JP2008288315A - PIN HOLE JUDGING METHOD OF SiC COATING - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new judging method for easily and securely judging the presence of a pin hole of SiC coating in a porous graphite member coated with SiC. <P>SOLUTION: The judging method comprises a process for hermetically storing the porous graphite member coated with SiC and an initial amount of liquid in a hermetical storage member at a room temperature, a process for heating the hermetical storage member hermetically storing the porous graphite member and liquid and making the liquid to be vapor, a process for cooling the hermetical storage member to the room temperature after the heating process is terminated, a process for collecting liquid in the hermetical storage member and a process for comparing the initial amount of liquid with an amount of collected liquid. When the amount of collected liquid decreases below the initial amount of liquid, it is judged that the pin hole exists in SiC coating. When the amount of collected liquid does not decrease below the initial amount of liquid, it is judged that the pin hole does not exist in SiC coating. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for determining the presence or absence of pinholes in SiC coating in a porous graphite member coated with SiC.

  In the manufacturing process of a semiconductor device, there is a step of forming a thin film on the substrate by supplying a reactive gas onto a semiconductor substrate cut off from the outside by a container. In these steps, a vapor phase growth apparatus is used that forms a thin film by causing a gas phase reaction on the substrate by supplying a raw material gas.

  Among them, in particular, an epitaxial growth apparatus for growing a single crystal of silicon on a silicon substrate is used in a manufacturing process of a semiconductor device such as an LSI. In this apparatus, a silicon substrate is usually heated to 1000 ° C. or more, a mixed gas of a raw material gas such as silicon tetrachloride and trichlorosilane and hydrogen is supplied into a reaction vessel, and the silicon substrate is reduced or thermally decomposed. A single crystal silicon thin film is grown on the epitaxial growth. Epitaxial growth is used to increase the breakdown voltage of bipolar devices in the manufacturing process of semiconductor devices. When manufacturing megabit memories in devices, it is a necessary technology to prevent soft errors and latch-up caused by alpha rays. It has become.

  For such epitaxial growth, for example, a vapor phase growth apparatus as shown in FIG. 3 is used. FIG. 3 is a schematic cross-sectional view showing a conventional vapor phase growth apparatus.

  In FIG. 3, reference numeral 30 denotes a vapor phase growth apparatus. The vapor phase growth apparatus 30 is separated from the outside by a quartz chamber 31 and a chamber base 32. A cylindrical support base 33 is rotatably disposed in the center of the chamber 31. The support base 33 supports a susceptor 36 on which a plurality of semiconductor substrates (wafers) 35 are placed from below. Has been. The susceptor 36 is formed of a disk-shaped graphite base material having an opening 36a in the center, and the graphite member is covered with a SiC film having a thickness of 150 μm by a CVD method.

  A source gas introduction part 37 is opened at the center of the support base 33, and the lower part of the support base 33 protrudes below the chamber base 32. A source gas nozzle 38 is connected to the central opening 36 a of the susceptor 36. The source gas nozzle 38 has a plurality of holes 38 a so that the source gas flows out substantially parallel to the surface of the semiconductor substrate 35. A source gas discharge port 40 is formed at the center of the chamber base 32 and around the support base 33. A coil 39 is installed in a vortex shape below the susceptor 36 and induction-heats the susceptor 36 from below.

  However, the susceptor coated with the SiC film here has a problem that pinholes are formed in the SiC film. FIG. 4 is a drawing showing the result of a micrograph of the pinhole 50 actually formed in the susceptor 36.

  When the pinhole 50 is formed in the SiC film in the recess of the susceptor 36 that accommodates the wafer 35, impurity gas from the graphite material constituting the susceptor 36 is released from the pinhole 50, and the susceptor is used to grow the epitaxial film. There is a problem that pinhole marks 52 are generated on the back surface of the wafer 35 by reacting with the wafer 35 accommodated in the recess 36. FIG. 5 shows a malfunction of the wafer 35 when the pinhole 50 is actually generated in the susceptor 36. FIGS. 5A and 5B are diagrams showing a state where a defect of the wafer 35 is photographed when the pinhole 50 is opened in the susceptor 36, wherein FIG. 5A is a photographed from the top surface, and FIG. Each state is shown. As shown in FIGS. 5A and 5B, when the pinhole 50 is opened in the susceptor 36, the pinhole-shaped mark 52 is transferred to the same position on the back surface of the wafer 35. If the darkness and size of the mark 52 exceed the visual appearance inspection standard for each user, it becomes a defective product as foreign matter adhesion.

  FIG. 6 is a map showing the results of impurity measurement inside the wafer. As shown in FIG. 6, when the internal impurity measurement does not satisfy the reference value even if there is no foreign matter attached, FIG. The display is determined as shown by the thick line hatched portion 54 of the cell in the map diagram, resulting in a defective product.

For this reason, conventionally, when the pinhole 50 is formed in the SiC film, the susceptor 36 is replaced to prevent the pinhole mark 52 from being generated on the wafer 35. However, it is not appropriate from the viewpoint of effective utilization of resources to replace the susceptor 36 every time the pinhole 50 is formed in the SiC film and to discard the replaced susceptor 36. From this point of view, Patent Document 1 discloses a susceptor that can be partially removed and replaced.
JP2002-164293

  Since the influence of the susceptor pinhole becomes stronger as the susceptor usage time elapses, it may affect a large amount of wafers. Therefore, it is important to find the pinhole before using the susceptor. Therefore, conventionally, in order to confirm whether there is a pinhole in the susceptor in advance, evacuation is performed with the susceptor in the vacuum vessel, and the presence or absence of a pinhole is determined from the relationship between the degree of vacuum and time. Was. This is because in a state without a pinhole, the degree of vacuum rises in a short time, but when there is a pinhole, it takes time to increase the degree of vacuum because the gas in the porous graphite leaks from the pinhole. This is a determination method using a phenomenon. However, when the pinhole is very small, the determination is difficult. Because of such a problem, a method for simply and reliably determining the presence or absence of pinholes has been demanded.

  The present invention has been made in view of the above-described conventional problems, and is a novel determination method capable of easily and reliably determining the presence or absence of SiC-coated pinholes in a porous graphite member coated with SiC. The purpose is to provide.

  In order to solve the above-mentioned problem, the SiC-coated pinhole presence / absence determination method in the SiC-coated porous graphite member according to the present invention includes a porous graphite member coated with SiC and an initial amount of liquid in a sealed housing member. A step of hermetically storing at room temperature, a step of heating the hermetic storage member that hermetically stores the porous graphite member and the liquid to make the liquid vapor, and a step of cooling the hermetic storage member to room temperature after the heating step is completed. And a step of recovering the liquid in the sealed housing member and a step of comparing the initial amount of the liquid and the recovered amount of the recovered liquid, wherein the recovered amount of the liquid is smaller than the initial amount of the liquid If there is a pinhole in the SiC coating, it is determined that there is no pinhole in the SiC coating if the recovery amount of the liquid is not reduced below the initial amount of the liquid. Than is.

  That is, a member made of porous graphite such as a susceptor coated with SiC is sealed in a sealed housing member such as a plastic bag together with a liquid such as water, and heated from the outside to vaporize the liquid such as water (for example, water vapor) Then, the vapor (water vapor) is adsorbed to the porous graphite through even a very small pinhole. Then, when it is cooled to room temperature, the adsorbed vapor (water vapor) becomes liquid, and it is difficult to return to the outside of the susceptor. Therefore, the amount of liquid such as water is surely reduced, and in this case, it is determined that there is a pinhole. If there is no decrease in the amount of liquid such as water, it can be determined that there is no pinhole. The heating means may be heated indirectly via water, that is, it is safe and sufficient if heated indirectly via hot water or the like. As the sealing means, a bag made of a synthetic resin such as vinyl is sufficient.

  However, since it is possible that the decrease in liquid such as water is not apparent, it is necessary to measure before and after the determination. If the bag has a hole, an accurate determination cannot be made. Therefore, it is necessary to confirm that the hole has not been opened after the determination. The method is to check that air does not leak by putting a proper amount of air into a sealed storage member such as a plastic bag after the determination and resealing it, and applying pressure in the water tank. That is, when the air is sealed in an empty sealed housing member from which the liquid has been collected and positioned in water, the sealed housing member is pressurized from the outside. The determination result of the presence or absence of the pinhole is not effective without a hole, and if a bubble comes out from the sealed housing member, the sealed storage member has a hole and the determination result of the presence or absence of the pinhole is invalid Just judge.

  In addition to water, chemicals such as alcohols, organic solvents, and hydrofluoric acid can be used as the liquid used in the method of the present invention, but water is the safest.

  According to the present invention, it is possible to easily and reliably determine the presence or absence of a SiC-coated pinhole in a porous graphite member coated with SiC.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. 1 and 2 in the accompanying drawings. However, the illustrated examples show preferred embodiments of the present invention, and as long as they do not depart from the technical idea of the present invention. Needless to say, various modifications are possible.

  FIG. 1 is a schematic explanatory view showing one embodiment of the method of the present invention in the order of steps. (A) is a step of putting a susceptor and measured water in a plastic bag and sealing it, and (b) is putting a susceptor and water. The step of heating the plastic bag, (c) heating and cooling for a predetermined time, opening the plastic bag and collecting the water, (d) comparing the recovered amount of water with the initial amount of water, The step of determining the presence or absence, (e) shows the step of checking the presence or absence of a hole in the used plastic bag. FIG. 2 is a flowchart in the order of steps in FIG. In FIG. 1, the susceptor is indicated by the same reference numeral as in FIG.

  In the present embodiment, a case where a susceptor is used as a porous graphite member coated with SiC, water as a liquid, and a plastic bag as a sealed housing member will be described. First, a plastic bag 10 is used as a sealed storage member, and an initial amount of water 14 measured with a susceptor 36 and a measuring container 13 is placed therein, and the seal portion 15 of the plastic bag 10 is sealed at room temperature using a sealer (see FIG. 1 (a) and step 100 of FIG. The initial amount of this water 14 is required to be the minimum amount that becomes water vapor in the heating process described later, passes through the pinhole, and is adsorbed on the porous graphite member (susceptor), and is too much to evaporate. If there is still water (hot water), the susceptor is immersed in water and water vapor cannot pass through the pinhole. Therefore, the water becomes steam when heated and the inside of the plastic bag 10 becomes saturated water vapor and It is preferable to seal the initial amount of water in the plastic bag 10 so that water remains slightly.

  Next, the plastic bag 10 containing the susceptor 36 and the water 14 is put into a water tank 18 with a heater 16 and heated with hot water for about 1 hour, so that the water 14 becomes steam 14a (FIGS. 1B and 2). Step 102). Thereafter, the heated plastic bag 10 is cooled to room temperature with cold water (step 104 in FIG. 2). A cooling time of about 15 minutes is sufficient. Next, the plastic bag 10 is opened, the susceptor 36 is taken out, and the water 14 is collected (step 106 in FIG. 1 (c) and FIG. 2). Comparing the recovered amount of water 14 with the initial amount 14A and the recovered amount 14B, in the susceptor 36 having a pinhole, the amount of recovered water 14B is smaller than the initial amount of water 14A because water is adsorbed to the pinhole. . Therefore, when the recovered amount of water 14B is smaller than the initial amount of water 14A, it is determined that the susceptor 36 has a pinhole (FIG. 1 (d)). Further, when the water recovery amount 14B is not smaller than the initial water amount 14A, it is determined that there is no pinhole in the susceptor 36 (step 108 in FIG. 2).

  Subsequently, an appropriate amount of air is put into the plastic bag 10 after the above determination, and the seal portion 15 of the plastic bag 10 is resealed using a sealer, placed in a water tank 22 of room temperature water 20, and pressure is applied with both hands. Then, it is confirmed whether air leaks, that is, the bubbles 24 are emitted or not (step 110 in FIG. 1 (e) and FIG. 2). If bubbles appear, a hole is formed in the plastic bag 10, and if no bubbles are generated, it can be confirmed that no hole is formed in the plastic bag 10. If it can be confirmed that there is no hole in the plastic bag 10, the determination result that the susceptor 36 has a pinhole is valid.

  The present invention will be described below with reference to examples, but it is needless to say that the examples are illustrative and should not be construed restrictively.

Example 1
As the susceptors, 8 susceptors (susceptors suspected of having pinholes), which are porous graphite members coated with SiC that have been used due to the occurrence of defective wafers as shown in FIGS. used. In the procedure shown in FIGS. 1 and 2, the susceptor and 20 cc of the initial amount of water were placed in a plastic bag (length 30 cm × width 25 cm), and heated in a water tank with a heater for 1 hour with hot water. Next, the heated plastic bag was cooled to room temperature with cold water (about 15 minutes), the plastic bag was opened, the susceptor was taken out, and water was collected. The recovered amount of water was 0 to 10 cc. When the initial amount of water and the recovered amount were compared, the recovered amount of water was lower than the initial amount in any of the eight susceptors. Therefore, it was determined that all eight susceptors had pinholes.

(Example 2)
About 10 susceptors (pinhole susceptors) that were determined to have pinholes in the vacuuming pinhole test, the results of a determination experiment for the presence or absence of pinholes in the susceptor were conducted as in Example 1. 0 to 5 cc. When the initial amount of water and the recovered amount were compared, the recovered amount of water was smaller than the initial amount in all 10 susceptors. Therefore, it was determined that 10 susceptors had pinholes.

(Example 3)
Pinholes in the susceptor in the same manner as in Example 1 with respect to five susceptors (normal susceptors) that were not used due to the generation of defective wafers as shown in FIGS. As a result of carrying out a determination experiment on the presence or absence of water, the amount of water recovered was 20 cc. When the initial amount of water and the recovered amount were compared, the recovered amount of water was not decreased from the initial amount in any of the five susceptors. Therefore, it was determined that all five sheets had no pinholes.

  From the above, it has been proved that the method of the present invention is effective in determining the susceptor pinhole. In addition, the susceptor that has been discontinued due to the defective wafer shown in FIGS. 5 (a) and 5 (b), that is, the susceptor that has been discontinued due to the suspected pinhole after the installation of the device, This is about 1.6%, and after the determination of the presence or absence of pinholes in the susceptor according to the method of the present invention, this is reduced to 0%, and it is estimated that the generation of defective products can be reduced in the future.

BRIEF DESCRIPTION OF THE DRAWINGS It is typical explanatory drawing which shows one embodiment of the method of this invention in order of a process, (a) puts a susceptor and measured water in a plastic bag, and seals, (b) is a plastic bag which put a susceptor and water. (C) is a process of heating and cooling for a predetermined time and then opening the plastic bag to recover the water, and (d) comparing the recovered water and the initial amount of water to determine the presence or absence of a pinhole. A process and (e) show the process of confirming the presence or absence of the hole of the used plastic bag, respectively. It is a flowchart of the order of the process of FIG. It is the typical sectional view showing the conventional vapor phase growth apparatus. It is drawing which shows the result of the microscope picture of the pinhole of a susceptor. It is drawing which shows the state when image | photographing the defect of a wafer when the pinhole is open to a susceptor, (a) shows the state image | photographed from the upper surface, (b) shows the state image | photographed from 45 degree | times diagonally. It is a map figure which shows the result of an internal impurity measurement.

Explanation of symbols

  10: Airtight storage member (plastic bag), 13: Metering container, 14: Liquid (water), 14a: Steam (water vapor), 14A: Initial amount of water, 14B: Amount of recovered water, 15: Seal part, 16: Heater, 18: Water tank with heater, 20: Room temperature water, 22: Room temperature water tank, 24: Bubble, 30: Vapor growth apparatus 31: Chamber, 32: Chamber base 32, 33: Support base, 35: Semiconductor substrate, 36: susceptor, 36a: opening, 37: source gas introduction unit, 38: source gas nozzle, 38a: hole, 39: coil, 40: source gas discharge port, 50: pinhole, 52: pinhole mark, 54: thick line Hatched part.

Claims (6)

  A step of sealingly storing a porous graphite member coated with SiC and an initial amount of liquid in a sealed storage member at room temperature; heating the porous graphite member and the sealed storage member sealingly storing the liquid; A step of cooling the sealed housing member to room temperature after completion of the heating step, a step of recovering the liquid in the sealed housing member, and a step of comparing the initial amount of the liquid and the recovered amount of the recovered liquid And when the recovery amount of the liquid is smaller than the initial amount of the liquid, it is determined that a pinhole is present in the SiC coating, and the recovery amount of the liquid is decreased from the initial amount of the liquid. If not, it is determined that there is no pinhole in the SiC coating. A method for determining the presence or absence of pinholes in an SiC coating in a porous graphite member coated with SiC.   The pinhole presence / absence determination method according to claim 1, wherein the liquid is water.   3. The pinhole presence / absence determination method according to claim 1, wherein the porous graphite member coated with SiC is a susceptor.   The pinhole presence / absence determination method according to any one of claims 1 to 3, wherein the hermetic housing member is heated by indirect heating in which water is interposed outside the hermetic housing member.   The pinhole presence / absence determination method according to claim 1, wherein the sealed housing member is made of a synthetic resin sheet.   The sealed housing member is pressurized from the outside in a state where air is sealed in the empty sealed housing member from which the liquid has been collected and is positioned in water. If no air bubbles are generated from the sealed housing member, the sealed housing member has a hole. The determination result of presence / absence of the pinhole is not open and the determination result of the presence / absence of the pinhole is valid, and if a bubble comes out from the sealed storage member, it is determined that the determination result of the presence / absence of the pinhole is invalid. The pinhole presence / absence determination method according to any one of claims 1 to 5.

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