this is a non-destructive inspection, and it is possible to perform a crack inspection on the total number of wafers to be shipped without causing any new scratches on the wafer.

Further, it is desirable that a microscope for detecting a scratch on the wafer is provided, and the microscope measures the size of the scratch on the wafer.
In this way, if the microscope further comprises a microscope for detecting scratches on the wafer, and the microscope measures the size of the scratches on the wafer, the wafer is inspected along with the polarization displacement measuring device. It can be carried out.

At this time, it is desirable that the microscope is of an optical type.
Optical microscopes are often used for wafer scratch detection and size measurement in wafer crack inspection. And handling is also comparatively easy.

Further, it is desirable to include a stage for holding a cassette for storing the wafer and a transfer robot for transferring the wafer in and out of the cassette for inspection.
In this way, if the apparatus further comprises a stage for holding a cassette for storing the wafer and a transfer robot for transferring the wafer in and out of the cassette for inspection, handling by the person when the wafer is set on the holding means. For this reason, it is possible to prevent generation of new scratches due to handling.

In addition, it is preferable that the transfer robot is disposed between the polarization displacement measuring device and the cassette stage.
In such a crack inspection apparatus, since the transfer robot is disposed between the polarization displacement measuring device and the cassette stage, the wafer can be transferred between the cassette stage and the polarization displacement measuring device at high speed and smoothly. It is possible to advance the crack inspection efficiently.

Further, it is desirable to include a device that controls the entire device and automatically determines whether or not the wafer is cracked based on the result of the polarization displacement measuring device (claim 6).
Thus, if the crack inspection apparatus further includes a device that controls the entire apparatus and automatically determines whether or not a crack occurs on the wafer from the result of the polarization displacement measuring apparatus, a person is involved. The crack inspection can be performed automatically and efficiently without any trouble. For example, when a microscope is further provided, a wafer can be evaluated by a polarization displacement measuring device and another wafer can be evaluated simultaneously and in parallel by a microscope, so that a crack inspection can be performed at high speed. It is.

  Further, the present invention is a method for inspecting a crack of a wafer, and measures at least the intensity of an S-polarized component and a P-polarized component of light incident on and transmitted through the wafer, calculates a polarization displacement amount, and calculates the polarization displacement amount. From the above, there is provided a wafer crack inspection method for determining whether cracks occur in a wafer (claim 7).

  In this way, at least the intensity of the S-polarized component and the P-polarized component of the light incident on and transmitted through the wafer is measured, the amount of polarization displacement is calculated, and whether or not cracking occurs on the wafer from the amount of polarization displacement. If it is a wafer crack inspection method for determining whether or not the wafer has been detected, the amount of polarization displacement having a high correlation with the crack generated during the process can be obtained and the crack determination is performed, so that the wafer crack inspection can be performed more accurately. it can. Further, this is a non-destructive inspection method, and it is possible to perform a crack inspection on the total number of wafers to be shipped without newly damaging the wafer.

Here, when the dispersion value (VAR) of the polarization displacement amount is less than 100 DU in a 500-micron pixel, it can be determined that no crack occurs in the wafer.
As described above, when the dispersion value (VAR) of the polarization displacement amount is less than 100 DU in a 500-micron pixel, it is possible to more reliably select non-defective products if it is determined that the wafer does not crack. It is possible to provide a wafer in which cracking does not occur.

The present invention also includes at least a slicing step for slicing a wafer from an ingot block, a chamfering step for chamfering the outer periphery of the sliced wafer, a flattening step for flattening the chamfered wafer, and the flattening. In a method for manufacturing a wafer, comprising: an etching step for removing processing distortion of the formed wafer; and a polishing step for polishing both surfaces or one side of the etched wafer. At least the light incident on the wafer and transmitted therethrough The intensity of the S-polarized component and the P-polarized component is measured, the amount of polarization displacement is calculated, and whether or not the wafer is cracked is determined from the amount of polarization displacement, and the wafer that is determined to be cracked is removed. Provided is a wafer manufacturing method in which a crack inspection step is performed at least once.
With such a wafer manufacturing method, the crack inspection process can be performed without newly damaging the wafer, and only a high-quality wafer can be manufactured, so that the yield can be improved.

At this time, when the dispersion value (VAR) of the polarization displacement amount is less than 100 DU in a 500-micron pixel, it can be determined that no crack occurs in the wafer.
As described above, when the dispersion value (VAR) of the polarization displacement amount is less than 100 DU in a 500-micron pixel, it is possible to more reliably select non-defective products if it is determined that the wafer does not crack. A wafer that does not generate cracks can be produced.

  With the wafer crack inspection apparatus and inspection method of the present invention, the amount of polarization displacement having a high correlation with the wafer crack actually generated in the process is obtained, and the crack determination is performed based on the obtained value. It is possible to select good products that do not occur. Further, since it is a non-destructive inspection, it is possible to perform a crack inspection on the total number of wafers shipped as products without damaging the wafer, and the yield is improved.

As a conventional method for inspecting the occurrence of cracks in a wafer, for example, there is a method of examining a surface scratch by etching, or evaluating by using an X-ray topograph or the like. In addition, there are a discrimination method based only on a measurement result of the size of a scratch by a microscope, and a method of discriminating a defective product by revealing a latent defect by applying a shock to the wafer from the outside using a steel ball.
However, these inspection methods have a low correlation with the occurrence of cracks in the wafer in the device manufacturing process, and cracks may occur in the process even if they are determined to be good products by the above method. In addition, since there is a possibility that a new scratch may be applied to the wafer, there has been a problem that it is impossible to perform 100% inspection.

  Further, in the research by the present inventors, a small strain (local strain) existing inside the wafer that cannot be detected only by observing the surface of the wafer, such as the above-described method using only a microscope, is caused by the semiconductor. It was found that cracking occurred in the device manufacturing process.

  Therefore, the present inventors are a wafer crack inspection apparatus, comprising at least a polarization displacement measuring device that detects a polarization component of light incident on and transmitted through the wafer, the polarization displacement measuring device comprising: Wafer crack inspection apparatus and crack inspection method for measuring the intensity of the S-polarized component and the P-polarized component of the wafer, calculating the amount of polarization displacement, and determining whether the wafer is cracked based on the amount of polarization displacement Was invented.

  Such a cracking inspection apparatus and inspection method is caused by the above-mentioned local distortion, and the intensity of the S-polarized component and the P-polarized component caused by birefringence when light is applied to the wafer, and the calculated polarization displacement amount A crack determination is performed, and a determination having a high correlation with cracks generated during the process can be performed. In addition, since it is a non-destructive inspection, the wafer after inspection can be handled as a product, and 100% inspection can be performed. In this way, the inventors have found that the wafer crack inspection can be performed more reliably and completed the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Here, FIG. 1 is a schematic view showing an example of the configuration of the crack inspection apparatus of the present invention.
In the crack inspection apparatus 1 of the present invention, a polarization displacement amount measuring apparatus 2 is first arranged.
Here, the polarization displacement measuring device 2 which is the basic configuration of the cracking inspection device 1 of the present invention will be described in detail with reference to FIG.
The polarization displacement amount measuring device 2 used in this example includes a detector 29 that detects a polarization component and measures the intensity, and a calculator 30 that calculates the polarization displacement amount. As described above, as a cause of cracks that occur during the device manufacturing process, for example, local strain can be cited. This local strain causes optical anisotropy such as birefringence. Therefore, light 26, for example, a linearly polarized infrared laser is incident on the periphery of the wafer W, and the polarized components (P-polarized component 27, S-polarized component 28) (generated by birefringence) of the transmitted light are detected. By detecting at 29, the above-mentioned optical anisotropy existing inside the wafer W is detected. Then, as described below, the amount of polarization displacement is calculated by the calculator 30 based on the polarization component detected and measured by the detector 29.

An unstrained silicon wafer has almost no optical anisotropy, but if there is a strain, anisotropy of the optical constant occurs at the peripheral portion, and a polarization component is generated in the transmitted light. Here, when the polarization intensities of the P-polarized component and the S-polarized component of the transmitted light detected and measured are defined as Pp and Ps, respectively, the amount of polarization displacement (hereinafter sometimes referred to as D value (Depolarization)). Is
D = 1− (Pp−Ps) / (Pp + Ps) = 2Ps / (Pp + Ps)
Indicated by

However, even if the intensity of the S polarization component is simply measured, a sufficient signal cannot be obtained because the intensity is insufficient. For this reason, the polarization displacement measuring device 2 of this example detects light synthesized by a method called homodyne synthesis.
For this reason, the D value is a value after homodyne synthesis, the optical anisotropy does not exist inside the wafer W, and the reference D value when the S-polarized component is not detected is not 0 but a constant value (D0 )
When the wafer W is subjected to stress, the birefringence changes due to the photoelastic effect. Therefore, as the strain increases due to the stress, the D value fluctuates from the constant value D0.

  As described above, the polarization displacement measuring device 2 used in this example detects the polarization components (P-polarization component 27, S-polarization component 28) of the light that has entered the sample and transmitted as described above, and the intensity thereof. And a calculator 30 for calculating the amount of polarization displacement. In this example, a product manufactured by TePla in Germany is used. However, the present invention is not limited to this, and any device that can determine the amount of polarization displacement may be used.

  As shown in FIG. 1, in this example, a microscope 3 is disposed adjacent to the polarization displacement measuring device 2. The microscope 3 detects scratches on the surface of the sample, and includes holding means 7 that holds the wafer W as shown in FIG. Examples of the microscope 3 include an optical one, but are not limited to visible light, and may be a method using a laser beam or an electron beam. Any method can be used as long as it can detect a scratch on the sample and measure its size.

  The holding means 7 may be an electrostatic chuck type, for example. As shown in FIG. 2 (A), in this example, 100 mm at the center of the wafer W is held by an electrostatic chuck, and can be rotated as shown in FIGS. 2 (B) and 2 (C). It is easy to detect and measure scratches by tilting W. As a result, it is possible to measure even at the periphery of the wafer W, for example. The holding means 7 for the wafer W is not particularly limited as long as it does not damage the wafer W.

  In addition, there is a cassette stage 4 that holds a cassette that accommodates the wafer W, and a wafer W transfer robot 5 is provided between the stage 4 and the position of the polarization displacement measuring device 2. The cassette contains a wafer W as a sample. The transfer robot 5 has, for example, an extendable arm, and holds the wafer W at the end of the arm for transfer. The holding unit may be any unit that does not damage the wafer W, and for example, a unit based on electrostatic adsorption can be considered. Moreover, the clip etc. to which the nonwoven fabric was attached | subjected to the contact part with a wafer may be used. Then, the wafer W is taken out from the cassette arranged on the cassette stage 4 and transported to the polarization displacement measuring device 2 and the microscope 3 for crack inspection. It also has the role of returning the wafer W to the cassette after inspection.

  Furthermore, a device 6 is provided which controls the entire crack inspection device and automatically makes a crack determination. This device 6 is constituted by a computer, and controls each of the above-described devices when performing a crack inspection. Further, for example, it is automatically determined from the polarization displacement amount obtained by the polarization displacement amount measuring device 2 based on a preset reference whether or not the wafer W is cracked. is there.

Thus, the crack inspection apparatus 1 of the present invention includes at least the polarization displacement amount measuring device 2 as described above, and calculates the polarization displacement amount (D value) by the polarization displacement amount measuring device 2, It is determined whether or not cracking occurs in the wafer W from the D value.
With this crack inspection apparatus 1 of the present invention, data having a high correlation with the crack of the wafer W generated during the device manufacturing process can be obtained. Therefore, a high-quality wafer W that is less likely to crack is more accurately selected. It is possible. In addition, since it is a non-destructive inspection apparatus, the wafer after inspection can be handled as a product without any problem, and 100% inspection can be performed without the need for extra cost, and the wafer W that is hard to break can be efficiently provided.

  Further, the crack inspection apparatus 1 of this example further includes a microscope 3. The microscope 3 detects scratches on the wafer W and measures the size of the scratches to add new reference data for determining the occurrence of cracks in the wafer W to the data from the polarization displacement measuring device 2. You can also. In particular, those with scratches are easy to generate not only cracks but also particles, so it is meaningful to measure them together with the amount of polarization displacement. As described above, the microscope 3 only needs to be capable of measuring the size of the scratch. Optical ones are often used and are relatively easy to handle.

Further, if a stage 4 for holding a cassette for storing the wafer W and a transfer robot 5 for transferring the wafer W in and out of the cassette for the crack inspection are provided, it is possible to prevent human hands from intervening. It is possible to prevent the wafer W from being newly scratched by handling by a person.
At this time, if the transfer robot 5 is disposed between the position of the polarization displacement measuring device 2 and the cassette stage 4, the wafer W can be transferred smoothly and at high speed, so that the crack inspection is efficiently performed. Can proceed.

  In addition, the device 6 is provided with a device 6 that controls the operation of each unit as described above, and further automatically determines whether or not the wafer W is cracked based on the measurement result of the polarization displacement measuring device 2 and the microscope 3. The crack inspection apparatus 1 can move each part efficiently, transport the wafer W to each part appropriately, and perform the crack inspection one after another, thereby reducing time and improving inspection efficiency. For example, when the inspection is performed with the polarization displacement measuring device 2, the inspection can be performed with the microscope 3 on another wafer W at the same time. Further, if necessary, it is possible to cause the transport robot 5 to transport and sort the wafers W determined to be abnormal into a BOX for storing abnormal products.

  By using such a wafer crack inspection apparatus 1 of the present invention, light is applied to an internal strain (local strain) that cannot be detected only from the appearance of the wafer W, the polarization component is detected, and the intensity is measured. Then, if the amount of polarization displacement is obtained and the occurrence of cracking is determined based on the value, this determination method has a good correlation with the cracking of the wafer W, and the occurrence of cracking can be more accurately determined. Non-defective products can be selected and sent to the manufacturing process, and production efficiency and yield can be improved. Further, since the crack inspection method of the present invention is a non-destructive inspection, all wafers W to be shipped can be inspected without damaging the wafer W.

Here, for example, if it is determined that there is no crack in the wafer W when the dispersion value of the polarization displacement amount is less than 100 DU at 500 micron pixels, the wafer W that is easily broken is removed in advance and the non-defective product is selected. Can do. In this example, the dispersion σ (local distortion value) of the D value that can be detected by, for example, 500 micron pixels (the minimum detection size of the polarization displacement measuring device 2 used) is represented by “VAR DU / 500 micron pixel”.
Further, although the polarization displacement variance σ is used as the determination criterion for cracks, other determination criteria can be set in accordance with various conditions such as the size and type of the wafer W.

  In addition, a slicing process for slicing a wafer from an ingot block, a chamfering process for chamfering the outer peripheral portion of the sliced wafer, a flattening process for flattening the chamfered wafer, and processing of the flattened wafer In a wafer manufacturing method comprising an etching step for removing strain and a polishing step for polishing both or one side of the etched wafer, an internal strain ( The light is applied to the local distortion, the polarization component is detected, the intensity is measured to determine the amount of polarization displacement, the occurrence of cracking is determined based on the value, and the wafer determined to have cracking is removed. If the crack inspection process is performed at least once, only a high-quality wafer can be manufactured, and the yield can be improved.

  Here, if the dispersion value (VAR) of the polarization displacement amount is less than 100 DU with a 500 micron pixel, it is possible to more reliably sort a high-quality wafer, and to select a high-quality wafer during the device process. It is possible to manufacture a high-quality wafer that does not generate cracks.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.
(Example 1 and Comparative Example 1)
Wafers that have been physically impacted or damaged have poor thermal shock resistance and are likely to crack. Therefore, a sample wafer having various damages is prepared. First, as a non-destructive crack inspection method, crack inspection is performed using the crack inspection apparatus of the present invention shown in FIG. 1, and as a comparative example, a conventional method is used. A crack inspection with a microscope was performed to determine whether or not the wafer was broken. Thereafter, the samples subjected to both crack inspections were actually subjected to rapid heating and rapid cooling, and a process similar to the device manufacturing process was performed to see whether cracks occurred on the wafer. And, while examining the correlation between the crack inspection method using the crack inspection apparatus according to the present invention and crack (Example 1), the correlation between the conventional inspection method using only the microscope and the crack of the wafer is also the same. It investigated (comparative example 1).

In the crack inspection method using the crack inspection apparatus of the present invention, it is determined that cracks occur when a wafer having a D value variance σ (local distortion value) of “VAR 100DU / 500 micron pixels” or more is used as a crack determination criterion. did.
In addition, an optical microscope was used. The size of a scratch generated by the above damage was measured, and it was determined that a wafer having a scratch having a size of 15 μm or more was cracked.
In both methods, measurement was performed on the entire circumference of an area 50 mm inside from the wafer edge.

First, a silicon wafer obtained by processing a single crystal rod pulled up by the Czochralski method was prepared with a diameter of 300 mm, a thickness of 0.775 mm, a P-type <100>, and a resistivity of 10 Ω · cm. As sample wafers, sample wafers A to D were prepared.
As “Sample A”, as shown in FIG. 6, the silicon wafer is dropped so that the edge is downward, and hits the impact jig 23 to give physical impact / damage.
Drop height: 5cm, 7.5cm, 10cm, 15cm, 20cm,
Impact jig: SiC flat surface, SiC apex side.
Under these conditions, a sample was produced by the above method.

As “Sample B”, the wafer surface is dropped so as to be horizontal, and hits the impact jig 23 at the center of the wafer to give physical impact / damage.
Drop height: 10cm, 20cm,
Impact jig: quartz cylinder (diameter 50 mm), quartz cylinder (100 mm).
Under these conditions, a sample was produced by the above method.

As “Sample C”, damage due to abnormal handling was assumed in the wafer processing step. The wafer transported by the transport robot is caused to collide with a quartz wafer holder.
Two types of collision conditions were prepared: a frontal collision on the side surface of the wafer and a collision in which the lower surface of the wafer rides on the holder, and a sample was prepared. The impact (calculated value) due to the two collisions is the same as that when dropped from a height of 10 cm (lower surface portion) and 20 cm (side surface portion).

As “Sample D”, a static pressure load is applied with a crash tester. The crash test machine is a device that causes a wafer to crash by applying a static pressure load from three directions of the wafer edge (clockwise positions of 20 °, 140 °, and 260 ° with respect to the notch). Using this device, a sample was prepared by applying a static pressure load to the wafer.
Static pressure load: 20 kg load, 40 kg load, 60 kg load.
As described above, wafers were damaged by various methods to prepare various samples A to D.

  These samples A to D are subjected to a rapid heating and rapid cooling process under the following conditions. This rapid heating / cooling process is very similar to the actual device manufacturing process, and by performing this process, it is possible to accurately obtain data relating to the occurrence of wafer cracking that actually occurs in the device manufacturing process.

Hereinafter, an apparatus for performing the rapid heating / cooling process on the wafer will be described with reference to FIG.
Here, as shown in FIG. 4, the rapid heating / rapid cooling device 12 is constituted by a heat treatment furnace 13, a cooling device 14, and a wafer W holding jig 15.
In the heat treatment furnace 13, a cantal heater 18 is disposed around a quartz muffle 17, and the periphery thereof is covered with a heat insulating material 19 and a water-cooled tube 20. Further, the heat treatment furnace 13 and the outside of the furnace communicate with each other with the furnace door 21 interposed therebetween. The heat treatment furnace 13 is only required to rapidly heat the wafer W, and the heater may be resistance heating, lamp heating, or the like. In addition to quartz, the furnace can also use SiC.

  Next, the cooling device 14 includes an air cooling device 16 in this example. The air cooling device 16 is forcibly cooled by blowing air from the upper surface of the wafer W on the heat-treated holding jig 15. Further, the wafer holding jig 15 may be cooled by water cooling.

  The holding jig 15 for holding the wafer W is disposed on the autoloader 22, and the autoloader 22 continues into the heat treatment furnace 13 and the cooling device 14. Therefore, the rapid heating / cooling speed of the wafer W on the holding jig 15 on it can be controlled by adjusting the loading / unloading speed (wafer conveyance speed) of the autoloader 22 to and from the heat treatment furnace 13. Further, the wafer W can be reciprocated between the heat treatment furnace 13 and the cooling device 14, and rapid heating and rapid cooling can be continuously performed repeatedly.

Conditions for the rapid heating / cooling process of the wafer using such an apparatus are as follows.
Wafer holding jig: made of quartz Holds the notch direction at an angle of 45 ° with respect to the loading / unloading direction of the heat treatment furnace.
Heat treatment furnace: temperature setting 1000 ° C. under N ₂ atmosphere
Wafer transfer speed: 10 m / sec,
FIG. 7 shows the temperature profile of the rapid heating rate and rapid cooling rate under these conditions (measured with a platinum thermocouple).
One cycle is 35 minutes, inserted into a heat treatment furnace, rapidly heated and held for 15 minutes, then taken out, rapidly cooled and held at room temperature for 15 minutes. This is evaluated by cracking when 5 cycles are repeated.

As described above, the relationship between the crack determination obtained by performing the crack inspection of the present invention on each sample wafer and the wafer that was actually broken by the rapid heating / cooling process performed after the crack inspection of the present invention. The results of 1 are shown in Table 1 below.
Table 1 shows all the damaged samples, and shows the ratio of actual cracking in the samples having the D value variance σ calculated by the cracking inspection apparatus of the present invention.

As can be seen from Table 1, 30% of the samples in which the variance σ of the D value determined to generate cracks in the wafer is “VAR 100DU or more” are cracked, and account for a high percentage. I understand. In particular, in the sample of “VAR 200DU or more”, cracks occur in 70% of the samples.
On the other hand, cracking does not occur in the sample of “less than VAR 100 DU” determined not to cause cracking.

  Moreover, in all the cracked samples, cracking occurred from a location where the local strain was a strong value of “VAR 100DU or more”. In the crack inspection performed before the rapid heating / cooling step, there was a sample having a location where a clear flaw was not found only with a conventional microscope, although the local strain was strong. Such a wafer having no scratches and having a local strain VAR of 100 DU or more increased to 15% of the wafers cracked by thermal shock in the rapid heating / cooling process.

  Thus, it can be seen that the occurrence of cracks can be determined with high probability by the crack inspection method using the crack inspection apparatus of the present invention. The crack inspection method of the present invention and the occurrence of cracks in the wafer device manufacturing process have a high correlation. For example, a wafer that is easily distorted due to large distortion even if scratches are not detected from the appearance. Therefore, it is possible to provide a high-quality wafer by reliably removing it.

Next, Table 2 shows the results of Comparative Example 1.
Table 2 shows the relationship between crack determination based only on the size of scratches on the wafer surface using a microscope, which is a conventional crack inspection method, and the rate at which cracks actually occur.
As can be seen from Table 2, the crack occurrence rate is about 8% even for a sample having a scratch having a size of 15 μm or more, which is determined to be cracked. This is the same value as the crack occurrence rate of a sample having a scratch of a size of less than 15 μm, which was determined not to cause cracks, and the size of scratches present on the wafer surface and the occurrence of cracks. There is not much correlation. Furthermore, cracks occurred in 7% of the wafers that did not appear to be scratched even when damage was given, and there was little correlation between the size of the scratches on the wafer surface and the damage or cracks generated on the wafer. It seems to be.

(Example 2)
A crack inspection is performed on 100,000 processed wafers (PW) having a diameter of 300 mm processed and cleaned using the crack inspection apparatus of the present invention shown in FIG.
First, on the entire circumference of an area 50 mm inside from the wafer edge, as shown below, 400 PWs having relatively large measured values by the polarization displacement measuring device and the optical microscope of the crack inspection device of the present invention are 100,000. Sorted out of the sheets.
Measurement by polarization displacement measuring device: Local strain value (500 micron pixel) VAR 35DU or more,
Measurement with an optical microscope: Scratch MAX size 8 μm or more.
Under the same conditions as in Example 1, 400 PWs sorted according to the above criteria were actually subjected to a rapid heating / cooling process to confirm the occurrence of cracks.

The results of Example 2 are shown in FIG.
Here, the right half region 8 in FIG. 3 is a range in which it is determined that cracking occurs when the VAR DU value is 100 or more in the inspection method by the crack inspection apparatus of the present invention. The upper half region 9 is a region in which it is determined that cracking occurs when the size of the scratch is 15 μm or more by a conventional inspection method using only an optical microscope.
Further, the lower left area 10 is a range including 99600 samples other than the selected 400 sheets. The lower right region 11 is a sample group that is determined to have no crack in the conventional inspection using only the optical microscope.
When the 400 PW was subjected to a rapid heating / cooling process, it was “no abnormality 397 sheets, crack occurrence 3 sheets”. As described above, the frequency of occurrence of cracking during the device manufacturing process is considered to be about 3 out of 100,000.

Here, as can be seen from FIG. 3, all the above three defective wafers in the region 8 are detected by the crack inspection method using the crack inspection apparatus of the present invention, and cracks are generated in this test. Even if not, it is possible to remove the possibility of cracking in the device process. At the same time, it is possible to provide a large number of high-quality wafers that do not cause cracks in the region 9 that are determined as defective wafers in the conventional method without determining as defective wafers, thereby improving productivity and reducing costs. Can do.
On the other hand, in the conventional method in which cracking is determined only by the size of a scratch measured with a microscope, the sample in the region 11 is determined as a non-defective product, and a sample that may crack is missed.

As described above, the crack inspection method using the crack inspection apparatus of the present invention has a high correlation with the occurrence of cracks in the device manufacturing process, for example, a defect that was not found in the conventional crack inspection method using only an optical microscope. It is possible to determine that the wafer is a wafer that is easily broken. For this reason, a yield can be improved and a good quality wafer can be provided efficiently.
Moreover, since it is a non-destructive inspection, the crack inspection of the present invention can be performed on all wafers to be shipped, and the manufacturing efficiency of the device can be improved.

  In addition, this invention is not limited to the said form. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as 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 schematic which showed an example of the structure of the crack inspection apparatus of this invention. It is an example of holding | maintenance of the wafer in a microscope. It is a result of Example 2. It is the schematic of the apparatus which carries out rapid heating and rapid cooling of the wafer in each Example and a comparative example. It is the schematic which showed an example of the polarization displacement measuring device of the crack inspection apparatus of this invention. It is an example of the creation method of a damage wafer. 2 is a rapid heating / cooling temperature profile in Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wafer inspection apparatus of this invention, 2 ... Polarization displacement measuring device,
3 ... Microscope, 4 ... Cassette stage, 5 ... Transfer robot,
6 ... A device that automatically controls and cracks the entire device,
7 ... Means for holding the wafer of the microscope,
8: Range in which it is determined that cracking occurs in the inspection method using the cracking inspection apparatus of the present invention (VAR 100DU or more);
9: Range in which cracks are generated by a conventional inspection method using only an optical microscope (a scratch size is 15 μm or more),
10 ... 99600 samples included,
11 ... Sample group in which cracking is determined not to occur in the conventional inspection method using only an optical microscope, 12 ... Rapid heating / cooling device, 13 ... Heat treatment furnace,
14 ... Cooling device, 15 ... Holding jig, 16 ... Air cooling device,
17 ... Quartz muffle, 18 ... Kantal heater, 19 ... Heat insulation,
20 ... Water-cooled tube, 21 ... Furnace door, 22 ... Autoloader,
23 ... Impact jig, 26 ... Light, 27 ... P-polarized component,
28 ... S-polarized component, 29 ... Detector, 30 ... Calculator,
W ... wah.

Claims (10)

  A wafer inspection apparatus comprising at least a polarization displacement measuring device for detecting a polarization component of light incident on and transmitted through a wafer, the polarization displacement measuring device comprising the S polarization component and P of the wafer. A wafer crack inspection apparatus characterized by measuring the intensity of a polarization component, calculating a polarization displacement amount, and determining whether or not the wafer is cracked based on the polarization displacement amount.   2. The wafer crack inspection apparatus according to claim 1, further comprising a microscope for detecting a scratch on the wafer, wherein the microscope measures a size of the scratch on the wafer.   3. The wafer crack inspection apparatus according to claim 2, wherein the microscope is an optical type.   4. The apparatus according to claim 1, further comprising a stage for holding a cassette for storing the wafer and a transfer robot for transferring the wafer in and out of the cassette for inspection. The wafer crack inspection apparatus described.   The wafer crack inspection apparatus according to any one of claims 1 to 4, wherein the transfer robot is disposed between the polarization displacement measuring device and the cassette stage.   6. The apparatus according to claim 1, further comprising an apparatus for controlling the entire apparatus and automatically determining whether or not the wafer is cracked based on a result of the polarization displacement measuring apparatus. The wafer cracking inspection apparatus according to any one of the above.   This is a wafer crack inspection method, which measures at least the intensity of the S-polarized component and the P-polarized component of light incident on and transmitted through the wafer, calculates the amount of polarization displacement, and determines whether the wafer is cracked from the amount of polarization displacement. Wafer crack inspection method for determining whether or not it occurs.   The wafer crack inspection method according to claim 7, wherein when the dispersion value (VAR) of the polarization displacement amount is less than 100 DU in a 500-micron pixel, it is determined that the wafer does not crack.   At least a slicing step of slicing a wafer from an ingot block, a chamfering step of chamfering the outer peripheral portion of the sliced wafer, a flattening step of flattening the chamfered wafer, and processing of the flattened wafer In a wafer manufacturing method comprising an etching step for removing distortion and a polishing step for polishing one or both sides of the etched wafer, at least an S-polarized component and a P-polarized light that are incident on the wafer and transmitted therethrough At least one crack inspection step for measuring the intensity of the component, calculating the amount of polarization displacement, determining whether or not the wafer is cracked from the amount of polarization displacement, and removing the wafer determined to be cracked. A method for manufacturing a wafer, characterized in that the method is performed once.   10. The method of manufacturing a wafer according to claim 9, wherein when the dispersion value (VAR) of the polarization displacement amount is less than 100 DU in a 500-micron pixel, it is determined that no crack occurs in the wafer. 11.

Images