JP4469454B2 - Manufacturing method of drift type silicon radiation detector having PN junction portion - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a silicon radiation detector, and more particularly to a method for manufacturing a drift-type silicon radiation detector having a PN junction portion.
[0002]
[Prior art]
As shown in FIG. 1, the conventional method for manufacturing a silicon radiation detector has the following processes.
(1) Cleaning of silicon wafer 1 (FIG. 2A)
(2) Impurity diffusion (FIG. 2B)
(3) Impurity drift (FIG. 2C)
(4) Polishing finish (polishing finish on the surface opposite to the impurity diffusion layer) (FIG. 2D)
(5) Metal deposition (forms a surface barrier) (FIG. 2E)
(6) Adhesion (mounting)
(7) Electrode deposition In the impurity drift in the above step (3), since the drift speed at the peripheral edge of the wafer is higher than that at the central portion of the wafer, the impurity 4 (FIG. 2C) is on the opposite side of the wafer at the peripheral edge. When the surface is reached, the impurities still do not reach the opposite surface of the wafer in the center.
[0003]
Since there are more impurities (phosphorus, etc.) and defects that hinder drift in the central part than in the outer peripheral part of the wafer, the drift speed is relatively high at the outer peripheral part of the wafer. The reason why there are many impurities and defects in the central part of the wafer is that when the crystal is grown, the liquid or solid is generally driven to the part where the impurities and defects are later solidified. It means that there are many impurities and defects in the central part that is thought to be solidified later.
[0004]
In the drift method, holes due to P-type impurities B in Si are compensated with electrons due to N-type impurities Li, thereby creating a neutral region. Therefore, the speed at which Li proceeds is related to the B concentration. The Si substrate is a P-type doped with B impurities, but the B region to be diffused later is a high-concentration layer that is about three orders of magnitude higher than the substrate. For this reason, when Li drifted in the B region diffused later arrives, it takes a considerable time for Li compensation in that portion, and it seems that it has stopped.
[0005]
For this reason, after the polishing finish in the above step (4), the opposite surface of the wafer is polished (FIG. 2D) until the impurity drift layer in the central portion appears, and the drifted impurity on the entire opposite surface. 4 (FIG. 2D) must appear.
[0006]
Such a conventional method has the following problems.
(A) Polishing is required after the drift of impurities is completed.
(A) After the impurity drift, a step (5) of depositing a metal for forming a surface barrier is required. In the process of depositing the metal, the deposited metal is processed at a high temperature (500 ° C. or higher). On the other hand, the already formed impurity drift layer is formed by drifting the impurity diffusion layer at a temperature of about 150 ° C., and may be destroyed by such a high temperature deposition process. .
(C) In the drift type silicon detector manufactured by such a conventional method, since a surface barrier type diode is formed, it is easily affected by the surrounding environment (pressure change, humidity, dust, etc.), and has characteristics. It is easy to cause deterioration. In the surface barrier type, since the diode characteristics are determined between the electrode metal and Si, it is weak to the surrounding environment (pressure, humidity, dust, etc.). For example, when the electrode metal is scratched, the surface barrier type is completely deteriorated.
(D) Impurity drift speed becomes non-uniform due to non-uniformity of impurity distribution in the silicon base material forming the wafer, and a large diameter (3 inches or more) and thick (5 mm or more) detector is manufactured. It is difficult. The reason why a thick detector is required is as follows. That is, the electric capacity that causes noise can be reduced depending on the thickness of the detector, so that the performance as a detector is improved. The reason is that there is a relationship given by the following equation between the capacitance C and the thickness d of the detector.
[0007]
C = ε _s ε ₀ S / d
Here, ε _s represents the relative dielectric constant of silicon, ε ₀ represents the dielectric constant in vacuum, and S represents the area of the detector. In particular, in a large area detector, this thickness is an important factor.
[0008]
[Problems to be solved by the invention]
In order to solve the problems of the silicon radiation detector manufactured by the above-described conventional manufacturing method and the difficulty of the manufacturing method, the present invention forms a PN junction diode and has a thickness that is strong even in a poor environment. An object is to produce a silicon radiation detector.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided a method of manufacturing a drift-type silicon radiation detector having a PN junction portion, a cleaning process for cleaning a semiconductor substrate of a first conductivity type, Heating in an atmosphere to form an oxide film on a first main surface of the semiconductor substrate and a second main surface opposite to the first main surface; an oxidation process; and The first conductive process is performed on a portion of the first main surface of the semiconductor substrate exposed by removing the diffusion portion of the oxide film and a first photo process step of removing the diffusion portion. Forming a first diffusion layer comprising a first impurity of the mold and comprising a circular central portion and an annular portion formed at the same center as the circular central portion; Forming a second oxide film covering the first diffusion layer; And oxidation process, the said said exposed portion by the diffusing part is removing the oxide film of the second main surface of the semiconductor substrate, the first of said first conductivity type different from the second conductivity type Forming a second diffusion layer made of two impurities, a second diffusion process, and removing a portion of the second oxide film corresponding to the first diffusion layer; A step of forming a drift electrode covering the first diffusion layer and the second oxide film; and drifting the second diffusion layer toward the first main surface to form the second diffusion Forming a drift region of the second conductivity type extending from a layer to the first diffusion layer, wherein a PN junction is formed at a boundary between the drift region and the first diffusion layer. And the guard ring structure is formed. Method for producing a drift-type silicon radiation detector and having a preparative process is provided.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
As illustrated in FIG. 3, the method for manufacturing the silicon radiation detector of the present application includes the following steps.
(1) Cleaning of silicon wafer (2) Oxidation (3) Photo process (4) Diffusion of first impurity (FIG. 4B)
(5) Second impurity diffusion (FIG. 4C)
(6) Second impurity drift (FIG. 4D)
(7) Polishing (8) Surface treatment (9) Adhesion (mounting)
(10) Electrode deposition The production method of the present invention will be described below with specific examples.
[0011]
The performance specifications of the specific example of the material silicon wafer used in the manufacturing method of the present invention are as follows.
Crystal production method FZ crystal orientation <111> or <100>
Dope agent B (boron)
Resistivity 100Ω · cm (from 3000Ω · cm)
Carrier lifetime 1 ms or more Dislocation density 1000 / cm ² or less P (adjacent) concentration 5 × 10 ¹² or less O (oxygen) concentration 1 × 10 ¹⁶ or less Surface finish Lapping or single-sided mirror finish In this example, the first impurity Boron (B) was used as the second impurity, and lithium (Li) was used as the second impurity. As the first impurities, boron (B), aluminum (Al), indium (In), zinc (Zn), gallium (Ga), and thallium (Ti), which are P-type impurities (acceptors), As the impurities, lithium (Li), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi), which are N-type impurities (donors), may be used.
(1) Cleaning process First, the wafer is subjected to organic solvent cleaning in which the wafer is subjected to ultrasonic cleaning or boiling cleaning with acetone and methanol. Next, the wafer is cleaned by boiling with aqua regia. Next, the wafer is washed with running water with pure water or deionized water (15 MΩ · cm or more). Finally, the crushed layer on the surface of the wafer is dissolved and removed with an etching solution (for example, 1HF: 2HNO ₃ : 1CH ₃ COOH).
(2) Oxidation process The wafer is heated in pure oxygen at 850 ° C. (from 600 ° C. to 900 ° C.) for 7 hours to form a SiO ₂ film having a film thickness of about 5000 Å.
(3) The SiO ₂ film formed in the diffusion portion used in the diffusion process after the photo process (PEP) process is removed. Since the entire wafer is heated in the diffusion process, it is necessary to cover an area where the diffusion is not desired with an oxide film.
(4) B (boron) diffusion process PBF (Poly Boron Film) is applied to the diffusion portion and heated at 850 ° C. (from 600 ° C. to 900 ° C.) for 24 hours, and the diffusion depth is 0.4 μm. A B diffusion layer 2 (FIG. 4B) of 0.2 μm or more is formed.
(5) Li (Lithium) diffusion process In a vacuum on the surface of the wafer opposite to the surface on which the B diffusion layer is formed (hereinafter referred to as “the main surface of the wafer”) (hereinafter referred to as “the opposite surface of the wafer”). (1 × 10 ⁻⁴ Torr or less) at 450 ° C. (from 400 ° C. to 500 ° C.) for 6 minutes (from 3 minutes to 15 minutes). Lithium diffusion layer 3 (FIG. 4C) of up to 7 mm is formed.
(6) Li (lithium) drift process First, the Li diffusion layer 3 (FIG. 4D) is formed so that the reverse characteristics of the PN junction diode formed in the wafer are improved, that is, the leakage current is reduced. The formed surface (Li side end face) is mesa-etched or grooved, and then at a voltage of 1000 V / cm (from 500 V / cm to 2000 V / cm) at a temperature of 130 ± 20 ° C. and a time determined by the following formula Drift processing is performed over t (FIG. 4D).
[0012]
W = (2 × μVt) ^1/2 (Formula 1)
Here, W represents the width of the drift region [cm], μ represents the mobility of lithium [cm ² / V · sec], V represents the reverse bias voltage [V], and t represents the drift time [sec], respectively. Yes.
[0013]
In this way, when the drift process over the drift time t obtained from Equation 1 is completed, the Li drifted portion (Li drift layer) is already formed in the entire cross section along the radial direction of the wafer. A PN junction is formed between the Li drift layer 4 (FIG. 4D) and the B diffusion layer 2 (FIG. 4D).
(7) Polishing process When a transmission type detector is manufactured, a polishing process is performed after the Li drift process, and the Li diffusion layer is completely removed. The transmission type is called a fully depleted layer detector, and is used to detect the energy loss of radiation and the amount of charge produced at that time. Those not transmissive are used as partially depleted layer detectors.
(8) Surface treatment process First, pure water cleaning is performed in which the wafer is washed with pure water or deionized water (15 MΩ · cm). Next, organic solvent cleaning is performed by ultrasonic cleaning or boiling cleaning of the wafer with acetone and methanol. Next, aqua regia cleaning is performed in which the wafer is boiled and washed with aqua regia. Next, a second pure water cleaning is performed in which the wafer is washed with running pure water or deionized water (15 MΩ · cm). Finally, the polishing surface and side surfaces (all surfaces other than the surface on which the B diffusion layer is formed) are etched using an etching solution (for example, 1HF: 3HNO ₃ ).
(9) Bonding (Mounting) Process The wafer 1 (FIGS. 5A and 5B) is bonded to an insulator 6 (FIGS. 5A and 5B) such as glass epoxy, acrylic, and ceramic with an insulating adhesive.
(10) Deposition process A metal electrode is formed by vapor-depositing a metal such as Au, Pt, Pd, Ni, and Al on both the main surface and the opposite surface of the wafer by vacuum deposition.
[0014]
The specifications of the silicon radiation detector manufactured by the manufacturing method of the present invention and the results of characteristic evaluation are shown below.
[0015]
Specification shape Diameter 146mm Thickness 10mm
Effective diameter 114mm or more Effective thickness 6000μm ± 200μm
Thickness uniformity within sensitive area Within ± 10μm (more than 95% of the total area)
Total depletion voltage 600V
Withstand voltage 800V
Leakage current 150μA or less (600V, 25 ℃)
As a result of the evaluation of the electrode side surface extraction characteristics, the voltage / current characteristics of the silicon radiation detector are as shown in FIG. The current at the minimum voltage of 50 V in the characterization test was approximately 21 μA, and the current at the maximum voltage of 350 V was approximately 38 μA.
[0016]
The voltage / capacitance characteristics of the silicon radiation detector are as shown in FIG. The capacity is almost constant regardless of the bias voltage. This indicates that since the resistivity of the drift layer is very high, the depletion layer is not greatly expanded by the bias voltage.
[0017]
The high resistivity of the drift layer means that the carrier concentration is low, which means that the depletion layer is further expanded at a low voltage. Since the thickness of this depletion layer becomes the effective thickness of the detector (it will be detected as a signal when radiation enters this portion), a thicker detector can be easily formed as the carrier concentration is lower. . The boron layer is about 0.5 μm, the lithium drift layer is about several mm, and the boron layer is a radiation entrance window that is a dead layer. Therefore, it is preferable that it is as thin as possible, and the lithium drift layer is as thick as possible because it is a sensitive part. Is preferred. Further, since the breakdown occurs when the depletion layer expands on the boron side, the carrier concentration is increased so that the depletion layer does not expand into the boron layer.
[0018]
FIG. 8 shows a graph of a measurement spectrum that represents the measurement result performed to obtain the α-ray resolution of the silicon radiation detector. The horizontal axis of the graph represents a channel, this channel corresponds to the energy of α-rays, the vertical axis represents the number of counts, and this number of counts was detected by the detector for each channel (energy). Represents the count number.
[0019]
The resolution is given by a value obtained by dividing the channel width at which the count number is the maximum and the channel width at which the count number is ½ of the maximum value. The smaller the resolution value, the better the detector.
[0020]
From the measurement results of FIG. 8, the count number is maximum at 378.7 channels (5.5 MeV), and the channel width at which the count number is ½ of the maximum value is 7.43 channels (108 keV). Measured. Therefore, the resolution of this detector was 108 keV / 5.5 MeV = 0.0196 = 1.96%.
[0021]
One of the causes for increasing the resolution value is fluctuation of α-ray particles in the detector. As a major factor of fluctuation inside the detector, there is particle scattering due to the presence of a surface insensitive layer on the surface of the detector. The surface insensitive layer is formed when the drift layer of the second impurity does not reach the diffusion layer of the first impurity. Since 5.5 MeV α-rays are transmitted through silicon only up to about 30 μm, when such a dead layer is formed, the resolution value becomes large. In the detector manufactured by the present invention, the resolution value is 1.96%, which is a sufficiently good value, so that it can be seen that the above-described surface insensitive layer is not formed.
[0022]
Of the measurement spectrum of FIG. 8, the pulsar represents the noise of the measurement system, and represents the spectrum when the pseudo signal is directly input from the detector to the preamplifier that amplifies the output signal.
[0023]
FIG. 9 shows the α-ray saturation characteristics of the silicon radiation detector. In this characteristic evaluation test, the range of α rays in the silicon substrate is about 30 μm, and therefore, in order to investigate how much insensitive part (corresponding to the part where the drift layer has not reached) exists in the incident part. It was conducted.
[0024]
Next, a second embodiment of the present invention will be described with reference to FIG. 10, FIG. 11, and FIG.
[0025]
FIG. 10 is a flowchart showing the process of the manufacturing method according to the second embodiment of the present invention. The cleaning process and oxidation process of the silicon wafer are the same as the embodiment shown in FIG. In the photo process 1, the surface of the silicon substrate 1 on which the first impurity diffusion layer is formed, that is, the portion corresponding to the B diffusion layer to be formed in the SiO ₂ film on the main surface of the wafer is removed. Next, the diffusion process of the first impurity is performed to form the B diffusion layer of the circular central portion 2a shown in FIGS. 11B and 12 and the diffusion layer of the annular portion 2b concentric with the central portion. The
[0026]
Next, in the process of forming the SiO ₂ film, the SiO ₂ film 7 is formed over the entire main surface of the wafer. Subsequently, in the second impurity diffusion process, the Li diffusion layer 3 is formed on the opposite surface of the wafer (FIG. 11C).
[0027]
In photo process 2, the portion covering the B diffusion layer 2a and the main surface of 2b is not formed of the SiO ₂ film 7 is left, another portion of the SiO ₂ film 7 is removed (FIG. 11D).
[0028]
In the next drift process of the second impurity, a drift process is performed, and the Li drift layer shown in FIG. 11E is formed. In this second impurity drift process, the gold electrode 8 shown in FIG. 11E is used as a drift electrode. The gold electrode 8 is formed by vacuum deposition after the photo process 2 is finished and before the second impurity drift process is started.
[0029]
FIG. 12 is a plan view (FIG. 12A) and a side sectional view (FIG. 12B) of a detector manufactured according to the second embodiment of the present invention. In FIG. 12A, the gold electrode 8 is omitted for the sake of clarity, but in reality, a circular gold electrode 8 is formed so as to cover the central portion 2a and the annular portion 2b. The annular portion 2b functions as a guard ring and has a function of preventing leakage current when the detector is used.
[0030]
The polishing process, surface treatment process, and adhesion (mounting) process executed thereafter are the same as those in the embodiment shown in FIG. In the electrode deposition process, an electrode is formed only on the opposite surface opposite to the main surface on which the gold electrode 8 is formed.
[0031]
Next, a third embodiment of the present invention will be described with reference to FIGS. 13, 14, and 15. FIG.
[0032]
FIG. 13 is a flowchart showing the process of the manufacturing method according to the third embodiment of the present invention. The cleaning process and oxidation process of the silicon wafer are the same as the embodiment shown in FIG. In the photo process 1, the surface of the silicon substrate 1 on which the first impurity diffusion layer is formed, that is, the portion corresponding to the B diffusion layer to be formed in the SiO ₂ film on the main surface of the wafer is removed. Next, the diffusion process of the first impurity is performed, and the stripe-shaped B diffusion layer 2c shown in FIGS. 14B and 15 is formed.
[0033]
Next, in the process of forming the SiO ₂ film, the SiO ₂ film 7 is formed over the entire main surface of the wafer. Subsequently, in the second impurity diffusion process, the Li diffusion layer 3 is formed on the opposite surface of the wafer (FIG. 14C).
[0034]
In photo process 2, the portion covering the principal surface of the stripe-shaped B diffusion layer 2c is not formed of the SiO ₂ film 7 is left, another portion of the SiO ₂ film 7 is removed (FIG. 14D).
[0035]
In the next drift process of the second impurity, a drift process is performed, and the Li drift layer shown in FIG. 14E is formed. In this second impurity drift process, the gold electrode 8 shown in FIG. 14E is used as a drift electrode. The gold electrode 8 is formed after the photo process 2 is finished and before the second impurity drift process is started.
[0036]
FIG. 15 is a plan view (FIG. 15A) and a side sectional view (FIG. 15B) of a detector manufactured according to the third embodiment of the present invention. In FIG. 15A, the gold electrode 8 is omitted for the sake of clarity, but in reality, a gold electrode having a shape corresponding to the stripe-shaped B diffusion layer 2c is formed.
[0037]
The polishing process, surface treatment process, and bonding (mounting) process performed thereafter are the same as those in the embodiment shown in FIG. In the electrode deposition process, when manufacturing a one-dimensional position detector, the gold electrode formed on the main surface is processed into a shape corresponding to the stripe-shaped B diffusion layer, and the opposite surface is entirely covered. Thus, an electrode is formed. When a two-dimensional position detector is manufactured, a stripe-shaped electrode orthogonal to the stripe-shaped electrode on the main surface is formed on the opposite surface.
[0038]
The reason why the SiO ₂ film formation process is executed by the methods of the second and third embodiments of the present invention will be described.
[0039]
When the stripe-shaped B diffusion layer is formed as in the third embodiment, the PN junction is formed when the tip of the drift region reaches the gold electrode in the silicon substrate portion between the stripe-shaped B diffusion layers. Disappears at the reached position, and the drift stops before the entire silicon base portion between the B diffusion layers is made neutral by the drift layer. On the other hand, in the position detector, the stripe-shaped diffusion layers must be regions having a high resistance value. When the region between the B diffusion layers is a region that is not neutralized by the drift layer and remains the same conductivity type as the diffusion layer, each stripe-shaped diffusion layer is not electrically insulated, This is because the function as a position detector cannot be obtained. Thus, in order to prevent the drift from stopping before the neutralization by the drift layer is completed, before the drift process, the SiO covering the main surface of the silicon substrate between the stripe-shaped diffusion layers is provided. _Two films were formed to keep the drift region from contacting the gold electrode so that drift continued.
[0040]
Furthermore, when used as a radiation detector, including when used as a position detector, the shape of the diffusion layer on the main surface is set to the central portion and this to prevent leakage current flowing along the side surface of the silicon substrate. It is formed as an annular portion surrounding the central portion, and this annular portion is used as a guard ring for preventing leakage current.
[0041]
Even in the case of forming the guard ring in this manner, as in the case of the position detector described above, the region between the central portion and the annular portion is completely neutralized, and the region has a high resistance value. is required.
[0042]
【The invention's effect】
According to the present invention, a PN junction can be formed without the need for polishing after the impurity drift, which is required in the conventional method, is completed. This PN junction is formed inside the Si substrate. Therefore, it is possible to manufacture a detector that does not easily deteriorate characteristics that are not easily affected by the surrounding environment (pressure change, humidity, dust, etc.). Furthermore, according to the present invention, a detector having a large diameter (3 inches or more in diameter) and a thick (5 mm or more) can be manufactured, and a detector having a small electric capacity that causes noise is provided.
[0043]
Furthermore, according to the present invention, the silicon substrate portion between the diffusion layers is completely neutralized by the drift layer so as to electrically insulate each striped diffusion layer of the manufactured position detector. Can do.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a process of a conventional method for manufacturing a silicon radiation detector.
FIGS. 2A and 2B are schematic views illustrating cross sections in each process of a silicon radiation detector made of A to E and manufactured by a conventional method of manufacturing a silicon radiation detector. FIGS.
FIG. 3 is a flowchart showing a process of a method for manufacturing a drift type silicon radiation detector according to the present invention.
FIG. 4 is a schematic diagram illustrating a cross section in each process of the silicon radiation detector, which is composed of A to D and manufactured by the method of manufacturing a drift type silicon radiation detector of the present invention.
5 is a plan view of a silicon radiation detector manufactured by the method of the present invention, and A is a sectional side view of the silicon radiation detector manufactured by the method of the present invention. FIG.
FIG. 6 is a graph of voltage-current characteristics of a silicon radiation detector manufactured by the method of the present invention.
FIG. 7 is a graph of voltage capacitance characteristics of a silicon radiation detector manufactured by the method of the present invention.
FIG. 8 is a graph of a measured spectrum for obtaining an α-ray resolution of a silicon radiation detector manufactured by the method of the present invention.
FIG. 9 is a graph of α-ray saturation characteristics of a silicon radiation detector manufactured by the method of the present invention.
FIG. 10 is a flowchart showing a process of a manufacturing method of a drift type silicon radiation detector according to the second embodiment of the present invention.
FIGS. 11A to 11E are schematic views illustrating cross sections in respective processes of a silicon radiation detector made of A to E and manufactured by the method of manufacturing a drift type silicon radiation detector according to the second embodiment of the present invention. FIGS.
12 is a plan view of a silicon radiation detector manufactured by the method according to the second embodiment of the present invention, and A is manufactured by the method according to the second embodiment of the present invention. The side sectional view of a silicon radiation detector.
FIG. 13 is a flowchart showing a process of a drift type silicon radiation detector manufacturing method according to a third embodiment of the present invention.
FIGS. 14A and 14B are schematic views illustrating cross sections in respective steps of a silicon radiation detector made of A to E and manufactured by the drift type silicon radiation detector manufacturing method according to the third embodiment of the present invention; FIGS.
FIG. 15 is composed of A and B, A is a plan view of a silicon radiation detector manufactured by the method of the third embodiment of the present invention, and B is manufactured by the method of the third embodiment of the present invention. The side sectional view of a silicon radiation detector.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Silicon base material 2 Boron (B) diffusion layer 2a Central circular part 2b of B diffusion layer Ring-shaped part 2c of B diffusion layer Striped B diffusion layer 3 Lithium (Li) diffusion layer 4 Lithium (Li) drift layer 5 Metal layer 6 Insulator 7 SiO ₂ film 8 Gold electrode

Claims (5)

A method of manufacturing a drift-type silicon radiation detector having a PN junction portion,
A cleaning process for cleaning the semiconductor substrate of the first conductivity type;
An oxidation process in which the semiconductor substrate is heated in an oxygen atmosphere to form an oxide film on a first main surface of the semiconductor substrate and a second main surface opposite to the first main surface; ,
A first photo process for removing a diffusion portion of the oxide film;
A portion of the first main surface of the semiconductor substrate exposed by removing the diffusion portion of the oxide film is made of the first impurity of the first conductivity type and has a circular central portion. Forming a first diffusion layer comprising a circular central portion and an annular portion formed in the same center; and a first diffusion process;
A second oxidation process for forming a second oxide film covering the first diffusion layer;
A portion of the second main surface of the semiconductor substrate exposed by removing the diffusion portion of the oxide film is exposed to a second impurity of a second conductivity type different from the first conductivity type. Forming a second diffusion layer comprising: a second diffusion process;
Removing a portion of the second oxide film corresponding to the first diffusion layer; a second photo process step;
Forming a drift electrode covering the first diffusion layer and the second oxide film;
Drift that drifts the second diffusion layer toward the first main surface to form the drift region of the second conductivity type extending from the second diffusion layer to the first diffusion layer. A drift type comprising: a drift process in which a PN junction is formed at a boundary between the drift region and the first diffusion layer and a guard ring structure is formed. Manufacturing method of silicon radiation detector. A method of manufacturing a drift-type silicon radiation detector having a PN junction portion,
A cleaning process for cleaning the semiconductor substrate of the first conductivity type;
An oxidation process in which the semiconductor substrate is heated in an oxygen atmosphere to form an oxide film on a first main surface of the semiconductor substrate and a second main surface opposite to the first main surface; ,
A first photo process for removing a diffusion portion of the oxide film;
A portion of the first main surface of the semiconductor substrate exposed by removing the diffusion portion of the oxide film is made of the first impurity of the first conductivity type and has a plurality of stripe-like shapes. Forming a first diffusion layer comprising a portion, a first diffusion process;
A second oxidation process for forming a second oxide film covering the first diffusion layer;
A portion of the second main surface of the semiconductor substrate exposed by removing the diffusion portion of the oxide film is exposed to a second impurity of a second conductivity type different from the first conductivity type. Forming a second diffusion layer comprising: a second diffusion process;
Removing a portion of the second oxide film corresponding to the first diffusion layer; a second photo process step;
Forming a drift electrode covering the first diffusion layer and the second oxide film;
Drift that drifts the second diffusion layer toward the first main surface to form the drift region of the second conductivity type extending from the second diffusion layer to the first diffusion layer. A drift type silicon radiation detector comprising: a drift process in which a striped PN junction is formed at a boundary between the drift region and the first diffusion layer. Method. The first impurity is any of boron (B), aluminum (Al), indium (In), zinc (Zn), gallium (Ga), and thallium (Ti),
3. The method according to claim 1, wherein the second impurity includes lithium (Li), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi). The first impurity comprises boron (B);
The method according to claim 1, wherein the second impurity is lithium (Li). The drift process is performed for a time t determined by the following equation:
W = (2 × μVt) ^1/2
Here, W represents the width [cm] of the drift region, μ represents the mobility of the second impurity [cm ² ], V represents the reverse bias voltage [V], and t represents the drift time [second]. The method according to any one of claims 1 to 4, characterized in that:

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