JP7059871B2 - Manufacturing method of semiconductor epitaxial wafer and manufacturing method of semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor epitaxial wafer and a method for manufacturing a semiconductor device.

Semiconductor epitaxial wafers in which an epitaxial layer is formed on a semiconductor wafer typified by a silicon wafer include MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistor), DRAMs (Dynamic Random Access Memory), power transistors, and back-illuminated solids. It is used as a device substrate for manufacturing various semiconductor devices such as an image pickup element.

For example, in a back-illuminated solid-state image sensor, by arranging a wiring layer or the like below the sensor unit, light from the outside can be directly taken into the sensor, and clearer images and moving images can be taken even in a dark place. .. Therefore, the back-illuminated solid-state image sensor has been widely used in mobile phones such as digital video cameras and smartphones in recent years.

In recent years, with the increasing miniaturization and higher performance of semiconductor devices, there is a demand for higher quality semiconductor epitaxial wafers used as device substrates in order to improve the quality of device characteristics.

Therefore, in Patent Document ₁ , the applicant of the present application irradiates the surface of the semiconductor wafer with cluster ions containing carbon and hydrogen as constituent elements such as _C3H5 ions, and after the first step. A method for manufacturing a semiconductor epitaxial wafer having a second step of forming an epitaxial layer on the surface of the semiconductor wafer and having a beam current value of the cluster ion of 50 μm or more in the first step has been proposed. The outline of the technique described in Patent Document 1 is as follows.

First, a semiconductor epitaxial wafer in which hydrogen ions are injected into a semiconductor wafer in the form of monomer ions (single atom ions) to form a hydrogen ion injection region on the surface layer portion of the semiconductor wafer, and then an epitaxial layer is formed on the surface layer portion. In, even if the hydrogen concentration profile in the depth direction in the surface layer is measured by the secondary ion mass spectrometry (SIMS), the hydrogen concentration is below the lower limit of detection and no hydrogen concentration peak is observed. .. This is because hydrogen is a light element, so that hydrogen diffuses outward due to heating during the formation of the epitaxial layer, and almost no hydrogen remains in the semiconductor wafer.

In Patent Document 1, hydrogen is injected in the form of cluster ions such as C ₃ H ₅ ions, and the beam current value is set to 50 μm or more so that the surface layer portion of the semiconductor wafer is formed even after the epitaxial layer is formed. It was possible to leave hydrogen at a high concentration, and it was possible to manufacture a semiconductor epitaxial wafer in which a peak exists in the hydrogen concentration profile in the depth direction in the surface layer portion. The hydrogen remaining on the surface layer portion of the semiconductor wafer (that is, directly under the epitaxial layer) diffuses into the epitaxial layer by the heat treatment during the device forming process for forming the semiconductor device in the epitaxial layer, and passes the defects in the epitaxial layer. Therefore, if the semiconductor epitaxial wafer of Patent Document 1 is used in the device forming process, the crystallinity of the epitaxial layer can be enhanced, and the device characteristics can be expected to be improved.

International Publication No. 2016/031328

Hydrogen remaining on the surface layer of the semiconductor wafer, which is the substrate of the semiconductor epitaxial wafer, inactivates the interface state defects in the epitaxial layer during the device formation process and contributes to the improvement of device characteristics such as reduction of leakage current. However, as a result of further studies by the present inventor, it was found that there is room for improvement in the following points in Patent Document 1. That is, in the method for manufacturing a semiconductor epitaxial wafer described in Patent Document 1, hydrogen is merely left on the surface layer portion of the semiconductor wafer after epitaxial growth by controlling the cluster ion irradiation conditions, and the hydrogen concentration in this surface layer portion is adjusted. No consideration has been given to how to enhance it. If a higher concentration of hydrogen can be captured and retained on the surface layer of the semiconductor wafer, which is the substrate of the semiconductor epitaxial wafer, the passivation effect of hydrogen in the epitaxial layer can be enhanced, and as a result, the device characteristics are further improved. It is expected that it can be done.

Therefore, in view of the above problems, the present invention uses a method for manufacturing a semiconductor epitaxial wafer and a method for manufacturing the semiconductor epitaxial wafer, which can manufacture a semiconductor epitaxial wafer having a higher passivation effect due to hydrogen in the epitaxial layer. An object of the present invention is to provide a method for manufacturing a semiconductor device.

In order to solve the above problems, the present inventor has carried out diligent research and obtained the following findings. That is, the semiconductor epitaxial wafer in which the epitaxial layer is formed after injecting cluster ions containing carbon and hydrogen into the semiconductor wafer is subjected to constant temperature heat treatment in a specific range of 500 ° C. or higher and 800 ° C. or lower in an atmosphere containing hydrogen. Therefore, it was found that a higher concentration of hydrogen can be captured and retained on the surface layer of the semiconductor wafer.

The abstract structure of the present invention completed based on the above findings is as follows.
(1) First, the surface of a semiconductor 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-dissolved on the surface layer portion of the semiconductor wafer. Process and
The second step of forming an epitaxial layer on the modified layer of the semiconductor wafer to obtain a semiconductor epitaxial wafer,
Have,
A method for manufacturing a semiconductor epitaxial wafer, which comprises performing a heat treatment for holding the semiconductor epitaxial wafer at a constant temperature of 500 ° C. or higher and 800 ° C. or lower in an atmosphere containing hydrogen after the second step.

(2) The first step is a condition in which a peak having a peak concentration of 1.0 × 10 ¹⁷ atoms / cm ³ or more is observed in the hydrogen concentration profile obtained by SIMS analysis of the surface layer portion after the second step. The method for manufacturing a semiconductor epitaxial wafer according to (1) above, which is performed below.

(3) The semiconductor epitaxial wafer according to (1) or (2) above, wherein the heat treatment is performed by taking out the semiconductor epitaxial wafer from the epitaxial growth apparatus and then putting the semiconductor epitaxial wafer into a separate heat treatment furnace. Production method.

(4) The semiconductor according to (3) above, wherein the hydrogen concentration in the atmosphere in the heat treatment furnace is 2% by volume or more and 4% by volume or less, and the holding time at a constant temperature is 10 minutes or more and 120 minutes or less. A method for manufacturing an epitaxial wafer.

(5) The method for manufacturing a semiconductor epitaxial wafer according to (1) or (2) above, wherein the heat treatment is performed in the process of lowering the temperature from the epitaxial growth temperature to the extraction temperature in the epitaxial growth apparatus performing the second step.

(6) The method for manufacturing a semiconductor epitaxial wafer according to (5) above, wherein the holding time at a constant temperature is 10 seconds or more and 300 seconds or less.

(7) The peak area, which is the integrated value of the hydrogen concentration profile obtained by SIMS analysis of the surface layer portion after the heat treatment, is 1.2 times or more the peak area before the heat treatment and after the second step. , The method for manufacturing a semiconductor epitaxial wafer according to any one of (1) to (6) above.

(8) The method for manufacturing a semiconductor epitaxial wafer according to any one of (1) to (7) above, wherein in the first step, the beam current value of the cluster ions is 50 μA or more and 5000 μA or less.

(9) The method for manufacturing a semiconductor epitaxial wafer according to any one of (1) to (8) above, wherein the semiconductor wafer is a silicon wafer.

(10) A method for manufacturing a semiconductor device, which comprises forming a semiconductor device on the epitaxial layer of the semiconductor epitaxial wafer manufactured by the manufacturing method according to any one of (1) to (9) above.

According to the method for manufacturing a semiconductor epitaxial wafer of the present invention, it is possible to manufacture a semiconductor epitaxial wafer having a higher passive effect due to hydrogen in the epitaxial layer. According to the method for manufacturing a semiconductor device of the present invention, the passivation effect of hydrogen in the epitaxial layer is sufficiently exhibited in the device forming process.

It is sectional drawing explaining the manufacturing method of the semiconductor epitaxial wafer 100 by one Embodiment of this invention. (A) is a graph showing the hydrogen concentration profile of the epitaxial silicon wafer in Experimental Example 1, and (B) is an enlarged graph thereof. (A) is a graph showing the hydrogen concentration profile of the epitaxial silicon wafer in Experimental Example 2, and (B) is an enlarged graph thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that, for convenience of explanation, FIG. 1 exaggerates the thicknesses of the modified layer 14 and the epitaxial layer 18 with respect to the semiconductor wafer 10, which is different from the actual thickness ratio.

(Manufacturing method of semiconductor epitaxial wafer)
In the method for manufacturing a semiconductor epitaxial wafer 100 according to an embodiment of the present invention, as shown in FIG. 1, the surface 10A of the semiconductor wafer 10 is irradiated with cluster ions 12 containing carbon and hydrogen as constituent elements, and the semiconductor wafer is irradiated with cluster ions 12. The first step (steps A and B in FIGS. 1) of forming the modified layer 14 in which the constituent elements of the cluster ions are solid-dissolved on the surface layer portion of the semiconductor wafer 10 and the epitaxial layer 18 on the modified layer 14 of the semiconductor wafer 10. After the second step (step C in FIG. 1) of forming the semiconductor epitaxial wafer 100 and the second step, the semiconductor epitaxial wafer 100 is kept constant at 500 ° C. or higher and 800 ° C. or lower in an atmosphere containing hydrogen. It has a step of performing a heat treatment for maintaining the temperature (step D in FIG. 1). The epitaxial layer 18 is a device layer for manufacturing a semiconductor element such as a back-illuminated solid-state image sensor.

[First step]
Examples of the semiconductor wafer 10 include a bulk single crystal wafer made of silicon and a compound semiconductor (GaAs, GaN, SiC) and having no epitaxial layer on the surface, but is generally used when manufacturing a back-illuminated solid-state image pickup device. A bulk single crystal silicon wafer is used. Further, as the semiconductor wafer 10, a single crystal silicon ingot grown by the Czochralski method (CZ method) or the floating zone melting method (FZ method) can be sliced with a wire saw or the like. Also, carbon and / or nitrogen may be added to the semiconductor wafer 10 to obtain higher gettering capability. Further, an arbitrary dopant may be added to the semiconductor wafer 10 at a predetermined concentration to form a so-called n + type or p + type, or n− type or p− type substrate.

Further, as the semiconductor wafer 10, an epitaxial wafer in which a semiconductor epitaxial layer is formed on the surface of a bulk semiconductor wafer may be used. For example, it is an epitaxial silicon wafer in which a silicon epitaxial layer is formed on the surface of a bulk single crystal silicon wafer. The silicon epitaxial layer can be formed under general conditions by the CVD method. The thickness of the epitaxial layer is preferably in the range of 0.1 to 20 μm, more preferably in the range of 0.2 to 10 μm. In this case, the semiconductor epitaxial wafer 100 has a plurality of epitaxial layers including an epitaxial layer 18 and an epitaxial layer of a semiconductor wafer (not shown).

In the first step, the surface 10A of the semiconductor wafer 10 is irradiated with cluster ions 12 containing carbon and hydrogen as constituent elements. In the present specification, "cluster ion" is 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 causing a fragment. It is obtained by 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 monoatomic ions such as carbon ions and hydrogen ions, carbon monoxide ions, and the like. It is clearly distinguished from single molecule ions. The number of constituent atoms of the cluster ion is usually about 5 to 100. As a cluster ion implanter using such a principle, for example, CLARIS (registered trademark) manufactured by Nissin Ion Equipment Co., Ltd. can be used.

When a silicon wafer as a semiconductor wafer 10 is irradiated with cluster ions 12 containing carbon and hydrogen, the irradiation energy momentarily causes the silicon to reach a high temperature of about 1350 to 1400 ° C. and melts. After that, the silicon is rapidly cooled, and carbon and hydrogen are dissolved in the vicinity of the surface in the silicon wafer. That is, the “modified layer” in the present specification means a layer in which carbon and hydrogen, which are constituent elements of the cluster ions to be irradiated, are solid-solved at the interstitial position or the substitution position of the crystal on the surface layer of the semiconductor wafer. The modified layer is then identified as a region in the carbon and hydrogen concentration profile in the depth direction of the semiconductor wafer where the concentration of at least one element is detected higher than the background, approximately 500 nm from the surface of the semiconductor wafer. It becomes the following surface layer part.

Here, the first step (cluster ion irradiation) is a hydrogen concentration profile in the thickness direction of the surface layer portion obtained by SIMS analysis of the surface layer portion (modified layer 14) after the second step (epitaxial growth) described later. , It is preferable to carry out under the condition that a peak having a peak concentration of 1.0 × 10 ¹⁷ atoms / cm ³ or more is observed.

As described above, since hydrogen ions are light elements, they tend to diffuse easily by heat treatment such as when the epitaxial layer 18 is formed, and tend to be difficult to stay in the semiconductor wafer after the epitaxial layer is formed. Therefore, as described in the background technology column, when hydrogen ions are injected into a semiconductor wafer in the form of monomer ions (monatomic ions), the hydrogen concentration in the depth direction on the surface layer of the semiconductor wafer immediately after the injection. Even if a peak concentration of about 1 × 10 ²⁰ atoms / cm ³ is obtained in the profile, the peak disappears in the hydrogen concentration profile after epitaxial growth, and the hydrogen concentration is below the lower limit of detection. In the current SIMS detection technique, the lower limit of hydrogen concentration detection is 7.0 × 10 ¹⁶ atoms / cm ³ .

On the other hand, in the present embodiment, by irradiating the semiconductor wafer with hydrogen in the form of cluster ions, a large amount of defects (damage) can be formed on the surface layer portion of the semiconductor wafer. Further, it is preferable to set the beam current value of the cluster ion 12 to 50 μA or more and irradiate the surface 10A of the semiconductor wafer 10 with hydrogen ions in a relatively short time to increase the damage to the surface layer portion. When the beam current value is 50 μA or more, the damage becomes large, and even after the subsequent formation of the epitaxial layer 18, hydrogen tends to remain in a high concentration on the surface layer portion on the epitaxial layer 18 side of the semiconductor wafer 10. For this purpose, the beam current value of the cluster ion 12 is preferably 100 μA or more, and more preferably 300 μA or more.

By doing so, although a large amount of hydrogen is diffused outward by the heat treatment during the epitaxial growth, the hydrogen captured by the defects in the surface layer portion remains in the surface layer portion even after the epitaxial growth. As a result, when hydrogen was injected to a peak concentration of about 1 × 10 ²⁰ atoms / cm ³ immediately after irradiation with cluster ions, the hydrogen concentration profile after epitaxial growth was also 1.0 × 10 ¹⁷ atoms / cm. A peak with a peak concentration of cm ³ or more, more specifically around 1 × 10 ¹⁸ atoms / cm ³ , is detected. The hydrogen remaining in the modified layer is diffused into the epitaxial layer by the heat treatment in the subsequent device forming process to passivate the defects in the epitaxial layer.

On the other hand, if the beam current value becomes excessive, epitaxial defects may be excessively generated in the epitaxial layer 18, so that the beam current value is preferably 5000 μA or less. The beam current value of the cluster ion 12 can be adjusted, for example, by changing the decomposition conditions of the raw material gas in the ion source.

Examples of the irradiation conditions of the cluster ions other than the beam current value include the constituent elements of the cluster ions, the dose amount of the cluster ions, the cluster size, the acceleration voltage of the cluster ions, and the like.

In this embodiment, the constituent elements of the cluster ion are carbon and hydrogen. Since the carbon atom at the lattice position has a smaller covalent bond radius than the silicon single crystal, a contraction field of the silicon crystal lattice is formed, and it becomes a gettering site that attracts impurities between the lattices. Therefore, in the present embodiment, in the modified layer 14, in addition to the passivation effect by hydrogen, the gettering effect of the impurity element by the region where carbon is solid-solved can be obtained.

Further, it is also preferable that the constituent elements of the cluster ions include elements other than hydrogen and carbon. In particular, in addition to hydrogen and carbon, it is preferred to irradiate with one or more dopant elements selected from the group consisting of boron, phosphorus, arsenic and antimony. 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 gaseous molecule used as a raw material for cluster ions is not particularly limited as long as it can obtain cluster ions having a desired cluster size. For example, if cyclohexane (C ₆ H ₁₂ ) is used as a raw material gas, cluster ions composed of carbon and hydrogen can be generated. Further, 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 ) and 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, and more preferably 50 or less. As used herein, the term "cluster size" means the number of atoms constituting one cluster. In the experimental example described later, C ₃ H ₅ having a cluster size of 8 was used. 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.

The dose amount of cluster ions can be adjusted by controlling the ion irradiation time. The dose amount of each element constituting the cluster ion is determined by the cluster ion species and the dose amount of the cluster ion (Cluster / cm ² ). In the present embodiment, the dose amount of hydrogen is preferably 1 × 10 ¹³ to 1 × 10 ¹⁶ atoms / cm ² , and more preferably 5 × 10 ¹³ so that hydrogen remains in a high concentration even after the second step. Atoms / cm ² or more. If it is less than 1 × 10 ¹³ atoms / cm ² , hydrogen may diffuse during the formation of the epitaxial layer, and if it exceeds 1 × 10 ¹⁶ atoms / cm ² , the surface of the epitaxial layer 18 may be seriously damaged. Because there is.

The amount of carbon dose is preferably 1 × 10 ¹³ to 1 × 10 ¹⁷ atoms / cm ² , more preferably 5 × 10 ¹³ atoms / cm ² or more and 5 × 10 ¹⁶ atoms / cm ² or less. If the carbon dose amount is less than 1 × 10 ¹³ atoms / cm ² , sufficient gettering capacity may not be obtained, and if the carbon dose amount exceeds 1 × 10 ¹⁶ atoms / cm ² , the semiconductor wafer 10 The damage given to the surface 10A of the surface 10A is large, and a large number of defects may be formed on the surface of the epitaxial layer 18 after the second step.

The acceleration voltage of the cluster ions, along with the cluster size, affects the peak position of the concentration profile in the depth direction of the constituent elements in the modified layer. 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 a high frequency while running linearly.

[Second step]
Examples of the epitaxial layer 18 formed on the modified layer 14 include a silicon epitaxial layer, which can be formed under general conditions. First, the semiconductor wafer is put into the epitaxial growth device and hydrogen-baked. The general condition of hydrogen baking treatment is that the inside of the epitaxial growth device is set to a hydrogen atmosphere, the semiconductor wafer is put into the furnace at a furnace temperature of 600 ° C. or higher and 900 ° C. or lower, and the temperature rises from 1 ° C./sec to 15 ° C./sec. The temperature is raised to a temperature range of 1100 ° C. or higher and 1200 ° C. or lower at a temperature rate, and the temperature is maintained for 30 seconds or longer and 1 minute or lower. This hydrogen baking treatment is to remove the natural oxide film formed on the wafer surface before the epitaxial layer grows. Subsequently, for example, hydrogen is used as a carrier gas, and a source gas such as dichlorosilane or trichlorosilane is introduced into the chamber. The growth temperature varies depending on the source gas used, but the CVD method is performed at a temperature in the range of approximately 1000 to 1200 ° C. Allows the epitaxial layer to grow on the semiconductor wafer. The thickness of the epitaxial layer 18 is preferably in the range of 1 to 15 μm. If the thickness is less than 1 μm, the resistivity of the epitaxial layer 18 may change due to the outward diffusion of the dopant from the semiconductor wafer 10, and if it exceeds 15 μm, the spectral sensitivity characteristics of the solid-state image sensor may change. This is because there is a risk of impact.

It is also preferable to perform a recovery heat treatment on the semiconductor wafer 10 for crystallinity recovery after the first step and prior to the second step. As the recovery heat treatment in this case, the semiconductor wafer 10 may be held at a temperature of 900 ° C. or higher and 1100 ° C. or lower for 10 minutes or longer and 60 minutes or lower in an atmosphere such as nitrogen gas or argon gas. In addition, recovery heat treatment can also be performed using a rapid elevating heat treatment device separate from the epitaxial device, such as RTA (Rapid Thermal Annealing) and RTO (Rapid Thermal Oxidation).

[Hydrogen atmosphere heat treatment process]
In the present embodiment, after the second step, it is important to perform a heat treatment for holding the semiconductor epitaxial wafer 100 at a constant temperature of 500 ° C. or higher and 800 ° C. or lower in an atmosphere containing hydrogen. As a result, a higher concentration of hydrogen can be captured and retained on the surface layer portion (modified layer 14) of the semiconductor wafer, and the passivation effect of hydrogen in the epitaxial layer can be further enhanced.

When the holding temperature is less than 500 ° C., the effect of incorporating hydrogen into the reformed layer 14 cannot be sufficiently obtained, and the passivation effect of hydrogen in the epitaxial layer cannot be enhanced. Therefore, the holding temperature is 500 ° C. or higher, preferably 600 ° C. or higher.

When the holding temperature exceeds 800 ° C., the amount of hydrogen already desorbed from the reformed layer 14 is larger than the amount of hydrogen taken into the reformed layer 14, so that the passivation effect of hydrogen in the epitaxial layer is rather lowered. Therefore, the holding temperature is 800 ° C. or lower, preferably 700 ° C. or lower.

The specific method for carrying out the hydrogen atmosphere heat treatment step is not particularly limited, and examples thereof include the following two methods.

[[First heat treatment method]]
As a first method, the heat treatment can be performed by taking out the semiconductor epitaxial wafer 100 from the epitaxial growth apparatus and then putting the semiconductor epitaxial wafer 100 into a separate heat treatment furnace. The heat treatment furnace is not particularly limited, and for example, a rapid elevating heat treatment device such as RTA or a resistance heating type heat treatment furnace can be used. The hydrogen concentration in the atmosphere in the heat treatment furnace in the heat treatment furnace is usually 2% by volume or more and 4% by volume or less. The rest of the atmosphere other than hydrogen is an inert gas consisting of one or more of nitrogen, argon and the like.

In this case, the holding time at a constant temperature is preferably 10 minutes or more and 120 minutes or less. By setting the holding time to 10 minutes or more, the effect of incorporating hydrogen into the modified layer 14 can be more sufficiently obtained, and the passivation effect of hydrogen in the epitaxial layer can be further enhanced. A more preferable holding time is 15 minutes or more. Even if the holding time exceeds 120 minutes, the effect of incorporating hydrogen into the modified layer 14 is saturated. Therefore, the holding time is preferably 120 minutes or less in consideration of productivity.

In the case of the first method, specifically, the heat treatment furnace is first heated to the above-mentioned constant temperature under an inert gas atmosphere consisting of one or more of nitrogen and argon, and then the semiconductor epitaxial wafer is placed in the heat treatment furnace. Add 100. After that, hydrogen having a predetermined concentration is supplied into the heat treatment furnace to maintain the heat treatment for a predetermined time. Then, hydrogen is exhausted, the inside of the heat treatment furnace is ventilated to the inert gas atmosphere, and then the semiconductor epitaxial wafer 100 is taken out from the heat treatment furnace.

[[Second heat treatment method]]
As a second method, the heat treatment can be performed in the process of lowering the temperature from the epitaxial growth temperature to the extraction temperature in the epitaxial growth apparatus performing the second step. That is, the semiconductor epitaxial wafer 100 is subsequently cooled in the epitaxial growth apparatus to a take-out temperature of generally about 600 to 700 ° C. after epitaxial growth at an epitaxial growth temperature in the range of 1000 to 1200 ° C. At that time, the inside of the epitaxial growth device has an atmosphere of 100% by volume of hydrogen. A typical temperature drop rate is 3-5 ° C / sec. Therefore, in the process of lowering the temperature of the semiconductor epitaxial wafer in the epitaxial growth device, the constant temperature can be maintained at 500 ° C. or higher and 800 ° C. or lower according to the present embodiment.

When the constant temperature during the heat treatment was set to a temperature lower than the general take-out temperature (for example, 500 ° C.), the temperature of the semiconductor epitaxial wafer was lowered to the above-mentioned constant temperature and held at the constant temperature. After that, the semiconductor epitaxial wafer 100 may be taken out from the epitaxial growth apparatus at the constant temperature.

In this case, the holding time at a constant temperature is preferably 10 seconds or more and 300 seconds or less. By setting the holding time to 10 seconds or more, the effect of incorporating hydrogen into the modified layer 14 can be more sufficiently obtained, and the passivation effect of hydrogen in the epitaxial layer can be further enhanced. A more preferable holding time is 20 seconds or more. Even if the holding time exceeds 300 seconds, the effect of incorporating hydrogen into the modified layer 14 is saturated. Therefore, the holding time is preferably 300 seconds or less in consideration of productivity.

[Increase in hydrogen concentration]
In the heat treatment of the present embodiment, the peak area (HA), which is the integrated value of the hydrogen concentration profile obtained by SIMS analysis of the surface layer portion after the heat treatment, is the peak area ( _{H B )} before the heat treatment and after the second step. It is preferable to carry out the process so as to be 1.2 times or more. When _HA / H _B is 1.2 or more, the passivation effect of hydrogen in the epitaxial layer can be further enhanced. Since the larger the _HA / _HB , the more preferable it is, the upper limit is not particularly limited, but in the present embodiment, it is generally 2.0 or less.

(Manufacturing method of semiconductor device)
The method for manufacturing a semiconductor device according to an embodiment of the present invention is characterized in that the semiconductor device is formed on an epitaxial layer 18 located on the surface of the semiconductor epitaxial wafer 100 manufactured by the above manufacturing method. According to this manufacturing method, the passivation effect of hydrogen in the epitaxial layer is sufficiently exhibited in the device forming process.

The semiconductor device formed on the epitaxial layer 18 is not particularly limited, and examples thereof include MOSFETs, DRAMs, power transistors, back-illuminated solid-state image pickup devices, and the like.

(Experimental Example 1)
An n-type silicon wafer (diameter: 300 mm, thickness: 775 μm, dopant type: phosphorus, resistivity: 20 Ω · cm) obtained from a CZ single crystal silicon ingot was prepared. Next, using a cluster ion generator (CLARIS (registered trademark) manufactured by Nissin Ion Equipment Co., Ltd.), C ₃ H ₅ cluster ions are generated and extracted using cyclohexane (C ₆ H ₁₂ ) as a raw material gas, and accelerated. The surface of the silicon wafer was irradiated under irradiation conditions of a voltage of 80 keV / Cluster (acceleration voltage 2.05 keV / atom per hydrogen atom, acceleration voltage 23.4 keV / atom per carbon atom). The dose amount when irradiated with cluster ions was 3.33 × 10 ¹⁴ cluster / cm ² . When converted to the number of hydrogen atoms, it is 1.66 × 10 ¹⁵ atoms / cm ² , and when converted to the number of carbon atoms, it is 1.0 × 10 ¹⁵ atoms / cm ² . The beam current value of the cluster ions was set to 550 μA.

Next, the silicon wafer after cluster ion irradiation is transferred into a single-wafer epitaxial growth apparatus (manufactured by Applied Materials), subjected to hydrogen baking treatment at a temperature of 1120 ° C. for 30 seconds, and then hydrogen is used as a carrier gas. , Trichlorosilane as a source gas, silicon epitaxial layer (thickness: 4.8 μm, dopant type: phosphorus, resistance: 10 Ω) on the surface on the side where the modified layer of the silicon wafer was formed by the CVD method at 1120 ° C. -Cm) was epitaxially grown to obtain an epitaxial silicon wafer. After the epitaxial growth, the epitaxial silicon wafer was cooled to about 700 ° C. at a temperature lowering rate of 5 ° C./sec with an atmosphere of 100% by volume of hydrogen in the epitaxial growth device, and then taken out from the epitaxial growth device.

Next, an RTA heat treatment was performed on the epitaxial silicon wafer in an atmosphere consisting of 3% by volume of hydrogen and 97% by volume of nitrogen, in which the epitaxial silicon wafer was held at a predetermined temperature for 30 minutes. The predetermined temperature is set to 5 levels of 500 ° C (invention example), 600 ° C (invention example), 700 ° C (invention example), 800 ° C (invention example), and 900 ° C (comparative example), and the heat treatment is not performed. (Comparative example) was used as a reference.

[Hydrogen concentration profile evaluation by SIMS]
For the epitaxial silicon wafer obtained under the above manufacturing conditions, the carbon and hydrogen concentration profiles in the depth direction from the surface of the silicon epitaxial layer were measured by SIMS measurement. As a result, the modified layer was identified at the surface layer portion of the silicon wafer of 250 nm (that is, 250 nm from the interface of the silicon epitaxial layer / silicon wafer).

2 (A) and 2 (B) show the obtained hydrogen concentration profile. Table 1 shows the peak area obtained from the hydrogen concentration profile and the rate of increase in the peak area based on the case where no heat treatment is performed (comparative example). As is clear from FIGS. 2 (A) and 2 (B) and Table 1, when the heat treatment temperatures are set to 500 ° C., 600 ° C., 700 ° C., and 800 ° C., the peak area is compared with the case where the heat treatment is not performed. However, when the heat treatment temperature was 900 ° C., the peak area decreased as compared with the case where the heat treatment was not performed.

(Experimental Example 2)
An n-type silicon wafer (diameter: 300 mm, thickness: 775 μm, dopant type: phosphorus, resistivity: 20 Ω · cm) obtained from a CZ single crystal silicon ingot was prepared. Next, using a cluster ion generator (CLARIS (registered trademark) manufactured by Nissin Ion Equipment Co., Ltd.), C ₃ H ₅ cluster ions are generated and extracted using cyclohexane (C ₆ H ₁₂ ) as a raw material gas, and accelerated. The surface of the silicon wafer was irradiated under irradiation conditions of a voltage of 80 keV / Cluster (acceleration voltage 2.05 keV / atom per hydrogen atom, acceleration voltage 23.4 keV / atom per carbon atom). The dose amount when irradiated with cluster ions was 3.33 × 10 ¹⁴ cluster / cm ² . When converted to the number of hydrogen atoms, it is 1.66 × 10 ¹⁵ atoms / cm ² , and when converted to the number of carbon atoms, it is 1.0 × 10 ¹⁵ atoms / cm ² . The beam current value of the cluster ions was set to 550 μA.

Next, the silicon wafer after cluster ion irradiation is transferred into a single-wafer epitaxial growth apparatus (manufactured by Applied Materials), subjected to hydrogen baking treatment at a temperature of 1120 ° C. for 30 seconds, and then hydrogen is used as a carrier gas. , Trichlorosilane as a source gas, silicon epitaxial layer (thickness: 4.8 μm, dopant type: phosphorus, resistance: 10 Ω) on the surface on the side where the modified layer of the silicon wafer was formed by the CVD method at 1120 ° C. -Cm) was epitaxially grown to obtain an epitaxial silicon wafer.

After the epitaxial growth, the epitaxial silicon wafer was cooled to a predetermined take-out temperature at a temperature lowering rate of 5 ° C./sec with an atmosphere of 100% by volume of hydrogen in the epitaxial growth device, and then taken out from the epitaxial growth device. At that time, in the cooling process, the epitaxial silicon wafer was heat-treated to be held at a predetermined temperature for 30 seconds. The predetermined temperature is set to 5 levels of 500 ° C (invention example), 600 ° C (invention example), 700 ° C (invention example), 800 ° C (invention example), and 900 ° C (comparative example), and the heat treatment is not performed. (Comparative example) was used as a reference. When the predetermined temperature was 700 ° C. or lower, the predetermined temperature was set to the above-mentioned take-out temperature, and when the predetermined temperature was 800 ° C. or higher, the above-mentioned take-out temperature was set to 700 ° C.

[Hydrogen concentration profile evaluation by SIMS]
For the epitaxial silicon wafer obtained under the above manufacturing conditions, the carbon and hydrogen concentration profiles in the depth direction from the surface of the silicon epitaxial layer were measured by SIMS measurement. As a result, the modified layer was identified at the surface layer portion of the silicon wafer of 250 nm (that is, 250 nm from the interface of the silicon epitaxial layer / silicon wafer).

3 (A) and 3 (B) show the obtained hydrogen concentration profile. Table 2 shows the peak area obtained from the hydrogen concentration profile and the rate of increase in the peak area based on the case where no heat treatment is performed (comparative example). As is clear from FIGS. 3 (A) and 3 (B) and Table 2, when the heat treatment temperatures are set to 500 ° C., 600 ° C., 700 ° C., and 800 ° C., the peak area is compared with the case where the heat treatment is not performed. However, when the heat treatment temperature was 900 ° C., the peak area decreased as compared with the case where the heat treatment was not performed.

According to the method for manufacturing a semiconductor epitaxial wafer of the present invention, it is possible to manufacture a semiconductor epitaxial wafer having a higher passive effect due to hydrogen in the epitaxial layer.

100 Semiconductor epitaxial wafer 10 Semiconductor wafer 10A Surface of semiconductor wafer 12 Cluster ion 14 Modified layer (surface layer part)
18 Epitaxy layer

Claims (7)

The first step of irradiating the surface of a semiconductor 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-dissolved on the surface layer portion of the semiconductor wafer.
The second step of forming an epitaxial layer on the modified layer of the semiconductor wafer to obtain a semiconductor epitaxial wafer,
Have,
The first step is performed under the condition that a peak having a peak concentration of 1.0 × 10 ¹⁷ atoms / cm ³ or more is observed in the hydrogen concentration profile obtained by SIMS analysis of the surface layer portion after the second step. ,
After the second step, the semiconductor epitaxial wafer is heat-treated to maintain the semiconductor epitaxial wafer at a constant temperature of 500 ° C. or higher and 800 ° C. or lower in an atmosphere containing hydrogen .
The heat treatment is performed by (I) taking out the semiconductor epitaxial wafer from the epitaxial growth apparatus and then putting the semiconductor epitaxial wafer into a separate heat treatment furnace. At that time, the hydrogen concentration in the atmosphere in the heat treatment furnace is 2. By volume% or more and 4% by volume or less, the balance in the atmosphere other than hydrogen is an inert gas composed of one or more of nitrogen and argon, or (II) in the epitaxial growth apparatus performing the second step. A method for manufacturing a semiconductor epitaxial wafer , which is carried out in the process of lowering the temperature from the epitaxial growth temperature to the extraction temperature, wherein the inside of the epitaxial growth apparatus has an atmosphere of 100% by volume of hydrogen . The method for manufacturing a semiconductor epitaxial wafer according to claim 1 , wherein in (I), the holding time at a constant temperature is 10 minutes or more and 120 minutes or less. The method for manufacturing a semiconductor epitaxial wafer according to claim 1 , wherein in (II), the holding time at a constant temperature is 10 seconds or more and 300 seconds or less. The claim that the peak area which is an integrated value of the hydrogen concentration profile obtained by SIMS analysis of the surface layer portion after the heat treatment is 1.2 times or more the peak area before the heat treatment and after the second step. The method for manufacturing a semiconductor epitaxial wafer according to any one of 1 to 3 . The method for manufacturing a semiconductor epitaxial wafer according to any one of claims 1 to 4 , wherein in the first step, the beam current value of the cluster ions is 50 μA or more and 5000 μA or less. The method for manufacturing a semiconductor epitaxial wafer according to any one of claims 1 to 5 , wherein the semiconductor wafer is a silicon wafer. A method for manufacturing a semiconductor device, which comprises forming a semiconductor device on the epitaxial layer of the semiconductor epitaxial wafer manufactured by the manufacturing method according to any one of claims 1 to 6 .

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