JP7415889B2 - Epitaxial wafer for X-ray sensor and X-ray sensor - Google Patents

Description

The present invention relates to an epitaxial wafer for an X-ray sensor and an X-ray sensor.

2. Description of the Related Art Conventionally, in the medical and industrial fields, X-ray sensors capable of non-destructively inspecting objects have been used. In this type of X-ray sensor, the received X-rays are generated by electrons generated by the photoelectric effect or Compton scattering inside a semiconductor such as silicon or germanium, and electron-hole pairs are generated according to the energy of all or part of the received X-rays. There is a method that detects electron-hole pairs by accelerating them using an electric field and collecting them on an electrode.

For example, in Non-Patent Document 1, an X-ray detection element and a signal processing circuit are manufactured separately, and both are connected by bonding using metal bumps. However, in the X-ray sensor described in Non-Patent Document 1, a high yield is required for each of the X-ray detection element and the signal processing circuit, and when miniaturization is required, there is a technology to reduce the size of the metal bumps as well. It was necessary to establish the system, and there were problems with many development elements.

Therefore, in recent years, an X-ray sensor has been proposed in which both an X-ray detection element and a signal processing circuit are integrally formed. For example, in Non-Patent Document 2, using an SOI wafer, an X-ray detection element is formed in a bulk silicon region on one side of an insulating oxide film, a signal processing circuit is formed in a bulk silicon region on the other side, and these are insulated. An X-ray sensor is described that is electrically connected via a via formed in an oxide film.

2007 STRJ Annual Report, Chapter 9, 9-5-2. Tsuru Tsuyoshi et al., “Development of photon-counting X-ray CMOS-SOI pixel detector capable of trigger output”, Proceedings of the 79th Japan Society of Applied Physics Autumn Academic Conference, 2018, 21p-224B-4

In the X-ray detection sensor using an SOI wafer described in Non-Patent Document 2, because the thermal conductivity of the insulating oxide film of the SOI wafer is low, the heat generated during X-ray detection accumulates inside the sensor. There is a risk of self-heating and malfunction.

The present invention has been made in view of the above problems, and its purpose is to prevent heat generated during X-ray detection from accumulating inside the sensor when an X-ray sensor is formed on a wafer. An object of the present invention is to provide a wafer for an X-ray sensor that can suppress the

The present invention for solving the above problems is as follows.
[1] An epitaxial wafer for X-ray sensors,
A silicon wafer having a thickness of 100 μm or more, a resistivity of 1000 Ω·cm or more, and an oxygen concentration of 1×10 ¹⁷ atoms/cm ³ or less, and containing no COPs or dislocation clusters;
a silicon epitaxial layer provided on the surface of the silicon wafer and having a device formation region with an oxygen concentration of 2×10 ¹⁶ atoms/cm ³ or less;
An epitaxial wafer for an X-ray sensor, comprising:

[2] The silicon wafer has an X-ray detection element formation region in which an X-ray detection element for detecting X-rays is formed, and the device formation region in the silicon epitaxial layer processes signals from the X-ray detection element. The epitaxial wafer for an X-ray sensor according to [1] above, which has a signal processing circuit formation region in which a circuit is formed.

[3] The epitaxial wafer for an X-ray sensor according to [1] or [2], further comprising a gettering sink provided on the back surface of the silicon wafer.

[4] A plurality of X-ray detection elements that receive and detect X-rays, formed on the silicon wafer of the epitaxial wafer for an X-ray sensor according to any one of [1] to [3] above;
a signal processing circuit for processing signals from the X-ray detection element, formed in the silicon epitaxial layer for each of the plurality of X-ray detection elements;
Equipped with
An X-ray sensor, wherein a pair of the X-ray detection element and the signal processing circuit are separated from each other.

According to the present invention, it is possible to suppress heat generated during X-ray detection from accumulating inside the sensor.

1 is a diagram showing a preferred example of an epitaxial wafer for an X-ray sensor according to the present invention. FIG. 3 is a diagram illustrating the relationship between the ratio of the crystal pulling rate to the temperature gradient in the crystal pulling direction and the crystal defect distribution when growing a silicon crystal by the Czochralski method. 1 is a diagram showing an example of an X-ray sensor according to the present invention. FIG. 3 is a diagram showing the structure of a pn junction diode used in Examples.

(Epitaxial wafer for X-ray sensor)
Embodiments of the present invention will be described below with reference to the drawings. The epitaxial wafer for X-ray sensors according to the present invention has a thickness of 100 μm or more, a resistivity of 1000 Ω·cm or more, and an oxygen concentration of 1×10 ¹⁷ atoms/cm ³ or less, and does not contain COPs or dislocation clusters. It is characterized by comprising a silicon wafer and a silicon epitaxial layer provided on the surface of the silicon wafer and having a device formation region with an oxygen concentration of 2×10 ¹⁶ atoms/cm ³ or less.

As described above, an X-ray sensor is formed using the SOI wafer described in Non-Patent Document 2, and by using the SOI wafer, it is possible to achieve good element isolation and reduction of parasitic capacitance. However, since the thermal conductivity of the insulating oxide film is low, the heat generated by X-ray detection is accumulated within the sensor, causing self-heating, which may cause malfunction.

The inventors of the present invention have conducted intensive studies on wafers that can suppress the accumulation of heat generated when X-rays are detected, compared to SOI wafers. As a result, we came up with the idea of using an epitaxial wafer that does not have an insulating oxide film like an SOI wafer. The present inventor has developed a silicon wafer that constitutes an epitaxial wafer that is free from grown-in defects (COPs and dislocation clusters), has a low oxygen concentration (1×10 ¹⁸ atoms/cm ³ or less), and has a high resistance (1000 Ω・cm 3 or less). (above), the silicon epitaxial layer is configured to have a sufficient thickness (100 μm or more) to detect X-rays, and the silicon epitaxial layer is thick enough to form a signal processing circuit that processes signals from the X-ray detection element. It was discovered that if the X-ray sensor is configured to have a region with a low oxygen concentration (2×10 ¹⁶ atoms/cm ³ or less), heat accumulation inside the sensor can be suppressed, and the present invention was completed. Each configuration will be explained below.

FIG. 1 shows a preferred example of an epitaxial wafer for an X-ray sensor according to the present invention. The epitaxial wafer 1 for an X-ray sensor shown in FIG. 1 includes a silicon wafer 11, a silicon epitaxial layer 12, and a gettering sink 13. The silicon epitaxial layer 12 has a transition region 12b into which oxygen from the silicon wafer 11 is diffused, and a device formation region 12a into which oxygen is not diffused.

The silicon wafer 11 has a region for forming an X-ray detection element of an X-ray sensor (X-ray detection element formation region). In order to form an X-ray detection element, the silicon wafer 11 must be free of grown-in defects, have high resistance, and have sufficient thickness to detect X-rays.

First, Grown-in defects refer to vacancy agglomerated defects (Crystal Originated Particles, COPs) formed by agglomeration of vacancies, dislocation clusters where interstitial silicon precipitates, etc., and remain in manufactured silicon wafers. This may cause leakage current in the X-ray sensor. Therefore, it is necessary that the silicon wafer 11 has no grown-in defects.

The silicon wafer 11 free of COPs and dislocation clusters is obtained by performing wafer processing on a single crystal silicon ingot (hereinafter also referred to as "silicon crystal") grown by the floating zone (FZ) method. ,Obtainable.

Further, the silicon wafer 11 without Grown-in defects is obtained by wafer processing on a silicon crystal composed of regions free of COPs and dislocation clusters among single crystal silicon ingots grown by the Czochralski (CZ) method. It can be obtained by processing.

When growing a silicon crystal by the CZ method, the behavior of vacancies and interstitial silicon introduced into the silicon crystal from the solid-liquid interface is explained by Voronkov's model (for example, V.V. Voronkov, J. (See Crystal Growth, 59, 625 (1982)). That is, the ratio v/G of the crystal pulling speed v to the temperature gradient G in the pulling direction of single crystal silicon near the solid-liquid interface is larger than a critical value (hereinafter also referred to as "critical v/G"). In this case, the vacancies are introduced more predominately than the interstitial silicon, and during the temperature drop, the interstitial silicon disappears due to annihilation reactions, leaving only the vacancies. On the other hand, when the value of v/G is smaller than the critical v/G, interstitial silicon is introduced more predominately than vacancies, and the vacancies disappear while the temperature decreases, leaving only interstitial silicon. survive. When the value of v/G is near the critical v/G and the point defect concentration is less than the critical supersaturation level for defect generation, a defect-free silicon crystal without COPs and dislocation clusters can be obtained.

FIG. 2 shows the relationship between the value of v/G and the defect distribution in the silicon crystal, and the horizontal axis shows the position in the diametrical direction of the silicon crystal. As shown in FIG. 2, silicon crystals are arranged in descending order of v/G value: a COP generation region 41, which is a crystal region where COPs are detected, and a ring-shaped OSF region when subjected to a specific oxidation heat treatment. OSF latent core region 42, oxygen precipitation promoting region (hereinafter also referred to as " _PV (1) region") 43, which is a crystalline region where oxygen precipitation occurs easily and COP is not detected, oxygen precipitates exist and COP is not detected The oxygen precipitation promoting region (hereinafter also referred to as " _PV (2) region") 44 is a crystalline region, and the oxygen precipitation suppressing region (hereinafter " _PI region") is a crystalline region in which oxygen precipitation is difficult to occur and COP is not detected. ) 45, and a dislocation cluster region 46 which is a crystal region where interstitial dislocation clusters are detected.

Among the silicon crystals showing the defect distribution as described above depending on the value of v/G, any of the crystal regions of the P _V (1) region 43, the P _V (2) region 44, and the P _I region 45, or A combination of these results in a silicon crystal free of COPs and dislocation clusters. Therefore, when producing a silicon wafer by the CZ method, a silicon wafer formed of any one of the crystal regions of the P _V (1) region 43, the P _V (2) region 44, and the P _I region 45, or a combination thereof. By performing wafer processing on a silicon crystal, a defect-free silicon wafer without COPs and dislocation clusters can be obtained.

Here, the term "silicon wafer containing no COPs" in the present invention means a silicon wafer in which no COPs are detected by observation and evaluation described below. That is, first, a silicon wafer cut and processed from a single crystal silicon ingot is subjected to SC-1 cleaning (that is, with a mixed solution of ammonia water, hydrogen peroxide solution, and ultrapure water in a ratio of 1:1:15). After cleaning, the surface of the silicon wafer was observed and evaluated using Surfscan SP-2 (manufactured by KLA-Tencor) as a surface defect inspection device. ). At this time, the observation mode is Oblique mode (oblique incidence mode), and the estimation of surface pits is performed based on the detected size ratio of the Wide and Narrow channels. The thus identified LPD is evaluated to determine whether it is a COP using an atomic force microscope (AFM). As a result of this observation and evaluation, a silicon wafer in which COPs are not observed is defined as a "silicon wafer containing no COPs."

In addition, in general device formation using epitaxial wafers, oxygen in the silicon wafer is precipitated to form BMDs (Bulk Micro Defects), and the formed BMDs are used to getter the heavy metals mixed into the wafer. May be used as a gettering site. However, the presence of BMD in an X-ray sensor causes leakage current and the like, degrading device performance. Therefore, the silicon wafer 11 needs to have a low oxygen concentration, and specifically, the oxygen concentration is 1×10 ¹⁷ atoms/cm ³ or less. In the present invention, the oxygen concentration is the oxygen concentration measured using a Fourier transform infrared spectrophotometer (FT-IR) in accordance with the infrared absorption method specified in ASTM F121-1979. .

A silicon wafer obtained from a silicon crystal grown by the above-mentioned FZ method has an oxygen concentration of 1×10 ¹⁷ atoms/cm ³ or less. On the other hand, in the CZ method, silicon raw materials are filled into a quartz crucible and heated and melted, so oxygen in the quartz crucible diffuses into the molten silicon, making it difficult to achieve a low oxygen concentration of 1×10 ¹⁷ atoms/cm ³ or less. However, by the magnetic-field-applied CZ (MCZ) method, etc., it is possible to grow silicon crystals with an oxygen concentration of 1×10 ¹⁷ atoms/cm ³ or less, and from the obtained silicon crystals. A silicon wafer having an oxygen concentration of 1×10 ¹⁷ atoms/cm ³ or less can be obtained.

Further, since a high voltage is applied to the silicon wafer 11 when detecting X-rays, the silicon wafer 11 needs to have high resistance. Therefore, in the present invention, the resistivity of the silicon wafer 11 is set to 1000 Ω·cm or more.

Currently, the thickness of the silicon wafer 11 is approximately 100 μm in order to form sufficient electron-hole pairs for receiving and detecting X-rays. Therefore, in the present invention, the thickness of the silicon wafer 11 is set to be 100 μm or more.

On the other hand, the silicon epitaxial layer 12 constitutes a region (device formation region) for forming a circuit for processing signals from the X-ray detection element. The silicon epitaxial layer 12 can be formed under general conditions using, for example, an epitaxial growth apparatus. For example, a source gas such as dichlorosilane or trichlorosilane is introduced into the chamber of an epitaxial growth apparatus using hydrogen as a carrier gas, and the CVD method is performed at a temperature of about 1000 to 1200°C, although the growth temperature varies depending on the source gas used. It can be epitaxially grown on the silicon wafer 11.

At this time, since the silicon wafer 11 is exposed to high temperatures, oxygen within the silicon wafer 11 diffuses into the silicon epitaxial layer 12. As a result, a transition region 12b in which oxygen is diffused is formed in the region of the silicon epitaxial layer 12 directly above the silicon wafer 11. Oxygen in this transition region 12b becomes a donor, causing problems such as fluctuations in resistivity. Therefore, the transition region 12b cannot be used to form a signal processing circuit.

Therefore, in the present invention, the thickness of the silicon epitaxial layer 12 is increased by the thickness of the transition region 12b, and the region 12a of the silicon epitaxial layer 12 excluding the transition region 12b is used as a device formation region for forming a signal processing circuit. do. Since the oxygen concentration in the silicon epitaxial layer 12 is usually 2×10 ¹⁶ atoms/cm ³ or less, the oxygen concentration in the device formation region 12a is 2×10 ¹⁶ atoms/cm ³ or less.

The thickness of the device formation region 12a of the silicon epitaxial layer 12 depends on the design of the signal processing circuit, but can be, for example, 1 to 15 μm. As described above, the silicon epitaxial layer 12 has the transition region 12b in which oxygen is diffused from the silicon wafer 11, so the thickness of the silicon epitaxial layer 12 is the thickness of the device formation region 12a plus the thickness of the transition region 12b. It is preferable that the thicknesses are the same.

Further, the resistivity of the device forming region 12a of the silicon epitaxial layer 12 is preferably 1 to 10 Ω·cm.

Note that, as shown in FIG. 1, it is preferable that the epitaxial wafer 1 further includes a gettering sink 13 on the back surface of the silicon wafer 11. As described above, since the silicon wafer 11 has a low oxygen concentration (1×10 ¹⁸ atoms/cm ³ or less), BMD cannot be precipitated and used as a gettering site. Therefore, by providing a gettering sink 13 on the back surface of the silicon wafer 11, heavy metals that have entered from the outside can be captured.

The gettering sink 13 may be formed by depositing polysilicon on the back surface of the silicon wafer 11 to form a poly back seal (PBS), by grinding the back surface of the silicon wafer 11 to form a strained region, or by forming a strained region by grinding the back surface of the silicon wafer 11. It can be formed by implanting ions such as carbon into the back surface of the substrate.

(X-ray sensor)
The X-ray sensor according to the present invention includes a plurality of X-ray detection elements that receive and detect X-rays formed on a silicon wafer of the epitaxial wafer for an X-ray sensor according to the present invention, and a plurality of X-ray detection elements. Each of the X-ray detection elements includes a signal processing circuit formed in a silicon epitaxial layer for processing signals from the X-ray detection element, and the pair of the X-ray detection element and the signal processing circuit are separated from each other.

As described above, the epitaxial wafer 1 for an X-ray sensor according to the present invention shown in FIG. does not have grown-in defects (COPs and dislocation clusters), has a low oxygen concentration (1×10 ¹⁸ atoms/cm ³ or less) and high resistance (1000 Ω cm or more), and can detect X-rays. It has a sufficient thickness (100 μm or more) for Furthermore, the silicon epitaxial layer 12 has a region with a low oxygen concentration (2×10 ¹⁶ atoms/cm ³ or less) that is thick enough to form a signal processing circuit that processes signals from the X-ray detection element. Therefore, by forming an X-ray detection element on the silicon wafer 11 of the epitaxial wafer 1 and forming a signal processing circuit for processing the signal from the X-ray detection element on the silicon epitaxial layer 12, heat during X-ray detection can be reduced. It is possible to construct an X-ray sensor that can suppress accumulation.

FIG. 3 shows an example of an X-ray sensor according to the invention. In the X-ray sensor 100 shown in FIG. 3, a plurality of X-ray detection elements 21 for receiving and detecting X-rays are formed in the silicon wafer 11 of the epitaxial wafer 1 shown in FIG. (Only one X-ray detection element is shown.) A signal processing circuit 22 is formed in the silicon epitaxial layer 12 to process a signal from each of the plurality of X-ray detection elements. A first wiring 23 and a second wiring 24 are connected to the X-ray detection element 21 and the signal processing circuit 22, respectively. Furthermore, the pair of X-ray detection element 21 and signal processing circuit 22 are isolated from each other by an STI (Shallow Trench Isolation) 25 and a guard ring 26 .

Examples of the present invention will be described below, but the present invention is not limited to the examples.

<Evaluation of thermal conductivity>
Regarding thermal conductivity, wafer samples were prepared by forming an oxide film with a thickness of 5 μm by thermal oxidation on an n-type 10 Ω cm CZ silicon wafer corresponding to the conventional example, and an n-type wafer sample with a resistivity of 1000 Ω cm corresponding to the invention example. A type FZ wafer sample was prepared. Thermal conductivity was evaluated by measuring the resistance value before applying heat to the surface of these samples and the resistance value after applying heat. As a result, the thermal resistivity of the FZ wafer sample was 291 W/mK, and the thermal resistivity of the CZ wafer sample with an oxide film was 120 W/mK, which was less than 1/2 of the FZ wafer sample. As described above, when an X-ray sensor is formed on an SOI wafer that includes an oxide film, it is expected that heat dissipation will be worse than when an X-ray sensor is formed on a wafer that does not include an oxide film.

(Invention example 1)
An n-type (dopant: phosphorus) single crystal silicon ingot was produced by the FZ method, and the obtained single crystal silicon ingot was subjected to wafer processing to form a silicon wafer (resistivity: 1000 Ω cm, thickness: 750 μm, Oxygen concentration: 6×10 ¹⁵ atoms/cm ³ ) was obtained. A p-type (dopant: boron) silicon epitaxial layer (resistivity: 1 Ω·cm, thickness: 7 μm) was formed on the obtained silicon wafer at 1150° C. by the CVD method. Then, a PBS film was formed on the back surface of the silicon wafer. In this way, an epitaxial wafer according to Invention Example 1 was obtained. Details of the obtained epitaxial wafer are shown in Table 1.

(Invention example 2)
In the same manner as Invention Example 1, an epitaxial wafer according to Invention Example 2 was obtained. However, the single crystal silicon ingot was produced by the MCZ method, and a silicon wafer having an oxygen concentration of 1×10 ¹⁷ atoms/cm ³ was obtained. Everything else is the same as Invention Example 1. Details of the obtained epitaxial wafer are shown in Table 1.

(Conventional example)
In the same manner as Invention Example 2, an epitaxial wafer according to Comparative Example 1 was obtained. However, the thickness of the silicon epitaxial layer was 5 μm. Everything else is the same as Invention Example 2. Details of the obtained epitaxial wafer are shown in Table 1.

(Comparative example 1)
In the same manner as Invention Example 2, an epitaxial wafer according to Comparative Example 1 was obtained. However, the single crystal silicon ingot was produced by the MCZ method, and a silicon wafer having an oxygen concentration of 4×10 ¹⁷ atoms/cm ³ was obtained. Everything else is the same as Invention Example 2. Details of the obtained epitaxial wafer are shown in Table 1.

(Comparative example 2)
In the same manner as Invention Example 2, an epitaxial wafer according to Comparative Example 2 was obtained. However, the single crystal silicon ingot was produced by the MCZ method, and a silicon wafer having an oxygen concentration of 7×10 ¹⁷ atoms/cm ³ was obtained. Everything else is the same as Invention Example 2. Details of the obtained epitaxial wafer are shown in Table 1.

(Comparative example 3)
In the same manner as Invention Example 1, an epitaxial wafer according to Comparative Example 3 was obtained. However, the resistivity of the silicon wafer was set to 10Ω·cm. Everything else is the same as Invention Example 1. Details of the obtained epitaxial wafer are shown in Table 1.

(Comparative example 4)
In the same manner as Invention Example 1, an epitaxial wafer according to Comparative Example 4 was obtained. However, the resistivity of the silicon wafer was set to 100Ω·cm. Everything else is the same as Invention Example 1. Details of the obtained epitaxial wafer are shown in Table 1.

(Invention example 3)
In the same manner as Invention Example 1, an epitaxial wafer according to Invention Example 3 was obtained. However, the resistivity of the silicon wafer was set to 10,000 Ω·cm. Everything else is the same as Invention Example 1. Details of the obtained epitaxial wafer are shown in Table 1.

<Characteristics evaluation of pn junction diode>
PN junction diodes shown in FIG. 4 were fabricated in the silicon epitaxial layers of the epitaxial wafers of Invention Examples 1 to 3, Conventional Examples, and Comparative Examples 1 to 4, and their characteristics were evaluated. Specifically, first, an n-type well region was formed in a p-type silicon epitaxial layer, and then a p-type region was formed within the n-type well region to form a pn junction region. Next, an interlayer insulating film and an Al wiring electrode were patterned on the silicon epitaxial layer to fabricate a pn junction diode capable of evaluating pn junction characteristics. The reverse current flowing through the manufactured pn junction diode was evaluated by IV measurement. At this time, the n-type well region and the back surface of the silicon wafer were fixed at 0V, a voltage from 0V to -10V was applied to the p-type region, and the current flowing through the pn junction region was measured. The results obtained are shown in Table 1.

As shown in Table 1, the IV measurement results were 1×10 ⁻⁴ A/cm ² for the conventional example, 1×10 −10 A/cm 2 for Invention Examples 1 to 3 and Comparative Examples 3 and 4, and 1×10 ⁻¹⁰ A/cm ² for the comparative example. In Examples 1 and 2, a current of 1×10 ⁻⁸ A/cm ² or more flowed. As a result of SIMS analysis, it was found that in the conventional example, oxygen diffused from the silicon wafer to the silicon epitaxial layer by 2 μm, and in Invention Examples 1 and 2 and Comparative Examples 1 and 2, oxygen diffused by 2.5 μm. In Invention Examples 1 and 2 and Comparative Examples 1 and 2, the silicon epitaxial layer was formed 2 μm thicker than in the conventional example, so it is thought that the increase in leakage current due to oxygen was suppressed.

<Performance evaluation of X-ray sensor>
In the epitaxial wafers according to Invention Examples 1 to 3, Conventional Examples, and Comparative Examples 1 to 4, X-ray sensors having the structure shown in FIG. 3 were fabricated in silicon wafers, and the light receiving characteristics of the X-ray sensors were evaluated. For the manufactured X-ray sensor, X-rays were irradiated onto the back surface of the silicon wafer, and the amount of received X-rays that passed through the silicon wafer was photoelectrically converted and evaluated as a current value. At that time, the second wiring 24 was fixed at 0V, and a voltage was applied to the first wiring 23. When X-rays are received, electron-hole pairs are generated in the X-ray detection element 21, and a current flows between the first wiring 23 and the second wiring 24. In this evaluation, if 1×10 ^-3 A/cm ² or more flows after X-ray irradiation, it is determined that X-rays have been received and is judged as ○, and if no X-rays flow, it is determined that X-rays were not received. It was judged as ×. The results obtained are shown in Table 1.

As shown in Table 1, in the conventional example and comparative examples 1 and 2, when the voltage is applied between the first wiring 23 and the second wiring 24 and the X-rays are not irradiated, the A current of 1×10 ⁻⁶ A/cm ² flowed between the wires where only 1×10 ⁻¹⁰ A/cm ² was supposed to flow, making it impossible to function as an X-ray sensor. It is thought that this is because interstitial oxygen contained inside the silicon wafer produced by the CZ method forms defects and becomes a source of leakage current.

In addition, for Comparative Examples 3 and 4, the depletion layer did not spread sufficiently because the resistivity of the region where the X-ray detection element was formed was low, and X-rays could not be detected sufficiently. A current of ^-3 A/cm2 or ^more did not flow. On the other hand, in Invention Examples 1 to 3, a current of 1×10 ⁻³ A/cm ² or more flowed after X-ray irradiation, and the irradiated X-rays could be detected.

According to the present invention, it is possible to suppress heat generated during X-ray detection from accumulating inside the sensor, and therefore it is useful in the semiconductor industry.

1 Epitaxial wafer 11 Silicon wafer 12 Silicon epitaxial layer 12a Device formation region 12b Transition region 13 Gettering sink 21 X-ray detection element 22 Processing circuit 23 First wiring 24 Second wiring 25 STI
26 Guard ring 41 COP generation region 42 OSF latent core region 43 Oxygen precipitation promotion region 44 Oxygen precipitation promotion region 45 Oxygen precipitation suppression region 46 Dislocation cluster region 100 X-ray sensor

Claims (4)

An epitaxial wafer for X-ray sensors,
A silicon wafer having a thickness of 100 μm or more, a resistivity of 1000 Ω·cm or more, and an oxygen concentration of 1×10 ¹⁷ atoms/cm ³ or less, and containing no COPs or dislocation clusters;
a silicon epitaxial layer provided on the surface of the silicon wafer and having a device formation region with an oxygen concentration of 2×10 ¹⁶ atoms/cm ³ or less;
An epitaxial wafer for an X-ray sensor, comprising: The silicon wafer has an X-ray detection element formation region in which an X-ray detection element for detecting X-rays is formed, and the device formation region in the silicon epitaxial layer has a circuit that processes a signal from the X-ray detection element. The epitaxial wafer for an X-ray sensor according to claim 1, having a signal processing circuit formation region formed therein. The epitaxial wafer for an X-ray sensor according to claim 1 or 2, further comprising a gettering sink provided on the back surface of the silicon wafer. A plurality of X-ray detection elements that receive and detect X-rays, formed on the silicon wafer of the epitaxial wafer for an X-ray sensor according to any one of claims 1 to 3;
a signal processing circuit for processing signals from the X-ray detection element, formed in the silicon epitaxial layer for each of the plurality of X-ray detection elements;
Equipped with
An X-ray sensor, wherein a pair of the X-ray detection element and the signal processing circuit are separated from each other.

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