TWI436429B - Method for manufacturing epitaxial germanium wafer and epitaxial germanium wafer - Google Patents

Description

Method for manufacturing epitaxial germanium wafer and epitaxial germanium wafer

The present invention relates to an epitaxial silicon wafer capable of exhibiting high gettering ability even in a semiconductor device manufacturing process in which the heat treatment is lowered in temperature and progressed in a short period of time. And its manufacturing method.

The present application claims the priority of Japanese Patent Application No. 2009-095936, filed on Apr.

There are various methods for producing a silicon single crystal, and a Czochralski method (hereinafter referred to as CZ method) is exemplified as a most representative method for producing single crystal germanium. In the production of single crystal germanium by the CZ method, polycrystalline germanium is melted in crucible to form a germanium melt. Then, a seed crystal is immersed in the crucible melt, and the seed crystal is pulled at a predetermined rotation speed and a pulling speed, thereby growing a cylindrical single sheet under the seed crystal. Silicon single crystal ingot.

In the tantalum wafer obtained by slicing, grinding, and grinding a single crystal germanium ingot produced by the CZ method, supersaturation (state in which oxygen enters the inter-lattice) exists in the single crystal. Oxygen dissolved in the pulling of the ingot. Owing to such supersaturated oxygen, oxygen precipitates are formed inside the tantalum wafer during heat treatment with high temperature, for example, in a device manufacturing process with heat treatment at 1000 ° C or higher.

In the component manufacturing process, if heavy metals are mixed into the germanium wafer, the device characteristics are deteriorated, resulting in a decrease in manufacturing yield. However, if the oxygen precipitates as described above are present at a sufficient density inside the germanium wafer, the heavy metals mixed in the germanium wafer are trapped by the oxygen precipitates. Thereby, the surface of the germanium wafer as the element active layer is kept clean, so that deterioration of characteristics of the element or reduction in manufacturing yield can be prevented. Such an effect is called Intrinsic Gettering (IG). IG has been used as a method to prevent deterioration of component characteristics or reduction in yield due to heavy metal contamination.

On the other hand, in a tantalum wafer whose surface has been mirror-polished, there is a pit-like grown-in defect called a crystal originated particle (COP). In the refinement of the element, this COP is a cause of a decrease in the manufacturing yield of the element. Therefore, as a tantalum wafer for a high-quality element, an epitaxial wafer in which a single crystal germanium layer is epitaxially grown on the surface of a germanium wafer after mirror polishing is used. The epitaxial wafer has no COP on the surface, thereby preventing a decrease in yield caused by COP.

A CVD method (chemical vapor deposition method) is generally widely used for the formation of a single crystal germanium layer which is grown by epitaxy. In the formation of the single crystal germanium layer by the CVD method, a high-temperature heat treatment of 1100 ° C or higher with rapid temperature rise and temperature drop is generally performed. However, during the high-temperature heat treatment of 1100 ° C or higher, the oxygen precipitates present in the germanium wafer are melted and disappear. Therefore, there is a problem in that the IG effect obtained by oxygen precipitation in the device manufacturing process of the epitaxial wafer is It becomes very weak, making it difficult to fully capture heavy metals.

Therefore, it is also known to use a p/p ^- epitaxial wafer which generates oxygen precipitates in a component manufacturing process in order to improve the degassing ability. As a method of manufacturing the p/p ^- embedded germanium wafer, for example, a method of manufacturing an epitaxial germanium wafer in which a single crystal germanium layer is epitaxially grown on a surface of a germanium-added germanium wafer is known (for example, reference is made to Patent Document 1). Further, a method for producing an epitaxial germanium wafer in which a single crystal germanium layer is epitaxially grown on a surface of a germanium-added germanium wafer (for example, see Patent Document 2) or a single crystal germanium layer is added. A method for producing an epitaxial germanium wafer having a surface epitaxial growth of a tantalum wafer of nitrogen and carbon (for example, see Patent Document 3).

However, in recent years, even when a p/p ^- plated crystal wafer having nitrogen or carbon added as described above is used, a sufficient degassing ability of heavy metals cannot be ensured. That is, in the manufacturing process of a semiconductor element in recent years, in order to realize an ultrafine structure, the heat treatment in the element manufacturing process is lowered (for example, the maximum temperature is about 300 to 990 ° C), and the time is short (for example, heat treatment). The time is about 5 minutes) There is progress. In such a low temperature or short time heat treatment, the diffusion distance of oxygen is short. Therefore, even if the epitaxial germanium wafer has an oxygen deposition nucleus in advance, it is difficult to sufficiently promote the growth of the oxygen precipitate, and the degassing ability of the heavy metal is insufficient.

[Advanced technical literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 10-50715

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2002-154891

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2002-201091

The present invention provides a method for producing an epitaxial germanium wafer, which can reliably precipitate oxygen precipitates even when the heat treatment in the manufacturing process of the semiconductor element is lowered and shortened, and the oxygen precipitates are surely The heavy metal is captured, whereby deterioration of characteristics of the element and reduction in manufacturing yield can be prevented.

Moreover, the present invention provides an epitaxial germanium wafer which can reliably capture heavy metals in accordance with the low temperature and short-time heat treatment in the manufacturing process of the semiconductor element, thereby preventing deterioration of characteristics of the element and reduction in manufacturing yield. .

In order to solve the above problems, the present invention provides a method of manufacturing an epitaxial germanium wafer as described below.

That is, the method for producing an epitaxial germanium wafer of the present invention includes the step of adding nitrogen in a concentration range of 3 × 10 ¹³ atoms/cm ³ or more and 2 × 10 ¹⁶ atoms/cm ³ or less, and/or 5×10 ¹⁵ atoms/cm ³ or more, 3×10 ¹⁷ atoms/cm ³ or less in a concentration range of carbon, and pulling a single crystal germanium ingot by a CZ method; and processing the above single crystal germanium ingot into a germanium wafer; Forming a single crystal germanium layer on one surface of the germanium wafer by an epitaxial method to obtain an epitaxial germanium wafer; and performing the epitaxial germanium wafer at 600 ° C or higher and 850 ° C or lower for 5 minutes or longer and 300 minutes or shorter. The first heat treatment; and the epitaxial germanium wafer subjected to the first heat treatment is heated to a range of 900 ° C or more and 1100 ° C or less, and then performed in a range of 900 ° C or more and 1100 ° C or less for 30 minutes. The second heat treatment above and below 300 minutes.

Preferably, the inter-lattice oxygen concentration of the epitaxial germanium wafer after the first heat treatment and the second heat treatment is 7.5×10 ¹⁷ atoms/cm ³ or more and 18×10 ¹⁷ atoms/cm ³ or less.

Further, it is preferable that the epitaxial germanium wafer manufactured by the method for producing an epitaxial germanium wafer is provided in a low temperature process in which the heat treatment in the subsequent step is 300 ° C or higher and 990 ° C or lower. Process.

Moreover, the epitaxial germanium wafer of the present invention is characterized in that the epitaxial germanium wafer is manufactured by the above-described method for manufacturing an epitaxial germanium wafer.

According to the method for producing an epitaxial germanium wafer of the present invention, nitrogen and/or 5 × 10 ¹⁵ atoms/cm in a concentration range of 3 × 10 ¹³ atoms / cm ³ or more and 2 × 10 ¹⁶ atoms / cm ³ or less are added. A single crystal germanium ingot having a concentration range of ³ or more and 3 × 10 ¹⁷ atoms/cm ³ or less is used to form a germanium wafer. Further, after the single crystal germanium layer is formed by epitaxial growth on the germanium wafer, a predetermined concentration is formed by the first and second heat treatments, for example, a size of 10 to 30 nm and a density of 3 × 10 ⁷ /cm. ³ or more oxygen precipitates (bulk micro defect (BMD)). When such an epitaxial wafer is used, even in a low-temperature heat treatment of a range of, for example, a low-temperature heat treatment in the range of 300 to 990 ° C or a short-time heat treatment in which the heat treatment time is 5 minutes or less, the element manufacturing step of a so-called low-temperature or short-time heat treatment may be used. The heavy metal is surely captured by a sufficient concentration of oxygen precipitates precipitated in advance. Therefore, the surface of the tantalum wafer as the element active layer can be kept clean, so that deterioration of characteristics of the element or reduction in manufacturing yield can be prevented.

Further, in the epitaxial germanium wafer of the present invention, a predetermined concentration, for example, an oxygen precipitate (BMD) having a size of 10 to 300 nm and a density of 3 × 10 ⁷ /cm ³ or more is formed in advance. Therefore, when the epitaxial germanium wafer of the present invention is used in a component manufacturing step of a so-called low-temperature, short-time heat treatment such as a low-temperature heat treatment in the range of 300 to 990 ° C or a short-time heat treatment in which the heat treatment time is 5 minutes or shorter. The heavy metal can be surely captured by a sufficient concentration of oxygen precipitates precipitated in advance. That is, when the epitaxial wafer of the present invention is used, the surface of the germanium wafer as the element active layer can be kept clean, and deterioration of characteristics of the element or reduction in manufacturing yield can be prevented.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

Hereinafter, a preferred embodiment of the method for producing single crystal germanium of the present invention will be described based on the drawings. In addition, this embodiment is described in order to better understand the gist of the invention, and the present invention is not limited unless otherwise specified.

Hereinafter, an embodiment of the tantalum substrate of the present invention and a method of manufacturing the same will be described based on the drawings.

Fig. 1 is a flow chart showing a method of manufacturing an epitaxial germanium wafer of the embodiment. Further, in the present embodiment, the epitaxial wafer is described as a so-called low-temperature treatment in which the maximum temperature of the heat treatment in the element manufacturing process is, for example, 300 to 990 ° C. or The heat treatment time is a short time treatment of 5 minutes or less.

In the manufacturing method of the present embodiment, as shown in FIG. 1, an epitaxial wafer manufacturing step P1 and a device manufacturing step P2 are included. The epitaxial wafer fabrication step P1 includes a single crystal germanium pulling step S1, a wafer processing step S2, an epitaxial film forming step S3, a first heat treatment step S4, and a second heat treatment step S5. The component manufacturing step P2 includes a component fabrication step S6 and a thinning and processing step S7. The epitaxial wafer of the present invention obtained by the epitaxial wafer fabrication step P1 is supplied to the element manufacturing step P2, thereby obtaining a semiconductor element. In addition, the first heat treatment step S4 and the second heat treatment step S5 may also be incorporated into the initial step of the component process (component fabrication step P2).

In the single crystal crucible pulling step S1, polycrystalline germanium which is a raw material of the germanium crystal is laminated in the quartz crucible. On the surface of the polycrystalline silicon, an appropriate amount of graphite powder is applied as a carbon component. Further, silicon nitride was added to the quartz crucible as a nitrogen component, and boron (boron, B) was introduced as a dopant. For example, in accordance with the Chai method (CZ method), CZ crystals in which nitrogen and carbon are added are extracted (growth) from the raw materials introduced into the quartz crucible.

Further, the concentration of nitrogen added to ³ × 10 ¹³ atoms / cm 3 or more and 2 × 10 ¹⁶ atoms / cm ³ or less, and, the concentration of carbon added to 5 × 10 ¹⁵ atoms / cm ³ Above and 3 × 10 ¹⁷ atoms / cm ³ or less. Further, regarding the nitrogen and the carbon, not only the two may be added, but only one of them may be added, for example, only carbon is added or only nitrogen is added to extract the CZ crystal.

A boron-containing P-type single crystal germanium ingot is prepared by adding carbon at a raw material stage. When a single crystal germanium ingot is produced from a raw material to which carbon is added, the oxygen concentration Oi is controlled to pull up the single crystal germanium ingot. Hereinafter, the pulling of the CZ single crystal germanium ingot when only carbon is added will be described. A wafer having a diameter of 300 mm will be described as an example, but the present invention is not limited thereto.

Fig. 2 is a longitudinal cross-sectional view of a CZ furnace suitable for explaining the production of the single crystal germanium ingot of the embodiment. The CZ furnace includes a crucible 101 disposed at a center portion in a chamber, and a heater 102 disposed outside the crucible 101. The crucible 101 has a double structure in which the quartz crucible 101c for accommodating the raw material melt 103 is held by the outer graphite crucible 101a, and is rotated and lifted and driven by a support shaft 101b called a pedestal.

Above the cymbal 101, a substantially cylindrical heat insulator 107 is provided. The heat insulator 107 is a structure in which a casing is made of graphite and the inside is filled with graphite felt. The inner surface of the heat insulator 107 is a taper surface whose inner diameter gradually decreases from the upper end portion toward the lower end portion. The upper portion of the outer surface of the heat insulator 107 is a tapered surface corresponding to the inner surface, and the lower portion of the outer surface of the heat insulator 107 is formed to be substantially straight so that the thickness of the heat insulator 107 gradually increases downward. (vertical) face. That is, a surface whose outer diameter gradually decreases toward the lower portion is formed on the upper portion of the outer surface of the heat insulator 107, and the outer diameter is substantially constant at the lower portion of the outer surface of the heat insulator 107.

The CZ furnace can, for example, achieve growth of a 300 mm single crystal ingot having a target diameter of 310 mm and a body length of, for example, 1200 mm.

The specification example of the heat insulator 107 is as follows. The outer diameter of the portion placed in the crucible is set to, for example, 570 mm, and the minimum inner diameter of the lowermost end S For example, it is set to 370 mm, and the width (thickness) W in the radial direction is set to, for example, 100 mm. Further, the outer diameter of the crucible 101 (or the quartz crucible 101c) is, for example, 650 mm, and the height H from the lower end of the heat insulator 107 to the molten metal surface is, for example, 60 mm.

Next, a method of setting the operating conditions for growing a carbon-added CZ single crystal germanium ingot will be described.

First, a high purity polycrystalline germanium is charged into the crucible. Then, boron (B) is added as a dopant so that the resistivity in the single crystal germanium is P ^- type. Further, in the present invention, the boron (B) concentration is P ⁺ type, which means that the specific resistance of the single crystal germanium is equivalent to 8 mΩcm to 100 mΩcm, and the P type means that the specific resistance of the single crystal germanium is equivalent to 0.1 Ωcm to 100 Ωcm. The concentration at the time, the P ^- type refers to the concentration at which the specific resistance of the single crystal germanium is equivalent to 0.1 Ωcm to 100 Ωcm. Further, the P/P ^- type refers to a wafer in which a P-type single crystal germanium layer is laminated by epitaxial growth on a P ^- type substrate.

In the present embodiment, a dopant is added to the ruthenium melt so that the carbon concentration is in the range of 5 × 10 ¹⁵ atoms/cm ³ or more and 3 × 10 ¹⁷ atoms / cm ³ or less. Further, the crystal rotation speed, the crucible rotation speed, the heating conditions, the applied magnetic field conditions, the pulling speed, and the like are controlled so as to achieve a predetermined oxygen concentration.

Further, the inside of the apparatus was set to an inert gas atmosphere and the pressure was reduced from 1.33 to 26.7 kPa (10 to 200 torr). For example, hydrogen gas may be mixed in an inert gas (such as Ar gas) so as to reach 3 to 20% by volume, and may flow into the furnace to be an inert gas atmosphere. Preferably, the pressure is 1.33 kPa (10 torr) or more, preferably 4 kPa or more and 26.7 kPa or less (30 torr) More preferably, it is 4 Torr or more and 9.3 kPa or less (30 torr or more and 70 torr or less). When the partial pressure of hydrogen becomes low, the concentration of hydrogen in the melt and the crystal becomes low. In order to prevent this from happening, the above lower limit pressure is specified.

On the other hand, if the pressure in the furnace is increased, the flow rate of the inert gas such as Ar on the melt is lowered, whereby the carbon or self-melting liquid degassed from the carbon heater or the carbon member is obtained. The reactant gas such as evaporated SiO will be difficult to vent. If the exhaust of the gas becomes difficult, the carbon concentration in the crystallization will be higher than the desired value. Further, SiO is condensed in a portion of the upper portion of the molten metal in the furnace at about 1100 ° C or lower, whereby dust is generated. Moreover, dislocation of crystals is caused by the above-mentioned dust falling into the melt. The above upper limit pressure is specified in order to prevent the occurrence of such phenomena.

Then, heating is performed by the heater 102 to melt the crucible to form the melt 103. Then, the seed crystal attached to the seed chuck 105 is immersed in the melt 103, and the crucible is pulled while rotating the crucible 101 and the pulling shaft 104. The crystal orientation is set to any of {100}, {111}, or {110}. After crystallizing for crystallizing without dislocation, a shoulder portion is formed, and the shoulder is changed to, for example, a target body diameter of 310 mm.

Then, the main body portion is grown to a temperature of, for example, 1200 mm at a constant pulling speed, and after the diameter is reduced under normal conditions, the crystal growth is completed. Here, the pulling speed can be based on the resistivity, the diameter size of the single crystal germanium ingot, and the hot zone structure of the single crystal pulling device used (heat Environment, etc., etc. are appropriately selected. As the pulling speed, for example, a pulling speed including a region which qualitatively generates an oxidation induced stacking fault (OSF) ring in a single crystal plane can be employed. The lower limit of the pulling speed can be set to be equal to or higher than the pulling speed at which the OSF ring region is generated in the single crystal plane and no dislocation clusters are generated.

By the single crystal 矽 pulling step S1 as described above, nitrogen and/or 5 × 10 ¹⁵ atoms/cm including a concentration range of 3 × 10 ¹³ atoms / cm ³ or more and 2 × 10 ¹⁶ atoms / cm ³ or less can be obtained. A single crystal germanium ingot of carbon having a concentration range of ³ or more and 3 × 10 ¹⁷ atoms/cm ³ or less.

Next, the single crystal germanium ingot obtained in the step S1 is pulled up from the single crystal crucible by the wafer processing step S2 to obtain a single crystal germanium wafer (hereinafter referred to as a germanium wafer) 11 containing carbon (refer to FIG. 3A). ).

As a processing method of the tantalum wafer 11 in the wafer processing step S2, for example, a single crystal germanium ingot is cut by a cutting device such as an inner diameter (ID) saw or a wire saw. slice. After the enamel wafer obtained by the dicing is annealed, the surface is ground. Surface treatment such as cleaning. Further, in addition to these steps, various steps such as wrapping, washing, and grinding may be employed, and the steps of use may be appropriately changed in accordance with the purpose of changing or omitting the order of steps.

In the tantalum wafer 11 (tantalum substrate) obtained as described above, the boron (B) concentration is P ^- type, and the carbon concentration is 5×10 ¹⁵ atoms/cm ³ or more and 3×10 ¹⁷ atoms/cm ³ or less, and The oxygen concentration is set to 1.5 × 10 ¹⁸ atoms / cm ³ or more and 1.7 × 10 ¹⁸ atoms / cm ³ or less. Further, when nitrogen is added, the nitrogen concentration was set to 3 × 10 ¹³ atoms / cm and 2 × 10 ¹⁶ atoms ³ or more / cm ³ or less.

Since carbon and/or nitrogen are contained in the ruthenium in a solid solution form, carbon and/or nitrogen can be introduced into the ruthenium lattice in a form substituted with ruthenium. The atomic radius of carbon and/or nitrogen is small compared to helium atoms, so when carbon and/or nitrogen are coordinated at the displacement site, the stress field of the crystal is a compressive stress field. Thereby, oxygen and impurities between the crystal lattices are easily captured by the compressive stress site. Starting from the carbon at the replacement position, the oxygen precipitates accompanying the dislocations are easily present at a high density, so that the silicon wafer 11 can be imparted with a high degassing effect.

The concentration of such carbon and/or nitrogen added must be limited to the above range. The reason is that if the carbon concentration is less than the above range, then carbon. Oxygen precipitates, nitrogen. The formation of oxygen-based precipitates does not become active. That is, when the carbon concentration is less than the above range, the above high density carbon cannot be achieved. Oxygen precipitates and nitrogen. Formation of oxygen-based precipitates.

On the other hand, if it exceeds the above range, then carbon. Oxygen precipitates and nitrogen. The formation of oxygen-based precipitates is promoted, and high-density carbon can be obtained. Oxygen precipitates and nitrogen. Oxygen-based precipitates, but the size of the precipitates is suppressed. As a result, the tendency of the strain around the precipitate to weaken becomes stronger. Therefore, the effect of strain is weak, so that the effect for capturing impurities is reduced.

Further, as a influence on the precipitates, boron is promoted by setting a higher boron concentration. carbon. nitrogen. Formation of complex defects of oxygen.

Next, after the surface of the cerium wafer 11 which is a CZ crystal to which carbon or/and nitrogen is added is mirror-finished, for example, RCA cleaning in which SC1 and SC2 are combined is performed. Then, in the epitaxial film forming step S3, in order to form a single crystal germanium layer by epitaxial growth, the germanium wafer 11 is loaded into the epitaxial growth furnace. Then, using various CVD methods (chemical vapor deposition), boron (B) is concentrated The single crystal germanium layer 12 having a P-type can be grown on the surface of the germanium wafer (see FIG. 3B).

The P/P ^- type epitaxial wafer 10 on which the single crystal germanium layer 12 is formed on one surface of the germanium wafer 11 is formed, and the oxide film 13 and the nitride film 14 are formed as needed (see FIG. 3C). The epitaxial wafer 10 in this state is a CZ crystal containing boron and solid solution carbon and/or solid solution nitrogen. However, the oxygen deposition nucleus formed during the crystal growth or the oxygen precipitate shrinks by the heat treatment during the epitaxial growth, and thus the oxygen precipitates which are not significantly observed under the optical micromirror are not observed.

In the element manufacturing step P2 to be described later, the highest temperature of the heat treatment is, for example, a so-called low-temperature treatment in the range of 300 to 990 ° C, or a short-time treatment in which the heat treatment time is 5 minutes or shorter. In this manner, even if the element manufacturing step P2 is a low-temperature, short-time process, in order to reliably capture heavy metals, the epitaxial wafer 10 is subjected to a first heat treatment step S4 and a second heat treatment step S5 for ensuring a gettering sink. .

First, in the first heat treatment step S4, the epitaxial wafer 10 is placed in an annealing furnace, and in a mixed environment of oxygen and an inert gas such as argon or nitrogen, 600 ° C or more and 850 ° C or less, 5 minutes or more and 300 minutes or less are performed. Heat treatment. Then, after the epitaxial wafer 10 subjected to the first heat treatment is heated in a range of 900 ° C or more and 1100 ° C or less, the second epitaxial wafer 10 is heated in a range of 900 ° C or more and 1100 ° C or less for 30 minutes or more and 300 minutes or less. Heat treatment step S5.

In the first heat treatment step S4, the temperature is preferably 600 ° C or more and 750 ° C or less, more preferably 600 ° C or more and 700 ° C or less. First heat treatment step The treatment time of S4 is preferably 30 minutes or more and 300 minutes or less, more preferably 60 minutes or more and 300 minutes or less. As long as the temperature of the first heat treatment step S4 is 600 ° C or more and 850 ° C or less, a sufficient amount of oxygen deposition nuclei can be generated. Further, as long as the treatment time of the first heat treatment step S4 is 5 minutes or longer and 300 minutes or shorter, a sufficient amount of oxygen deposition nuclei can be generated.

The temperature increase rate in the second heat treatment step S5 is not particularly limited, but is preferably 0.1 ° C / min or more and 3 ° C / min or less.

In the second heat treatment step S5, the temperature is preferably 950 ° C or more and 1100 ° C or less, more preferably 1000 ° C or more and 1050 ° C or less. The treatment time in the second heat treatment step S5 is preferably 60 minutes or longer and 300 minutes or shorter, more preferably 120 minutes or longer and 300 minutes or shorter. When the temperature of the second heat treatment step S5 is 900 ° C or more and 1100 ° C or less, the oxygen deposition nucleus can be surely grown, and as a result, a sufficient amount of oxygen precipitates can be obtained. Further, as long as the treatment time of the second heat treatment step S5 is 30 minutes or longer, an oxygen precipitate having a size that easily traps impurities between the crystal lattices can be formed, and if it is 300 minutes or shorter, it is possible to reliably form an impurity sufficient to capture inter-lattice. The size, strain of oxygen precipitates.

The oxygen deposition nucleus is generated by the first heat treatment S4, and the oxygen deposition nucleus is grown by the second heat treatment S5 to obtain an oxygen precipitate.

When such a first heat treatment step S4 and a second heat treatment step S5 are performed, a majority of boron is precipitated with the replacement position carbon of the epitaxial wafer 10 or the replacement position nitrogen as a starting point. carbon. nitrogen. Oxygen-based oxygen precipitates 16. In addition, in the present invention, boron. carbon. nitrogen. Oxygen precipitates contain boron. Carbon complex (clusters) or contain boron. A precipitate of a complex (clusters) of nitrogen.

If the germanium wafer 11 containing solid solution carbon and/or solid solution nitrogen is used as a starting material, the oxygen precipitates 16 will naturally occur throughout the entire wafer 11 during the initial stage of the component fabrication step. Precipitate. Therefore, degassing adsorption with high degassing ability for metal contamination in the element manufacturing step can be formed over the entire thickness of the germanium wafer 11 from directly below the epitaxially grown single crystal germanium layer 12. Thus, degassing of the vicinity of the single crystal germanium layer 12 is achieved.

In order to achieve this degassing, as boron. carbon. Oxygen complex or boron. nitrogen. The oxygen precipitate (BMD) 16 of the oxygen-based composite has a size of, for example, 10 to 300 nm, and is present in the tantalum wafer 11 at 3 × 10 ⁷ /cm ² or more. In addition, the BMD size at this time is the diagonal length of the precipitate in the TEM (Transmission Electron Microscopy) observation of the cross section of the 矽 wafer in the thickness direction, and the precipitate in the observation field is observed. The average value is expressed.

The size of the oxygen precipitates 16 is set to be equal to or lower than the lower limit in the above range in order to capture (degas) intergranular impurities (for example, heavy metals, etc.) by using the strain effect generated by the interface between the parent ruthenium atom and the oxygen precipitate. The probability increases. Further, the size of the oxygen precipitates 16 is not problematic even if it is larger than or equal to the above range.

The trapping (degassing) of heavy metals in the ruthenium crystal depends on the strain generated at the interface between the parent ruthenium atom and the oxygen precipitate and the interface level density (bulk density). Therefore, the density range in the tantalum wafer 11 of the oxygen precipitates 16 is preferably set to the above range.

After the steps as described above, the oxygen precipitates are obtained in advance. The epitaxial germanium wafer 10 of the present invention precipitated in density. The epitaxial germanium wafer 10 of the present invention has an oxygen precipitate having a predetermined density deposited. Therefore, the present invention is a low-temperature process in which the maximum temperature of the heat treatment in the component manufacturing step P2 to be described later is, for example, a low-temperature process in the range of 300 to 990 ° C or a short-time process in which the heat treatment time is 5 minutes or less. The epitaxial wafer 10 is also capable of reliably capturing heavy metals.

In the device manufacturing step S6, a structure as an element is formed on the surface of the germanium wafer 10, and as shown in FIG. 4A, the germanium element substrate 21 is manufactured to have a thickness T3 of 1000 μm or less and 500 μm or more and 800 μm or less. And 600 μm or more and 700 μm or so. As the component fabrication step S6, a general manufacturing step of a memory element can also be employed. Although an example is shown here, it is not particularly limited to this structure. step.

In the element fabrication step S6, a metal oxide semiconductor-field effect transistor (MOS-FET) having a floating gate is formed. Thereby, the 矽 element substrate 21 on the surface where the memory element is formed is manufactured.

In the above-described element fabrication step S6, for example, in the step of forming a gate oxide film, a step of separating a device, and forming a polysilicon gate electrode, for example, a low-temperature heat treatment in the range of 300 to 990 ° C or a heat treatment time of 5 minutes or less is performed. Short-term heat treatment. FIG. 5 shows an example of the low-temperature, short-time heat treatment in the element production step S6. Further, the short-time high-temperature heat treatment (for example, RTA/RTO/LSA) shown in FIG. 5 includes a temperature rising step of entering a temperature band exceeding 1000 ° C in a very short time.

Conventionally, in such a low-temperature, short-time heat treatment, an oxygen precipitate having a sufficient density cannot be precipitated as a degassing adsorption. However, in the epitaxial wafer 10 of the present invention, the first heat treatment step S4 and the second heat treatment step S5 are used as oxygen precipitates having a sufficient density (3 × 10 ⁷ /cm ² or more) at the time of degassing adsorption. (BMD) 16 is preliminarily precipitated. Therefore, even if the heat treatment in the element manufacturing step P2 is low temperature and short time, heavy metals can be reliably captured.

Then, the substrate 27 having a thickness of, for example, about 30 μm is produced by the thin film formation in the element manufacturing step P2 and the processing step S7. In the thinning and processing step S7, first, as the grinding processing step, the back surface 21a of the tantalum element substrate 21 having the thickness T3 shown in FIG. 4A is thinned by the grinding process to form the thickness shown in FIG. 4B. The germanium element substrate 23 of T4.

As an example of the conditions at this time, it is set as follows.

Thickness T3: 700μm, Thickness T4: 60μm (50~80μm)

Forming a random processing metamorphic layer on the back side

Surface state: roughness about 5nm

Next, after the grinding process, chemical mechanical polishing is performed using a hard slurry having a hardness of about 1 μm to 10 μm composed of colloidal silica or ruthenium crystal or diamond like carbon. The chemical mechanical polishing (CMP) process is performed to obtain the tantalum element substrate 27 having the thickness T5 shown in Fig. 4C.

As an example of the conditions at this time, it is set as follows.

Thickness T5: 30μm

Surface state: roughness about 5nm

The CMP processing conditions were set as follows.

As the abrasive grains, colloidal cerium oxide or cerium crystal or diamond-like carbon having a hardness of about 200 HV to 1000 HV and a particle diameter of about 10 to 100 nm is used. The pressure is 9.8 kPa to 49 kPa (100 g/cm ² to 500 g/cm ² ) and the treatment time is carried out on a plate made of alumina by a slurry containing the above-mentioned abrasive grains in a weight ratio of 1% by weight to 5% by weight. 10~60 seconds of processing.

Thereafter, as a polishing step, a treatment of a pressure of 9.8 kPa to 49 kPa (100 g/cm ² to 500 g/cm ² ) and a treatment time of about 10 to 60 seconds is performed. Thereby, the thickness of the germanium element substrate 27 is 40 μm or less and 5 μm or more, and the back surface 27a is provided with an external degassing which generates residual stress of 200 MPa or less and 5 Mpa or more. At this time, the surface state of the back surface 27a was such that cracks and defects were not generated and the roughness was about 5 nm. Here, the measurement of the residual stress is performed by a Raman apparatus and by the method of incident on the cross section.

As described above, in the method for producing an epitaxial wafer of the present invention, nitrogen and/or 5 × 10 ¹⁵ are added in a concentration range of 3 × 10 ¹³ atoms / cm ³ or more and 2 × 10 ¹⁶ atoms / cm ³ or less. A germanium wafer is obtained by a single crystal germanium ingot of a concentration range of atoms/cm ³ or more and 3 × 10 ¹⁷ atoms/cm ³ or less. Further, after the single crystal germanium layer is formed by epitaxial growth on the obtained germanium wafer, a predetermined concentration is formed by the first and second heat treatments, for example, a size of 10 to 300 nm and a density of 3 × 10 ⁷ / Oxygen precipitates (BMD) of cm ³ or more. When such an epitaxial wafer is used, it can be borrowed in a component manufacturing step of a so-called low-temperature, short-time heat treatment such as a low-temperature heat treatment in the range of 300 to 990 ° C or a short-time heat treatment in a heat treatment time of 5 minutes or less. The heavy metal is surely captured by a sufficient concentration of oxygen precipitates precipitated in advance. Therefore, the surface of the tantalum wafer as the element active layer can be kept clean, so that deterioration of characteristics of the element or reduction in manufacturing yield can be prevented.

While the present invention has been described in its preferred embodiments, the present invention is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application.

10‧‧‧Emission wafer

11‧‧‧矽 wafer

12‧‧‧ Single crystal layer

13‧‧‧Oxide film

14‧‧‧ nitride film

16‧‧‧Oxygen precipitates

21‧‧‧矽Element substrate

21a, 27a‧‧‧ back

23‧‧‧矽Element substrate

27‧‧‧Substrate

101‧‧‧坩埚

101a‧‧‧Graphite

101b‧‧‧Support shaft

102‧‧‧heater

103‧‧‧ Raw material melt

104‧‧‧Tip shaft

105‧‧‧ seed chuck

107‧‧‧Insulation

H‧‧‧ Height

S‧‧‧minimum inner diameter

T3, T4, T5‧‧‧ thickness

W‧‧‧Width

S1~S7, P1~P2‧‧‧ steps

1 is a flow chart showing a method of manufacturing an epitaxial germanium wafer of the present invention.

2 is a cross-sectional view showing an example of a pulling step of a single crystal germanium ingot.

3A to 3C are cross-sectional views showing a manufacturing step of an epitaxial wafer.

4A to 4C are cross-sectional views showing the processing steps of the epitaxial wafer in the element manufacturing step.

FIG. 5 is a graph showing an example of low-temperature, short-time heat treatment in which the element fabrication step is performed by temperature and time.

S1~S7, P1~P2‧‧‧ steps

Claims (5)

A method for producing an epitaxial germanium wafer, comprising the steps of: adding nitrogen in a concentration range of 3 × 10 ¹³ atoms / cm ³ or more, 2 × 10 ¹⁶ atoms / cm ³ or less, and / or 5 × 10 ¹⁵ a carbon having a concentration range of atoms/cm ³ or more and 3×10 ¹⁷ atoms/cm ³ or less, and pulling a single crystal germanium ingot by a CZ method; processing the single crystal germanium ingot into a germanium wafer; Forming a single crystal germanium layer on one surface of the germanium wafer by an epitaxial method to obtain an epitaxial germanium wafer; and performing the epitaxial germanium wafer at 600 ° C or higher and 850 ° C or lower for 5 minutes or longer and 300 minutes or shorter. After the first heat treatment, the epitaxial germanium wafer subjected to the first heat treatment is heated to a temperature of 900 ° C or more and 1100 ° C or less at a temperature increase rate of 0.1 ° C / min or more and 3 ° C / min or less. The second heat treatment is performed at a temperature of 900 ° C or more and 1100 ° C or less for 30 minutes or more and 300 minutes or less, and an oxygen precipitate having a size of 10 to 300 nm and a density of 3 × 10 ⁷ /cm ² or more is epitaxially twinned. Precipitated inside the circle. The application method of manufacturing the epitaxial silicon wafer of patentable scope of item 1, wherein the heat treatment is carried out between the first and the second heat treatment after epitaxial silicon wafer of lattice oxygen concentration of 7.5 × 10 ¹⁷ atoms /cm ³ or more and 18 × 10 ¹⁷ atoms/cm ³ or less. The method for producing an epitaxial wafer according to claim 1, wherein after the second heat treatment, a low temperature treatment in a range of 300 ° C or higher and 990 ° C or lower is performed. An epitaxial germanium wafer manufactured by the method for manufacturing an epitaxial germanium wafer according to claim 1 or 2, wherein the epitaxial germanium wafer is provided to 300 Low temperature treatment process in the range of °C or higher and 990 °C or lower. An epitaxial germanium wafer produced by the method for fabricating an epitaxial wafer according to the first or second aspect of the patent application.