Semiconductor carrier density evaluation device

Abstract

To evaluate and confirm carrier density by relating the carrier density to the actual enlargement / reduction state of a crystal defect.SOLUTION: An enlargement / reduction state of a defect of a sample 1 irradiated with light by light irradiation means 3 is detected by a two-dimensional detector 5, and a value of a carrier density when the defect of the sample 1 changes (upon enlargement / reduction of the defect) is determined by a control device 6 based on the enlargement / reduction state of the sample 1 and on information of a Hall voltage formed by hall signal generation means 7.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a semiconductor carrier density evaluation device capable of evaluating and confirming the carrier density by making the carrier density correspond to the actual expansion and contraction of crystal defects.

Background Art

[0002] It is known that stacking defects in silicon carbide (SiC) crystals expand and contract according to the injected excess carrier density and temperature. Here, typical stacking defects are single-shockley type stacking defects and double-shockley type stacking defects. In particular, it is known that single-shockley type stacking defects expand with the basal plane dislocation as the nucleus and the excess carrier density around it becoming high, which is a major issue in ensuring the long-term reliability of power devices using SiC as a semiconductor material.

[0003] There are many basal plane dislocations in an SiC single crystal substrate, and when an SiC single crystal film is formed on it, a part of the basal plane dislocations in the substrate propagates. In a PiN diode fabricated using such a single crystal film and a single crystal substrate, it has been a major issue that stacking defects expand due to energization. In this case, holes are injected from the anode and electrons are injected from the cathode.

[0004] As a solution for suppressing the expansion of stacking defects, reducing the basal plane dislocation density in the SiC single crystal film has been studied, and by devising the film formation conditions, the conversion efficiency to other dislocations (through edge dislocations) during the film formation of the single crystal film can be increased. Currently, it has been reported that the basal plane dislocation can be made zero even on a wafer with a diameter of 150 mm.

[0005] On the other hand, when increasing the current density, it has been an issue that stacking defects expand from the basal plane dislocations on the substrate side rather than the interface between the single-crystalline film and the single-crystalline substrate. When using the sublimation method used for the production of SiC single crystals, it is difficult to make the basal plane dislocation density zero. As a solution, in order to reduce the excess carrier density, particularly the minority carrier density, around the basal plane dislocations, it has been studied and the effect has been demonstrated that inserting a layer with a short carrier lifetime as a buffer layer.

[0006] Here, the carrier lifetime is the time when excess carriers disappear in the semiconductor. As a measure to shorten the carrier lifetime, increasing the free carrier density in the SiC single-crystalline film and introducing lattice defects that act as recombination centers have been proposed. When inserting a layer with a certain value of carrier lifetime, it has been experimentally shown that the higher the thickness, the higher the current density that causes the expansion of stacking defects.

[0007] Here, the carrier density in the desired layer is generally analytically obtained by simulation from the device structure and the current density (see, for example, Patent Document 1). By grasping the carrier density by simulation, it is possible to infer the carrier density at which the behavior of the expansion and contraction of stacking defects occurs.

[0008] However, since the accuracy of the carrier density estimated by simulation depends on the structural model, it lacks quantitative properties, and the emergence of a technology that can quantitatively associate the relationship between the behavior of the expansion and contraction of stacking defects and the carrier density is desired.

[0009] It has been reported that the threshold of the excess carrier density at which stacking defects expand varies depending on the impurity density of the SiC single crystal, etc. In elucidating the physical mechanism regarding the expansion of stacking defects, a method for determining the excess carrier density is also required. Since the expansion threshold of stacking defects varies depending on the impurity density and measurement temperature of the SiC single crystal film, in order to improve the reliability of devices using SiC single crystals, an evaluation method capable of obtaining quantitative values is required for quality control.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] The present invention has been made in view of the above situation, and an object thereof is to provide a semiconductor carrier density evaluation device capable of quantitatively determining the carrier density corresponding to the actual expansion and contraction of crystal defects.

Means for Solving the Problems

[0012] The semiconductor carrier density evaluation device according to claim 1 for achieving the above object includes: light irradiation means for irradiating a semiconductor sample with light; the Actual of the sample irradiated with light by the light irradiation means State of stacking defect two-dimensional detection means for detecting; current application means for applying a current to the sample; magnetic field generation means for applying a magnetic field to the sample; the Stacking defect of the sample detected by the two-dimensional detection means, and information on the electrical signals formed by the current application means and the magnetic field generation means are input, and based on these information, the State of stacking defect control means for deriving the value of the carrier density when changes occur is provided、 The current application means and the magnetic field generation means are An electric field in the electrode direction and a Hall signal generation means for generating an electric field in a direction perpendicular to the magnetic field The control means is Based on the expansion and contraction information of the stacking defect of the sample when irradiated with the light irradiation means, obtain the Hall voltage of the sample, and derive the carrier density based on the information of this Hall voltage It is characterized by the following.

[0013] In the present invention according to claim 1, the State of stacking defect (two-dimensional situation) of the sample in the state irradiated with light by the light irradiation means is detected by the two-dimensional detection means, and based on the information of the Stacking defect of the sample detected by the two-dimensional detection means, the current applied by the current application means, and the information of the magnetic field formed by the magnetic field generation means, the value of the carrier density when the State of stacking defect of the sample changes (when the defect expands or contracts) can be derived. Here, the derived carrier density is the sum of the carrier density in the dark and the excess carrier density generated by light irradiation. Also, the excess carrier density generated by light irradiation can be calculated from the difference between the two. Then, a Hall electric field is generated by the Hall signal generation means, the Hall voltage is obtained based on the information of the stacking defect of the sample, and the value of the carrier density can be obtained based on the information of the Hall voltage That is, based on the information of crystal defects (expansion and contraction situation) and the information of Hall electric field, the value of the carrier density when the crystal defects of the sample expand and contract can be derived In addition, the value of the threshold excess carrier density, which is the carrier density when the crystal defects expand and contract, can be determined

[0014] Thereby, it becomes possible to make the carrier density of the sample correspond to the detected State of stacking defect{(actual expansion and contraction situation of the situation of crystal defects: two-dimensional situation)} .

[0017] Also, Claim 2 the semiconductor carrier density evaluation device of the present invention according to Claim 1 is characterized in that, in the semiconductor carrier density evaluation device described in

[0018] Claim 2 In the present invention according to

[0019] Also, Claim 3 the semiconductor carrier density evaluation device of the present invention according toClaim 1 or Claim 2 In the semiconductor carrier density evaluation apparatus according to , it is characterized by comprising stress applying means for applying bending stress to the sample.

[0020] Claim 3 In the present invention according to , by applying a desired bending stress to the sample by the stress applying means, the value of the carrier density under arbitrary stress conditions can be obtained.

[0025] Also, Claim 4 The carrier density evaluation apparatus of the present invention according to is Claims 1 to 3 In the semiconductor carrier density evaluation apparatus according to any one of , the sample is a sample for evaluating the carrier density, and the control means is based on the Any state of stacking defect When the is obtained, based on the value of the carrier density, Desired state of stacking defect It is characterized by having a function of setting the device structure so that the carrier density to be obtained is the carrier density to be obtained.

[0026] Claim 4 In the present invention according to , the State of stacking defect When the changes (when the defect expands or contracts), the value of the carrier density is derived, and based on the value of the carrier density of the sample, Desired state of stacking defect The device structure can be set so that the carrier density to be obtained is the carrier density to be obtained (the device structure can be set according to the sample).

[0027] Also, Claim 5 The semiconductor carrier density evaluation apparatus of the present invention according to is Claims 1 to 3 In the semiconductor carrier density evaluation apparatus according to any one of , the sample is an actual sample cut out from a single crystal film, and the control means is based on the Desired state of stacking defect When the is obtained, based on the value of the carrier density, it has a function of evaluating the carrier density of the actual sample and confirming the carrier density (a function of confirming whether it is a desired carrier density).

[0028] Claim 5In the present invention related thereto, the value of the carrier density when State of stacking defect changes (when the defect expands or contracts) is derived, and Desired state of stacking defect based on the value of the carrier density when obtained, the carrier density of the actual sample can be evaluated and the carrier density can be confirmed (it can be confirmed whether the actual sample is in the designed state). For example, the data is mapped, and the carrier density is confirmed for the actual measurement result (Hall electric field) based on the map. Also, Desired state of stacking defect in addition to the carrier density when obtained, the state of the actual sample is confirmed (cross-checked) based on the conductivity and carrier mobility.

[0029] Also, Claim 6 The semiconductor carrier density evaluation device according to the present invention related thereto is Claims 1 to 5 In the semiconductor carrier density evaluation device according to any one of the above, the sample is characterized in that it is formed from a silicon carbide semiconductor.

[0030] Claim 6 In the present invention related thereto, State of stacking defect of silicon carbide semiconductor the value of the carrier density when changes (when the defect expands or contracts) can be derived.

[0031] Also However, Claim 7 The semiconductor carrier density evaluation device according to the present invention related thereto is Any one of Claims 1 to 6 In the semiconductor carrier density evaluation device according to the above, the stacked defect is characterized in that it is a single shockley type stacked defect and a double shockley type stacked defect.

Effect of the Invention

[0032] The semiconductor carrier density evaluation device of the present invention can make the carrier density correspond to the actual expansion and contraction situation of the State of stacking defect (crystal defect: two-dimensional situation) of the sample.

Brief Description of the Drawings

[0033]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0034] FIG. 1 shows the schematic configuration of the equipment of an evaluation apparatus which is a semiconductor carrier density evaluation apparatus according to an embodiment of the present invention, FIG. 2 shows the block configuration of control means, FIG. 3 shows the conceptual situation of the Hall voltage, and FIGS. 4 and 5 show control graphs for quantifying the carrier density.

[0035] As shown in FIG. 1, a sample 1 of a semiconductor to be evaluated (a sample for evaluating the carrier density) is placed on a carrier density evaluation apparatus 10, and a table 2 having a temperature adjustment function, a stress application function, and a magnetic field application function (magnetic field application means) is provided. An optical irradiation means 3 for irradiating laser light or the like is provided, and light of an arbitrary wavelength and an arbitrary intensity is emitted from the optical irradiation means 3 to the sample 1.

[0036] For example, the optical irradiation means 3 is a laser light, a light emitting diode (LED) light, a lamp, etc. As its wavelength, in the case of one-photon excitation, it is equal to or higher than the bandgap energy of the semiconductor to be evaluated or equal to or higher than the energy of the crystal defect level, and in the case of two-photon excitation, it is equal to or higher than 1 / 2 of the bandgap energy of the semiconductor to be evaluated or equal to or higher than 1 / 2 of the energy from the defect level formed by the crystal defect to the conduction band or the valence band. Those having such energies can be used. Multi-photon excitation such as three-photon excitation may also be used.

[0037] The magnetic field applying means (magnetic field generating means) provided in Table 2 is, for example, a permanent magnet or the like, and can apply a magnetic field to the sample 1 to be evaluated. Also, the direction, polarity, and intensity of the magnetic field may be arbitrarily controlled. The temperature adjustment function (temperature adjustment means) can use, for example, the arrangement of a heater directly below the sample to be evaluated or a constant temperature bath. The stress applying function (stress applying means) can use, for example, a four-point bending structure.

[0038] A grasping device (microscope) 4 for grasping the situation of the sample 1 irradiated with light is provided, and the information grasped by the grasping device 4 is adjusted to two-dimensional information ( Information on the state of stacking defect: two-dimensional information) by the two-dimensional detector 5 and sent to the control device 6 (control means). Incidentally, when there is no Stacking defect on the sample 1, an indentation can be intentionally formed by pressing a piezoresistor into the sample 1.

[0039] A current applying means for applying a current to the sample 1 is provided, and the current applying means can use a DC power supply, an AC power supply, or a superposition of them. The current applying means and the magnetic field applying means constitute a Hall signal generating means 7 for generating an electric field in the electrode direction and an electric field (Hall electric field) in a direction perpendicular to the magnetic field.

[0040] The information on the Hall voltage generated by the Hall signal generating means 7 constituted by the current applying means and the magnetic field applying means is sent to the control device 6. The control device 6 has a carrier density deriving function for deriving the value of the carrier density when the Information on the state of stacking defect: of the sample 1 expands or contracts based on the two-dimensional information ( Stacking defect two-dimensional information: two-dimensional situation grasping function) grasped by the grasping device 4 and the information on the Hall voltage (Hall signal grasping function) generated by the Hall signal generating means 7.

[0041] As shown in FIG. 2, the control device 6 is based on the two-dimensional information grasped by the grasping device 4 and adjusted by the two-dimensional detector 5 ( Information on the state of stacking defect:It has a two-dimensional situation grasping function 11 to which two-dimensional information) is sent. Further, the control device 6 has a hall signal grasping function 12 to which information on the hall voltage generated by the hall signal generating means 7 is sent. Then, the information grasped by the two-dimensional situation grasping function 11 and the information on the hall voltage grasped by the hall signal grasping function 12 are sent to the carrier density deriving function 13, and the carrier density is obtained. Stacking defect The information of, and the information on the hall voltage grasped by the hall signal grasping function 12 are sent to the carrier density deriving function 13, and the carrier density is obtained.

[0042] As shown in FIG. 3, for the semiconductor sample 21, by supplying a current from the power supply means 22 through the electrodes, an electric field is formed in the direction of the current (y direction), and a magnetic field is formed in the z direction perpendicular to the y direction by the magnetic field applying means. Then, a hall electric field is formed in the direction perpendicular to the y direction and the z direction (the plane direction of the sample: x direction). Based on the information of the hall electric field (hall voltage), the type (electron, hole) of carriers, the carrier density, and the carrier mobility of the sample 21 can be grasped (measured).

[0043] For the detection of the hall voltage, for example, a voltmeter can be used. When an AC signal is used in the light irradiation means, the magnetic field applying means, or the current applying means, a lock-in amplifier or the like can also be used to improve the signal-to-noise ratio.

[0044] As shown in FIG. 4, in the two-dimensional situation grasping function 11, a graph of the relationship between the hall voltage and the light intensity (reference map) is stored. That is, a map of the state in which the hall voltage (V) decreases as the light intensity from the light irradiation means 3 increases is stored. And in the two-dimensional map is stored together with information on the state in which the size of the defect 15 crystal defect) increases as the light intensity from the light irradiation means 3 increases. Stacking defect( defect 15 : crystal defect) increases as the light intensity from the light irradiation means 3 increases.

[0045] That is, the reference map stores information that as the light intensity increases, the Hall voltage (V) decreases, and information that as shown by the triangular marks in the figure, the size of defect 15 increases (or decreases). Therefore, based on the reference map, the light intensity I th for the Hall voltage (V) value V Hth can be grasped.

[0046] In addition, with the temperature adjustment function and the stress application function, by applying a desired temperature and a desired stress to sample 1, the relationship between the Hall voltage and the light intensity shown in Fig. 4 is corrected to a state based on the applied temperature and stress.

[0047] The Hall signal grasping function 12 receives the information formed by the Hall signal generating means 7 (the Hall voltage information shown in Fig. 3). And the Hall signal grasping function 12 has grasped the result of the relationship between the carrier density and the Hall voltage by calculation (see Fig. 5). That is, as the Hall voltage (V) increases, a calculation result is obtained that the carrier density (n) decreases.

[0048] That is, as the Hall voltage (V) increases, a calculation result is obtained in a state where the carrier density (n) decreases and the decrease in the carrier density (n) becomes gentle, and the value n of the carrier density (n) at an arbitrary Hall voltage (V) value (the situation of an arbitrary defect 15) th can be obtained.

[0049] In the carrier density derivation function 13, based on the value V of the Hall voltage (V) in the defect 15 in an arbitrary state Hth the value n of the carrier density (n) in the defect 15 in an arbitrary state (for example, when the defect 15 increases) th is obtained. The obtained value n of the carrier density (n) th is evaluated and output as, for example, a threshold value when the defect 15 expands.

[0050] The basal plane dislocation of the SiC crystal becomes the nucleus, the excess carrier density around it increases, and the stacking defect (defect 15) expands. In the carrier density derivation function 13 described above, the threshold excess carrier density (the threshold value of the carrier density) when the defect 15 expands or contracts can be quantitatively evaluated.

[0051] The operation of the carrier density evaluation device 10 described above will be described.

[0052] By the temperature adjustment function and the stress application function, light with an arbitrary wavelength and intensity is irradiated from the light irradiation means 3 to the sample 1 adjusted to a desired temperature and a desired internal stress state, and the defect 15 is uniformly irradiated with light. By irradiating the defect 15 with light while changing the intensity, the carrier density around the defect 15 of the sample 1 in the desired environmental state is changed. The Hall voltage when the defect 15 expands or moves is formed by the Hall signal generation means 7 and measured by the Hall signal grasping function of the control device 6.

[0053] Light intensity I th The value V of the Hall voltage (V) with respect to Hth Based on this, the value n of the carrier density (n) at the defect 15 in the expanded or moved state (for example, when the defect 15 becomes larger) th is obtained. The obtained value n of the carrier density (n) th is evaluated and output as, for example, the threshold value when the defect 15 expands.

[0054] The carrier density when the size of the defect 15 changes is obtained, and that value is used as the threshold value. By fabricating a semiconductor with a desired carrier density while grasping the threshold value, a semiconductor in which the defect 15 does not expand can be obtained, and the reliability is improved. For example, by laminating layers with different carrier densities, the state of the defect (the state of the carrier density) can be controlled.

[0055] That is, based on the value n of the carrier density (n) when Any state of stacking defect the sample 1 (sample sample) for evaluating the carrier density is obtained th Desired state of stacking defect ​It has a function of setting the device structure so as to obtain the carrier density at which the situation of th defect 15 occurs. Then, based on the value n of the carrier density (n) of sample 1 th the device structure can be set according to sample 1 so as to obtain the carrier density (n) at which the desired defect 15 occurs (the defect 15 is in the desired state).

[0056] For example, a device structure including a single crystal film having desired physical properties can be constructed. That is, in single crystal films with different impurity densities and carrier lifetimes, by designing so as to obtain the value n of an arbitrary carrier density (n) th (by designing to a carrier density regulated by the threshold value at which the spread of defects occurs), a stacked device with suppressed defect spread can be manufactured.

[0057] In the above-described embodiment, as sample 1, a sample sample for evaluating the carrier density is used, the carrier density (n) of the sample sample is evaluated, and an example of setting the device structure according to the sample sample is described. However, as the sample, it is also possible to evaluate the carrier density (n) of an actual product sample using an actual product sample cut out from the actual product.

[0058] By using the actual product sample, it is possible to confirm whether the single crystal film in the device structure designed based on sample 1 is manufactured as designed (a function of confirming whether it is the desired carrier density).

[0059] Also, in the above-described embodiment, based on the reference map, the light intensity at which the value V of the Hall voltage (V) Hth is obtained is used as the state of irradiating light, and while changing the stress applied to sample 1 by the stress application function, the state of the actual sample can be confirmed by confirming the state of defect 15.

Industrial Applicability

[0060] The present invention can be used in the industrial field of a semiconductor carrier density evaluation apparatus capable of evaluating and confirming the carrier density.

Explanation of Signs

[0061] 1 Sample (sample) 2 Table 3 Light irradiation means 4 Grasping device 5 Two-dimensional detector 6 Control device 7 Hall signal generation means 10 Carrier density evaluation apparatus 11 Two-dimensional situation grasping function 12 Hall signal grasping function 13 Carrier density derivation function 15 Defect 21 Sample 22 Power supply means

Claims

1. A light irradiation means for irradiating a semiconductor sample with light; a two-dimensional detection means for detecting a state of stacking faults in the sample when light is irradiated by a light irradiation means; A current applying means for applying a current to the sample; A magnetic field generating means for applying a magnetic field to the sample; a control means for receiving information on stacking faults in the sample detected by the two-dimensional detection means, and information on the electric signals generated by the current application means and the magnetic field generation means, and for deriving a carrier density value when a state of the stacking faults in the sample changes based on the information; The current applying means and the magnetic field generating means include: a Hall signal generating means for generating an electric field in a direction perpendicular to the electrodes and the magnetic field; The control means A Hall voltage of the sample is obtained based on information on the expansion and contraction of stacking faults in the sample when irradiated by the light irradiation means, and a carrier density is derived based on the information on the Hall voltage.

2. A semiconductor carrier density evaluation device comprising:

2. The semiconductor carrier density evaluation device according to claim 1, A temperature control means for changing the temperature of the sample is provided.

2. A semiconductor carrier density evaluation device comprising:

3. The semiconductor carrier density evaluation device according to claim 1 or 2, A stress applying means for applying a bending stress to the sample is provided.

2. A semiconductor carrier density evaluation device comprising:

4. The semiconductor carrier density evaluation device according to any one of claims 1 to 3, the sample is a sample for evaluating carrier density, The control means includes: The device structure is set to a carrier density that provides a desired stacking fault state based on the carrier density value when an arbitrary stacking fault state of the sample specimen is obtained.

2. A semiconductor carrier density evaluation device comprising:

5. The semiconductor carrier density evaluation device according to any one of claims 1 to 3, The sample is a real product sample cut out from a real product, The control means includes: The method has a function of evaluating and confirming the carrier density of the actual sample based on the carrier density value when the desired state of stacking faults in the actual sample is obtained.

2. A semiconductor carrier density evaluation device comprising:

6. The semiconductor carrier density evaluation device according to any one of claims 1 to 5, The sample is made of a silicon carbide semiconductor.

2. A semiconductor carrier density evaluation device comprising:

7. The semiconductor carrier density evaluation device according to any one of claims 1 to 6, The stacking faults are single Shockley type stacking faults and double Shockley type stacking faults.

2. A semiconductor carrier density evaluation device comprising:

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