JP2007067321A - Simox substrate and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an SIMOX (Separation by Implanted Oxygen) substrate where pit-like defect generation on a silicon layer surface is extremely small, and further an SIMOX substrate which has a sufficient gettering site inside. <P>SOLUTION: The SIMOX substrate uses a wafer that is detected as a Grown-in defect by evaluation by a Cu decoration method, and not detected as a flow pattern by selective etching in an area where an OSF (Oxygen Induced Stacking Fault) ring generation position is at the outer periphery of the silicon single crystal, an area where an OSF ring generation position is present from the center to the outer periphery, or an area where an OSF ring disappears sampled from the silicone single crystal by a CZ method which has a non-defect area expanded under raising conditions, and a maximum defect size is preferably ≤0.09 μm. Further, in the SIMOX substrate initial oxygen density is 6.5×10<SP>17</SP>atoms/cm<SP>3</SP>(old ASTM) and oxygen deposits to become a gettering site are formed in the substrate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention uses a wafer obtained from a silicon single crystal manufactured by the Czochralski method (hereinafter referred to as “CZ method”) as a substrate, and an SOI (Silicon on Insulator) in which a silicon layer is formed on an insulator. More particularly, the present invention relates to a SIMOX (Separation by Implanted Oxygen) substrate in which oxygen ions are implanted from the surface of a silicon wafer and a buried oxide insulating layer is formed therein, and a method of manufacturing the same. It is.

  A substrate having an SOI structure in which a single crystal silicon layer is formed on an insulator can be completely separated from each other as compared with a conventional silicon single crystal substrate, and device miniaturization and high reliability are easy. Since the parasitic capacitance between the substrates is reduced, the speed can be increased, the three-dimensional structure is simple, and the integration and the multi-function are easy. For this reason, it is considered that it will be utilized further for higher integration, higher speed, and higher power consumption of LSI.

  As a main manufacturing method of the SOI substrate, there are a bonding method and a SIMOX method. The bonding method uses two single crystal wafers, which are bonded via an oxide film formed on the surface, this oxide film layer is used as an insulating layer, and one wafer is polished to a desired thickness to form an element. A silicon active layer. In this case, since it is difficult to realize a thin silicon layer having a uniform thickness by polishing, a layer in which hydrogen ions are previously implanted under the oxide film is formed to a predetermined depth, and after bonding, A smart cut method has been developed in which hydrogen gas is deposited and cracks are generated for splitting.

  In the case of the bonding method, the silicon layer on which the element is formed has an advantage that if a single crystal wafer with guaranteed quality is used, it can be directly exposed on the insulating film. However, the manufacturing process is complicated, and an increase in manufacturing cost is unavoidable due to the need for two wafers.

  In the SIMOX method, oxygen ions are implanted at a high concentration from a surface of a single crystal silicon wafer to a specific depth, and then bonded to silicon by high-temperature heat treatment to form an insulating layer of silicon oxide. By controlling the implantation energy, the depth of the insulating layer can be easily controlled, and two wafers are not required unlike the bonding method, the process is simple, and the manufacturing cost can be reduced.

However, the amount and quality of the buried oxide layer formed immediately below the surface by oxygen ion implantation largely depend on the ion implantation amount (dose amount) and implantation conditions. Usually, the ion implantation amount has an optimum range, the generation amount of crystal defects due to ion implantation is small, and the optimum dose amount for forming a continuous uniform buried oxide layer after high-temperature heat treatment is 2.5 × 10 ¹⁷ to It has been found to be in the range of 5.0 × 10 ¹⁷ / cm ² .

  After the oxygen ion implantation, the buried oxide layer is formed by heating to 1300 ° C. or higher in a rare gas atmosphere such as argon at atmospheric pressure containing 1.0% or less of oxygen. However, with the dose amount referred to as low-dose ion implantation, the thickness of the insulator layer is not always sufficient and the electrical insulation property may be inferior. The oxygen concentration in the inside is increased to, for example, 30% or more, and the oxidation treatment is performed to increase the thickness of the buried oxide layer.

  Patent Document 1 discloses an invention of a countermeasure against the method of increasing the thickness of the buried oxide layer by high-temperature oxidation treatment to simultaneously progress the surface oxidation and thin the silicon active layer. This is because, prior to the high-temperature oxidation treatment, a silicon component to be oxidized by the treatment is formed in advance on the silicon active layer by epitaxial growth, polysilicon growth or amorphous silicon growth, and the silicon active layer having a sufficient thickness after the treatment is formed. The layer remains.

  Further, as a cause of the insulation failure of the buried oxide layer in the SIMOX substrate, there is a Grown-in defect of the silicon wafer to be used, and Patent Document 2 discloses a diameter in a region from the surface to the depth at which the buried oxide layer is formed. An invention of a method using a silicon single crystal wafer in which a void or COP (Crystal Originated Particle) of 0.1 μm or more in terms of conversion does not exist has been proposed. A wafer having an area free from voids or COP defects is formed with an epitaxial layer of 0.4 μm or more, a heat treatment of 1000 to 1300 ° C. or more in a rare gas atmosphere with impurities of 5 ppm or less, or a pulling rate of 0 It is obtained by sampling from a single crystal grown at 8 mm / min or less.

  This is mainly related to the production of a SIMOX substrate which is made of a normally used silicon wafer and has a sufficient buried oxide layer and a more healthy silicon active layer. From the stage, there are some specially designed for SIMOX.

For example, the invention disclosed in Patent Document 3 is a method using a single crystal containing nitrogen in an amount of 1 × 10 ¹⁴ to 1 × 10 ¹⁷ atoms / cm ³ . When oxygen ions are implanted and heated to a temperature close to the melting point of 1300 ° C. or higher to form a buried oxide layer, and the oxygen partial pressure is increased to increase the thickness of the oxide layer, it is called a thermal pit on the substrate surface. Many square pyramids or conical indentations with a size of about 10 μm are generated.

  Thermal pits not only change the thickness of the silicon single crystal on the buried oxide layer, but often penetrate the buried oxide layer and destroy the SOI structure. Thermal pits are one major problem for expanding the application of SIMOX substrates. However, the addition of nitrogen suppresses the generation of thermal pits.

  Due to the recent demand for higher integration and miniaturization of devices, it is important to improve the quality of wafers obtained from single crystals grown by the CZ method, and there are no defects that do not have grown-in defects such as COPs and dislocation clusters. Wafers are being manufactured.

  When a silicon single crystal is grown by the CZ method, if the pulling speed is high, a vacancy-rich defect such as COP that lacks silicon atoms tends to occur, and if the pulling speed is slow, the silicon atom has excessive dislocation cluster type defects. Is likely to occur. According to the explanation of the inventive technique disclosed in Patent Document 4, when the pulling rate is Vmm / min and the temperature gradient in the crystal in the pulling axis direction in the temperature range immediately after solidification is G ° C / mm, V / G is specified. In this value range, a region where neither a COP defect nor a dislocation cluster defect appears, and a portion where a so-called ring-shaped OSF (Oxygen Induced Stacking Fault) occurs exists in the region.

  FIG. 1 is a diagram schematically illustrating the occurrence of these defects. This figure shows a single crystal grown by continuously changing the pulling speed by the normal CZ method, and longitudinally cut along the pulling axis, and the presence of micro defects is observed in the cross section by X-ray topography using Cu decoration. The distribution is shown.

  Since the surface of the wafer taken from the single crystal is perpendicular to the pulling axis, as can be seen from the figure, in the single crystal when the pulling speed is high, there is an OSF generation region in the periphery, and the COP defect is mainly in the center. When a wafer is obtained and the pulling speed is low, a wafer whose entire surface is a dislocation cluster generation region is obtained. Between the COP generation region and the dislocation cluster generation region, regions indicated as an oxygen precipitation promotion region, a ring-like OSF generation region, an oxygen precipitation promotion region, an oxygen precipitation suppression region, and the like appear, all of which are grown-in. This is a defect-free region where no defect exists.

  The dislocation cluster defect is as large as about 10 μm, and if an integrated circuit is formed on this defect, it becomes a defective product. On the other hand, the COP defect has a size of about 0.1 to 0.2 μm and can be eliminated to some extent by heat treatment of the wafer. The single crystal pulling speed can be increased and the productivity can be improved. For the reason that precipitates having a ring action can be formed, COP is likely to occur in the speed range of A to B shown in FIG. However, it has been manufactured at a pulling speed that becomes a region that does not appear on the periphery or on the wafer surface.

  As described above, the defect-free region appears when V / G is in a specific range. In the case of normal single crystal growth, since the single crystal pulled from the melt is cooled from the outer peripheral surface, the temperature gradient G in the vertical direction is larger near the outer peripheral surface than inside. For this reason, the defect-free region appears close to the outer peripheral surface when the pulling speed V is high, and appears at the center when the pulling speed is low.

  As shown in FIG. 1, under normal single crystal pulling conditions, a defect-free region can appear in a part of the wafer, but the entire surface of the wafer cannot be made a defect-free region. In contrast, when the silicon single crystal is pulled from the melt, the temperature gradient in the pulling axis direction inside the single crystal immediately after solidification is reduced so that the crystal center is large and the outer periphery is small. Various studies have been made to expand the defect-free region in the horizontal direction shown in FIG. 1 in the horizontal direction by using a growth apparatus in which the structure of the portion (hot zone) is variously devised. If the defect-free region can be expanded in the horizontal direction with respect to the pulling axis, a single crystal can be obtained from which a wafer in the entire defect-free region can be collected.

  For example, looking at the method of the invention disclosed in Patent Document 5, in the temperature range from the melting point to 1370 ° C., the temperature gradient in the pulling axis direction of the single crystal is Gc at the center and Ge at the outer periphery. Gc is 2.8 ° C./mm or more and Gc / Ge is 1 or more, that is, about 1.2 to 1.5. The temperature distribution in the crystal during the pulling is controlled by using radiation from the heat shield, cooling body, crucible inner wall surface or melt surface arranged around the single crystal immediately after the pulling.

  As a result, the change in the defect distribution due to the pulling rate investigated by the same method as in FIG. 1 is as shown in FIG. By controlling the temperature distribution in the single crystal using a hot zone structure growth apparatus capable of obtaining such a defect distribution and performing growth in the speed range of E to F, a single crystal in a defect-free region can be obtained over the entire length. As a result, a wafer having no defects on the entire surface can be obtained.

JP 2000-294513 A JP 2000-68489 A Japanese Patent Laid-Open No. 10-64837 JP-A-8-330316 JP 2002-187794 A

  As described above, the SIMOX substrate has an advantage that the process is simpler and can be manufactured at a lower cost than the SOI substrate by the bonding method. However, the quality of the silicon active layer for forming the element tends to be damaged due to oxygen ion implantation embedded in the insulating oxide film, and tends to be inferior to the bonded SOI substrate.

  Therefore, in order to further improve the quality of the silicon active layer, improvement of ion implantation conditions, application of various heat treatments, improvement of material single crystals, and the like have been performed, but sufficient ones have not been obtained. It has also been proposed to form an epitaxial layer, whereby a good active layer can be obtained, but the advantage that the process characteristic of the SIMOX substrate is simple and can be manufactured at low cost is lost.

  The present invention takes advantage of the above-described SIMOX method to form a more healthy silicon active layer, in particular, a SIMOX substrate having a very small number of pit-like defects occurring on the surface of the silicon layer and causing a significant problem, and a sufficient getter inside. An object of the present invention is to provide a SIMOX substrate having a BMD (Bulk Micro Defect) serving as a ring site and a method for manufacturing the same.

The gist of the present invention is as follows.
(1) An SOI substrate in which a wafer obtained from a silicon single crystal manufactured by the CZ method is formed by SIMOX, where the OSF ring generation position is located on the outer periphery of the crystal, and the OSF ring generation position exists from the center to the outer periphery. The SIMOX substrate is characterized in that the defect is generated in the surface silicon active layer due to the OSF or the Grown-in defect, which is composed of a region where the OSF ring disappears.
(2) An SOI substrate in which a wafer obtained from a silicon single crystal manufactured by the CZ method is formed by SIMOX, where the OSF ring generation position is in the outer periphery of the crystal, and the OSF ring generation position exists from the center to the outer periphery. SIMOX substrate characterized by using as a substrate a wafer that comprises a region that disappears or an OSF ring disappears, and that is detected as a grown-in defect by evaluation by a Cu decoration method and that is not detected as a flow pattern evaluation by selective etching It is.

In this SIMOX substrate, the maximum size of the grown-in defect is desirably 0.09 μm or less using, for example, an OPP apparatus. On the other hand, the density of the grown-in defects does not need to be particularly limited because it does not affect the surface defects after SIMOX.
(3) The SIMOX substrate according to (1) or (2) above, wherein a wafer having an initial oxygen concentration of 6.5 × 10 ¹⁷ atoms / cm ³ (old ASTM) or more is used.
(4) The SIMOX substrate according to any one of (1) to (3), wherein an oxygen precipitate serving as a gettering site is formed inside the substrate.
(5) Oxygen ions are implanted into the wafer heated to 300 to 550 ° C. once or plural times, and then heated to 1300 ° C. or more to form an insulating oxide film therein, thereby forming the inside of the SOI layer. The method of manufacturing a SIMOX substrate according to any one of (1) to (4) above, wherein OSF and Grown-in defects are eliminated.
(6) Oxygen ions are implanted into a wafer heated to 300 to 550 ° C. and implanted with oxygen ions at a temperature of room temperature to 300 ° C., and then heated to 1300 ° C. or higher to form an insulating oxide film therein. This is a method for manufacturing a SIMOX substrate according to any one of (1) to (4) above.
(7) The above process, wherein oxygen ions are implanted to form an insulating oxide film therein, and then a heat treatment at 400 to 900 ° C. and a heat treatment at 900 to 1250 ° C. are performed. This is a method for manufacturing a SIMOX substrate according to any one of 1) to (4).

  In the SIMOX substrate of the present invention, defects such as pits generated in the silicon active layer on the surface are as low as those of the bonded SOI substrate or the SIMOX substrate having an epitaxial layer formed on the surface, and have sufficient gettering action inside. Have a good BMD. In addition, the manufacturing process or manufacturing cost is not significantly different from that of normal SIMOX, and can be effectively used as a semiconductor substrate that is required to have higher performance in the future.

  The present inventor has made various studies on methods for reducing defects in the silicon active layer above the buried oxide layer and improving its quality in manufacturing an SOI substrate by the SIMOX method.

  In the silicon active layer of the substrate by the SIMOX method, damage that may be caused by the passage of ions, or the surface after removal of the surface oxide film in the oxidation process for increasing the thickness of the buried oxide layer, a buried oxide that can be as large as 10 μm Dozens to hundreds of pyramids or conical depressions called thermal pits reaching the layer are generated.

  Regarding the thermal pits, using the wafer containing nitrogen described in Patent Document 3 described above has an effect of reducing the size of the pits, but does not seem to reduce the number of the pits. The thickness of the silicon active layer of the SOI substrate tends to become thinner due to the miniaturization of the circuit, and it is necessary to sufficiently reduce the number of such defects as well as the size of such defects.

  When the occurrence position of the thermal pit is examined, it often coincides with the occurrence position of the COP defect generated on the used substrate. However, when the size of the COP defect was small, no thermal pit was generated and the defect disappeared. It was estimated that this could be eliminated if the defects were small during the heat treatment for forming the buried oxide layer.

  Grown-in defect distribution in a cross-section parallel to the pulling axis when a single crystal is grown by continuously reducing the pulling rate using a growing device with an improved hot zone for defect-free wafer production. For example, as shown in FIG.

  With such a growth apparatus, a single crystal capable of collecting a so-called defect-free wafer can be obtained by performing the growth with the pulling speed set between E to F in FIG. If the pulling rate is reduced to reach the dislocation cluster generation region, a large dislocation cluster defect occurs and a wafer that can be used practically cannot be obtained. On the other hand, when the pulling speed is faster than E, the region where the ring-shaped OSF is generated enters the wafer, and when it is further increased, the region where the ring-shaped OSF is generated moves to the outer peripheral portion of the wafer, and the central portion is This is a region where COP defects are likely to occur.

  For this reason, for the production of defect-free wafers, the pulling speeds E to F are usually selected so that the entire single crystal is defect-free. However, when the growth is performed by this growth apparatus, even when the ring-shaped OSF enters or the ring-shaped OSF moves to the outer periphery of the wafer, a single crystal can be obtained in which a COP defect is small over the entire surface and the number of wafers is small.

  Therefore, paying attention to the size of the COP defect, oxygen ions are implanted by using single crystal wafers pulled up at various speeds as shown in FIG. 2, and oxide formation treatment and oxide layer thickening treatment are performed. Then, a SIMOX substrate was fabricated, and defects in the silicon active layer on the surface were investigated.

  As a result, even if the OSF ring is in the region D to E in FIG. 2 where the OSF ring appears inside the wafer, even if the OSF ring is in the C to D region where the COP defect appears near the outer periphery and in the center, It has been found that if the size is small, a SIMIOX substrate having a good silicon active layer with few defects can be obtained.

  Based on such knowledge, the limit conditions were further clarified, and the present invention could be completed.

  That is, the SIMOX substrate of the present invention is sampled from a silicon single crystal by the CZ method in which the defect-free region is enlarged by the growth conditions, and the OSF ring generation position is in the outer periphery of the crystal, and the OSF ring generation position extends from the center to the outer periphery. A wafer having an existing region or a region where the OSF ring disappears and the maximum defect size of a grown-in defect such as COP is 0.09 μm or less is used as a substrate.

  The ion implantation, oxide layer forming treatment, and oxide layer thickening treatment as the SIMOX substrate may be those usually employed. Furthermore, if the post-implantation wafer temperature is set to a low temperature of 200 ° C. or less and ion implantation with a reduced dose is added, the effect of increasing the soundness of the oxide film can be obtained.

  Oxide formation of implanted oxygen ions is performed, for example, by heating to 1300 ° C. or higher in a rare gas atmosphere containing 1.0% or less of oxygen, and the oxide layer thickening treatment is performed with a rare gas containing oxygen exceeding 10%. What is necessary is just to perform by heating in a gas atmosphere.

  In the SIMOX substrate of the present invention, the wafer used for the substrate is collected from a single crystal by a growth apparatus in which the hot zone is improved and the defect-free region is expanded. As can be seen from the comparison between FIG. 1 and FIG. 2, the single crystal produced by the growth apparatus having an improved hot zone for producing defect-free wafers has excellent uniformity of the in-plane defect distribution of the wafer taken therefrom. Further, in the portion close to the ring-shaped OSF, the grown-in defects such as COP are small and the number thereof is small.

  In such a single crystal, the wafer used for the substrate has a Grown-in defect size of 0.09 μm or less even at the maximum. Here, the Grown-in defect is detected by a Cu decoration method and does not include a flow pattern defect caused by selective etching.

  The size of the maximum defect existing in the wafer of the substrate is set to 0.09 μm or less. A defect exceeding 0.09 μm does not disappear by heat treatment exceeding 1300 ° C. after ion implantation, and causes thermal pits. Because. Further, the grown-in defect is considered to be damaged by oxygen ion implantation, but if it is not small, it seems to disappear by high-temperature heat treatment.

  The smaller the defect is, the easier it is to disappear, and the maximum defect size is preferably 0.05 μm or less, more preferably 0.03 micron.

  In the region where the maximum defect size is 0.09 μm or less, if the hot zone is the same, the pulling speed range is between C and F in FIG. In the meantime, there are a region where the OSF ring generation positions of C to D are near the outer periphery of the crystal, a region where the OSF ring generation positions of D to E exist from the center to the outer periphery, or a region where the OSF rings of E to F disappear. is there.

  In the manufacture of defect-free wafers, the E to F region is usually used in the single crystal manufacturing conditions of FIG. 2, and the single crystal having the D to E or C to D region conditions is not used. This is to avoid the adverse effects of COP defects and OSF as much as possible. However, in actual manufacturing operations, even if the single crystal being pulled can be partially made into the E to F region, the control of the growth conditions to be realized over the entire length is extremely strict, and the single crystal has a sufficiently large diameter. Control becomes difficult. For this reason, the yield of non-defective wafers is not high, which causes an increase in cost.

  However, when a single crystal produced by this defect-free wafer manufacturing method is used as the SIMOX substrate, the defect-free wafer may be a single-crystal wafer that has a defective condition of D to E or CD. It turns out that it becomes a good base substrate.

  That is, as a substrate, a SIMOX substrate having a good silicon active layer can be obtained even with a wafer made of not only defect-free regions E to F but also regions C to E.

  This is because the single crystal is broken in the ion-implanted region after oxygen ion implantation, but the single crystal portion remains only on the surface of the silicon substrate and in the very vicinity, and it is activated by recrystallization by high-temperature heat treatment. It was thought that the grown-in defects that were damaged by the ion implantation also crystallized at the same time as the layer changed to a single crystal.

  Therefore, as a result of investigating the defect distribution before and after the high-temperature oxidation treatment with respect to the size of the defect and the presence / absence of oxygen ion implantation using a defect inspection apparatus (Magics) In many cases, it remains without disappearing after the treatment, but when oxygen ions are implanted, it is found that the portion where the ions have passed disappears if the size of the defect is small.

  This is because low-temperature oxygen ion implantation leaves the influence of polycrystallization or amorphization in the passage of ions and naturally damages the grown-in defects. The amorphous part has the effect of promoting recrystallization, and it is thought that the defect disappeared. In the OSF generation region, OSF nuclei shrink and disappear due to such high temperature heating.

  As described above, the D-E region in FIG. 2 and the COP generation, which are not conventionally used in the manufacture of defect-free wafers, appear in a position where the generation region of the ring-shaped OSF is considerably inserted from the center to the periphery of the wafer. The fact that the region can be a good SIMOX substrate up to the C to D region appearing in the center of the wafer means that the growth conditions of the single crystal for collecting the substrate wafer are relaxed and the yield is greatly improved, resulting in a significant increase in manufacturing cost. Results in a decline.

  The speed range of C to F shown in FIG. 2 varies depending on the diameter of the single crystal to be grown and the structure of the hot zone to be used. Therefore, the single crystal is grown by changing the pulling speed by the diameter of the single crystal and the growth apparatus. It is necessary to check the pulling speed range. The speed range of C to F confirmed by the apparatus to be used is substantially the same even if the growth chances are different.

  In addition, a defect-free single crystal growth device with an improved hot zone is used to reduce the size of COP defects and expand the defect-free region. Methods such as nitrogen doping or incorporating a water-cooled structure in the hot zone have been proposed, but in any method, the maximum Grown-in defect size is 0.09 μm or less, a defect-free region, and If the wafer is grown in an adjacent region, the effects of the present invention can be exhibited.

Next, when it is desired to secure an intrinsic gettering site in the SIMOX substrate for the purpose of eliminating heavy metal contamination of the silicon active layer, the oxygen concentration of the substrate wafer is set to 6.5 × 10 ¹⁷ atoms / cm ³ ( old ASTM) or higher.

If oxygen in the wafer is deposited as BMD (Bulk Micro Defect), it becomes a gettering site. The reason why the oxygen concentration is set to 6.5 × 10 ¹⁷ atoms / cm ³ (old ASTM) or more is to ensure the strength of the wafer substrate and to form a sufficient BMD. The upper limit is not particularly limited, but is naturally limited in order to be a healthy wafer.

  The oxygen concentration of the wafer substrate may be low because oxygen oxide is implanted to form an oxide layer, and then the oxide layer is thickened by high-temperature heat treatment in a high oxygen atmosphere. . Due to this high-temperature oxidation, inward diffusion of oxygen proceeds, but at that time, the oxygen concentration inside the substrate increases.

  FIG. 3 is a diagram illustrating an example of an increase in oxygen concentration by high-temperature heat treatment in a high oxygen atmosphere. This is done by measuring the oxygen concentration in the wafer before heat treatment, heating it at 1320 ° C. for 10 hours in an argon atmosphere containing 40% oxygen at atmospheric pressure, and then removing the oxide film on the surface. This is the result of investigating the increase in oxygen concentration in the silicon near the wafer surface. The oxygen concentration in silicon is determined by FT-IR (infrared ray transmission method).

  As is clear from FIG. 3, the lower the oxygen concentration in the wafer of the substrate, the greater the amount of oxygen increase in the thickening process. Even if the oxygen concentration in the substrate wafer is low, the oxygen concentration is sufficient to form oxygen precipitates. Reach.

  The BMD precipitation treatment to be a gettering site may be performed on the substrate on which the oxide layer formation treatment has been performed after oxygen ion implantation. For example, it heats at 400-900 degreeC for 4-48 hours, and then heats at 900-1250 degreeC for 1-48 hours. As the atmosphere, nitrogen, oxygen, a rare gas, or a mixed gas thereof may be used.

  Note that the size of the oxygen precipitate is 200 nm or less, desirably 150 nm or less, and more desirably 100 nm or less. That is, in recent device processes, rapid thermal processing (RTP) has become the mainstream, and extremely large thermal stress is generated in the SIMOX substrate during this heat treatment, which may cause dislocations from oxygen precipitates. For this reason, it is desirable to limit the size of the oxygen precipitates. In the experiments conducted by the inventors, it was confirmed that when thermal stress equivalent to about 5 MPa is applied to the substrate, dislocations are generated from the oxygen precipitate size of about 200 nm. ing.

  The first heating at 400 to 900 ° C. is for the formation of oxygen precipitation nuclei. At temperatures below 400 ° C., the diffusion of oxygen is slow and nucleation is insufficient, and at temperatures above 900 ° C., the solubility increases. However, sufficient nuclei may not be formed. The next heating at 900 to 1250 ° C. is for growing and enlarging the formed nuclei. If it is less than 900, the growth rate is slow, and if it exceeds 1250 ° C., oxygen re-dissolves, and both have sufficient BMD. It cannot be formed.

  As a method for effectively obtaining the nuclei of oxygen precipitates, carbon may be doped during the growth of a single crystal.

[Example 1]
As a comparative example, a wafer having a diameter of 200 mm by a single crystal obtained by a normal CZ method, a wafer having a 5 μm thick silicon epitaxial film grown on the wafer surface, and a defect-free wafer are obtained as an example of the present invention. Thus, a wafer collected from a single crystal obtained by a growth apparatus having an improved hot zone was prepared, and a SIMOX substrate was produced.

The manufacturing conditions of the SIMOX substrate were as follows. First, the substrate wafer was heated to 400 ° C., and oxygen ions with an acceleration energy of 140 keV and a dose of 4.0 × 10 ¹⁷ / cm ² were implanted. Next, the temperature of the wafer was lowered to room temperature, and oxygen ions were implanted at a dose of two orders of magnitude with the same acceleration energy.

  After the ion implantation, the furnace was charged in a furnace at 700 ° C., heated to 1320 ° C., and held for 5 hours in an atmospheric pressure atmosphere of 1% oxygen remaining argon. Next, oxygen was kept at 40% and held for 10 hours, and then cooled and taken out from the furnace.

Table 1 shows the state of the wafer of the substrate used. Test Nos. 1 and 2 used for comparison use a wafer obtained from a normal single crystal by the CZ method. The minimum COP defect size is 0.12 μm and the defect density is 1.0 × 10 ^5. / Cm ² was exceeded. In this Run No. 1, examining the pit defects SIMOX substrate surface after the oxide film removing surface with an optical microscope, it was greater than 1 / cm ^2. In the SIMOX substrate No. 2 in which the same wafer was used and a silicon epitaxial film was formed on the surface, the number of pit defects was less than 0.1 / cm ² .

  Trial numbers 3 to 6 are based on wafers collected from a single crystal manufactured using a growth apparatus for obtaining defect-free wafers. Trial number 3 is the region above C in FIG. Similarly, regions C to D, trial number 5 is a region from D to E, and trial number 6 is a wafer made of a single crystal grown under the region conditions E to F.

The maximum size of the COP defect in trial number 3 was 0.11 μm, and in other regions, it was 0.09 μm or less. The number of pit defects in the SIMOX substrate produced from these wafers was 1 / cm ² or more in trial number 3, but all of trial numbers 4 to 6 were less than 0.1 / cm ² .

Trials Nos. 7 to 10 were obtained by adding 6% hydrogen to the atmosphere in the apparatus and raising the same in the same growth apparatus as trial numbers 3 to 6. As a result of growing under the same conditions, the maximum size of the COP defect was 0.09 μm or less even in the region above C in FIG. These wafers were subjected to the same ion implantation twice to form a SIMOX substrate, but the pit defects were all less than 0.1 / cm ² .

  About the SIMOX substrate of the trial number 1 and the trial number 3, the defect distribution was investigated using the defect inspection apparatus (Magics). The results are shown in FIG. In trial No. 1, many defects were observed, and when compared with the generation position of the grown-in defect of the wafer before oxygen implantation, these defects occurred at points corresponding to substantially the same position. confirmed. In trial No. 3, the number of defects in the SIMOX substrate was small, and it was thought that it was caused by another factor regardless of the position of defects before oxygen implantation.

As described above, it can be said that the pit defects of the SIMOX substrate of the present invention are almost the same as those of a wafer having an epitaxial film formed on the surface.
[Example 2]
Using the SIMOX substrate of trial No. 3 in Example 1, the sample was placed in a furnace heated to 500 ° C., then heated to 700 ° C. at a temperature rising rate of 0.3 ° C./min and held for 1 hour. Next, the temperature was raised to 1000 ° C. at a rate of temperature rise of 3 ° C./min and held for 8 hours. After cooling, the substrate was cleaved and immersed in a light etching solution for 2 minutes, and the density of oxygen precipitates was observed with an optical microscope. As a result, it was confirmed that the oxygen precipitate density was 1 × 10 ¹⁰ / cm ³ or more.
Example 3
A SIMOX substrate was produced under the same conditions as in Example 1 using a wafer grown under the E to F region conditions with an initial oxygen concentration of 6.5 × 10 ¹⁷ / cm ³ . This was put into a furnace heated to 400 ° C., then heated to 900 ° C. at a temperature rising rate of 0.2 ° C./min and held for 1 hour. Next, after holding at 1000 ° C. for 16 hours, cooling, cleaving, immersing in a light etchant, and measuring the oxygen precipitate density by optical microscope observation of the cleavage plane, it is 5.0 × 10 ⁹ / cm ³ or more. Was confirmed.

  According to the SIMOX substrate of the present invention and the method of manufacturing the same, defects such as pits generated in the silicon active layer on the surface are as small as those of the bonded SOI substrate or the SIMOX substrate having an epitaxial layer formed on the surface. It has sufficient BMD with gettering action. In addition, the manufacturing process or manufacturing cost does not change significantly from normal SIMOX. As a result, it can be widely used as a semiconductor substrate for which higher performance is required in the future.

A diagram schematically illustrating the general relationship between the pulling speed and the position of occurrence of crystal defects when pulling a silicon single crystal, with the defect distribution in the cross section of the single crystal grown by gradually lowering the pulling speed. is there. A growth apparatus having a hot zone structure in which the temperature gradient in the pulling direction of the single crystal immediately after solidification is smaller in the crystal peripheral part (Ge) than in the crystal central part (Gc) (Gc> Ge), that is, for producing a defect-free wafer It is the figure explaining the single crystal pulled up with the single crystal growth apparatus by the same method as FIG. It is a figure which shows the relationship between the initial stage oxygen concentration in a silicon wafer when performing high temperature oxidation heat processing, and the oxygen increase amount by heat processing. It is the figure which showed distribution of the pit defect observed on the SIMOX substrate surface.

Claims (8)

An SOI substrate formed by SIMOX a wafer obtained from a silicon single crystal manufactured by the Czochralski method,
A region where the OSF ring generation position is on the outer periphery of the crystal, a region where the OSF ring generation position exists from the center to the outer periphery, or a region where the OSF ring disappears,
A SIMOX substrate, wherein defects generated in a surface silicon active layer due to the OSF or Grown-in defects are reduced. An SOI substrate formed by SIMOX a wafer obtained from a silicon single crystal manufactured by the Czochralski method,
A region where the OSF ring generation position is on the outer periphery of the crystal, a region where the OSF ring generation position exists from the center to the outer periphery, or a region where the OSF ring disappears,
A SIMOX substrate characterized in that a wafer that is detected as a Grown-in defect by evaluation by a Cu decoration method and is not detected as a flow pattern by selective etching is used as the substrate.   3. The SIMOX substrate according to claim 1, wherein the maximum size of the grown-in defect of the substrate is 0.09 [mu] m or less. The SIMOX substrate according to claim 1, wherein a wafer having an initial oxygen concentration of 6.5 × 10 ¹⁷ atoms / cm ³ (old ASTM) or more is used.   5. The SIMOX substrate according to claim 1, wherein an oxygen precipitate serving as a gettering site is formed inside the substrate.   Oxygen ions are implanted into a wafer heated to 300 to 550 ° C. once or a plurality of times, and then heated to 1300 ° C. or higher to form an insulating oxide film therein, thereby forming OSF and Growth in the SOI layer. The method for manufacturing a SIMOX substrate according to claim 1, wherein -in defects are eliminated.   The wafer is heated to 300 to 550 ° C. and then implanted with oxygen ions. Further, oxygen ions are implanted at a temperature of room temperature to 300 ° C., and then heated to 1300 ° C. or more to form an insulating oxide film inside. A method for producing a SIMOX substrate according to any one of claims 1 to 5. 6. A heat treatment at 400 to 900 [deg.] C. and a heat treatment at 900 to 1250 [deg.] C. are performed after oxygen ions are implanted to form an insulating oxide film therein. The manufacturing method of the SIMOX board | substrate in any one of.

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