JP2004311726A - Working method of single crystal ingot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a working method of a single crystal ingot for correctly evaluating the carrier concentration of the ingot before working a wafer, reducing loss generated in the working and selection of the wafer, and working the ingot into the wafer having desired physical property values. <P>SOLUTION: A first process of grinding and working a single crystal ingot 1, a second process of specifying the crystallographic surface of the ingot side face of the single crystal which is either a part where facet growth is not generated or a part from which a facet growth region is removed corresponding to the crystal growth direction of the single crystal ingot 1 and chemically etching only the front surface of the surface, a third process of irradiating the specified surface of the surface chemically etched in the second process with excitation light and evaluating the carrier concentration from a photoluminescence spectrum based on the excitation light, and a fourth process of performing slicing with the the mechanically polished surface not chemically etched in the third process as a fixed surface, are successively performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, when a wafer is obtained by processing an ingot, the carrier concentration in the single crystal is evaluated with high accuracy in a state of the ingot by removing processing damage caused by grinding, and a position to be sorted and processed is determined in advance. In addition to avoiding breakage loss due to deterioration of adhesion between the ingot and the holder during the slicing process, the generation of non-standard products during the slicing process is reduced, and quick feedback to the crystal growth process is achieved. And a method for processing a single crystal ingot, which enables:
[0002]
[Prior art]
In the advanced information communication field and the optoelectronics field, a high-frequency element, a light emitting diode (LED) and a laser diode (LD) are indispensable devices. In producing these devices, a compound semiconductor wafer is used as a substrate. For example, in the case of an LED or LD, a pn junction is formed by epitaxial growth on the wafer, and current is injected into the pn junction to emit light. Current injection into the pn junction is performed by applying a voltage to the electrodes formed on the upper surface of the grown epitaxial layer and on the rear surface of the substrate. Therefore, the physical properties of the substrate used, in particular, the carrier concentration and the resistivity, are extremely important, and are required to have values specific to the use of the device formed on the substrate. As described above, the importance of the physical properties of the substrate is not limited to the compound semiconductor at all, and the same applies to elemental semiconductors of Si and Ge. Elemental semiconductors of Si and Ge are used in integrated circuits based on bipolar elements and MOS elements, discrete elements, solar cells, and the like.
[0003]
In general, a semiconductor wafer is manufactured as a single crystal ingot by a Czochralski method, a liquid sealing Czochralski method, a horizontal boat method, a vertical boat method, a floating zone melting method (FZ method), or the like, and several hundreds by slicing. It can be obtained in the form of a wafer having a thickness of μm, and further through lapping, etching, and mirror polishing processes.
As a required characteristic value, in order to obtain a semiconductor wafer having a specific carrier concentration, a predetermined amount of a predetermined impurity (dopant) is added (doped) together with a semiconductor raw material during ingot growth. However, since the segregation coefficient of the impurity rarely becomes 1, the impurity concentration has a slope between the head and the tail in the obtained ingot. For example, when Zn is added to GaAs, since the effective segregation coefficient is about 0.4, the impurity concentration of the latter is about 3.7 times that of the former at a solidification ratio of 0.1 and 0.9. Will be. Further, when a highly volatile dopant or a dopant accompanied by a chemical reaction loss in a growth system is used, the impurity concentration may vary between growth lots.
[0004]
By the way, as a method for evaluating the electric impurity concentration, that is, the carrier concentration and the resistivity, as has been introduced in semiconductor textbooks for a long time, a method using the Hall effect represented by the Van der Pauw method, (CV method) using a capacitance-voltage characteristic by forming a diode (for example, Non-Patent Documents 1 and 2). The method using the Hall effect and the CV method are standard evaluation methods for evaluating the carrier concentration and the resistivity of a compound semiconductor.
However, in the method using the Hall effect or the CV method, since an electrode forming step must be performed on a sample to be evaluated, it is generally necessary to slice an ingot into a wafer-shaped sample piece. When the Hall effect is used, a sample is cut out from the wafer into a strip shape, a clover leaf shape, a square shape, or the like. In the case of the CV method, even if the sample is most easily prepared, the surface on which the Schottky electrode is to be formed must be clean and free of a processed layer, so that mirror polishing or mirror etching is required.
As described above, when the Hall effect or the CV method is used, after all, it is necessary to perform a process of cutting a wafer from an ingot and further form an electrode to perform measurement. This is a so-called destructive inspection, and it is practically impossible to apply it in an ingot state.
[0005]
Now, as described above, apart from the requirement for the characteristic value of the carrier concentration, the wafer orientation is intentionally shifted from the growth axis orientation of the ingot, or the wafer is cut so as to have a different thickness. Processing requirements are also diversifying. That is, the final wafer product needs to satisfy all these characteristics. However, the required range for the characteristic value of the carrier concentration is often narrower than the concentration range in the ingot. Therefore, it is necessary to cut out the slices including the processing specifications according to individual device applications.
Conventionally, in order to satisfy the necessity, a large number of data were accumulated, and based on the accumulated data, a rough outline of the boundary position of the carrier concentration was predicted, and sorting processing was performed at the time of slicing. . However, in addition to the fact that the impurity concentration in the ingot changes depending on the site due to the segregation phenomenon, and the variation width between the growth batches is overplayed, the characteristic value of the carrier concentration is different from the expected value based on the accumulated data. There are cases.
In that case, first, there is a problem that it is necessary to lose the material or additionally confirm and evaluate the required range of the carrier concentration, which is troublesome and increases the loss.
Second, it is desirable that the crystal characteristic value of the ingot be quickly fed back to the crystal growth conditions. However, in industrial production, slice processing is often performed after the range of product characteristics including processing specifications is determined, and there has been a problem that a feedback period for crystal growth conditions becomes longer.
[0006]
Therefore, the present inventor measured the photoluminescence spectrum at room temperature as a method for evaluating the carrier concentration in the ingot state, and used the wavelength information such as the peak wavelength, the half width, and the high energy side wavelength at which the half value of the peak value was obtained. An evaluation method has already been proposed (see Patent Document 1). In this method, after the surface altered layer (for example, a thermally damaged layer) during crystal growth is removed by mechanical grinding, the side surface of the ingot is irradiated with laser light and photoluminescence light is measured to reduce the carrier concentration in the longitudinal direction. evaluate. In this case, if the state of the mechanically ground surface is constant, the carrier concentration distribution is evaluated with sufficient accuracy.
[0007]
[Patent Document 1]
JP-A-2002-148191 (FIG. 5, paragraph 0045)
[Non-patent document 1]
Edited by Takashi Katoda, "Semiconductor Evaluation Technology", Sangyo Tosho, 1989, p. 221-235
[Non-patent document 2]
ASTM Standard F76-86, Vol. 10.05, p. 117, 1991
[0008]
[Problems to be solved by the invention]
However, the present inventor has found a problem that the correlation between the wavelength information of photoluminescence and the carrier concentration in Patent Document 1 is not always maintained and may be broken. That is, when there is a change with time such as wear of the grinding wheel, the state of the processed layer on the ground surface cannot be maintained with good reproducibility, and the correlation between the wavelength information of photoluminescence and the carrier concentration is broken. .
[0009]
As an explanation of this problem, the effect of processing damage on the photoluminescence spectrum will be described with reference to experimental results.
FIG. 8 is a diagram showing a wafer surface that has been subjected to mechanical damage to a chemically mirror-polished wafer. As the wafer, a Si-doped GaAs wafer from which processing damage introduced during slicing or lapping has been completely removed is used. This mechanical damage is caused by intentionally rubbing the wafer surface with # 500 sandpaper. The mechanical damage changes the manner of giving the mechanical damage by changing the magnitude of the rubbing force at each of the points A, B, C, and D in FIG.
[0010]
FIG. 9 is a graph showing the half-width of the photoluminescence spectrum at each different point in the diameter direction of the wafer. In FIG. 9, the white circles indicate the half widths before the mechanical damage is introduced, and the black circles indicate the half widths after the mechanical damage is introduced. Note that A to D in FIG. 9 correspond to points A, B, C, and D in FIG. As can be seen from FIG. 9, before the introduction of the mechanical damage, the half-value width of each portion on the wafer was the same, but after the introduction of the mechanical damage, the portions where the mechanical damage was given, that is, A, FIG. At each of points B, C, and D, the half width of the photoluminescence spectrum increases. Also, the amount of increase is different in each of A, B, C, and D.
[0011]
FIGS. 10A and 10B are graphs showing the photoluminescence spectra of the wafer of FIG. 8, wherein FIG. 10A shows the photoluminescence spectra at point A in FIG. 8 and FIG. 10B shows the photoluminescence spectra at point D in FIG. In the figure, open circles indicate photoluminescence intensity before mechanical damage is introduced, and black circles indicate photoluminescence intensity after mechanical damage is introduced. FIG. 10 shows that the introduction of mechanical damage lowers the photoluminescence intensity, shifts the peak wavelength, and increases the half width.
[0012]
By the way, when the ingot is subjected to cylindrical mechanical grinding or planar mechanical grinding using a diamond grindstone or the like, a processing damage layer called a crush layer is formed on the crystal processing surface. Although the photoluminescence spectrum shape changes due to the formation of the processing damage layer, if the processing damage is constant between processing batches, the reproducibility of the photoluminescence spectrum shape corresponding to the carrier concentration is secured. Will be. However, it is not practically possible to keep the processing damage constant over a long period of time due to the effects of wear of the diamond grindstone, change over time of the coolant liquid, flow rate fluctuation, and the like. Therefore, there is a problem that it is difficult to ensure reproducibility of the photoluminescence spectrum shape corresponding to the carrier concentration.
[0013]
By the way, when the evaluation of the carrier concentration distribution of the ingot is finished, based on the result of the evaluation, slicing is performed in accordance with a predetermined processing standard to obtain a thin wafer. At this time, the ingot is fixed to a carbon or ceramic fixing table with wax or an adhesive to prevent the wafer from escaping at the end of slicing. However, if the adhesiveness between the ingot and the fixed base is insufficient, the wafer is detached from the fixed base just before or at the end of slicing. As a result, not only is it caught by the cutting blades and wires in motion and dissipated, but also if it scatters, it also damages the wafer around it, reducing the processing yield. is there.
[0014]
Further, in order to remove processing damage caused when the ingot is mechanically ground, it is preferable to etch the entire ingot for evaluation of photoluminescence, but the surface is smoother than the mechanically ground surface. There is a problem that the anchor effect is weakened, the adhesion between the wax and the adhesive and the surface of the ingot is deteriorated, and as described above, the processing yield during slicing is reduced.
[0015]
When evaluating the carrier concentration using the photoluminescence method in the ingot state, it is necessary to remove the processing damage on the mechanically ground surface in order to ensure reproducibility. Although there is a method of performing chemical etching, the method of chemical etching is simpler and more practical. On the other hand, when slicing the ingot, on the other hand, in order to secure the adhesion to the fixing table, the fixing portion of the ingot preferably has a mechanically ground surface and is not preferably subjected to chemical etching. As described above, the preferred method in the photoluminescence evaluation in the ingot state and the preferred method in the subsequent wafer slicing do not always coincide with each other, and both must be satisfied.
[0016]
In view of the above problems, the present invention can correctly evaluate the carrier concentration of an ingot of a semiconductor single crystal before processing a wafer, and reduce a loss caused by processing selection of a wafer, for example, a loss due to a nonstandard specification or a damage during a slice processing. It is another object of the present invention to provide a semiconductor ingot processing method capable of processing an ingot into a wafer having desired physical properties.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, a method for processing a single crystal ingot according to the present invention comprises a first step of mechanically grinding the single crystal ingot, a portion where facet growth does not occur depending on the crystal growth orientation of the single crystal ingot, and a facet. A second step in which the crystallographic plane of the side face of the ingot of the single crystal, which is one of the portions excluding the growth region, is specified, and only the surface of the ingot is chemically etched, and the surface chemically etched in the second step. A third step of irradiating the specified surface with excitation light and evaluating a carrier concentration from a photoluminescence spectrum based on the excitation light, and performing a slicing process using the mechanically ground surface not subjected to chemical etching as a fixed surface in the third step. The fourth step to be performed is sequentially performed.
[0018]
In the above configuration, when the growth plane orientation of the single crystal ingot is set to [−100], in the first step, the plane on which the plane ground surface is formed by mechanical grinding is the (0-11) plane and the (01-) plane. 1) A plane within ± 5 ° from any one of the planes, and in the second step, the crystallographic planes are (001) plane, (0-10) plane, (00-1) plane. ), (010), (0-11), and (01-1) planes within ± 90 °, preferably ± 60 ° from any one of the planes. The chemical etching is performed only on the single crystal side surface region, and the (001) plane, the (0-10) plane, the (00-1) plane, and the (010) plane of the chemically etched portion in the third step. ), Any of (0-11) and (01-1) planes within ± 20 ° from any of the planes The surface of the side surface of the ingot limited to any range within ± 5 ° from the surface is irradiated with the excitation light.
[0019]
Further, the growth orientation of the single crystal ingot is an orientation equivalent to [-100], and in the first step, the plane forming the plane ground surface is a (0-11) plane and a (01-1) plane. A plane within ± 5 ° from a plane equivalent to any one of the above, and in the second step, the crystallographic plane is (001) plane, (0-10) plane, (00-1) plane, A plane within ± 90 °, preferably ± 60 ° from a plane equivalent to any of the (010) plane, the (0-11) plane, and the (01-1) plane; The plane irradiated with the excitation light is ± 20 from a plane equivalent to any of the (001), (0-10), (00-1) and (010) planes of the chemically etched portion. Either within ± 5 ° or within ± 5 ° from a plane equivalent to any of the (0-11) and (01-1) planes Characterized in that it is a surface of limited ingot side.
[0020]
Furthermore, when the growth plane orientation of the single crystal ingot is any one of [1-1-1-1] and [111], in the first step, the surface on which the plane ground surface is formed by mechanical grinding is changed to (1-1-1). 10), (0-11), (-101), (-110), (01-1) and (10-1) specified as a plane within ± 5 ° from any of the planes At the same time, in the second step, chemical etching is performed only on a single crystal side surface region within ± 90 °, preferably within ± 60 ° with respect to the surface ground surface. ± 15 from any of the (1-10), (0-11), (-101), (-110), (01-1), and (10-1) planes The irradiation of the excitation light is performed on the surface of the side surface of the ingot limited within the range of °.
[0021]
Further, the growth orientation of the single crystal ingot is an orientation equivalent to one of [-1-1-1] and [111], and in the first step, the surface forming the surface ground surface is (1). A plane within ± 5 ° from a plane equivalent to any of the (-10) plane, (0-11) plane, (-101) plane, (-110) plane, (01-1) plane, and (10-1) plane In the third step, the surface to be irradiated with the excitation light is the chemically etched surface (1-10), (0-11), (-101), or (-101). (110), (01-1), and (10-1). The surface of the side surface of the ingot limited to within ± 15 ° from a plane equivalent to the plane.
[0022]
The crystal structure of the single crystal ingot is preferably one of a diamond type and a zinc blende type.
In addition, an etchant used when performing chemical etching on a specified region of the single crystal side surface is hydrochloric acid, nitric acid, a mixed solution of hydrochloric acid, nitric acid, and water, a mixed solution of sulfuric acid, hydrogen peroxide, and water, A mixture of hydrochloric acid, hydrogen peroxide and water, a mixture of hydrofluoric acid, hydrogen peroxide and water, a mixture of acetic acid or water, hydrofluoric acid and nitric acid, a mixture of ammonia water, hydrogen peroxide and water Liquid, a mixed solution of caustic soda, hydrogen peroxide solution and water, potassium hydroxide, hydrogen peroxide solution and water, or a mixed solution of bromine or iodine and methanol is preferable.
[0023]
Further, the single crystal ingot is preferably GaAs doped with any of Si, Te, Se, S, Zn and C, or InP doped with any of Se, Te, Sn, S, Zn and Cd. Which is either
Further, the single crystal ingot is preferably one of GaP, GaSb, InSb, and InAs doped with any of Si, S, Se, Te, Zn, and Mg.
The single crystal ingot is preferably any one of ZnSe, ZnTe, and CdTe doped with any of Li, Al, Ga, B, N, P, As, Sb, and Cl.
Further, the single crystal ingot is preferably one of Si and Ge doped with any of B, Al, Ga, P, As and Sb.
[0024]
In the chemical etching in the second step, preferably, the side surface of the ingot is held via a holder on a height adjusting table provided on the bottom surface of the etching solution tank, and the height of the etching solution surface or the height This is done by adjusting the height of the adjustment table. Further, when performing the chemical etching in the second step, it is desirable to mask a region not to be etched with an adhesive tape or a coating type masking agent.
[0025]
According to the present invention, when evaluating the carrier concentration in the growth direction of the ingot by the photoluminescence method, the excitation light irradiation is specified on a specific crystallographic plane. An operation for removing a processing damage layer by chemical etching is performed to remove processing damage on the mechanically ground surface only on the specified surface. On the other hand, the fixing surface at the time of ingot slicing is defined as a surface that does not include the chemically etched surface, thereby ensuring adhesion to the ingot fixing table and preventing processing loss at the time of slicing. Therefore, it is possible to simultaneously solve the problem of accurate and reproducible evaluation of the carrier concentration and the problem of processing damage failure during ingot slicing.
[0026]
Further, according to the present invention, as a method of chemically etching only a specified portion of the side surface of the ingot, the direction of the ingot to be immersed in the etching solution is determined, and at least the height of the ingot in the etching solution surface or the etching solution is determined. Adjust one. At this time, in the case where the etching solution touches other parts when the ingot is put into or taken out of the etching tank, or in the case where etching is caused by vapor from the etching solution, it is pre-etched with an adhesive tape or the like. By masking other than the specific surface, only the specific surface can be etched.
[0027]
Further, according to the present invention, when irradiating the specified surface of the single crystal ingot with excitation light for photoluminescence evaluation, in order to position the single crystal ingot with the optical system of the photoluminescence evaluation device, the diameter of the single crystal is increased in advance. Utilize the properties of habit lines generated at the parts and side surfaces, or use the relationship between the shape and orientation of the etch pits generated by the selective chemical etching characteristics of the sample fragment cut out from the end face, and further determine the direction of X-ray diffraction and X-ray diffraction. To determine the crystallographic orientation using a method, to mark a part of the ingot and align it with the optical system, or when performing surface grinding of the ingot, the surface ground surface and the optical system Positioning may be performed based on the angle relationship described above.
[0028]
Also, if the surface fixed by wax or adhesive between the ingot and the ingot fixing base during wafer processing slicing is a mechanically ground surface that is not subjected to etching, the wafer may fall off during slicing and damage to peripheral wafers due to falling off. Can be prevented.
It is necessary to change the center angle of the circumference of the ingot bonded to the ingot fixing table depending on the thickness and brittleness of the wafer to be sliced, but it is generally about 50 to 120 °. By setting the side surface of the ingot subjected to chemical etching to within ± 90 ° with respect to the specified surface, 180 ° or more of the side surface can be maintained as a mechanically ground surface, but depending on the off angle and direction at the time of slicing. Since there is a possibility that an etched portion may be included in a part of the fixed surface, it is preferable that the fixed surface be within ± 60 ° with respect to the specific surface. In this case, since 240 ° or more of the side surface of the ingot remains a mechanically ground surface, the inclusion of the etched portion on the surface fixed by the wax or the adhesive regardless of the off angle and direction at the time of slicing is included. Can be avoided.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a single crystal ingot property evaluation processing method according to the present invention will be described in detail with reference to the drawings.
First, a GaAs single crystal ingot having a crystal growth orientation of [-100], which is a target for processing the characteristics of the single crystal ingot according to the present invention, will be described. FIG. 1A is a diagram schematically illustrating a GaAs single crystal ingot having a crystal growth orientation of [−100], and FIG. 1B is a schematic diagram of a facet growth region in a (100) wafer of a crystal cross section. is there. 1B shows the facet growth region, the solid line shows the outer periphery of the ingot in a state where the crystal is grown, and the dotted line shows the outer periphery of the ingot after being ground in the first process described later. Is shown.
An index that gives a certain direction in the crystal is usually expressed as [hkl], and a plane index is expressed as (hkl). When a certain plane intersects the crystal on the negative side with respect to the origin, the index becomes Although a negative sign is added above the index, a negative sign “-” is added before the index for convenience in the present specification. The same applies to the case of indicating the azimuth.
[0030]
In a GaAs single crystal ingot having a crystal growth orientation of [-100], habit lines are observed in four directions on the crystal surface as shown in FIG. On the side surface of the crystal, a habit line appears on a plane in the [011], [0-11], [0-1-1] and [01-1] directions (the [0-11] direction is not shown), and In the diameter part, the side connected to the crystal habit lines [011] and [0-1-1] is longer than the crystal habit line connected to [0-11] and [01-1]. The approximate orientation of the crystal, that is, the crystallographic plane of one side surface of the ingot can be determined by observing the appearance based on the difference in the length.
[0031]
Next, a first process of the method for processing the characteristics of a GaAs ingot shown in FIG. 1A will be described.
In the first step, mechanical grinding of the ingot is performed.
First, the deteriorated layer on the outermost surface of the ingot generated during the production of the ingot is removed by cylindrical grinding or surface grinding.
Next, in general, in the case of a semiconductor wafer, it is a circular wafer having a uniform diameter, and orientation flat processing is performed to determine the crystallographic orientation of the wafer. For this purpose, the grown ingot 1 is machined to have a constant diameter by cylindrical mechanical grinding, and the orientation flat portion is subjected to plane mechanical grinding. For example, a Si-doped GaAs single crystal ingot having a growth orientation of [-100] is subjected to constant diameter processing by cylindrical mechanical grinding, and then the [0-11] orientation of the side face of the ingot is determined by the above-described positional relationship of crystal habit lines and X-ray diffraction. And perform plane mechanical grinding on the plane of (0-11) ± 5 °. The surface ground surface may be the (01-1) surface on the opposite side. The facet regions on the [0-11] and [01-1] sides are often only regions having a few mm of the pole surface of the crystal, and the facet regions are removed by cylindrical mechanical grinding and / or plane mechanical grinding.
The GaAs single crystal whose crystal growth direction is [−100] shown in FIG. 1A has a size indicated by a solid line in FIG. It will be processed to the size indicated by. However, in the facet area indicated by oblique lines in FIG. 1B, [011] and [0-1-1] are larger than [0-11] and [01-1]. The facet regions of [011] and [0-1-1] cannot be completely removed by the mechanical grinding.
[0032]
Next, a second process of the method for evaluating the properties of a single crystal ingot according to the present invention will be described.
In the second step, the crystallographic plane of the side face of the ingot of the single crystal is specified, and only the surface of the ingot is subjected to chemical etching. In this chemical etching, the excitation light irradiation is specified on a specific crystallographic plane in order to accurately evaluate the carrier concentration in the growth direction of the ingot by a photoluminescence method in a third process described later. Therefore, chemical etching is performed only on the specified surface to remove the processing damage on the mechanically ground surface. At this time, when evaluating the carrier concentration distribution in the ingot growth direction using the photoluminescence method, the surface to be irradiated with the excitation light according to the crystal growth direction can be accurately determined by crystallographically specified surface. A high carrier concentration can be obtained. The specified surface may be any of a portion where facet growth does not occur and a portion where the facet growth region is removed according to the crystal growth orientation of the single crystal ingot, as described later.
[0033]
For example, when the ingot growth direction is [−100], as shown by hatching in FIG. 1 (b), generally, [0-11], [0-11], [0-11] on the [011] and [0-1-1] sides. The facet growth region is larger than that on the [01-1] side and penetrates into the crystal. In this facet region, the growth state is different from that of the other portion, and the state of capturing impurities is different, so that the carrier concentration is different from that of the other region. Therefore, when the carrier concentration distribution in the growth direction of the ingot is evaluated by the photoluminescence method, in order to avoid the facet growth region, the specified surface of the ingot, ie, (001), (0-10), (00) -1) It is necessary to irradiate the excitation light within a range of ± 20 ° from either plane.
In addition, a single crystal side surface region within ± 90 ° from any one of (001), (0-10), (00-1), and (010), preferably within ± 60 ° with respect to each surface. Preferably, chemical etching is performed.
Further, the facet regions on the [0-11] and [01-1] sides are often only regions having a depth of several mm, which are the extreme surfaces of the crystal, and the facet regions are formed by cylindrical mechanical grinding and / or plane mechanical grinding. Under the removed conditions, chemical etching is performed for mechanical grinding damage within a range of any of (0-11) ± 90 ° and (01-1) ± 90 °, preferably within a range of ± 60 °. It may be.
This chemical etching is performed to remove machining damage on the mechanically ground surface that has been mechanically ground in the first step. However, in the fourth step to be described later, when slicing the ingot, the ingot fixing table is used. In order to secure the adhesion to the ingot, the surface to be fixed to the ingot fixing table is excluded from the surface on which the chemical etching is performed.
[0034]
Here, the etching method will be described.
FIG. 2A is a diagram showing an embodiment of a method of immersing the ingot in an etching solution during the etching of the ingot in the second step, and FIG. 2B is a diagram showing an embodiment of actually immersing the ingot in the etching solution. is there. As shown by the thick arrow in FIG. 2A, for example, the ingot 1 is immersed in the etching solution 2 with the [001] direction of the ingot 1 facing downward. At this time, an ingot holding table 3 as shown in FIG. 2B is used so that the lower portion of the ingot 1 is appropriately supported in the etching solution 2 so as to be properly etched. Is preferred.
Further, the level of the etching solution 2 is adjusted or the height of the ingot holding table 3 is adjusted so that the chemical etching is limited to the side surface region within (001) ± 90 °, preferably ± 60 °. Is adjusted with the height adjustment table 4. At this time, a region where etching is not performed may be masked by a coating type masking agent such as an adhesive tape or picein. Here, as the GaAs etching solution 2, a mixed solution of hydrochloric acid and nitric acid at a volume ratio of 1: 1 is used, and the etching is carried out at room temperature for 5 minutes. When the etching is completed, the ingot 1 is taken out of the etching solution tank 5, and the etching solution is immediately sufficiently washed off with pure water and dried by nitrogen or air blow.
The composition of the etching solution 2 may be another composition of the etching solution, and the etching conditions such as the solution temperature and the etching time may be set as appropriate so that mechanical grinding damage is sufficiently removed.
Thus, the surface after etching has a damaged layer removed by mechanical grinding and has a pseudo-mirror surface, whereas the portion not immersed in the etching solution 2 maintains the roughened state of mechanical grinding. ing.
[0035]
Next, the third step of the method for evaluating the properties of a single crystal ingot according to the present invention will be described.
In the third step, the specified crystallographic surface of the etched surface is irradiated with excitation light, and the carrier concentration in the ingot state is measured at room temperature based on the wavelength information of the photoluminescence spectrum.
FIG. 3 is a conceptual diagram of the movable stage 6 which is a part of the photoluminescence evaluation device. The movable stage 6 includes an X stage 61, a Y stage 62, and a Z stage 63. The X stage 61, the Y stage 62, and the Z stage 63 can be independently set at predetermined positions in the directions X, Y, and Z indicated by arrows in the drawing by driving devices such as stepping motors 61a and 62a. The photoluminescence evaluation device (not shown) includes a light source for excitation light, a measurement detector for photoluminescence light, and the like.
[0036]
The measurement and evaluation of photoluminescence of an ingot by the photoluminescence evaluation device will be described.
First, the ingot 1 is set on the movable stage 6. Then, in order to obtain photoluminescence light, an ingot for specifying the excitation light Lp having energy larger than the forbidden band width of the semiconductor crystal to be evaluated within a portion etched in the second process, for example, within (001) ± 20 °. Irradiate on the side. When the ingot 1 is made of GaAs, an Ar laser Lp having a wavelength of 514.5 nm (= 2.41 eV) having an energy larger than the GaAs band gap (band gap: about 1.43 eV at room temperature) is used as the excitation light Lp. Can be.
The angle for irradiating the excitation light to a prescribed crystallographic position is determined based on an angle from the plane-ground (0-11) plane or a mark obtained in advance from the positional relationship of the crystal habit line. It is only necessary to determine and set the ingot 1 on the movable stage 6. Then, after performing the optical adjustment of the excitation light irradiation position and the photoluminescence light focusing system, the ingot 1 is moved in a direction perpendicular to the focusing system at intervals of several mm pitch, that is, the movable stage 6 is moved. Then, a photoluminescence spectrum is measured at each point.
[0037]
The wavelength information of the photoluminescence spectrum at each of the measured points, that is, the peak wavelength of the spectrum, the wavelength on the high energy side that is half the peak value, the half width, and the like are obtained in advance by another method, for example, the Hall effect. By using the calibration line with the carrier concentration, the carrier concentration is calculated, and the distribution of the carrier concentration in the growth longitudinal direction can be obtained (see Patent Document 1). At this time, by marking the measurement start position and / or the measurement end position, the positional relationship with the obtained longitudinal carrier concentration distribution becomes clear, and the sorting at the time of slicing can be easily performed.
The irradiation range of the excitation light is not limited to the side surface of the ingot specified within (001) ± 20 °, but the portions actually etched in the second step (001), (0-10), (00) -1), any range of a plane within ± 20 ° from any of the planes of (010) or a plane within ± 5 ° of any of the planes of (0-11) and (01-1) May be.
[0038]
Next, a fourth step of the method for evaluating single crystal ingot characteristics according to the present invention will be described.
The fourth step is a step of slicing the ingot into wafers. More specifically, the wafer is sliced while the mechanically ground surface that has not been etched is fixed to an ingot fixing base with wax or an adhesive.
The inner peripheral slicer 7 used in the fourth step will be described. FIG. 4 is a schematic perspective view schematically showing wafer slicing processing by the inner peripheral blade slicer 7. The inner peripheral blade slicer 7 has an ingot holding portion 70 to which an ingot fixing base 71 for holding the ingot 1 can be attached, and an inner peripheral blade 74 fixed to a table or the like (not shown).
[0039]
The ingot holding portion 70 has a gonio structure, and has a movable structure in which the X-direction tilt 72 and the Y-direction tilt 73 can be controlled in the directions indicated by the two-way arrows E and F, respectively. Further, the ingot holding section 70 is moved in the slice pitch feed direction indicated by the arrow G in the drawing, and the position of the ingot 1 with respect to the inner peripheral blade 74 can be adjusted.
[0040]
Further, the ingot fixing base 71 is made of carbon or the like. The ingot is fixed to the ingot fixing base 71 using a wax or an epoxy-based adhesive. At this time, in the above-mentioned example, since a portion within (001) ± 90 °, preferably within ± 60 ° of the side surface of the ingot 1 has been subjected to chemical etching, another mechanically ground surface is used.
The inner peripheral blade slicer 7 is configured as described above, and after the position of the ingot 1 to be cut and the slice pitch are accurately adjusted by the gonio structure of the ingot holding section 70, the ingot holding section 70 is moved by the arrow shown in the drawing. By moving in the direction of H, the ingot 1 can be sliced.
[0041]
In the fourth step, it may be better to use a multi-wire saw 8 instead of the inner peripheral blade slicer 7. FIG. 5 is a schematic perspective view schematically showing a wafer slicing process using the multi-wire saw 8.
The multi-wire saw 8 includes an ingot fixing base 81 that holds the ingot 1, an ingot fixing stage 83 having a gonio mechanism 80, and a multi-wire 84.
[0042]
The ingot fixing base 81 is fixed to an ingot fixing stage 83 by an ingot fixing base clamp 82. The multi-wire 84 has a so-called multi-wire structure in which a large number is provided in parallel at intervals corresponding to the pitch so that a slice pitch of the ingot 1 to be cut can be obtained. The reciprocating motion is performed in the illustrated arrow L direction (X-axis direction) while feeding the wire 84.
The gonio mechanism 80 built in the ingot fixed stage 83 can adjust the cutting position of the ingot 1 with respect to the multi-wire 84. As shown, although the rotation tilt around the Z axis indicated by the arrow I can be increased, the adjustment amount of the rotation tilt around the X axis indicated by the arrow J and the Y axis indicated by the arrow K, that is, in the longitudinal direction of the ingot 1 The structure has a small amount of adjustment for the in-plane rotation of the ingot growth axis in the vertical and ingot directions. The method of fixing the ingot 1 to the carbon ingot fixing base 81 is the same as that of the inner peripheral blade slicer 7 in FIG.
The wire saw 8 is configured as described above, and moves the ingot 1 vertically in the direction of the arrow M (Z-axis direction) as shown in the figure, and supplies the abrasive slurry to the cut portion of the ingot 1 to feed the multi-wire 84. The ingot 1 can be sliced by the reciprocating motion in the direction of the arrow L accompanied by. At this time, because of the multi-wire structure, a number of wafers corresponding to the number of the multi-wires 84 can be cut at a time.
[0043]
Next, a method for slicing a desired plane will be described with reference to an example.
(Slice example 1)
When manufacturing a substrate for an AlInGaP-based semiconductor laser or LED, a wafer having a surface inclined from the (100) orientation grown GaAs single crystal ingot 1 by, for example, 10 ° from the (100) to the (111) A direction. Need to be cut out. When the multi-wire saw 8 is used, it is necessary to rotate the ingot fixing stage 83 around the Z axis by 10 °, so that the adhesive fixing surface of the ingot has the (01-1) surface as shown in FIG. Must be fixed in the center.
(Slice example 2)
In the case of manufacturing a substrate of an AlGaAs surface emitting laser, it is necessary to cut out a wafer having a surface inclined from the (100) plane by about 2 to 5 ° in the (1-10) direction. In this case, FIG. As shown in b), the adhesive fixing surface of the ingot needs to be fixed around the (00-1) plane.
6 (a) and 6 (b) also show the azimuth relationship of the ingot bonding and fixing surface and the positional relationship of the etched surface, and the dotted line shows the range to be subjected to chemical etching. In addition, the thick dotted line indicates a range which is a particularly preferable target of chemical etching.
[0044]
As described above, since the bonding surfaces of the ingot fixing bases 71 and 81 and the ingot 1 are not chemically etched, that is, are mechanically ground, the wafer is maintained in a state where detachment of the wafer during slicing can be avoided. Slicing can be performed.
[0045]
As described above, according to the present invention, since the carrier concentration distribution of the semiconductor single crystal ingot is accurately evaluated before performing the wafer processing, the non-standard loss of the carrier concentration range caused by the conventional processing selection is significantly reduced. can do. At the same time, there is no processing loss at the time of slicing as a wafer, so that the loss in the sorting processing can be significantly reduced.
[0046]
In the above description, the case where the crystal growth direction is [-100] has been described. However, the direction in which the crystal growth direction is [-100], that is, [100], [010], and [0-10]. , [001], and [00-1], the surface to be ground in the first process, the surface to be etched in the second process, and the surface to be irradiated with the excitation light in the third process are the above-described surfaces, respectively. It may be equivalent to.
[0047]
The same is true even if the crystal grows in another crystal growth direction. For example, when the growth surface orientation of the ingot is any one of [-1-1-1] and [111] and a surface equivalent thereto, in the first step, a surface ground surface is formed by mechanical grinding. The plane is defined as any one of the (1-10) plane, the (0-11) plane, the (-101) plane, the (-110) plane, the (01-1) plane, and the (10-1) plane, and equivalents thereof. Specify a plane within ± 5 ° from the plane.
Next, in the second step, chemical etching is performed on the single crystal side surface region within ± 90 °, preferably ± 60 °, of the surface ground surface.
Next, in the third process, the (1-10), (0-11), (-101), (-110), (01-1), and (10-1) -1) Irradiation of excitation light is performed on any of the surfaces and the surface of the side surface of the ingot limited to within ± 15 ° from a surface equivalent thereto.
[0048]
The crystal structure of the single crystal ingot may be a diamond type single crystal ingot or a zinc blende type single crystal ingot. Some examples include GaAs doped with any of Si, Te, Se, S, Zn, and C, or InP doped with any of Se, Te, Sn, S, Zn, and Cd.
Also, GaP, GaSb, InSb, or InAs doped with any of Si, S, Se, Te, Zn, and Mg may be used.
Alternatively, ZnSe, ZnTe, or CdTe doped with any of Li, Al, Ga, B, N, P, As, Sb, and Cl may be used.
Further, Si or Ge doped with any of B, Al, Ga, P, As and Sb may be used.
[0049]
Further, the etching solution may be determined according to the type of the single crystal of the ingot. To give some examples, when the ingot is GaAs or InAs single crystal, a mixed solution of hydrochloric acid, nitric acid and water, a mixed solution of sulfuric acid, hydrogen peroxide and water, hydrochloric acid or hydrofluoric acid and peroxide A mixture of hydrogen water and water, a mixture of ammonia water, hydrogen peroxide and water, a mixture of caustic soda, hydrogen peroxide and water, a mixture of potassium hydroxide, hydrogen peroxide and water, and bromine Any of the mixed solutions with methanol may be used as the etching solution.
When the ingot is a single crystal of InP or GaP, one of a mixture of hydrochloric acid, hydrogen peroxide and water, a mixture of hydrochloric acid, nitric acid and water, and a mixture of bromine and methanol are etched. It may be used as a liquid.
When the ingot is GaSb or InSb, any one of a mixed solution of acetic acid or water, hydrofluoric acid, and nitric acid, a mixed solution of nitric acid, hydrochloric acid, and water, and a mixed solution of bromine or iodine and methanol, It may be used as an etching solution.
When the ingot is made of ZnSe, any of a mixture of iodine and methanol and a mixture of nitric acid, hydrochloric acid and water may be used as the etching solution.
When the ingot is CdTe or ZnTe, any of a mixture of hydrofluoric acid, nitric acid and water, a mixture of hydrochloric acid, nitric acid and water, and hydrochloric acid may be used as the etching solution.
When the ingot is Si or Ge, a mixed solution of acetic acid or water, hydrofluoric acid, and nitric acid may be used as the etching solution.
[0050]
Next, examples and comparative examples will be described.
(Example 1)
As an example in which photoluminescence measurement can be accurately performed according to the present invention, a case where an ingot side surface where facet growth does not occur in the second step is used as an etching surface, and the etched surface is irradiated with excitation light in the third step is described in the first embodiment. And It is assumed that the following specifications A and B are required for the GaAs wafer.
The required specification A has a carrier concentration range of 7.0 × 10 ¹⁷ ~ 1.2 × 10 ¹⁸ cm ^-3 The plane orientation was inclined from (100) to the [011] direction by 10 ± 0.1 °, and the slice thickness of the wafer was 750 μm.
In the required specification B, the carrier concentration range is 1.0 to 2.0 × 10 ¹⁸ cm ^-3 The plane orientation was inclined from the (100) to the [011] direction by 10 ± 0.1 °, and the slice thickness of the wafer was 570 μm.
[0051]
As a first step, a Si-doped GaAs single crystal ingot having a diameter of 82 to 84 mm and a growth orientation of [-100] grown by a vertical boat method was cylindrically ground and subjected to a constant diameter processing of 79 mm in diameter. Next, the [0-11] orientation of the side surface of the ingot is determined by the positional relationship of the habit lines of the diameter-increased portion and X-ray diffraction, and a plane grinding process of 12 mm width is performed on the (0-11) ± 0.5 ° plane. Was given. Here, the habit line of the (011) plane is longer than the habit line of the (0-11) plane. The (001) plane is an intermediate position between the (011) plane and the (0-11) plane.
[0052]
As a second step, the (001) face of the side face of the ingot is inserted into an etching solution having a volume ratio of nitric acid and hydrochloric acid of 1: 1 with the (001) ± 60 ° range only. Etching was performed at room temperature for 5 minutes. The ingot holding table 3 and the etching solution level shown in FIG. 2B are adjusted to etch only the specified portions. After the completion of the etching, the ingot 1 was taken out of the etching liquid tank 5, immediately washed with pure water, and dried by blowing nitrogen.
[0053]
As a third step, the ingot 1 was set on the movable stage 6 of the photoluminescence evaluation device so that the irradiation of the laser excitation light was (001) ± 5 ° in the growth axis direction on the side surface of the ingot (see FIG. 3). . At this time, the angle between the (0-11) plane, which is the plane ground plane, and the laser beam irradiation plane was set to 45 °. A mark was placed on the measurement start position, and the photoluminescence spectrum was measured at each measurement point while moving the movable stage 6 in the direction of the growth axis of the ingot at a measurement interval of 5 mm. Then, the carrier concentration distribution in the growth axis direction of the ingot 1 was obtained using the correlation information between the wavelength information and the carrier concentration.
[0054]
FIG. 7 is a perspective view schematically showing the result of the carrier concentration distribution of the GaAs ingot of Example 1. As shown in the figure, the seed side 1a of the crystal of the GaAs ingot 1 is 7.1 × 10 ¹⁷ cm ^-3 1.9 × 10 on the tail side 1b. ¹⁸ cm ^-3 Met. Therefore, in order to process and collect the wafer with the highest yield, the carrier concentration is set to 1.1 × 10 ¹⁸ cm ^-3 The processing conditions were changed at the position 1c (see FIG. 7).
[0055]
That is, in the required specification A, the carrier concentration range is 7.0 × 10 ¹⁷ ~ 1.2 × 10 ¹⁸ cm ^-3 Therefore, as shown in FIG. 7, the carrier concentration from the seed side 1a of the crystal of the GaAs ingot 1 is 1.1 × 10 ¹⁸ cm ^-3 The region of the ingot 1 up to 1c, which is the position of the ingot 1, is processed by slicing (see FIG. 7A).
Further, in the required specification B, the carrier concentration range is 1.0 to 2.0 × 10 ¹⁸ cm ^-3 Therefore, the remaining ingot 1 region, that is, the ingot 1 region from 1c in FIG. 7 to the tail side 1b is obtained by slicing (see FIG. 7B).
[0056]
As a fourth process, since the carrier concentration distribution in the growth axis direction is known in advance, a mark is placed on the ingot side surface position 1c (hereinafter, referred to as the corresponding position) corresponding to the value, and the ingot fixing base 71 for slicing is marked. Then, the wax was fixed so that the (01-1) plane was the center (see FIG. 6A).
The ingot fixing base 71 was held on the inner peripheral blade slicer 7 and surfaced using an X-ray cut surface inspection apparatus, and continuous slicing was started at a pitch in which the required margin was added to the required specification B. The number of slices was calculated in advance from the distance from the previously marked position, and the slice processing was automatically interrupted once at the corresponding position 1c. Next, slicing in consideration of the cutting margin was continued in accordance with the required specification A, and the target sorting was performed.
[0057]
As a result, since the effective length of the crystal was 183 mm and the corresponding position 1c was 103 mm from the tail side, 114 wafers for the specification B, 74 wafers for the specification A, and 188 wafers for convenience were obtained. At this time, since the fixed state of the slice fixing base 71 and the fixed portion of the slice wafer was ensured, no processing damage occurred during slicing. When the carrier concentration of the wafer at the corresponding position 1c, which is the boundary of the sorting process, was determined by the Hall effect evaluation, ¹⁸ cm ^-3 There was no deviation from the two required specifications A and B.
[0058]
(Example 2)
In the second embodiment, the facet growth region is completely removed in the first process, the side surface of the ingot from which the facet growth region is removed in the second process is etched, and the excitation light is applied to the etched surface in the third process. The case where the photoluminescence measurement can be accurately performed by irradiating is described below. It is assumed that the following specifications C and D are required for the GaAs wafer.
The required specification C is such that the carrier concentration range is 7.0 × 10 ¹⁷ ~ 1.2 × 10 ¹⁸ cm ^-3 The plane orientation was inclined from the (100) in the [011] direction by 10 ± 0.1 °, and the slice thickness of the wafer was 700 μm.
The required specification D is such that the range of the carrier concentration is 1.0 to 2.0 × 10 ¹⁸ cm ^-3 And the plane orientation was the same as the required specification C, but the slice wafer thickness was 550 μm.
[0059]
As a first step, a Si-doped GaAs single crystal ingot similar to that of the first embodiment was subjected to cylindrical grinding and surface grinding by the same method.
As a second step, the (0-11) plane, which is a ground surface, is inserted into an etching solution having a volume ratio of nitric acid and hydrochloric acid of 1: 1 with the (0-11) ± 60 ° of (0-11) ± 60 °. Only the portion in the range was etched at room temperature for 5 minutes in the same manner as in Example 1, and post-etching treatment was performed.
[0060]
As a third step, the movable stage 6 of the photoluminescence evaluation device is set so that the surface irradiated with the laser excitation light is (0-11) in the growth axis direction of the side surface of the ingot, that is, ± 2 ° with respect to the plane ground surface. The ingot 1 was set to. At this time, the angle between the (0-11) plane, which is the plane ground plane, and the laser beam irradiation may be set to 90 °, that is, perpendicular. The carrier concentration distribution in the growth axis direction of the ingot was obtained from the photoluminescence spectrum in the same manner as in Example 1, and as a result, 7.7 × 10 ¹⁷ cm ^-3 , 1.8 × 10 on the tail side ¹⁸ cm ^-3 Met.
[0061]
As a fourth step, since it is desired to collect as many wafers as the specification C as much as possible, the separation at the time of slicing is performed when the carrier concentration obtained by the photoluminescence method of the third step is 1.15 × 10 5 ¹⁸ cm ^-3 Was set. Note that the effective length of this single crystal ingot was 188 mm, the corresponding position was 98 mm from the tail side, and a mark was placed thereon.
Then, as shown in FIG. 6A, wax fixation was performed on the carbon slice base for fixing the ingot 1 so that the (0-11) plane, which is the plane ground surface, was the upper surface. In this case, the bonding surface is a mechanically ground surface that has not been subjected to chemical etching. Although a multi-wire saw was used for slicing, the roller pitch was set so as to correspond to each slice thickness, and the boundary position of the roller and the corresponding position of the ingot 1 were matched.
In order to cut out a plane inclined by 10 ° in the [011] direction from the (100) plane, the ingot fixed stage 83 is rotated by 10 ° from a right angle to the multi-wire 84 as shown in FIG. Was.
[0062]
As a result, 109 and 146 slice wafers of the specifications C and D were obtained by the slicing process, but there was no processing damage. In addition, the carrier concentration of the D-spec wafer in the vicinity of the corresponding position, which is the sorting processing boundary, was determined by the method using the Hall effect. ¹⁸ cm ^-3 There was no deviation from the two required specifications C and D.
[0063]
(Example 3)
Sorting processing of the same required specifications C and D as in Example 2 was performed on 18 single crystal ingots. The carrier concentration calculated by the photoluminescence method in the third step is 7.1 to 8.0 × 10 ¹⁷ cm ^-3 1.7 to 2.0 × 10 on the tail side ¹⁸ cm ^-3 Was in the range. Carrier concentration 1.15 × 10 ¹⁸ cm ^-3 Although the corresponding position of the sorting process was different for each ingot, the same slicing process as in Example 2 was performed by setting individually.
The total number of slice wafers of the specification C and the specification D was 1850 and 2765, respectively, and there was no processing damage during slicing, and there was no deviation from the standard of the carrier concentration.
[0064]
Next, a comparative example will be described.
(Comparative Example 1)
The same cylindrical and surface mechanical grinding was performed on the same five single crystal ingots as in Example 1.
No specific surface chemical etching was performed in the second step of the method for processing a single crystal ingot of the present invention. Next, the ingot is set on the movable stage of the photoluminescence evaluation apparatus so that the irradiation of the laser excitation light is (001) ± 5 ° in the direction of the growth axis on the side surface of the ingot. The angle between a certain (0-11) plane and the laser light irradiation plane was set to 45 °.
Then, the carrier concentration was measured by the photoluminescence method in the third step as in the example of the present invention.
As a result of determining the carrier concentration distribution in the growth axis direction of each of the five single crystal ingots, 7.3 to 8.5 × 10 ¹⁷ cm ^-3 1.7 to 2.5 × 10 on the tail side ¹⁸ cm ^-3 Was calculated. Note that the carrier concentration determined from the wavelength information of photoluminescence is determined from a calibration curve using a Hall effect measurement sample whose surface is mechanically ground.
And, as a fourth step, for each ingot, 1.1 × 10 ¹⁸ cm ^-3 Assuming the calculated position as the boundary between the required specification A and the specification B, sorting was performed.
As a result, as for the slice wafers, the total number of specifications A and specification B was 395 and 513, respectively. Further, there was no breakage during slicing because the wax fixing surface of the ingot was a mechanically ground surface.
[0065]
When the carrier concentration of the wafer at the sorting processing boundary position was determined by the Hall effect evaluation, a deviation from the specification range of the specification A occurred in two ingots, and the Hall effect evaluation was performed to obtain a wafer range falling within the specification range. Inspection work occurred five times.
In addition, 35 slice wafers out of the standard range of the A specification including loss due to re-inspection occurred. That is, a sorting loss of 8.9% with respect to the specification A occurred.
Also, the carrier concentration range of the original B specification, 1.0 to 2.0 × 10 ¹⁸ cm ^-3 Is satisfied, 2.0 × 10 ¹⁸ cm ^-3 Since there was one ingot that was evaluated as a portion exceeding the limit, the corresponding portion was cut off in a block shape without performing the wafer processing in the B specification. As a result, a sampling loss of 28 wafers occurred. That is, a sorting loss of 5.2% occurred with respect to the specification B.
Accordingly, it can be seen that, in Comparative Example 1 in which the second step in the present invention is not performed, the yield of the wafer is poor as compared with Examples 1 to 3 of the present invention.
[0066]
(Comparative Example 2)
The same processing and evaluation as in Example 1 were performed on three single crystal ingots, except for the etching method. In this case, since the entire ingot was immersed in the etching solution, all of the cylindrical mechanically ground surfaces were in a pseudo mirror surface state. After sorting the three ingots, 211 and 348 sliced wafers were obtained for specifications A and B, respectively.
As a result of inspecting the carrier concentration by the Hall effect measurement, there was no deviation of the carrier concentration from the standard range. However, the wafers fall off from the wax fixing part during the slicing process with two ingots, resulting in processing damage losses of 5 and 12 wafers in specifications A and B, respectively. Loss slightly increased to 3.3%, and the specification A was 2.3%. Thus, it can be seen that, in Comparative Example 2 in which etching different from the chemical etching in the second step in the present invention was performed, the yield of the wafer was lower than in Examples 1 to 3 of the present invention.
[0067]
As described above, it can be seen that there is a great difference in the wafer yield when comparing the example of the present invention with the comparative example. These differences are due to the following reasons.
In the present invention, as a second step before the carrier concentration measurement of the ingot by the photoluminescence in the third step, the damage due to the mechanical grinding in the first step is removed by chemical etching in advance at the excitation light irradiation position. As a result, there is no variation in the shape of the photoluminescence spectrum due to processing damage, and the carrier concentration of the ingot can be accurately measured.
Further, the chemical etching in the second step is partially performed on a specific surface of the ingot, and in the wafer slice in the fourth step, the wafer is fixed to the ingot fixing base via the surface that has not been chemically etched. In addition, it is possible to prevent the falling off of the wafer and the accompanying damage of the peripheral wafer.
[0068]
As described above, the embodiments of the present invention have been described. However, the present invention can be variously modified within the scope of the invention described in the claims, and it can be said that they are also included in the scope of the present invention. Not even.
[0069]
【The invention's effect】
As described above, according to the present invention, since the carrier concentration distribution of a semiconductor single crystal ingot is correctly evaluated before wafer processing, it is possible to significantly reduce the non-standard loss of the carrier concentration range caused by the conventional processing selection according to the conventional prediction. . At the same time, there is no processing loss at the time of wafer slicing, so that the loss in the sorting processing can be greatly reduced, and the feedback period for the crystal growth conditions can be greatly shortened.
[Brief description of the drawings]
FIG. 1A is a diagram schematically showing the state of habit lines of a GaAs single crystal ingot having a crystal growth orientation of [−100], and FIG. 1B is a facet growth of a crystal cross-section (100) wafer. It is a schematic diagram of an area.
FIG. 2A is a diagram illustrating a dipping mode when etching an ingot, and FIG. 2B is a diagram illustrating a mode of etching an ingot using an ingot holding table.
FIG. 3 is a view showing a movable stage of an ingot for evaluating the distribution of a photoluminescence spectrum.
FIG. 4 is a conceptual diagram of an inner peripheral blade slicer.
FIG. 5 is a conceptual diagram of a multi-wire saw.
6A and 6B show an orientation relationship of an ingot bonding and fixing surface and a positional relationship of an etched surface in a fourth step of the embodiment of the present invention, and FIG. 6A shows an AlInGaP-based semiconductor laser or LED substrate; (B) shows a case where a substrate of an AlGaAs-based surface emitting laser is manufactured.
FIG. 7 is a perspective view schematically showing a result of a carrier concentration distribution of the GaAs ingot of Example 1.
FIG. 8 is a diagram showing a wafer surface that has been subjected to mechanical damage to a chemically mirror-polished wafer.
FIG. 9 is a graph showing a distribution of a half width of a photoluminescence spectrum in a wafer diameter direction before and after giving a mechanical damage.
FIGS. 10A and 10B are graphs showing photoluminescence spectra before and after mechanical damage is caused. FIG. 10A shows a spectrum at point A of the wafer in FIG. 8, and FIG. 10B shows a spectrum at point D of the wafer in FIG.
[Explanation of symbols]
1 ingot
2 Etching solution
3 Ingot holding base
4 Height adjustment table
5 Etching solution tank
6 movable stage
61 X Stage
62 Y stage
63 Z stage
61a, 62a Stepping motor
7 Slicer
70 Ingot holding part
71 Ingot fixed base
72 X direction tilt
73 Y direction tilt
74 Inner peripheral blade
8 Multi-wire saw
80 Goniometer mechanism
81 Ingot fixing base
82 Ingot Clamp Clamp
83 Ingot fixed stage
84 Multi Wire

Claims (13)

A first step of mechanically grinding the single crystal ingot;
Identify the crystallographic plane of the side face of the single crystal ingot, which is either the part where facet growth does not occur or the part where the facet growth area is removed according to the crystal growth direction of the single crystal ingot, and only the surface A second step of performing etching;
A third step of irradiating the specified surface of the surface chemically etched in the second step with excitation light and evaluating a carrier concentration from a photoluminescence spectrum based on the excitation light;
A fourth step of performing slicing with the mechanically ground surface not subjected to chemical etching in the third step as a fixed surface;
A method for processing a single crystal ingot, which is performed in order. When the growth plane orientation of the single crystal ingot is [-100],
In the first step, the surface forming the surface ground surface by mechanical grinding is a surface within ± 5 ° from any one of the (0-11) surface and the (01-1) surface,
In the second step, the crystallographic planes are (001) plane, (0-10) plane, (00-1) plane, (010) plane, (0-11) plane, and (01-1) plane. A) a plane within ± 90 ° from any one of the planes, preferably a plane within ± 60 °, and performing the chemical etching only on the specified single crystal side surface region;
In the third step, a plane within ± 20 ° from any one of the (001) plane, the (0-10) plane, the (00-1) plane, and the (010) plane of the chemically etched portion. Irradiation of the excitation light is performed on the surface of the side surface of the ingot limited to any range within ± 5 ° from any one of the (0-11) plane and the (01-1) plane. The method for processing a single crystal ingot according to claim 1, wherein the method is performed. A growth direction of the single crystal ingot is a direction equivalent to [-100];
In the first step, a surface forming the surface ground surface is a surface within ± 5 ° from a plane equivalent to any one of the (0-11) plane and the (01-1) plane;
In the second step, the crystallographic planes are (001) plane, (0-10) plane, (00-1) plane, (010) plane, (0-11) plane, and (01-1) plane. A plane within ± 90 ° from a plane equivalent to any of the planes, preferably a plane within ± 60 °,
In the third step, the surface irradiated with the excitation light may be any one of the (001), (0-10), (00-1), and (010) planes of the chemically etched portion. An ingot limited to a range within ± 20 ° from the equivalent plane, or within ± 5 ° from a plane equivalent to any of the (0-11) plane and the (01-1) plane. 3. The method for processing a single crystal ingot according to claim 2, wherein the single crystal ingot is a side surface. When the growth plane orientation of the single crystal ingot is any of [1-1-1-1] and [111],
In the first step, the surface on which the plane ground surface is formed by mechanical grinding is defined as (1-10), (0-11), (-101), (-110), or (01-1). Plane and (10-1) plane and within ± 5 ° from any plane,
In the second step, chemical etching is limited to a single crystal side surface region within ± 90 °, preferably ± 60 ° with respect to the surface ground surface,
In the third step, the (1-10), (0-11), (-101), (-110), (01-1), and (10-1) faces of the chemically etched faces are obtained. The method for processing a single crystal ingot according to claim 1, wherein the surface of the side surface of the ingot limited to within ± 15 ° from any one of the surfaces is irradiated with the excitation light. A growth direction of the single crystal ingot is a direction equivalent to one of [1-1-1-1] and [111],
In the first step, the surface forming the surface ground surface includes a (1-10) surface, a (0-11) surface, a (-101) surface, a (-110) surface, a (01-1) surface, and (10-1) In addition to specifying a surface within ± 5 ° from a surface equivalent to any of the surfaces,
In the third step, the surface to be irradiated with the excitation light is a chemically etched surface (1-10) surface, (0-11) surface, (-101) surface, (-110) surface, 5. The single crystal ingot according to claim 4, wherein the surface is a side surface of the ingot limited within ± 15 ° from a plane equivalent to one of the (01-1) plane and the (10-1) plane. Method. The method for processing a single crystal ingot according to any one of claims 1 to 5, wherein a crystal structure of the single crystal ingot is one of a diamond type and a zinc blende type. Hydrochloric acid, nitric acid, a mixture of hydrochloric acid, nitric acid and water, a mixture of sulfuric acid, hydrogen peroxide and water, and a mixture of hydrochloric acid and hydrochloric acid when performing chemical etching on the specified region of the single crystal side surface. A mixture of hydrogen peroxide and water, a mixture of hydrofluoric acid, hydrogen peroxide and water, a mixture of acetic acid or water, hydrofluoric acid and nitric acid, a mixture of ammonia water, hydrogen peroxide and water, 7. A mixture of caustic soda, hydrogen peroxide and water, potassium hydroxide, hydrogen peroxide and water, or a mixture of bromine or iodine and methanol. The method for processing a single crystal ingot according to any one of the above. Whether the single crystal ingot is GaAs doped with any of Si, Te, Se, S, Zn and C, or InP doped with any of Se, Te, Sn, S, Zn and Cd The method for processing a single crystal ingot according to claim 1, wherein: The single crystal ingot is any one of GaP, GaSb, InSb, and InAs doped with any of Si, S, Se, Te, Zn, and Mg. The method for processing a single crystal ingot according to any one of the above. The single crystal ingot is any one of ZnSe, ZnTe, and CdTe doped with any of Li, Al, Ga, B, N, P, As, Sb, and Cl. The method for processing a single crystal ingot according to any one of claims 1 to 7. The single crystal ingot is any one of Si, Ge doped with any of B, Al, Ga, P, As, and Sb, and is characterized in that the single crystal ingot is one of Si and Ge. Processing method of single crystal ingot. In the chemical etching in the second step, the side surface of the ingot is held via a holder on a height adjusting table provided on the bottom surface of the etching liquid tank, and the height of the etching liquid surface or the height of the height adjusting table is adjusted. The method for processing a single crystal ingot according to any one of claims 1 to 11, wherein the method is performed by adjusting the thickness. The single crystal according to any one of claims 1 to 12, wherein, when performing the chemical etching in the second step, a region not to be etched is masked with an adhesive tape or a coating type masking agent. Ingot processing method.

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