JP2021172573A - Method for determining defect region of wafer - Google Patents

Abstract

To provide a method for determining a defect region of a wafer, capable of easily and efficiently detecting and determining a B-band region and a dislocation cluster formation region in a silicon single crystal wafer.SOLUTION: A method for determining a defect region of a wafer cut and prepared from a silicon single crystal grown by the CZ method comprises: applying impurity metal having a concentration of 1×1011-1×1015 atoms/cm2 on the surface of the wafer to diffuse the impurity metal by heating; polishing and removing the surface layer of the wafer by 0.5 μm or more after the heating; measuring silicide defects due to the impurity metal on the surface of the wafer after the polishing by a particle counter; and determining whether or not a B-band region or an I-rich region is included in the wafer on the basis of the measured result.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for determining a defect region of a wafer produced by cutting out a silicon single crystal by the Czochralski Method (hereinafter, also referred to as the CZ method).

A material used as a substrate for a semiconductor device includes, for example, a silicon wafer, and the silicon wafer is mainly cut out from a silicon single crystal manufactured by the CZ method. In recent years, the miniaturization of devices has progressed due to the high integration of devices. Along with this, silicon wafers are required to have few or no defects near the surface. Wafers that meet the requirements include epitaxial wafers, annealed wafers, and defect-free PWs (polished wafers). Among these, it is the defect-free PW that can achieve high quality at a relatively low cost, and the defect-free PW is required to have few or no Green-in defects.

A Green-in defect in a silicon single crystal is a defect formed by agglutination of pores (Vacancy) or interstitial silicon (Interstitial-Si). Defects formed by agglutination of pores are called Void defects, and are classified into FPD (Flow Pattern Defect), COP (Crystal Originalized Particle), LSTD (Laser Scattering Tomography Defects), and the like according to the detection method. On the other hand, defects formed by agglutination of interstitial silicon are called dislocation clusters in which dislocation loops are clustered, and are detected as LEP (Large Etch Pit) by selective etching.
Pore or interstitial silicon is incorporated at the solid-liquid interface during silicon single crystal growth. It is known that which point defect becomes predominant is determined by the ratio (V / G) of the temperature gradient G and the crystal growth rate V at the growth interface.

The relationship between the V / G and the defect region in the silicon single crystal will be described with reference to FIG. FIG. 6 shows the result of manufacturing a silicon single crystal having a diameter of 300 mm by gradually reducing the growth rate V under the condition that G is constant in the growth direction, and vertically dividing the crystal to examine the defect distribution. That is, it shows the transition of the defect region corresponding to the change of V / G.
When V / G is larger than (V / G) critical, the pores are predominant, and when V / G is smaller, interstitial silicon is predominant. If the V / G is extremely large, the pores become excessive during crystal growth, and the pores aggregate to form voids (void formation region (V region)). On the contrary, if the V / G is extremely small, the interstitial silicon becomes excessive during crystal growth, and the interstitial silicon aggregates to form a dislocation cluster (dislocation cluster formation region (I-rich region)).
When a crystal is manufactured under an intermediate condition between a condition in which vacancies predominate and a condition in which interstitial silicon predominates, there are no vacancies or interstitial silicon, or the concentration is low enough not to form Void defects or dislocation cluster defects. A defect-free region crystal having only point defects can be obtained.
An R-OSF region in which stacking defects due to relatively large-sized oxygen precipitates are formed in as-grown is formed between the defect-free region and the void formation region, and between the defect-free region and the dislocation cluster formation region. There is a stacking defect formed by agglomerates of interstitial silicon, but there is a B-band region that has not led to the formation of dislocation loops.

Further, even if the pores are predominant in the defect-free region, the Green-in defect is not formed unless the amount is sufficient to form the Green-in defect. Such a region is called an Nv region (or Pv region). Green-in defects are not formed in the Nv region, but vacancies remain. The formation of oxygen-precipitated nuclei is promoted in a temperature range lower than the temperature at which the remaining pores form the Green-in defect. Since the oxygen precipitation reaction involves volume expansion, the increase in strain energy due to volume expansion due to the growth of the precipitate can be alleviated in the Nv region where there are residual vacancies in the surroundings, so that the oxygen precipitation reaction can easily proceed.
On the other hand, even if the interstitial silicon is dominant in the defect-free region, the Green-in defect is not formed unless the amount is sufficient to form the Green-in defect. Such a region is called a Ni region (or Pi region). Unlike the Nv region, the Ni region has few remaining pores, so that the oxygen precipitation reaction as described above is unlikely to proceed, and oxygen precipitation is unlikely to occur even when the device or the like is heat-treated.

With the progress of device technology in recent years, the characteristic difference between the Nv region and the Ni region is becoming a problem. Since the susceptibility to oxygen precipitation differs greatly between the Nv region and the Ni region, if a wafer in which the Nv region and the Ni region coexist is used, the difference in oxygen precipitation characteristics becomes apparent due to the thermal history of the device process, and the wafer warps or warps. It may cause device pattern deviation. From the above problems, in recent years, it has been desired to manufacture the product in either the Nv region or the Ni region with respect to the defect-free PW.
Therefore, as described above, in a silicon single crystal for manufacturing a silicon wafer, a method of detecting or guaranteeing each defect region is important.

As described above, it is known that Void, which is an aggregate of pores, and dislocation clusters, which are aggregates of interstitial silicon, can be detected by selective etching. Further, it is generally known that R-OSF can be detected as an etch pit by performing selective etching after oxidative heat treatment at a temperature of about 1150 ° C. and observing the surface.
Further, the Nv region and the Ni region can be distinguished by using the difference in oxygen precipitation characteristics between the two regions. Specifically, the Nv region and the Ni region can be distinguished by detecting the density of the oxygen precipitate by an infrared tomography method or the like after performing the oxygen precipitation heat treatment under an appropriate temperature condition.

However, regarding the method for detecting the B-band region, there is no method that can be used in an actual inspection step as a means for guaranteeing the defective region of the silicon single crystal. For example, as described in Patent Document 1, there is a method of intentionally applying an impurity metal to an inspection sample, diffusing it by heat treatment, and then etching the surface layer to detect shallow pits formed on the surface.
Most of the impurity metals remain on the surface of the Ni region because there are no sites for gettering the impurity metals. Since it contributes as a gettering site, the impurity metal diffuses into the bulk and the amount of metal remaining on the surface layer is reduced. Therefore, many shallow pits formed starting from the impurity metal are formed in the Ni region, and the shallow pit density decreases in the B-band region and the dislocation cluster formation region.
When observing a region with many shallow pits on the sample surface under a condensing lamp, the sample surface looks cloudy due to light scattering, and no cloudiness is seen in the region with few shallow pits. By observing under a condensing lamp and evaluating the presence or absence of white turbidity on the surface, it is possible to determine the presence or absence of a mixture of B-band region and dislocation cluster formation region in the sample.

However, if the B-band region and the dislocation cluster formation region are included in a large proportion of the wafer, the presence or absence of cloudiness can be easily seen and easily determined, but the B-band region and the dislocation cluster formation region are slightly included. If it is, it is difficult to see the presence or absence of cloudiness, and it is difficult to determine whether or not the B-band region and the dislocation cluster formation region are included. In addition, since the presence or absence of cloudiness is a subjective judgment of the observer, individual differences are likely to occur, and it is not possible to stably and reliably determine the presence or absence of a mixture of B-band regions and dislocation cluster formation regions.

Further, there is a method in which the dislocation cluster formation region is selectively etched as in Patent Document 2 and the presence or absence of the dislocation cluster formation region is evaluated based on the presence or absence of etch pits.
However, since the density of etch pits generated by dislocation clusters due to selective etching is low, it may be overlooked even when observed with an optical microscope. Furthermore, only large-sized dislocation clusters are etched by selective etching, and small-sized stacking defects and dislocations that do not reach dislocation loops cannot be detected as etch pits, so this method has sufficient sensitivity. It is hard to say that there is.

Further, when a silicon wafer is manufactured from a silicon single crystal, a specific off-angle of several minutes to several degrees is intentionally given from a specific plane orientation such as a (100) plane, a (110) plane, or a (111) plane. Wafers may be manufactured by intentionally tilting the surface from the surface.
In that case, the B-band region and the dislocation cluster formation region may have a completely concentric shape and are not distributed in the wafer plane, but may have a biased crescent-shaped distribution. In the case of such a crescent-shaped distribution, the measurement area becomes a wide area with the entire surface of the wafer by the method of etching and searching for pits as in Patent Document 2, and efficient inspection cannot be performed. Therefore, as a method for detecting the B-band region and the I-rich region, a method capable of collectively inspecting the entire surface of the wafer is required.

Patent Document 3 describes a method of evaluating a defect region with high sensitivity by heat-treating a silicon wafer to form a secondary defect, polishing the surface of the silicon wafer, and inspecting the silicon wafer with an LLS inspection apparatus. Since the entire surface of the wafer can be inspected collectively by this method, it is possible to inspect the B-band region and the dislocation cluster formation region distributed in a crescent shape as described above with high efficiency.
However, in the method of Patent Document 3, oxygen precipitates are grown by performing heat treatment, and the precipitates are detected by an LLS inspection apparatus, so that the detection sensitivity is greatly affected by the oxygen concentration of the sample. In addition, low oxygen crystals with an oxygen concentration of about 10 ppma (JEIDA) or less cannot be detected with high sensitivity or require a considerably long heat treatment, so that it cannot be said to be an efficient inspection method.

As described above, conventionally, there has been no method for inspecting a defect region of a silicon single crystal for easily and efficiently detecting a B-band region and a dislocation cluster formation region.

Japanese Unexamined Patent Publication No. 2012-148925 Japanese Unexamined Patent Publication No. 2014-093457 JP-A-2017-220587

The present invention has been made in view of the above problems, and is a defect region of a wafer in which a B-band region and a dislocation cluster formation region can be easily and efficiently detected and determined in a silicon single crystal wafer. An object of the present invention is to provide a determination method.

In order to achieve the above object, the present invention is a method for determining a defect region of a wafer produced by cutting out a silicon single crystal by the Czochralski method.
An impurity metal having a concentration of ^{1 × 10 11} to 1 × 10 ¹⁵ atoms / cm ² is applied to the surface of the wafer and diffused by heat treatment.
The surface layer of the wafer after the heat treatment is polished and removed by 0.5 μm or more to remove it.
Silicide defects due to the impurity metal on the surface of the polished wafer were measured with a particle counter.
Provided is a method for determining a defective region of a wafer, which comprises determining whether or not a B-band region or an I-rich region is included in the wafer based on the result of the measurement.

With such a determination method, the presence or absence of the B-band region and the I-rich region can be easily and efficiently determined, and the observer's subjectivity is different from the conventional determination method based on shallow pit detection. It is possible to prevent the judgment result from being influenced by the judgment.
By setting the coating concentration of the impurity metal to 1 × 10 ¹¹ atoms / cm ² or more, the above-mentioned silicide defect can be sufficiently formed as a material for determining the defect region, and 1 × 10 ¹⁵ atoms / cm ² By doing the following, it is possible to prevent the defects in the B-band region and the I-rich region from being completely captured, and to prevent the silicid defects from being formed even in the region where there are no defects.
Further, even if the impurity metal is diffused by heat treatment, most of it is precipitated on the surface. Therefore, by polishing 0.5 μm or more, the influence is eliminated and the impurity metal is formed in the B-band region or I-rich region in the bulk. The defect area of the wafer can be accurately determined by detecting the defect.

At this time, the impurity metal to be applied can be Cu or Ni.

Since Cu and Ni have a remarkable property of gathering in the B-band region and the I-rich region, the defect region can be determined more reliably.

Further, when the heat treatment is performed, the heat treatment temperature can be set to 500 ° C. or higher and the heat treatment time can be set to 5 minutes or longer.

Under such heat treatment conditions, the impurity metal can be diffused more sufficiently.

As described above, according to the method for determining the defect region of the wafer of the present invention, it is possible to easily and efficiently determine the presence or absence of the B-band region and the I-rich region, and the determination result is the observer. It can be prevented from being influenced by the subjective judgment of.

It is a flow chart which shows an example of the process of the method of determining a defect region of a wafer of this invention. It is the schematic which shows an example of the silicon single crystal production apparatus which can produce a silicon single crystal. It is a defect distribution diagram which shows the result of having measured the defect of 30 nm or more with the particle counter in Example 1. FIG. It is a defect distribution diagram which shows the result of having measured the defect of 30 nm or more with the particle counter in the comparative example 1. FIG. It is a defect distribution diagram which shows the result of having measured the defect of 30 nm or more with the particle counter in the comparative example 2. It is explanatory drawing which shows the relationship of the defect region in V / G and a silicon single crystal.

As mentioned above, there has been no effective method for easily and efficiently determining the B-band region and the I-rich region. Therefore, as a result of diligent research, the present inventors conducted coating of an impurity metal at a predetermined concentration, diffusion by heat treatment, polishing of 0.5 μm or more, and measurement of VDD defects with a particle counter, and based on the measurement results, B The present invention has been completed by finding that the presence or absence of a −band region or I-rich region can be easily and efficiently determined.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.
FIG. 1 shows an example of a process of a method for determining a defect region of a wafer of the present invention. As shown in FIG. 1, it is roughly divided into a process of preparing a wafer to be judged, coating an impurity metal, diffusing by heat treatment, polishing, measuring with a particle counter, and judging a defect region. Hereinafter, each step will be described in detail.
(Preparation of wafer to be judged)
First, a wafer (hereinafter, also referred to as a sample) to be determined for a defect region is prepared. This wafer is a silicon single crystal wafer, which is cut out from a silicon single crystal manufactured by the CZ method.
Here, a single crystal manufacturing apparatus by the CZ method and a method for manufacturing a silicon single crystal will be described. FIG. 2 is a schematic view showing an example of a single crystal manufacturing apparatus capable of manufacturing a silicon single crystal. The single crystal manufacturing apparatus 20 shown in FIG. 2 is a single crystal manufacturing apparatus that pulls a silicon single crystal from a silicon raw material melt (silicon melt) 4 by a CZ method. In the main chamber 1 of the single crystal manufacturing apparatus 20, a quartz crucible 5 containing the molten silicon raw material melt 4 and a graphite crucible 6 containing the quartz crucible 5 are provided, and these crucibles 5 and 6 are driven. It is supported by a mechanism (not shown) so that it can rotate, move up and down.

Further, a pulling chamber 2 for accommodating the silicon single crystal 14 pulled up from the silicon raw material melt 4 and taking it out to the outside is connected to the upper part of the main chamber 1, and the silicon single crystal 14 is placed on the upper part of the seed crystal. A pulling mechanism (not shown) for pulling up from the silicon raw material melt 4 via the seed crystal 3 held by the holder is provided. In the driving mechanism of the crucibles 5 and 6 (not shown), the crucibles 5 and 6 are rotated when the silicon single crystal 14 is pulled up, and at the same time, the melt surface of the silicon raw material melt 4 is raised as the silicon single crystal 14 is pulled up. The crucibles 5 and 6 are set to be raised so as to correct the decrease and keep the melt surface of the silicon raw material melt 4 at a substantially constant position during single crystal growth.

A heating heater (graphite heater) 7 for melting the silicon raw material melt 4 is arranged around the crucibles 5 and 6 so as to surround the crucibles 5 and 6, and further, heating is performed around the outside of the heating heater 7. A heat insulating material 8 is arranged to prevent the radiant heat from the heater 7 from being radiated directly to the main chamber 1.
Further, inside the main chamber 1, an inert gas such as argon gas (Ar) is introduced from the gas introduction port 10 provided in the upper part of the pull-up chamber 2, and the gas rectifying cylinder 12 provided in the top chamber 11 It passes between the silicon single crystal 14 being pulled up, passes between the heat shield member 13 and the melt surface arranged so as to face the melt surface of the silicon raw material melt 4, and passes through the side wall of the graphite rubbing pot 6. Flows downward from the main chamber 1 and is discharged to the outside from the gas outlet 9 at the lower end of the main chamber 1. The heat shielding member 13 prevents the radiant heat from the silicon raw material melt 4 from being radiated to the upper part of the main chamber 1, facilitating the formation of a desired crystal cooling atmosphere, and inactive flowing along the melt surface. It has the role of rectifying the gas.

Then, in producing the silicon single crystal 14 using such a single crystal production apparatus 20, the silicon raw material melt 4 is heated by the heating heater 7, and argon gas is introduced from the gas introduction port 10 while being introduced. The seed crystal 3 held by the seed crystal holder is landed, and the silicon single crystal 14 is pulled up while rotating the ruts 5 and 6. Then, it can be cut out into a wafer shape with a wire saw or the like to obtain a wafer to be determined.

(Applying impurity metal and diffusing by heat treatment)
Impurity metal is applied to the wafer prepared as described above, and further heat treatment is performed to diffuse the impurity metal.
Here, first, the reason why the impurity metal is applied to the wafer and diffused will be described. Impurity metals are trapped around gettering sites in the silicon single crystal if they are present. When a B-band region or a dislocation cluster formation region is included in a silicon single crystal, small-sized stacking defects existing in the B-band region or dislocation or dislocation agglomerates existing in the dislocation cluster formation region serve as gettering sites. Impurity metals are intensively trapped around those defects to contribute. On the other hand, if there are no defects in the silicon single crystal, there will be no gettering sites, so the impurity metal will not be trapped intensively at a specific site.
That is, when the impurity metal is intentionally applied and diffused, if the sample contains a B-band region or a dislocation cluster forming region, the impurity metal is diffused to selectively collect the impurity metal in those defect regions. Can be done. Further, since Cu and Ni are remarkable in the property of gathering in the B-band region and the dislocation cluster forming region, it is preferable to select Cu or Ni as the impurity metal to be applied, but the present invention is not limited thereto.

When the impurity metal is intensively trapped in the B-band region or the dislocation cluster formation region as described above, the impurity metal is locally supersaturated around the gettering site. Therefore, in order to eliminate supersaturation, the impurity metal and silicon are composited and precipitated as silicide. That is, by applying the impurity metal and diffusing it, the silicide can be selectively formed in the B-band region and the dislocation cluster forming region.

When applying impurity metals, it is necessary to pay attention to the concentration. If the concentration to be applied is too low, the concentration of impurity metals sufficient to form silicide in the B-band region and dislocation cluster formation region will not be reached, so the contamination concentration must be 1 × 10 ¹¹ atoms / cm ² or more. There is. Further, if the contamination concentration is too high, it cannot be completely captured by defects in the B-band region and the dislocation cluster formation region, and silicide may be formed even in the region without defects. Therefore, the upper limit of the contamination concentration is 1 × 10. ^It should be 15 atoms / cm ² or less.

After applying the impurity metal, it is necessary to diffuse it by heat treatment. For example, Cu and Ni have a relatively high diffusion rate in a silicon single crystal, so that they can be easily diffused by a short heat treatment. If the heat treatment temperature is 500 ° C. or higher and 1000 ° C. or lower, and the heat treatment time is 5 minutes or longer, more preferably 10 minutes or longer and 60 minutes or lower, impurity metals such as Cu and Ni can be sufficiently diffused, and time efficiency is considered to be good. ..

(Polishing)
After diffusing the impurity metal as described above, the surface layer of the wafer is polished and removed.
First, the reason for performing such polishing will be described. Even if the impurity metal is diffused by heat treatment, most of it is deposited on the surface. That is, when a large amount of metal is deposited on the surface layer, it is difficult to see the difference in metal gettering ability depending on the defect region distributed on the wafer. However, by removing the surface layer of the wafer by a physical method such as polishing without impairing the flatness, it is possible to analyze the surface of a portion that was bulk during the heat treatment.

At this time, polishing needs to be performed by 0.5 μm or more. Further, it is preferably performed at 5 μm or less. By polishing 0.5 μm or more, the influence of silicide of impurity metals such as Ni deposited on the surface can be completely eliminated, and the bulk state can be surface-analyzed. Therefore, the B-band region and dislocation cluster formation region in the bulk can be analyzed. It will be possible to detect VDD defects formed due to the metal gettered on the surface. Further, since the defect distribution is uniform when polishing 0.5 μm or more, the polishing removal allowance is preferably 5 μm or less from the viewpoint of time efficiency.

(Measurement by particle counter)
Next, the above-mentioned VDD defect on the surface of the wafer after polishing is measured.
A particle canter is used to detect silicide defects. If it is a particle counter, it is possible to detect defects caused by VDD formed by metal impurities with high sensitivity and high efficiency. Assuming that all the defects that can be normally measured by the particle counter are defects caused by VDD, the amount of defects directly becomes the superiority or inferiority of the gettering ability, and high-precision evaluation becomes possible.

(Judgment of defective area)
Based on the result of the above measurement, it is determined whether or not the wafer contains a B-band region or an I-rich region. This makes it possible to confirm the presence or absence of these defect regions in the wafer and the silicon single crystal that is the source of the wafer.
More specifically, for example, the presence or absence of these defect regions can be determined from the measured distribution of VDD defects in the wafer surface (particularly, a dense distribution). When a wafer is produced by cutting out a silicon single crystal without inclination and a B-band region or a dislocation cluster formation region exists in the wafer surface, the distribution is concentric or simple with no center. .. Alternatively, in a wafer produced by cutting out a silicon single crystal with an inclination, if a B-band region or a dislocation cluster forming region exists in the wafer surface, the shape is inclined to a crescent shape or an ellipse due to an off-angle or the like. It is distributed in a shape. That is, if the distribution of defects detected by the particle counter is as described above, it can be determined that the B-band region and the dislocation cluster formation region are mixed.

The above-mentioned determination method of the present invention is easier than the conventional determination method using shallow pits, which is difficult to determine, and it is not necessary for the operator to visually and subjectively determine the defect distribution. , There is no deviation in detection sensitivity due to individual differences. Further, as described above, since the ferrite made of the impurity metal is formed not only in the dislocation cluster forming region but also in the B-band region, the sensitivity for detecting not only the dislocation cluster region but also the B-band region is sufficient. Therefore, with this method, it is possible to evaluate the entire wafer area easily, with high sensitivity, and efficiently, and it can be used as a means for guaranteeing the defect region of the defect-free PW. In particular, it can be useful for determining whether the entire surface is a defect-free Ni region, or includes a B-band region or a dislocation cluster formation region.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited thereto.

(Example 1)
Using the single crystal manufacturing apparatus shown in FIG. 2, a quartz crucible having a diameter of 32 inches (800 mm) and a silicon single crystal having a diameter of 305 mm and a straight body length of 140 cm were pulled up with an initial charge amount of 380 kg. A silicon wafer having a diameter of 300 mm and a thickness of 0.775 mm was produced from the raised crystals. When cutting out the wafer, it was performed without tilting. One of them was taken out as an inspection sample.
Ni was applied to the test sample at ^{a concentration of 1 × 10 12} atoms / cm ² and diffused by heat treatment at 700 ° C. × 20 min. After that, the surface layer was polished by 1 μm, and defects (filaicide defects) existing on the surface were measured by a particle counter (SurfScan series manufactured by KLA, SP3).

A particle counter measures defects of 30 nm or more, and FIG. 3 shows a map of the detected defects. As shown in FIG. 3, defects densely packed concentrically were detected.
Therefore, it was judged that this sample contained a B-band region and a dislocation cluster formation region, and it was judged to be unacceptable as a defect-free PW.

As a verification, when selective etching was performed on silicon wafers of the same level and microscopic observation was performed, pits thought to be caused by dislocation clusters were detected. That is, since the B-band region and the dislocation cluster formation region are mixed in this wafer, it can be said that the judgment result from the measurement with the particle counter was correct.

(Comparative Example 1)
A silicon single crystal having the same diameter was produced using the same single crystal production apparatus as in Example 1. An inspection sample was extracted from the silicon single crystal in the same manner as in Example 1. That is, a test sample similar to that of Example 1 (that is, the same as that in Example 1 in which it has already been confirmed that the B-band region and the dislocation cluster formation region exist concentrically) was prepared. ..
Ni was applied to the test sample at ^{a concentration of 1 × 10 10} atoms / cm ² and diffused by heat treatment at 700 ° C. × 20 min. After that, the surface layer was polished by 1 μm, and defects were measured by a particle counter.

FIG. 4 shows a map of defects detected by measuring defects of 30 nm or more with a particle counter. Since the distribution of dense defects was not confirmed as shown in FIG. 4, it was judged that the B-band region and the dislocation cluster formation region were not mixed, and it was judged that the defect-free PW was acceptable.

However, when selective etching was performed on silicon wafers of the same level and microscopic observation was performed, pits thought to be caused by dislocation clusters were detected. That is, since the B-band region and the dislocation cluster formation region are mixed in this wafer, it can be said that the determination result from the measurement with the particle counter was not correct.
It is considered that this is because the Ni contamination concentration was ^{as low as 1 × 10 10} atoms / cm ^2, and it was not possible to get Ni in the B-band region and the dislocation cluster formation region to form Ni silicide.

(Comparative Example 2)
A silicon single crystal having the same diameter was produced using the same single crystal production apparatus as in Example 1. An inspection sample was prepared from the silicon single crystal, and an inspection sample different from that of Example 1 was prepared. Ni was applied to the test sample at ^{a concentration of 1 × 10 12} atoms / cm ² and diffused by heat treatment at 500 ° C. × 10 min. After that, the surface layer was polished by 0.1 μm, and defect measurement was carried out with a particle counter.

FIG. 5 shows a map of defects detected by measuring defects of 30 nm or more with a particle counter. Since defects were observed on the entire surface of the wafer, it was judged that the B-band region and the dislocation cluster formation region were mixed, and it was judged that the defect-free PW was unacceptable.

However, for verification, when selective etching was performed on silicon wafers of the same level and microscopic observation was performed, pits thought to be caused by dislocation clusters were not detected. That is, since the B-band region and the dislocation cluster formation region are not mixed in this wafer, it can be said that the above determination result is not correct. That is, it is considered that this wafer was a pass product as a defect-free PW.
As yet another verification, when the same sample polished by 0.1 μm was additionally polished by 1 μm (that is, the total polishing amount was 1.1 μm) and then the particle counter measurement was performed again, dense defects were found. Was not observed, and it was determined that the PW was defect-free in which the B-band region and the like were not mixed, as in the verification by the above selective etching.
This is because the amount of polishing in Comparative Example 2 was as small as 0.1 μm, so that many defects due to Ni silicide remaining on the wafer surface layer were detected, and the Ni silicide formation behavior due to the defect region could not be observed. it is conceivable that. On the other hand, when the total polishing amount of the polishing in Comparative Example 2 and the additional polishing performed in the verification is 1.1 μm (corresponding to the determination method of the present invention), the Ni silicide formation behavior caused by the defect region is correctly captured. It can be said that it was possible.

(Example 2)
To the same test sample as in Example 1 (ie, the same as in Example 1 and subsequent verifications that have already confirmed the presence of concentric B-band regions and dislocation cluster formation regions). On the other hand, defect measurement was carried out in the same manner as in Example 1 except that the coating concentration of Ni was 1 × 10 ¹¹ atoms / cm ^{2 and the polishing amount was 0.5 μm.}

As a result, the defect distribution (concentric distribution) similar to that in FIG. 3 is obtained, and it is judged that the B-band region and the dislocation cluster formation region are mixed as in Example 1, and the defect-free PW is not suitable. It was judged to have passed.
As described above, it has been confirmed in Example 1 and the subsequent verification that the B-band region and the like are mixed, and it can be seen that the evaluation can be performed correctly.

(Example 3)
To the same test sample as in Example 1 (ie, the same as in Example 1 and subsequent verifications that have already confirmed the presence of concentric B-band regions and dislocation cluster formation regions). On the other hand, defect measurement was carried out in the same manner as in Example 1 except that the coating concentration of Ni was 1 × 10 ¹⁵ atoms / cm ^{2 and the polishing amount was 0.5 μm.}

As a result, the defect distribution (concentric distribution) similar to that in FIG. 3 is obtained, and it is judged that the B-band region and the dislocation cluster formation region are mixed as in Example 1, and the defect-free PW is not suitable. It was judged to have passed.
As described above, it has been confirmed in Example 1 and the subsequent verification that the B-band region and the like are mixed, and it can be seen that the evaluation can be performed correctly.

(Comparative Example 3)
For the same inspection sample as in Comparative Example 2 (that is, the same as the one that has already been confirmed to be defect-free PW by the verification after Comparative Example 2), the coating concentration of Ni was 1 × 10 ¹⁶ Defect measurement was carried out in the same manner as in Comparative Example 2 except that the atoms / cm ^{2 was set and the polishing amount was 0.5 μm.}

As a result, the defect distribution (distributed over the entire surface) is the same as in FIG. 5, and it is judged that the B-band region and the dislocation cluster formation region are mixed as in Comparative Example 2, and the defect-free PW is rejected. Was judged.
However, as described above, in the verification after Comparative Example 2, it has been confirmed that the PW is a defect-free PW in which the B-band region and the like are not mixed, and it can be seen that the evaluation cannot be performed correctly.

The present invention is not limited to the above embodiment. The above embodiment is an example, and any one having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect and effect is the present invention. It is included in the technical scope of the invention.

1 ... Main chamber, 2 ... Pulling chamber, 3 ... Seed crystal,
4 ... Silicon raw material melt, 5 ... Quartz crucible, 6 ... Graphite crucible,
7 ... Heater, 8 ... Insulation material, 9 ... Gas outlet, 10 ... Gas inlet,
11 ... Top chamber, 12 ... Gas rectifier cylinder, 13 ... Heat shielding member,
14 ... Silicon single crystal, 20 ... Single crystal manufacturing equipment.

Claims (3)

It is a method for determining the defect region of a wafer produced by cutting out from a silicon single crystal by the Czochralski method.
An impurity metal having a concentration of ^{1 × 10 11} to 1 × 10 ¹⁵ atoms / cm ² is applied to the surface of the wafer and diffused by heat treatment.
The surface layer of the wafer after the heat treatment is polished and removed by 0.5 μm or more to remove it.
Silicide defects due to the impurity metal on the surface of the polished wafer were measured with a particle counter.
A method for determining a defect region of a wafer, which determines whether or not a B-band region or an I-rich region is included in the wafer based on the result of the measurement. The method for determining a defective region of a wafer according to claim 1, wherein the impurity metal to be applied is Cu or Ni. The method for determining a defective region of a wafer according to claim 1 or 2, wherein when the heat treatment is performed, the heat treatment temperature is set to 500 ° C. or higher and the heat treatment time is set to 5 minutes or longer.

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