JP5815330B2 - Semiconductor substrate analysis method - Google Patents

Description

  The technical field relates to a method for analyzing a semiconductor substrate. Further, the present invention relates to a method for manufacturing an SOI substrate.

  As a method for analyzing a silicon substrate with a single-layer structure without an internal structure, the lifetime of the silicon substrate (bulk lifetime) is obtained from the time change (decay curve) of the excess carrier density obtained by the μ-PCD (μ-wave photoconductive decay) method. A method for measuring (also called) is known. (See Patent Document 1).

  The lifetime is one of the indices indicating the size of defect levels in the semiconductor energy gap. When a defect level exists in a particularly deep position in the energy gap, carriers are recombined (disappeared) through the defect level. The lifetime is a measure of the time (lifetime) from the generation of carriers to the disappearance by recombination through the defect level. Since the frequency of recombination increases as the defect level increases, the lifetime decreases.

  Further, the μ-PCD method is an effective technique for measuring a lifetime because it can analyze a sample such as a semiconductor substrate nondestructively. The principle will be described below.

  The surface of the sample is irradiated with a laser and a microwave (also called a μ wave) at the same time. Excess carriers are generated in the sample by laser irradiation. When the laser irradiation is stopped, the carrier density returns to a thermal equilibrium state after a certain time due to recombination via defect levels in the energy gap. Here, by utilizing the correlation between the carrier density and the reflectance of the μ wave and detecting the reflected microwave, it is possible to follow the time change of the carrier density during the attenuation.

JP 59-55013 A

  However, there has been no attempt to analyze a semiconductor substrate having a multi-layer structure (also referred to as a multilayer structure) using the μ-PCD method. For example, for a semiconductor substrate having a DZ (denuded zone) layer in the vicinity of the surface and an IG (intrinsic gettering) layer inside, a separation evaluation method for the bulk lifetime and surface recombination velocity of each layer, or the thickness of the DZ layer No measurement method has been proposed.

  In view of the above, an object of one embodiment of the present invention is to measure bulk lifetime by a μ-PCD method in a semiconductor substrate having a multilayer structure.

  Another object of one embodiment of the present invention is to measure the thickness of a DZ layer by a μ-PCD method in a semiconductor substrate having a DZ layer on the surface.

  With respect to a semiconductor substrate having a multi-layer structure, an analysis is performed by superimposing a result of an experimental μ-PCD method and a result of a μ-PCD method by simulation (also referred to as fitting).

One embodiment of the present invention includes performing a μ-PCD method on the first semiconductor substrate from which the IG layer is exposed, using the IG layer side as an irradiation surface, and measuring the lifetime τ _A1 of the primary mode, A μ-PCD method is performed on the second semiconductor substrate having the DZ layer on one side, with the DZ layer side as the irradiation surface, and the lifetime of the primary mode τ _B1 and the primary mode with respect to the carrier density of all modes. measuring a first relation between the reciprocal R _B ratio of carrier density, by simulation using the lifetime tau _A1, the irradiation surface with respect to the model of the same structure as the second semiconductor substrate, the DZ layer side The lifetime of the primary mode τ _C1 and the carrier density of the primary mode relative to the carrier density of all modes when the μ-PCD method is performed and the thickness and surface recombination velocity of the DZ layer are changed. A step of obtaining a second relationship with a reciprocal number _RC of the ratio, and a step of superimposing the first relationship and the second relationship and measuring the thickness of the DZ layer in the second semiconductor substrate. This is a method for analyzing a semiconductor substrate.

In another embodiment of the present invention, the μ-PCD method is performed on the first semiconductor substrate from which the IG layer is exposed, using the IG layer side as an irradiation surface, and the lifetime τ _A1 of the primary mode is measured. A primary mode is performed by performing a μ-PCD method on a plurality of second semiconductor substrates having a DZ layer on at least one surface and having different surface treatment conditions, with each DZ layer side as an irradiation surface. And measuring the first relationship between the lifetime τ _B1 of the first mode and the reciprocal R _B of the ratio of the carrier density of the primary mode to the carrier density of all modes, and the second semiconductor by simulation using the lifetime τ _A1 For the model having the same structure as the substrate, the μ-PCD method is performed with the DZ layer side as the irradiation surface, and the lifetime τ _C1 of the first mode when the thickness of the DZ layer and the surface recombination velocity are changed are , All modes The step of obtaining a second relationship with a reciprocal _RC of the ratio of the carrier density of the primary mode to the carrier density, the first relationship, and the second relationship are overlapped, and the DZ layer in the second semiconductor substrate And a method of measuring the thickness of the semiconductor substrate.

  Note that the DZ layer of the first semiconductor substrate and the DZ layers of the plurality of second semiconductor substrates may be formed by annealing the semiconductor substrate in an inert atmosphere or a hydrogen atmosphere.

  In addition, a silicon substrate may be used as the first semiconductor substrate and the plurality of second semiconductor substrates.

  According to one embodiment of the present invention, a semiconductor substrate can be analyzed nondestructively.

  Further, according to one embodiment of the present invention, the thickness of the DZ layer in the semiconductor substrate can be measured.

The figure which shows an example of an attenuation curve. The figure which shows an example of the analysis method of a semiconductor substrate. The figure which shows an example of the analysis method of a semiconductor substrate. The figure which shows an example of the result of a μ-PCD method. The figure which shows an example of the analysis method of a semiconductor substrate. The figure which shows an example of the result of a μ-PCD method. The figure which shows an example of the result of a μ-PCD method. The figure which shows an example of the result of a μ-PCD method. The figure which shows an example of the analysis method of a semiconductor substrate. 10A and 10B illustrate a method for manufacturing an SOI substrate.

  Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments below. Note that in the structures of the present invention described below, the same reference numerals are used in common in different drawings.

(Embodiment 1)
In this embodiment, an example of a method for analyzing a semiconductor substrate having a multi-layer structure will be described. The analysis is performed by the following steps A to D.

<Process A>
The lifetime of the semiconductor substrate is measured by experiment. The μ-PCD method is performed on the semiconductor substrate from which the IG layer is exposed, using the IG layer side as an irradiation surface, and the lifetime τ _A1 of the primary mode is measured.
<Process B>
The lifetime of the semiconductor substrate is measured by an experiment different from the process A. A μ-PCD method is performed on a semiconductor substrate having a DZ layer on at least one surface, with the DZ layer side as an irradiation surface. Then, measured between lifetime tau _B1 of the primary mode, the relationship between the reciprocal R _B ratio of the carrier density of the primary mode for the carrier density in all modes (also referred to as a first relationship).
<Process C>
The lifetime of the semiconductor substrate is obtained by simulation. Using the lifetime τ _A1 measured in the process A, a μ-PCD method simulation is performed on the model having the same structure as the semiconductor substrate used in the process B with the DZ layer side as an irradiation surface. Then, the lifetime τ _C1 of the primary mode and the reciprocal _RC of the ratio of the carrier density of the primary mode to the carrier density of all modes are obtained. Further, a relationship (also referred to as a second relationship) between the lifetime τ _C1 and the reciprocal number _{RC of the} ratio when the thickness of the DZ layer and the surface recombination velocity are changed is obtained.
<Process D>
The result of the experiment in the process B (first relation) and the result of the simulation in the process C (second relation) are superimposed, and the thickness of the DZ layer in the semiconductor substrate used in the process B is measured.

In the present embodiment, the lifetime τ ₁ (τ _A1 , τ _B1 , and τ _C1 ) of the first-order mode and the reciprocal R (R _B and R _C ) of the ratio play an important role. Therefore, first, a method for obtaining the lifetime τ ₁ and the reciprocal R of the ratio will be described, and then specific examples of each process will be described.

<Method for obtaining lifetime τ ₁ and reciprocal R of ratio>
FIG. 1 shows a change over time in the density of excess minority carriers (also referred to as carrier density) generated by the μ-PCD method. The resulting curve is called the decay curve. The vertical axis is a logarithmic display of the carrier density n (the carrier density of all modes (total at time t = 0) is normalized to 1), and the horizontal axis is the time t [μsec].

  FIG. 1 shows all modes (solid line, total: superposition of an infinite number of eigenmodes) and a primary mode (dashed line). The second half of the attenuation curve is almost a straight line in logarithmic display. This means that with the passage of time, the high-order mode is quickly attenuated and only the primary mode remains.

From FIG. 1, it is possible to obtain the lifetime τ _{1 of} the primary mode and the reciprocal R of the ratio in each step. The primary mode lifetime τ ₁ is the time constant of the mode with the longest time constant among the infinite number of eigenmodes.

First, the lifetime τ ₁ of the primary mode is obtained from FIG. The lifetime τ ₁ of the primary mode is proportional to the reciprocal of the slope of the straight line portion in the attenuation curve of the primary mode. That is, by obtaining the inclination, the lifetime τ ₁ of the primary mode can be obtained.

  Further, the reciprocal R of the ratio is obtained from FIG. The ratio is an intercept with the vertical axis in the attenuation curve of the first-order mode. That is, the inverse number R of the ratio can be obtained by obtaining the intercept. Note that the attenuation curve of the first-order mode is extrapolated by a first-order function.

  The method using the above attenuation curve can be applied to each step. Specific examples of Step A to Step D are shown below.

<Specific example of step A>
In step A, the μ-PCD method is performed on the semiconductor substrate from which the IG layer is exposed, using the IG layer side as an irradiation surface, and the lifetime of the semiconductor substrate is measured. That is, the measured value of lifetime is obtained.

  FIG. 2 is an example of a semiconductor substrate used in step A.

FIG. 2A shows a silicon substrate Si having a DZ layer DZ (thickness L _DZ ) on one surface. The x direction indicates the depth direction of the silicon substrate Si.

  The DZ layer DZ is formed, for example, by annealing the silicon substrate Si in an inert atmosphere such as argon, helium, or nitrogen, or in a hydrogen atmosphere. By performing the annealing, oxygen or the like in the vicinity of the surface of the silicon substrate Si is diffused outward, and a layer with few crystal defects (DZ layer DZ) can be formed in the vicinity of the surface. The formation method of DZ layer DZ is not limited to this.

  Then, a layer (IG layer IG) having an overwhelming number of crystal defects is formed inside the vicinity of the surface (inside the DZ layer DZ) compared to the DZ layer DZ. That is, the silicon substrate Si has a DZ layer DZ on one surface and an IG layer IG on the other surface and inside.

  Therefore, the silicon substrate Si does not have the DZ layer DZ on the other surface. Such a silicon substrate Si can be obtained by forming a DZ layer on both sides and then scraping it so as to completely remove the DZ layer on one side (FIG. 2B).

  The film thickness of the DZ layer DZ (generally 10 μm or more and 50 μm or less) is sufficiently thinner than the film thickness of the silicon substrate Si (generally 500 μm or more and 1 mm or less).

  Further, as shown in FIG. 2C, a silicon substrate Si from which the DZ layer DZ on both sides is removed after the DZ layer DZ is formed on both sides may be used. In this case, the silicon substrate Si has a single layer structure of the IG layer IG.

  That is, in the process A, the silicon substrate Si from which the IG layer IG on at least one surface is exposed can be used.

  A semiconductor substrate other than a silicon substrate can also be used. For example, a compound semiconductor substrate such as a silicon germanium substrate or a silicon carbide substrate may be used. Note that a single crystal semiconductor, a polycrystalline semiconductor, or the like can be used.

  In this example, the μ-PCD method is performed on the silicon substrate Si shown in FIG. 2A using the IG layer IG side as an irradiation surface, and the lifetime of the silicon substrate Si is measured. That is, the measured value of lifetime is obtained.

  First, as shown by the arrow in FIG. 3, the irradiation surface is the IG layer IG side of the silicon substrate Si, and laser and μ waves are irradiated.

Then, an attenuation curve as shown in FIG. By the method described above, the lifetime τ _A1 of the primary mode when the IG layer IG side is the irradiation surface is obtained.

As described above, in the process A, the lifetime τ _A1 when the IG layer side is the irradiation surface can be measured.

<Specific example of process B>
In step B, a μ-PCD method is performed on a semiconductor substrate having a DZ layer on at least one surface with the DZ layer side as an irradiation surface, and the lifetime of the semiconductor substrate is measured. That is, actual values such as lifetime are obtained.

  FIG. 5 is an example of a semiconductor substrate used in step B.

  FIG. 5A shows a silicon substrate Si having DZ layers DZ on both sides. The method for forming the DZ layer DZ may be performed in the same manner as in step A.

  Further, as shown in FIG. 5B, a silicon substrate Si having a DZ layer DZ on one surface may be used. In that case, the substrate used in step A can be used.

  That is, in the process B, a silicon substrate having the DZ layer DZ on at least one surface can be used.

  In this example, a silicon substrate Si having DZ layers on both sides as shown in FIG.

  First, as shown by an arrow in FIG. 5C, a laser and μ wave are irradiated using one surface of the silicon substrate Si as an irradiation surface. That is, the irradiated surface is on the DZ layer DZ side.

Then, an attenuation curve as shown in FIG. The above-described method, when used as a radiation surface DZ layer DZ side, the lifetime tau _B1 of the primary _mode, and obtains the reciprocal R _B ratio of the carrier density of the primary mode for the carrier density in all modes.

As described above, in the step B, when used as a radiation surface DZ layer side, it is possible to measure the lifetime tau _B1 and the proportion of the reciprocal R _B. FIG. 6A shows a relationship (referred to as a first relationship) between the obtained lifetime τ _B1 and the reciprocal number R _{B of the} ratio. In FIG. 6A, the vertical axis represents the reciprocal number R _B of the ratio, and the horizontal axis represents the lifetime τ _B1 [μsec] of the primary mode. The first relationship is used in step D.

<Specific example of process C>
In the process C, the experiment of the process B is performed by simulation using the lifetime τ _A1 measured in the process A. That is, a calculated value such as lifetime is obtained.

  The model of the semiconductor substrate used for the simulation is a model having the same structure as that of the semiconductor substrate used in the process B. Therefore, in this example, the same model of FIG. Note that a model as shown in FIG. 5B can be used as long as it is the same model of the semiconductor substrate as in the process B. That is, it is only necessary to have the DZ layer DZ on at least one surface.

  As shown in FIG. 5C, a μ-PCD method simulation is performed using one surface of the silicon substrate Si as an irradiation surface. That is, the irradiated surface is on the DZ layer DZ side.

Here, if the irradiation surface of DZ layer DZ side, to the simulation of mu-PCD method in the silicon substrate Si, it is necessary to give lifetime tau _IG of IG layer IG, the lifetime tau _DZ of DZ layer DZ. However, instead, it is sufficient to give either 1 / τ _IG -1 / τ _DZ and τ _IG , or a combination of either 1 / τ _IG -1 / τ _DZ and τ _DZ .

As described above, the crystal defects of the DZ layer DZ are much smaller than the crystal defects of the IG layer IG. Therefore, the lifetime τ _DZ is much larger than the lifetime τ _IG .

Therefore, the approximation 1 / τ _IG −1 / τ _DZ = 1 / τ _IG holds.

Here, as the lifetime τ _IG of the IG layer IG, it is possible to use the result (actual value τ _A1 obtained in the step A) obtained by the μ-PCD method when the IG layer IG side is the irradiation surface (described later). Reference <Derivation Process of τ _IG = τ _A1 >). That is, it is possible to τ _IG = τ _A1. Therefore, the approximation 1 / τ _IG −1 / τ _DZ = 1 / τ _IG = 1 / τ _A1 holds.

Then, by solving the differential equation of the carrier density, it is possible to calculate the reciprocal number _RC of the ratio of the carrier density of the primary mode to the lifetime τ _{C1 of the} primary mode and the carrier density of all modes (see later <Solution>).

Further, when the irradiation surface is the DZ layer DZ side, the lifetime of the primary mode of the silicon substrate Si changes according to the thickness L _DZ of the DZ layer and the surface recombination velocity S of the silicon substrate Si. The surface recombination velocity S is an index indicating the surface state of the semiconductor substrate, and varies depending on the surface treatment (also referred to as surface passivation).

Therefore, in this example, the thickness L _DZ of the DZ layer is three types of 30 μm, 40 μm, and 50 μm, and the surface recombination speed S is 10 cm / sec, 20 cm / sec, 50 cm / sec, 100 cm / sec, 200 cm / sec, Eight types of 500 cm / sec, 1000 cm / sec, and 2000 cm / sec are used, and the relationship (second relationship) between the lifetime τ _C1 and the reciprocal number _{RC of the} ratio is obtained. FIG. 6B shows the obtained second relationship. In FIG. 6B, the vertical axis represents the reciprocal number _RC of the ratio, and the horizontal axis represents the lifetime τ _C1 [μsec] of the primary mode.

In FIG. 6B, the three curves are obtained from differences in the thicknesses L _DZ of the three types of DZ layers. In addition, eight pieces of data in each curve are obtained from the difference in eight kinds of surface recombination rates S. The second relationship is used in step D.

  In addition, the order of the process B and the process C is not limited. Therefore, step B may be performed after step C.

<Specific example of process D>
In step D, the first relationship obtained in step B (FIG. 6A) and the second relationship obtained in step C (FIG. 6B) are superimposed (FIG. 6C )).

From FIG. 6C, the thickness L _DZ of the DZ layer of the silicon substrate used in the process B can be estimated. In this example, the thickness L _DZ of the DZ layer is estimated to be 30 μm to 40 μm.

  By using the method of this embodiment mode, the lifetime of a semiconductor substrate having a multi-layer structure or the thickness of a DZ layer can be measured nondestructively.

In Step C, the number of curves in FIG. 6B can be increased by finely shaking the thickness L _DZ of the DZ layer. By doing so, the thickness of the DZ layer can be measured with higher accuracy.

  In this embodiment, a silicon substrate having a DZ layer and an IG layer is used as a semiconductor substrate having a multi-layer structure, but the present invention is not limited to this. A semiconductor substrate having a plurality of layers with different numbers of crystal defects can be analyzed.

<Derivation process of τ _IG = τ _A1 >
In step C, the approximation is made as τ _IG = τ _A1, and the derivation process is shown below.

FIG. 8 shows the result of the simulation of the μ-PCD method using FIG. 2A as the model of the semiconductor substrate and using the IG layer IG side as the irradiation surface. That is, it is a result of conducting an experiment by the process A by simulation. In addition, (tau) ₁ was calculated by extrapolating the linear part of the attenuation | damping curve obtained by calculation.

In this simulation, the lifetime τ _IG of the IG layer IG is set to 1 μsec, the surface recombination velocity S and the thickness L _DZ of the DZ layer are widely changed, and the lifetime τ ₁ of the primary mode is obtained. The vertical axis represents the lifetime τ ₁ of the primary mode, and the horizontal axis represents the surface recombination velocity S.

From FIG. 8, it is recognized that when the IG layer IG side is the irradiated surface, the lifetime τ ₁ is substantially constant regardless of the surface recombination velocity S and the thickness L _DZ of the DZ layer. That is, the approximation τ ₁ = τ _IG holds.

Therefore, the lifetime τ _A1 obtained from the process A can be calculated as the life lime τ _IG of the IG layer IG.

From the above, in step C, τ _IG = τ _A1 can be obtained.

<Solution of differential equation>
In step C, each value was obtained from the solution of the differential equation of carrier density. The calculation process is as follows.

As shown in FIG. 9, in the silicon substrate Si, the coordinate of one surface is x ₂ , the coordinate of the other surface is −x ₂ , and the coordinate of the interface between the DZ layer DZ and the IG layer IG is x = x ₁ and x = −x ₁ , −x ₁ ≦ x ≦ x ₁ is an IG layer IG, and −x ₂ ≦ x ≦ −x ₁ and x ₁ ≦ x ≦ x ₂ are DZ layers DZ. Further, the bulk lifetime of the DZ layer DZ is τ _DZ , and the bulk lifetime of the IG layer IG is τ _IG . Considering the case where the surface recombination speeds of both sides of the silicon substrate Si are equal, both are set to S. This structure is inversion symmetric with respect to x = 0.

  Here, attention is focused on excess minority carriers obtained by laser irradiation. Then, Equation 1 is used as a differential equation that the carrier density follows. Note that drift is ignored, including only diffusion and recombination effects, assuming low level injection.

Here, D is a diffusion constant of minority carriers. Further, τ _{b in} the second term on the right side is τ _{DZ in the} DZ layer DZ and τ _{IG in the} IG layer IG, and therefore differs from a semiconductor substrate having a single layer structure in that τ _b depends on x. Furthermore, Formula 2, which is a boundary condition considering recombination on the surface, is imposed.

  Furthermore, Formula 3 is introduced as a boundary condition at the interface between the DZ layer DZ and the IG layer IG. Here, from analogy of quantum mechanics, it is assumed that the carrier density at the interface between the DZ layer DZ and the IG layer IG and the first derivative thereof are continuously connected at the interface between the DZ layer DZ and the IG layer IG.

When the differential equation is solved under various boundary conditions, infinite eigenmodes characterized by discrete time constants τ _i are obtained. The calculated primary mode lifetime τ ₁ is the time constant of the mode with the longest time constant among the eigenmodes.

  If a carrier injection profile at time t = 0 is given as an initial condition, a simulation with respect to time change can be performed.

The initial carrier injection profile is approximated to n (x, t = 0) ∝exp (−αx) using the absorption coefficient α determined by the wavelength of the incident light and the sample. This profile is represented by a superposition of eigenmodes _{φ i exp (-αx) = ΣA} i φ i. The superposition formation A _i can be calculated using the orthogonal function of φ _i .

From the above, the solution of the carrier density n (x, t) is n (x, t) = ΣA _i φ _i (x) exp (−t / τ _i ).

Further, from this solution, an attenuation curve as shown in FIG. 1 can be obtained, and the reciprocal _RC of the ratio of the carrier density of the primary mode to the carrier density of all modes can be calculated. The carrier density is integrated with respect to x.

As described above, the lifetime τ _C1 and the reciprocal number _RC of the ratio can be obtained.

In step C, the surface recombination velocity S and the thickness L _DZ of the DZ layer are changed to obtain the lifetime τ _C1 and the reciprocal number _RC of the ratio.

  This embodiment can be implemented in appropriate combination with any of the other embodiments.

(Embodiment 2)
In the present embodiment, as a method for analyzing a semiconductor substrate, a modification of the process B in the first embodiment is shown.

<Modification of process B>
Embodiment 1, in step B, is to obtain the relationship between lifetime tau _B1 and percentage of reciprocal R _B by a single data (first relationship).

  On the other hand, in the present embodiment, the first relationship is obtained from a plurality of data. That is, like the second relationship obtained in step C, the first relationship may be shown by a curve corresponding to the change in the surface recombination velocity S.

  Therefore, in this example, an experiment is performed using a plurality of silicon substrates. The silicon substrate used is the same as that shown in FIG. When forming the DZ layer DZ, the process conditions are the same for a plurality of silicon substrates, and the thickness of the DZ layer is made uniform.

  Then, surface treatment (also referred to as surface passivation) is performed on a plurality of silicon substrates under different conditions. By changing the surface treatment conditions, the bulk lifetime of each layer does not change, and only the surface recombination velocity S changes. Therefore, the obtained first relationship can be shown by a curve corresponding to the surface recombination treatment S.

  Here, thermal oxidation treatment is performed on the four silicon substrates as surface treatment. Then, silicon oxide films having thicknesses of 50 nm, 100 nm, 150 nm, and 200 nm are formed on the surfaces of the four silicon substrates, respectively. Note that the number of silicon substrates and the thickness of the silicon oxide film are not limited.

  Further, the surface treatment is not limited to the thermal oxidation treatment, and a treatment for changing the surface recombination rate S may be performed. For example, a process for providing an insulating layer by a CVD method, a hydrochloric acid oxidation process, or the like may be performed.

Then, with respect to four silicon substrate, subjected to mu-PCD method DZ layer side surface treatment is performed as an irradiation surface, measuring the reciprocal R _B lifetime tau _B1 and proportions of the primary mode. Then, a relationship (first relationship) between the lifetime τ _B1 and the reciprocal number R _{B of the} ratio is obtained. FIG. 7A shows the first relationship with a curve.

  Then, the first relationship (FIG. 7A) and the second relationship obtained in step C (FIG. 7B) are overlapped (FIG. 7C). Note that the second relationship is the same as that obtained in Step C of Embodiment 1 (FIG. 6B).

  From FIG. 7C, the thickness of the DZ layer in the four silicon substrates used in the process B can be estimated. In this example, the thickness of the DZ layer is estimated to be 30 μm to 40 μm.

In this embodiment, the use of a plurality silicon substrate, it is possible to indicate the relationship between lifetime tau _B1 and percentage of reciprocal R _B by a curve. By doing so, the thickness of the DZ layer can be measured with higher accuracy.

Further, the number of curves in FIG. 7B can be increased by finely shaking the thickness L _DZ of the DZ layer in step C. By doing so, the thickness of the DZ layer can be measured with higher accuracy.

  This embodiment can be implemented in appropriate combination with any of the other embodiments.

(Embodiment 3)
In this embodiment, a method for manufacturing an SOI (Silicon On Insulator) substrate using the semiconductor substrate analyzed by the method of Embodiment 1 or 2 will be described.

  First, the semiconductor substrate 101 is prepared (FIG. 10A). As the semiconductor substrate 101, the one analyzed by the method of Embodiment 1 or Embodiment 2 is used.

  Next, the semiconductor substrate 101 is irradiated with ions 103 to form a damaged region 105 at a predetermined depth (FIG. 10B).

  The damaged region 105 can be formed by irradiating the semiconductor substrate 101 with ions (ion beams) 103 accelerated by an electric field and introducing the ions 103 to a predetermined depth from the surface of the semiconductor substrate 101. Note that a damaged region can be formed inside the DZ layer by using the semiconductor substrate 101 in which the thickness of the DZ layer is measured.

  Irradiation with the ions 103 can be performed by ion doping or ion implantation using ions of hydrogen, an inert element (eg, helium), or halogen (eg, fluorine).

  Next, the support substrate 107 is prepared (FIG. 10C).

  As the support substrate 107, a substrate made of an insulator such as glass, plastic, ceramic, quartz, or sapphire, a substrate made of a semiconductor such as silicon, or a substrate made of a conductor such as metal or stainless steel can be used.

  Next, the semiconductor substrate 101 and the supporting substrate 107 are attached to each other with the insulating layer 109 interposed therebetween (FIG. 10D). The bonding is performed using the side of the semiconductor substrate 101 where the damaged region 105 is formed as a bonding surface (also referred to as a bonding surface).

  The insulating layer 109 functions as a bonding layer for bonding two substrates, and may be formed over the semiconductor substrate 101 or the support substrate 107. In the case where the insulating layer 109 is formed over the semiconductor substrate 101, the insulating layer 109 may be formed before the ion 103 irradiation.

  The insulating layer 109 may be formed by a single layer or a stack of oxides, nitrides, or the like by a CVD method. Specific examples of the material include silicon oxide, silicon nitride, silicon oxynitride, and silicon nitride oxide.

  Note that silicon oxynitride has a higher oxygen content than nitrogen, and silicon nitride oxide has a higher nitrogen content than oxygen. Here, the content is compared based on the measurement results of the Rutherford backscattering method and the hydrogen forward scattering method.

  In addition, surface treatment may be performed on the bonding surfaces of the two substrates before bonding. By performing the surface treatment, hydrophilicity or cleanliness is improved, and bonding strength at the time of bonding can be improved. Note that the surface treatment may be performed on at least one of the two substrates. In addition, when surface treatment is performed on the substrate over which the insulating layer 109 is formed, the surface treatment is performed on the surface of the insulating layer 109.

  Next, heat treatment is performed, and the semiconductor substrate 101 is separated (also referred to as division) in the damaged region 105 (FIG. 10E). By the separation, the insulating layer 109 and the semiconductor layer 111 including a part of the semiconductor substrate 101 can be sequentially provided over the supporting substrate 107. That is, the semiconductor layer 111 including a part of the semiconductor substrate 101 can be transferred onto the support substrate 107.

  Note that the heat treatment may be performed at a temperature of 300 ° C. or higher and lower than the strain point of the support substrate 107.

  In this manner, the SOI substrate 113 can be manufactured.

  By using the analysis method of Embodiment 1 or Embodiment 2, the thickness of the DZ layer of the semiconductor substrate can be measured in advance. Then, by forming a damaged region inside the DZ layer and transferring a part of the DZ layer, a semiconductor layer with few crystal defects can be obtained.

  Note that an SOI substrate is a general term for a semiconductor substrate provided with an insulating layer on a supporting substrate, and is not limited to a substrate having a silicon layer.

  A semiconductor device such as a transistor or a diode can be manufactured using this SOI substrate.

  In addition, various electronic devices can be manufactured using the semiconductor element. Examples of the electronic device include a display device such as a television, a personal computer, a video camera, a digital camera, a navigation system, or a portable information terminal (such as a mobile phone, an electronic book, or a portable game machine). A circuit using the semiconductor element can be provided in a display portion or a peripheral portion of these display devices.

  Further, as another example of the electronic apparatus, a display unit may not be essential, and examples thereof include various devices such as a wireless tag, an authentication device, a lighting device, and an air conditioner. A circuit using the semiconductor element can be provided in these devices.

  Examples of the circuit include a circuit that can use the semiconductor element, such as a pixel circuit, a driver circuit, an arithmetic circuit, a sensor circuit, a power supply circuit, or a memory circuit.

  This embodiment can be implemented in appropriate combination with any of the other embodiments.

101 Semiconductor substrate 103 Ion 105 Damaged region 107 Support substrate 109 Insulating layer 111 Semiconductor layer 113 SOI substrate

Claims (2)

Performing a μ-PCD method on the first semiconductor substrate from which the IG layer is exposed, using the IG layer side as an irradiation surface, and measuring the lifetime τ _A1 of the primary mode;
A μ-PCD method is performed on a second semiconductor substrate having a DZ layer on at least one surface, with the DZ layer side as an irradiation surface, and the primary mode lifetime τ _B1 and the primary mode with respect to the carrier density of all modes. Measuring a first relationship with a reciprocal number R _B of the ratio of the carrier density of
Based on the simulation using the lifetime τ _A1 , a μ-PCD method is performed on the model having the same structure as that of the second semiconductor substrate with the DZ layer side as an irradiation surface, and the thickness and surface recombination of the DZ layer Determining a second relationship between the lifetime of the primary mode τ _C1 when the speed is changed and the reciprocal _RC of the ratio of the carrier density of the primary mode to the carrier density of all modes;
A method for analyzing a semiconductor substrate, comprising: superimposing the first relationship and the second relationship and measuring a thickness of the DZ layer in the second semiconductor substrate. Performing a μ-PCD method on the first semiconductor substrate from which the IG layer is exposed, using the IG layer side as an irradiation surface, and measuring the lifetime τ _A1 of the primary mode;
A primary mode lifetime is obtained by performing a μ-PCD method on a plurality of second semiconductor substrates having a DZ layer on at least one surface and having different surface treatment conditions, with each DZ layer side as an irradiation surface. and tau _B1, measuring a first relation between the reciprocal R _B ratio of the carrier density of the primary mode for the carrier density in all modes,
Based on the simulation using the lifetime τ _A1 , a μ-PCD method is performed on the model having the same structure as that of the second semiconductor substrate with the DZ layer side as an irradiation surface, and the thickness and surface recombination of the DZ layer Determining a second relationship between the lifetime of the primary mode τ _C1 when the speed is changed and the reciprocal _RC of the ratio of the carrier density of the primary mode to the carrier density of all modes;
A method for analyzing a semiconductor substrate, comprising: superimposing the first relationship and the second relationship and measuring a thickness of the DZ layer in the second semiconductor substrate.

Images