CN112951932A - Silicon single crystal substrate and silicon epitaxial wafer for solid-state imaging device, and solid-state imaging device - Google Patents
Silicon single crystal substrate and silicon epitaxial wafer for solid-state imaging device, and solid-state imaging device Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 202
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 202
- 239000010703 silicon Substances 0.000 title claims abstract description 202
- 239000013078 crystal Substances 0.000 title claims abstract description 183
- 239000000758 substrate Substances 0.000 title claims abstract description 182
- 238000003384 imaging method Methods 0.000 title claims abstract description 84
- 239000002019 doping agent Substances 0.000 claims abstract description 53
- 238000000034 method Methods 0.000 claims abstract description 29
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 57
- 239000001301 oxygen Substances 0.000 claims description 57
- 229910052760 oxygen Inorganic materials 0.000 claims description 57
- 230000003287 optical effect Effects 0.000 claims description 3
- 239000010410 layer Substances 0.000 description 57
- 206010047571 Visual impairment Diseases 0.000 description 53
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
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- H—ELECTRICITY
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
- H01L31/0264—Inorganic materials
- H01L31/028—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic System
- H01L31/0288—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic System characterised by the doping material
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/02—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt
- C30B15/04—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt adding doping materials, e.g. for n-p-junction
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/06—Silicon
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- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
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- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
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- H01L21/02365—Forming inorganic semiconducting materials on a substrate
- H01L21/02518—Deposited layers
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- H01L21/02365—Forming inorganic semiconducting materials on a substrate
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- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
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- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
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Abstract
The technical problem is as follows: the invention provides a silicon single crystal substrate and a silicon epitaxial wafer for a solid-state imaging device, which can inhibit the residual image characteristics of the solid-state imaging device. The solution is as follows: silicon single crystal substrate for solid-state camera componentA silicon single crystal substrate for a solid-state imaging element obtained by slicing a silicon single crystal produced by the CZ method, wherein the silicon single crystal substrate is a p-type silicon single crystal substrate in which Ga is a main dopant and B concentration is 5X 1014atoms/cm3The following.
Description
Technical Field
The present invention relates to a silicon single crystal substrate and a silicon epitaxial wafer for a solid-state imaging device, and a solid-state imaging device.
Background
The solid-state imaging device has been applied to mobile devices such as smart phones. The solid-state imaging device captures carriers generated by light in a depletion region (photodiode) of the PN junction portion, and converts optical information into electronic information to obtain an image (photoelectric conversion). In recent years, with the increase in the number of pixels, a plurality of images can be obtained in a short time by providing a cache memory near a photodiode, and photographs at every moment, which have been difficult to capture in the past, can be taken in addition to high image quality. This is because data can be read from the photodiode in a short time.
The current problem is the afterimage characteristic. This is a phenomenon in which a carrier generated by the photoelectric effect is captured and released after a certain period of time, and thus an image is seen as being left due to the influence of the carrier. When a plurality of data are acquired with high functionality and in a short time, if the afterimage exists, it means that the influence of the previous imaging data remains. The cause of the afterimage characteristics is considered to be a complex of boron and oxygen in the substrate (see non-patent documents 1 and 2 and patent documents 1 and 2).
In addition, in recent years, since expectations for autonomous driving have been increased, LiDAR (laser radar) has attracted attention as a sensor (eye). This technique is a technique of measuring the surrounding state (distance) by irradiating infrared rays as a light source and capturing reflected light by a sensor, and has been used in the field of airplane, mountain surveying, and the like. By combining with the millimeter wave, high-precision measurement required for automatic operation can be performed. In the LiDAR system, portions of the sensor use a solid-state imaging assembly. Among them, a method of increasing the sensitivity by multiplying the amount of carriers generated by avalanche breakdown (avalanche breakdown) of a diode when photons are incident on one photodiode has been discussed as a contrived concept of increasing the sensitivity. In this field, if the previous afterimage characteristics are generated, there is a possibility that the accuracy is degraded (although light is not originally present, light is perceived.
In addition to the automatic operation, the solid-state imaging device is expected to be used in many fields such as a vision sensor provided in an industrial robot and medical use for surgical operations.
Since a solid-state imaging device including these photodiodes is manufactured using a silicon substrate, it is important to develop a substrate capable of suppressing an afterimage characteristic.
Documents of the prior art
Patent document
[ patent document 1 ] Japanese patent laid-open publication No. 2019-9212
[ patent document 2 ] Japanese patent laid-open publication No. 2019-79834
[ patent document 3 ] Japanese patent No. 3679366
Non-patent document
[ Nonpatent document 1 ] No. 77 applied Physics Association autumn academic seminar, lecture corpus 14P-P6-10 Jintian wing, Dagu chapter "elucidation 1 of afterimage mechanism of CMOS image sensor"
[ Nonpatent document 2 ] 77 th Utility Physics Association autumn academic seminar, lecture corpus 14P-P6-10 Jintian wing, Dagu chapter, clarification 2 of afterimage mechanism of CMOS image sensor "
Disclosure of Invention
Technical problem to be solved
The present invention has been made in view of the above problems, and an object of the present invention is to provide a silicon single crystal substrate for a solid-state imaging device and a silicon epitaxial wafer, which can suppress an afterimage characteristic of the solid-state imaging device.
(II) technical scheme
In order to achieve the above object, the present invention provides a silicon single crystal substrate for a solid-state imaging device, which is obtained by slicing a silicon single crystal produced by the CZ method, wherein the silicon single crystal substrate is a p-type silicon single crystal substrate in which Ga is a main dopant and B concentration is 5 × 1014atoms/cm3The following.
Thus, the silicon single crystal is obtained by slicing a silicon single crystal produced by the CZ method (Czochralski method)The obtained p-type silicon single crystal substrate, which has a main dopant of Ga (gallium) instead of B (boron) that is generally used and has a B concentration of 5X 10 in the substrate, can be reduced in B concentration that is a cause of afterimage characteristics, and thus can suppress afterimage characteristics regardless of the interstitial oxygen concentration14atoms/cm3The following.
In addition, since the substrate is a CZ substrate, the substrate can be superior to an FZ (float zone) substrate in terms of substrate strength, gettering capability, substrate diameter size, and the like.
The "main dopant" is a dopant having a maximum concentration that determines the conductivity type of the silicon single crystal substrate.
Preferably, the interstitial oxygen concentration in the p-type silicon single crystal substrate is 1ppma or more and 15ppma or less.
If the concentration is 15ppma or less, the probability of generating a phenomenon (referred to as white spot (12461; \ 12474), in which oxygen becomes a generation center in a depletion layer and electron-hole pairs are generated to cause generation of charges even if light is not incident, or dark current is reduced. On the other hand, if the amount is 1ppma or more, the problems of decrease in substrate strength and insufficient gettering capability for heavy metal contamination can be more reliably prevented.
In addition, the above values of the interstitial oxygen concentration are based on the jeida (jeita) specification. JEIDA is an abbreviation of japan electronics industry society of corporation, and JEIDA shows calculation of the interstitial oxygen concentration using a determined conversion factor. Currently, JEIDA has been changed to JEITA (society of community electronic information technology industries).
Further, the present invention provides a solid-state imaging device comprising a photodiode section, a memory section, and a computing section, wherein at least the photodiode section is formed on the silicon single crystal substrate for the solid-state imaging device according to the present invention.
The solid-state imaging element includes at least a photodiode section, a memory section, and a computing section, but since the photodiode section has an afterimage characteristic, Ga is used as a main dopant and B concentration is 5X 1014atoms/cm3The following p-type silicon single crystal substrate is formed withThe substrate of the photodiode section can produce a solid-state imaging element with suppressed afterimage characteristics.
In addition, the invention provides a silicon epitaxial wafer for a solid-state imaging device, which is provided with a silicon epitaxial layer on the surface of a silicon single crystal substrate and is characterized in that the silicon epitaxial layer is a p-type epitaxial layer with Ga as a main dopant and the concentration of B is 5 multiplied by 1014atoms/cm3The following.
When a solid-state imaging device is manufactured using a silicon epitaxial wafer, since oxygen is hardly contained in a silicon epitaxial layer (also simply referred to as an epitaxial layer) in which a photodiode is formed, even if a main dopant of the epitaxial layer is B as in the conventional case, a complex of B and oxygen, which is a cause of image sticking characteristics, should not be formed. However, in the conventional product, oxygen in the silicon single crystal substrate may diffuse into the epitaxial layer due to the accumulation of the epitaxial layer or the heat treatment during the device fabrication process, thereby causing the generation of the image sticking characteristic. However, in the present invention, since the main dopant in the epitaxial layer is Ga and the concentration of B is 5X 1014atoms/cm3Accordingly, the afterimage characteristics can be suppressed regardless of how oxygen from the substrate diffuses. In addition, even if B is contained in the silicon single crystal substrate and diffuses into the epitaxial layer, the residual image characteristics can be still suppressed because the initial B concentration in the epitaxial layer is extremely low as described above.
Further, the silicon single crystal substrate is a p-type silicon single crystal substrate in which a main dopant is Ga, and the concentration of B is 5X 1014atoms/cm3The following.
In the case where B and oxygen are contained in the silicon single crystal substrate on which the epitaxial layer is formed, depending on their concentrations and the heat treatment to which the silicon single crystal substrate is subjected, in the conventional product, sometimes two elements diffuse into the epitaxial layer to cause the generation of the afterimage characteristic. Further, Ga is used as a main dopant in the silicon single crystal substrate, and B concentration is set to 5X 1014atoms/cm3The afterimage characteristics can be more reliably suppressed as follows.
The silicon single crystal substrate has a main dopant of B and a B concentration of 1X 1018atoms/cm3The aboveP of (a)+A silicon single crystal substrate.
If it is such a p+The silicon single crystal substrate of the type can further improve the "gettering capability of metal impurities and the like that may be generated by the deposition of an epitaxial layer or the heat treatment in the device fabrication process". In this case, although there may be B from p+The type silicon single crystal substrate diffuses into the epitaxial layer, but since oxygen is hardly contained in the epitaxial layer as described above, it is possible to suppress formation of a complex of B and oxygen, which is a cause of the residual image characteristics.
The silicon single crystal substrate has a main dopant of B and a B concentration of 1X 1016atoms/cm3P is as follows-A silicon single crystal substrate.
If it is such a p-Since the type silicon single crystal substrate has a limitation in "B diffused in the epitaxial layer due to the deposition of the epitaxial layer or the heat treatment in the device fabrication process", B in the epitaxial layer can be suppressed from forming a complex with oxygen, and the gettering capability and the substrate strength can be improved by increasing the oxygen concentration between the crystal lattices of the silicon single crystal substrate.
In addition, the silicon single crystal substrate is an n-type silicon single crystal substrate.
Since the n-type silicon single crystal substrate contains almost no B, the afterimage characteristics can be suppressed regardless of the diffusion of oxygen from the substrate.
The case of an n-type silicon single crystal substrate is also similar to that of p-Similarly to the silicon single crystal substrate of the type, the formation of a complex of B and oxygen in the epitaxial layer can be suppressed, and the gettering capability and substrate strength can be improved by increasing the interstitial oxygen concentration of the silicon single crystal substrate.
In addition, the present invention provides a solid-state imaging device comprising a photodiode section, a memory section and a calculation section, wherein at least the photodiode section is formed in the silicon epitaxial layer of the silicon epitaxial wafer for the solid-state imaging device according to the present invention.
The solid-state imaging element has at least a photodiode section, a memory section, and a computing section, but since the photodiode section has an afterimage characteristic, Ga is used as a main dopant and B concentration is 5X 1014atoms/cm3The following p-type silicon single crystal substrate is used as an epitaxial layer in which at least a photodiode portion is formed, and a solid-state imaging device in which image sticking characteristics are suppressed can be manufactured.
(III) advantageous effects
As described above, according to the present invention, it is possible to provide a silicon single crystal substrate for a solid-state imaging device and a solid-state imaging device, which can suppress the afterimage characteristics of the solid-state imaging device. Further, a silicon epitaxial wafer for a solid-state imaging device and a solid-state imaging device can be provided, which can suppress the afterimage characteristics of the solid-state imaging device.
Drawings
Fig. 1 is a schematic view showing an example of a silicon single crystal substrate for a solid-state imaging device according to the present invention.
FIG. 2 is a schematic view showing an example of a single crystal pulling apparatus by the CZ method.
Fig. 3A is a schematic diagram showing an example of the solid-state imaging module according to the present invention.
Fig. 3B is a schematic diagram showing an example of the method of manufacturing the solid-state imaging device according to the present invention.
Fig. 4 is a configuration diagram showing an example of the afterimage characteristic evaluation device.
Fig. 5 is a view showing an example of a measurement procedure of the method for evaluating a semiconductor substrate.
Fig. 6 is a graph showing the evaluation results of the afterimage characteristics of example 1 and comparative example 1.
Fig. 7 is a schematic view showing an example of a silicon epitaxial wafer for a solid-state imaging device according to the present invention.
Description of the reference numerals
10: a p-type silicon single crystal substrate; 20, a single crystal pulling device; 201, a crucible; 202, a bottom chamber; 203, single crystal; 204, a top chamber; 205, a winding mechanism; 206 metal lines; 207, seed crystal; 208 seed crystal support part; 209, a quartz crucible; 210: a graphite crucible; 211, a heater; 212, heat insulating material; 213, supporting the shaft; 214, a driving device; 215, a rectifying cylinder; 216, silicon melt; 30, a solid-state image pickup module; 301 a first substrate; 302: a second substrate; 303, a photodiode section; 304, a memory part and an arithmetic part; 305: a gate oxide film; STI (component separation section) 306; 307, wiring; 308, an interlayer insulating film; 40 residual image characteristic evaluation device; 401, PN junction; 402, a substrate; 403, an illumination part; 404, an optical fiber; 405, an illuminometer; 406 Kelvin probe; 407, a current measurer (SMU); 70, silicon epitaxial wafer; 701 p-type silicon epitaxial layer; 702 a silicon single crystal substrate.
Detailed Description
The present inventors have made extensive studies on suppression of the residual image characteristics of a solid-state imaging device, and as a result, have focused particularly on a complex of B and oxygen related to the residual image characteristics, and have conceived to use Ga instead of B as a p-type host dopant in order to reduce the complex.
In addition, as an example of using Ga instead of B as a p-type dopant, a silicon single crystal used for a solar cell is known (patent document 3).
However, the solar cell is different in manufacturing process and manufacturer and also in technical field from the solid-state image pickup device.
In addition, the effect of suppressing the light deterioration is aimed at when used in a solar cell, and the effect of suppressing the afterimage characteristic is aimed at when used in a solid-state imaging device, and therefore, the intended effects are completely different.
Therefore, there has been no case, or even no idea, of using a p-type silicon single crystal substrate in which Ga is a main dopant as a silicon single crystal substrate for a solid-state imaging device.
Further, it is considered that if it is intended to suppress formation of a complex of B and oxygen related to the afterimage characteristics, an FZ substrate (a silicon single crystal substrate obtained by slicing a silicon single crystal which is produced by the FZ method and contains almost no oxygen) is used with the aim of reducing the oxygen concentration.
However, in the case of using the FZ substrate as the solid-state imaging device, since there are disadvantages such as the following, the FZ substrate is hardly used as the solid-state imaging device, and the disadvantages are: (1) since oxygen is hardly contained, the substrate strength is low and the gettering capability by oxygen precipitate is not obtained; (2) since nitrogen is doped for increasing the substrate strength, the resistivity is changed due to the generation of a nitrogen donor and the depletion layer width of the photodiode portion is changed, thereby affecting the component characteristics; (3) the diameter is smaller than that of the CZ substrate by one generation (currently, the maximum diameter in the mass production level is 300mm for the CZ substrate and 200mm for the FZ substrate), and the like.
As described above, it was found that a p-type CZ silicon single crystal substrate in which Ga was the main dopant and B concentration was 5X 1014atoms/cm3The following low values are excellent in the afterimage characteristics of the solid-state imaging device, the substrate strength, and the like, and the present invention has been completed. Further, it was found that the solid-state imaging device has good afterimage characteristics as long as the silicon epitaxial wafer has a silicon epitaxial layer having the same Ga and B conditions as those described above, and the present invention was completed.
The present invention will be described in detail below with reference to the accompanying drawings as an example of an embodiment, but the present invention is not limited thereto.
Fig. 1 shows a schematic view of a silicon single crystal substrate for a solid-state imaging device according to the present invention. As shown in FIG. 1, the silicon single crystal substrate 10 of the present invention is a p-type CZ silicon single crystal substrate in which the main dopant is Ga and the concentration of B is 5X 1014atoms/cm3The following.
First, since the silicon single crystal substrate is produced by the CZ method, the substrate has advantages such as higher substrate strength, gettering capability of oxygen precipitates, and a larger substrate diameter compared to, for example, an FZ silicon single crystal substrate containing almost no oxygen. The substrate diameter is not particularly limited, but may be, for example, 300mm or more, or 450mm or more.
The main dopant, i.e., the dopant that determines the substrate conductivity type, is not B doped in a conventional silicon single crystal substrate for a solid-state imaging device, but Ga. Further, the B concentration was 5X 1014atoms/cm3The lower values are as follows. Accordingly, the present invention can provide a silicon single crystal substrate which can suppress "because BO", which is a problem in the production of a solid-state imaging device in the conventional product in which the main dopant is B2The characteristics of afterimage generated by the complex ", and the quality is superior to the existing solid-state imaging device in terms of afterimage characteristics regardless of the oxygen concentration between the cells.
The Ga concentration is not particularly limited, and may be appropriately determined according to the desired resistivity and the like.
The lower limit of the B concentration is not particularly limited. Although there is a possibility that the incorporation of BO is unavoidable in the production of a single crystal, the BO is prevented2The production of the composite is preferably as small as possible.
As long as the above conditions are satisfied, the dopant may be mixed with other dopants in addition to Ga and B.
The oxygen concentration of the silicon single crystal substrate 10 may be set to, for example, 1ppma or more and 15ppma or less.
If the amount is 15ppma or less, the probability of occurrence of white spots (or dark current) in which oxygen becomes a generation center in the depletion layer even if light is not incident, and electron-hole pairs are generated to generate charges can be reduced.
Further, if the amount is 1ppma or more, the problems of decrease in substrate strength and insufficient gettering capability for heavy metal contamination can be more reliably prevented.
Further, it is preferably 10ppma or less, more preferably 5ppma or less.
An example of the method for producing the silicon single crystal substrate 10 of the present invention will be described in detail below. First, a configuration example of a single crystal pulling apparatus by the CZ method is shown with reference to FIG. 2.
The single crystal pulling apparatus 20 is composed of a bottom chamber 202 and a top chamber 204, wherein the bottom chamber 202 accommodates a crucible 201 for melting a raw material, and the top chamber 204 accommodates and takes out a pulled single crystal (single crystal rod) 203. Further, a wire winding mechanism 205 for pulling up the single crystal is provided at the top of the top chamber 204, and the wire 206 is lowered or wound up in accordance with the growth of the single crystal. Further, at the tip of this metal wire 206, a seed crystal 207 for pulling up a silicon single crystal is attached to a seed crystal support portion 208.
On the other hand, the crucible 201 in the bottom chamber 202 is configured such that the inner side is a quartz crucible 209 and the outer side is a graphite crucible 210, and a heater 211 for melting the polycrystalline silicon raw material added to the crucible is disposed around the crucible 201, and the heater is surrounded by a heat insulating material 212. Further, the crucible 201 is filled with a silicon melt 216 melted by heating with a heater. The crucible 201 is supported by a support shaft 213 which is rotatable and movable up and down, and a driving device 214 for this purpose is attached to the bottom of the bottom chamber 202. Further, a rectifying cylinder 215 for rectifying the inert gas introduced into the furnace may be used.
Next, a method for producing a silicon single crystal using the above-described apparatus will be described. First, a polycrystalline silicon raw material and Ga as a dopant are placed in a crucible 201, and heated by a heater 211 to melt the raw material. In the present embodiment, Ga is put into a crucible together with a polycrystalline silicon raw material before melting, but since fine concentration adjustment is required in mass production, it is desirable to produce a Ga-doped silicon single crystal with a high concentration, finely pulverize the Ga-doped silicon single crystal to produce a dopant, and put the polycrystalline silicon raw material into the crucible after melting to adjust the Ga-doped silicon single crystal to a desired concentration.
Next, after the polycrystalline silicon raw material is completely melted, a seed crystal 207 for growing a single crystal rod is attached to the tip of the wire 206 of the wire winding mechanism 205, and the tip of the seed crystal 207 is brought into contact with the silicon melt 216 by gently lowering the wire 206. At this time, the crucible 201 and the seed crystal 207 are rotated in opposite directions to each other, and the inside of the pulling machine is in a reduced pressure state and is filled with an inert gas such as argon gas flowing from the top of the furnace.
After the temperature around the seed crystal 207 is stabilized, the seed crystal 207 is gently wound up while rotating the seed crystal 207 and the crucible 201 in opposite directions to each other, and the seed crystal 207 starts to be pulled up. In addition, necking is performed to eliminate slip dislocation generated in the seed crystal 207. After necking is performed until the thickness and length of slip dislocation are eliminated, the diameter is gradually enlarged to produce a taper portion of the single crystal 203, and the diameter is enlarged to a desired diameter. When the diameter of the taper is enlarged to a predetermined diameter, the taper is transferred to a constant diameter portion (columnar portion) for producing a single crystal ingot. At this time, the rotation speed of the crucible, the pulling speed, the pressure of the inert gas in the chamber, the flow rate, and the like are appropriately adjusted in accordance with the oxygen concentration contained in the grown single crystal. In addition, the crystal diameter is controlled by adjusting the temperature and the pulling rate.
After pulling the column part of the single wafer by a predetermined length, the diameter of the crystal is reduced and the tail part is formed, the tip of the tail part is separated from the silicon melt surface, and the grown silicon single crystal is wound up to the top chamber 204 and waits for the crystal to cool. After the single crystal rod is cooled to a removable temperature, it is taken out of the pulling machine and transferred to a step of processing the crystal into a wafer.
In the processing step, first, the tapered portion and the tail portion are cut, and the periphery of the single crystal rod is cylindrically ground to cut and process a block having an appropriate size. The single crystal block having an appropriate size is sliced into a wafer shape by a slicing machine, and then subjected to chamfering, polishing, and the like as necessary, and further subjected to etching to remove processing strain, thereby producing a wafer as a substrate.
In the above examples, an example in which only Ga is intentionally doped is given, but the dopant is not limited thereto. The main dopant determining the conductivity type is Ga-doped and the concentration of B is set to 5X 1014atoms/cm3The following may be used.
May be appropriately determined according to the desired resistivity and the like.
The resistivity for the solid-state imaging element is preferably in the range of 0.1 to 20 Ω cm, for example.
Fig. 3A shows an example of a solid-state imaging device according to the present invention. Here, a back-illuminated solid-state imaging module is taken as an example, but the present invention is not limited thereto.
The solid-state imaging device 30 includes a photodiode section 303, a memory section, and a calculation section 304. The solid-state imaging element 30 is formed by bonding various elements on a first substrate 301 (a silicon single crystal substrate 10 of the present invention) and a second substrate 302.
The first substrate, i.e., the substrate on which the photodiode section 303 is formed, is a p-type CZ silicon single crystal substrate in which the main dopant is Ga, and the B concentration is 5X 10, as in the silicon single crystal substrate 10 of the present invention14atoms/cm3The following.
On the other hand, the second substrate may be, for example, a CZ silicon single crystal substrate. It may be determined as appropriate, instead of Ga as the main dopant in the first substrate.
In the case of the solid-state imaging element 30, the afterimage is generatedThe photodiode section 303 is used, and therefore, at least the first substrate 301 is doped with Ga as a main dopant and B at a concentration of 5X 1014atoms/cm3The following p-type CZ silicon single crystal substrate is a solid-state imaging device in which afterimage characteristics are suppressed.
Fig. 3B shows an example of a method for manufacturing the solid-state imaging module 30.
First, the first substrate 301 and the second substrate 302, which are substrates according to the present invention, are prepared.
On these substrates, various elements (the photodiode section 303 (light receiving element), the memory section, and the arithmetic section 304) are formed by forming a gate oxide film 305, and STI (element isolation section) 306, wiring 307, an interlayer insulating film 308, and the like are also formed.
Then, the first substrate 301 and the second substrate 302 on which various components are formed are bonded to each other, thereby producing the solid-state imaging device 30.
In addition, a solid-state imaging device using a silicon epitaxial wafer capable of suppressing an afterimage characteristic, which is different from the solid-state imaging device using the silicon single crystal substrate described above, will be described below.
First, fig. 7 shows a schematic view of a silicon epitaxial wafer for a solid-state imaging device according to the present invention. As shown in FIG. 7, the silicon epitaxial wafer 70 of the present invention has Ga as a main dopant and B at a concentration of 5X 10 on the surface of a silicon single crystal substrate 70214atoms/cm3The following p-type silicon epitaxial layer 701. In the silicon epitaxial wafer 70, since the concentration of B originally in the silicon epitaxial layer 701 is extremely low and oxygen is hardly contained, even if oxygen or B diffuses from the silicon single crystal substrate 702, formation of a composite of oxygen and B can be suppressed, and the afterimage characteristics can be suppressed.
The silicon single crystal substrate 702 itself (e.g., a main dopant) is not limited and may be determined as appropriate. An example of the silicon single crystal substrate 702 is described below.
The silicon single crystal substrate 702 may be, for example, Ga as a main dopant and 5X 10 as a B concentration14atoms/cm3The following p-type silicon single crystal substrate. In the case of such a p-type silicon single crystal substrate, the diffusion of B and oxygen into the silicon epitaxial layer 701 due to the heat treatment applied to the silicon single crystal substrate can be more reliably suppressed,thereby causing a situation in which an afterimage characteristic is generated.
The silicon single crystal substrate 702 may have, for example, a main dopant of B and a B concentration of 1X 1018atoms/cm3Above p+A silicon single crystal substrate. If it is such a p+The silicon single crystal substrate of the type can further improve gettering capability of metal impurities and the like which may be generated by deposition of the silicon epitaxial layer 701 and heat treatment in the fabrication process during the deposition. In this case, although there may be B slave p+The type silicon single crystal substrate diffuses into the epitaxial layer, but since the epitaxial layer contains almost no oxygen, it is possible to suppress formation of a complex of B and oxygen, which is a cause of image sticking characteristics. The upper limit of the concentration of B is not particularly limited, but the higher the concentration, the better, for example, the solid solubility limit of B to the silicon single crystal may be.
At this time, p is+Although the interstitial oxygen concentration of the type silicon single crystal substrate is not limited, the interstitial oxygen concentration is more reliably prevented from being increased from p+The type silicon single crystal substrate is preferably diffused into the epitaxial layer, and the interstitial oxygen concentration is preferably 20ppma or less, more preferably 15ppma or less.
The silicon single crystal substrate 702 may have, for example, a main dopant of B and a B concentration of 1X 1016atoms/cm3P is as follows-A silicon single crystal substrate. If it is such a p-Since the type silicon single crystal substrate has a limitation in "B diffused in the epitaxial layer due to the deposition of the epitaxial layer or the heat treatment in the device fabrication process", B in the epitaxial layer can be suppressed from forming a complex with oxygen, and the gettering capability and the substrate strength can be improved by increasing the oxygen concentration between the crystal lattices of the silicon single crystal substrate. The lower limit of the concentration of B is not particularly limited, and the lower the concentration, the more B can be inhibited from forming a complex with oxygen.
The silicon single crystal substrate 702 may be an n-type silicon single crystal substrate, for example. If it is an n-type silicon single crystal substrate, it contains almost no B and is therefore compatible with p-Similarly, the type silicon single crystal substrate can more reliably suppress the formation of a complex of B and oxygen in the epitaxial layer, and can increase the gettering capability and substrate strength by increasing the interstitial oxygen concentration of the silicon single crystal substrate.
Next, a method for manufacturing the silicon epitaxial wafer of the present invention will be described.
First, the silicon single crystal substrate 702 can be produced by, for example, using the single crystal pulling apparatus 20 of the CZ method shown in fig. 2, and subjected to slicing, chamfering, and the like. In the case of intentionally doping B, the B dopant may be melted together with the raw material at a desired concentration during pulling of the single crystal.
Further, a silicon epitaxial layer 701 is stacked on the manufactured silicon single crystal substrate 702. In this case, the epitaxial device used is not particularly limited, and for example, the same device as a conventional device can be used. The silicon single crystal substrate 702 is placed on a susceptor in a furnace, the furnace is heated, and a gas containing, for example, gallium chloride is also flowed in the furnace as a carrier gas or a source gas, and also as a Ga doping gas. Thus, a "p-type semiconductor device in which the main dopant is Ga" can be stacked, and the concentration can be suppressed to 5X 10 even if B is inevitably mixed14atoms/cm3The silicon epitaxial wafer 70 of the present invention can be manufactured by using the epitaxial layer 701 ″ below (lower is preferable).
The method of doping Ga is not limited to the above method, and may be appropriately determined according to a desired concentration or the like.
Next, a solid-state imaging device using the silicon epitaxial wafer will be described, but the present invention is not limited thereto.
The solid-state imaging device includes a photodiode section, a memory section, and a calculation section, as in the solid-state imaging device 30 using the silicon single crystal substrate of fig. 3A. However, in the example of fig. 3A, the first substrate 301 on which the photodiode section 303 is formed is the silicon single crystal substrate 10 of the present invention, and is replaced with the silicon epitaxial wafer 70 described above.
In a silicon epitaxial layer formed with a photodiode portion, at least a main dopant in the silicon epitaxial layer is Ga, and a B concentration is 5 x 1014atoms/cm3Hereinafter, the quality of the afterimage characteristics is superior to that of the conventional solid-state imaging device.
Examples
The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited thereto.
(example 1)
A CZ silicon single crystal was pulled up using the apparatus of fig. 2, and sliced to produce a p-type silicon single crystal substrate for a solid-state imaging module of the present invention in which the main dopant was Ga. Specific parameters for the production are as follows. In addition, although Ga is intentionally doped, B cannot be prevented from being mixed.
Diameter 300mm, crystal orientation<100>Oxygen concentration: 3.4-10.5 ppma, resistivity 5 Ω cm, Ga concentration: 3X 1015atoms/cm3And B concentration: 5X 1013atoms/cm3Below (below the lower limit value measured by SIMS).
Comparative example 1
A p-type silicon single crystal substrate for a conventional solid-state imaging device in which the main dopant was B was produced. Specific parameters for the production are as follows. Other than that, the same procedure as in example 1 was repeated.
Diameter 300mm, crystal orientation<100>Oxygen concentration: 3.4-10.5 ppma, resistivity 10 Ω cm, B concentration: 1X 1015atoms/cm3。
PN junctions were formed using the substrates of example 1 and comparative example 1, and the oxygen concentration dependence of the afterimage characteristics was compared on a substrate scale (evaluated as "leak current ratio before and after light irradiation" after annealing at 450 ℃ for 75 hours). The evaluation device and method are described in detail below.
Fig. 4 shows an example of the afterimage characteristic evaluation device 40 for explaining a specific evaluation method. The evaluation apparatus includes a device (illumination unit) 403 for irradiating a semiconductor substrate 402 having a PN structure 401 with light, an optical fiber 404, a device (illuminometer) 405 for measuring the amount of light, and a current measuring instrument (SMU)407 having a Kelvin Probe (Kelvin Probe) 406. Further, a substrate is provided, and after light irradiation of a predetermined illuminance is performed for a predetermined time on the surface of the semiconductor substrate 402 (a light irradiation step), a step of measuring the carrier generation amount after the light irradiation is performed after the light irradiation is turned off is performed.
Here, the light irradiates an LED using white light. The amount of light was 500 lux at the time of measurement. The light irradiation time was 10 seconds.
Next, the carrier generation amount of the PN junction formed as described above was measured. Fig. 5 is a conceptual diagram showing a specific light irradiation and measurement sequence. Fig. 5 is a view showing an example of a measurement procedure of the method for evaluating a semiconductor substrate.
The amount of carriers generated by light irradiation is affected by the type of the semiconductor substrate 402 or the light element, particularly carbon element, contained in the semiconductor substrate 402. Therefore, in order to avoid that the difference in the amount of carriers generated by light irradiation at first affects the afterimage characteristics, the amount of carriers generated (the amount of carriers generated in light irradiation) is measured at once while light irradiation is performed, as shown in fig. 5. In this way, the semiconductor substrate was evaluated in consideration of the difference in the amount of carriers initially generated.
The measurement time of the carrier generation amount after the light irradiation was turned off was set to 1 second.
In fig. 5, the reason why the measurement is stopped immediately before the measurement of the carrier generation amount after the off-light irradiation is performed is to more reliably avoid noise at the time of the off-light irradiation.
In addition, the afterimage characteristics were evaluated from the ratio of the current values of the carrier measurement probe at the time of on/off of light irradiation. For example, a higher current value after the light irradiation is turned off indicates that the carriers are captured, and it is presumed that the afterimage characteristics are poor.
In an actual solid-state imaging device, electric charges are generated by electron/hole pairs generated by light incident when a shutter is opened, and an image is constructed by introducing the electric charges, but it is important to rapidly discharge the electron/hole pairs after the shutter is closed, and if the discharge is slow, the electron/hole pairs are used as an afterimage and affect the next frame.
(evaluation results of example 1 and comparative example 1)
The evaluation results are shown in fig. 6. In the case of comparative example 1 (main doping is B), it was found that at any oxygen concentration [ Oi ]]Next, the current before and after light irradiation was larger than that of example 1 (the main doping was Ga), and the afterimage characteristics were inferior. Specifically, the current ratio before and after light irradiation was 2.7 to 5.2 in comparative example 1, and 1.2 to 1.6 in example 1. If the annealing is carried out for 75 hours at 450 DEG CFire is generating BO2Although the current value was changed in comparative example 1 of the B-doped crystal having defects, BO was changed in example 1 of the Ga-doped crystal2The formation is suppressed, and thus the change in the current value (the change in the afterimage characteristics) is suppressed. In comparative example 1, it is understood that the current ratio is increased as the oxygen concentration increases, and the image retention characteristics tend to deteriorate as the oxygen concentration increases.
On the other hand, in the case of example 1, even if the oxygen concentration is increased, the current ratio before and after light irradiation is almost fixed at a low value (a value close to 1), and it can be judged that the afterimage characteristics are good.
(example 2)
A CZ silicon single crystal was pulled up using the apparatus of fig. 2, and sliced to produce a p-type silicon single crystal substrate for a solid-state imaging module of the present invention in which the main dopant was Ga. Specific parameters for the production are as follows. In addition, B is intentionally doped in a slight amount in addition to Ga.
Diameter 300mm, crystal orientation<100>Oxygen concentration: 5ppma, resistivity 4 Ω cm, Ga concentration: 3X 1015atoms/cm3And B concentration: 5X 1014atoms/cm3
In addition, evaluation of the afterimage characteristics was performed in the same manner as in example 1.
(evaluation results of example 2)
The ratio of the current before and after the light irradiation was about 1.6, and the afterimage characteristics were judged to be good.
(example 3)
In order to produce a silicon epitaxial wafer for a solid-state imaging device according to the present invention, first, a CZ silicon single crystal is pulled up by the apparatus shown in fig. 2, and sliced to produce a p-type silicon single crystal substrate in which Ga is a main dopant, and a p-type epitaxial layer in which Ga is a main dopant is formed on the substrate. Specific parameters for the production are as follows.
(silicon Single Crystal substrate)
Diameter 300mm, crystal orientation<100>Oxygen concentration: 15ppma, resistivity 4 Ω cm, Ga concentration: 3X 1015atoms/cm3And B concentration: 5X 1013atoms/cm3The following (lower limit value by SIMS)
(silicon epitaxial layer)
Film thickness of the epitaxial layer: 5 μm, resistivity 10 Ω cm, Ga concentration: 1X 1015atoms/cm3And B concentration: 5X 1013atoms/cm3The following (lower limit value by SIMS)
In addition, evaluation of the afterimage characteristics was performed in the same manner as in example 1.
(evaluation results of example 3)
The ratio of the current before and after light irradiation was about 1.8, and the afterimage characteristics were judged to be good.
Comparative example 2
Except that B (B concentration in epitaxial layer: 1X 10) is used15atoms/cm3) A silicon epitaxial wafer was produced under the same conditions as in example 3, except that Ga was used as a dopant for the silicon epitaxial layer, and the image sticking characteristics were evaluated in the same manner as in example 1.
(evaluation result of comparative example 2)
The current ratio before and after light irradiation was about 8.2, which was larger than that in example 3, and it was judged that the afterimage characteristics were inferior.
(example 4)
In order to fabricate a silicon epitaxial wafer for a solid-state imaging device according to the present invention, a CZ silicon single crystal is pulled up by the apparatus shown in fig. 2, and sliced to fabricate a p-type epitaxial wafer having B as a main dopant+A silicon single crystal substrate of type, and a p-type epitaxial layer whose main dopant is Ga is formed on the substrate. Specific parameters for the production are as follows.
(silicon Single Crystal substrate)
Diameter 300mm, crystal orientation<100>Oxygen concentration: 10ppma, resistivity 0.01 Ω cm, B concentration: 8.5X 1018atoms/cm3
(silicon epitaxial layer)
Film thickness of the epitaxial layer: 5 μm, resistivity 10 Ω cm, Ga concentration: 1X 1015atoms/cm3And B concentration: 5X 1013atoms/cm3The following (lower limit value by SIMS)
In addition, evaluation of the afterimage characteristics was performed in the same manner as in example 1.
(evaluation result of example 4)
The ratio of the current before and after the light irradiation was about 2.1, and the afterimage characteristics were judged to be good.
(example 5)
In order to fabricate a silicon epitaxial wafer for a solid-state imaging device according to the present invention, a CZ silicon single crystal is pulled up by the apparatus shown in fig. 2, and sliced to fabricate a p-type epitaxial wafer having B as a main dopant-A silicon single crystal substrate of type, and a p-type epitaxial layer whose main dopant is Ga is formed on the substrate. Specific parameters for the production are as follows.
(silicon Single Crystal substrate)
Diameter 300mm, crystal orientation<100>Oxygen concentration: 15ppma, resistivity 10 Ω cm, B concentration: 1X 1015atoms/cm3
(silicon epitaxial layer)
Film thickness of the epitaxial layer: 5 μm, resistivity 10 Ω cm, Ga concentration: 1X 1015atoms/cm3And B concentration: 5X 1013atoms/cm3The following (lower limit value by SIMS)
In addition, evaluation of the afterimage characteristics was performed in the same manner as in example 1.
(evaluation result of example 5)
The ratio of the current before and after the light irradiation was about 2.2, and the afterimage characteristics were judged to be good.
(example 6)
In order to produce a silicon epitaxial wafer for a solid-state imaging device according to the present invention, first, a CZ silicon single crystal is pulled up by the apparatus shown in fig. 2, and sliced to produce a p-type silicon single crystal substrate in which Ga is a main dopant, and a p-type epitaxial layer in which Ga is a main dopant is formed on the substrate. Specific parameters for the production are as follows. In addition, B is intentionally doped in a small amount in addition to Ga in the epitaxial layer.
(silicon Single Crystal substrate)
Diameter 300mm, crystal orientation<100>Oxygen concentration: 15ppma, resistivity 4 Ω cm, Ga concentration: 3X 1015atoms/cm3And B concentration: 5X 1013atoms/cm3The following (lower limit value measured by SIMS)
(silicon epitaxial layer)
Film thickness of the epitaxial layer: 5 mu m,Resistivity 8 Ω cm, Ga concentration: 1X 1015atoms/cm3And B concentration: 5X 1014atoms/cm3
In addition, evaluation of the afterimage characteristics was performed in the same manner as in example 1.
(evaluation result of example 6)
The ratio of the current before and after the light irradiation was about 2.3, and the afterimage characteristics were judged to be good.
The present invention is not limited to the above embodiments. The above-described embodiments are examples, and any embodiments having substantially the same configuration as the technical idea described in the claims of the present invention and producing the same operational effects are included in the technical scope of the present invention.
Claims (9)
1. A silicon single crystal substrate for a solid-state imaging element obtained by slicing a silicon single crystal produced by the CZ method,
the silicon single crystal substrate is a p-type silicon single crystal substrate in which the main dopant is Ga and the concentration of B is 5 x 1014atoms/cm3The following.
2. The silicon single crystal substrate for a solid-state imaging device according to claim 1,
the interstitial oxygen concentration in the p-type silicon single crystal substrate is 1ppma or more and 15ppma or less.
3. A solid-state imaging device having an optical diode section, a memory section and an arithmetic section,
at least the photodiode portion is formed on the silicon single crystal substrate for the solid-state imaging device according to claim 1 or 2.
4. A silicon epitaxial wafer for a solid-state imaging device, which has a silicon epitaxial layer on a surface of a silicon single crystal substrate,
the silicon epitaxial layer is a p-type epitaxial layer with Ga as main dopant, andand B concentration is 5X 1014atoms/cm3The following.
5. The epitaxial silicon wafer for a solid-state imaging device according to claim 4, wherein the epitaxial silicon wafer is a silicon epitaxial wafer,
the silicon single crystal substrate is a p-type silicon single crystal substrate in which the main dopant is Ga and the concentration of B is 5 x 1014atoms/cm3The following.
6. The epitaxial silicon wafer for a solid-state imaging device according to claim 4, wherein the epitaxial silicon wafer is a silicon epitaxial wafer,
the silicon single crystal substrate is mainly doped with B with a concentration of 1 × 1018atoms/cm3Above p+A silicon single crystal substrate.
7. The epitaxial silicon wafer for a solid-state imaging device according to claim 4, wherein the epitaxial silicon wafer is a silicon epitaxial wafer,
the silicon single crystal substrate is mainly doped with B with a concentration of 1 × 1016atoms/cm3P is as follows-A silicon single crystal substrate.
8. The epitaxial silicon wafer for a solid-state imaging device according to claim 4, wherein the epitaxial silicon wafer is a silicon epitaxial wafer,
the silicon single crystal substrate is an n-type silicon single crystal substrate.
9. A solid-state imaging device having an optical diode section, a memory section and an arithmetic section,
at least the photodiode portion is formed in the silicon epitaxial layer of the silicon epitaxial wafer for the solid-state imaging device according to any one of claims 4 to 8.
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| JP2021088498A (en) | 2021-06-10 |
| JP7318518B2 (en) | 2023-08-01 |
| KR20210065043A (en) | 2021-06-03 |
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