JP2005286282A - Method of manufacturing simox substrate and simox substrate resulting from same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently capture heavy metal contamination into a substrate during a device process. <P>SOLUTION: The method includes the steps of: performing oxygen ion implantation into a wafer; forming a buried oxidation layer by performing first heat treatment on the wafer at the temperature of 1,300 to 1,390°C in a predetermined gas atmosphere and forming an SOI layer on a surface of the wafer, wherein the wafer before the oxygen ion implantation has an oxygen concentration of 8×10<SP>17</SP>to 1.8×10<SP>18</SP>atoms/cm<SP>3</SP>(former ASTM), and the buried oxidation layer is formed all over the surface of the wafer; forming an oxygen deposition core in a bulk layer lower than a defective aggregate layer formed just under an embedded oxidation layer by performing second heat treatment on the wafer to which the first heat treatment is applied, for 1 to 96 hours at the temperature of 400 to 900°C in the predetermined gas atmosphere; and developing the formed oxygen deposition core into an oxygen sludge by performing third heat treatment on the wafer to which the second heat treatment is applied, for 1 to 96 hours at the temperature of 900 to 1250°C higher than that of the second heat treatment in the predetermined gas atmosphere. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a SIMOX (Separation) among SOI (Silicon-On-Insulator) substrates in which a single crystal silicon layer (hereinafter referred to as SOI layer) is formed in a silicon single crystal body through a buried oxide layer (Buried Oxide). by Implanted Oxygen) technology and a SIMOX substrate obtained by the method. More specifically, the present invention relates to a method for manufacturing a SIMOX substrate capable of efficiently capturing heavy metal contamination in a device process inside the substrate, and a SIMOX substrate obtained by the method.

The SOI substrate (1) can reduce the parasitic capacitance between the element and the substrate, so that the device operation speed can be increased, (2) it has excellent radiation withstand voltage, and (3) it is highly integrated due to easy dielectric separation. It has excellent characteristics such as (4) improved latch-up resistance characteristics. There are two main methods for manufacturing SOI substrates. One method is a bonding method in which an active wafer to be thinned and a supporting wafer are bonded to each other, and the other method is to implant oxygen ions from the wafer surface into a region of a predetermined depth from the wafer surface. This is a SIMOX method for forming a buried oxide layer. In particular, the SIMOX method is expected as an effective method in the future because the number of manufacturing steps is small.
As a method for manufacturing a SIMOX substrate, an oxygen ion implantation step in which one main surface of a silicon single crystal substrate is mirror-finished and oxygen ions are implanted from the mirror-finished surface to a predetermined depth in the substrate by implantation, The substrate includes a high temperature heat treatment process in which a buried oxide layer is formed inside the substrate by performing high temperature heat treatment in an oxidizing atmosphere on the substrate into which ions are implanted. Specifically, the silicon single crystal substrate maintained at a temperature of 500 ° C. to 650 ° C., implanting oxygen atom ion or an oxygen molecule ion ¹⁰¹⁷ about ¹⁸ / cm ² from the substrate surface to a predetermined depth . Subsequently, the silicon substrate into which oxygen ions were implanted was put into a heat treatment furnace maintained at a temperature of 500 ° C. to 700 ° C., and the temperature was gradually raised so as not to generate slip, and a temperature of about 1300 ° C. to 1390 ° C. Apply heat treatment for about an hour. Oxygen ions implanted into the substrate by this high temperature heat treatment react with silicon to form a buried oxide layer inside the substrate.

On the other hand, in the device manufacturing process, as gettering technology for removing metal from the substrate surface that directly affects device characteristics, a method of distorting the back surface of the substrate by sandblasting, a method of depositing a polycrystalline silicon film on the back surface of the substrate, There is an external gettering method such as a method of injecting high-concentration phosphorus into the backside of the substrate, but an internal gettering method that uses the strain field of crystal defects caused by oxygen precipitates deposited inside the silicon substrate ( Intrinsic Gettering) is excellent in mass production and is partly used for mass production as a clean gettering method.
However, since a SIMOX substrate generally requires a high-temperature heat treatment at around 1300 ° C. after oxygen ion implantation in order to form a buried oxide layer inside the substrate, an internal gettering sink is formed in the bulk layer by this high-temperature heat treatment. It was said that it was difficult to form certain oxygen precipitates.

  As a measure for solving the above-mentioned problems, after implanting oxygen ions into a silicon single crystal substrate, the substrate is subjected to heat treatment at a temperature of 1200 to 1300 ° C. for 6 to 12 hours in a hydrogen atmosphere or a nitrogen atmosphere containing a small amount of oxygen. There has been proposed a method for manufacturing a semiconductor substrate, in which a buried oxide layer is formed by applying a heat treatment stepwise or continuously from a low temperature to a high temperature (see, for example, Patent Document 1). As a specific heat treatment condition shown in Patent Document 1, a stepwise heat treatment method is started from 500 ° C., and is gradually increased in a step of 50 to 100 ° C., and the final temperature is increased to 850 ° C., continuously. Starting from 500 ° C. with a gradient of 0.2-1.0 ° C./min and a final temperature of 850 ° C. However, since heat treatment at about 1300 ° C. is performed to form a buried oxide layer of the SIMOX substrate, oxygen precipitation nuclei are reduced and eliminated due to crystal pulling. However, since the growth of oxygen precipitates is suppressed, a sufficient gettering effect was not obtained when the final temperature reached 850 ° C.

Further, a SIMOX substrate having a region in which a buried oxide layer is not partially formed and having a structure in which gettering means due to crystal defects or crystal distortion is provided on a silicon single crystal substrate bulk or a silicon single crystal substrate back surface, and A manufacturing method has been proposed (see, for example, Patent Document 2). In Patent Document 2, the buried oxide layer is formed in the vicinity of the surface layer in a piecewise manner, and oxygen precipitation nuclei are formed in a heat treatment condition for gettering in the range of 500 to 900 ° C., and the density is 10 ⁵ / cm ^3. in the range of 10 ⁹ / cm ^3, it is described that may be the precipitation nuclei are grown precipitates in the range of 1000 to 1150 ° C. as a second heat treatment.

However, in the examples, SIMOX according to the prior art, that is, SIMOX in which a buried oxide film is grown on the entire surface of the wafer is used as a reference sample to evaluate the amount of crystal defects generated on the substrate surface due to quantitative contamination of heavy metals. In the present embodiment, surface defects are hardly observed, whereas in conventional SIMOX, pits and stacking faults of 10 ⁵ to 10 ⁶ pieces / cm ² are observed. That is, Patent Document 1 also means that a complete gettering technique has not been established.
JP-A-7-193072 (Claims 1 to 3) JP-A-5-82525 (Claims 1, 2, 4, and 5, paragraphs [0019] to paragraph [0023]) J. Electrochem. Soc., 142, 2059, (1995)

  On the other hand, it is disclosed that a defect assembly layer having a thickness of about 200 nm is inevitably formed immediately below the buried oxide layer as a feature when manufacturing a SIMOX substrate, and this defect assembly layer has a gettering effect. (For example, refer nonpatent literature 1.). That is, based on the contents disclosed in Non-Patent Document 1, when heavy metal contamination occurs suddenly in the manufacturing process of the SIMOX substrate, the oxygen precipitates of the SIMOX substrate shown in Patent Document 1 and Patent Document 2 are If a sufficient gettering effect cannot be obtained, it is conceivable that heavy metals are also trapped in the defect assembly layer immediately below the buried oxide layer.

  In recent years, there has been a demand for thinning of the SOI layer of the SIMOX substrate, so that the heavy metal contamination region trapped in the defect assembly layer immediately below the buried oxide layer may affect the device characteristics. It has been necessary to design a SIMOX substrate having a gettering source that has no influence and can efficiently capture sudden heavy metal contamination in the process.

  An object of the present invention is to provide a method for manufacturing a SIMOX substrate and a SIMOX substrate obtained by the method, which can reduce the concentration of heavy metals in a defect assembly layer and efficiently capture heavy metals inside the bulk layer.

As shown in FIGS. 1A to 1E, the invention according to claim 1 includes a step of implanting oxygen ions into the silicon wafer 11, and a mixed gas of oxygen and an inert gas. A process of forming a buried oxide layer 12 in a region having a predetermined depth from the surface of the wafer 11 and forming an SOI layer 13 on the wafer surface on the buried oxide layer 12 by performing a first heat treatment at 1300 to 1390 ° C. in an atmosphere. Improvement of a method for manufacturing a SIMOX substrate.
The characteristic structure is that the silicon wafer 11 before the oxygen ion implantation has an oxygen concentration of 8 × 10 ^{17 to} 1.8 × 10 ¹⁸ atoms / cm ³ (former ASTM), and the buried oxide layer 12 extends over the entire surface of the wafer. The formed first heat-treated wafer is subjected to a second heat treatment at 400 to 900 ° C. for 1 to 96 hours in an atmosphere of oxygen, nitrogen, argon, hydrogen, or a mixed gas thereof, thereby forming the wafer directly under the buried oxide layer 12. The step of forming oxygen precipitation nuclei 14b in the bulk layer 14 below the defect assembly layer 14a and the second heat-treated wafer in an atmosphere of oxygen, nitrogen, argon, hydrogen, or a mixed gas thereof are 900 to 900 to higher than the second heat treatment temperature. By performing the third heat treatment at 1250 ° C. for 1 to 96 hours, the oxygen precipitation nuclei 14b formed in the bulk layer 14 are grown into the oxygen precipitates 14c. It is in place and a step.
In the invention according to claim 1, the bulk layer 14 below the defect assembly layer 14a has a gettering source made of oxygen precipitates 14c, and the density of the oxygen precipitates 14c is 1 × 10 ⁸ to 1 × 10 ¹² / It is possible to obtain a SIMOX substrate that is cm ³ and the size of the oxygen precipitates 14c is 50 nm or more.

  The invention according to claim 2 is the invention according to claim 1, wherein the second heat treatment is performed at a rate of 0.1 to 5.0 ° C./min in a partial range or all ranges of 400 ° C. to 900 ° C. It is carried out within a range of 1 to 96 hours by heating, and the third heat treatment is performed by raising the temperature at a rate of 0.1 to 20 ° C./min in a partial range or all ranges from 900 ° C. to 1250 ° C. It is a manufacturing method performed within the range of -96 hours.

According to a third aspect of the present invention, a wafer is obtained by first implanting oxygen ions into the silicon wafer 11 and subjecting the wafer 11 to a first heat treatment at 1300 to 1390 ° C. in a mixed gas atmosphere of oxygen and inert gas. 11 forming an embedded oxide layer 12 in a region having a predetermined depth from the surface, and forming an SOI layer 13 on the wafer surface on the embedded oxide layer 12.
The characteristic structure is that the silicon wafer 11 before the oxygen ion implantation has an oxygen concentration of 8 × 10 ^{17 to} 1.8 × 10 ¹⁸ atoms / cm ³ (former ASTM), and the buried oxide layer 12 extends over the entire surface of the wafer. Alternatively, after the partially formed and first heat-treated wafer is held at 1050 to 1350 ° C. for 1 to 900 seconds and then subjected to a rapid heat treatment in which the temperature is lowered at a temperature lowering rate of 10 ° C./second or more, the buried oxide layer 12 A step of injecting vacancies in the lower bulk layer 14 and a second heat treatment of the rapidly heat-treated wafer in an atmosphere of oxygen, nitrogen, argon, hydrogen or a mixed gas thereof at 500 to 1000 ° C. for 1 to 96 hours, And a step of forming oxygen precipitation nuclei 14b in the bulk layer 14 below the defect assembly layer 14a formed immediately below the buried oxide layer 12. .
In the invention according to claim 3, when the SIMOX substrate that has been subjected to the second heat treatment is heat-treated in the device manufacturing process of the semiconductor device manufacturer, the oxygen precipitation nuclei grow into oxygen precipitates and have an IG effect over the entire wafer surface. Become.

The invention according to claim 4 is the invention according to claim 3, wherein the second heat-treated wafer is in an atmosphere of oxygen, nitrogen, argon, hydrogen or a mixed gas thereof at 900 to 1250 ° C. higher than the second heat treatment temperature. The manufacturing method further includes the step of growing the oxygen precipitation nuclei 14b formed in the bulk layer 14 into the oxygen precipitates 14c by performing the third heat treatment for 1 to 96 hours.
The invention according to claim 5 is the invention according to claim 3, wherein the second heat treatment is performed at a rate of 0.1 to 5.0 ° C./min in a partial range or all ranges of 500 ° C. to 1000 ° C. It is a manufacturing method performed within a range of 1 to 96 hours by heating.
The invention according to claim 6 is the invention according to claim 4, wherein the third heat treatment is performed at a rate of 0.1 to 20 ° C./min in a partial range or all ranges from 900 ° C. to 1250 ° C. This is a production method carried out within a range of 1 to 96 hours.

The invention according to claim 7 is a SIMOX substrate manufactured from the method according to any one of claims 1 to 6, as shown in FIG. 1 (e) or FIG. 2 (f). A buried oxide layer 12 formed in a region of a predetermined depth; an SOI layer 13 formed on the wafer surface on the buried oxide layer; a defect aggregation layer 14a formed immediately below the buried oxide layer 12; A bulk layer 14 below the layer 12, a bulk layer 14 below the defect assembly layer 14 a has a gettering source made of an oxygen precipitate 14 c, and the density of the oxygen precipitate 14 c is 1 × 10 ⁸ to 1 ×. The SIMOX substrate is characterized by 10 ¹² / cm ³ and the size of the oxygen precipitates 14 c being 50 nm or more.
In the invention according to claim 7, the bulk layer 14 below the defect assembly layer 14a has a gettering source made of oxygen precipitates 14c, and the density of the oxygen precipitates 14c is 1 × 10 ⁸ to 1 × 10 ¹² / Since it is cm ³ and the size of the oxygen precipitate 14c is 50 nm or more, it becomes a stronger gettering source than the defect assembly layer 14a. Therefore, most of the heavy metal contaminants conventionally captured in the defect assembly layer 14a are removed. It is possible to getter the oxygen precipitates 14c of the bulk layer 14 without trapping them.

In the SIMOX substrate of the present invention, the bulk layer below the defect assembly layer has a gettering source made of oxygen precipitates, and the density of oxygen precipitates is 1 × 10 ⁸ to 1 × 10 ¹² pieces / cm ³ , Since the size of the oxygen precipitate is 50 nm or more, it becomes a stronger gettering source than the defect assembly layer, so that the heavy metal capture concentration of the defect assembly layer can be reduced and the heavy metal can be efficiently captured inside the bulk layer. Can do.

Next, a first best mode for carrying out the present invention will be described with reference to the drawings.
The present invention relates to a SIMOX substrate in which oxygen ions are implanted into a silicon wafer and then a heat treatment is performed to form a buried oxide layer in a region at a predetermined depth from the wafer surface, and an SOI layer is formed on the wafer surface. is there. As shown in FIG. 1, the SIMOX substrate manufacturing method according to the present invention heat-treats the wafer 11 after oxygen ion implantation in three stages, and then removes the oxide films 11b and 11c formed on the surface of the wafer 11. To do. Each of these steps is shown below.

(1-1) Oxygen Ion Implantation Step First, as shown in FIG. 1A, a silicon wafer 11 is prepared and oxygen ions are implanted into the wafer 11. The prepared silicon wafer 11 before oxygen ion implantation is prepared having an oxygen concentration of 8 × 10 ^{17 to} 1.8 × 10 ¹⁸ atoms / cm ³ (former ASTM). The prepared silicon wafer may be an epitaxial wafer or an annealed wafer.

  Then, oxygen ions are implanted into the prepared silicon wafer 11. This oxygen ion implantation is performed by the same means as conventionally used. Then, oxygen ions are implanted from the surface of the wafer 11 into a region 11a having a predetermined depth so that the SOI layer 13 in the finally obtained SIMOX substrate has a thickness of 10 to 200 nm, preferably 20 to 100 nm. . If the thickness of the SOI layer 13 is less than 10 nm, it is difficult to control the thickness of the SOI layer 13, and if the thickness of the SOI layer 13 exceeds 200 nm, it is difficult to accelerate the oxygen ion implanter.

(1-2) First Heat Treatment Step Next, as shown in FIG. 1B, the wafer 11 into which oxygen ions have been implanted is subjected to a first treatment at a temperature of 1300 to 1390 ° C. in a mixed gas atmosphere of oxygen and inert gas. 1 heat treatment. Examples of the inert gas include argon gas and nitrogen gas. Therefore, the gas atmosphere of the first heat treatment is preferably a mixed gas of oxygen and argon or a mixed gas of oxygen and nitrogen. And it is preferable that the heat processing time of this 1st heat processing is 1 to 20 hours, Preferably it is 10 to 20 hours.
By this first heat treatment, oxide films 11b and 11c are formed on the front and back surfaces of the wafer 11, and a buried oxide layer 12 is formed on the entire surface of the wafer 11 in a region 11a having a predetermined depth from the front surface of the wafer 11. Further, an SOI layer 13 is formed between the front-side oxide film 11 b and the buried oxide layer 12. Further, a defect assembly layer 14a is inevitably formed immediately below the buried oxide layer 12.

(1-3) Second Heat Treatment Step Next, as shown in FIG. 1C, the wafer 11 subjected to the first heat treatment is left with the oxide films 11b and 11c left or with the oxide films 11b and 11c removed. The second heat treatment is performed in an atmosphere of oxygen, nitrogen, argon, hydrogen, or a mixed gas thereof. It is preferable to perform the second heat treatment with the oxide films 11b and 11c left, particularly in a non-oxidizing gas atmosphere because the thickness of the SOI layer 13 does not decrease and variation does not occur. The reason for this is that when the second heat treatment is first performed in an oxidizing gas atmosphere, the oxide films 11b and 11c are further grown to consume silicon on the wafer surface, and secondly in a hydrogen or argon gas atmosphere. This is because if the second heat treatment is performed, the SOI layer 13 is etched. On the other hand, when the thickness of the SOI layer 13 is relatively large, the SOI layer 13 having a predetermined thickness can be obtained even if the thickness of the SOI layer 13 is reduced, so that the oxide films 11b and 11c are removed. A second heat treatment may be performed. The gas atmosphere of the second heat treatment is preferably nitrogen gas, argon gas, nitrogen added with a trace amount of oxygen, or argon gas.

  Moreover, 2nd heat processing conditions are performed for 1 to 96 hours at the temperature of 400-900 degreeC. The reason why the second heat treatment temperature is specified within the range of 400 to 900 ° C. is that if it is less than the lower limit value, the nucleation temperature is too low and a long heat treatment is required, and if the upper limit value is exceeded, oxygen precipitation nucleation does not occur. It is. The second heat treatment time is defined within the range of 1 to 96 hours because if it is less than the lower limit, the time for forming oxygen precipitation nuclei is too short. This is because it occurs. The second heat treatment is more preferably performed at a temperature of 500 to 800 ° C. for 4 to 35 hours. The second heat treatment is performed by raising the temperature at a rate of 0.1 to 5.0 ° C./min, preferably 0.1 to 1.0 ° C./min in a partial range or all ranges of 400 ° C. to 900 ° C. The time may be 1 to 96 hours, preferably 4 to 35 hours. By performing this second heat treatment, oxygen precipitation nuclei 14 b are formed in the bulk layer 14 below the defect assembly layer 14 a formed immediately below the buried oxide layer 12.

(1-4) Third Heat Treatment Step Next, as shown in FIG. 1D, the second heat-treated wafer 11 is subjected to a third heat treatment. This third heat treatment is performed in an atmosphere of oxygen, nitrogen, argon, hydrogen or a mixed gas thereof at 900 to 1250 ° C., which is higher than the second heat treatment temperature, for 1 to 96 hours. The gas atmosphere of the third heat treatment is preferably nitrogen gas, argon gas, nitrogen added with a trace amount of oxygen, or argon gas. The reason why the third heat treatment temperature is set within the range of 900 to 1250 ° C. is that if it is less than the lower limit value, the growth of oxygen precipitation nuclei does not occur sufficiently, and if it exceeds the upper limit value, the problem of dissolution of oxygen precipitates occurs. . Further, the reason why the third heat treatment time is defined within the range of 1 to 96 hours is that the growth of oxygen precipitates is not sufficient if it is less than the lower limit value, and if the upper limit value is exceeded, the problem of deterioration in productivity occurs. The third heat treatment is preferably performed at 1000 to 1200 ° C. for 8 to 24 hours. Furthermore, the third heat treatment is performed at a rate of 0.1 to 20 ° C./min in a partial range or all range of 900 ° C. to 1250 ° C., preferably 1 to 96 hours by raising the temperature at 1 to 5 ° C./min. Preferably, it may be performed within a range of 8 to 24 hours. By performing the third heat treatment, the oxygen precipitation nuclei 14b formed in the bulk layer 14 can be grown on the oxygen precipitates 14c.

(1-5) Oxide Film 11b, 11c Removal Step As shown in FIG. 1E, the oxide film 11b, 11c on the front and back surfaces of the wafer 11 that has been subjected to the third heat treatment is removed with hydrofluoric acid or the like. As a result, the buried oxide layer 12 formed at a predetermined depth from the wafer surface, the SOI layer 13 formed on the wafer surface on the buried oxide layer, and the defect set formed immediately below the buried oxide layer 12 A bulk layer 14 below the buried oxide layer 12, a bulk layer 14 below the defect assembly layer 14 a has a gettering source made of oxygen precipitates 14 c, and the density of the oxygen precipitates 14 c is 1 A SIMOX substrate is obtained in which the number is 10 ⁸ to 1 × 10 ¹² pieces / cm ³ and the size of the oxygen precipitate 14 c is 50 nm or more.

Since this SIMOX substrate has oxygen precipitates 14c having a density of 1 × 10 ⁸ to 1 × 10 ¹² pieces / cm ³ and a size of 50 nm or more in the bulk layer 14 below the defect assembly layer 14a, the device process The sudden heavy metal contamination inside can be efficiently captured by the oxide precipitate 14c. Further, since this oxide precipitate 14c becomes a stronger gettering source than the defect aggregate layer 14a, heavy metal contaminants that have been trapped in the defect aggregate layer 14a can be gettered to the oxygen precipitate 14c of the bulk layer 14. it can. As a result, for example, when the heavy metal concentration is 1 × 10 ¹¹ to 1 × 10 ¹² pieces / cm ² and forcibly contaminated with heavy metal so as to become a substrate, the concentration of heavy metals captured by the defect assembly layer 14a is 5 × 10 ⁹ pieces. / Cm ² or less. Needless to say, the present invention can also be applied to a SIMOX substrate in which a buried oxide layer is partially formed.

Next, a second best mode for carrying out the present invention will be described with reference to the drawings.
The present invention relates to a SIMOX substrate in which oxygen ions are implanted into a silicon wafer and then a heat treatment is performed to form a buried oxide layer in a region at a predetermined depth from the wafer surface, and an SOI layer is formed on the wafer surface. is there. As shown in FIG. 2, the SIMOX substrate manufacturing method according to the present invention heat-treats the wafer 11 after the oxygen ions are implanted in three or four stages, and then forms an oxide film 11b formed on the surface of the wafer 11; 11c is removed. Each of these steps is shown below.

(2-1) Oxygen Ion Implantation Step First, as shown in FIG. 2A, a silicon wafer 11 is prepared and oxygen ions are implanted into the wafer 11. The prepared silicon wafer 11 before oxygen ion implantation is prepared having an oxygen concentration of 8 × 10 ^{17 to} 1.8 × 10 ¹⁸ atoms / cm ³ (former ASTM). The prepared silicon wafer may be an epitaxial wafer or an annealed wafer.

  Then, oxygen ions are implanted into the prepared silicon wafer 11. This oxygen ion implantation is performed by the same means as conventionally used. Then, oxygen ions are implanted from the surface of the wafer 11 into a region 11a having a predetermined depth so that the SOI layer 13 in the finally obtained SIMOX substrate has a thickness of 10 to 200 nm, preferably 20 to 100 nm. . If the thickness of the SOI layer 13 is less than 10 nm, it is difficult to control the thickness of the SOI layer 13, and if the thickness of the SOI layer 13 exceeds 200 nm, it is difficult to accelerate the oxygen ion implanter.

  It should be noted that oxygen ions are implanted into the silicon wafer 11 after a mask or the like is partially formed at a desired position on the surface of the silicon wafer 11, so that oxygen ions are introduced into the wafer below the portion where the mask is not formed. Since oxygen ions are not implanted into the inside of the wafer below the portion where the mask is formed, the buried oxide layer 12 is partially formed only below the portion where the mask is not formed by applying the first heat treatment that follows. Is done.

(2-2) First Heat Treatment Step Next, as shown in FIG. 2B, the wafer 11 into which oxygen ions have been implanted is subjected to a first treatment at a temperature of 1300 to 1390 ° C. in a mixed gas atmosphere of oxygen and inert gas. 1 heat treatment. Examples of the inert gas include argon gas and nitrogen gas. Therefore, the gas atmosphere of the first heat treatment is preferably a mixed gas of oxygen and argon or a mixed gas of oxygen and nitrogen. And it is preferable that the heat processing time of this 1st heat processing is 1 to 20 hours, Preferably it is 10 to 20 hours.
By this first heat treatment, oxide films 11b and 11c are formed on the front and back surfaces of the wafer 11, and a buried oxide layer 12 is formed on the entire surface of the wafer 11 in a region 11a having a predetermined depth from the front surface of the wafer 11. Further, when oxygen ions are partially implanted into a region having a predetermined depth from the surface of the wafer 11 using a mask or the like, the buried oxide layer 12 is partially formed. Further, an SOI layer 13 is formed between the front-side oxide film 11 b and the buried oxide layer 12. Further, a defect assembly layer 14a is inevitably formed immediately below the buried oxide layer 12.

(2-3) Rapid Heat Treatment Step Next, as shown in FIG. 2C, the first heat-treated wafer is held at 1050 ° C. to 1350 ° C. for 1 second to 900 seconds, and then the temperature lowering rate is 10 ° C./second or more. Apply rapid heat treatment to lower the temperature. The gas atmosphere for this rapid heat treatment is preferably an argon gas or ammonia-containing gas atmosphere.

  The rapid heat treatment conditions are maintained at 1050 ° C. to 1350 ° C. for 1 second to 900 seconds. The reason why the rapid heat treatment temperature is defined within the range of 1050 ° C. to 1350 ° C. is that if it is less than the lower limit value, a sufficient amount of vacancies cannot be injected into the wafer to promote the formation of oxygen precipitation nuclei. This is because slip dislocations are generated in the wafer during heat treatment, causing troubles during device fabrication. A preferable heat treatment temperature is 1100 to 1300 ° C. In addition, if the holding time is set to 1 second to 900 seconds, if it is less than the lower limit value, the time required to reach the desired heat treatment temperature differs in the in-plane and depth directions of the wafer, which may cause variations in quality. This is because of concern. The reason why the upper limit is specified is that slip reduction and productivity are taken into consideration. A preferred holding time is 10 to 60 seconds. By maintaining the rapid heat treatment temperature for a predetermined time, vacancies are injected into the wafer. To keep the injected vacancies inside the wafer, the cooling rate when cooling the wafer is an important role. Will be fulfilled. It is considered that the injected vacancies disappear when reaching the wafer surface, the concentration decreases near the outermost surface, and the diffusivity of the vacancies from the inside to the surface occurs due to the concentration difference caused thereby. For this reason, if the cooling rate is slow, the time for staying at a lower temperature becomes longer, and the outward diffusion proceeds accordingly, once the vacancies injected by the high-temperature RTA heat treatment are reduced, and oxygen precipitation nuclei are formed. It is considered that a sufficient amount cannot be secured.

  Therefore, after performing a predetermined holding, the temperature is decreased at a temperature decrease rate of 10 ° C./second or more. The reason for setting the temperature lowering rate to 10 ° C./second or more is that if it is less than the lower limit value, the effect of suppressing the disappearance of pores cannot be obtained. The reason why the upper limit was not set is that the effect is hardly changed if it exceeds 10 ° C./second. However, if the temperature lowering rate is set too high, the temperature uniformity in the wafer surface is deteriorated during cooling and slipping occurs. Therefore, it is desirable to control the temperature lowering rate to 10 to 100 ° C./second in consideration of productivity. A more preferable cooling rate is 15 to 50 ° C./second. By performing this rapid heat treatment, vacancies 15 are injected into the bulk layer 14 below the buried oxide layer 12. By this rapid heat treatment, in-plane uniformity of the oxygen precipitate density distribution in the wafer surface is ensured, and the certainty of oxygen precipitate growth is improved even for a silicon wafer having a low oxygen concentration. If this rapid heat treatment is not performed, the oxygen precipitate density distribution in the wafer surface may not be uniform even if subsequent steps are performed.

(2-4) Second Heat Treatment Step Next, as shown in FIG. 2 (d), oxygen is applied to the wafer 11 subjected to the rapid heat treatment while leaving the oxide films 11b and 11c or removing the oxide films 11b and 11c. Second heat treatment is performed in an atmosphere of nitrogen, argon, hydrogen, or a mixed gas thereof. It is preferable to perform the second heat treatment with the oxide films 11b and 11c left, particularly in a non-oxidizing gas atmosphere because the thickness of the SOI layer 13 does not decrease and does not vary. The reason for this is that when the second heat treatment is first performed in an oxidizing gas atmosphere, the oxide films 11b and 11c are further grown to consume silicon on the wafer surface, and secondly in a hydrogen or argon gas atmosphere. This is because if the second heat treatment is performed, the SOI layer 13 is etched. On the other hand, when the thickness of the SOI layer 13 is relatively large, the SOI layer 13 having a predetermined thickness can be obtained even if the thickness of the SOI layer 13 is reduced, so that the oxide films 11b and 11c are removed. A second heat treatment may be performed. The gas atmosphere of the second heat treatment is preferably nitrogen gas, argon gas, nitrogen added with a trace amount of oxygen, or argon gas.

  Moreover, 2nd heat processing conditions are performed for 1 to 96 hours at the temperature of 500-1000 degreeC. The reason why the second heat treatment temperature is defined within the range of 500 to 1000 ° C. is that if the temperature is less than the lower limit, the nucleation temperature is too low and a long heat treatment is required, and if the upper limit is exceeded, oxygen precipitation nucleation does not occur. It is. The second heat treatment time is defined within the range of 1 to 96 hours because if it is less than the lower limit, the time for forming oxygen precipitation nuclei is too short. This is because it occurs. The second heat treatment is more preferably performed at a temperature of 500 to 800 ° C. for 4 to 35 hours. The second heat treatment is performed by raising the temperature at a rate of 0.1 to 5.0 ° C./min, preferably 0.1 to 1.0 ° C./min in a partial range or all ranges of 500 ° C. to 1000 ° C. The time may be 1 to 96 hours, preferably 4 to 35 hours. By performing this second heat treatment, oxygen precipitation nuclei 14 b are formed in the bulk layer 14 below the defect assembly layer 14 a formed immediately below the buried oxide layer 12. When the SIMOX substrate that has been subjected to the second heat treatment is heat-treated in the device manufacturing process of the semiconductor device manufacturer, the oxygen precipitation nuclei grow into oxygen precipitates and have an IG effect over the entire surface of the wafer.

(2-5) Third Heat Treatment Step Next, as shown in FIG. 2E, the second heat-treated wafer 11 is subjected to a third heat treatment. This third heat treatment is performed in an atmosphere of oxygen, nitrogen, argon, hydrogen or a mixed gas thereof at 900 to 1250 ° C., which is higher than the second heat treatment temperature, for 1 to 96 hours. The gas atmosphere of the third heat treatment is preferably nitrogen gas, argon gas, nitrogen added with a trace amount of oxygen, or argon gas. The reason why the third heat treatment temperature is set within the range of 900 to 1250 ° C. is that if it is less than the lower limit value, the growth of oxygen precipitation nuclei does not occur sufficiently, and if it exceeds the upper limit value, the problem of dissolution of oxygen precipitates occurs. . Further, the reason why the third heat treatment time is defined within the range of 1 to 96 hours is that the growth of oxygen precipitates is not sufficient if it is less than the lower limit value, and if the upper limit value is exceeded, the problem of deterioration in productivity occurs. The third heat treatment is preferably performed at 1000 to 1200 ° C. for 8 to 24 hours. Further, the third heat treatment is performed at a rate of 0.1 to 20 ° C./min in a partial range or all range of 900 ° C. to 1250 ° C., preferably 1 to 96 hours by raising the temperature at 1 to 5 ° C./min. Preferably, it may be performed within a range of 8 to 24 hours. By performing the third heat treatment, the oxygen precipitation nuclei 14b formed in the bulk layer 14 can be grown on the oxygen precipitates 14c.

(2-6) Oxide Films 11b and 11c Removal Step As shown in FIG. 2F, the oxide film 11b and 11c on the front and back surfaces of the wafer 11 subjected to the third heat treatment are removed with hydrofluoric acid or the like. As a result, the buried oxide layer 12 formed at a predetermined depth from the wafer surface, the SOI layer 13 formed on the wafer surface on the buried oxide layer, and the defect set formed immediately below the buried oxide layer 12 A bulk layer 14 below the buried oxide layer 12, a bulk layer 14 below the defect assembly layer 14 a has a gettering source made of oxygen precipitates 14 c, and the density of the oxygen precipitates 14 c is 1 A SIMOX substrate is obtained in which the number is 10 ⁸ to 1 × 10 ¹² pieces / cm ³ and the size of the oxygen precipitate 14 c is 50 nm or more.

Since this SIMOX substrate has oxygen precipitates 14c having a density of 1 × 10 ⁸ to 1 × 10 ¹² pieces / cm ³ and a size of 50 nm or more in the bulk layer 14 below the defect assembly layer 14a, the device process The sudden heavy metal contamination inside can be efficiently captured by the oxide precipitate 14c. Further, since this oxide precipitate 14c becomes a stronger gettering source than the defect aggregate layer 14a, heavy metal contaminants that have been trapped in the defect aggregate layer 14a can be gettered to the oxygen precipitate 14c of the bulk layer 14. it can. As a result, for example, when the heavy metal concentration is 1 × 10 ¹¹ to 1 × 10 ¹² pieces / cm ² and forcibly contaminated with heavy metal so as to become a substrate, the concentration of heavy metals captured by the defect assembly layer 14a is 5 × 10 ⁹ pieces. / Cm ² or less.

Next, examples of the present invention will be described in detail together with comparative examples.
<Example 1>
First, as shown in FIG. 1A, a silicon ingot having an oxygen concentration of 1.3 × 10 ¹⁸ atoms / cm ³ (former ASTM) and a specific resistance of 20 Ω · cm grown by the CZ method was cut to a predetermined thickness. A CZ silicon wafer was prepared. Next, this wafer was heated to a temperature of 550 ° C., and in this state, oxygen ions were implanted into a predetermined region of the silicon wafer (for example, a region of about 0.4 μm from the substrate surface) under the following conditions.

Accelerating voltage: 180 keV
Beam current: 50 mA
Dose amount: 4 × 10 ¹⁷ / cm ²
After ion implantation, SC-1 and SC-2 cleaning was performed on the wafer surface. Subsequently, as shown in FIG. 1 (b), the wafer 11 is placed in a heat treatment furnace and kept at a constant temperature of 1350 ° C. for 4 hours in an Ar gas atmosphere having an oxygen partial pressure of 0.5%, and then the furnace atmosphere. A first heat treatment was performed in which the oxygen partial pressure was increased to 70% and maintained for 4 hours. As shown in FIG. 1C, the first heat-treated wafer is continuously raised from 500 ° C. to 850 ° C. at 1.0 ° C./min in a 1% oxygen atmosphere with the oxide films 11b and 11c on the surface remaining. After the heating, a second heat treatment was performed by holding at 850 ° C. for 1 hour. As shown in FIG. 1 (d), the second heat-treated wafer 11 is heated from 1850C to 1100C at a rate of 5.0C / min in a 1% oxygen atmosphere, and then at 1100C. A third heat treatment was performed for 8 hours. Thereafter, the temperature of the third heat-treated wafer was lowered to 700 ° C. at a temperature lowering rate of 3.0 ° C./min. The oxide films 11b and 11c on the front and back surfaces of the wafer after the heat treatment were removed with an HF solution to obtain a SIMOX substrate. This SIMOX substrate was referred to as Example 1.

<Example 2>
First, as shown in FIG. 1 (a), the oxygen concentration grown by the CZ method is 1.4 × 10 ¹⁸ atoms / cm ³ (former ASTM), and the nitrogen concentration is 4.0 × 10 ¹⁴ atoms / cm ³ (former ASTM). A CZ silicon wafer cut out to a predetermined thickness from a silicon ingot having a specific resistance of 10 Ω · cm was prepared. Next, this wafer was heated to a temperature of 550 ° C., and in this state, oxygen ions were implanted into a predetermined region of the silicon wafer (for example, a region of about 0.4 μm from the substrate surface) under the following conditions.

Accelerating voltage: 180 keV
Beam current: 50 mA
Dose amount: 4 × 10 ¹⁷ / cm ²
After ion implantation, SC-1 and SC-2 cleaning was performed on the wafer surface. Subsequently, as shown in FIG. 1 (b), the wafer 11 is placed in a heat treatment furnace and kept at a constant temperature of 1350 ° C. for 4 hours in an Ar gas atmosphere having an oxygen partial pressure of 0.5%, and then the furnace atmosphere. A first heat treatment was performed in which the oxygen partial pressure was increased to 70% and maintained for 4 hours. As shown in FIG. 1C, the first heat-treated wafer is 0.5 ° C./600° C. to 700 ° C. in a 1% oxygen (argon base) atmosphere with the oxide films 11b and 11c on the surface remaining. After continuously raising the temperature in minutes, a second heat treatment was performed by holding at 700 ° C. for 1 hour. As shown in FIG. 1D, the second heat-treated wafer 11 is heated from 700 ° C. to 1000 ° C. at a rate of 5.0 ° C./min in a 1% oxygen atmosphere, and then at 1000 ° C. A third heat treatment was performed for 16 hours. Thereafter, the temperature of the third heat-treated wafer was lowered to 700 ° C. at a temperature lowering rate of 3.0 ° C./min. The oxide films 11b and 11c on the front and back surfaces of the wafer after the heat treatment were removed with an HF solution to obtain a SIMOX substrate. This SIMOX substrate was referred to as Example 2.

<Example 3>
A SIMOX substrate was obtained in the same manner as in Example 2 except that the second heat treatment was held at 700 ° C. for 4 hours. This SIMOX substrate was designated as Example 3.
<Example 4>
A SIMOX substrate was obtained in the same manner as in Example 2 except that the second heat treatment was held at 700 ° C. for 8 hours. This SIMOX substrate was referred to as Example 4.

<Example 5>
First, as shown in FIG. 1A, the oxygen concentration grown by the CZ method is 1.4 × 10 ¹⁸ atoms / cm ³ (former ASTM), and the carbon concentration is 2.02 × 10 ¹⁶ atoms / cm ³ (former ASTM). A CZ silicon wafer cut out to a predetermined thickness from a silicon ingot having a specific resistance of 10 Ω · cm was prepared. A 3 μm silicon epitaxial film was deposited on the surface of the CZ silicon wafer. Next, this wafer was heated to a temperature of 550 ° C., and in this state, oxygen ions were implanted into a predetermined region of the silicon wafer (for example, a region of about 0.4 μm from the substrate surface) under the following conditions.

Accelerating voltage: 180 keV
Beam current: 50 mA
Dose amount: 4 × 10 ¹⁷ / cm ²
After ion implantation, SC-1 and SC-2 cleaning was performed on the wafer surface. Subsequently, as shown in FIG. 1 (b), the wafer 11 is placed in a heat treatment furnace and kept at a constant temperature of 1350 ° C. for 4 hours in an Ar gas atmosphere having an oxygen partial pressure of 0.5%, and then the furnace atmosphere. A first heat treatment was performed in which the oxygen partial pressure was increased to 70% and maintained for 4 hours. As shown in FIG. 1C, the first heat-treated wafer was subjected to a second heat treatment that was held at 700 ° C. for 8 hours in a nitrogen atmosphere while leaving the oxide films 11b and 11c on the surface. As shown in FIG. 1D, the second heat-treated wafer 11 is heated from 700 ° C. to 1000 ° C. at a temperature rising rate of 5.0 ° C./min in a nitrogen atmosphere, and then at 1000 ° C. for 16 hours. A third heat treatment was performed. Thereafter, the temperature of the third heat-treated wafer was lowered to 700 ° C. at a temperature lowering rate of 3.0 ° C./min. The oxide films 11b and 11c on the front and back surfaces of the wafer after the heat treatment were removed with an HF solution to obtain a SIMOX substrate. This SIMOX substrate was referred to as Example 5.

<Comparative Example 1>
A SIMOX substrate was obtained in the same manner as in Example 1 except that the second heat treatment and the third heat treatment were not performed. This SIMOX substrate was referred to as Comparative Example 1.
<Comparative example 2>
Instead of the second heat treatment and the third heat treatment, SIMOX was performed in the same manner as in Example 1 except that heat treatment was started at 500 ° C. and continuously heated at 1.0 ° C./min until the final temperature reached 850 ° C. A substrate was obtained. This SIMOX substrate was referred to as Comparative Example 2.

<Comparison test 1>
After removing the surface oxide films 11b and 11c of each of the SIMOX substrates 10 of Examples 1 to 5 and Comparative Examples 1 and 2, the SOI layer 13, the buried oxide layer 12, and the defect assembly layer 14a immediately below the buried oxide layer of each SIMOX substrate. Were dissolved and recovered with an aqueous solution of nitric acid hydrofluoric acid, and ICP-MS measurement (Inductively Coupled Plasma-Mass Spectrometry) was performed on these recovered dissolved solutions, and iron, nickel, zinc and The heavy metal concentration for copper was measured. Moreover, the bulk layers 14 of Examples 1 to 5 and Comparative Examples 1 and 2 were all dissolved, and the heavy metal concentration in the dissolved solutions was measured.

  Regarding heavy metals other than nickel, that is, iron, zinc and copper, none of the SIMOX substrates of Examples 1 to 5 and Comparative Examples 1 and 2 were observed in the SOI layer, the buried oxide layer, the defect assembly layer and the bulk layer. Table 1 shows the nickel concentration results contained in each layer of the SIMOX substrates of Examples 1 to 5 and Comparative Examples 1 and 2, respectively.

As is clear from Table 1, in the SIMOX substrates of Comparative Examples 1 and ² , nickel of about 5.0 × 10 ¹⁰ atoms / cm ^{2 in} terms of surface concentration was observed in the SOI layer, the buried oxide layer, and the defect assembly layer. It was. On the other hand, the nickel concentration in the bulk layer was below the detection limit value. On the other hand, in the SIMOX substrates of Examples 1 to 5, the nickel concentration was below the detection limit value in the SOI layer, the buried oxide layer, and the defect assembly layer. The nickel concentration in the bulk layer is 2.6 × 10 ^{11 to} 4.8 × 10 ¹¹ atoms / cm ³ , and heavy metal impurities are reliably gettered by the oxygen precipitates formed in the bulk layer. understood.

<Comparison test 2>
The SIMOX substrates in Examples 1 to 5 and Comparative Examples 1 and 2 were each cleaved into two. Both the cleaved substrates were selectively etched with a Wright etchant. First, one substrate was observed with an optical microscope, and oxygen precipitates at a depth of 2 μm were measured from the surface of the substrate cleavage plane to determine the density. The density of oxygen precipitates in the SIMOX substrates of Comparative Examples 1 and 2 was 5 × 10 ⁷ pieces / cm ² or less. On the other hand, the oxygen precipitate density in the SIMOX substrates of Examples 1 to 5 was in the range of 1 × 10 ⁸ to 1 × 10 ¹² pieces / cm ³ . Further, a DZ layer (Denuded Zone) in which oxygen precipitates do not exist was present in the region immediately below the buried oxide layer to 10 μm.
Next, the other substrate was observed with an electron microscope to determine the size of oxygen precipitates. The SIMOX substrates of Comparative Examples 1 and 2 had an oxygen precipitate size of 50 nm or less, but the SIMOX substrates of Examples 1 to 5 were found to have most of the oxygen precipitate size of 50 nm or more.

<Comparison test 3>
A part of the sample obtained in Example 5 was measured with an FT-IR (Fourier transform infrared absorption spectroscopy) apparatus and the residual oxygen concentration after the heat treatment was measured. As a result, the residual oxygen concentration was 5 × 10 ¹⁷ atoms / cm ^3. However, there was no change in the amount of warpage before and after the oxygen precipitate growth heat treatment.

<Example 6>
First, as shown in FIG. 2A, a silicon ingot having an oxygen concentration of 1.0 × 10 ¹⁸ atoms / cm ³ (former ASTM) and a specific resistance of 20 Ω · cm grown by the CZ method was cut to a predetermined thickness. A CZ silicon wafer was prepared. Next, this wafer was heated to a temperature of 550 ° C., and in this state, oxygen ions were implanted into a predetermined region of the silicon wafer (for example, a region of about 0.4 μm from the substrate surface) under the following conditions.

Accelerating voltage: 180 keV
Beam current: 50 mA
Dose amount: 4 × 10 ¹⁷ / cm ²
After ion implantation, SC-1 and SC-2 cleaning was performed on the wafer surface. Subsequently, as shown in FIG. 2 (b), the wafer 11 is placed in a vertical heat treatment furnace and held in an Ar gas atmosphere with an oxygen partial pressure of 0.5% at a constant temperature of 1350 ° C. for 4 hours, and then the furnace is continued. A first heat treatment was performed in which the oxygen partial pressure in the inner atmosphere was increased to 70% and held for another 4 hours. As shown in FIG. 2 (c), the first heat-treated wafer is heated to 1150 ° C. at a temperature rising rate of 50 ° C./second in an ammonia-containing gas atmosphere, held for 120 seconds, and then a temperature lowering rate of 50 ° C. Rapid heat treatment was performed to lower the temperature to 400 ° C. per second. As shown in FIG. 2D, the rapidly heat-treated wafer 11 is placed in a horizontal batch furnace with the oxide films 11b and 11c on the surface left, and is kept in an argon atmosphere at a constant temperature of 800 ° C. for 48 hours. A second heat treatment was performed. The oxide film on the front and back surfaces of the wafer after the heat treatment was removed with an HF solution to obtain a SIMOX substrate. This SIMOX substrate was referred to as Example 6.

<Comparison test 4>
The SIMOX substrates in Examples 1 and 6 were cleaved in two. This cleaved substrate was selectively etched with a Wright etchant. By observing the substrate with an optical microscope, oxygen precipitates at a depth of 3 μm were measured from the surface of the substrate cleavage plane, and the density was determined. The oxygen precipitate density in the SIMOX substrate of Example 1 was 1 × 10 ⁴ pieces / cm ² or less. On the other hand, the oxygen precipitate density in the SIMOX substrate of Example 6 was in the range of 8 × 10 ⁴ pieces / cm ³ .
<Comparative test 5>
After removing the surface oxide films 11b and 11c of each SIMOX substrate 10 of Example 6 and Comparative Example 1, the SOI layer 13, the buried oxide layer 12 and the defect assembly layer 14a immediately below the buried oxide layer of each SIMOX substrate were treated with hydrofluoric acid. It melt | dissolved and collect | recovered with each aqueous solution, ICP-MS measurement was performed to these collect | recovered solution, and the nickel concentration contained in a solution was measured. In addition, the bulk layer 14 of Example 6 and Comparative Example 1 was separated into a bulk layer excluding 1 μm from the back surface and a region of 1 μm from the back surface, and was completely dissolved, and the nickel concentration in each dissolved solution was measured. .
In the SIMOX substrate of Example 6, nickel was detected in the bulk region except 1 μm from the back surface, but nickel was not detected in other regions. On the other hand, in the SIMOX substrate of Comparative Example 1, nickel was detected in the defect assembly layer 14a immediately below the buried oxide layer.

Process drawing which shows the 1st manufacturing method of the SIMOX board | substrate of this invention. Process drawing which shows the 2nd manufacturing method of the SIMOX board | substrate of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 SIMOX substrate 11 Silicon wafer 12 Embedded oxide layer 13 SOI layer 14 Bulk layer 14a Defect assembly layer 14b Oxygen precipitation nucleus 14c Oxygen precipitate 15 Vacancy

Claims (7)

Implanting oxygen ions into the silicon wafer (11);
The wafer (11) is subjected to a first heat treatment at 1300 to 1390 ° C. in a mixed gas atmosphere of oxygen and an inert gas, so that a buried oxide layer (12) is embedded in a region at a predetermined depth from the surface of the wafer (11). And forming a SOI layer (13) on the wafer surface on the buried oxide layer (12), and a method of manufacturing a SIMOX substrate,
The silicon wafer (11) before the oxygen ion implantation has an oxygen concentration of 8 × 10 ^{17 to} 1.8 × 10 ¹⁸ atoms / cm ³ (former ASTM), and the buried oxide layer (12) extends over the entire surface of the wafer. Formed,
The first heat-treated wafer is formed under the buried oxide layer 12 by performing a second heat treatment at 400 to 900 ° C. for 1 to 96 hours in an atmosphere of oxygen, nitrogen, argon, hydrogen, or a mixed gas thereof. Forming oxygen precipitation nuclei (14b) in the bulk layer (14) below the defect assembly layer (14a),
The bulk heat treatment is performed on the wafer subjected to the second heat treatment in an atmosphere of oxygen, nitrogen, argon, hydrogen, or a mixed gas thereof at a temperature of 900 to 1250 ° C. higher than the second heat treatment temperature for 1 to 96 hours. And a step of growing the oxygen precipitation nuclei (14b) formed on the oxygen precipitates (14c).   The second heat treatment is performed within a range of 1 to 96 hours by raising the temperature at a rate of 0.1 to 5.0 ° C./min in a partial range or all ranges of 400 ° C. to 900 ° C. The method according to claim 1, wherein the temperature is raised within a range of 1 to 96 hours by raising the temperature at a rate of 0.1 to 20 ° C / min in a partial range or all ranges of 900 ° C to 1250 ° C. Implanting oxygen ions into the silicon wafer (11);
The wafer (11) is subjected to a first heat treatment at 1300 to 1390 ° C. in a mixed gas atmosphere of oxygen and an inert gas, so that a buried oxide layer (12) is embedded in a region at a predetermined depth from the surface of the wafer (11). And forming a SOI layer (13) on the wafer surface on the buried oxide layer (12), and a method of manufacturing a SIMOX substrate,
The silicon wafer (11) before the oxygen ion implantation has an oxygen concentration of 8 × 10 ^{17 to} 1.8 × 10 ¹⁸ atoms / cm ³ (former ASTM), and the buried oxide layer (12) extends over the entire surface of the wafer. Or partly formed,
The first heat-treated wafer is held at 1050 to 1350 ° C. for 1 to 900 seconds, and then subjected to a rapid heat treatment for lowering the temperature at a temperature lowering rate of 10 ° C./second or more, thereby lowering the bulk below the buried oxide layer (12). Injecting holes into the layer (14);
The rapidly heat-treated wafer is formed under the buried oxide layer (12) by performing a second heat treatment at 500 to 1000 ° C. for 1 to 96 hours in an atmosphere of oxygen, nitrogen, argon, hydrogen or a mixed gas thereof. And a step of forming oxygen precipitation nuclei (14b) in the bulk layer (14) below the defect assembly layer (14a).   The second heat-treated wafer is subjected to a third heat treatment at 900 to 1250 ° C. higher than the second heat treatment temperature for 1 to 96 hours in an atmosphere of oxygen, nitrogen, argon, hydrogen, or a mixed gas thereof, thereby forming a bulk layer (14). The method according to claim 3, further comprising a step of growing the formed oxygen precipitation nuclei (14b) into oxygen precipitates (14c).   The second heat treatment is performed within a range of 1 to 96 hours by raising the temperature at a rate of 0.1 to 5.0 ° C / min in a partial range or all ranges of 500 ° C to 1000 ° C. Manufacturing method.   The production according to claim 4, wherein the third heat treatment is performed within a range of 1 to 96 hours by raising the temperature at a rate of 0.1 to 20 ° C / min in a partial range or all of the range of 900 ° C to 1250 ° C. Method. A SIMOX substrate manufactured from the method according to any one of claims 1 to 6, wherein a buried oxide layer (12) formed in a region at a predetermined depth from the wafer surface, and on the buried oxide layer An SOI layer (13) formed on the wafer surface, a defect assembly layer (14a) formed immediately below the buried oxide layer (12), and a bulk layer (14) below the buried oxide layer (12), With
The bulk layer (14) below the defect assembly layer (14a) has a gettering source made of oxygen precipitates (14c), and the density of the oxygen precipitates (14c) is 1 × 10 ⁸ to 1 × 10 A SIMOX substrate, wherein the number is ¹² / cm ³ and the size of the oxygen precipitate (14c) is 50 nm or more.

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