JP6244833B2 - Determination method of absolute value of atomic vacancy concentration in silicon wafer - Google Patents

Description

  The present invention relates to a method for determining an absolute value of atomic vacancy concentration in a silicon wafer.

  In recent years, semiconductor elements (LSI: Large Scale Integration) typified by DRAM and flash memory have become more multifunctional and higher quality with the advancement of communication equipment, etc., and mobile phones and portable music players have become popular. As a result, demand is increasing rapidly. Correspondingly, the demand for silicon wafers, which are materials for semiconductor elements, has been increasing rapidly, and it is possible to efficiently produce high-quality silicon wafers to meet the demand that is expected to increase in the future. Technology that can be done is required.

  Incidentally, in the semiconductor industry, silicon wafers are generally manufactured by the Czochralski method (CZ method) or the float zone (FZ method). The silicon wafer formed by these methods contains lattice defects at a certain rate. This lattice defect is a point defect mainly composed of an atomic vacancy from which one silicon atom in the lattice is removed and an interstitial atom having a silicon atom in an irregular position of the lattice. In particular, when atomic vacancies that are point defects gather to form voids that are secondary defects, the electrical characteristics and yield of devices manufactured using silicon wafers are adversely affected. Therefore, in the manufacture of so-called high-end devices used in communication equipment as described above, processed annealed wafers, epitaxial wafers, and fully crystalline silicon wafers that suppress the growth of voids as secondary defects are used. It has been broken.

  However, in the annealed wafer, the substrate wafer is annealed in order to remove surface layer defects. In addition, the epitaxial wafer is an epitaxial layer in which the impurity concentration and thickness are precisely controlled on the wafer. In other words, in both annealed wafers and epitaxial wafers, it is necessary to perform secondary processing on silicon wafers cut out from silicon ingots, which increases the number of man-hours required for production of silicon wafers efficiently. Have difficulty. In addition, in the annealed wafer and the epitaxial wafer, there is a problem that it is difficult to perform the secondary processing described above on a large-diameter wafer.

  For these reasons, in recent years, a completely crystalline silicon wafer in which the growth of voids as secondary defects is suppressed and only atomic vacancies and interstitial atoms as point defects have been put into practical use. However, even in this complete crystal silicon wafer, in order to improve the electrical characteristics and yield of the device, it is necessary to determine the region of the atomic vacancy rich portion and the region of the interstitial atom rich portion in the crystal ingot. is there. Furthermore, it is necessary to evaluate the distribution of atomic vacancy concentration in advance in the region of one atomic vacancy-rich portion prior to device fabrication.

  Therefore, the development of a growth technique for high-quality CZ silicon crystal ingots with controlled point defects requires quantitative evaluation of atomic vacancy concentration by ultrasonic measurement. Characteristic control in device manufacturing using a complete crystal silicon wafer is possible by preliminarily evaluating the existence concentration of atomic vacancies in a complete crystal silicon wafer manufactured by slicing the CZ silicon crystal ingot by ultrasonic measurement. This is expected to make a significant contribution to yield improvement.

  One of the present inventors has proposed an atomic vacancy analyzer using ultrasonic measurement so far (Patent Document 1). In this atomic vacancy analyzer, an external magnetic field is applied to a silicon sample, ultrasonic waves are passed through the crystal sample while cooling, and a curve showing the relationship between the ultrasonic sound velocity change in the silicon sample and the cooling temperature of the silicon sample The atomic vacancy defect concentration is obtained on the basis of the sharp drop amount.

  By the way, in the semiconductor industry, there is a strong demand to measure the absolute value of the atomic vacancy concentration inside the silicon wafer and in the surface layer. Until now, the method for determining the atomic vacancy concentration by measuring the sonic drop at low temperature by ultrasonic waves can determine the relative distribution of the atomic vacancy concentration of the silicon wafer. However, a quantitative proportional relationship between the low-temperature change in sound velocity in silicon and the atomic vacancy concentration has not been established, and a technique for measuring the absolute value of the atomic vacancy concentration has not been known so far.

Japanese Patent Laid-Open No. 7-174742

  In view of the above problems, an object of the present invention is to provide a new method for determining the absolute value of atomic vacancy concentration in a silicon wafer.

The present inventors have developed a means for determining the absolute value of the atomic vacancy concentration from the amount of softening at low temperature. The evaluation of the atomic vacancy concentration in a boron-added CZ silicon ingot having a diameter of 300 mm used in the semiconductor industry was advanced using ultrasonic measurement. The amount of softening of the elastic constant C ₄₄ by lowering the temperature from 5 K to 20 mK is markedly dependent on the location in the ingot, demonstrating that the atomic vacancy concentration in the ingot is distributed. On the other hand, the density and size of voids were measured by infrared scattering. Focusing on the sum rule of the amount of atomic vacancies consumed for void formation and the atomic vacancies remaining in the wafer, per quadruple degenerate ground state orbital called Γ ₈ We found that the magnitude of the bond between the electric quadrupole and the strain ε _zx is: However, experimental errors were taken into account. Based on this knowledge, the inventors have conceived the present invention.

That is, the method for determining the absolute value of the atomic vacancy concentration in the silicon wafer of the present invention was measured in the measurement step of measuring the low temperature softening amount ΔC ₄₄ / C ₄₄ of the elastic constant of the silicon sample, and this measurement step. And a determination step of determining an absolute value of the atomic vacancy concentration N in the silicon wafer based on the low-temperature softening amount ΔC ₄₄ / C ₄₄ .

In the determination step, the atomic vacancy concentration N = (1.5 ± 0.2) × 10 ¹³ cm ⁻³ corresponds to the low-temperature softening amount ΔC ₄₄ / C ₄₄ = 1 × 10 ⁻⁴ . it you wherein determining the atomic vacancy concentration N based on that.

In addition, the measuring step is performed at a temperature of 20 mK to 20K .

Method for producing a silicon wafer of the present invention includes a measuring step of measuring the low-temperature softening amount ΔC _{44 /} C ₄₄ of the elastic constant of silicon sample, the low-temperature softening amount ΔC _{44 /} C ₄₄ measured in this measuring step And a determining step for determining an absolute value of the atomic vacancy concentration N in the silicon wafer .

An apparatus for determining an absolute value of atomic vacancy concentration in a silicon wafer according to the present invention includes a silicon sample in which an ultrasonic oscillator and an ultrasonic receiver are formed, and magnetic force generating means for applying an external magnetic field to the silicon sample. Detecting a phase difference between a cooling means for cooling the silicon sample, an ultrasonic pulse oscillated from the ultrasonic oscillator, and an ultrasonic pulse propagated through the silicon sample and received by the ultrasonic receiver Detecting means for calculating the elastic constant C ₄₄ of the silicon sample based on the phase difference, and low-temperature softening amount ΔC ₄₄ / C ₄₄ = 1 × 10 ^{−4 of the} elastic constant. And determining means for determining the atomic vacancy concentration N based on the fact that the concentration N = (1.5 ± 0.2) × 10 ¹³ cm ⁻³ .

  According to the method for determining the absolute value of the atomic vacancy concentration in the silicon wafer of the present invention, the absolute value of the atomic vacancy concentration in the silicon wafer can be determined, and the absolute value of the atomic vacancy concentration in the silicon wafer. It is possible to provide a silicon wafer displaying the above.

It is the schematic which shows one Embodiment of the measuring apparatus used for the determination method of the absolute value of the atomic vacancy concentration in the silicon wafer of this invention. It is an enlarged view of the sample holder part which set the silicon sample same as the above. It is sectional drawing which shows typically the structure of a silicon sample same as the above. It is a block diagram which shows the structure of a detection means same as the above. (A) which is sectional drawing of a silicon sample, and the bar graph (b) which shows the magnitude | size of low temperature softening. It is a graph which shows low temperature softening of each site | part shown in FIG. It is a graph which shows that the sum total of the amount of atomic vacancies consumed for void formation and the amount of atomic vacancies remaining on the wafer is the amount of atomic vacancies generated during crystal growth (sum rule). It is a graph showing that the low-temperature softening of elastic constant is proportional to the square of the product Ng ² atomic vacancy N and coupling constant g remaining in the wafer. Depending on Ng ² obtained from softening at low temperature and the amount of atomic vacancies remaining in the wafer estimated from the sum rule, the coupling constant g = 2.6-3.0 × It is a graph which shows that 10 < ⁵ > K is obtained.

In the present invention, the coupling constant between the atomic vacancy orbit newly found by the present inventors and the strain ε _zx of the transverse ultrasonic wave C ₄₄ is g = (2.8 ± 0.2) × 10 ⁵ K. Based on knowledge. The present invention makes it possible to determine the absolute value of the atomic vacancy concentration based on this finding.

  In the present invention, the term “absolute value” refers to a numerical value determined absolutely, and is used to distinguish it from a relatively determined numerical value.

  Hereinafter, the determination method of the absolute value of the atomic vacancy concentration in the silicon wafer of the present invention will be described in detail based on examples.

[measuring device]
An example of the configuration of a measuring apparatus used in the method for determining the absolute value of the atomic vacancy concentration in the silicon wafer of this embodiment will be described.

  In FIG. 1 showing the measurement apparatus of the present embodiment, the apparatus 1 includes a sample holder portion 2, a dilution refrigerator 3 as a cooling means, a magnetic force generation means 4, and a detection coaxial line 5 as detection means. As a whole, the apparatus 1 cools the silicon sample 6 to a predetermined temperature in a state where an external magnetic field is applied to the silicon sample 6 installed in the sample holder unit 2, and the sound velocity of the ultrasonic pulse propagated through the silicon sample 6. Is configured to be detectable.

  The magnetic force generating means 4 is arranged so as to surround a position where the silicon sample 6 is set in order to apply an external magnetic field to the silicon sample 6. As the magnetic force generation means 4, for example, a superconducting magnet can be used. Further, in order to detect the sound velocity of the ultrasonic pulse propagated through the silicon sample 6 with an external magnetic field applied to the silicon sample 6 as necessary, the magnetic force generating means 4 is at least in the range of 0 to 10 Tesla. It is configured to be controllable.

The dilution refrigerator 3 cools the silicon sample 6 installed in the sample holder 2 and is configured to be controllable in a range of at least 20 mK to 20K. In the present embodiment, the dilution refrigerator 3 includes two systems, a ³ He- ⁴ He mixed gas system 10 and a ⁴ He system 11, and is configured so that the inside of the dewar 12 can be cooled to a predetermined temperature. The dewar 12 has a double structure of an inner layer 12a and an outer layer 12b, and a vacuum space 12c is formed between the inner layer 12a and the outer layer 12b. In the dewar 12, liquid ⁴ He is stored.

^{The 3} He system 10 is configured to obtain a cooling capacity as the dilution refrigerator 3. The ³ He- ⁴ He mixed gas system 10 includes a storage tank 14, a circulation pump 15, a condenser 16, a mixer 17, and a fractionator 18. Unlike a normal pump, the circulation pump 15 has a structure in which ³ He does not escape to the outside air. The condenser 16 cools the ³ He gas sent out from the circulation pump 15 and separates it into a ³ He rich phase and a ³ He dilute phase.

The mixer 17 is a portion having the lowest temperature in the dilution refrigerator 3. In the mixer 17, there is an interface of phase-separated ³ He- ⁴ He mixed liquid. The upper half of the mixer 17 is a ³ He rich phase and is constantly supplied from the capacitor 16. In addition, the lower half of the mixer 17 is a ³ He dilute phase (concentration of about 6%, and the remaining is superfluid ⁴ He), which is connected to the fractionator 18. In this mixer 17, ³ He is forcibly moved from a concentrated phase having a large entropy to a diluted phase having little entropy, and the cooling capacity of the dilution refrigerator 3 is generated by the entropy difference generated at this time. It has become.

The fractionator 18 is configured to selectively evaporate only ³ He in the lean phase. The fractionator 18 is maintained at a predetermined temperature (for example, 0.8 K or less). As a result, the fractionator 18 evaporates only ³ He by utilizing the phenomenon that the vapor pressure of ³ He is kept finite while the vapor pressure of ⁴ He is 0. .

^{The 4} He system 11 is configured to be capable of liquefying ³ He gas. This ⁴ He system includes a 1K pot 20 having an exhaust pump. In this ⁴ He system 11, the cooling capacity is obtained by exhausting ⁴ He in the 1K pot 20 with an exhaust pump. In the present embodiment, a 4.2K ⁴ He liquid is directly taken from the dewar 12 through the capacitor 16 so that continuous operation is possible, and the ³ He gas is liquefied in the capacitor 16. Yes.

FIG. 1 shows a configuration in which the sample holder 2 to which the silicon sample 6 is set is phase-separated into a ³ He rich phase and a ³ He dilute phase in the mixer 17. In this embodiment, the member forming the cooled mixer 17 is made of a material having a high thermal conductivity, and the silicon sample 6 is cooled indirectly using the heat conduction from the member forming the mixer 17. ing. Such a configuration is particularly advantageous in that the temperature range for cooling can be expanded to the high temperature side.

  The detection coaxial line 5 oscillates an ultrasonic pulse with respect to the surface of the silicon wafer, receives an ultrasonic pulse in which the oscillated ultrasonic pulse is propagated in the silicon wafer, and receives the ultrasonic pulse propagated in the silicon wafer. The sound velocity can be detected.

  As shown in FIG. 2, the sample holder portion 2 is composed of a pair of pins 25 urged in the axial direction by a coil spring 24. The sample holder 2 configured in this way holds the silicon sample 6 with the silicon sample 6 sandwiched between a pair of pins 25.

  The silicon sample 6 includes a silicon wafer 26, an ultrasonic oscillation unit 27 provided on one surface of the silicon wafer 26, and an ultrasonic reception unit 28 provided on the other surface. The ultrasonic oscillator 27 and the ultrasonic receiver 28 include a transducer 30.

As shown in FIG. 3, the transducer 30 includes a thin film vibrator 31 formed in a film shape, and an internal electrode 32 and an external electrode 33 as electrodes for applying an electric field to the thin film vibrator 31. The thin film vibrator 31 can be made of a known material such as LiNbO ₃ , ZnO, PVDF (polyvinylidene fluoride).

  Next, the configuration and operation of the detection coaxial line 5 will be described with reference to FIG. The detection coaxial line 5 is configured to detect a phase difference between the reference signal obtained by directly measuring the basic signal of the ultrasonic pulse applied to the silicon sample 6 and the measurement signal of the ultrasonic pulse propagated through the silicon sample 6. Has been. In this embodiment, the detection coaxial line 5 includes a standard signal generator 35, a frequency counter 36, a personal computer 37, a diode switch 38, a pulse generator 39, a phase shifter 40, and a phase detector 41.

  The standard signal generator 35 generates a basic signal. This basic signal is branched into a reference signal system 5a and a measurement signal system 5b. The frequency counter 36 measures the basic signal and outputs the result to the personal computer 37.

  The reference signal system 5a is connected to the phase detector 41 via the phase shifter 40. On the other hand, in the measurement signal system 5b, the diode switch 38 to which the pulse generator 39 is connected and the silicon sample 6 are arranged in this order, and are connected to the phase detector 41. The diode switch 38 divides the basic signal into a predetermined width.

  The phase detector 41 compares the reference signal based on the basic signal and the measurement signal output from the silicon sample 6 to detect the sound speed of the ultrasonic pulse in the silicon wafer 26.

  It is more preferable that the detection coaxial line 5 has means for performing zero detection by changing the oscillation frequency so that the phase difference caused by the change in sound speed due to temperature or magnetic field becomes constant. Further, it is preferable that a plurality of silicon samples 6 and a plurality of points of one silicon sample 6 are configured so that the phase difference can be measured simultaneously.

[Determination of coupling constant between atomic vacancy orbit and strain ε _zx of transverse wave ultrasonic wave C ₄₄ ]
Next, determination of the coupling constant between the atomic vacancy orbit and the distortion ε _zx of the transverse wave ultrasonic wave C ₄₄ will be described.

Focusing on the silicon wafer cut out from the void region grown by controlling the pulling conditions of the CZ silicon ingot, the amount of voids in the wafer is measured by a light scattering method using laser light, and the elastic constant of the wafer is low-temperature soft The amount of crystallization was measured with ultrasound. Here, the low temperature softening means that the elastic constant _C44 is remarkably reduced in proportion to the reciprocal of the temperature, which is seen when the change of the elastic constant with respect to the cooling temperature when the silicon wafer is cooled to a low temperature range is measured. A phenomenon. The softening at low temperature can be measured by using the above measuring device. Further, it is known that the amount of softening at low temperature is proportional to the amount of residual atomic vacancies.

  FIG. 5 shows a cross section of the silicon sample used for the measurement, and FIG. 6 shows low-temperature softening of each part shown in FIG.

As a result, as shown in FIG. 7, particularly in the central portion of the silicon wafer where the amount of atomic vacancies is constant, the amount of atomic vacancies contributing to void formation and the amount of low-temperature softening (ΔC ₄₄ / C ₄₄ ( It was found that there was a correlation with × 10 ⁻⁵ )). This indicates that the total conservation law of the residual vacancy concentration of silicon wafer (Residual vacancy concentration) and the amount of atomic vacancies (Consumed vacancy) contributing to void formation is established.

  The difference in the amount of residual vacancies appears because the same amount of vacancies are formed during crystal growth, but the amount of vacancies consumed for void formation during pull-up cooling differs depending on the pull-up speed, etc. It is thought that it is due to coming. Further, since the amount of atomic vacancies taken in at the outer periphery of the silicon wafer is larger than that at the center, it is considered that there is no correlation between the amount of voids and the amount of softening at low temperature.

  For this reason, the amount of atomic vacancies consumed for void formation can be estimated from the size of the void and its concentration.

Also, referring to FIG. 7, as described above, since the total conservation law of the amount of residual atomic vacancies in the silicon wafer and the amount of atomic vacancies contributing to void formation is established, a silicon sample of 0 mm from the center of the wafer in block D is obtained. The residual atomic vacancy concentration is estimated to be N = 3.5 to 4.0 × 10 ¹² / cm ³ . The measured value of the low temperature softening amount of this silicon sample is ΔC ₄₄ / C ₄₄ = 3.5 × 10 ⁻⁵ , and since the residual atomic vacancy concentration and the low temperature softening amount are proportional, ΔC ₄₄ / The low temperature softening amount of C ₄₄ = 1 × 10 ⁻⁴ corresponds to the residual atomic vacancy concentration N = (1.5 ± 0.2) × 10 ¹³ / cm ³ .

On the other hand, by fitting the temperature _{-C 44} curves in FIG. 8, block A0 in ^{Ng 2 = 2.4 × 10 23 K} 2 / cm 3, the ^{Ng 2 = 4 × 10 23 K} 2 / cm 3 in block D0. FIG. 9 shows the relationship of Ng ² = 2.4 × 10 ²³ K ² / cm ³ in the block A3 and the relationship of Ng ² = 4 × 10 ²³ K ² / cm ^{3 in} the block D0.

Thus, the binding constant of the binding Hamiltonian H = gOε _zx the strain epsilon _xy vacancy orbital and transverse ultrasonic waves _{C 44} was determined to g = (2.8 ± 0.2) × 10 5 K.

[Method for determining absolute value of atomic vacancy concentration in silicon wafer]
Next, a method for determining the absolute value of the atomic vacancy concentration in the silicon wafer of this embodiment will be described.

  First, an external magnetic field is applied as necessary to the silicon sample 6 in which the ultrasonic oscillator 27 and the ultrasonic receiver 28 are formed on the surface of the silicon wafer 26 obtained by cutting out a predetermined portion from the silicon ingot. Then, it is cooled to a temperature range of 20K or less.

  Next, the standard signal generator 35 oscillates the basic signal. This basic signal is branched into a reference signal system 5a and a measurement signal system 5b. The basic signal of the measurement signal system 5b is divided by the diode switch 38 into a width of 0.5 μs, for example.

  In the transducer 30, an alternating electric field as an electric field is applied between the external electrode 33 and the internal electrode 32 by the basic signal divided by the diode switch 38. Due to this AC electric field, the thin-film vibrator 31 induces elastic strain, whereby the ultrasonic oscillator 27 generates an ultrasonic pulse based on the basic signal. In this way, the basic signal is converted into a mechanical signal, that is, an ultrasonic pulse by the transducer 30 of the ultrasonic oscillator 27.

  The ultrasonic pulse propagates from one end of the silicon wafer 26 to the other end. The ultrasonic pulse propagating through the silicon wafer 26 is repeatedly reflected at one end and the other end of the silicon wafer 26, received as a measurement wave pulse by the transducer 30 of the ultrasonic receiver 28, and converted into an electrical signal again to be a measurement signal. Is output as

This measurement signal and the reference signal is compared in phase detector 41 measures the phase difference phi _n between the ultrasonic pulse and the measuring wave pulse. Using this phase difference φ _n , the speed of sound v is calculated from Equation 1: φ _n = 2π (2n−1) lf / v. Here, (2n-1) l is the propagation length of the nth echo, and f is the ultrasonic frequency.

From the sound velocity v calculated in this way, the elastic constant C ₄₄ is calculated from the equation 2: C ₄₄ = ρv ² . Here, ρ is the density of silicon.

As described above, to detect the sequential sound velocity v from the phase difference phi _n of ultrasonic pulse. Then, to calculate the decrease [Delta] C ₄₄ of the elastic constants _{C 44} with decreasing cooling temperature from the sound velocity v, the decrease [Delta] C ₄₄ of the elastic constants _{C 44,} the amount _{[Delta] C} 44 _{/ C 44} of the low-temperature softening of elastic constant Can be calculated.

The absolute value of the atomic vacancy concentration N in the silicon wafer is determined based on the low temperature softening amount ΔC ₄₄ / C ₄₄ of the elastic constant of the silicon sample obtained by the above measurement. Specifically, the atomic vacancy concentration \ N = (1.5 ± 0.2) × 10 ¹³ / cm ³ corresponds to the low temperature softening amount ΔC ₄₄ / C ₄₄ = 1 × 10 ⁻⁴ . Based on this, the atomic vacancy concentration N is determined. Thereby, the absolute value of the atomic vacancy concentration in the silicon wafer can be determined.

  Due to the electric quadrupoles of the atomic vacancies in the boron-doped silicon wafer, which is a semiconductor substrate material, the elastic constant is softened at low temperatures. If the principle of quantum mechanics in which the magnitude of softening at low temperature is proportional to the atomic vacancy concentration is used, it can be expected to develop as an innovative technique for evaluating atomic vacancies in silicon wafers. The interaction between the electric quadrupole of the vacancy orbit of site i and the ultrasonic distortion is

Can be written. g is a coupling constant determined in this example. Furthermore, electric quadrupole coupling of vacancies at different sites is

Can be written. The vacancy orbit formed around the vacancies of the boron-added silicon wafer contains an odd number of three electrons and undergoes orbital degeneracy due to spin-orbit interaction (Γ ₈ ). Is realized. For this reason, the quadrupole susceptibility χ increases in proportion to the reciprocal of the temperature at low temperature (χ to 1 / T), and the elastic constant is softened.

Becomes more prominent by approaching absolute zero, and low-temperature ultrasonic measurement is effective. Furthermore, atomic vacancy orbits are originally formed from Bloch electrons that have expanded infinitely, and their orbital radii have expanded as much as 1 nm. Therefore, the electric quadrupole has become enormous and the quadrupole-strain interaction is g ~. It is extremely large as 2.8 × 10 ⁵ . Between atomic vacancies through phonons and hole bands, quadrupole fluctuations can be observed even at absolute zero due to the antiferromagnetic quadrupole coupling g ′ <0. For this reason, we noticed that atomic vacancies that exist at an extremely dilute concentration of 10 billion Si atoms can be detected with sufficient accuracy by measuring ultrasonic softening at low temperatures. The idea of determining the absolute value of atomic vacancy concentration based on it was obtained.

The elastic constants largest cold softening is observed is C _44. By measuring the low temperature softening of the elastic constant C ₄₄ by the ultrasonic wave propagating in the direction of the crystal orientation [100], the amount of the low temperature softening can be measured with the highest sensitivity.

  The softening at low temperature disappears due to a magnetic field applied from outside, but the behavior disappears depending on the direction of application of the magnetic field. When a magnetic field is applied in parallel to the surface ultrasonic wave traveling direction, the magnetic field behaves differently when applied perpendicular to the surface ultrasonic wave traveling direction and parallel to the wafer surface, or when the magnetic field is applied perpendicular to the wafer surface. .

As described above, the method for determining the absolute value of the atomic vacancy concentration in the silicon wafer according to the present embodiment includes the measurement process of measuring the low temperature softening amount ΔC ₄₄ / C ₄₄ of the elastic constant of the silicon sample, and the measurement process. And a determination step of determining an absolute value of the atomic vacancy concentration N in the silicon wafer based on the low temperature softening amount ΔC ₄₄ / C ₄₄ measured in step (1). More specifically, in the determination step, the atomic vacancy concentration N = (1.5 ± 0.2) × 10 ¹³ / with respect to the low-temperature softening amount ΔC ₄₄ / C ₄₄ = 1 × 10 ⁻⁴ . The atomic vacancy concentration N is determined based on the corresponding cm ³ . Preferably, the measurement step is performed at a temperature of 20 mK to 20K.

  Therefore, the absolute value of the atomic vacancy concentration in the silicon wafer can be determined.

  According to the present invention, a silicon wafer that specifically displays the quantity of atomic vacancy concentration measured by ultrasonic waves can be put into practical use in the semiconductor industry. Atomic vacancies in silicon wafers are a factor that dominates oxide minute defect (BMD) deposition in the semiconductor manufacturing process. For this reason, when the display of atomic vacancy concentration on wafers is put into practical use, the yield of manufacturing cutting-edge devices such as memory, arithmetic elements (CPUs), and image sensors, which are increasingly miniaturized, will dramatically increase. improves. It can make a significant contribution to improving the performance of power semiconductors that are currently attracting attention through clean energy control.

The method for determining the absolute value of the atomic vacancy concentration in the silicon wafer of the present invention includes a silicon sample 6 in which an ultrasonic oscillator 27 and an ultrasonic receiver 28 are formed, and an external magnetic field with respect to the silicon sample 6. The magnetic force generating means 4 for applying the pressure, the cooling means 3 for cooling the silicon sample 6, the ultrasonic pulse oscillated from the ultrasonic oscillator 27, and the ultrasonic receiver 28 that propagates through the silicon sample 6. The detection coaxial line 5 for detecting a phase difference with the ultrasonic pulse received by the calculation means, a calculation means for calculating the elastic constant C ₄₄ of the silicon sample based on the phase difference, and a low temperature softening amount ΔC ₄₄ of the elastic constant. Determination of determining the atomic vacancy concentration N based on the fact that the atomic vacancy concentration N = (1.5 ± 0.2) × 10 ¹³ / cm ³ corresponds to / C ₄₄ = 1 × 10 ⁻⁴ Using a device equipped with means You can. Here, the calculation means for calculating the elastic constant C ₄₄ of the silicon sample based on the phase difference, and the atomic vacancy concentration N with respect to the low-temperature softening amount ΔC ₄₄ / C ₄₄ = 1 × 10 ^{−4 of the} elastic constant. The determining means for determining the atomic vacancy concentration N based on the fact that = (1.5 ± 0.2) × 10 ¹³ / cm ³ can be configured by computer software or the like.

3 dilution refrigerator (cooling means)
4 Magnetic force generation means 5 Detection coaxial line (detection means)
6 Silicon samples
27 Ultrasonic oscillator
28 Ultrasonic receiver

Claims (5)

Measurement step of measuring low temperature softening amount ΔC ₄₄ / C ₄₄ of elastic constant of silicon sample, and atomic vacancy concentration in silicon wafer based on said low temperature softening amount ΔC ₄₄ / C ₄₄ measured in this measurement step And a determination step for determining an absolute value of N. A method for determining an absolute value of an atomic vacancy concentration in a silicon wafer. In the determination step, the atomic vacancy concentration N = (1.5 ± 0.2) × 10 ¹³ / cm ³ corresponds to the low-temperature softening amount ΔC ₄₄ / C ₄₄ = 1 × 10 ⁻⁴ . 2. The method for determining an absolute value of atomic vacancy concentration in a silicon wafer according to claim 1, wherein the atomic vacancy concentration N is determined based on the above. The method for determining an absolute value of atomic vacancy concentration in a silicon wafer according to claim 1 or 2, wherein the measuring step is performed at a temperature of 20 mK to 20 K. Measurement step of measuring low temperature softening amount ΔC ₄₄ / C ₄₄ of elastic constant of silicon sample, and atomic vacancy concentration in silicon wafer based on said low temperature softening amount ΔC ₄₄ / C ₄₄ measured in this measurement step A silicon wafer manufacturing method comprising: a determination step of determining an absolute value of N. A silicon sample in which an ultrasonic oscillator and an ultrasonic receiver are formed, a magnetic force generating means for applying an external magnetic field to the silicon sample, a cooling means for cooling the silicon sample, and an oscillation from the ultrasonic oscillator Detecting means for detecting a phase difference between the ultrasonic pulse propagated through the silicon sample and received by the ultrasonic receiver, and an elastic constant C ₄₄ of the silicon sample based on the phase difference. The calculation means for calculating and the low temperature softening amount ΔC ₄₄ / C ₄₄ = 1 × 10 ^{−4 of the} elastic constant has an atomic vacancy concentration N = (1.5 ± 0.2) × 10 ¹³ / cm ^3. An apparatus for determining the absolute value of the atomic vacancy concentration in a silicon wafer, comprising: a determining means for determining the atomic vacancy concentration N based on the equivalent.