JP4247007B2 - Semiconductor wafer evaluation method and semiconductor device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor wafer evaluation method, and more particularly, to a semiconductor wafer evaluation method for evaluating defects on a surface layer of a semiconductor wafer by measuring photoluminescence light by irradiation with excitation light.
[0002]
[Prior art]
In a process of forming an integrated circuit on a semiconductor wafer such as a silicon wafer, crystal defects existing in the operation region of the semiconductor integrated circuit, that is, in the vicinity of the surface of the wafer, cause a hindrance to the normal operation of the semiconductor integrated circuit.
[0003]
With the miniaturization of semiconductor integrated circuits, every time a design rule is changed, a minute defect that has been considered to have no influence in the past has become apparent as a defect that hinders the normal operation of the circuit. For example, when the 0.35 μm design rule is recently adopted, a void defect having a size of about 0.1 μm, which was not a problem with the previous design rule, became apparent. A void defect is an aggregate of atomic vacancies formed during silicon crystal growth, as shown in FIG. 1A, and has a regular octahedral structure with one side of about 0.1 μm.
[0004]
If the example of a void defect is followed, the rule of thumb that the defect of the size of about 1/3 of a design rule affects the operation | movement of a semiconductor integrated circuit can be derived. For example, in the 0.10 μm rule, defects having a size of 0.03 μm or more must be excluded from the operating area of the integrated circuit. In order to eliminate defects, it is first necessary to recognize the presence of 0.03 μm size defects on the extreme surface layer.
[0005]
As a method for detecting defects on the surface layer of the silicon wafer, a selective etching method and a light scattering method are widely used. The selective etching method can detect only defects having a size of submicron or more, but the light scattering method can recognize a scatterer (defect) having a size of 0.03 μm or more. In the light scattering method, a region in which no defect of 0.03 μm size or more exists is called a defect-free region or DZ (Denuded Zone). Usually, a wafer whose DZ width determined by the light scattering method is a specified value or more is used. If it passes, it is adopted as a wafer for manufacturing a semiconductor integrated circuit.
[0006]
On the other hand, in order to eliminate void defects on the surface layer after the 0.35 μm design rule, an annealed wafer has been devised in which the wafer is subjected to a heat treatment to eliminate the void defects on the surface prior to the formation of the integrated circuit. As heat treatment conditions, heating is performed at a temperature of 1000 ° C. or more for 1 hour or more in a non-oxidizing atmosphere such as argon or hydrogen. During such heat treatment, void defects are eliminated, but defects such as oxygen precipitates are eliminated. Newly occurs. Precipitates at a deep position of the wafer are necessary as gettering sites, but oxygen precipitates generated in the vicinity of the wafer surface and remaining void defects are not preferable for the operation of the semiconductor device. At present, the above-described light scattering method is exclusively used to detect precipitates and void defects in the vicinity of the wafer surface layer.
[0007]
Against this background, it is predicted that a 0.02 μm-sized defect will appear in the next generation 0.07 μm rule as shown in FIG. Is concerned. As described above, the minimum size of a scatterer (defect) that can be recognized using a light scattering method that is used for general purposes and is said to have the highest detection sensitivity is 0.03 μm. According to the fact that a 1/3 size defect of the design rule becomes apparent, in the 0.07 μm design rule, the 0.02 to 0.03 μm size defect may cause the integrated circuit to operate normally. Such a very small defect cannot be detected by the light scattering method having a detection limit in the vicinity of 03 μm.
[0008]
Similarly, in order to eliminate surface defects, an epitaxial wafer having an epitaxial growth layer with a low impurity concentration in the surface layer region from the surface to 10 μm has been conventionally used. As a method for evaluating the surface layer of an epitaxial wafer, an excitation light having an energy larger than the band gap of the semiconductor material of the wafer is irradiated, an electron-hole pair is generated near the surface of the semiconductor layer, and a specific wavelength emitted by recombination is generated. A method is known in which the strength is detected to evaluate the lifetime of a silicon crystal (see, for example, Patent Document 1).
[0009]
There has also been proposed a method for measuring the lifetime of the semiconductor layer of the epitaxial growth layer by generating excited minority carriers in a state where a predetermined electric field is applied to the semiconductor wafer (see, for example, Patent Document 2). .
[0010]
It is essential that the lifetime of a silicon wafer as a starting material is long. However, if the wafer has trap levels due to lattice defects or heavy metal impurities, the carriers of electrons and holes are recombined through the traps and the carrier density is attenuated. When there are many defects, the time when the carrier density becomes 1 / e of the original, that is, the lifetime is shortened. Therefore, in the lifetime measurement method using excitation light, a silicon wafer whose lifetime is equal to or greater than a predetermined value is regarded as a passing wafer, and the process proceeds to a semiconductor element manufacturing process.
[0011]
[Patent Document 1]
JP-A-8-139146
[0012]
[Patent Document 2]
JP-A-10-270516
[0013]
[Problems to be solved by the invention]
However, in the epitaxial wafer lifetime evaluation method using the above-described excitation light, regardless of the position, size, and type of defects present in the epitaxial growth layer, all defects and the presence of heavy metal impurities are considered as causes of recombination. Since only the recombination lifetime is evaluated, it is impossible to determine whether there is a defect that actually affects the operation of the element formed on the wafer surface.
[0014]
Therefore, the present invention utilizes a semiconductor wafer evaluation method suitable for detecting a very small defect of 0.02 μm or less existing on the surface layer of a semiconductor wafer, particularly an annealed wafer, and such a semiconductor wafer evaluation method. An object is to provide a method for manufacturing a semiconductor device.
[0015]
[Means for Solving the Invention]
In order to achieve the above-described object, the present invention basically uses a photoluminescence measurement method by irradiation with excitation light, and from the intensity distribution of light emission at a specific wavelength (band edge light emission), the position of the defect, the defect distribution density, Determine the defect size.
[0016]
Further, in the semiconductor device manufacturing process, the semiconductor integrated circuit manufacturing process is started by determining the pass / fail of the wafer based on the defect position and defect density obtained from the photoluminescence measurement result.
[0017]
In particular, by irradiating a silicon wafer with laser light with a wavelength of 800 nm or less, more preferably with laser light with a wavelength of 500 nm or less, and measuring photoluminescence light obtained from silicon, in a surface layer region within 10 μm from the surface Therefore, it is possible to specify a very small defect having a size of 0.02 μm or less that cannot be detected by the light scattering method.
[0018]
Specifically, in the first aspect of the present invention, the semiconductor wafer evaluation method includes the following steps.
(A) irradiating a semiconductor wafer with excitation light having a wavelength of 800 nm or less and measuring a spectrum of photoluminescence light generated from the semiconductor wafer;
(B) extracting the intensity of the band edge emission from the spectrum of the photoluminescence light to obtain the intensity distribution of the band edge emission in the semiconductor wafer; and
(C) A step of evaluating defects in the surface layer of the semiconductor wafer from the intensity distribution of hand edge emission.
[0019]
According to this evaluation method, it becomes possible to more specifically determine the defect on the wafer surface layer from the intensity distribution of the band edge emission, and the wafer can be accurately evaluated.
[0020]
Preferably, the method further includes a step of three-dimensionally plotting the relationship between the coordinates on the semiconductor wafer and the light emission intensity from the intensity distribution of the band edge light emission. Thereby, the defect of a semiconductor wafer can be recognized visually immediately.
[0021]
The semiconductor wafer evaluation method further includes a step of removing a component in accordance with the normal distribution from the intensity distribution of hand-end light emission, and a step of extracting a reduced emission intensity portion from the intensity distribution after the removal of the normal distribution component. By quantifying or enlarging and displaying the portion where the light emission intensity is taken out, the wafer defect can be analyzed in more detail, and the evaluation accuracy is improved.
[0022]
Defect evaluation is performed based on at least one of defect position, distribution density, and defect size. In particular, by quantifying the degree of decrease in light emission intensity, it becomes possible to specify the type and size of a defect that causes a decrease in intensity, thereby enabling more accurate wafer evaluation.
[0023]
The semiconductor wafer is an annealed wafer that has been annealed. Alternatively, an epitaxial wafer obtained by epitaxially growing silicon on the wafer surface, a surface polished wafer, a CZ wafer, or the like may be used.
[0024]
As a second aspect of the present invention, a method for manufacturing a semiconductor device using the evaluation method described above is provided. The method for manufacturing a semiconductor device includes the following steps.
(A) a step of cutting a plurality of semiconductor wafers from a semiconductor ingot into a lot;
(B) A step of taking an arbitrary semiconductor wafer from the lot and making it an evaluation wafer,
(C) irradiating the evaluation wafer with excitation light having a wavelength of 800 nm or less and measuring a spectrum of photoluminescence light generated from the evaluation wafer;
(D) extracting the intensity of the band edge emission from the spectrum of the photoluminescence light, and obtaining the intensity distribution of the band edge emission in the wafer for evaluation;
(E) a step of evaluating defects of the wafer for evaluation based on the intensity distribution of hand edge emission;
(F) determining whether the evaluation wafer is acceptable based on the evaluation result; and
(G) A step of forming a semiconductor element on the semiconductor wafer of the lot when the evaluation wafer is judged acceptable.
[0025]
According to such a method for manufacturing a semiconductor device, it is possible to make a flexible pass / fail judgment based on more accurate wafer evaluation, thereby improving the yield of the semiconductor device.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0027]
FIG. 2 is a graph for explaining the principle of the photoluminescence method employed in the present invention. When light having a photon energy larger than the band gap is used as an excitation source and the semiconductor crystal is irradiated with light and absorbed, non-equilibrium electrons and holes are generated. The generated electrons and holes go through several metastable states and recombine to return to the initial thermal equilibrium state. The light emitted by the luminescent recombination in this process is photoluminescence light.
[0028]
The graph of FIG. 2 shows a typical photoluminescence spectrum of a silicon wafer (crystal). The light emission indicated by the arrow is called band edge light emission, and is light emission in the recombination process of free electrons in the conduction band and free holes in the valence band. When defects exist in the crystal, electrons or holes generated by light irradiation are trapped in the defects, and the intensity of band edge emission decreases. In other words, a decrease in the band edge emission intensity indicates that a defect exists in the crystal.
[0029]
By the way, since the penetration depth of light into a solid depends on the wavelength of irradiation light, it is possible to obtain information from the surface in the depth direction by selecting the wavelength of excitation light in photoluminescence evaluation. . According to GE Jellison Jr. et al. (J. Appl. Phys. 53 (5) May 1982, at 3745), the penetration depth of light into a silicon crystal is about 10 μm at a wavelength of 800 nm. As the wavelength decreases (ie, as the energy increases), the absorption increases and the light penetration length decreases. Therefore, by defining the wavelength of the excitation light at 800 nm or less, it is possible to obtain information on the defect state having a depth within 10 μm from the surface. In particular, by setting the wavelength of the excitation light to 500 nm or less, it becomes possible to evaluate defects of about 3 μm from the surface, and by setting the wavelength in the vicinity of the upper limit of the ultraviolet region, the extreme surface layer shallower than 1 μm from the surface Evaluation becomes possible.
[0030]
FIG. 3 is a schematic configuration diagram of the photoluminescence measuring apparatus 10 used in the semiconductor wafer evaluation method of the present invention. A sample wafer to be measured is mounted on the sample holder 1. Laser light emitted from the laser 2 is irradiated onto the sample wafer through the irradiation optical system 3. The photoluminescence light emitted from the sample is collected by the condensing optical system 4, separated by the spectroscope 5, and then detected.
[0031]
Preferably, the laser beam is scanned relative to the sample wafer, the photoluminescence spectrum at each (x, y) position is measured, and the band edge emission intensity is extracted. The band edge emission intensity on the wafer is stored in a storage medium (not shown) and used for defect evaluation of the sample wafer. Details of the defect evaluation will be described later.
[0032]
In the embodiment of the present invention, measurement is performed on both the epitaxial wafer and the annealed wafer using the photoluminescence measuring apparatus 10 of FIG.
[0033]
The sample used for the epitaxial wafer experiment is a wafer obtained by epitaxially growing a silicon thin film having a thickness of 5 μm on a wafer (hereinafter referred to as “CZ wafer”) obtained from an ingot produced by the CZ method. The epitaxial wafer has a lower defect density in the epitaxial layer (device active region) than the CZ wafer or annealed wafer. Therefore, among the many silicon wafers, it is said to have the highest crystallinity (surface integrity).
[0034]
On the other hand, the anide wafer is a wafer obtained by annealing a CZ wafer at a high temperature in an inert atmosphere. The purpose of annealing is to eliminate void defects on the surface generated during crystal growth. As long as the light scattering method is used for the annealed wafer, it has been confirmed that there are no scatterers (defects) in the region of about 15 μm from the surface layer. However, as described above, the detection lower limit of the light scattering method is 0.03 μm, and it is unknown about the presence of extremely small defects of 0.03 μm or less. The possibility of the existence of void defects that cannot be completely eliminated by annealing and the existence of new oxygen precipitates cannot be denied, and it is an important issue to measure the existence of these in the next generation rules.
[0035]
FIG. 4 is a measurement result of photoluminescence when each of the epitaxial wafer and the annealed wafer is irradiated with laser light having a wavelength of 514.5 nm, and FIG. 5 is a 364 nm laser for each of the epitaxial wafer and the annealed wafer. It is a measurement result of photoluminescence when light is irradiated. The alternate long and short dash line indicates the spectrum of the epitaxial wafer (also referred to as “epi wafer”), and the solid line indicates the spectrum of the annealed wafer. The penetration depth of light is about 10 μm from the surface at a wavelength of 514.5 nm (FIG. 4), and about 10 nm from the surface at a wavelength of 364 nm (FIG. 5).
[0036]
4 and 5, the large emission (peak) seen near the wavelength of 1150 nm of the photoluminescence spectrum is the band edge emission, and the free electrons in the conduction band and the free holes in the valence band generated by the irradiation of the excitation light. It is luminescence generated in the recombination process. In both cases of FIG. 4 and FIG. 5, the decrease in the band edge emission intensity of the annealed wafer is more severe than the band edge emission intensity of the epitaxial wafer. This means that the surface layer of the annealed wafer has crystal defects that do not exist in the epitaxial wafer that is originally supposed to have few defects.
[0037]
Such a crystal defect evaluated from the photoluminescence spectrum is a defect in a region which is regarded as a defect-free region in the evaluation by the conventional light scattering method. Thus, by evaluating the decrease in band edge emission in the photoluminescence spectrum of the annealed wafer, it becomes possible to identify the presence of defects that could not be detected by the conventional light scattering method.
[0038]
As shown in FIG. 4, when the wavelength of the excitation light is 514.5 nm, the decrease in the band edge emission intensity of the annealed wafer is remarkable due to the influence of precipitates and structural defects deeper than 10 μm from the surface layer. Because it ends up. As shown in FIG. 5, when excitation light having a wavelength of 364 nm is used, it is possible to determine the presence or absence of defects only in a region closer to the surface layer.
[0039]
FIG. 6 is a distribution diagram of the band edge emission intensity of the annealed wafer measured using a laser beam having a wavelength of 364 nm. In the photoluminescence measuring apparatus 10 of FIG. 3, for example, the irradiation position of the laser beam is fixed, and the sample wafer is moved in the X direction and the Y direction by the movable sample holder 1 so that each (x, y) At the position, the spectrum of photoluminescence generated in the extreme surface layer region from the wafer surface to about several tens of nanometers is measured. Alternatively, the photoluminescence spectrum at each (x, y) position is measured by fixing the sample wafer on the sample holder 1 and causing the irradiation optical system 3 to scan the wafer with irradiation light using, for example, a deflector.
[0040]
The band edge emission intensity (that is, the intensity at a wavelength of 1150 nm in the photoluminescence spectrum) is extracted from the photoluminescence spectrum measured at each (x, y) position to obtain a two-dimensional distribution of the band edge emission intensity. Data of the band edge emission intensity at the extracted (x, y) position is stored in a storage medium. Furthermore, a graph in which the intensity of the band edge emission intensity is plotted three-dimensionally with respect to the vertical axis from such two-dimensional distribution data is the distribution diagram of FIG. From the band edge emission intensity distribution diagram of FIG. 6, it is possible to visually recognize the position where the emission intensity is reduced, its density, and the degree of intensity reduction.
[0041]
For example, in the graph of FIG. 6, there is a portion where the band edge emission intensity is steeply dropped as indicated by an arrow. It can be seen that the decrease in emission intensity correlates with the size of the defect, and the larger the degree of depression (decrease) on the plot, the larger the size of the defect.
[0042]
FIG. 7 shows a two-dimensional distribution of band edge emission intensity in a histogram. The horizontal axis represents the intensity of light emission, and the vertical axis represents the number of measurement points corresponding to the light emission intensity. In the hiss and gram in FIG. 7, the band edge emission intensity from 820 to 960 follows a normal distribution. On the other hand, there is a component that does not follow the normal distribution in the region where the band edge emission intensity is lower than 820, as indicated by the dashed circle A. Such a component corresponds to a drop in emission intensity due to wafer defects. That is, since electrons and holes are trapped and recombined at the defect position, the emission intensity at the band edge becomes weak, and a component that does not follow the normal distribution is generated. Such a reduced component of intensity deviating from the normal distribution can be evaluated in association with the structural defect of the wafer.
[0043]
FIG. 8 is obtained by removing the component according to the normal distribution from the plot result of FIG. As indicated by the solid circle, the position, density, and degree of decrease in the emission intensity become clearer, and the (x, y) position and defect density of the defect on the wafer can be calculated. Furthermore, by extracting only the drop (decrease) portion of the emission intensity indicated by the solid circle B in the figure and displaying it in an enlarged manner, the reduction in the band edge emission intensity can be observed in detail. Also, Light emission By quantifying the degree of strength reduction, the type and size of defects can be specified.
[0044]
As an example, when the decrease in emission intensity is 60 with the state in which the component according to the normal distribution is removed as a reference point, it can be recognized as a defect having a size of about 0.02 μm, and the decrease in emission intensity is 120. In this case, it can be recognized that the defect has a size of about 0.05 μm.
[0045]
FIG. 9 is a flowchart of a semiconductor wafer defect evaluation method according to an embodiment of the present invention. In step S101, excitation light with a wavelength of 800 nm or less, preferably 500 nm or less is irradiated onto the semiconductor wafer to be evaluated. This is because by selecting such a wavelength, it is possible to collect photoluminescence light reflecting information of the extreme surface layer region within 10 μm from the wafer surface.
[0046]
Next, in step S103, the spectrum of the photoluminescence light is measured at each point of the semiconductor wafer. Preferably, a photoluminescence spectrum is measured at each (x, y) position on the semiconductor wafer. It is sufficient to measure the photoluminescence spectrum in the range of 1700 nm or less. This is because in the case of a silicon wafer, band edge emission due to recombination of electrons and holes occurs in the vicinity of 1150 nm.
[0047]
Next, in step S105, the band edge emission intensity is extracted from the photoluminescence spectrum at each (x, y) position to obtain a two-dimensional distribution of hand edge emission intensity.
[0048]
In the case of roughly recognizing the presence / absence, density, defect size, etc. of the structural defect in the extreme surface region of the semiconductor wafer to be evaluated, the process proceeds to step S107, and from the two-dimensional distribution data of the band edge emission intensity obtained in step S105. Then, a three-dimensional plot (see FIG. 6) in which the emission intensity is taken on the vertical axis with respect to the XY coordinates is created, and the decrease in the emission intensity is visually observed. From the three-dimensional plot, the presence / absence of a structural defect, its approximate position, size, and density can be grasped.
[0049]
If more accurate information about the structural defect of the semiconductor wafer is required, the process proceeds to step S109, where the component according to the normal distribution is removed from the two-dimensional distribution data of the band edge emission intensity obtained in step S105, and the emission intensity is increased. Remove only the degraded components. As described above, the band edge emission intensity of the photoluminescence light trapped in the defect and recombined is significantly lower than the band edge emission intensity of the light recombined in the defect-free region, and depends on the size of the defect. The degree of strength reduction is different. Therefore, the defect can be analyzed in more detail by taking out only the strength lowering component.
[0050]
In step S111, the (x, y) position of the intensity decreasing component of the band edge emission is read, and the defect density is calculated. Further, the degree of the decrease in the emission intensity is quantified, and the size and type of the defect are specified according to the value. Although not shown, when extracting the intensity decreasing component in step S109, mapping data in which the intensity decreasing position and the intensity of the band edge emission are associated with each other may be created. Further, in step S111, the intensity-decreasing portion may be enlarged and displayed prior to position reading, distribution density calculation, intensity reduction quantification, etc., or simultaneously with these processes.
[0051]
By such an evaluation method, not only the presence or absence of a structural defect of 0.02 μm or less in the extreme surface layer region within 10 μm from the surface of the semiconductor wafer, but also the position, distribution density, and size of such a defect can be specified. . Therefore, it is possible to evaluate the semiconductor wafer defect more accurately and in detail.
[0052]
For example, if the defect is in the peripheral region of the wafer, or even if it is inside the wafer, the decrease in emission intensity is relatively small (for example, when trapped by implanted impurities), and integration with the target design rule If it does not seem to affect the operation of the circuit, this wafer can be a successful wafer. Conversely, if there is a portion where the emission intensity is significantly reduced inside the wafer, or the density of the reduced portion is high, the wafer is rejected.
[0053]
When producing a semiconductor device using such a wafer evaluation method, a plurality of semiconductor wafers cut out from a semiconductor ingot are prepared as a lot. An arbitrary wafer is extracted from the lot to be an evaluation wafer, which is set in the photoluminescence measuring apparatus shown in FIG. Then, in the procedure shown in the flow of FIG. 9, the laser light is irradiated, the spectrum of the photoluminescence light is measured at each (x, y) position on the wafer, and the intensity of the band edge emission is extracted. A two-dimensional distribution of the band edge emission intensity is acquired from the extracted band edge emission intensity, and the approximate position, density, and size of the defect are recognized from the two-dimensional distribution. Alternatively, the component according to the normal distribution is removed from the two-dimensional distribution of the band edge emission intensity, and the position, density, and size of the defect are specified, and the wafer is evaluated in detail.
[0054]
The acceptance / rejection of the evaluation wafer is determined based on the evaluation result. If the normal distribution component is not removed, and a pass / fail decision can be made visually from a graph (see FIG. 6) in which the band edge emission intensity distribution is plotted three-dimensionally, the pass / fail decision can also be made at that time. When the determination is delicate, the normal distribution component is removed from the band edge emission intensity distribution, the intensity-decreasing portion is enlarged, and quantitative analysis is performed, so that a pass / fail determination is made based on detailed information on the wafer defect. As a result of the pass / fail judgment, if the evaluation wafer is acceptable, the process proceeds to a step of forming a semiconductor integrated circuit on the semiconductor wafer of this lot. If the evaluation wafer is rejected, depending on the degree of failure, remove another wafer from the same lot and re-evaluate it, or reject the entire lot according to more detailed criteria. The manufacturing of the semiconductor device can proceed.
[0055]
The evaluation method described above can also be realized by software such as a wafer evaluation program. In this case, the wafer evaluation program causes the computer to extract the intensity of the band edge emission from the spectrum of the photoluminescence light at each position on the wafer, and to create the intensity distribution of the band edge emission. Then, from the emission intensity distribution at the band edge, a three-dimensional plot is created with the emission intensity taken on the vertical axis with respect to the two-dimensional coordinates on the wafer. Alternatively, the component according to the normal distribution is removed from the intensity distribution of the band edge emission, and the intensity-decreasing portion of the band edge emission is extracted from the intensity distribution after the removal of the normal distribution component, and is quantified or enlarged. Whether to perform three-dimensional plotting, quantification, or enlarged display may be performed according to the operation of the operator, or at least one of them may be automatically performed.
[0056]
The spectrum of the photoluminescence light may be read from data stored in advance in a storage medium, or may be sequentially processed according to an input from the photoluminescence measurement device. Further, the operator may make a pass / fail decision based on a three-dimensional plot, an enlarged display of a reduced intensity portion, or a quantified value, or a computer may automatically make a pass / fail decision.
[0057]
In the embodiment described above, the defect evaluation method of the extreme surface layer of the annealed wafer that is considered to be widely used in the next generation rule has been described as an example. However, the defect evaluation method of the present invention is a surface polished (polished) wafer, Needless to say, the present invention can be similarly applied to an epitaxial wafer, a CZ wafer, and the like.
[0058]
In the embodiment, in order to evaluate a structural defect of 0.02 μm (20 nm) or less in the extreme surface layer region where a depletion layer of a semiconductor element is formed, using the 0.07 μm rule as a target, excitation light having a wavelength of 364 nm However, in order to detect an extremely minute defect in a shallower surface region, an excimer laser having a wavelength of 300 nm or less may be used to irradiate the evaluation wafer.
[0059]
Finally, the following notes are disclosed regarding the above description.
(Appendix 1) A step of irradiating a semiconductor wafer with excitation light having a wavelength of 800 nm or less and measuring a spectrum of photoluminescence light generated from the semiconductor wafer;
Extracting the intensity of the band edge emission from the spectrum of the photoluminescence light, obtaining the intensity distribution of the band edge emission in the semiconductor wafer;
A step of evaluating defects in the surface layer of the semiconductor wafer from the intensity distribution of the hand edge emission;
A method for evaluating a semiconductor wafer, comprising:
(Supplementary note 2) The evaluation method according to supplementary note 1, further comprising a step of three-dimensionally plotting a relationship between the planar coordinates on the semiconductor wafer and the emission intensity from the intensity distribution of the band edge emission.
(Additional remark 3) The process of removing the component according to normal distribution from the intensity distribution of the said hand edge light emission,
A step of extracting a reduced portion of the emission intensity from the intensity distribution after removing the normal distribution component;
The method for evaluating a semiconductor wafer according to appendix 1, further comprising:
(Supplementary note 4) The evaluation method according to supplementary note 1, wherein the defect is evaluated based on at least one of a defect position, a distribution density, and a defect size.
(Additional remark 5) The said semiconductor wafer is an annealed wafer which performed annealing treatment, The evaluation method of Additional remark 1 characterized by the above-mentioned.
(Additional remark 6) The said excitation light is excitation light with a wavelength of 500 nm or less, The evaluation method of Additional remark 1 characterized by the above-mentioned.
(Additional remark 7) The evaluation method of Additional remark 3 characterized by further including the process of quantifying or the enlarged display of the fall part of the said emitted light intensity.
(Appendix 8) A step of cutting a plurality of semiconductor wafers from a semiconductor ingot into a lot;
A process of taking an arbitrary semiconductor wafer from the lot to make an evaluation wafer, and irradiating the evaluation wafer with excitation light having a wavelength of 800 nm or less, and measuring a spectrum of photoluminescence light at each point of the evaluation wafer Process,
Extracting the intensity of the band edge emission from the spectrum of the photoluminescence light, and obtaining the intensity distribution of the band edge emission in the wafer for evaluation;
A step of evaluating defects of the evaluation wafer based on the intensity distribution of the hand edge emission;
Determining pass / fail of the wafer for evaluation based on the evaluation result;
Forming a semiconductor element on the semiconductor wafer of the lot when the evaluation wafer is judged to be acceptable; and
A method for manufacturing a semiconductor device comprising:
(Additional remark 9) The manufacturing method of the semiconductor device of Additional remark 8 characterized by using the annealed wafer to which the annealing process was given as said semiconductor wafer.
(Additional remark 10) The manufacturing method of the semiconductor device of Additional remark 8 characterized by irradiating excitation light with a wavelength of 500 nm or less as said excitation light.
(Appendix 11)
From the spectrum of photoluminescence light at each position on the wafer, the intensity of the band edge emission is extracted, and the intensity distribution of the band edge emission is created.
From the emission intensity distribution at the band edge, remove the component according to the normal distribution,
From the intensity distribution after removal of the normal distribution component, the intensity-decreasing part of the band edge emission is extracted and quantified or enlarged.
A wafer evaluation program including an instruction sequence.
[0060]
【The invention's effect】
As described above, according to the present invention, it is possible to evaluate the position, distribution density, size, and the like of structural defects having a size of 0.02 μm or less in the extreme surface layer of a semiconductor wafer, particularly an annealed wafer.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a relationship between a design rule and a defect size in question.
FIG. 2 shows a typical photoluminescence spectrum of a silicon wafer.
FIG. 3 is a schematic view of a photoluminescence measuring apparatus used in an embodiment of the present invention.
FIG. 4 is a diagram showing photoluminescence spectra of an epitaxial wafer and an annealed wafer when irradiated with excitation light having a wavelength of 514.5 nm.
FIG. 5 is a diagram showing photoluminescence spectra of an epitaxial wafer and an annealed wafer when irradiated with excitation light having a wavelength of 364 nm.
FIG. 6 is a diagram showing a band edge emission intensity distribution of an annealed wafer.
FIG. 7 is a diagram showing the distribution of band edge emission intensity in a histogram.
FIG. 8 is a distribution diagram in a state in which a component according to a normal distribution is removed from a band edge emission intensity distribution, and an enlarged view of a portion where the band edge emission intensity decreases.
FIG. 9 is a flowchart of a wafer defect evaluation method according to an embodiment of the present invention.
[Explanation of symbols]
1 Sample holder
2 Laser
3 Irradiation optics
4 Condensing optical system
5 Spectrometer
6 Detector
10 Photoluminescence measuring device

Claims (6)

Irradiating a semiconductor wafer with excitation light having a wavelength of 800 nm or less, and measuring a spectrum of photoluminescence light generated from the semiconductor wafer;
Extracting the intensity of the band edge emission from the spectrum of the photoluminescence light, obtaining the intensity distribution of the band edge emission in the semiconductor wafer;
A step of evaluating void defects in the surface layer of the semiconductor wafer based on a decrease in emission intensity obtained from the intensity distribution of the band edge emission , and a semiconductor wafer evaluation method comprising:
Removing a component according to a normal distribution from the intensity distribution of the hand edge emission;
Extracting a reduced portion of the emission intensity from the intensity distribution after removing the normal distribution component;
A method for evaluating a semiconductor wafer , further comprising: A step of three-dimensionally plotting the relationship between the plane coordinates on the semiconductor wafer and the emission intensity from the intensity distribution of the band edge emission,
The method for evaluating a semiconductor wafer according to claim 1, wherein the decrease in the emission intensity is detected based on the three-dimensional plot. The evaluation of the void defects, the position of the void defect, distribution density, method for evaluating a semiconductor wafer according to claim 1, characterized in that on the basis of at least one void defect size. 2. The method for evaluating a semiconductor wafer according to claim 1, wherein in the evaluation step, a void defect of 0.02 μm or less is evaluated based on a decrease in the emission intensity. Cutting a plurality of semiconductor wafers from a semiconductor ingot into a lot; and
A step of taking an arbitrary semiconductor wafer from the lot and making it an evaluation wafer;
Irradiating the evaluation wafer with excitation light having a wavelength of 800 nm or less, and measuring a spectrum of photoluminescence light generated from the evaluation wafer;
Extracting the intensity of the band edge emission from the spectrum of the photoluminescence light, and obtaining the intensity distribution of the band edge emission in the wafer for evaluation;
A step of evaluating void defects of the evaluation wafer based on a decrease in emission intensity obtained from the intensity distribution of the band edge emission; and
Determining pass / fail of the wafer for evaluation based on the evaluation result;
And a step of forming a semiconductor element on the semiconductor wafer of the lot when the evaluation wafer is judged to be acceptable. 6. The method of manufacturing a semiconductor device according to claim 5 , wherein the evaluation step detects and evaluates a void defect of 0.02 [mu] m or less based on the decrease in the emission intensity.

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