JP4779519B2 - Epitaxial wafer manufacturing method - Google Patents

Description

The present invention relates to a manufacturing method of an epitaxial-way Ha and a silicon substrate and an epitaxial layer deposited on the surface of the silicon substrate.

Conventionally, a silicon substrate manufactured by processing a silicon single crystal pulled and grown by the CZ (Czochralski) method contains a large amount of oxygen impurities, which oxygen precipitates cause dislocations and defects. (BMD: Bulk Micro Defect). When this oxygen precipitate is present on the surface where the device is formed, it causes a leakage current increase, an oxide film breakdown voltage decrease, and the like, which greatly affects the characteristics of the semiconductor device.
For this reason, conventionally, a rapid heating / quenching heat treatment (RTA) for a short time at a high temperature of 1250 ° C. or higher is applied to the silicon substrate surface in a predetermined atmosphere gas, and excess vacancies are buried inside. Then, a method of uniformly forming a DZ (Denuded Zone) layer (defect-free layer) by diffusing vacancies on the surface in the subsequent heat treatment is used. Then, after the formation of the DZ layer, a process of forming a BMD layer having a gettering effect by forming and stabilizing an oxygen precipitation nucleus as an internal defect layer by performing heat treatment at a temperature lower than the above temperature is employed.

On the other hand, in recent years, an epitaxial wafer is known in which a silicon single crystal epitaxial layer is epitaxially grown on the surface of a silicon substrate. In this epitaxial wafer, high temperature treatment is performed to remove the oxide film on the surface by heat treatment in a hydrogen atmosphere before epitaxial growth, and since the hydrogen atmosphere is usually also in the epitaxial process, interstitial silicon implantation that eliminates vacancy defects is performed. As a result, oxygen precipitation nuclei disappeared from the surface of the silicon substrate, and BMD was less likely to be formed.
In order to solve this problem, it has been proposed to heat-treat an epitaxial wafer obtained by epitaxially growing a silicon single crystal on the surface of a silicon substrate in an atmosphere gas containing a nitriding gas (see, for example, Patent Document 1). In this method, in the step of heat-treating the epitaxial wafer in the atmospheric gas, the atmospheric gas contains a nitriding gas. It is said that it is possible to obtain oxygen precipitation nuclei sufficient to cause a gettering effect in the vicinity of the surface by injecting vacancies from the inside.
Japanese Patent Laying-Open No. 2003-77924 (Specification [0009], FIG. 1)

However, since an epitaxial layer made of a silicon single crystal has already been formed on the surface of a silicon substrate, there has been a problem that further heat treatment of the epitaxial wafer increases the number of work steps.
Also, even if the epitaxial wafer is heat-treated in an atmospheric gas containing a nitriding gas and the vacancies that promote the precipitation deeply penetrate into the epitaxial layer, the oxygen precipitation having a gettering effect at a position away from the surface. It was difficult to produce nuclei.
An object of the present invention, without increasing the number of operation steps is to provide a method for manufacturing an epitaxial-way Ha therein away from the surface of the epitaxial layer may cause a gettering effect.

According to 請 Motomeko 1 invention, as shown in FIG. 2, an epitaxial wafer for forming the epitaxial layer 13 on the surface of the reaction the silicon substrate 12 disposed in the container 20 by flowing a raw material gas into the reaction vessel 20 This is an improvement of the manufacturing method.
Its distinctive point, the epitaxial layer 13 is a silicon epitaxial layer 13, a silicon internal and 1μm or more from the surface of the epitaxial layer 13 by flowing a nitrogen-containing gas to the initial distribution of the raw material gas substrate 12 and the silicon epitaxial layer 13 of the region to the interface is contained nitrogen, nitrogen is characterized that you nitrogen concentration ^{1 × 10 13 ~1 × 10 16} atoms / cm 3 in the region that is contained.
Conventional epitaxial growth uses hydrogen as a carrier gas and introduces a silicon-based gas into the reaction chamber to grow silicon on the substrate. Other epitaxial gases that are introduced into the reaction chamber during epitaxial growth have a specific resistance. It was only a dopant for control. However, in the method for manufacturing an epitaxial wafer according to the claim 1, since the inclusion of nitrogen in the portion of the thickness direction of the epitaxial layer 13 by flowing a nitrogen-containing gas to one period of flow of the material gas, nitrogen Nitrogen can be introduced into an arbitrary partial region in the thickness direction of the epitaxial layer 13 during the growth of the epitaxial layer 13 while controlling the amount and the timing of the introduction. As a result, a region having a partial gettering effect can be introduced into the epitaxial layer 13 with accuracy and accuracy in a later step and relatively easily, rather than doping the silicon substrate 12 with nitrogen.
Then, by flowing a nitrogen-containing gas to the initial distribution of the raw material gas, it is possible to introduce nitrogen into the epitaxial layer 13 near the interface of the silicon substrate 12 and the epitaxial layer 13, without increasing the number of operation steps, an epitaxial A gettering effect can be produced in the inside of the layer 13 away from the surface , that is, in the region from the surface to the inside of 1 μm or more and to the interface between the silicon substrate 12 and the silicon epitaxial layer 13 . By containing nitrogen in this region, oxygen diffusion from the silicon substrate 12 can be expected, defect induction between the epitaxial layer 13 and the silicon substrate 12 is also promoted, and gettering is performed in the interior away from the surface of the epitaxial layer 13. An effect can be produced.
In addition, by setting the nitrogen concentration in the above range, a region having a gettering effect with high metal impurity surface cleanliness can be formed in the region of the epitaxial layer 13 containing nitrogen.

The epitaxial wafer manufacturing method of the present invention, since the inclusion of nitrogen in the portion of the thickness direction of the epitaxial layer by flowing a nitrogen-containing gas to one period of flow of the raw material gas, control the introduction amount and timing of nitrogen However, during the growth of the epitaxial layer, nitrogen can be introduced into the entire region of the epitaxial layer or an arbitrary partial region in the thickness direction. As a result, a layer having a partial gettering effect can be introduced into the epitaxial layer with high accuracy and accuracy in a later process and relatively easily, rather than doping the silicon substrate with nitrogen. By the early during distribution the one time of the flow of feed gas, it is possible to relatively easily introduce nitrogen into the epitaxial layer near the interface of the silicon substrate and the epitaxial layer, without increasing the number of operation steps, A gettering effect can be produced in the interior away from the surface of the epitaxial layer . Further, by setting the concentration of nitrogen contained in the epitaxial layer to 1 × 10 ¹³ to 1 × 10 ¹⁶ atoms / cm ³ , the gettering effect with high metal impurity surface cleanliness in the region of the epitaxial layer containing nitrogen is obtained. A layer having can be formed. In addition, by making the region containing nitrogen the above region, oxygen diffusion from the silicon substrate can be expected although it depends on the heat treatment conditions, and the induction of defects between the epitaxial layer and the silicon substrate is promoted, and the surface of the epitaxial layer is increased. A gettering effect can be produced in the interior away from the center.

Next, the best mode for carrying out the present invention will be described with reference to the drawings.
As shown in FIG. 1, an epitaxial wafer 11 produced by the present invention includes a silicon substrate 12 and the epitaxial layer 13 formed on a surface of the sheet Rico emission substrate 12. The epitaxial wafer 11 is produced by forming an epitaxial layer 13 on the surface of the silicon substrate 12 disposed in the reaction vessel 20 in which the raw material gas is circulated in the reaction vessel 20 as shown in FIG. .

  FIG. 2 shows an apparatus for manufacturing a single wafer type epitaxial wafer. The reaction vessel 20 in this apparatus is composed of an upper dome 21 and a lower dome 22, and a support member 24 for supporting a single silicon substrate 12 for epitaxial growth is provided inside the reaction vessel 20. The reaction vessel 20 is provided with a gas supply port 26 and a gas discharge port 27 that communicate with the inside of the upper dome 21. One end of a gas introduction pipe 28 for supplying a source gas or a dope gas is connected to the gas supply port 26, and a gas discharge pipe 25 is connected to the gas discharge port 27. The gas inlet tube 28 and the gas outlet 27 are made of a hydrochloric acid resistant alloy such as Hastelloy.

In this apparatus, although not shown, the source gas is introduced together with the carrier gas into the reaction vessel 20 through the gas introduction pipe 28 and the gas supply port 26 while heating the silicon substrate 12 with a heat source provided outside the domes 21 and 22. To do. Here, examples of the source gas include SiH ₂ Cl ₂ , SiHCl ₃ , SiH _{4, and} SiCl _{4, and} H ₂ is mainly used as the carrier gas. The introduced source gas or the like flows through the space between the upper dome 21 and the silicon substrate 12, and after forming the epitaxial layer 13 (FIG. 1) made of a silicon single crystal thin film on the surface of the silicon substrate 12, the gas outlet 27 is opened. It is discharged from the gas discharge pipe 25 through.

Then, that certain features of the production method of the present invention, the nitrogen contained in the initial to Ru was circulated them to the reaction vessel 20 by introducing the raw material gas together with the carrier gas into the reaction vessel 20 through the gas introduction pipe 28 and the gas supply port 26 It's where gas flows. When forming the epitaxial layer 13, if a nitrogen-containing gas is allowed to flow into the reaction vessel 20, nitrogen is contained in the entire epitaxial layer 13 or a part in the thickness direction. That is, when a nitrogen-containing gas is allowed to flow along with the source gas over the entire period in which the source gas is circulated through the reaction vessel 20, nitrogen is contained in the entire region of the epitaxial layer 13 as shown in FIG. When a nitrogen-containing gas is allowed to flow through the container 20 at a time, nitrogen is contained in a partial region in the thickness direction of the epitaxial layer 13 as shown in FIGS. Here, as the nitrogen-containing gas, nitrogen gas (N ₂ ) diluted with a carrier gas (H ₂ ) in a cylinder is used.

  As described above, in the epitaxial wafer 11 in which nitrogen is contained in the entire region of the epitaxial layer 13 or a part of the region except the surface in the thickness direction, the epitaxial layer 13 can intentionally contain nitrogen. Thus, micro defects are induced thereby, and a region having a gettering effect can be formed in the entire region of the epitaxial layer 13 containing nitrogen or a part of the region excluding the surface in the thickness direction.

Here, FIG. 1 shows an epitaxial wafer 11 in which part of the flow of the source gas is the initial stage of the flow, and a partial region in the thickness direction of the epitaxial layer 13 is in the vicinity of the interface between the silicon substrate 12 and the epitaxial layer 13. Indicates. In this case, although depending on the post-epitaxial heat treatment conditions, a partial region in the thickness direction of the epitaxial layer 13 is 1 μm or more from the surface of the epitaxial layer 13 to the interface between the silicon substrate 12 and the epitaxial layer 13. area Ru der. Specifically, the partial region in the thickness direction of the epitaxial layer 13 is preferably a region having a thickness of 0 to 20 μm from the interface between the silicon substrate 12 and the epitaxial layer 13.

  On the other hand, the standard thickness of the epitaxial layer 13 in the general epitaxial wafer 11 is 1 to 10 [mu] m for a thin one and 100 to 150 [mu] m for a thick one. Therefore, a region within 1 μm or more from the surface of the epitaxial layer 13 to the interface between the silicon substrate 12 and the epitaxial layer 13, or a region having a thickness of 0 to 20 μm of the epitaxial layer 13 from the interface between the silicon substrate 12 and the epitaxial layer 13. Putting nitrogen into the tank means flowing the nitrogen-containing gas during 90 to 10% in the initial stage of the entire period in which the raw material gas is circulated. When nitrogen is introduced into a region having a thickness of 0 to 20 μm from the interface between the epitaxial layer 13 and the silicon substrate 12 in this way, oxygen diffusion from the silicon substrate 12 can be expected, and between the epitaxial layer 13 and the silicon substrate 12 can be expected. It seems that defect induction is also promoted. That is, when nitrogen is introduced into the interface between the silicon substrate 12 and the epitaxial layer 13, it is considered that it is easily deposited by interstitial oxygen nitrogen due to oxygen diffusion in the silicon substrate 12. As a result, a gettering effect can be produced in the interior away from the surface of the epitaxial layer 13 without increasing the number of work steps, and a gettering effect similar to that obtained by doping the silicon substrate 12 with nitrogen can be obtained.

Further, it the nitrogen concentration in the region where the nitrogen of the epitaxial layer 13 is contained in Ri ^{1 × 10 13 ~1 × 10 16} atoms / cm 3 der, is ^{1 × 10 15 ~1 × 10 16} atoms / cm 3 good Masui. If the nitrogen concentration is within this range, a layer having a high gettering effect is formed in all regions of the epitaxial layer 13 containing nitrogen or a part of the region excluding the surface in the thickness direction. The epitaxial wafer 11 with high cleanliness can be obtained. If the nitrogen concentration is less than 1 × 10 ¹³ atoms / cm ³ , the gettering effect is reduced, and even if the nitrogen concentration exceeds 1 × 10 ¹⁶ atoms / cm ³ , a significant improvement in gettering effect cannot be expected.

  In addition, the amount of nitrogen flowing into the reaction vessel 20 during the growth of the epitaxial layer 13 is preferably in a range that can be controlled by a mass flow meter, that is, 0.0001 liter / minute to 1 liter / minute, and further diluted. It is preferable to create a thin and stable amount of nitrogen gas by owning piping equipment and the like. By controlling the amount of nitrogen, the nitrogen concentration in the region containing nitrogen in the epitaxial layer 13 can be within the above range. If the amount of nitrogen flowing into the reaction vessel 20 is about the same as the carrier gas, the concentration required for the epitaxial layer 13 will be exceeded, and a nitride film will be formed and a normal epitaxial layer 13 cannot be formed.

For this reason, in the epitaxial wafer manufacturing method of the present invention, nitrogen is introduced into an arbitrary partial region in the thickness direction of the epitaxial layer 13 while growing the epitaxial layer 13 while controlling the amount and timing of nitrogen introduction. Let As a result, it is possible to form a region having a gettering effect in the epitaxial layer 13 in a subsequent process, relatively easily, and with high accuracy, rather than doping the silicon substrate 12 with nitrogen, thereby creating a stable device. it can.

On the other hand, FIG. 3 shows an example in which nitrogen is introduced in the middle of the epitaxial layer 13. This epitaxial wafer 11 is preferable when used for an insulated gate bipolar transistor (IGBT), but has an effect of strengthening the getter in other applications. In the case of forming the IGBT, the specific resistance together with the raw material gas is introduced into the reaction vessel 20 through the gas introduction pipe 28 and the gas supply port 26 while heating the silicon substrate 12 by a heat source provided outside the domes 21 and 22 in FIG. A dopant gas for controlling the above is introduced together with a carrier gas of H ₂ . Examples of the dopant gas include PH ₃ , and the nitrogen-containing gas is preferably introduced at a certain time (between n ⁺ and n ^{− in} FIG. 3) when the dopant gas is switched. In such IGBT varieties, nitrogen can be contained in the epitaxial layer 13 without inducing defects, so that it can be used as an alternative to the lifetime killer that has been secured by conventional gold diffusion, electron beam, neutron irradiation, etc. it can.

  FIG. 4 shows a case where nitrogen is contained in the entire region of the epitaxial layer 13. Thus, even if the epitaxial wafer 11 contains nitrogen in the entire region of the epitaxial layer 13, a gettering effect is generated in the epitaxial layer 13, and the epitaxial wafer 11 having high metal impurity surface cleanliness can be obtained. On the other hand, depending on the temperature at which the epitaxial layer 13 is formed and the amount of nitrogen introduced, if nitrogen is introduced near the surface of the epitaxial layer 13, the surface becomes rough. For this reason, when the epitaxial layer 13 is formed on the surface of the silicon substrate 12 by flowing a nitrogen-containing gas over the entire period when the raw material gas is circulated, the surface of the epitaxial layer 13 is preferably mirror-polished thereafter. Thereby, roughness of the surface of the epitaxial layer 13 due to the nitrogen-containing gas can be eliminated.

The following examples of the present invention will be described together with comparative examples.
< Reference Example 1>
A reaction vessel 20 shown in FIG. 2 is prepared, and a silicon substrate 12 for epitaxial growth is supported inside the reaction vessel 20, and the raw material is introduced into the reaction vessel 20 through the gas introduction pipe 28 and the gas supply port 26 while heating the silicon substrate 12. SiHCl ₃ as a gas and PH ₃ as a doping gas were introduced together with a carrier gas composed of H ₂ . And the epitaxial wafer 11 was obtained by flowing the nitrogen-containing gas diluted with the dilution mechanism in the whole period which distribute | circulates them to the reaction container 20. FIG. Seven silicon substrates 12 for epitaxial growth were prepared, and the amount of nitrogen introduced into each silicon substrate 12 was changed. That is, the amount of nitrogen introduced was varied so as to gradually increase by shaking about 5 ml / min, and seven types of epitaxial wafers 11 differing only in the amount of nitrogen introduced were obtained. And nitrogen taken in into epitaxial layer 13 in each wafer 11 was measured by SIMS and a raster change method. The result is shown in FIG.

< Reference Example 2>
Five epitaxial wafers 11 having different amounts of nitrogen taken into the epitaxial layer 13 were prepared. The amount of precipitation when these wafers 11 were contaminated with a certain amount of metal impurities was measured by ICP-MS. FIG. 6 shows the relationship between the amount of nitrogen taken into the epitaxial layer 13 and the amount of metal impurities deposited.

<Evaluation 1>
As shown in FIG. 6, when nitrogen is contained in the epitaxial layer 13, the amount of metal impurities deposited tends to increase. This is considered due to the fact that minute defects are induced by the nitrogen contained in the epitaxial layer 13. Thus, causing a gettering effect in a part of the area except for the d pita key tangential wafer 11 was contained nitrogen, the entire area or thickness direction of the surface of which nitrogen is contained epitaxial layer 13 in the epitaxial layer 13 You can see that
On the other hand, as is apparent from FIG. 5, it can be seen that the nitrogen in the epitaxial layer 13 varies depending on the amount of nitrogen contained in the source gas. Therefore, it can be seen that nitrogen can be introduced into the entire region of the epitaxial layer 13 or an arbitrary partial region in the thickness direction during the growth of the epitaxial layer 13 while controlling the amount and timing of nitrogen introduction. Then, in the manufacturing method of the present invention to control the introduction amount and timing of nitrogen, Ri by you doping nitrogen in a silicon substrate 12, relatively easily, accurately, epitaxial regions having partially gettering effect It can be seen that it can be introduced into layer 13.
From the result of FIG. 6, the nitrogen concentration in the region containing nitrogen of the epitaxial layer 13 is preferably 1 × 10 ¹³ to 1 × 10 ¹⁶ atoms / cm ³ in order to produce a gettering effect. I understand.

<Example 1 >
A reaction vessel 20 shown in FIG. 2 is prepared, and a silicon substrate 12 for epitaxial growth having a diameter of 20 cm and a thickness of 0.725 mm is supported inside the reaction vessel 20, and a gas introduction tube is heated while heating the silicon substrate 12. A source gas such as SiH ₂ Cl ₂ or SiHCl ₃ was introduced into the reaction vessel 20 through the gas supply port 26 and the gas supply port 26 together with a carrier gas of H ₂ . Then, an epitaxial wafer 11 was obtained by flowing a nitrogen-containing gas at the initial stage of flowing the source gas into the reaction vessel 20.
The nitrogen concentration at an arbitrary point in the portion 10 cm inside from the center and outer periphery of the obtained epitaxial wafer 11 was measured using a secondary ion mass spectrometer (SIMS). FIG. 7 shows the nitrogen concentration at the center of the epitaxial wafer 11 and FIG. 8 shows the nitrogen concentration at an arbitrary point in the portion 10 cm inside from the outer periphery of the epitaxial wafer 11.

<Evaluation 2>
As is apparent from FIGS. 7 and 8, it can be seen that nitrogen is contained in a partial region in the thickness direction of the epitaxial layer 13 in the vicinity of the interface between the silicon substrate 12 and the epitaxial layer 13. This is considered to be caused by flowing the nitrogen-containing gas in the initial stage of flowing the raw material gas to the reaction vessel 20. It can be seen that the nitrogen concentration at any one point in the center and the periphery of the epitaxial wafer 11 is equivalent. Thereby, it can be seen that the epitaxial wafer 11 in which nitrogen is introduced into the interface between the silicon substrate 12 and the epitaxial layer 13 can be obtained by the method of the present invention.

It is sectional drawing of the epitaxial wafer of this invention embodiment. It is a block diagram of the reaction container for producing the wafer. It is sectional drawing of another epitaxial wafer. It is sectional drawing of another epitaxial wafer. It is a figure which shows the relationship between the introduction amount of nitrogen, and the nitrogen taken in. It is a figure which shows the relationship between the quantity of taken-in nitrogen, and the precipitation amount of metal contamination. It is a figure which shows the nitrogen concentration of the thickness direction in the epitaxial wafer center. It is a figure which shows the nitrogen concentration of the thickness direction in the circumference | surroundings of an epitaxial wafer.

11 Epitaxial wafer 12 Silicon substrate 13 Epitaxial layer 20 Reaction vessel

Claims (1)

In the method for manufacturing an epitaxial wafer for forming the epitaxial layer on the surface of the silicon base plate arranged on the reaction container in by circulating the material gas into the reaction container,
The epitaxial layer is a silicon epitaxial layer;
Wherein the initial distribution of the raw material gas by flowing a nitrogen-containing gas is contained nitrogen in the region to the interface of the from the surface of the epitaxial layer and the inner and the silicon substrate than 1μm said epitaxial layer,
Method for producing an epitaxial wafer, comprising that you the nitrogen concentration of the nitrogen is contained area with ^{1 × 10 13 ~1 × 10 16} atoms / cm 3.

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