Monocrystalline silicon semiconductor wafer and method for producing the same

Abstract

To provide a method of manufacturing a semiconductor wafer of single crystal silicon which satisfies mechanical robustness without being hindered by an oxygen-induced stacking fault (OSF defect), and to provide a semiconductor wafer made of single crystal silicon.SOLUTION: A method for producing a semiconductor wafer of monocrystalline silicon includes growing a single crystal of silicon by the Czochralski (CZ) method, splitting at least one semiconductor wafer of monocrystalline silicon from the single crystal, and performing a first rapid thermal annealing (RTA), a second RTA treatment, and a third RTA treatment of the semiconductor wafer in this order.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The subject of the present invention is a method for manufacturing semiconductor wafers of monocrystalline silicon, and also semiconductor wafers made from monocrystalline silicon. [Background technology]

[0002] The production of certain electronic components such as BCD type (bipolar-CMOS-DMOS) requires the use of This requires semiconductor wafers made from monocrystalline silicon, which are distinguished by a particular mechanical robustness, especially during machining steps that must be carried out at relatively high temperatures for long periods of time. Furthermore, such wafers typically have a defect-free zone (DZ) with a predetermined depth and a high peak density of BMDs (BMDs) located in the interior of the semiconductor wafer and adjacent to the DZ. The defect-free region is understood to be a region of the semiconductor wafer's crystal lattice that is free of BMDs and incapable of generating BMDs by thermal treatment.

[0003] Conventional technology / issues RTA treatment under argon at temperatures above 1300°C is difficult because oxygen under such conditions Diffusion near the surface creates a relatively flat DZ with a depth of several microns. No. 2012 0 001 301 describes such RTA treatment and oxygen loss with weakening of the mechanical robustness of the semiconductor wafer. To enhance the surface roughness and promote the formation of BMDs within the wafer, the semiconductor wafer may be doped, for example, with nitrogen. When pulling single crystals by the Czochralski method (CZ method) for the production of semiconductor wafers, it is ensured that the ratio of the pulling rate V to the axial temperature gradient G at the phase boundary between the single crystal and the melt (V / G control) is adjusted so that the crystal lattice exhibits specific properties with respect to point defects such as silicon interstitials (silicon interstitials) and vacancies.

[0004] The term "rapid thermal processing" (RTA) refers to the process of bringing a semiconductor wafer to a relatively high temperature relatively quickly, This refers to a heat treatment in which the material is held at this temperature for a relatively short time and then cooled relatively quickly. An apparatus suitable for this purpose is described, for example, in US Patent Application Publication No. 2003 0 029 859. During the RTA process, the semiconductor wafer in the apparatus is placed on a ring that rotates. and exposed to thermal radiation from above.

[0005] It is also known that RTA treatment under argon and ammonia atmospheres, followed by RTA treatment under argon, leaves a relatively deep DZ (T. Muller et al., "Near-Surface Defect Control by Vacancy Injection / Out-Diffusing Rapid Thermal Annealing" (Phys. Status Solidi A, 2019, 1900325)). Summary of the Invention [Problem to be solved by the invention]

[0006] The drawback of nitrogen doping of semiconductor wafers during single crystal pulling is that the relatively high nitrogen concentration inside the semiconductor wafer promotes the formation of OSF defects (oxygen induced stacking faults). do.

[0007] Therefore, the object of the present invention is to provide a method for manufacturing a semiconductor device that satisfies mechanical robustness without being hindered by OSF defects. The goal is to provide access to semiconductor wafers of single crystal silicon that are consistent with the requirements of the single crystal. Furthermore, the semiconductor wafers should have the ability to develop BMDs below the DZ with a uniform BMD density in the radial direction. The semiconductor wafers should also possess these properties regardless of their location within the single crystal. [Means for solving the problem]

[0008] The object of the present invention is to provide a method for producing semiconductor wafers of monocrystalline silicon, comprising the steps of: growing a silicon single crystal by the CZ method; At least one semiconductor wafer of monocrystalline silicon is separated from the monocrystalline silicon, and the semiconductor wafer is completely composed of N-regions and has no aggregates of silicon interstitials or vacancies having a diameter of more than 20 nm. No aggregates exist, 5.3 × 10 17 atoms / cm 3 Over 5.9 x 10 17 atoms / cm 3 and oxygen concentrations below 1.0 x 10 12 atoms / cm 3 having a nitrogen concentration of: performing a first RTA treatment of the semiconductor wafer in a first atmosphere of argon and ammonia in a ratio of 1:2 to 1:0.75, at a temperature in a first temperature range of 750°C to 1100°C, for a period of 10 seconds to 30 seconds; performing a second RTA treatment of the semiconductor wafer in a second atmosphere of argon at a temperature within a second temperature range of 1190°C to 1280°C for a period of 20 seconds to 35 seconds; , and performing a third RTA treatment of the semiconductor wafer in a third atmosphere of argon and ammonia in a ratio of 8:10 to 3:2, at a temperature in a third temperature range of 1160°C to 1180°C for a period of 15 to 25 seconds, inclusive. This is achieved by:

[0009] RTA treatment in the sense of the present invention refers to the rapid heating of a semiconductor wafer of monocrystalline silicon to a target temperature. The method includes heating the semiconductor wafer to a target temperature, holding the semiconductor wafer at the target temperature for a holding time, and rapidly cooling the semiconductor wafer from the target temperature. The temperature increase rate during heating is preferably 15°C / sec or more, more preferably 25°C / sec or more, and the temperature decrease rate during cooling is 25°C / sec or more. The temperature increase and decrease rates are preferably slower for temperatures up to 100°C away from the target temperature than for temperatures with a large difference. The semiconductor wafer may be cooled or heated from one target temperature to the next, or may be subjected to intermediate cooling to a base temperature of 650°C or less between two target temperatures.

[0010] The first RTA treatment was performed using argon (Ar) and ammonia in a ratio of 1:2 or more and 1:0.75 or less. In a first atmosphere of nitriding (NH3), the semiconductor wafer is heated from a base temperature to a target temperature within a first temperature range of 750°C to 1100°C and held at the target temperature for a time period of 10 seconds to 30 seconds. The first and third RTA processes represent steps of nitriding the front surface of the semiconductor wafer and, to a lesser extent, the back surface of the semiconductor wafer. The nitrogen concentration introduced into the near-surface region of the semiconductor wafer by the nitriding RTA process is actually lower than that of the front surface. As a result, the increase in robustness of the semiconductor wafer is concentrated in the near-surface region on the front side of the semiconductor wafer.

[0011] In combination with the second RTA treatment and optionally the fourth RTA treatment, nitrogen is diffused into the near-surface region of the semiconductor wafer. In this way, up to 2×10 15 atoms / cm 3 Nitrogen enters the near-surface region of the semiconductor wafer, ensuring sufficient robustness of the crystal lattice. Nitrogen-induced formation of OSF defects in the interior of the semiconductor wafer occurs only when the nitrogen concentration required for such formation is achieved there. This is not being done because it is not possible to

[0012] The second RTA treatment of the semiconductor wafer is performed in a second atmosphere of argon at 1190° C. or higher for 12 hours. The treatment is carried out at a temperature within a second temperature range of 80° C. or less for a period of 20 to 35 seconds.

[0013] The third RTA treatment of the semiconductor wafer is performed with a second argon and a second argon gas in a ratio of 8:10 or more and 3:2 or less. The heating is carried out in an atmosphere of ammonium hydroxide and at a temperature in a third temperature range of 1160° C. to 1180° C. for a time period of 15 seconds to 25 seconds.

[0014] According to one preferred embodiment of the present invention, the fourth RTA treatment of the semiconductor wafer is also performed by the algorithm. The heating is carried out in a fourth atmosphere at a temperature in a fourth temperature range of 1130° C. to 1145° C. for a time of 25 seconds to 35 seconds.

[0015] To achieve the stated objective, the crystal lattice of the semiconductor wafer consists of only N regions, and Semiconductor wafers are cut from single crystals pulled by the CZ method under V / G control so that there are no agglomerates of silicon interstitials or vacancies with diameters exceeding 0 nm. The region preferably contains at least one Ni domain in which silicon interstitials predominate as a type of point defect and at least one Nv domain in which vacancies predominate as a type of point defect. The single crystal is not intentionally doped with nitrogen. Therefore, the nitrogen concentration is 1.0×10 12 atoms / cm 3 The semiconductor wafers separated from the single crystal are 5.3 x 10 17 atoms / cm 3 Over 5.9 x 10 17 atoms / cm 3 The oxygen concentration in the single crystal can be adjusted during production of said crystal, for example, by adjusting the rotation speed of the crucible and / or the single crystal, and / or by adjusting the pressure and / or flow rate of the gas forming the atmosphere in which the single crystal is grown, and / or by adjusting the strength of the magnetic field imposed on the melt.

[0016] A magnetic field is preferably applied to the melt during pulling of the single crystal, more preferably a horizontal magnetic field or a CUSP magnetic field.

[0017] The pulling speed V is preferably 0.5 mm / min or more, and the intention is to have a pulling speed V of at least 30 The objective is to produce semiconductor wafers with a diameter of 0 mm.

[0018] The single crystal is preferably grown in an atmosphere of argon, more preferably in an atmosphere containing argon and hydrogen, the partial pressure of hydrogen being preferably less than 40 Pa.

[0019] Further processing of the semiconductor wafer after separation from the single crystal and before the RTA treatment is preferably involves mechanical processing of semiconductor wafers separated from a single crystal by lapping and / or grinding, removal of damaged crystalline regions near the surface by etching, and pre-cleaning of semiconductor wafers in SC1 solution, SC2 solution, and ozone.

[0020] The object of the present invention is to provide a semiconductor wafer of single crystal silicon having a front surface and a back surface made of N regions. Ha is 5.3 x 10 17 atoms / cm 3 Over 5.9 x 10 17 atoms / cm 3 The interstitial oxygen concentration decreases from the front and back surfaces toward the interior of the semiconductor wafer, and At a depth of 2.0×10 15 atoms / cm 3 This is further achieved by the semiconductor wafer comprising a nitrogen concentration that is equal to or greater than 1000 ppm.

[0021] The semiconductor wafer is preferably distinguished by the following further properties: The nitrogen concentration considered in the near-surface region up to 150 μm from the back surface into the semiconductor wafer is , which is lower than the concentration considered in the near-surface region up to 150 μm from the surface into the semiconductor wafer. The nitrogen concentration in the near-surface region on the surface side up to a depth of 150 μm was measured by LT-FTIR. 1.0×10 14 atoms / cm 3 ~2.0×10 15 atoms / cm 3 In between, the concentration drops to a minimum, which corresponds to the nitrogen concentration in the single crystal from which the semiconductor wafer is derived. The surface is the face of the semiconductor wafer that faces upward during the RTA process. The nitrogen concentration in the near-surface region on the back surface is about 50% of the nitrogen concentration in the near-surface region on the front surface side of the semiconductor wafer.

[0022] The density of vacancy agglomerates in semiconductor wafers with sizes less than 20 nm is determined by IR-LST and Preferably 5.0 x 10 measured with a laser power of at least 70 mW 15 cm -3 Less than do.

[0023] After testing by heat treatment of the semiconductor wafer in which the seeds are developed into BMDs, the semiconductor wafer is The defect-free zone extends from the surface to a depth of preferably 10 μm or more and 20 μm or less into the interior of the semiconductor wafer. The density of BMDs is preferably 4.0×10 9 cm -3 ~8.0×10 9 cm - 3 , more preferably 5.0 × 10 9 cm -3 ~7.0×10 9 cm -3 The heat treatment involves heating a semiconductor wafer of single crystal silicon to a temperature of 800° C. for a period of 4 hours in an atmosphere consisting of 10 volume fraction nitrogen and 1 volume fraction oxygen, followed by heating the semiconductor wafer to a temperature of 1000° C. for a period of 16 hours. In a radial direction from the center to the edge of the semiconductor wafer, the density of BMDs preferably varies by less than 15%. Variation was determined by ascertaining BMD densities from center to edge at 148 locations and relating the maximum (max) to minimum (min) ascertained BMD densities in the formula (max-min) x 100% / mean, where mean is the arithmetic mean of the BMD densities ascertained at that location. .

[0024] The capacity of a semiconductor wafer to develop BMD is determined by the amount of material that is present in the semiconductor wafer after it is separated from the wafer. This capacitance is independent of the axial position of the semiconductor wafer material within the single crystal prior to doping. Because the single crystal is not intentionally doped with nitrogen, there is no effect from nitrogen segregation, and this capacitance is dependent on axial position.

[0025] After testing by heat treating the semiconductor wafer in dry oxygen at a temperature of 1000° C. for a period of 4 hours, the density of OSF defects is preferably less than 1 / cm 2 is less than.

[0026] The invention is further explained below with reference to examples and figures. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a partial view of an arrangement of semiconductor wafers during RTA processing in an apparatus configured for that purpose. [Figure 2] 1 shows the defect-free zone depth profile as a function of radius r for a semiconductor wafer of the present invention. [Figure 3] 1 shows the profile of BMD density as a function of radius r for a semiconductor wafer of the present invention. [Figure 4] 1A and 1B illustrate semiconductor wafer configurations during the generation of thermal stresses. [Figure 5] FIG. 1 shows a map of SIRD stress in a ring-shaped edge region of a semiconductor wafer. [Figure 6] FIG. 1 shows the relationship between depolarization and density of BMDs. DETAILED DESCRIPTION OF THE INVENTION

[0028] Silicon single crystals were pulled according to the CZ method in an atmosphere of argon and hydrogen (hydrogen partial pressure: 25-35 Pa) and further processed into semiconductor wafers with polished front and back surfaces. Due to the conditions regarding the V / G ratio selected during the pulling process, the crystal lattice of the semiconductor wafer with a diameter of 300 mm consists of only N domains with a certain percentage of Nv domains and a certain percentage of Ni domains. According to the new ASTM, semiconductor wafers subjected to a series of RTA treatments were found to have a 5.8 x10 17 atoms / cm 3 The oxygen concentration was

[0029] The semiconductor wafers were assigned to four groups and subjected to RTA treatment under the conditions summarized in the table. did.

[0030] [Table 1]

[0031] The semiconductor wafer was heated to the target temperature of the first RTA treatment at a rate of 70° C. / sec and cooled from the target temperature of the last RTA treatment at a rate of 30° C. / sec.

[0032] FIG. 1 shows a RTA process in an apparatus configured for that purpose, having a base 2. The semiconductor wafer 1 is placed on a ring 3 and heated from above, and only the surface of the semiconductor wafer 1 is exposed to the atmosphere by the RTA treatment. The ring 3 is placed on a rotating cylinder 4. Between the semiconductor wafer 1 and the reflector 5 is a cover 6 made of quartz. The presence of the cover 6, and the fact that atmospheric gases cannot pass unimpeded to the backside of the semiconductor wafer, limits the concentration of nitrogen passing into the semiconductor wafer near the surface during the nitriding RTA process to a concentration that is higher than that of the backside of the semiconductor wafer. It is crucial to ensure that the surface area is higher than the face area.

[0033] To determine the ability of BMD to develop in the inner region (BMD test), the semiconductor wafer was heat treated in an atmosphere consisting of a mixture of oxygen and nitrogen in an O:N volume ratio of 1:10, first at a temperature of 800°C for a period of 4 hours, and then at a temperature of 1000°C for a period of 16 hours.

[0034] To determine the depth of the defect-free zone, the radial density distribution of BMDs, and the radial size distribution of BMDs. An LST300A analysis tool from the Hungarian manufacturer Semilab Co. Ltd. was available at the facility. This tool was used to analyze semiconductors by IR-LST (infrared light scattering tomography). The wafer was analyzed.

[0035] FIG. 2 shows the defect-free zone depth profile as a function of radius r for a semiconductor wafer of the present invention. The average depth of the defect-free zone is approximately 14 μm.

[0036] 3 shows a profile of BMD density (BMD-D) as a function of radius r for a semiconductor wafer of the present invention in a representative example. The average density of BMDs is about 6.5×10 9 / cm 3 where The radial variation of BMD density is 11.6%.

[0037] To test their robustness, semiconductor wafers were subjected to thermal stress in a deposition reactor for depositing epitaxial layers. In this type of deposition reactor, the semiconductor wafer is positioned between upper and lower lamp arrays that direct thermal radiation to the back and front surfaces of the semiconductor wafer. The test was designed so that the semiconductor wafer heated 5°C more in the edge regions than in the central region surrounded by the edge regions. The semiconductor wafer was then analyzed by SIRD (Semiconductor Infrared Depolarization). Infrared radiation passing through the semiconductor wafer is depolarized in areas of the crystal lattice that have been damaged by thermal stress. The greater the damage, the higher the depolarization, measured in depolarization units (DU).

[0038] FIG. 4 shows the arrangement of a semiconductor wafer 1 during thermal stress between an upper lamp array 7 and a lower lamp array 8 in a deposition reactor, with the bold arrows representing the higher temperatures generated at the edge region of the semiconductor wafer due to irradiation.

[0039] 5 shows maps of SIRD stress in the ring-shaped edge region (up to 5 mm radially inward from the edge) for an example (left) and a comparative example (right). The example semiconductor wafer belonged to Group C. The comparative example semiconductor wafer differs in that it did not undergo any RTA treatment.

[0040] For the example semiconductor wafer, 0.1% of the analyzed area exceeded the depolarization threshold of 40 DU, while for the comparative semiconductor wafer, this percentage was 1.2%.

[0041] FIG. 6 shows the relationship between depolarization and BMD density. The average depolarized SIRD determined at measurement points distributed over the entire area of ​​the wafer is taken as the average BMD Density BMD-D avg is shown as a function of .

[0042] Therefore, the stress load in the semiconductor wafers of groups A to D is relatively small. is 4.0×10 9cm -3 Less than or 8.0 x 10 9 cm -3 In the comparative example of a semiconductor wafer of 1000 MPa, the stress load is significantly higher. In the comparative example, the semiconductor wafer is not subjected to any RTA treatment. The wafers were either untreated (Comparative Example V1) or treated differently from the present invention (Comparative Example V2). A first RTA treatment was performed in an argon atmosphere at a temperature of 1175° C. for a period of 5 seconds, followed by a second RTA treatment in an argon atmosphere at a ratio of 10:7.5. and ammonia atmosphere at a temperature of 1170° C. for a period of 15 seconds, and a third RTA treatment in an argon atmosphere at a temperature of 1150° C. for a period of 30 seconds. did. [Explanation of symbols]

[0043] List of reference symbols used 1. Semiconductor wafer 2 base 3 Rings 4 cylinders 5 Reflector 6 Cover 7 Upper Lamp Array 8 Lower Lamp Array

Claims

1. 1. A method for producing a semiconductor wafer of single crystal silicon, comprising: growing a silicon single crystal by the CZ method; Separating at least one of the semiconductor wafers of the single crystal silicon from the single crystal, the semiconductor wafer consisting entirely of N-region and silicon interstitials having a diameter greater than 20 nm. There are no aggregates of particles or voids, and the １７ atoms / cm ３ 5.9 x 10 １７ atoms / cm ３ The following oxygen concentrations and 1.0 x 10 １２ atoms / cm ３ having a nitrogen concentration of: performing a first RTA treatment of the semiconductor wafer in a first atmosphere of argon and ammonia in a ratio of 1:2 to 1:0.75, at a temperature within a first temperature range of 750° C. to 1100° C. for a period of 10 to 30 seconds; performing a second RTA treatment of the semiconductor wafer in a second atmosphere of argon at a temperature within a second temperature range of 1190° C. to 1280° C. for a period of 20 seconds to 35 seconds; And, and performing a third RTA treatment of the semiconductor wafer in a third atmosphere of argon and ammonia in a ratio of 8:10 to 3:2, at a temperature in a third temperature range of 1160° C. to 1180° C. for a period of 15 to 25 seconds, inclusive.

2. performing a fourth RTA treatment on the semiconductor wafer in a fourth atmosphere of argon at a temperature within a fourth temperature range of 1130° C. to 1145° C. for a time period of 25 seconds to 35 seconds; The method of claim 1 further comprising:

3. A semiconductor wafer of single crystal silicon having a front surface and a back surface made of N regions, 5.3 x 10 １７ atoms / cm ３ 5.9 x 10 １７ atoms / cm ３ The interstitial oxygen concentration is: The concentration of the ion-doped silicon dioxide decreases from the front surface and the rear surface toward the inside of the semiconductor wafer, and is 2.0×10 at a depth of 50 μm from the front surface. １５ atoms / cm ３ and a nitrogen concentration equal to or greater than a semiconductor wafer comprising:

4. The semiconductor wafer according to claim 3 , wherein the nitrogen concentration in the near-surface region on the back side is lower than the nitrogen concentration in the near-surface region on the front side.

5. a defect-free region extending from the surface to a depth of 10 μm or more and 20 μm or less into the semiconductor wafer; 5.0 x 10 ９ cm －３ ~7.0 x 10 ９ cm －３ and a base region having a BMD of a density of 5. The semiconductor wafer according to claim 3 or 4.

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