JP5615303B2 - Impurity concentration measuring method and impurity concentration measuring apparatus - Google Patents

Description

  The present invention relates to an impurity concentration measuring method and an impurity concentration measuring apparatus for measuring the concentration of impurities contained in a wafer, and can be used, for example, when measuring the concentration of carbon contained in a silicon wafer.

  A silicon single crystal widely used as a power device substrate contains carbon impurities. Since carbon impurities have a great influence on the characteristics of semiconductor devices, it is important to know the carbon content contained in a silicon wafer. As a method for measuring the concentration of carbon contained in a silicon wafer, there is a technique using infrared absorption (for example, Patent Documents 1 and 2).

  In the technique according to Patent Document 1, the carbon concentration is measured from the infrared absorption peak intensity due to substitutional carbon in a silicon single crystal using an infrared absorption method. Moreover, in the technique which concerns on patent document 2, carbon concentration is measured from the infrared absorption peak intensity | strength by the carbon-oxygen complex in a silicon single crystal using the infrared absorption method.

JP-A-6-194310 JP 2003-75340 A

  However, in the impurity concentration measurement method using the infrared absorption method, when the sample (wafer) thickness is small, the amount of infrared absorption decreases, and the absorption peak cannot be detected. For this reason, in the impurity concentration measurement method using the infrared absorption method, the thickness of the wafer needs to be about several mm.

  A silicon single crystal wafer used as a substrate of a power device is thin and has a sample thickness of about 650 μm at most. That is, in the impurity concentration measurement method using the infrared absorption method, when the measurement target is such a thin wafer, the low concentration impurity contained in the wafer cannot be measured. That is, when the wafer is thin, the measurement method cannot measure low-concentration impurities contained in the wafer.

  Further, when the carrier concentration on the surface layer of the wafer is high, infrared rays are reflected by the surface layer. For this reason, in the impurity concentration measurement method using the infrared absorption method, when the object to be measured is a wear having a low resistance layer formed by ion implantation or impurity diffusion on the surface layer, the inner side of the surface layer It is impossible to measure the impurity concentration of the wafer contained in the wafer.

  Therefore, the present invention provides an impurity concentration measuring method and an impurity concentration measuring apparatus capable of accurately measuring an impurity concentration even for a wafer containing low concentration impurities even when the wafer is thin. The purpose is to provide.

  It is another object of the present invention to provide an impurity concentration measuring method and an impurity concentration measuring apparatus capable of accurately measuring the impurity concentration even for a wafer having an ion implantation layer formed on the surface layer.

In order to achieve the above object, an impurity concentration measuring method according to claim 1 of the present invention is an impurity concentration measuring method for measuring the concentration of impurities contained in a wafer, and (A) for the wafer, A step of irradiating an electron beam having energy for moving a carbon atom existing at a lattice position to an interstitial position ; and (B) performing a photoluminescence method on the wafer after the step (A). Obtaining a first intensity that is a photoluminescence intensity derived from an element constituting the wafer and a second intensity that is a photoluminescence intensity derived from the impurity element; C) measuring the concentration of the impurity in the wafer using the first intensity, the second intensity, and a calibration curve prepared in advance.

An impurity concentration measuring method according to claim 1 of the present invention is an impurity concentration measuring method for measuring the concentration of impurities contained in a wafer, wherein (A) carbon atoms present at lattice positions are measured with respect to the wafer. A step of irradiating an electron beam having energy to be moved to an interstitial position ; and (B) after the step (A), by performing a photoluminescence method on the wafer, the elements constituting the wafer A step of obtaining a first intensity that is the intensity of the derived photoluminescence and a second intensity that is the intensity of the photoluminescence derived from the impurity element; and (C) the first intensity And a step of measuring the concentration of the impurity in the wafer using the second intensity and a calibration curve prepared in advance.

  Thus, in the present invention, not the infrared absorption method but the photoluminescence method is used. Therefore, even when the wafer is thin, the impurity concentration can be accurately measured even for a wafer containing a low concentration of impurities. Moreover, in this invention, before performing a photo-luminescence method with respect to a wafer, the electron beam irradiation process is performed with respect to the said wafer. By the electron beam irradiation treatment, impurities can be changed to a state that can be detected by photoluminescence. As described above, in the present invention, the concentration of impurities contained in the wafer can be measured by performing the photoluminescence method after performing electron beam irradiation on the wafer.

It is the perspective view which showed typically the structure of the impurity concentration measuring apparatus 100 which concerns on this invention. 3 is an enlarged plan view showing a configuration of a wafer stage 9. FIG. It is a flowchart for demonstrating operation | movement of the impurity concentration measuring method which concerns on this invention. It is a figure which shows the photoluminescence spectrum after electron beam irradiation. It is a figure for demonstrating the preparation method of a calibration curve. It is a figure which shows the photoluminescence spectrum in the case of not performing electron beam irradiation.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.

<Embodiment 1>
FIG. 1 is a perspective view schematically showing the configuration of an impurity concentration measuring apparatus 100 according to the present invention. Hereafter, each component with which the impurity concentration measuring apparatus 100 is provided is demonstrated with reference to FIG.

  The impurity concentration measuring apparatus 100 includes an electron beam generator 1, a horizontal beam sweep electrode 2, a vertical beam sweep electrode 3, a beam shutter 4, a vacuum pump 5, a housing 6, a gate valve 7, a wafer stage 9, and a stage transport unit. 10, a laser light source 11, a spectrometer 12, a detector 13, and a personal computer (PC) 14.

  The electron beam generator 1 generates an electron beam EB that irradiates the wafer 8 placed on the wafer stage 9. The horizontal beam sweep electrode 2 controls the traveling direction of the electron beam EB toward the wafer 8 in the horizontal direction, and the vertical beam sweep electrode 3 travels in the vertical direction. To control. The beam shutter 4 is used to block the electron beam EB. The vacuum pump 5 evacuates the propagation area of the electron beam EB and the arrangement area of the wafer 8 in the impurity concentration measuring apparatus 100. The housing 6 holds the propagation area of the electron beam EB in a vacuum.

  The gate valve 7 separates the vacuum between the generation region of the electron beam EB and the sample introduction region of the electric wire EB. The wafer stage 9 places and fixes a wafer 8 as a sample. The stage transfer unit 10 is used to place the wafer stage 9 in a vacuum. The laser light source 11 irradiates the wafer 8 placed on the wafer stage 9 with a laser beam 18. The spectroscope 12 separates the photoluminescence 19 emitted from the wafer 8 placed on the wafer stage 9. The detector 13 detects the photoluminescence 19 separated by the spectrometer 12. Then, the PC 14 obtains the impurity concentration from the photoluminescence 19 detected by the detector 13.

  In the impurity concentration measuring apparatus 100, the electron beam generator 1 generates an electron beam EB with the beam shutter 4 and the gate valve 7 being opened. As a result, the uniform electron beam EB is directly irradiated onto the wafer 8 fixedly placed on the wafer stage 9 (that is, without going through a glass window described later). The electron beam EB penetrates the wafer 8.

  FIG. 2 is an enlarged plan view showing the configuration of the wafer stage 9. Here, the wafer stage 9 shown in FIG. 2 is a plan view viewed from the irradiation side of the laser beam 18.

  As shown in FIGS. 1 and 2, the wafer stage 9 is provided with a cooling unit 16 in which a coolant circulates. By circulating a coolant such as liquid helium in the cooling unit 16, the entire wafer stage 9 including the wafer 8 can be cooled.

  As shown in FIG. 2, a glass window 17 that transmits visible light is provided on the side of the wafer stage 9 irradiated with the laser beam 18. Similarly, a glass window that transmits visible light is also provided on the irradiation side of the stage 10 with the laser beam 18 (not shown in FIG. 1).

  The laser beam 18 emitted from the laser light source 11 passes through the glass window of the stage transfer unit 10 and the glass window 17 of the wafer stage 9 and is irradiated onto the wafer 8 placed on the wafer stage 9.

  The wafer 8 that has been irradiated with the laser beam 18 emits photoluminescence 19. The photoluminescence 19 is transmitted through the glass window 17 of the wafer stage 9 and the glass window of the stage transfer unit 10. The transmitted photoluminescence 19 is separated by the spectroscope 12 and then detected by the detector 13. The PC 14 calculates the impurity concentration using the detected photoluminescence 19.

  Hereinafter, the operation of the impurity concentration measuring apparatus 100 according to the present embodiment will be described using the flowchart shown in FIG. Here, in the following description, the case where the wafer 8 is a silicon single crystal wafer and the concentration of carbon contained as an impurity in the wafer 8 is measured will be referred to.

  The wafer 8 is placed and fixed on the wafer stage 9, and the stage transfer unit 10 moves the wafer 8 to the irradiation position of the electron beam EB. (See FIG. 1). Here, the wafer 8 is disposed in a space that is in a low pressure state by the vacuum pump 5 at the irradiation position of the electron beam EB.

  In this state, the electron beam generator 1 generates an electron beam EB with high energy (acceleration voltage: several hundred keV or more). The electron beam EB is emitted to a space in a low pressure state by the vacuum pump 5, and the propagation direction is adjusted by the horizontal beam sweep electrode 2 and the vertical beam sweep electrode 3. The electron beam EB whose propagation direction is adjusted propagates through the housing 6 that has been brought into a low pressure state by the vacuum pump 5 and is irradiated onto the wafer 8 (step ST1). That is, the wafer 8 is irradiated with a high energy electron beam EB.

  By irradiating the wafer 8 with the electron beam EB, the carbon in the silicon single crystal wafer 8 is changed to a state that can be detected by photoluminescence. That is, the carbon atom existing at the lattice position is moved to the interstitial position.

  Next, a refrigerant (for example, liquid helium) is circulated through the cooling unit 16 (step ST2). The wafer 8 placed on the wafer stage 9 is cooled by the cooling process in step ST2.

  By bringing the wafer 8 to a low temperature state, the photoluminescence of carbon is detected well. Therefore, it is desirable to perform the cooling process of step ST2. Here, it is desirable to lower the wafer 8 to an absolute temperature of 30 Kelvin or lower for good detection of carbon photoluminescence.

  In the flowchart of FIG. 3, the wafer 8 is cooled after irradiation with the electron beam EB. However, the wafer 8 may be cooled before irradiation with the electron beam EB and / or during irradiation with the electron beam RB. Here, each said cooling process is implemented until a carbon concentration measurement is complete | finished.

  Next, a laser beam 18 is emitted from the laser light source 11 (the laser beam 18 has a wavelength having energy equal to or greater than the band gap of silicon forming the wafer 8, for example). And the said laser beam 18 is irradiated with respect to the wafer 8 mounted in the wafer stage 9 (step ST3).

  Here, the irradiation of the electron beam EB is performed on the first main surface of the wafer 8, and the irradiation of the laser beam 18 is performed on the second main surface of the wafer 8 facing the first main surface. To be implemented. As described above, the laser beam 18 irradiates the second main surface of the wafer 8 after passing through each glass window 17.

  The wafer 8 that has been irradiated with the laser beam 18 emits photoluminescence 19 from the second main surface side. The photoluminescence 19 is received by the spectroscope 12 after passing through each glass window 17 as described above. The photoluminescence 19 is separated by the spectroscope 12 and then detected by the detector 13. By detecting the photoluminescence 19 in the detector 13, the PC 14 acquires a photoluminescence spectrum as shown in FIG. 4 (step ST4).

  Here, in FIG. 4, the vertical axis represents the intensity (count) of the photoluminescence 19, and the horizontal axis represents the wavelength (nm) of the photoluminescence 19. FIG. 4 is a photoluminescence spectrum from the wafer 8 having a carbon concentration of 0.05 ppm or less.

  In FIG. 4, peaks are formed at 1280 nm ± 5 nm and 1130 nm ± 5 nm, respectively. Here, the peak (G line) of 1280 nm ± 5 nm is photoluminescence derived from carbon, and the peak (TO line) of 1130 nm ± 5 nm is luminescence derived from silicon.

In addition to the G line and the TO line, a TA line, a TO + O ^Γ line, a plasma line derived from the laser beam 18, and a phonon replica of the G line appear in the photoluminescence spectrum of FIG.

  As described above, the photoluminescence method shown in steps ST3 and ST4 is applied to the wafer 8, and the PC 14 acquires a photoluminescence spectrum as shown in FIG. Thereafter, the PC 14 determines, from the photoluminescence spectrum, the first intensity which is the intensity of photoluminescence derived from the elements constituting the wafer 8 and the photoluminescence derived from the impurity elements contained in the wafer 8. A second intensity that is the intensity of the sense is acquired (step ST5).

  In the description of the operation, the silicon single crystal wafer 8 containing carbon is a measurement target. Therefore, in the description of the operation, the first intensity is the intensity of the TO line that is luminescence derived from silicon. Yes, the second intensity is the intensity of G-rays that are photoluminescence derived from carbon.

  Next, the PC 14 obtains the impurity (carbon) concentration of the wafer 8 using the first intensity acquired above, the second intensity acquired above, and a calibration curve set in advance. (Step ST6).

  A photoluminescence intensity ratio which is a value obtained by dividing the second intensity by the first intensity (second intensity / first intensity) is proportional to the concentration of impurities contained in the wafer 8. Therefore, in step ST6, the PC 14 obtains the impurity concentration in the wafer 8 using the photoluminescence intensity ratio and the calibration curve.

  The calibration curve is a line indicating a proportional relationship between the impurity concentration and the photoluminescence intensity ratio, and the calibration curve is prepared in advance in the following manner.

  First, two or more types of prepared wafers having different impurity concentration concentrations (the constituent elements of the prepared wafer are the same as the constituent elements of the wafer 8) are prepared. Here, in the description, two or more types of silicon single crystal wafers are prepared as preparation wafers, and each preparation wafer contains carbon having different concentrations. Here, from the viewpoint of improving the accuracy of the calibration curve, it is preferable to increase the number of prepared wafers.

  Further, the concentration of impurities (carbon) contained in each prepared wafer is measured using secondary ion mass spectrometry or the like. That is, each prepared wafer is kept in a known state of the concentration of contained impurities (carbon concentration). Here, the range of impurity concentration (carbon concentration) that can be detected by secondary ion mass spectrometry is about 0.02 ppm to 0.2 ppm.

  Next, each process of steps ST1 to ST4 shown in FIG. 3 is performed on each prepared wafer whose impurity concentration is known using the impurity concentration measuring apparatus 100 of FIG. As a result of each processing, a photoluminescence spectrum is obtained for each prepared wafer.

  Then, the third intensity and the fourth intensity are obtained for each photoluminescence spectrum from each photoluminescence spectrum for the prepared wafer by the same method as in step ST5.

  Here, the third intensity is the intensity of the photoluminescence derived from the element constituting the preparation wafer (in this case, silicon), and the fourth intensity is the impurity contained in the preparation wafer. It is the intensity of photoluminescence derived from the element (in this case, carbon).

  Next, for each photoluminescence spectrum (that is, for each preparatory wafer), a photoluminescence intensity ratio that is a value obtained by dividing the fourth intensity by the third intensity (fourth intensity / third intensity). (Hereinafter referred to as the intensity ratio for creating a calibration curve).

  Now, for each prepared wafer, the concentration of carbon contained is known, and the intensity ratio for creating a calibration curve was determined. Therefore, in the coordinate system in which the horizontal axis is the impurity (carbon) concentration and the vertical axis is the intensity ratio (intensity ratio) for creating the calibration curve, the known carbon concentration and the calculated intensity ratio for creating the calibration curve for each prepared wafer Is pointed to (see FIG. 5). Then, a straight line (or approximate line) passing through each pointing point is created over the entire impurity concentration range (see FIG. 5).

  In FIG. 5, the horizontal axis represents the impurity (carbon) concentration, and the vertical axis represents the calibration curve intensity ratio (or photoluminescence intensity ratio, simply indicated as the intensity ratio). Further, in FIG. 5, the portion indicated by “◯” is the pointing portion, and a straight line passing through each “◯” portion is created in the entire impurity concentration (carbon concentration) range. The created straight line (approximate line) becomes a calibration curve.

  The calibration curve can be used in common for each wafer 8 once it is created.

  The created calibration curve is set in advance in the PC 14 before measuring the concentration on the wafer 8. As described above, in step ST6, the PC 14 uses the photoluminescence intensity ratio obtained in steps ST1 to DT5 in FIG. 3 and the calibration curve (FIG. 5) created in advance to Obtain the impurity concentration.

  As described above, the photoluminescence intensity ratio is proportional to the concentration of impurities contained in the wafer 8. Therefore, the PC 14 obtains a point where the photoluminescence intensity ratio obtained in step ST5 and the calibration curve intersect (see “x” in FIG. 5). The value of the impurity (carbon) concentration at the intersecting point is the concentration of the impurity (carbon) contained in the wafer 8.

  As described above, in the impurity concentration measuring method according to the present embodiment, the photoluminescence method is performed on the wafer 8, and the resulting photoluminescence intensity ratio and the calibration curve prepared in advance are obtained. The concentration of impurities contained in the wafer 8 is measured.

  As described above, since the photoluminescence method is used instead of the infrared absorption method, even if the thickness of the wafer 8 is thin, the impurity is applied to the wafer 8 containing low concentration impurities. Concentration can be measured accurately. For example, in the present embodiment, even if the thickness of the wafer 8 is less than the order of several hundred μm, the impurity concentration of 0.005 ppm or less contained in the wafer 8 can be measured (the entire calibration curve shown in FIG. 5). Concentration measurement in a range is possible).

  Here, when the electron beam irradiation process of step ST1 is not performed, impurity carbon of silicon is not detected by photoluminescence as shown in FIG. That is, when step ST1 is not performed, no G line is detected in the photoluminescence spectrum of FIG.

  Therefore, in the impurity concentration measurement method according to the present embodiment, the electron beam irradiation process of step ST1 is performed on the wafer 8 before the photoluminescence method is performed on the wafer 8. By the process of step ST1, the impurity (carbon) can be changed to a state detectable by photoluminescence. That is, by the processing in step ST1, the impurity element (carbon atom) existing at the lattice position can be moved to the interstitial position (that is, the impurity is brought into an optically active state).

  As described above, in the present invention, the impurity concentration contained in the wafer 8 can be measured by performing the photoluminescence method after irradiating the wafer 8 with the electron beam.

  Further, in the impurity concentration measurement method according to the present embodiment, the photoluminescence method is performed on the wafer 8 cooled by the cooling unit 16 to an absolute temperature of 30 Kelvin or less. Therefore, the photoluminescence of carbon contained in the wafer 8 can be detected well.

<Embodiment 2>
In the present embodiment, the silicon single crystal wafer 8 in which the ion implantation layer is formed in the surface is the measurement target of the impurity concentration. In the case of the measurement object, in step ST3 treatment, which is one step of the photoluminescence method described in the first embodiment, a laser beam 18 having energy greater than or equal to the band gap of silicon is applied to a silicon single crystal having the ion implantation layer. Irradiate the wafer 8.

  For example, a laser beam 18 having a wavelength of 1000 nm or less is applied to the silicon single crystal wafer 8 having the ion implantation layer. Here, the silicon single crystal wafer 8 is placed and fixed so that the ion implantation layer faces the glass window 17 shown in FIG. That is, the laser beam 18 is irradiated from the ion implantation layer.

  Steps other than the above are the same as those described in the first embodiment. Also in the present embodiment, the first intensity is the intensity of the TO line that is luminescence derived from silicon, and the second intensity is the intensity of the G line that is photoluminescence derived from carbon. The calibration curve described in Embodiment 1 is used.

  In this way, by irradiating the silicon single crystal wafer 8 having the ion implantation layer with the laser beam 18 having energy higher than the band gap of silicon, the laser beam 18 can be prevented from being reflected by the ion implantation layer. . Therefore, the laser beam 18 reaches the inside of the silicon single crystal wafer 8 and the carbon concentration in the inside can be measured. That is, according to the present embodiment, it is possible to measure the carbon concentration with respect to the silicon wafer 8 having the ion implantation layer formed on the surface.

<Embodiment 3>
In the present embodiment, the epi-wafer 8 is an object for measuring the impurity concentration. The epitaxial wafer 8 has an epitaxial film formed on the surface of a silicon single crystal wafer. Specifically, in the present embodiment, the carbon concentration contained in the epitaxial film in the epi-wafer 9 is measured.

  Here, the epitaxial film is a film formed by epitaxial growth on a silicon single crystal wafer. The thickness of the epitaxial film is as thin as several μm.

  By shortening the wavelength of the laser beam 18 emitted from the laser light source 11, the carbon concentration of only the epitaxial film on the epi wafer 8 can be measured. Therefore, in the case of the measurement object, in step ST3 processing, which is one step of the photoluminescence method described in the first embodiment, the epiwafer 8 is irradiated with the laser beam 18 having a wavelength of 633 nm or less.

  Here, the epitaxial wafer 8 is mounted and fixed so that the epitaxial film faces the glass window 17 shown in FIG. That is, the laser beam 18 is irradiated from the epitaxial film.

  Steps other than the above are the same as those described in the first embodiment. Also in the present embodiment, the first intensity is the intensity of the TO line that is luminescence derived from silicon, and the second intensity is the intensity of the G line that is photoluminescence derived from carbon. The calibration curve described in Embodiment 1 is used.

  Thus, by irradiating the epi-wafer 8 with the laser beam 18 having a wavelength of 633 nm or less, the laser beam 18 enters only a distance of several μm (for example, about 3 μm) from the surface of the epi-wafer 8. That is, according to the present embodiment, the carbon concentration in the thin epitaxial film formed on the surface of the silicon single crystal wafer can be measured.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  DESCRIPTION OF SYMBOLS 1 Electron beam generation part, 2 Horizontal beam sweep electrode, 3 Vertical beam sweep electrode, 4 Beam shutter, 5 Vacuum pump, 6 Case, 7 Gate valve, 8 Wafer (epi wafer), 9 Wafer stage, 10 Stage conveyance part , 11 Laser light source, 12 Spectrometer, 13 Detector, 14 Personal computer (PC), 16 Cooling unit, 17 Glass window, 18 Laser beam, 19 Photoluminescence, EB Electron beam, 100 Impurity concentration measuring device.

Claims (9)

An impurity concentration measurement method for measuring the concentration of impurities contained in a wafer,
(A) irradiating the wafer with an electron beam having energy to move carbon atoms existing at lattice positions to interstitial positions ;
(B) After the step (A), by performing a photoluminescence method on the wafer, a first intensity which is an intensity of photoluminescence derived from an element constituting the wafer, and the impurity A step of obtaining a second intensity that is a photoluminescence intensity derived from the element;
(C) using the first intensity, the second intensity, and a calibration curve prepared in advance, measuring the concentration of the impurity in the wafer,
Impurity concentration measuring method characterized by the above. (A) preparing at least two kinds of preparatory wafers with known concentrations of the impurities;
(B) irradiating each of the prepared wafers with an electron beam;
(C) After irradiating the electron beam, by performing a photoluminescence method on each of the prepared wafers, a third intensity that is an intensity of photoluminescence derived from an element constituting the prepared wafer; A fourth intensity, which is a photoluminescence intensity derived from the impurity element, is obtained for each of the prepared wafers;
(D) calculating the intensity ratio between the third intensity and the fourth intensity for each of the prepared wafers;
(E) determining the calibration curve from the intensity ratio with respect to each preparation wafer and the concentration of the impurities contained in each preparation wafer;
The impurity concentration measuring method according to claim 1. The step (C)
Calculating the intensity ratio of the previous SL first intensity and said second intensity, from the intersection of the above calibration curve and the calculated intensity ratio, measuring the concentration of the impurity,
The impurity concentration measuring method according to claim 2. The elements constituting the wafer are
Silicon,
The impurity element is:
Carbon,
The measurement of the first intensity is
Carried out by detecting a peak appearing at 1130 nm ± 5 nm from the photoluminescence spectrum,
The measurement of the second intensity is
Carried out by detecting a peak appearing at 1280 nm ± 5 nm from the photoluminescence spectrum,
The impurity concentration measuring method according to claim 3. The step (B)
For the wafer cooled to an absolute temperature of 30 Kelvin or less,
The impurity concentration measuring method according to claim 4. In the surface of the wafer,
An ion implantation layer is formed,
The step (B)
The step of irradiating the wafer with light having energy greater than or equal to the band gap of the silicon, and carrying out the photoluminescence method.
The impurity concentration measuring method according to claim 4. On the surface of the wafer,
An epitaxial layer is formed,
The step (B)
Irradiating the wafer with light having a wavelength of 633 nm or less, and performing the photoluminescence method.
The impurity concentration measuring method according to claim 4. An impurity concentration measuring device for measuring the concentration of impurities contained in a wafer,
A stage on which the wafer is placed;
Irradiating the placed wafer on the stage, the electron beam generating section which carbon atoms present in the grid position generating a sagittal electricity with energy to move the interstitial sites,
A light source unit that irradiates light on the wafer placed on the stage;
A detector that detects photoluminescence emitted from the wafer that has been irradiated with the light from the light source; and
A computer unit that determines the concentration of the impurities contained in the wafer from a detection result from the detector and a preset calibration curve is provided.
An impurity concentration measuring apparatus characterized by the above. A cooling unit disposed on the stage,
The impurity concentration measuring apparatus according to claim 8.