JP2010034473A - Method of manufacturing simox substrate, and etching device used for the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce patterning defects in device fabrication caused by sticking of oxidation foreign matter by removing the oxidation foreign matter sticking on the reverse surface of a substrate through a high-temperature oxidation heat treatment. <P>SOLUTION: The method of manufacturing a SIMOX (Separation by Implanted Oxygen) substrate includes: the stages of injecting oxygen ions into a wafer; manufacturing an SIMOX substrate by placing the wafer on a silicon ring and carrying out a heat treatment to form an embedded oxide film in a region of predetermined depth from a surface and then forming an SOI layer on the embedded oxide film, and further forming an entire-surface oxide film; and etching the entire surface of the substrate after demounting the SIMOX substrate which has been heat-treated from the ring to remove the entire-surface oxide film, and the method further includes: a stage of etching a ring-shaped region including a contact part of the substrate reverse surface entirely having the oxide film, which comes into contact with the ring in the heat treatment stage to remove the sticking oxidation foreign matter produced owing to the heat treatment while contacting between the wafer and ring before or after the stage of removing the entire-surface oxide film. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method of manufacturing a SIMOX (Separation by Implanted Oxygen) substrate by forming a buried oxide film in a silicon wafer and forming an SOI (Silicon-On-Insulator) layer on the buried oxide film. The present invention relates to an etching apparatus used in 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. And (4) excellent characteristics such as improved anti-latch-up 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 has a small number of manufacturing steps, and the SOI substrate manufactured by the SIMOX method, that is, the SIMOX substrate, can easily obtain a device formation region having a large area and good crystallinity. Is expected as a new technique.

As shown in FIGS. 9A to 9D, the SIMOX substrate is manufactured by first mirror-treating both surfaces of the silicon wafer 2 and then implanting oxygen ions 1 from the mirror-finished surface by wafer implantation 2. An ion implantation process for implanting to a predetermined depth therein, and a heat treatment process for forming a buried oxide film 3 in the wafer 2 by subjecting the wafer 2 implanted with oxygen ions 1 to a high temperature heat treatment in an oxidizing atmosphere. Specifically, the silicon wafer 2 is held at a temperature of 500 ° C. to 650 ° C., and oxygen atom ions or oxygen molecular ions 1 of about 10 ¹⁷ to 10 ¹⁸ ions / cm ² are implanted to a predetermined depth from the surface of the wafer 2. To do. Subsequently, the silicon wafer 2 into which oxygen ions 1 have been implanted is put into a heat treatment furnace maintained at a temperature of 500 ° C. to 700 ° C., and the temperature is gradually raised so as not to generate slip, and a temperature of about 1300 ° C. to 1390 ° C. For about 10 hours. Oxygen ions 1 implanted into the wafer 2 by this high-temperature heat treatment react with silicon to form a buried oxide film 3 inside the wafer. Through these steps, a SIMOX substrate 6 including a support substrate 9, a buried oxide film 3 formed on the support substrate 9, and an SOI layer 4 formed on the buried oxide film 3 is manufactured. The Since the obtained SIMOX substrate 6 has the oxide film 8 formed on the entire surface by the heat treatment, the entire oxide film 8 is removed by etching the entire surface of the substrate 6 to remove the oxide film 8 generated by the heat treatment. Is done.

In the processing chamber of the heat treatment furnace used in the heat treatment step, a reaction tube into which a processing gas is introduced, a support for supporting the wafer, a heat insulating plate for suppressing heat radiation from the furnace opening, and the like are disposed. In order to reduce the occurrence of slip due to an increase in the diameter of the wafer, a support has been developed that makes line contact and surface contact with the wafer in a ring shape. For example, as one form thereof, a first jig which is made of a silicon material and is in direct contact with and supported by a semiconductor substrate, and a second jig which holds the first jig and is placed on a heat treatment boat, A heat treatment jig for a semiconductor substrate provided with a substrate is disclosed (for example, see Patent Document 1). In Patent Document 1, a silicon single crystal is used as the first jig, and silicon carbide that is strong against high-temperature strength is used as the second jig serving as a holder.
International Publication No. 2005/045917 Pamphlet (Specification, Page 2, Lines 20 to 24, Claim 1)

  However, when a wafer support having a silicon ring at the contact portion with the wafer as described in Patent Document 1 is used, as shown in FIGS. 10 (a) to 10 (c), ion implantation is performed. The subsequent wafer 2 is mounted in the furnace while being placed on the support 5 and subjected to heat treatment. In the high temperature oxidation heat treatment, not only the entire surface of the wafer 2 but also the surface of the silicon ring 5a directly supporting the wafer 2 is formed. Oxidized, and an oxide film 8 is also formed at the contact portion between the wafer 2 and the silicon ring 5a, so that the wafer 2 is supported by the silicon ring 5a via the oxide film 8. Then, as shown in FIG. 10 (d), when the SIMOX substrate 6 after the heat treatment is lowered from the silicon ring 5a, if the oxide film 8a in the contact portion with the silicon ring 5a is adsorbed to the substrate 6 side, the back surface of the substrate 6 It adheres as oxidized foreign matter 8a. Then, as shown in FIG. 10 (e), even if the entire surface of the substrate 6 is subjected to an etching process for removing the oxide film, the adhered foreign matter 8a is present at the contact portion with the silicon ring 5a on the back surface of the substrate 6. As a result, the oxide films 8 and 8a cannot be completely removed, and the oxide film remains in a ring shape on the back surface of the substrate 6 as a foreign substance.

  Here, it is considered that the etching process for removing the oxide film applied to the entire surface of the substrate is performed by taking a longer time than usual until the oxide film formed on the back surface of the substrate does not remain as a foreign substance. In this case, the edge of the buried oxide film located on the side surface of the substrate is etched, and the end surface of the SOI layer corresponding to the upper layer is projected in an eave-like shape. Since the overhanging portion is thin, it is weak in mechanical strength and is chipped or peeled off during various subsequent processing steps. The silicon pieces generated thereby become particles and adhere to the surface of the SOI layer in the active region. When a device is formed on an SOI layer to which particles are attached, there is a problem in that the yield of the product is reduced due to defective patterns and defects in various deposited films.

  If foreign matter remaining after the entire surface oxide film treatment exists on the back surface of the substrate, the surface of the substrate is raised between the stage of the exposure apparatus and the SIMOX substrate during device fabrication, and local defocusing occurs. There was a risk of causing patterning failure of the resist pattern.

  An object of the present invention is to remove a foreign oxide adhering to the back surface of a substrate by a high-temperature oxidation heat treatment, and to reduce a patterning defect during device fabrication caused by the adhering oxidized foreign matter, and the method of manufacturing a SIMOX substrate Another object of the present invention is to provide an etching apparatus used for the above.

  In the invention according to claim 1, as shown in FIG. 1, an ion implantation process for implanting oxygen ions 11 into a silicon wafer 12, and a heat treatment is performed by placing the wafer 12 on a silicon ring 15a and applying heat treatment. Forming a buried oxide film 13 in a predetermined depth region to form an SOI layer 14 on the wafer surface on the buried oxide film 13 to form a SIMOX substrate 16 and further forming an oxide film 18 on the entire surface; And improving the method of manufacturing the SIMOX substrate, including the step of removing the oxide film 18 generated by the heat treatment by removing the heat-treated SIMOX substrate 16 from the silicon ring 15a and then etching the entire surface of the SIMOX substrate 16. It is. The characteristic structure is that before or after the entire oxide film removing step, the ring-shaped region 17 including the contact portion with the silicon ring 15a in the heat treatment step on the back surface of the SIMOX substrate 16 having the oxide film on the entire surface is etched, and the wafer is etched. And a step of removing the attached oxidized foreign matter 18a caused by the heat treatment in the contact state between the silicon ring and the silicon ring.

  The invention according to claim 2 is an apparatus for etching a ring-shaped region including a contact portion with a ring on a wafer back surface having an oxide film after heat treatment after the silicon wafer is supported on the back surface of the wafer by a silicon ring during heat treatment. As shown in FIG. 2, the disc-shaped base 21 installed horizontally, and the first and second concentric circles provided on the upper surface of the base 21 at the same height from the center of the base 21 toward the outer periphery of the base 21. The second peripheral walls 22 and 23 and the rear surface of the wafer 16 which is erected on the outer periphery of the base 21 are opposed to the upper surface of the base 21 with the back surface of the wafer 16 being separated from each upper end of the first and second peripheral walls 22 and 23 by 0.5 to 3 mm. A water supply for supplying pure water to a plurality of wafer supports 24 that support the wafer 16 and a circular recess 21 a that is provided at the center of the base 21 and surrounded by the first peripheral wall 22. An etching solution supply hole 26 and a ring shape for supplying an etching solution to the hole 25 and a ring-shaped recess 21 b provided in the base 21 between the first peripheral wall 22 and the second peripheral wall 23 and surrounded by the peripheral walls 22, 23. Etching solution discharge holes 27 for discharging the etching solution stored in the recesses 21b, and all of pure water that is provided in the first peripheral wall 22 so as to vertically penetrate the circular recesses 21a and the ring-shaped recesses 21b. A plurality of first through holes 28 for discharging a part of the etching solution and a plurality of second holes for discharging a part of the etching solution that penetrates the second peripheral wall 23 in the vertical direction and overflows from the ring-shaped recess 21b. Provided with a through hole 29 and a plurality of ejection holes 30 provided in the base 21 outside the second peripheral wall 23 for ejecting pure water higher than the second peripheral wall 23, The ring-shaped region on the back surface of the wafer 16 supported horizontally by the support 24 is brought into contact with the etching solution stored in the ring-shaped recess 21b to etch the ring-shaped region, and the heat treatment is performed in a contact state between the wafer and the silicon ring. The attached oxidized foreign matter is removed, the inner region of the ring-shaped region on the back surface of the wafer 16 is brought into contact with pure water stored in the circular recess 21a to protect the inner region from the etching solution, and the back surface of the wafer 16 is protected. The etching apparatus is configured to contact the outer region of the ring-shaped region 21b with pure water ejected from the plurality of ejection holes 30 to protect the outer region from the etching solution.

  The invention according to claim 3 is the invention according to claim 2, and as shown in FIG. 4, the etching solution discharged from the etching solution discharge hole 27 is supplied to the etching solution supply hole 26 by the pump 32 and is etched. This is an etching apparatus that circulates and uses a liquid.

  The invention according to claim 4 is the etching apparatus according to claim 2 or 3, wherein the heater 33 for heating the etching solution to 25 to 45 ° C. is provided in the flow path for circulating the etching solution.

  The manufacturing method of the SIMOX substrate of the present invention removes the ring-shaped oxide foreign matter adhering to the back surface of the substrate by high-temperature oxidation heat treatment by performing a step of removing the attached oxide foreign matter before or after the entire oxide film removing step. Since the SIMOX substrate has a high flatness, patterning defects at the time of device fabrication that have been caused by the adhered oxide foreign matter can be reduced.

  Moreover, the etching apparatus of the present invention can efficiently remove only the ring-shaped oxidized foreign matter adhering to the back surface of the substrate by the high-temperature oxidation heat treatment and the surrounding ring-shaped region in the production of the SIMOX substrate.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  In the method of manufacturing a SIMOX substrate according to the present invention, after implanting oxygen ions into a silicon wafer, the wafer is placed on a silicon ring and subjected to heat treatment to form a buried oxide film in a predetermined depth from the wafer surface. As a result, an SOI layer is formed on the wafer surface on the buried oxide film, a SIMOX substrate is formed, an oxide film is further formed on the entire surface, the heat-treated SIMOX substrate is lowered from the silicon ring, and then the entire surface of the SIMOX substrate is etched. The oxide film produced by the heat treatment is removed.

  The characteristic structure is that before or after the removal of the oxide film on the entire surface, the ring-shaped region including the contact portion with the silicon ring in the heat treatment process on the back surface of the SIMOX substrate having the oxide film on the entire surface is etched, and the wafer and the silicon ring are etched. The method further includes a step of removing adhering oxidized foreign matter generated due to the heat treatment in the contact state. Each of these steps is shown below.

(1) Ion implantation process First, as shown in FIG. 1 (a), a single crystal ingot produced by a method such as the Czochralski method or the floating zone method is sliced and processed into a wafer, and the wafer is wrapped. Then, a silicon wafer 12 formed by performing etching, grinding, polishing, and mirror polishing is prepared. The oxygen concentration of the prepared silicon wafer 12 before oxygen ion implantation is preferably 15 to 30 ppma.

  Next, oxygen ions 11 are implanted into the silicon wafer 12. The implantation of oxygen ions 11 is performed by the same means as conventionally used, but the thickness of the SOI layer 14 in the finally obtained SIMOX substrate 16 shown in FIG. 1 (f) is 5 to 100 nm, preferably Implanting into the region of a predetermined depth from the surface of the wafer 12 so as to be 15 to 90 nm. Here, the thickness of the SOI layer 14 is limited to the range of 5 to 100 nm because a breakdown voltage failure occurs when the thickness is less than 5 nm, or defects due to surface roughness due to the roughness of the buried oxide film 13 and the SOI layer 14. This is because the withstand voltage decreases when the thickness exceeds 100 nm.

(2) Heat treatment step As shown in FIG. 1 (b), the silicon wafer 12 into which the oxygen ions 11 have been implanted is placed on a support 15 in which the contact point with the wafer is formed by the silicon ring 15a. The support is mounted in the heat treatment furnace in a supported state. Subsequently, as shown in FIG. 1 (c), in an oxidizing atmosphere, that is, in a mixed atmosphere of oxygen and an inert gas, the temperature is 1300 to 1370 ° C., preferably 1330 to 1360 ° C., more preferably 1350 ° C. A high temperature oxidation heat treatment is performed for 15 to 30 hours, preferably 18 to 25 hours. Examples of the inert gas include argon and nitrogen gas. Therefore, the gas atmosphere of this heat treatment is preferably a mixed gas of oxygen and argon or a mixed gas of oxygen and nitrogen. Here, the heat treatment temperature is limited to the range of 1300 to 1370 ° C. If the temperature is less than 1300 ° C., there is a risk that a breakdown voltage will be generated, and if it exceeds 1370 ° C., This is because the deterioration of the silicon wafer 12 is abnormally deteriorated and quality abnormalities occur. The reason why the heat treatment time is limited to the range of 15 to 30 hours is that the normal buried oxide film 13 cannot be formed if the heat treatment time is less than 15 hours, and the productivity decreases if the heat treatment time exceeds 30 hours. The reason why the silicon ring 15a is used in the contact portion with the wafer as the support 15 used in this heat treatment is to reduce the occurrence of slip due to the large diameter of the wafer.

  By this high-temperature oxidation heat treatment, the buried oxide film 13 is formed in a region having a predetermined depth from the surface of the wafer 12 and the SOI layer 14 is formed on the surface of the wafer 12 on the buried oxide film 13. An oxide film is formed on the entire surface of the substrate. That is, as shown in FIG. 1C, a SIMOX substrate having a support substrate 19, a buried oxide film 13 formed on the support substrate 19, and an SOI layer 14 formed on the buried oxide film 13. 16 is obtained.

  Further, by this high-temperature oxidation heat treatment, not only the entire surface of the SIMOX substrate 16 but also the silicon ring 15a that directly supports the SIMOX substrate 16 is oxidized, and an oxide film is also formed at the contact portion between the SIMOX substrate 16 and the silicon ring 15a. Therefore, the SIMOX substrate 16 is supported by the silicon ring 15a via the oxide films 18 and 18a. The oxide film 18 formed on the entire surface of the SIMOX substrate 16 has a thickness of about 800 nm, the oxide film 18a formed on the surface of the silicon ring 15a has a thickness of at least about 800 nm, and between the SIMOX substrate 16 and the silicon ring 15a. The existing oxide films 18 and 18a are considered to have a total thickness of 1600 nm or more.

  After the high-temperature oxidation heat treatment, as shown in FIG. 1D, when the SIMOX substrate 16 is lowered from the silicon ring 15a, an oxide film formed between the SIMOX substrate 16 and the silicon ring 15a is formed on the surface of the silicon ring 15a. When the oxidized film 18a is adsorbed on the substrate 16 side, it adheres to the back surface of the substrate as oxidized foreign matter. Therefore, after the high-temperature oxidation heat treatment, it is necessary to remove the ring-shaped oxidized foreign matter adhering to the contact portion with the silicon ring on the back surface of the SIMOX substrate.

  When the SIMOX substrate 16 is lowered from the silicon ring 15a, the oxide film 18a formed on the surface of the silicon ring 15a is not adsorbed on the SIMOX substrate 16 side, and conversely, the oxide film 18 formed on the back surface side of the SIMOX substrate 16 is formed. Although it may be adsorbed on the silicon ring 15a side, the probability is about 50%, and there is still a possibility that adhered oxide foreign matter may be formed on the back surface of the SIMOX substrate 16 with a high probability. When the oxide film 18 formed on the back surface side of the SIMOX substrate 16 is adsorbed on the silicon ring 15a side, only the portion of the oxide film formed on the back surface of the SIMOX substrate 16 that is in contact with the silicon ring 15a is peeled off. Is formed.

(3) Adhering Oxide Foreign Body Removal Step As shown in FIG. 1E, the ring-shaped region 17 including the contact portion with the silicon ring 15a in the heat treatment step on the back surface of the SIMOX substrate 16 having the oxide film 18 on the entire surface is etched. Then, the attached oxidized foreign matter resulting from the heat treatment in the contact state between the wafer 12 and the silicon ring 15a is removed. Here, the ring-shaped region 17 refers to a ring-shaped oxidized foreign material adhering to the back surface of the substrate 16 by high-temperature oxidation heat treatment and a peripheral region. Only the ring-shaped region 17 is etched on the back surface of the substrate 16 after this process is performed, and the inner region 17a located inside the ring-shaped region 17 and the outer region 17b located outside are not etched and the oxide film 18 is not etched. The remaining state is maintained.

  The etching apparatus of the present invention used in this step is an apparatus that can efficiently etch only the ring-shaped region 17 on the back surface of the substrate 16.

  As shown in FIGS. 2 and 3, the etching apparatus 20 includes a base 21, first and second peripheral walls 22 and 23, a wafer support 24, a water supply hole 25, an etchant supply hole 26, and an etchant. A discharge hole 27, a first through hole 28, a second through hole 29, and an ejection hole 30 are provided.

  The base 21 has a disk shape and is installed horizontally. On the upper surface of the base 21, first and second peripheral walls 22 and 23 are provided concentrically at the same height from the center of the base 21 toward the outer periphery of the base 21. It is done. The wafer support 24 is erected on the outer periphery of the base 21 so as to support the wafer so as to face the upper surface of the base with the back surface of the wafer separated from the upper ends of the first and second peripheral walls 22 and 23 by 0.5 to 3 mm. A plurality are provided. The water supply hole 25 is provided at the center of the base 21. Pure water is supplied from the water supply hole 25 to the circular recess 21 a surrounded by the first peripheral wall 22. Further, the etchant supply hole 26 and the etchant discharge hole 27 are provided in the base 21 between the first peripheral wall 22 and the second peripheral wall 23, respectively. The etchant is supplied from the etchant supply hole 26 to the ring-shaped recess 21b surrounded by the peripheral walls 22 and 23, and most of the etchant stored in the ring-shaped recess 21b is discharged from the etchant discharge hole 27. A plurality of first through holes 28 are provided through the first peripheral wall 22 in the vertical direction. The first through hole 28 is provided to discharge all of the pure water overflowing from the circular recess 21a and the ring-shaped recess 21b and a part of the etching solution. A plurality of second through holes 29 are provided through the second peripheral wall 23 in the vertical direction. The second through hole 29 is provided to discharge a part of the etching solution overflowing from the ring-shaped recess 21b. A plurality of ejection holes 30 are provided in the base 21 outside the second peripheral wall 23. From the ejection hole 30, it is comprised so that a pure water may be ejected higher than the 2nd surrounding wall 23. FIG. A plurality of third through holes 31 are provided in the base 21 further outside the ejection holes 30. The third through hole 31 is provided to discharge pure water ejected from the ejection hole.

  FIG. 4 is a schematic diagram showing the flow of the etching solution and pure water supplied to the etching apparatus. Note that since the etching apparatus shows only the configuration necessary for the flow of the etching solution and pure water, the configuration is partially omitted.

  As shown in FIG. 4, the etching solution stored in a tank (not shown) is supplied from the etching solution supply hole 26 to the ring-shaped recess 21 b by the pump 32. As the etching solution to be used, hydrofluoric acid is suitable. Further, in order to warm the supplied etching solution, a heater 33 that warms the etching solution may be provided in a flow path for circulating the etching solution, that is, a flow path between the pump 32 and the etching solution supply hole 26. The heating range in this case is preferably 25 to 45 ° C. By heating the etching solution, the etching rate is increased and the etching processing capability is improved. And most of the supplied etching liquid is discharged | emitted from the etching liquid discharge hole 27 provided in the base 21 of the ring-shaped recessed part 21b. Although the discharged etching solution may be discarded as it is, from the viewpoint of environmental protection and processing cost, the discharged etching solution is sent to the pump 32 and supplied again to the etching solution supply hole 26 to circulate the etching solution. It is good also as a structure which is used. The pure water stored in a tank (not shown) is supplied from the water supply hole 25 to the circular recess 21 a by the pump 34. Moreover, it is comprised so that a pure water may be ejected from the ejection hole 30 higher than the 2nd surrounding wall 23. FIG.

  In addition, it is good also as a structure which warms the board | substrate 16 by supplying warm water from the SIMOX board | substrate 16 surface side, and accelerates the etching rate of the etching liquid which contacts the ring-shaped area | region 17 by it.

  An adhesion oxide foreign matter removing process using the etching apparatus having such a configuration will be described.

  As shown in FIG. 2, first, the SIMOX substrate 16 having an oxide film on the entire surface is horizontally supported on the four wafer supports 24 of the etching apparatus 20. These supports 24 contact only the end face of the substrate 16. The supported substrate 16 is opposed to the upper surface of the base 21 with the back surface spaced 0.5 to 3 mm from the upper ends of the first and second peripheral walls 22 and 23. By providing an interval within the above range, the etching solution and pure water can be supplied and discharged smoothly, and the inner region 17a located inside the ring-shaped region and the outer region 17b located outside can be protected from the etching solution.

  In this state, the etchant is supplied from the etchant supply hole 26 to the ring-shaped recess 21b, pure water is supplied from the water supply hole 25 to the circular recess 21a, and pure water is also ejected from the ejection hole 30.

  As a result, the etching solution stored in the ring-shaped recess 21 b comes into contact with the ring-shaped region 17 on the back surface of the SIMOX substrate 16, the ring-shaped region 17 is etched, and the oxidized foreign matter attached to the back surface of the substrate 16 is removed. And most of the supplied etching liquid is discharged | emitted out of the etching apparatus 20 from the etching liquid discharge hole 27 provided in the ring-shaped recessed part 21b. Further, a part of the etching solution overflows from the ring-shaped recess 21 b and flows into the first through hole 28 inside the first peripheral wall 22 and the second through hole 29 inside the second peripheral wall 23, and goes outside the etching apparatus 20. Discharged. Therefore, the etching solution does not contact the inner region 17a located inside the ring-shaped region and the outer region 17b located outside.

  Further, the pure water stored in the circular recess 21 a comes into contact with the inner region 17 a located inside the ring-shaped region 17 of the SIMOX substrate 16, and this inner region 17 a is protected from the etching solution, and is outside the ring-shaped region 17. Pure water ejected from the plurality of ejection holes 30 is in contact with the outer region 17b located, and the outer region 17b is protected from the etching solution. Thus, since the inner region 17a and the outer region 17b are protected by pure water, even if the etching liquid scatters from the ring-shaped recess 21b, it is not etched.

  In this case, it is sufficient to remove the adhering oxide foreign matter. However, as long as the back surface of the substrate 16 is not roughened, the etching process is performed in the ring-shaped region 17 as shown in FIG. Etching may be performed until all of the oxide films 18 and 18a are removed.

  FIG. 5 is a photograph of the etching apparatus 20 of the present invention, and FIG. 6 is a photograph showing a state in which a SIMOX substrate 16 having an oxide film is mounted on the entire surface and the ring-shaped region 17 on the back surface is etched on the etching apparatus 20 of the present invention. 7 is a photograph showing the surface of the substrate 16 after etching the ring-shaped region 17 on the back surface of the SIMOX substrate 16 using the etching apparatus 20 of the present invention. FIG. 8 is a diagram showing the etching apparatus 20 of the present invention. FIG. 5 is a photograph showing the back surface of the substrate 16 after etching the ring-shaped region 17 on the back surface of the SIMOX substrate 16.

  As described above, it can be confirmed that only the ring-shaped region 17 on the back surface of the SIMOX substrate 16 after the heat treatment is etched in the process of removing the attached oxidized foreign matter, and the attached oxidized foreign matter is removed.

  By using the etching apparatus 20 having such a configuration, high-temperature and high-concentration hydrofluoric acid can be used as the etching solution, and as a result, the attached oxide foreign matter can be efficiently removed.

(4) Entire Oxide Film Removal Step Next, as shown in FIG. 1F, the entire surface of the SIMOX substrate 16 that has been subjected to the adhered oxide foreign matter removal step is etched to remove the entire oxide film generated by the heat treatment. . In this step, the oxide film on the entire surface of the SIMOX substrate 16 can be removed by a method generally performed conventionally. For example, the desired SIMOX substrate can be obtained by storing the etching solution in an etching tank, immersing the substrate 16 in the etching tank for a certain period of time to remove the oxide film on the entire surface, followed by cleaning with pure water and drying. it can.

  In this way, through the above steps, the ring-shaped oxidized foreign matter adhering to the back surface of the substrate is removed by the high-temperature oxidation heat treatment to obtain a high flatness SIMOX substrate. Patterning defects during device fabrication can be reduced.

  In this embodiment, the example in which the adhered oxide foreign matter removing step is performed before the entire surface oxide film removing step has been described, but it may be performed before the entire surface oxide film removing step.

  However, in consideration of the quality of the back surface of the SIMOX substrate, if the attached oxide foreign matter removing step is performed before the entire oxide film removing step, the cleanliness of the back surface is increased. It is preferable to set the order of performing the steps.

  In addition, when the adhered oxide foreign matter removal process is performed before the entire oxide film removal process, even if liquid splash or dirt adheres to the surface side in this adhered oxide foreign matter removal process, an oxide film is still formed on the surface side. In this state, the deterioration of the surface quality can be extremely reduced. Therefore, it is preferable that the entire oxide film removing step is performed after the attached oxide foreign matter removing step.

  The etching apparatus of the present invention is not limited to use in a method for manufacturing a SIMOX substrate, but can be used for post-process etching that requires high-temperature oxidation heat treatment.

The process figure which shows the manufacturing process of the SIMOX board | substrate of this invention. The top view of the etching apparatus of this invention. FIG. 3 is a cross-sectional view taken along line A-B-C in FIG. 2. Schematic which shows the flow of an etching liquid and a pure water when performing the adhesion oxidation foreign material removal process using the etching apparatus of this invention. The photograph figure which shows the etching apparatus of this invention. The photograph figure which shows the state which mounted the SIMOX board | substrate which has an oxide film on the whole surface in the etching apparatus of this invention, and etched the ring-shaped area | region of the back surface. The photograph figure which shows the board | substrate surface after etching the ring-shaped area | region of the back surface of a SIMOX board | substrate using the etching apparatus of this invention. The photograph figure which shows the board | substrate back surface after etching the ring-shaped area | region of the SIMOX board | substrate back surface using the etching apparatus of this invention. Process drawing which shows the manufacturing process of a general SIMOX substrate. Process drawing which shows the manufacturing process of the conventional SIMOX board | substrate at the time of using a silicon ring for a contact part with a wafer as a heat processing support tool.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Oxygen ion 12 Silicon wafer 13 Embedded oxide film 14 SOI layer 15 Wafer support 15a Silicon ring 16 SIMOX substrate 17 Ring-shaped area | region 18 Oxide film 19 Support substrate 20 Etching apparatus 21 Base 21a Circular recessed part 21b Ring-shaped recessed part 22 1st surrounding wall 23 Second peripheral wall 24 Wafer support 25 Water supply hole 26 Etch solution supply hole 27 Etch solution discharge hole 28 First through hole 29 Second through hole 30 Ejection hole

Claims (4)

An ion implantation process for implanting oxygen ions into the silicon wafer;
The wafer is placed on a silicon ring and subjected to a heat treatment to form a buried oxide film in a region at a predetermined depth from the wafer surface, thereby forming an SOI layer on the wafer surface on the buried oxide film to form a SIMOX substrate. A heat treatment step of forming an oxide film on the entire surface, and
A method of manufacturing a SIMOX substrate, comprising: removing the oxide film generated by the heat treatment by removing the oxide film generated by the heat treatment by removing the heat-treated SIMOX substrate from the silicon ring and then etching the entire surface of the SIMOX substrate;
Before or after the entire surface oxide film removing step,
This was caused by etching the ring-shaped region including the contact portion with the silicon ring during the heat treatment process on the back surface of the SIMOX substrate having the oxide film on the entire surface, and performing the heat treatment in the contact state between the wafer and the silicon ring. A method for producing a SIMOX substrate, further comprising the step of removing adhering oxidized foreign matter. An apparatus for etching a ring-shaped region including a contact portion with the ring on the wafer back surface having the oxide film after the heat treatment after the silicon wafer is supported on the back surface of the wafer by a silicon ring during the heat treatment,
A disc-shaped base installed horizontally;
First and second peripheral walls provided concentrically at the same height from the center of the base toward the outer periphery of the base on the upper surface of the base;
A plurality of wafer supports that are erected on the outer periphery of the base and support the wafer so as to face the upper surface of the base in a state where the back surface of the wafer is separated from each upper end of the first and second peripheral walls by 0.5 to 3 mm; ,
A water supply hole for supplying pure water to a circular recess provided in the center of the base and surrounded by the first peripheral wall;
An etching solution supply hole for supplying an etching solution to a ring-shaped recess provided on a base between the first and second peripheral walls and surrounded by both peripheral walls and an etching solution stored in the ring-shaped recess are discharged. Etching solution discharge hole for,
A plurality of first through holes for exhausting all of the pure water overflowing from the circular recess and the ring-shaped recess and a part of the etching solution, which are provided through the first peripheral wall in the vertical direction;
A plurality of second through-holes that are provided through the second peripheral wall in the vertical direction and discharge a part of the etchant overflowing from the ring-shaped recess;
A plurality of ejection holes provided on the outer base of the second peripheral wall for ejecting pure water higher than the second peripheral wall;
Etching the ring-shaped region by contacting an etching solution stored in the ring-shaped recess with a ring-shaped region on the back surface of the wafer horizontally supported by the plurality of wafer supports, and the contact state between the wafer and the silicon ring The attached oxidized foreign matter generated due to the heat treatment is removed, and the inner region of the ring-shaped region on the back surface of the wafer is brought into contact with pure water stored in the circular recess to protect the inner region from the etching solution. And an etching apparatus configured to protect the outer region from the etching solution by bringing pure water ejected from the plurality of ejection holes into contact with an outer region of the ring-shaped region on the back surface of the wafer. .   3. The etching apparatus according to claim 2, wherein the etching solution discharged from the etching solution discharge hole is supplied to the etching solution supply hole by a pump and the etching solution is circulated for use.   4. The etching apparatus according to claim 2, further comprising a heater for heating the etching solution to 25 to 45 [deg.] C. in the flow path for circulating the etching solution.