JP2002148191A - Semiconductor characteristic evaluation method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor characteristic evaluation method and apparatus capable of evaluating a characteristic value of a semiconductor and a characteristic value distribution in an ingot with high accuracy in the ingot state before being sliced like a wafer, performing selective milling including various machining specifications at the stage before slicing, to thereby improve yield in manufacturing a wafer, and quickly performing feedback to a crystal growth process. SOLUTION: This characteristic evaluation apparatus for a compound semiconductor is provided with a movable stage 12 for supporting the ingot of a compound semiconductor, the surface of which is smoothed to remove a surface affected layer, an excitation light source 18 for radiating excited light capable of causing inter-band absorption transfer between a valence band and a conduction band of the compound semiconductor intermittently or continuously along the longitudinal direction of the compound ingot in the room temperature environment in the atmosphere of inert gas, a photo detecting part 20 for detecting photoluminescence light obtained by irradiation of the excited light, and an evaluating means for evaluating the carrier concentration according to at least one of wavelength information and intensity information of the photoluminescence light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for evaluating the characteristics of compound semiconductors, and more particularly, to grasping characteristic values of compound semiconductors in advance in an ingot state prior to wafer slicing, and converting compound semiconductors into wafers. The present invention relates to a method and an apparatus for evaluating the characteristics of a compound semiconductor, which can be sorted out according to its characteristics before slicing, and can be quickly fed back to crystal growth conditions.

[0002]

2. Description of the Related Art Compound semiconductors include high frequency devices, light emitting diodes (LEDs), laser diodes (LDs), and the like.
Various applications have been made in the fields of high-speed information communication and optoelectronics. Generally, when manufacturing these devices, a compound semiconductor wafer is used as a substrate thereof. For example, in the case of an LED or LD, light is emitted by epitaxially growing a pn layer on a wafer and injecting current into the junction. At this time, a current flows vertically from the upper surface of the epitaxial layer and the electrode formed on the back surface of the substrate, so that the conductivity type of the substrate (p-type,
Not only n-type) but also the substrate resistance and carrier concentration are important characteristic values, and different values are required for different wafer applications.

In general, a compound semiconductor wafer is manufactured into a single crystal ingot by a liquid sealing Czochralski method, a horizontal boat method, a vertical boat method or the like, and cut into a wafer having a thickness of several hundred μm by slicing. It is manufactured as a product wafer through processes such as lapping, etching, and mirror polishing. Further, in order to control the characteristic value required for the compound semiconductor wafer, a predetermined impurity (dopant) is added (doped) together with a predetermined amount of raw material during the growth of the ingot.

[0004] However, since the segregation coefficient of impurities rarely becomes 1, the impurity concentration in the obtained ingot has a gradient. For example, when Zn is added to GaAs, the effective segregation coefficient is about 0.4, and when the solidification ratio of the ingot is 0.1 and 0.9, the latter has an impurity concentration of about 3 of the former. 0.7 times. In addition, when the volatility is high or when a dopant involving a chemical reaction loss is used in the growth system, the impurity concentration of the ingot may vary between growth lots.

As described above, it is necessary to inspect a wafer cut from a single crystal ingot to determine a range satisfying the required value of the carrier concentration for the required value of the carrier concentration which varies depending on the use of the wafer.

On the other hand, as a well-known method for evaluating the electric impurity concentration, that is, the carrier concentration and the resistivity, a hole (Ha) is used.
ll) A method utilizing the effect, a method of forming a diode and utilizing its capacitance-voltage characteristic (CV), and the like are known (for example, Semiconductor Evaluation Technology, edited by Takashi Kawatoda (Sangyo Tosho), 221). 235). These evaluation methods are actually used as standard methods for evaluating the carrier concentration and resistivity of a compound semiconductor.

However, in these methods, it is necessary to attach electrodes to a sample to be evaluated. In general, a wafer or a wafer-like sample piece is sliced from an ingot, and further, in the measurement of the Hall effect, a strip-shaped or cloverleaf is cut from the wafer. Since it is cut out into a shape or a square to form a sample, it is a destructive inspection. Also, in the CV method, even when the sample is most easily prepared, the surface on which the Schottky electrode is formed must be clean and free of a processed layer, so that mirror polishing or mirror etching is required, and eventually the destruction occurs. Inspection. That is, it can be said that it is practically impossible to carry out these evaluation methods in an ingot state.

As a method for evaluating the carrier concentration characteristics, in addition to the above-mentioned two methods which are generally put into practical use, typical evaluation methods which have been conventionally developed include the following.
A light absorption method and a photoluminescence method are known. Hereinafter, these methods will be described.

Light absorption method This method is a method in which light is transmitted through a wafer to determine the impurity concentration from the amount of absorption. In the case of GaAs, it is used to obtain a deep impurity level (EL2) concentration. (GM Martin, Appl. Phys. Lett. 39.747 (1981)
See). Further, in the case of an n-type doped crystal, free carrier absorption occurs, and at an infrared wavelength of 4 μm or more, α∝K · n between the carrier concentration n and the absorption coefficient α.
It has been reported that there is a relationship of λ ³ (K represents a constant and λ represents a wavelength) (JS Blakemore, J. Appl. Ph.
ys. 53. R144 (1981)), the carrier concentration can be calculated from this relationship.

However, in this method, since the evaluation is made based on the absorption of light, it is generally desirable that the light incident surface and the light emitting surface are parallel to each other. As a result, the progress of light is hindered, so that there is a problem that reproducible results cannot be obtained unless the cleaning is clean. In addition, there is an appropriate sample thickness according to the carrier concentration of the sample, as can be seen from the above equation,
If the carrier concentration is high, the absorption coefficient is too large,
There is a problem that transmitted light becomes too weak, and it is difficult to evaluate a carrier concentration range having a large thickness in a fixed form.

Photoluminescence Method In general, the photoluminescence method involves irradiating light having energy larger than the forbidden band width to form an excess electron-hole pair in the interband absorption process, so that the electrons are directly or variously captured. Light emitted when the electrons recombine with holes or shallow acceptor levels in the valence band via luminescence (luminescence)
This is an evaluation method using the information as information. Since the luminescence intensity decreases as the sample temperature increases, it is often measured at a liquid helium temperature (4.2 K), a liquid nitrogen temperature (77 K), or a low temperature state using a refrigerator.
In this method, the spectrum changes depending on the type and concentration of the impurity in the semiconductor material to be evaluated, and the impurity concentration can be determined by using the spectrum.

For example, in the case of a GaAs Si-doped crystal, it is known that the peak wavelength of the photoluminescence spectrum shifts to the higher energy side with the Si concentration (Semiconductor Evaluation Technology, edited by Takashi Kawatoda (industrial book), 267, see FIG. 7.6). Similarly, in Si-doped GaAs, a comparison between the theoretically calculated value and the actual value of the photoluminescence spectrum shape with respect to the carrier concentration, the shift amount of the peak wavelength of the spectrum, the energy position on the high energy side which is half the peak value, and the carrier concentration The relationship and the relationship between the spectral half width (FWHM) and the carrier concentration have been reported (see Yunosuke Makita, Lectures of the Electrotechnical Laboratory, 48, 508 (1984)). In addition, a comparative example of a photoluminescence intensity map and a carrier concentration map obtained by a CV method for a fine region in a Si-doped GaAs mirror surface wafer has also been reported (R. Toba, et. Al., Material Science Forum V
196-201, 1785 (1995)).

As described above, in the photoluminescence method, since crystal characteristic information such as carrier concentration can be obtained from wavelength information and intensity information, this method is very useful.
Another advantage is that there is no need to perform electrode attachment unlike the Hall effect or the CV method.

In general, however, in this method, it is a common sense to use, as a target sample surface, a mirror-polished or mirror-etched wafer or a strip-shaped sample surface cut from a wafer. When the strength is actually compared, the state of the surface must be constant. Therefore, in order to obtain a surface with good reproducibility, a mirror-polished surface equivalent to the wafer product level is required. Further, in the case of the same excitation light intensity condition, the latter has a photoluminescence emission intensity lower by one to two orders of magnitude between the mirror surface state and the lap surface.
The evaluation in the mirror state is more advantageous including the SN ratio at the time of detection. In addition, when measurement is performed at a low temperature, the band edge emission group can obtain a finely split spectrum, so that impurities and defects can be identified.
Since the emission intensity is lower by about one to four orders of magnitude at low temperature than at room temperature, it is common sense to cool for measurement.

In recent years, with the improvement of sensitivity on the detection side,
Detection has become possible even when the luminescence intensity is weak, and evaluation has become possible for limited purposes even at room temperature. Here, the limited purpose is that the fine structure of the spectrum obtained only by measurement at the temperature of liquid helium or liquid nitrogen disappears as the temperature rises, so the same content as at low temperature cannot be evaluated, but such This means that it is not necessary to obtain a fine structure of the spectrum.

In addition to the above-mentioned characteristic requirements relating to the carrier concentration, various factors such as a wafer plane orientation (cutting by intentionally shifting the orientation from the ingot growth axis orientation) and a wafer thickness differ depending on the use of the device. Is becoming
Naturally, the final wafer product must satisfy all of these various characteristic values, but this has caused the following problems.

That is, the required range for the carrier concentration characteristic value is often narrower than the concentration change range in the ingot. Therefore, it is necessary to perform cutting at the time of slicing including processing specifications according to individual device applications. for that reason,
Conventionally, sorting processing has been performed at the time of slicing by estimating an outline of a boundary position such as carrier concentration based on accumulated data.

[0018]

However, in addition to the fact that the concentration of impurities in the ingot varies depending on the location due to the segregation phenomenon, and the variation width between the growth batches is overplayed, the characteristic values may differ from the expected values. In that case, there is a problem that the trouble and the loss are increased, for example, it is necessary to confirm and evaluate the required range of the carrier concentration due to the loss or addition of the material. In addition, the crystal characteristic value of the ingot should be fed back to the crystal growth conditions promptly. In the case of an experiment, it is possible to evaluate any sample piece, but in industrial production, the processing specification In many cases, slicing is performed after the product characteristic range including the above is determined, and conversely, there has been a problem that the feedback period becomes longer.

As described above, there has been a problem that the characteristic values such as the carrier concentration and the resistivity have to be evaluated after slicing the wafer from the ingot in the conventional evaluation method.

In the case where the measurement and distribution of the carrier concentration are to be evaluated in the ingot state, it is most likely that the above-described photoluminescence method is applied in a room temperature environment. However, in that case, there are the following problems.

(1) The compound semiconductor ingot to be measured is generally manufactured by a liquid-sealed Czochralski (LEC) method, a vertical boat (VBG) method, a horizontal boat (HB) method, or the like. is there. Although the crystal of the LEC method has improved diameter controllability, the crystal surface has irregularities of about several mm, and the VBG method and the HB method have irregularities of the contact portion in the container, and the surface is smooth. However, since the surface is deteriorated by thermal decomposition or contact, the characteristics of the outermost surface do not reflect the characteristics inside the ingot. Therefore, even if these surfaces are evaluated, the internal information cannot be accurately captured.

(2) In general, a semiconductor wafer is obtained by slicing a single crystal ingot into a circular or rectangular wafer. Immediately before that, in order to form the ingot into a fixed form, cylindrical grinding or surface grinding is performed. In this case, since the mechanical grinding is performed, the surface condition is determined by the grinding wheel and the processing conditions.
It can be finished to a level uneven surface. However, since dirt such as a grinding fluid is generated, it cannot be considered as a common sense that the surface is used for optical evaluation such as photoluminescence. In addition, since it is not in a mirror-finished state, the emission intensity of photoluminescence is reduced by about one or two digits, and it is considered that the excitation light intensity needs to be increased by one or two digits for detection.

(3) However, when the surface of the compound semiconductor is irradiated with strong excitation light, the intensity of the photoluminescence light changes with time. For example, in the case of GaAs or InP, when strong excitation light is irradiated in the air atmosphere as shown in FIG. 1A, the emission intensity attenuates and gradually increases as shown in FIG. 1B. Although the cause of this phenomenon has not been elucidated scientifically, it does not occur in samples in liquid helium or liquid nitrogen, and is thought to be caused by some change in the surface structure, such as the reaction of atmospheric components with GaAs or InP. In particular, this phenomenon becomes more remarkable as the intensity of the excitation light increases. Normally, the wavelength of the spectroscope on the detection side is scanned in order to obtain a spectrum. However, the emission intensity changes every moment during scanning, which greatly affects the measured spectrum shape as shown in FIG. . That is, an error is given to the evaluation of the wavelength information such as the peak wavelength and the full width at half maximum (FWHM), and an error also occurs in the carrier concentration evaluation using the wavelength information of the photoluminescence.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and has been made to highly accurately evaluate the characteristic value of a semiconductor and the characteristic value distribution in an ingot in an ingot state before slicing into a wafer. A semiconductor property evaluation method capable of performing selective slice processing including various processing specifications at a stage before slicing, improving yield in wafer manufacturing, and quickly performing feedback to a crystal growth process, and the like. It is intended to provide a device.

[0025]

Means for Solving the Problems The inventor of the present invention has made intensive studies to solve the above-mentioned problems, and as a result, the compound semiconductor ingot obtained by smoothing the surface and removing the surface-altered layer was compared with the compound semiconductor ingot. By irradiating excitation light capable of causing an inter-band absorption transition between the electronic band and the conduction band in an inert gas atmosphere, preferably in a dry nitrogen atmosphere, even from the ground ingot surface, even at room temperature. It is possible to obtain photoluminescence light of sufficient intensity without change over time, and to predict the carrier concentration distribution in the ingot state before slicing into a wafer with sufficient accuracy based on the wavelength information and intensity information. And found that the present invention was completed.

That is, according to the semiconductor characteristic evaluation method of the present invention, a GaAs having a surface smoothed and a surface altered layer removed is provided.
fixing ingots of compound semiconductors such as s and InP,
Excitation light that can cause interband absorption transition between the valence band and the conduction band of the compound semiconductor intermittently or continuously along the longitudinal direction of the ingot of the compound semiconductor is generated in an inert gas atmosphere at room temperature. The irradiation is performed in a medium atmosphere, preferably a nitrogen atmosphere, and the carrier concentration is evaluated based on at least one of the wavelength information and the intensity information of the photoluminescence light obtained by the irradiation of the excitation light.

In the method for evaluating the characteristics of a semiconductor, it is preferable that the light irradiation surface of the ingot of the compound semiconductor is subjected to cylindrical grinding or surface grinding.

Further, the apparatus for evaluating the characteristics of a compound semiconductor according to the present invention is characterized in that the surface is smoothed and the surface altered layer is removed.
Supporting means for supporting an ingot of a compound semiconductor such as As or InP; and inter-band absorption transition between a valence band and a conduction band of the compound semiconductor intermittently or continuously along the longitudinal direction of the compound ingot. Light irradiation means for irradiating an excitation light capable of causing the light in an inert gas atmosphere at room temperature environment, preferably in a nitrogen atmosphere, light detection means for detecting photoluminescence light obtained by irradiation of the excitation light, Evaluation means for evaluating the carrier concentration based on at least one of the wavelength information and the intensity information of the photoluminescence light.

In this semiconductor characteristic evaluation apparatus, it is preferable that the light irradiation surface of the compound semiconductor ingot is subjected to cylindrical grinding or surface grinding. Further, in the above-described semiconductor characteristic evaluation apparatus, the excitation light applied to the ingot of the compound semiconductor is moved one-dimensionally or two-dimensionally onto the light irradiation surface of the ingot of the compound semiconductor, and is irradiated. A position information means for obtaining position information may be provided. Further, in the above-described apparatus for evaluating characteristics of a semiconductor, it is preferable that a holding means for holding a distance between the light irradiation surface of the ingot of the compound semiconductor, the light irradiation means and the light detection means constant. Further, it is preferable that the light irradiating means irradiates the compound semiconductor ingot with excitation light from a vertically lower side or a horizontal direction.

[0030]

When evaluating the carrier concentration of a compound semiconductor, the surface-altered layer of the ingot is removed by cylindrical grinding or surface grinding, so that the surface irradiated with excitation light in the photoluminescence method has the same crystal characteristic surface as the inside of the ingot. The distribution in the ingot state can be evaluated without slicing into a wafer or collecting sample fragments.

The temporal change of photoluminescence caused by the change of the surface structure in the air caused by the irradiation of the excitation light is described below.
Preferably, it can be prevented by using a dry nitrogen atmosphere, and the wavelength information and the intensity information can be accurately measured, so that the peak wavelength, the half width, the high energy side wavelength at which the peak becomes half value, and the Hall effect are obtained. It can be accurately calculated by using a correlation equation with the carrier concentration by measurement.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment of the method for evaluating the characteristics of a semiconductor according to the present invention, the characteristics of the semiconductor are evaluated using a photoluminescence method at room temperature.

Prior to the evaluation of the characteristics, the deteriorated layer on the outermost surface of the ingot during crystal growth is removed by cylindrical grinding or surface grinding to expose a surface having the same crystal characteristics as the inside of the ingot. This is also a step before processing the wafer, which is very convenient. in this way,
By making the surface to be evaluated a cylindrical or surface ground surface just before slicing, irregularities on the crystal surface and altered parts on the surface can be removed, and characteristic information inside the crystal can be obtained accurately. , It is possible to mark the measurement position of the photoluminescence spectrum,
It is extremely easy to perform selective slicing in accordance with the carrier concentration standard, and it is possible to greatly reduce material loss due to deviation from the standard.

When the photoluminescence spectrum is measured at room temperature in the state of a ground surface, the emission intensity of the photoluminescence is reduced. Therefore, the intensity of the excitation light is increased to secure a sufficient emission intensity for detection. Such a transient change in the emission intensity accompanying the increase in the excitation light intensity (FIG. 1)
(B) is prevented or suppressed by performing the excitation light irradiation in an inert gas, preferably dry nitrogen (or at least the excitation light irradiation part is in an inert gas atmosphere, preferably a dry nitrogen gas atmosphere). I do. Excitation light is 1mmφ
Since the spot light is of the order of magnitude and the surface change due to the light assist occurs only in this portion, the entire ingot may be in an inert gas atmosphere (preferably a dry nitrogen atmosphere). An active gas, preferably dry nitrogen, may be purged. By irradiating the excitation light in an inert gas (preferably dry nitrogen) as described above, even if the surface condition of the side surface of the ingot of the compound semiconductor is a surface condition subjected to cylindrical grinding, surface grinding, or the like, the semiconductor It is possible to obtain a photoluminescence spectrum without error regarding the wavelength information and the intensity information of the crystal (see FIG. 3).

Further, in order to obtain a distribution of wavelength information and intensity information of photoluminescence in the state of the ingot, the ingot shaped by cylindrical grinding, surface grinding, or the like is fixed to a reference plane for measurement, thereby irradiating the ingot with excitation light. With the distance between the surface and the excitation light irradiator and detector kept constant, the relative one-dimensional or two-dimensional scan between the surface of the ingot and the excitation light and detector is performed, and the relative irradiation is performed. The distribution of the photoluminescence spectrum is measured at different positions to evaluate the distribution of the photoluminescence spectrum in the ingot. By fixing the ingot in this way, the reliability of the excitation light intensity and the detected photoluminescence intensity can be improved.

Hereinafter, embodiments of a method and apparatus for evaluating semiconductor characteristics according to the present invention will be described in detail with reference to the accompanying drawings.

First, an embodiment of a semiconductor characteristic evaluation apparatus according to the present invention will be described with reference to FIGS.

As shown in FIGS. 4 (a) and 4 (b), the ingot 10 to be evaluated by the semiconductor characteristic evaluation apparatus of the present embodiment has a longitudinal surface formed by grinding the side surface of a substantially cylindrical ingot. The ingot has a flat portion extending in the direction. The ingot 10 may have a substantially polygonal cross section in addition to a substantially circular cross section. The diameter or the diagonal length of the cross section of the ingot 10 is 40 mm.
As described above, the length of the ingot is preferably 50 mm.

As shown in FIG. 4A, in one embodiment of the present invention, a semiconductor characteristic evaluation apparatus includes a movable stage 12 on which an ingot 10 is mounted, and a device extending perpendicularly to the movable stage 12. A stopper 14 that abuts against the flat portion of the ingot 10, a pusher 16 that fixes the ingot 10 to prevent displacement of the ingot 10, and that is substantially perpendicular to the flat portion of the ingot 10 through an opening 14 a of the stopper 14. An excitation light source 18 for irradiating an excitation laser beam (in a substantially horizontal direction in this embodiment) and a photodetector 20 for detecting photoluminescence light from a plane portion of the ingot 10. As shown in FIG. 4B, the opening 14a formed in the stopper 14 extends in the longitudinal direction of the ingot 10, so that excitation light can be irradiated along the longitudinal direction of the ingot 10. I have.

Further, as shown in FIG. 5, in another embodiment of the present invention, the semiconductor characteristic evaluation apparatus comprises an ingot 1
A movable stage 121 on which the ingot 10 is placed with its flat surface facing downward, a pusher 16 for fixing the ingot 10 and preventing the ingot 10 from shifting, and an ingot 10 via an opening 121a of the movable stage 121.
An excitation light source 18 that irradiates an excitation laser beam substantially perpendicularly (in this embodiment, in a substantially vertical direction) to the flat portion, and a photodetector 20 that detects photoluminescence light from the flat portion of the ingot 10. . In addition, movable stage 1
The opening 121a formed in the extension 21 extends in the longitudinal direction of the ingot 10 so that excitation light can be irradiated along the longitudinal direction of the ingot 10. In this embodiment, the distance between the excitation light irradiating surface of the ingot 10 and the excitation light source 18 and the light detection unit 20 can be easily reduced by placing the ingot 10 with the flat surface facing downward and hitting the reference surface of the movable stage 121 by its own weight. Can be kept constant.

In these embodiments, the light detecting section 20
As TRIB manufactured by JOBIN YVON SPEX
An AX-320 spectrometer and a photomultiplier having an S-1 type sensitivity curve (R176 manufactured by Hamamatsu Photonics)
7 type or R5108 type), but a detector may be appropriately selected depending on the semiconductor material to be evaluated. Further, as the excitation light source 18, an excitation light source such as an excitation light laser that emits excitation light capable of causing an inter-band absorption transition between a valence band and a conduction band of the semiconductor material to be evaluated can be used. The excitation light may be not only moved and irradiated one-dimensionally along the longitudinal direction with respect to the light irradiation surface of the ingot 10 of the compound semiconductor, but also may be configured to be moved and irradiated two-dimensionally. Further, a position information unit (not shown) for obtaining position information of the irradiation point may be provided.

Also, in these embodiments, FIG.
The entire ingot is kept in a dry nitrogen atmosphere as shown in FIG. 6A, or the portion irradiated with the spot light is purged with dry nitrogen as shown in FIG. I do.

Further, an evaluation means (not shown) for automatically evaluating the carrier concentration based on the wavelength information (or intensity information) of the photoluminescence light is provided by a method such as the embodiment of the semiconductor characteristic method described later. It may be.

Next, a description will be given of an embodiment of a semiconductor characteristic evaluation method according to the present invention for evaluating semiconductor characteristics using the above-described semiconductor characteristic evaluation apparatus.

First, the distribution of the photoluminescence spectrum is measured on the side surface of the ingot 10 using the above-described semiconductor characteristic evaluation apparatus. Next, wavelength information (or intensity information) such as the peak wavelength of the spectrum at each measurement position, the wavelength on the high energy side that is half the peak value, and the half width, and the carrier determined in advance by another method, for example, the Hall effect The carrier concentration of the ingot 10 is evaluated before slicing by using a calibration line with the concentration (see FIGS. 7, 8 and 9). When the surface condition is constant, there is also a correlation between the peak intensity and the carrier concentration, and the evaluation may be possible. It may fluctuate between ingots, stains of the cutting fluid may remain, and it is difficult to keep the surface state constant in and between the ingots. Therefore, it is preferable to evaluate using wavelength information.

[0046]

EXAMPLES Hereinafter, the method for evaluating semiconductor characteristics according to the present invention will be described in more detail with reference to examples.

Example 1 The vertical boat method was used to obtain a diameter of 8
Cylindrical S with a diameter of 2 to 84 mm and a fixed diameter of 200 mm
An i-doped (100) GaAs single crystal was grown. The obtained crystal had a peeling on the shell in part of the surface of the ingot due to the difference in thermal expansion between the container and the crystal during the cooling, and was unsuitable for optical distribution evaluation .

Next, cylindrical grinding was performed to a diameter of 79 mmφ using a # 150 grindstone, and (011)
An orientation flat surface having a width of 16 mm was formed on the surface by surface grinding. The cutting fluid at the time of grinding was wiped off with a waste cloth, but some dirt remained visually.

Thereafter, the ground surface of the ingot is placed on the reference surface of the movable stage 121 shown in FIG. 5 and irradiated with 300 mW of Ar laser light (514.5 nm) from below. Was detected to obtain a spectrum.

Next, the movable stage 121 was sequentially moved to obtain a spectrum at each point at a predetermined pitch from the seed side end to the tail side end of the ingot.

In addition, the excitation light irradiation part was 0.1 L / min.
Purged with dry nitrogen. In addition, a distribution diagram was obtained by converting the carrier concentration in the longitudinal direction of the ingot using the wavelength information of the spectrum (half-value wavelength on the high energy side, half-value width, etc.).

Then, the wafer is sliced, the wafer for Hall effect measurement is sampled, a 10 mm square sample is cut out from each wafer, and In electrodes are attached to the four corners. An ohmic alloy treatment was performed, and the carrier concentration was determined by a Van der Pauw method.

As a result, as shown in FIG. 10, the values of the two coincided within ± 5%, and it was possible to sufficiently predict the carrier concentration in the ingot state. Also, as shown in FIG. 11, similar results were obtained when the carrier concentration distribution was continuously evaluated.

[Example 2] The carrier concentration standard was 0.7 to 0.7
1.2 × 10 ¹⁸ cm ⁻³ , wafer orientation (10
0), a wafer specification A in which the finished thickness of the wafer is 600 μm, and a carrier concentration standard of 1.0 to 2.0 × 10 ¹⁸ c
m ⁻³ , the wafer plane orientation is inclined by 10 ° from (100) and the wafer specification B having a wafer thickness of 450 μm is efficiently extracted from one ingot. It cut | disconnected at the position of ¹⁸ cm- ³ .

Processing of the ingot and measurement of photoluminescence were performed in the same manner as in Example 1, the carrier concentration distribution of the ingot was predicted, and marking was made on the side of the ingot at the position where the slice condition was changed.

Based on the mark, the angle and the slice thickness are adjusted during the actual slicing, and the wafer specifications A and B are adjusted.
Was carved. After sampling the wafer at the boundary position and adjusting the sample for the Hall effect measurement, the carrier concentration was actually measured by the van der Pauw method.
× 10 ¹⁸ cm ⁻³ , and there were no wafers out of specifications A and B. Assuming that the separation is performed based on the conventional statistical prediction, 15 wafers are out of the standard and a loss is generated.

[Embodiment 3] Using a single crystal growth apparatus, S
i-doped GaAs was grown ten times. In these growths, the target carrier concentration is 0.1% at a solidification rate of the crystal of 0.1.
8 × ¹⁰ 18 cm ^{- 3} or more, in solidification ratio 0.9 2.0 × 1
This was carried out under the conditions of the charged amounts of the raw material GaAs and the dopant Si, the temperature conditions of the growth furnace, and the stirring conditions so as to be 0 ¹⁸ cm ⁻³ or less.

After the first growth, the ingot was taken out of the growth furnace and the next growth was started immediately, so that the charging conditions could not be changed. However, during the second growth, the ingot was subjected to the cylindrical grinding and surface grinding steps. As the process progressed, the same evaluation as in Example 1 was immediately performed. as a result,
It was found that the carrier concentration was higher than the target value in the latter half of the crystal growth.

At that time, the second crystal growth had a solidification rate of 0.
Since the progress was about four, the stirring conditions in the latter half of the crystal growth were corrected, and the growth was continued. As a result, the carrier concentration at the target position of the solidification rate of 0.9 was 1.93 × 10
¹⁸ cm ^-3 , and a desired value could be obtained by prompt feedback to the growth conditions.

After that, even in the ten growths, the results could be reflected in the next or at least the next growth condition, so that the yield of the carrier concentration was significantly increased to 98%.

Comparative Example 1 Crystal growth similar to that of Example 3 was performed 10 times continuously. In this case, the evaluation of the carrier concentration is as follows.
The measurement was performed by the Hall effect measurement generally performed.
Although it was possible to proceed to cylindrical grinding and surface grinding, slicing could not be performed until the processing specifications were determined. Therefore, feedback to crystal growth could be obtained after two batches at a high speed, five batches at a slow speed, and an average of three batches. After 0.5 batches, the deviation from the target that occurred during that time could not be corrected. Therefore, the yield based on the carrier concentration standard of 10 ingots was 88% on average.

Comparative Example 2 Carrier concentration of 5 × 10 ¹⁸
When measuring the photoluminescence spectrum of Si-doped GaAs in the range of cm ^{−3 to} 2.5 × 10 ¹⁸ cm ⁻³ , the excitation light irradiation unit was kept at room temperature and in air. At that time, the peak wavelength at the band edge was located at 860 to 875 nm, and the spectroscope scanned at a wavelength of 820 to 900 nm at 4 nm / sec. In the meantime, as shown by the dotted line in FIG. 3, the photoluminescence intensity changes with time, so that the excitation light intensity of the Ar laser must be reduced to 50 mW in order to suppress the intensity change during measurement to about 5% or less. Therefore, the intensity of the photoluminescence is reduced by about 1 compared with the case of Example 1, and the SN in the measurement is reduced.
The ratio has dropped. Therefore, the calculated value of the carrier concentration obtained from the wavelength information is ± 1% of the measured value of the Hall effect measurement.
An error of 0-20% occurred.

[0063]

As described above, according to the present invention, the irradiation of the excitation light in an inert gas atmosphere, preferably in a dry nitrogen atmosphere, makes it possible to reduce the room temperature even from the ground ingot surface. It is possible to obtain photoluminescence light of sufficient intensity without change over time and to predict the distribution of carrier concentration in the ingot state before slicing into a wafer based on the wavelength information and intensity information with sufficient accuracy. be able to. As a result, the loss during wafer processing can be greatly reduced, and the feedback can be quickly made to the crystal growth step.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change over time of photoluminescence light when GaAs and InP are irradiated with excitation light in the air at room temperature.

FIG. 2 is a view for explaining a spectrum error caused by a temporal change of photoluminescence light when irradiation with excitation light is performed at room temperature in the atmosphere.

FIG. 3 shows Ga in a room temperature atmosphere and a room temperature dry nitrogen atmosphere.
The figure which shows the time-dependent change of photoluminescence light at the time of irradiating excitation light to As.

FIG. 4 is a diagram schematically showing an embodiment of a semiconductor characteristic evaluation device according to the present invention.

FIG. 5 is a view schematically showing another embodiment of a semiconductor characteristic evaluation device according to the present invention.

FIG. 6 is a diagram showing an example of means for setting a dry nitrogen atmosphere in the embodiment of the semiconductor characteristic evaluation apparatus according to the present invention.

FIG. 7 is a diagram schematically showing a calibration line for calculating a carrier concentration from a relationship between a peak intensity and a carrier concentration in the semiconductor characteristic evaluation method according to the present invention.

FIG. 8 is a diagram schematically illustrating a calibration line for calculating a carrier concentration from a relationship between a half-value wavelength on the high energy side and a carrier concentration in the semiconductor characteristic evaluation method according to the present invention.

FIG. 9 is a diagram schematically showing a calibration line for calculating a carrier concentration from a relationship between a half width and a carrier concentration in the semiconductor characteristic evaluation method according to the present invention.

FIG. 10 is a diagram showing a comparison between intermittent evaluation results of the carrier concentration distribution obtained in Example 1 and evaluation results of the carrier concentration distribution obtained by the conventional method.

FIG. 11 is a diagram showing a comparison between a continuous evaluation result of a carrier concentration distribution obtained in Example 1 and an evaluation result of a carrier concentration distribution obtained by a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Ingot 12 Movable stage 14 Stopper 14a Opening 16 Pusher 18 Excitation light source 20 Light detector 121 Movable stage 121a Opening

Claims (13)

[Claims] 1. A compound semiconductor ingot from which a surface is smoothed to remove a surface-altered layer is fixed, and the valence band of the compound semiconductor is intermittently or continuously changed along the longitudinal direction of the compound semiconductor ingot. An excitation light capable of causing an inter-band absorption transition between the conduction band and the conduction band is irradiated in an inert gas atmosphere at room temperature, and at least one of wavelength information and intensity information of the photoluminescence light obtained by the irradiation of the excitation light. A method for evaluating the characteristics of a semiconductor, comprising: evaluating a carrier concentration based on the following. 2. The method according to claim 1, wherein the inert gas is nitrogen. 3. The method for evaluating characteristics of a semiconductor according to claim 1, wherein the light irradiation surface of the ingot of the compound semiconductor is cylindrically ground. 4. The method for evaluating characteristics of a semiconductor according to claim 1, wherein the light irradiation surface of the ingot of the compound semiconductor is ground. 5. The method according to claim 1, wherein the compound semiconductor is GaAs or In.
5. The method for evaluating characteristics of a semiconductor according to claim 1, wherein P is P. 6. A supporting means for supporting an ingot of a compound semiconductor whose surface has been smoothed to remove a surface altered layer, and a valence band of the compound semiconductor intermittently or continuously along the longitudinal direction of the compound ingot. Light irradiating means for irradiating an excitation light capable of causing an inter-band absorption transition between the light and the conduction band in an inert gas atmosphere at room temperature, and a light for detecting photoluminescence light obtained by the irradiation of the excitation light An apparatus for evaluating the characteristics of a compound semiconductor, comprising: a detection unit; and an evaluation unit that evaluates a carrier concentration based on at least one of wavelength information and intensity information of the photoluminescence light. 7. The semiconductor characteristic evaluation apparatus according to claim 6, wherein said inert gas is nitrogen. 8. The semiconductor characteristic evaluation apparatus according to claim 6, wherein the light irradiation surface of the compound semiconductor ingot is cylindrically ground. 9. The semiconductor characteristic evaluation apparatus according to claim 6, wherein a light irradiation surface of the compound semiconductor ingot is ground. 10. An excitation light applied to the compound semiconductor ingot is moved one-dimensionally or two-dimensionally onto a light irradiation surface of the compound semiconductor ingot, and is applied.
10. The semiconductor characteristic evaluation apparatus according to claim 6, further comprising a position information unit that obtains position information of the irradiation point. 11. The apparatus according to claim 6, further comprising holding means for holding a distance between a light irradiation surface of said compound semiconductor ingot and said light irradiation means and said light detection means constant. The semiconductor characteristic evaluation device according to any one of the above. 12. The apparatus according to claim 6, wherein the light irradiating unit irradiates the compound semiconductor ingot with excitation light from a vertically lower side or a horizontal direction.
The characteristic evaluation device according to any one of the above. 13. The method according to claim 13, wherein the compound semiconductor is GaAs or I.
The semiconductor characteristic evaluation device according to claim 6, wherein the device is nP.