JP6988990B2 - Manufacturing method of epitaxial silicon wafer and epitaxial silicon wafer - Google Patents

Description

The present invention relates to a method for manufacturing an epitaxial silicon wafer and an epitaxial silicon wafer.

Metal contamination is one of the factors that deteriorate the characteristics of semiconductor devices. For example, in a back-illuminated solid-state image sensor, the metal mixed in the epitaxial silicon wafer that is the substrate of the element causes an increase in the dark current of the solid-state image sensor, and causes a defect called a white scratch defect. By arranging the wiring layer etc. below the sensor part, the back-illuminated solid-state image sensor can directly capture the light from the outside into the sensor and shoot clearer images and moving images even in dark places. In recent years, it has been widely used in mobile phones such as digital video cameras and smartphones. Therefore, it is desired to reduce white scratch defects as much as possible.

The mixing of metal into a silicon wafer mainly occurs in the manufacturing process of an epitaxial silicon wafer and the manufacturing process of a solid-state image sensor (device manufacturing process). Metal contamination in the manufacturing process of epitaxial silicon wafers is caused by heavy metal particles from the constituent materials of the epitaxial growth furnace, or because chlorine-based gas is used as the gas in the furnace during epitaxial growth, the piping material is corroded by metal. It may be due to heavy metal particles. In recent years, these metal contaminations have been improved to some extent by replacing the constituent materials of the epitaxial growth furnace with materials having excellent corrosion resistance, but they are not sufficient. On the other hand, in the manufacturing process of the solid-state image sensor, there is a concern about heavy metal contamination of the epitaxial silicon wafer during each process such as ion implantation, diffusion and oxidative heat treatment.

Therefore, in general, metal contamination on the epitaxial silicon wafer is avoided by forming a gettering layer for capturing metal on the epitaxial silicon wafer.

Here, as a technique for forming a gettering layer, a technique for irradiating cluster ions prior to forming a silicon epitaxial layer is known. Patent Document 1 describes a first step of irradiating the surface of a silicon wafer with cluster ions to form a modified layer in which constituent elements of the cluster ions are solid-dissolved on the surface layer portion of the silicon wafer, and the first step. After that, a second step of performing heat treatment for recovering crystallinity so that the haze level of the surface of the silicon wafer becomes 0.20 ppm or less, and after the second step, epitaxial on the modified layer of this silicon wafer. A method for manufacturing a semiconductor epitaxial wafer having a third step of forming a layer is disclosed.

The modified layer formed by the technique described in Patent Document 1 becomes a strong gettering site. However, depending on the cluster ion irradiation conditions, the crystallinity of the outermost surface of the silicon wafer before forming the epitaxial layer is disturbed, so that epitaxial defects may occur in the epitaxial layer after forming the epitaxial layer. Therefore, in the technique described in Patent Document 1, the crystallinity of the surface layer portion of the silicon wafer disturbed by the cluster ion irradiation is restored before the epitaxial layer is formed.

Further, Patent Document 2 discloses an epitaxial silicon wafer in which the surface of a silicon wafer is irradiated with cluster ions containing carbon and hydrogen as constituent elements to form a modified layer, and then an epitaxial layer is formed. In this epitaxial silicon wafer, a hydrogen high concentration region in which hydrogen is retained at a high concentration is formed in the reformed layer even after the epitaxial layer is formed. Then, the hydrogen existing in the hydrogen high concentration region can passivate the point defects in the epitaxial layer and enhance the crystallinity of the epitaxial layer. Therefore, the epitaxial wafer disclosed in Patent Document 2 has a strong gettering ability, and the semiconductor device manufactured by using the epitaxial wafer can improve its device characteristics.

Japanese Unexamined Patent Publication No. 2014-099472 Japanese Unexamined Patent Publication No. 2016-051729

In recent years, there has been a demand for the establishment of technology that can further improve the characteristics of semiconductor devices. Therefore, in order to enhance the passive effect of hydrogen, the present inventors have formed an epitaxial silicon wafer in the reformed layer by irradiation with cluster ions, and further increased the hydrogen peak concentration in this high hydrogen concentration region. Considered to get. By increasing the amount of hydrogen dose, it is possible to increase the hydrogen peak concentration in the high-concentration hydrogen injection region immediately after irradiation with cluster ions. However, since the cluster ion irradiation is performed with a high dose amount, the injection damage formed on the surface layer portion of the silicon wafer also increases. Therefore, if the amount of hydrogen dose is simply increased, forming a silicon epitaxial layer after irradiation with cluster ions causes frequent occurrence of epitaxial defects.

Therefore, the present inventors have studied to perform a recovery heat treatment before forming an epitaxial layer while increasing the amount of hydrogen dose during irradiation with cluster ions. As disclosed in Patent Document 1, if the recovery heat treatment is performed for a sufficient time, the generation of epitaxial defects can be suppressed even if the amount of hydrogen dose is increased. However, since hydrogen is a light element, hydrogen is diffused in the hydrogen high concentration region formed by cluster ion irradiation due to the recovery heat treatment, and the hydrogen peak concentration in the reformed layer is even before the epitaxial layer is formed. Will decrease sharply. It was also found that the gettering ability may be reduced depending on the heat treatment conditions of the recovery heat treatment. If the crystal recovery is insufficient, such as in a short recovery heat treatment, epitaxial defects will occur, and the hydrogen diffusion rate is extremely high, so the hydrogen peak concentration in the modified layer will decrease rapidly. It could be.

As described above, it has been difficult to suppress the occurrence of epitaxial defects while maintaining a high concentration of hydrogen in the modified layer while exhibiting high gettering ability. However, in order to further improve the characteristics of semiconductor devices, it is necessary to overcome these technical problems at the same time.

Therefore, the present invention provides an epitaxial silicon wafer capable of suppressing the occurrence of epitaxial defects while maintaining a high concentration of hydrogen in the modified layer while exhibiting higher gettering ability, and a method for manufacturing the same. The purpose is.

In order to solve the above problems, the present inventors have diligently studied, and by optimizing the heat treatment conditions after irradiation with cluster ions, the hydrogen peak concentration is maintained at a high concentration while increasing the gettering ability, and further, epitaxial defects. It was found that the occurrence of can be suppressed. The present invention has been completed based on the above findings, and its gist structure is as follows.

(1) First, the surface of a silicon wafer is irradiated with cluster ions containing carbon and hydrogen as constituent elements to form a modified layer in which the constituent elements of the cluster ions are solid-solved on the surface layer portion of the silicon wafer. Process and
After the first step, a second step of performing a flash lamp annealing process on the silicon wafer and a second step.
After the second step, a third step of forming a silicon epitaxial layer on the modified layer of the silicon wafer is provided.
In the first step, the amount of hydrogen dose due to the cluster ion irradiation was set to 2.8 × 10 ¹⁵ atoms / cm ² or more.
A method for manufacturing an epitaxial silicon wafer, wherein the flash lamp annealing treatment in the second step has a processing time of 0.1 ms or more and 20 ms or less and a treatment temperature of 800 ° C. or higher and 1200 ° C. or lower.

(2) The method for manufacturing an epitaxial silicon wafer according to (1) above, wherein the amount of carbon dose due to the cluster ion irradiation is 1.7 × 10 ¹⁵ atoms / cm ^{2 or more.}

(3) The method for manufacturing an epitaxial silicon wafer according to (1) or (2) above, wherein the processing temperature of the flash lamp annealing treatment in the second step is 1000 ° C. or higher and 1150 ° C. or lower.

(4) The epitaxial silicon wafer according to any one of (1) to (3) above, wherein the processing time of the flash lamp annealing treatment in the second step is 0.1 ms or more and 5 ms or less. Production method.

(5) The method for manufacturing an epitaxial silicon wafer according to any one of (1) to (4) above, wherein the oxygen concentration of the silicon wafer is 12 × 10 ¹⁷ atoms / cm ^{3 or less.}

The oxygen concentration of the silicon wafer in this specification conforms to ASTM F121-1979.

(6) Silicon wafer and
A modified layer in which carbon and hydrogen are solid-solved formed on the surface layer of the silicon wafer, and
The silicon epitaxial layer formed on the modified layer and
Have,
The peak oxygen concentration of the oxygen concentration profile in the thickness direction of the modified layer is 5 × 10 ¹⁸ atoms / cm ³ or less, and the peak hydrogen concentration of the hydrogen concentration profile is 2 × 10 ¹⁸ atoms / cm ³ or more. ,
An epitaxial silicon wafer characterized in that the epitaxial defects on the surface of the epitaxial layer are 1.0 × 10 ⁻² pieces / cm ^{2 or less.}

(7) The epitaxial silicon wafer according to (6) above, wherein the half-value width of the hydrogen concentration profile in the thickness direction of the modified layer is 150 nm or less, and the half-value width of the oxygen concentration profile is 150 nm or less.

(8) The epitaxial silicon wafer according to (6) or (7) above, wherein the oxygen concentration of the silicon wafer is 12 × 10 ¹⁷ atoms / cm ^{3 or less.}

According to the present invention, an epitaxial silicon wafer and a method for manufacturing the same, which can suppress the occurrence of epitaxial defects while maintaining a high concentration of hydrogen in a high-concentration hydrogen injection region while exhibiting higher gettering ability. Can be provided.

It is a schematic sectional drawing explaining the manufacturing method of the epitaxial silicon wafer 100 by one Embodiment of this invention. It is a figure which shows the density profile and the TEM cross-sectional view of the silicon wafer surface layer part after flash lamp annealing in the invention example 1. FIG. It is a figure which shows the density profile and the TEM cross-sectional view of the silicon wafer surface layer part after flash lamp annealing in the prior art example 1. FIG. It is a figure which shows the density profile and the TEM cross-sectional view of the silicon wafer surface layer part after flash lamp annealing in the comparative example 1. FIG. It is a density profile in the vicinity of the surface layer portion of the silicon wafer after forming the epitaxial layer in the first aspect of the invention. It is a density profile in the vicinity of the surface layer portion of the silicon wafer after forming the epitaxial layer in the conventional example 1. It is a TEM cross-sectional view after forming an epitaxial layer in the invention example 1. FIG. It is a TEM cross-sectional view after forming an epitaxial layer in the prior art example 1. FIG. 5 is a hydrogen concentration profile of the surface layer of a silicon wafer after flash lamp annealing in Examples 5 and 6.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In principle, the same reference numbers are assigned to the same components, and the description thereof will be omitted. Although the details will be described later, for convenience of explanation, the modified layer immediately after irradiation with cluster ions is designated by reference numeral 18A, the modified layer after flash lamp annealing treatment is designated by reference numeral 18B, and the modified layer after forming the silicon epitaxial layer is designated by reference numeral 18B. The reference numeral 18C is added to the above, and these will be described separately. Further, in FIG. 1, for convenience of explanation, the thicknesses of the modified layers 18A, 18B, 18C and the silicon epitaxial layer 20 are exaggerated and shown with respect to the silicon wafer 10, which is different from the actual thickness ratio.

(Manufacturing method of epitaxial silicon wafer)
An embodiment of the method for manufacturing an epitaxial silicon wafer according to the present invention will be described with reference to the schematic cross-sectional view of FIG.

In the method for manufacturing an epitaxial silicon wafer 100 according to the present embodiment, the surface 10A of the silicon wafer 10 is irradiated with cluster ions 16 containing carbon and hydrogen as constituent elements, and the surface layer portion of the silicon wafer 10 is coated with the cluster ions 16. The first step (FIGS. 1, steps A and B) of forming the modified layer 18A in which the constituent elements are solid-dissolved is performed. Then, after the first step, a second step (steps C and D in FIGS. 1) of performing a flash lamp annealing (FLA) process on the silicon wafer 10 is performed. With the heat treatment of the flash lamp annealing treatment in the second step, the modified layer 18A changes to the modified layer 18B. Further, after the second step, a third step (step E in FIG. 1) of forming the silicon epitaxial layer 20 on the modified layer 18B of the silicon wafer 10 is performed. With the heat treatment at the time of forming the silicon epitaxial layer 20, the modified layer 18B is further transformed into the modified layer 18C. Here, in the present embodiment, in the first step, the amount of hydrogen dose due to irradiation of cluster ion 16 is set to 2.8 × 10 ¹⁵ atoms / cm ² or more. Further, in the present embodiment, the flash lamp annealing treatment in the second step is performed with a treatment time of 0.1 ms or more and 20 ms or less and a treatment temperature of 800 ° C. or higher and 1200 ° C. or lower. Hereinafter, the details of each step will be described in sequence.

<First step>
In the first step (steps A and B in FIGS. 1) in the present embodiment, as described above, the surface 10A of the silicon wafer 10 is irradiated with cluster ions 16 containing carbon and hydrogen as constituent elements to obtain the silicon wafer 10. A modified layer 18A in which the constituent elements of the cluster ion 16 are solid-dissolved is formed on the surface layer portion. Then, the amount of hydrogen dose by irradiation with cluster ions is set to 2.8 × 10 ¹⁵ atoms / cm ² or more.

<< Silicon Wafer >>
Examples of the silicon wafer 10 used in the first step include a bulk single crystal silicon wafer having no silicon epitaxial layer on the surface 10A to be an irradiated surface. Here, the bulk single crystal silicon wafer is generally suitable for manufacturing a back-illuminated solid-state image sensor. The oxygen concentration of the silicon wafer 10 is preferably 12 × 10 ¹⁷ atoms / cm ³ (based on ASTM F121-1979, and so on) or less. This is because if the oxygen concentration is 12 × 10 ¹⁷ atoms / cm ³ or less, the amount of oxygen captured in the modified layer 18B during the flash lamp annealing treatment can be suppressed, and the gettering ability is considered to be enhanced. .. Further, it is preferable that the oxygen concentration of the silicon wafer 10 is 1.0 × 10 ¹⁷ atoms / cm ^{3 or more.} This is because if the oxygen concentration is lower than this range, slip may occur during the flash lamp annealing process in the second step. The oxygen concentration of the silicon wafer 10 is defined by the average oxygen concentration in the thickness direction of the silicon wafer 10.

A silicon wafer having an oxygen concentration in the above concentration range can be produced by slicing a silicon single crystal ingod obtained by using a general CZ method (Czochralski method: Czochralski method) with a wire saw or the like. Carbon and / or nitrogen may be added to the silicon wafer 10 for higher gettering capability. Further, an arbitrary dopant may be added to the silicon wafer 10 to form an n-type or a p-type.

<< Cluster ion irradiation >>
Here, the term "cluster ion" as used herein refers to an atomic aggregate having various atomic numbers by colliding electrons with a gaseous molecule to dissociate the bond of the gaseous molecule by an electron impact method, and forms a fragment. It is obtained by raising and ionizing the atomic aggregate, performing mass separation of the ionized atomic aggregates of various atomic numbers, and extracting the ionized atomic aggregates of a specific mass number. That is, cluster ions are ionized by giving a positive charge or a negative charge to a cluster in which a plurality of atoms are aggregated and agglomerated, and are a single atom ion such as a carbon ion or a single molecule ion such as a carbon monoxide ion. Is clearly distinguished from.

When the silicon wafer is irradiated with the cluster ion 16 composed of carbon and hydrogen, for example, the cluster ion 16 momentarily becomes a high temperature state of about 1350 to 1400 ° C. with the energy of the cluster ion 16 when the silicon wafer is irradiated, and the silicon melts. .. After that, the silicon is rapidly cooled, and carbon and hydrogen are solid-solved near the surface in the silicon wafer. That is, the “modified layer” in the present specification means a layer in which the constituent elements of the ion to be irradiated are solid-solved at the interstitial position or the substitution position of the crystal on the surface layer of the silicon wafer. The carbon concentration profile in the depth direction of a silicon wafer by secondary ion mass spectrometry (SIMS) depends on the acceleration voltage and cluster size of cluster ions, but is sharper than that of monomer ions. Therefore, the thickness of the locally present region (that is, the modified layer) of the irradiated carbon is approximately 500 nm or less (for example, about 50 to 400 nm). When the constituent elements of the cluster ion 16 contain elements that contribute to gettering such as carbon, the modified layer 18 functions as a strong gettering site.

The cluster ion 16 to be irradiated in this embodiment contains carbon and hydrogen as constituent elements. The carbon atom at the lattice position has a smaller covalent bond radius than the silicon single crystal, and a contraction field of the silicon crystal lattice is formed, so that the gettering ability to attract impurities between the lattices is high. Further, as described above, hydrogen passesivates the point defects of the silicon epitaxial layer 20 and contributes to the improvement of the device characteristics when a semiconductor device is produced using the epitaxial silicon wafer 100 obtained by the present embodiment. Is.

Here, in the first step, the amount of hydrogen dose due to cluster ion irradiation is set to 2.8 × 10 ¹⁵ atoms / cm ² or more. This is to form a high hydrogen concentration region in the modified layer 18A and increase the hydrogen peak concentration in the thickness direction thereof. Further, it is also an object to maintain a high concentration of hydrogen in the reformed layer 18C even after the heat treatments of the second step and the third step after the first step. For these purposes, it is more preferable that the hydrogen dose amount is 3.3 × 10 ¹⁵ atoms / cm ^{2 or more.} Further, if the hydrogen dose amount is 5.0 × 10 ¹⁵ atoms / cm ² or less, the occurrence of epitaxial defects can be suppressed by the crystal recovery effect of the second step, and 4.2 × 10 ¹⁵ atoms / cm ² It is more reliable if the following is done.

Although the amount of carbon dose depends on the atomic ratio of the elements constituting the cluster ion 16, the amount of carbon dose should be 1.7 × 10 ¹⁵ atoms / cm ² or more in order to surely obtain the gettering effect. Is preferable. Further, it is more preferable that the amount of carbon dose is 2.0 × 10 ¹⁵ atoms / cm ^{2 or more.} Further, if the carbon dose amount is 3.0 × 10 ¹⁵ atoms / cm ² or less, the occurrence of epitaxial defects can be suppressed by the crystal recovery effect of the second step, and 2.5 × 10 ¹⁵ atoms / cm ² It is more reliable if the following is done.

<Second step>
After the first step, a second step (steps C and D in FIGS. 1) of performing a flash lamp annealing (FLA) process on the silicon wafer 10 is performed. As described above, the modified layer 18A changes to the modified layer 18B with the heat treatment of the flash lamp annealing treatment in the second step. Here, the flash lamp annealing treatment in this step is performed with a treatment time of 0.1 ms or more and 20 ms or less and a treatment temperature of 800 ° C. or higher and 1200 ° C. or lower.

Here, when performing the flash lamp annealing treatment, it is general that the preheating is first performed from the room temperature to the preheating temperature (assist heat temperature) to be lower than the treatment temperature. The assist heat temperature is not particularly limited as long as it is lower than the above processing temperature, but may be, for example, 400 ° C. to 780 ° C. Then, after the temperature inside the furnace is raised to the assist heat temperature, as a flash lamp annealing treatment, the treatment time is 0.1 ms or more and 20 ms or less, and the treatment temperature is 800 ° C. or higher and 1200 ° C. or lower for a very short time. Perform heat treatment. After the heat treatment at a high temperature for a very short time, the temperature inside the furnace is lowered to the assist heat temperature, and the preheating is stopped to lower the temperature to room temperature.

If the processing time of the flash lamp annealing treatment is too short, the injection damage formed by the cluster ion irradiation in the first step is insufficient to recover the crystals, and the occurrence of epitaxial defects cannot be suppressed. Therefore, the processing time of the flash lamp annealing process is set to 0.1 ms or more. Further, for this purpose, it is more preferable that the processing time is 1.4 milliseconds or more.

On the other hand, if the processing time of the flash lamp annealing treatment is excessive, it is sufficient to perform crystal recovery, but it is present in the modified layer 18A when the modified layer 18A is transformed into the modified layer 18B. Hydrogen diffuses and oxygen is captured too much in the modified layer 18B. Therefore, the processing time of the flash lamp annealing process is set to 20 milliseconds or less. Further, for this purpose, the processing time is more preferably 5 milliseconds or less, and further preferably 2 milliseconds or less.

Further, if the treatment temperature by the flash lamp annealing treatment is within the range of 800 ° C. or higher and 1200 ° C. or lower, the diffusion of hydrogen existing in the modified layer 18A can be suppressed, and crystal recovery can also be performed. can. In order to sufficiently recover the crystals, the treatment temperature is preferably 1000 ° C. or higher, and more preferably 1050 ° C. or higher. Further, in order to suppress hydrogen diffusion more reliably, the treatment temperature is preferably 1150 ° C. or lower, and more preferably 1100 ° C. or lower.

The atmosphere gas in the flash lamp annealing treatment is not particularly limited _{, and an inert gas atmosphere such as nitrogen gas (N 2} ) or argon gas (Ar) can be used. It is also preferable to perform flash lamp annealing treatment in an ammonia gas (NH _{3) atmosphere.} It has been experimentally confirmed that the concentration of hydrogen captured in the modified layer 18B can be increased, and from this fact, it is presumed that hydrogen can be maintained at a high concentration even after the formation of the epitaxial layer.

The apparatus for performing the flash lamp annealing treatment is not particularly limited, and a known apparatus can be used. For example, LA-3000-F, LA-3100 manufactured by SCREEN Semiconductor Solutions Co., Ltd., which is a xenon (Xe) lamp type, can be exemplified. Further, the processing temperature and processing time during the flash lamp annealing processing can be confirmed by a pyrometer or the like.

<Third step>
After the second step, a third step of forming the silicon epitaxial layer 20 on the modified layer 18B of the silicon wafer 10 is performed (step E in FIG. 1). In this way, it is possible to obtain an epitaxial silicon wafer 100 in which the modified layer 18C is provided on the surface layer portion of the silicon wafer 10 and the silicon epitaxial layer 20 is provided on the modified layer 18C.

The silicon epitaxial layer 20 can be formed under general conditions. In this case, for example, hydrogen is used as a carrier gas, and a source gas such as dichlorosilane or trichlorosilane is introduced into the chamber, and the growth temperature varies depending on the source gas used, but CVD is performed at a temperature in the range of approximately 1000 to 1200 ° C. By the method, it can be epitaxially grown on the silicon wafer 10. The thickness of the silicon epitaxial layer 20 is preferably in the range of 1 to 15 μm. If it is less than 1 μm, the resistivity of the epitaxial layer 20 may change due to the outward diffusion of the dopant from the silicon wafer 10, and if it exceeds 15 μm, the spectral sensitivity characteristics of the solid-state image sensor are affected. This is because there is a risk.

By going through each of the above steps, according to the present embodiment, an epitaxial can exhibit higher gettering ability, increase the hydrogen peak concentration in the high concentration hydrogen injection region, and suppress the occurrence of epitaxial defects. A method for manufacturing a silicon wafer can be provided. The epitaxial silicon wafer 100 provided with the modified layer 18C and the silicon epitaxial layer 20 thus formed can improve the device characteristics of the semiconductor device produced by using the epitaxial silicon wafer 100.

Hereinafter, the irradiation mode of cluster ions in this embodiment will be described.

The constituent elements of the cluster ion 16 to be irradiated are not particularly limited as long as they contain carbon and hydrogen. Examples of the constituent elements of the cluster ion 16 other than carbon and hydrogen include boron, phosphorus, arsenic, and oxygen. In particular, in addition to hydrogen and carbon, it is also preferred to irradiate with one or more dopant elements selected from the group consisting of boron, phosphorus, arsenic and antimony in the form of cluster ions. This is because the types of metals that can be efficiently gettered differ depending on the types of elements that can be solid-dissolved. Therefore, by dissolving a plurality of elements in solid solution, a wider range of metal contamination can be dealt with. For example, in the case of carbon, nickel (Ni) can be efficiently gettered, and in the case of boron, copper (Cu) and iron (Fe) can be efficiently gettered.

The compound to be ionized is not particularly limited, but ethane, methane and the like can be used as the carbon source compound capable of ionization, and diborane and decabolane (B ₁₀ H ₁₄ ) can be used as the boron source compound capable of ionization. Etc. can be used. For example, when a gas obtained by mixing dibenzyl and decaborane is used as a material gas, a hydrogen compound cluster in which carbon, boron and hydrogen are aggregated can be generated. Further, if cyclohexane (C ₆ H ₁₂ ) is used as a material gas, cluster ions composed of carbon and hydrogen can be generated. As the carbon source compound, it is particularly _{preferable to use cluster C n} H _m (3 ≦ n ≦ 16, 3 ≦ m ≦ 10) _{produced from pyrene (C 16} H ₁₀ ), dibenzyl (C ₁₄ H ₁₄ ), or the like. This is because it is easy to control a small-sized cluster ion beam.

The cluster size can be appropriately set from 2 to 100, preferably 60 or less, more preferably 50 or less. The cluster size can be adjusted by adjusting the gas pressure of the gas ejected from the nozzle, the pressure of the vacuum vessel, the voltage applied to the filament during ionization, and the like. The cluster size can be obtained by obtaining the cluster number distribution by mass spectrometry using a quadrupole high-frequency electric field or time-of-flight mass spectrometry, and taking the average value of the number of clusters.

Even after the silicon epitaxial layer 20 is formed, the beam current value of the cluster ion 16 is preferably 50 μA or more in order to further increase the peak concentration of hydrogen in the surface layer portion of the silicon wafer 10. When the cluster ion 16 containing hydrogen is irradiated under the above current value conditions, the hydrogen contained in the constituent elements of the cluster ion 16 is more reliably dissolved in the surface layer portion of the silicon wafer 10 in excess of the equilibrium concentration. In order to obtain this effect more reliably, the beam current value is more preferably 100 μA or more, and further preferably 300 μA or more. The beam current value of the cluster ion 16 can be adjusted, for example, by changing the decomposition conditions of the raw material gas in the ion source.

On the other hand, if the beam current value becomes excessive, epitaxial defects may be excessively generated in the silicon epitaxial layer 20, so that the beam current value is preferably 5000 μA or less.

The acceleration voltage of the cluster ions affects the peak position of the concentration profile in the depth direction of the constituent elements of the cluster ions together with the cluster size. In the present embodiment, the acceleration voltage of the cluster ion can be more than 0 keV / Cluster and less than 200 keV / Cluster, preferably 100 keV / Cluster or less, and more preferably 80 keV / Cluster or less. Two methods, (1) electrostatic acceleration and (2) high frequency acceleration, are generally used for adjusting the acceleration voltage. As the former method, there is a method in which a plurality of electrodes are arranged at equal intervals and an equal voltage is applied between them to create an equiaccelerating electric field in the axial direction. As the latter method, there is a linear linac method in which ions are accelerated by using high frequency while running linearly. Further, the dose amount of cluster ions can be adjusted by controlling the ion irradiation time.

Hereinafter, a preferred embodiment of the epitaxial silicon wafer manufactured by the manufacturing method according to the present embodiment will be described.

(Epitaxial silicon wafer)
FIG. 1 Step E illustrates one aspect of the epitaxial silicon wafer 100 obtained by the above manufacturing method. The epitaxial silicon wafer 100 includes a silicon wafer 10, a modified layer 18C formed on the surface layer portion of the silicon wafer 10, in which carbon and hydrogen are solidly dissolved, and a silicon epitaxial layer 20 formed on the modified layer 18C. Has. The peak oxygen concentration of the oxygen concentration profile in the thickness direction of the modified layer 18C is 5 × 10 ¹⁸ atoms / cm ³ or less, and the peak hydrogen concentration of the hydrogen concentration profile is 2 × 10 ¹⁸ atoms / cm ³ or more. Is. The epitaxial defects on the surface of the epitaxial layer 20 are 1.0 × 10 ⁻² pieces / cm ² or less. In the silicon epitaxial silicon wafer 100, the reformed layer 18C is the first to realize an epitaxial silicon wafer having a low epitaxial defect while realizing a low oxygen concentration and a high hydrogen concentration, which were difficult in the prior art.

Further, the epitaxial defect on the surface of the epitaxial layer of the epitaxial silicon wafer 100 of the present invention can be 5.0 × 10 ^-3 pieces / cm ² or less, and further, 2.0 × 10 ^-3 pieces / cm. It can be ^{2 or less.}

Further, in order to ensure the passivation effect, it is preferable that the half width (FWHM) of the hydrogen concentration profile in the thickness direction of the modified layer 18C is 150 nm or less in the epitaxial silicon wafer 100. Further, in order to enhance the gettering ability, it is preferable that the half width of the oxygen concentration profile is 150 nm or less so that oxygen precipitation is localized.

Further, in order to enhance the gettering ability, in the epitaxial silicon wafer 100, the carbon peak concentration of the carbon concentration profile in the carbon depth direction in the modified layer 18C is 1.0 × 10 ¹⁵ atoms / cm ³ or more and 1.0 ×. It is preferably 10 ²⁰ atoms / cm ³ or less, and it is also preferable that the half-value width of the peak of the carbon concentration profile in the depth direction is 100 nm or less.

Further, a carbon, hydrogen and oxygen concentration profile within a range from the surface 10A of the silicon wafer 10 (that is, the interface between the silicon wafer 10 serving as a base substrate and the silicon epitaxial layer 20) to a depth of 150 nm in the depth direction. It is preferable that each of the peaks is present. Since it is physically impossible to have the peak position of the concentration profile of each element on the outermost surface of the silicon wafer 10 irradiated with the cluster ion 16 (depth 0 nm from the surface 10A of the silicon wafer 10), it is at least 5 nm. It will exist at the above depth position.

The thickness of the modified layer 18C is defined as a region in the above concentration profile in which the carbon concentration profile contained in the constituent elements of the cluster ion 16 is locally detected in excess of the background concentration, for example, 30 to 400 nm. Can be within the range of.

It is preferable that the oxygen concentration of the silicon wafer 10 is 1.0 × 10 ¹⁷ atoms / cm ³ or more 12 × 10 ¹⁷ atoms / cm ³ or less, further, 1.0 oxygen concentration × 10 ¹⁷ atoms / cm ³ The above is preferable. The oxygen concentration referred to here refers to the oxygen concentration of the silicon wafer other than the modified layer.

Although the typical embodiments of the present invention have been described above, the present invention is not limited to these embodiments.

[Experimental Example 1]
(Conventional example 1)
Obtained from CZ single crystal silicon ingot, a silicon wafer (diameter of oxygen concentration (ASTM F 121-1979) is ^{10 × 10 17 atoms / cm 3} : 300mm, thickness: 725 .mu.m, the dopant type: boron, resistivity: 20 [Omega · cm) was prepared.

Next, using a cluster ion generator (manufactured by Nissin Ion Equipment Co., Ltd., model number: CLARIS) _{, cluster ions of C 3} H ₅ generated from cyclohexane were subjected to carbon dose amount: 2.0 × 10 ¹⁵ atoms / cm ^2. , Hydrogen dose amount: 3.3 × 10 ¹⁵ ions / cm ² , Acceleration voltage: 80keV / Cluster, Tilt: 0 °, Twist: 0 °, irradiate the surface of the silicon wafer and modify it to the surface layer of the silicon wafer. A layer was formed. Since the acceleration voltage is 80 keV / Cruster, the acceleration voltage is 1.95 keV / atom per hydrogen atom, and the acceleration voltage is 23.4 keV / atom per carbon atom. Therefore, the range of hydrogen is 40 nm, and the range of carbon is 80 nm.

Next, the silicon wafer was transferred into a single-wafer epitaxial growth apparatus (manufactured by Applied Materials), and hydrogen-baked at a temperature of 1120 ° C. for 30 seconds in the apparatus. Then, a silicon epitaxial layer having a thickness of 5.0 μm (hereinafter abbreviated as the epitaxial layer) was grown on a silicon wafer by a CVD method at 1150 ° C. using hydrogen as a carrier gas and trichlorosilane as a source gas.

(Invention Example 1)
Conventional examples except that the silicon wafer was subjected to a recovery heat treatment for a very short time using a flash lamp annealing device (LA-3000-F) manufactured by SCREEN Semiconductor Solutions after irradiation with cluster ions and before formation of the silicon epitaxial layer. An epitaxial silicon wafer according to Invention Example 1 was obtained in the same manner as in 1. The heat treatment conditions for performing the flash lamp annealing treatment were as follows.
Assist heat temperature: 400 ° C
Processing time: 1.4 ms Processing temperature: 1000 ° C
Atmospheric gas: Nitrogen (N ₂ )

(Invention Examples 2 to 4)
Except for the heat treatment conditions as shown in Table 1 below, epitaxial silicon wafers according to Invention Example 1 were obtained in the same manner as in Invention Example 1.

(Comparative Example 1)
Instead of the flash lamp annealing treatment in Example 1, a short-time recovery heat treatment was performed at 1000 ° C. for 1.0 second using an RTA apparatus (manufactured by Matson Thermal Products Co., Ltd.), and the epitaxial according to Comparative Example 1. Silicon wafers were obtained respectively.

(Evaluation method)
The following evaluations were made in each of the invention examples and comparative examples.

<Evaluation 1: Evaluation of epitaxial defects>
The surfaces of the epitaxial wafers of the samples prepared in Invention Examples 1 to 4, Conventional Example 1 and Comparative Example 1 were observed and evaluated using KLA-Tenchor Co., Ltd .: Surfscan SP-1, and the state of occurrence of LPD was investigated. At that time, the observation mode was the Oblique mode (diagonal incident mode), and the surface pits were estimated based on the detection size ratio of the Wide Now channel. Subsequently, the site where LPD was generated was observed and evaluated using a scanning electron microscope (SEM) to confirm whether or not the LPD was a stacking fault (SF). The LPD confirmed as SF was evaluated as an epitaxial defect, and the number of the LPD was defined as the number of epitaxial defects. The evaluation results are shown in Table 1.

<Evaluation 2: Hydrogen and oxygen concentration distribution (SIMS measurement)>
Regarding Examples 1 to 4, the concentration of hydrogen and oxygen in the thickness direction after the flash lamp annealing treatment is measured by secondary ion mass spectrometry (SIMS).
). As a representative example, the measurement result of Invention Example 1 is shown in FIG. Further, for Conventional Example 1, the concentration distribution after irradiation with cluster ions is shown in FIG. Further, for Comparative Example 1, the concentration distribution after the short-time heat treatment is shown in FIG. Further, after forming the epitaxial layer, the concentrations of hydrogen and oxygen in Invention Examples 1 to 4 and Comparative Example 1 were measured by secondary ion mass spectrometry. As a representative example, the measurement results of Invention Example 1 and Comparative Example 1 are shown in FIGS. 5 and 6, respectively.

Further, Table 1 shows the evaluation results of the peak concentrations of hydrogen and oxygen in the cluster ion implantation region, using Comparative Example 1 as a reference (relative value 1.0). With the epitaxial growth, the peak oxygen concentration and the peak hydrogen concentration in the modified layer of the epitaxial silicon wafer according to Comparative Example 1 can be similar to those of Invention Example 1, but Comparative Example 1 has many epitaxial defects, while Invention Example 1 has many epitaxial defects. Epitaxial defects were suppressed. Further, as shown in Table 1, in Conventional Example 1, since epitaxial defects frequently occurred, the concentration was not evaluated after the epitaxial layer was formed.

<Evaluation 3: Observation by TEM cross-sectional photograph>
With respect to Invention Example 1, Conventional Example 1 and Comparative Example 1, the cross section around the modified layer immediately before the formation of the epitaxial layer was observed with a TEM (Transmission Electron Microscope). The TEM cross-sectional view of Invention Example 1 is shown in FIG. 2, the TEM cross-sectional view of Conventional Example 1 is shown in FIG. 3, and the TEM cross-sectional view of Comparative Example 1 is shown in FIG. 4 in comparison with the concentration distribution by SIMS. In the TEM cross-sectional photograph, the position where the black contrast is seen is the region where the damage is particularly large, and the portion where the black color appears is the amorphous region. From FIG. 3, the formation of an amorphous region (a high hydrogen concentration injection region in SIMS and a white portion in the TEM cross-sectional view) by irradiation with cluster ions is confirmed. In FIG. 2, it can be read that a part of the cluster ion irradiation region is recovered by crystal, and in FIG. 4, almost all of the cluster ion irradiation region is recovered by crystallinity.

Further, with respect to Invention Example 1 and Conventional Example 1, TEM cross-sectional views after forming the epitaxial layer are shown in FIGS. 7 and 8, respectively. As shown in FIG. 8, in Conventional Example 1, two black spot-shaped defects having a major axis of about 40 nm and a minor axis of about 20 nm were formed at a depth of about 50 nm directly below the interface between the epitaxial layer and the silicon wafer. Can be confirmed. It is presumed that the generation of black spot-shaped defects is the cause of the frequent generation of epitaxial defects in Conventional Example 1. On the other hand, as shown in FIG. 7, in Invention Example 1, the black spot-like defect observed in FIG. 8 is not generated.

<Evaluation 4: Evaluation of gettering ability>
The surface of the epitaxial silicon wafer of each sample produced in Invention Examples 1 to 4 and Comparative Example 1 ^{was intentionally contaminated with Fe contaminated liquid (1 × 10 13} atoms / cm ² ) by a spin coating contamination method, and continued at 1050 ° C. Heat treatment was performed for 2 hours. Then, the concentration of Fe was measured by SIMS, and the peak concentration of Fe was measured. It can be evaluated that the higher the peak concentration of Fe, the higher the gettering ability because more Fe can be captured. Table 1 shows the evaluation results using the peak concentration of Fe in Comparative Example 1 as a reference (relative value 1.0). As shown in Table 1, in the conventional example 1, the gettering ability was not evaluated because the epitaxial defects frequently occurred.

(Discussion of evaluation results)
From Table 1 and FIGS. 2 to 4, it can be confirmed that the lower the peak oxygen concentration in the cluster ion implantation region, the higher the gettering ability. This is because a gettering site is formed in the modified layer by irradiation with cluster ions, and oxygen in the wafer is captured by this gettering site by the subsequent heat treatment (that is, the oxygen peak concentration is increased in the concentration detection by SIMS). If it is high), it is presumed that most of the gettering sites are occupied by oxygen atoms. If the oxygen atom occupies most of the gettering site, the gettering site will not be able to capture the metal and the gettering ability will be reduced. In addition, it is confirmed that the diffusion of hydrogen can be suppressed if the heat treatment has less oxygen capture. The ultra-short time heat treatment in milliseconds by the flash lamp annealing treatment has less diffusion of oxygen and hydrogen than the short-time heat treatment in seconds by RTA or the like, has a high crystal recovery effect, and has an epitaxial defect. The occurrence can be suppressed.

Further, considering the results of Invention Examples 1 to 4 shown in Table 1, since hydrogen can be maintained at the highest concentration and the gettering ability is high in Invention Example 1, the flash lamp annealing treatment can be performed. It can be confirmed that a relatively low temperature and an extremely short time are preferable. On the other hand, in order to minimize epitaxial defects, it was also confirmed that it is preferable to perform flash lamp annealing treatment at a relatively low temperature for a long time or at a relatively high temperature for a short time as in Invention Examples 2 and 3.

[Experimental Example 2]
(Invention Example 5)
Obtained from CZ single crystal silicon ingot, a silicon wafer (diameter of oxygen concentration (ASTM F 121-1979) is ^{10 × 10 17 atoms / cm 3} : 300mm, thickness: 725 .mu.m, the dopant type: boron, resistivity: 20 [Omega · cm) was prepared.

Next, using a cluster ion generator (manufactured by Nissin Ion Equipment Co., Ltd., model number: CLARIS) _{, cluster ions of C 3} H ₅ generated from cyclohexane were subjected to carbon dose amount: 3.0 × 10 ¹⁵ atoms / cm ^2. , Hydrogen dose amount: 5.0 × 10 ¹⁵ ions / cm ² , Acceleration voltage: 80 keV / Cluster, Tilt: 0 °, Twist: 0 °, irradiate the surface of the silicon wafer and modify it to the surface layer of the silicon wafer. A layer was formed. Since the acceleration voltage is 80 keV / Cruster, the acceleration voltage is 1.95 keV / atom per hydrogen atom, and the acceleration voltage is 23.4 keV / atom per carbon atom. Therefore, the range of hydrogen is 40 nm, and the range of carbon is 80 nm.

After irradiation with cluster ions and before forming the silicon epitaxial layer, the silicon wafer was subjected to a recovery heat treatment for a very short time using a flash lamp annealing device (LA-3000-F) manufactured by SCREEN Semiconductor Solutions. The heat treatment conditions for performing the flash lamp annealing treatment were as follows.
Assist heat temperature: 400 ° C
Processing time: 1.4 ms Processing temperature: 1000 ° C
Atmospheric gas: Nitrogen (N ₂ )

Then, an epitaxial layer was formed under the same conditions as in Experimental Example 1, and an epitaxial silicon wafer according to Invention Example 5 was produced.

(Invention Example 6)
When the atmospheric gas in Invention Example 5 was nitrogen, an epitaxial silicon wafer according to Invention Example 6 was produced under the same conditions as Invention Example 5 except that it was replaced _{with ammonia (NH 3).}

With respect to Invention Examples 5 and 6, the hydrogen concentration in the thickness direction after the flash lamp annealing treatment was measured by secondary ion mass spectrometry (SIMS) in the same manner as in Evaluation 2 above. The measurement results are shown in FIG.

From FIG. 9, it was confirmed that when the atmosphere gas at the time of flash lamp annealing was ammonia gas, hydrogen could be captured at a higher concentration than when it was nitrogen gas.

According to the present invention, an epitaxial silicon wafer and a method for manufacturing the same, which can suppress the occurrence of epitaxial defects while maintaining a high concentration of hydrogen in a high-concentration hydrogen injection region while exhibiting higher gettering ability. Can be provided.

10 Silicon wafer 10A Surface of silicon wafer 16 Cluster ion 18A Modified layer (after irradiation with cluster ion)
18B modified layer (after FLA treatment)
18C modified layer (after epitaxial growth)
20 Silicon epitaxial layer 100 epitaxial silicon wafer FLA flash lamp annealing treatment

Claims (8)

The first step of irradiating the surface of a silicon wafer with cluster ions containing carbon and hydrogen as constituent elements to form a modified layer in which the constituent elements of the cluster ions are solid-solved on the surface layer portion of the silicon wafer.
After the first step, a second step of performing a flash lamp annealing process on the silicon wafer and a second step.
After the second step, a third step of forming a silicon epitaxial layer on the modified layer of the silicon wafer is provided.
In the first step, the amount of hydrogen dose due to the cluster ion irradiation was set to 2.8 × 10 ¹⁵ atoms / cm ² or more.
The flash lamp annealing treatment in the second step is characterized in that the treatment time is 0.1 ms or more and 20 ms or less and the treatment temperature is 800 ° C. or higher and 1200 ° C. or lower in an ammonia gas atmosphere. Manufacturing method of silicon wafer. The method for manufacturing an epitaxial silicon wafer according to claim 1, wherein the carbon dose amount by the cluster ion irradiation is 1.7 × 10 ¹⁵ atoms / cm ^{2 or more.} The method for manufacturing an epitaxial silicon wafer according to claim 1 or 2, wherein the processing temperature of the flash lamp annealing treatment in the second step is 1000 ° C. or higher and 1150 ° C. or lower. The method for manufacturing an epitaxial silicon wafer according to any one of claims 1 to 3, wherein the processing time of the flash lamp annealing treatment in the second step is 0.1 ms or more and 5 ms or less. The method for manufacturing an epitaxial silicon wafer according to any one of claims 1 to 4, wherein the oxygen concentration of the silicon wafer is 12 × 10 ¹⁷ atoms / cm ^{3 or less.} With silicon wafers
A modified layer in which carbon and hydrogen are solid-solved formed on the surface layer of the silicon wafer, and
The silicon epitaxial layer formed on the modified layer and
Have,
The peak oxygen concentration of the oxygen concentration profile in the thickness direction of the modified layer is 5 × 10 ¹⁸ atoms / cm ³ or less (however, excluding ^{5 × 10 18} atoms / cm ³ ), and the peak of the hydrogen concentration profile. The hydrogen concentration is 2 × 10 ¹⁸ atoms / cm ³ or more,
An epitaxial silicon wafer having an epitaxial defect on the surface of the epitaxial layer of 1.0 × ^10-2 pieces / cm ^{2 or less.} The epitaxial silicon wafer according to claim 6, wherein the modified layer has a half width of the hydrogen concentration profile of 150 nm or less in the thickness direction and a half width of the oxygen concentration profile of 150 nm or less. The epitaxial silicon wafer according to claim 6 or 7, wherein the silicon wafer has an oxygen concentration of 12 × 10 ¹⁷ atoms / cm ^{3 or less.}

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