JP4769439B2 - Processing equipment - Google Patents

Description

  The present invention relates to a processing apparatus for decomposing a silicon substrate when analyzing impurities in the silicon substrate.

In recent years, with the improvement in performance of semiconductors, impurities contained in silicon substrates have a great influence on the performance of semiconductors.
Therefore, it is necessary to accurately analyze the amount of impurities contained in the silicon substrate. Instead of indirect impurity analysis methods such as electrical characteristics, a method of directly measuring impurities by dissolving the silicon substrate is adopted. ing.
Such a method is performed by using a processing apparatus including a silicon substrate and a hermetically sealed container for storing a decomposition solution of the silicon substrate. Specifically, it arrange | positions in the said airtight container, without making a silicon substrate contact a decomposition solution directly. Then, the sealed container is pressurized and heated to vaporize the decomposition solution and contact with the silicon substrate. As a result, the silicon component of the silicon substrate is sublimated, leaving only impurities. The remaining impurities are collected and analyzed (for example, see Patent Document 1).

Japanese Patent No. 3051023 (pages 4 to 6, FIG. 1)

However, in the method described above, since the decomposition liquid is vaporized, the vapor of the decomposition liquid is condensed on the upper surface portion of the container, and water drops fall on the silicon substrate. Since a trace amount of metal impurities may be present on the back surface (the inner surface of the container) of the upper surface portion of the container, a trace amount of metal impurities may be mixed into the condensed water droplets. Therefore, there is a problem that the water droplet falls on the silicon substrate, the silicon substrate is contaminated by a trace amount of metal impurities in the water droplet, and the analysis accuracy is lowered.
Here, as in Patent Document 1, there is a method of adopting a structure for curving the upper surface portion of the container in a curved shape and preventing a drop of water from dropping from the upper surface portion, but even if such a structure is adopted, It is difficult to reliably prevent a decrease in analysis accuracy because there is a possibility that water droplets containing condensation on the upper surface portion and containing a trace amount of metal impurities may fall.

  The objective of this invention is providing the processing apparatus which can prevent the fall of the analysis precision of an impurity.

The processing apparatus of the present invention is a processing apparatus for vaporizing a decomposition solution to decompose a silicon substrate to obtain impurities in the silicon substrate, which contains the silicon substrate and decomposes the silicon substrate. A container for storing a liquid in a lower part, a heating part that is disposed outside the container, heats the upper surface part and the lower surface part of the container, and vaporizes the decomposition liquid stored in the lower part of the container, and a side surface of the container And a plurality of substantially flat support plates disposed in the container and supporting each of the plurality of silicon substrates, each of the support plates being accommodated in a lower portion of the container. A recess having a depth of 10 mm or more, which is inclined at a predetermined angle with respect to the liquid surface of the decomposed liquid and arranged parallel to each other and accommodates the silicon substrate or a residue containing impurities after the silicon substrate is decomposed. Yes It is characterized by that.

According to the present invention, the heating unit for heating the silicon substrate and the upper surface portion of the container for storing the decomposition solution of the silicon substrate is installed, and the upper surface portion is heated to increase the temperature. Can be reliably prevented from condensing on the upper surface of the container. Thereby, it can prevent that a silicon substrate will be contaminated by the fall of the water droplet which condensed on the upper surface part, and can prevent the fall of analysis accuracy.
Furthermore, in the present invention, a heating unit that heats the upper surface portion of the container is provided, and condensation on the upper surface portion can be reliably prevented, so that it is not necessary to curve the upper surface portion of the container as in Patent Document 1, The structure of the container can be simplified.
Further, according to the present invention, since the heating unit heats not only the upper surface part of the container but also the lower surface part, the decomposition solution can be quickly vaporized, and further, the decomposition reaction of the silicon substrate can be performed. Since it can be promoted, the time required for the decomposition of the silicon substrate can be shortened.
And, by providing a heating unit that heats the upper and lower surfaces of the container, the decomposition reaction of the silicon substrate is promoted, and the time taken for the decomposition of the silicon substrate can be shortened, so the container is pressurized to promote the decomposition reaction There is no need to let them. Therefore, the container need not have a pressure-resistant structure, and the structure of the container can be simplified.
Here, examples of the cooling unit include a Peltier element and a cooling coil filled with a cooling medium (cooling liquid) such as an ethylene glycol liquid.
According to such this invention, since the side part of the container is cooled by the cooling unit, the temperature of the side part is lower than that of other parts. For this reason, condensation occurs on the side surface. Thereby, generation | occurrence | production of the dew condensation in the upper surface part of a container can be prevented more reliably.

According to the invention, such as this, the support plate for supporting the silicon substrate is substantially flat, are arranged inclined I also a predetermined angle in the container, parallel to the liquid surface of the decomposing solution Since it is not arranged, vaporization of the decomposition solution is not hindered. Thereby, the silicon substrate can be efficiently decomposed.
Also, substantially flat support plate is disposed inclined I also a predetermined angle to the liquid surface of the decomposing solution, since not in a state to cover the liquid surface of the decomposition solution, the vaporized The adhesion amount of the decomposition liquid to the back surface of the support plate can be reduced. As a result, the vaporized decomposition solution efficiently contacts the silicon substrate, and the silicon substrate is efficiently decomposed.
In addition, since the support plate for supporting the silicon substrate is disposed at a predetermined angle with respect to the liquid level of the decomposition liquid in the container, a large number of support plates are provided as compared with the case where the support plate is disposed substantially parallel to the liquid level. It can be placed in the container body. Thereby, since many silicon substrates can be decomposed, it becomes possible to efficiently analyze impurities on the silicon substrate.
Furthermore, a recess having a depth dimension of 10 mm or more is formed on the surface of the support plate, and since the silicon substrate is installed in the recess, there is no possibility that the residue after decomposition of the silicon substrate falls from the support plate. .

Furthermore, in the present invention, the temperature of the heating unit is preferably 70 ° C. or higher and 230 ° C. or lower.
When the temperature of the heating part is less than 70 ° C., there is a possibility that the occurrence of condensation cannot be reliably prevented. Moreover, when it exceeds 230 degreeC, a container may raise | generate a deformation | transformation.
In the present invention, since the temperature of the heating section is set to 70 ° C. or higher and 230 ° C. or lower, the occurrence of condensation can be reliably prevented and the deformation of the container can be prevented.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a processing apparatus 1 of the present embodiment.
This processing apparatus 1 is for obtaining impurities contained in the silicon substrate 21 by decomposing the silicon substrate 21 with the evaporated decomposition solution 22. Here, examples of impurities contained in the silicon substrate 21 include Fe, Al, Na, Ni, and K.
The diameter of the silicon substrate 21 used in the present embodiment is, for example, 200 mm to 300 mm.

The processing apparatus 1 is installed in a draft (not shown), and includes a container 11 in which a silicon substrate 21 and a decomposition solution 22 are filled, a heating unit 12, and a support plate 13.
As shown in FIG. 2, the container 11 includes a rectangular parallelepiped container main body 111 having an upper surface opened, and a lid member 112 that closes the opening of the container main body 111.

The container main body 111 has a rectangular parallelepiped shape, and includes a lower surface portion 111A having a substantially rectangular plane shape, and four planar rectangular side surface portions 111B rising from the periphery of the lower surface portion 111A. The container body 111 is preferably made of a material that is not easily affected by the decomposition liquid 22, and is made of, for example, PTFE (polytetrafluoroethylene).
The lower surface portion 111A has a length dimension of, for example, 260 mm on one side and a length dimension of a side orthogonal to the one side, for example, 270 mm.
Moreover, the height dimension of the side part 111B is 280 mm, for example.

Of the side surface portions 111B, a pair of opposing side surface portions 111B1 are formed with a plurality of inclined grooves, for example, three grooves 111B11. The groove 111B11 extends from the upper end of the side surface portion 111B1 located on the opening side of the container main body 111 toward the lower end located on the lower surface portion 111A side.
In addition, the extension direction front-end | tip of this groove | channel 111B11 is located upwards, for example about 80 mm from 111 A of lower surface parts.
Each groove 111B11 is formed substantially in parallel. The width dimension T1 of the groove 111B11 is, for example, 20 mm. Moreover, it is preferable that the space | interval T2 between each groove | channel 111B11 is 10 mm or more, for example, is 15 mm.

Further, a notch 111B21 is formed at the upper end portion of the side surface portion 111B2 orthogonal to the side surface portion 111B1 in the side surface portion 111B. The side surface portion 111B2 is a side surface portion located on the front end side in the extending direction of the groove 111B11, and is a surface facing the surface of the silicon substrate 21 described later.
This notch 111B21 is formed along the upper end edge of the side surface portion 111B2, and when a lid material 112 described later is attached, as shown in FIG. Will be formed. That is, the hole 113 is formed in the upper portion of the side surface portion 111B2 of the container 11. The height dimension of the notch 111B21, in other words, the height dimension T3 of the hole 113 is preferably 1 mm or more, for example.
Such a container main body 111 is filled with the decomposition liquid 22. The height position of the liquid surface of the decomposition liquid 22 filled in the container main body 111 is lower than the height position of the tip in the extending direction of the groove 111B11.

The lid member 112 constitutes the upper surface portion of the container 11 and has a planar rectangular shape larger than the opening of the container body 111. A projecting portion 112 </ b> A having a substantially rectangular shape projecting toward the opening side of the container main body 111 is formed at a substantially central portion of the back surface of the lid member 112 located on the container main body 111 side. The protrusion 112A is fitted into the opening of the container body 111.
In addition, the planar shape of the projecting portion 112A is smaller than the planar shape of the opening of the container main body 111B. Accordingly, when the protruding portion 112A is fitted into the opening of the container main body 111B, the protruding portion 112A and the side surface portion 111B of the container main body 111B do not come into contact with each other.

When such a lid member 112 is attached to the container body 111, the protruding portion 112A is fitted into the opening of the container body 111, and the peripheral edge of the back surface of the lid member 112 is the upper end of the side surface portion 111B of the container body 111. The lid member 112 comes into contact with the edge and is supported by the side surface portion 111 </ b> B of the container main body 111. As described above, since the notch 111B21 is formed in the side surface portion 111B2, the slit-shaped hole 113 is formed between the rear surface peripheral portion of the lid member 112. The hole 113 constitutes an exhaust passage for exhausting the gas inside the container 11 to the outside.
In addition, like the container main body 111, such a lid | cover material 112 is preferably comprised with the raw material which is hard to be influenced by the decomposition liquid 22, for example, is made from PTFE (polytetrafluoroethylene).

The support plate 13 supports the silicon substrate 21 and is installed in the container 11 and has a substantially flat plate shape as shown in FIG. In the center of the surface of the support plate 13, a planar substantially circular recess 131 for installing and supporting the silicon substrate 21 is formed. The depth dimension of the recess 131 is, for example, 10 mm or more, and the silicon substrate 21 is placed in the recess 11 by placing the silicon substrate 21 in the recess 131 and inserting the support plate 13 into the groove 111B11 of the container body 111. Will be installed.
At this time, the support plate 13 and the silicon substrate 21 are located above the liquid surface of the decomposition liquid 22 filled in the container main body 111.
The back surface of the support plate 13 is located on the side of the decomposition liquid 22 when the support plate 13 is inserted into the groove 111B11 of the container body 111.

As described above, since the groove 111 </ b> B <b> 11 is formed to be inclined, when the support plate 13 is installed in the container 11, the back surface of the support plate 13 becomes the liquid surface of the decomposition liquid 22 filled in the container body 111. It will be inclined and arranged. As shown in FIG. 1, the inclination angle θ (the angle formed between the back surface of the support plate 13 and the liquid surface of the decomposition liquid 22) is preferably 30 ° or more and 65 ° or less.
Further, since three grooves 111B11 are formed in each of the side surface portions 111B1, in this embodiment, three support plates 13 can be installed in the container 11.
Furthermore, since the interval T2 of the groove 111B11 is 10 mm or more, the interval between the support plates 13 installed in the container body 111 is also 10 mm or more.

As shown in FIG. 1, the heating unit 12 heats the lid 112 that is the upper surface of the container 11 and the lower surface 111 </ b> A of the container main body 111 to vaporize the decomposition liquid 22 filled in the container 11. .
The heating unit 12 includes a pair of heating unit main bodies 121. Here, in the present embodiment, the heating unit main body 121 is a hot plate.
Of the pair of heating unit main bodies 121, one heating unit main body 121 is disposed on the lid member 112 that is the upper surface portion of the container 11 and is in contact with the lid member 112.
The other heating unit main body 121 is installed below the lower surface portion 111A of the container main body 111 and is in contact with the lower surface portion 111A.
The pair of heating unit main bodies 121 of the heating unit 12 heat the upper surface of the lid 112 and the entire lower surface 111 </ b> A of the container main body 111 at 70 ° C. or higher and 230 ° C. or lower.

Using the processing apparatus 1 as described above, the silicon substrate 21 is disassembled as follows.
First, the decomposition liquid 22 is filled into the container body 111. Here, in this embodiment, the decomposition liquid 22 contains hydrofluoric acid and nitric acid. For example, 50 wt% hydrofluoric acid and 70 wt% nitric acid are mixed at a volume ratio of 2: 1. It is a mixture.
In the present embodiment, the decomposition liquid 22 contains hydrofluoric acid and nitric acid. However, the present invention is not limited to this, and for example, the decomposition liquid 22 may contain hydrofluoric acid, nitric acid, and sulfuric acid.
Next, the silicon substrate 21 is installed in each of the recesses 131 of the three support plates 13 and placed in the container main body 111. Note that the silicon substrate 21 to be used is cleaned in advance.
Thereafter, the opening of the container body 111 is closed with the lid member 112, and the lower surface portion 111 </ b> A of the container 11 and the lid member 112 are heated by the heating unit 12. The decomposition of the silicon substrate 21 is completed in about 15 to 16 hours from the start of heating.
At this time, the decomposition liquid 22 is vaporized by heating of the heating unit 12, and the following reaction occurs inside the container 11, and the silicon substrate 21 is decomposed.

(Main reaction)
Si + 4HNO ₃ ↑ → SiO ₂ + 4NO ↑ + 2H ₂ O + 2O ₂ ↑ (1)
SiO ₂ + 4HF ↑ → SiF ₄ + 2H ₂ O (2)
SiF ₄ ↑ + 2HF ↑ → H ₂ SiF ₆ (3)
H ₂ SiF ₆ + 3H ₂ O → H ₂ SiO ₃ ↓ + 6HF ↑ (4)
(Side reaction)
2NO + O ₂ ↑ → 2NO ₂ ↑ ・ ・ ・ (5)
SiF ₄ ↑ + 2H ₂ O → 4HF ↑ + SiO ₂ (6)

In the present embodiment, a gap is formed between the protruding portion 112A of the lid member 112 and the side surface portion 111B of the container main body 111B, and a hole 113 is formed in the container 11. Furthermore, since the processing apparatus 1 is installed in the draft, the gas inside the container 11 is discharged to the outside. Therefore, nitrogen dioxide or SiF ₄ which is a by-product gas generated with the decomposition reaction is discharged from the container 11. Note that from the container 11, with 1L / min or faster, nitrogen dioxide, which is a by-product gas, it is preferable that the SiF ₄ is discharged.

After about 15 to 16 hours, the support plate 13 is removed from the container 11. As shown in FIG. 4, a residue 23 containing impurities in the silicon substrate 21 exists in the recess 131 of the support plate 13.
Next, a solution 24 for dissolving the residue 23 is dropped onto the surface of the residue 23. The solution 24 is, for example, a mixture of 68 wt% nitric acid, 36 wt% hydrochloric acid, and pure water at a volume ratio of 1: 1: 1.
In the present embodiment, a solution obtained by mixing 1 ml each of the nitric acid, hydrochloric acid, and pure water is used as the solution 24. As the solution 24, a mixture of nitric acid, hydrochloric acid, pure water, and sulfuric acid may be used.
Thereafter, as shown in FIG. 5, the dissolved matter 25 of the residue 23 is collected in a beaker 26 or the like and heated by the heating means 27 such as a hot plate until the solution 24 evaporates. Thereby, the silicon component in the residue 23 is removed, and the impurities in the silicon substrate 21 can be obtained. The heating temperature by the heating means 27 is, for example, 100 ° C. or more and 200 ° C. or less.
Thereafter, the impurities are diluted and analyzed by an inductively coupled plasma mass spectrometer, an atomic absorption spectrometer or the like.

Therefore, according to this embodiment, the following effects can be produced.
(1) Since the heating unit main body 121 of the heating unit 12 is installed on the silicon substrate 21 and the lid member 112 of the container 11 filled with the decomposition solution 22 of the silicon substrate 21, the vapor of the decomposition solution 22 is vaporized by the lid member 112. It is possible to reliably prevent dew condensation on the back surface. Thereby, it is possible to prevent the silicon substrate 21 from being contaminated due to the drop of water droplets condensed on the back surface of the lid member 112, and to prevent the analysis accuracy of impurities in the silicon substrate 21 from being lowered.

(2) In addition, there is a structure in which the upper surface of the container is curved in order to prevent water droplets condensed on the upper surface of the container from falling onto the silicon substrate 21, but when such a structure is employed, There is a problem that the structure becomes complicated.
On the other hand, in this embodiment, the heating unit main body 121 of the heating unit 12 is provided on the lid member 112, and condensation on the back surface of the lid member 112 can be reliably prevented. It is not necessary to bend the material 112, and the structure of the container 11 can be simplified. That is, the shape of the back surface of the lid member 112 can be configured as a substantially flat surface, and labor is not required for manufacturing the lid member 112.

(3) Furthermore, in this embodiment, since the heating unit body 121 of the heating unit 12 is provided not only on the upper part of the lid member 112 of the container 11 but also on the lower surface part 111A of the container body 111, the decomposition liquid 22 Can be rapidly vaporized, and further, the decomposition reaction of the silicon substrate 21 can be promoted, so that the time required for the decomposition of the silicon substrate 21 can be shortened.
Furthermore, since the decomposition liquid 22 can be quickly vaporized and the decomposition reaction of the silicon substrate 21 can be promoted in this way, a plurality of silicon substrates 21 are placed in the container 11 and processed simultaneously. Is possible.

(4) In addition, the decomposition reaction of the silicon substrate 21 is promoted by providing the heating part main body 121 of the heating part 12 at the upper part of the lid member 112 of the container 11 and the lower part of the lower surface part 111A of the container main body 111 as described above. Since the time required for the decomposition of the silicon substrate 21 can be shortened, it is not necessary to pressurize the container 11 to promote the decomposition reaction. Therefore, the container 11 does not need to have a pressure resistant structure, and the structure of the container 11 can be simplified.

(5) When the temperature of the heating unit 12 is less than 70 ° C., there is a possibility that condensation cannot be reliably prevented. Further, when the temperature of the heating unit 12 exceeds 230 ° C., the container 11 may be deformed.
In this embodiment, since the temperature of the heating unit 12 is set to 70 ° C. or higher and 230 ° C. or lower, the occurrence of condensation and the deformation of the container 11 can be reliably prevented.

(6) Further, the support plate 13 for supporting the silicon substrate 21 is a substantially flat, are arranged inclined I also a predetermined angle in the container body 111 of the container 11, the liquid of the decomposition liquid 22 Since it is not arranged parallel to the surface, vaporization of the decomposition liquid 22 is not hindered. Thereby, decomposition | disassembly of the silicon substrate 21 can be performed efficiently.

(7) In addition, substantially flat support plate 13 is arranged inclined I also a predetermined angle to the liquid surface of the decomposing solution 22, in a state to cover the liquid surface of the decomposing solution 22 Therefore, the amount of vaporized decomposition liquid 22 attached to the back surface of the support plate 13 can be reduced. As a result, the vaporized decomposition solution 22 comes into contact with the silicon substrate 21 efficiently, and the silicon substrate 21 is decomposed efficiently.

(8) Moreover, since the place I also predetermined angle support plate 13 for supporting the silicon substrate 21 to the liquid surface of the decomposing solution 22 in the container 11, substantially arranged parallel to the liquid surface Compared to the case, a large number (three in the present embodiment) of the support plates 13 can be arranged in the container main body 111. Thereby, a large number (three in this embodiment) of the silicon substrates 21 can be decomposed, so that the impurities on the silicon substrate 21 can be analyzed efficiently.

(9) Further, a recess 131 having a depth dimension of 10 mm or more is formed on the surface of the support plate 13, and the silicon substrate 21 is installed in the recess 131. There is no possibility of falling from the support plate 13.

(10) When the interval between the adjacent support plates 13 is less than 10 mm, the evaporated decomposition solution 22 is less likely to contact the silicon substrate 21 installed on the support plate 13, and the decomposition rate of the silicon substrate 21 is increased. May be reduced.
On the other hand, in this embodiment, since the interval between the adjacent support plates 13 is set to 10 mm or more, the evaporated decomposition solution 22 reliably comes into contact with the silicon substrate 21, and the decomposition rate of the silicon substrate 21 is reduced. Decline can be prevented.

(11) When the inclination angle of the support plate 13 with respect to the liquid surface of the decomposition liquid 22 is less than 30 °, the liquid surface is covered with the support plate 13, so that the vaporization of the decomposition liquid 22 is hindered by the support plate 13. There is a possibility that. In addition, when the angle of the support plate 13 with respect to the liquid surface of the decomposition liquid 22 is less than 30 °, the vaporized decomposition liquid 22 may adhere to the back surface of the support plate 13 in a large amount.
Furthermore, if the angle of the support plate 13 with respect to the liquid surface of the decomposition liquid 22 exceeds 65 °, the residue 23 generated along with the decomposition of the silicon substrate 21 may fall from the support plate 13. Yes, not preferred.
In the present embodiment, since the angle of the support plate 13 with respect to the liquid surface of the decomposition liquid 22 is set to 30 ° or more and 65 ° or less, occurrence of such a problem can be prevented.

(12) In addition, since the container 11 is formed with a hole 113 which is an exhaust passage for discharging the gas inside the container 11 to the outside, the secondary gas generated from the container 11 along with the decomposition reaction is formed. Nitrogen dioxide, which is a product gas, is discharged. Thereby, suppression of evaporation of the decomposition liquid due to excessive accumulation of nitrogen dioxide can be prevented, and the decomposition liquid 22 is efficiently evaporated. For this reason, the decomposition rate of the silicon substrate 21 can be improved.
Further, since the container 11 is formed with a hole 113 which is an exhaust passage for discharging the gas inside the container 11 to the outside of the container 11, SiF ₄ is discharged from the container 11. Accordingly, the reaction according to the above-described reaction formula (3) does not easily proceed, and hydrofluoric acid is used only for the decomposition reaction of the silicon substrate 21. As a result, the decomposition rate of the silicon substrate 21 can be improved.
Furthermore, in this embodiment, since the decomposition of the silicon substrate 21 can be promoted in this way, it is not necessary to pressurize the container 11, and the container 11 does not have to have a pressure-resistant structure, so the structure of the container 11 is simplified. can do.

(13) In the present embodiment, a notch 111B21 is formed in the side surface portion 111B2 of the container body 111, and a slit-like hole 113 is formed between the notch 111B21 and the back surface peripheral edge portion of the lid member 112. Therefore, the gas inside the container 11 can be reliably discharged.
Furthermore, since the slit-shaped hole 113 extends along the upper end edge of the side surface portion 111B2, and its height dimension T3 is 1 mm or more, the gas inside the container 11 can be discharged more reliably.

(14) The residue 23 obtained by decomposing the silicon substrate 21 with the decomposition solution 22 has a property of being easily dissolved in water. In this embodiment, pure water is added to the solution 24. It can be easily dissolved. Thereby, the impurities in the residue 23 can be reliably recovered, and the impurities can be analyzed more accurately.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the above-described embodiment, the lower surface portion 111A of the container body 111 is heated by the other heating unit body 121 of the heating unit 12. However, the present invention is not limited to this. The lower end portion of the side surface portion 111B may be heated.

Further, in addition to the pair of heating unit main bodies 121, a new heating unit main body is provided, the heating unit main body is brought into contact with the side surface part 111B of the container main body 111, and the lid member 112, which is the upper surface part of the container main body 111, the lower surface part You may heat 111A and the side part 111B.
In this way, the decomposition liquid 22 can be efficiently vaporized by heating the side surface portion 111B as well.
Furthermore, in the said embodiment, although the lid | cover material 112 of the container 11 and the lower surface part 111A of the container main body were heated by the heating part 12, you may heat only the lid | cover material 112 of the container 11. FIG.
In this way, when only the lid member 112 of the container 11 is heated, the heating part main body for heating the lower surface part 111A becomes unnecessary, so that the number of members can be reduced.
Furthermore, in the above-described embodiment, the heating unit body 121 of the heating unit 12 is a hot plate. However, the present invention is not limited to this. For example, the heating unit body 121 that heats the lower surface portion 111A of the container body 111 is configured by an oil bath or the like. May be.

  In the embodiment, the condensation of the vapor of the decomposition liquid 22 on the back surface of the lid member 112 is prevented only by heating the lid member 112. However, the present invention is not limited to this. As shown in FIG. 6, a cooling unit 14 that cools the side surface part 111 </ b> B of the container main body 111 may be provided. The cooling unit 14 includes a Peltier element 141, a heat radiating plate 142, and a fan (not shown). Although not specifically shown, the Peltier element 141 has a plurality of junction pairs configured by joining a p-type semiconductor and an n-type semiconductor with metal pieces, and the plurality of junction pairs are electrically connected in series. And a direct current flows from the n-type semiconductor to the p-type semiconductor or from the p-type semiconductor to the n-type semiconductor.

  Here, when a direct current is passed from the n-type semiconductor to the p-type semiconductor, the metal piece is cooled and heat can be taken away from the surroundings. On the contrary, when a direct current is passed from the p-type semiconductor to the n-type semiconductor, the metal piece is heated, and heat can be released to the surroundings. In the Peltier element 141 having such a configuration, when a direct current is passed, one surface on the side surface portion 111B side of the Peltier element 141 becomes a heat absorbing portion that absorbs heat, and the other surface becomes a heat generating portion that generates heat. . The heat of the heat generating portion is radiated from the heat radiating plate 142 and cooled by a fan (not shown). Thereby, the heat | fever of the side part 111B can be absorbed, and the side part 111B can be made to form condensation by cooling the side part 111B. Therefore, it is possible to effectively prevent the condensation of the vapor of the decomposition liquid 22 on the back surface of the lid member 112.

In the said embodiment, although the container 11 was a rectangular parallelepiped shape, the shape of a container is arbitrary and may be a column shape, for example.
Moreover, in the said embodiment, although the temperature of the heating part 12 was 70 degreeC or more and 230 degrees C or less, when the heat resistance of the container 11 is very high, it is good also as what exceeds 230 degreeC.

In the embodiment, the notch 111B21 is formed in the container main body 111 of the container 11, and the hole 113 is formed in the side surface 111B of the container 11 by attaching the lid member 112 to the container main body 111. However, the present invention is not limited to this, and a perfectly shaped hole may be formed in the side surface portion 111B.
Furthermore, in the said embodiment, although the notch part 111B21 was formed in the container main body 111 of the container 11, this notch part 111B21 does not need to be. For example, when a gap is formed between the container main body 111 and the lid member 112 so that a predetermined amount of gas (for example, 1 L / min or more) can pass, without forming the notch 111B21, This gap may be used as an exhaust passage. By doing in this way, the effort which forms notch 111B21 in the container main body 111 can be saved.

In the above-described embodiment, a plurality of support plates 13 can be installed in the container 11, but only one support plate 13 may be installed. By doing in this way, since the number of groove | channels 111B11 formed in the side part 111B can be reduced, a labor is not required for manufacture of a container main body.
Furthermore, in the said embodiment, although the space | interval between the support plates 13 was 10 mm or more, not only this but less than 10 mm may be sufficient.
In the said embodiment, although the angle with respect to the liquid level of the decomposition liquid 22 of the support plate 13 was 30 degrees or more and 65 degrees or less, the said angle may be out of this range. For example, if the silicon substrate 21 on the support plate 13 does not fall from the support plate 13, the angle may exceed 65 °. In such a case, it is preferable to increase the depth of the recess 131 of the support plate 13.

  Moreover, in the said embodiment, although the support plate 13 was inclined and arrange | positioned with respect to the liquid level of the decomposition liquid 22, it is not restricted to this and the support plate 13 does not need to be arrange | positioned. For example, the support plate 13 may be disposed so as to be substantially parallel to the liquid surface of the decomposition liquid 22.

Next, examples of the present invention will be described.
(Example)
The silicon substrate 21 was decomposed using the processing apparatus 1 of the embodiment.
First, a decomposition solution 22 was prepared by mixing 50 wt% hydrofluoric acid and 68 wt% nitric acid at a volume ratio of 2: 1.
Next, the decomposition liquid 22 was filled into the container main body 111 of the processing apparatus 1. Thereafter, two support plates 13 on which the silicon substrate 21 was installed and one support plate 13 on which the silicon substrate 21 was not installed were installed in the container body 111. At this time, the silicon substrate 21 is located above the liquid surface of the decomposition liquid 22. Further, the support plate 13 on which the silicon substrate 21 was not installed was inserted into the groove 111B11 closest to the hole 113 of the container 11.

Next, the opening of the container main body 111 was closed by the lid member 112, and the lower surface portion 111A and the lid member 112 of the container main body 111 were heated by the heating unit 12 that is a hot plate. At this time, the temperature of the heating unit 12 was set to 85 ° C. or more and 125 ° C. or less.
After 15 hours, the silicon substrate 21 was completely decomposed.
Thereafter, the support plate 13 on which the silicon substrate 21 was not installed was taken out of the container 11, and a solution 24 in which 68 wt% nitric acid, 20 wt% hydrochloric acid and ultrapure water were mixed was dropped onto the support plate 13. Thereafter, the liquid on the support plate 13 was collected in the beaker 26, 98 wt% sulfuric acid was added, and the mixture was heated at 170 ° C. by the heating means 27 that was a hot plate. Thereafter, ultrapure water was added for dilution, and this was quantitatively analyzed with an inductively coupled plasma mass spectrometer.

(Comparative example)
The heating unit 12 on the lid 112 of the processing apparatus 1 was not used. The decomposition of the silicon substrate 21 took 18 hours. Other conditions are the same as in the example.

(result)
In the example, the decomposition of the silicon substrate 21 took 15 hours, but in the comparative example, the decomposition of the silicon substrate 21 took 18 hours.
In the example, when the decomposition of the silicon substrate 21 was completed, no water droplets adhered to the back surface of the lid member 112, and no water droplets dropped on the support plate 13.
On the other hand, in the comparative example, when the decomposition of the silicon substrate 21 was completed, a large amount of water droplets adhered to the back surface of the lid member 112, and several ml of water droplets were dropped on the support plate 13.
FIG. 7 shows an analysis result of the amount of each element (contamination amount of the support plate 13) existing on the support plate 13 on which the silicon substrate 21 is not installed.
In the example, since no water droplets were dropped on the support plate 13, the contamination on the support plate 13 was hardly confirmed. Thereby, in the Example, it was confirmed that the silicon substrate 21 on the support plate 13 is not contaminated and the analysis accuracy is not lowered.
On the other hand, in the comparative example, a large amount of each element was present on the support plate 13, and contamination of the support plate 13 could be confirmed. That is, in the comparative example, it was confirmed that the silicon substrate 21 on the support plate 13 was contaminated and the analysis accuracy was lowered.
From the above, it was possible to confirm the effect of the present invention that the decomposition rate of the silicon substrate can be increased and the deterioration of the impurity analysis accuracy can be prevented.

  The present invention can be used for analyzing impurities in a silicon substrate.

It is sectional drawing which shows the processing apparatus concerning embodiment of this invention. It is a disassembled perspective view which shows the container of the said processing apparatus. It is a perspective view which shows the support plate of the said processing apparatus. It is a schematic diagram which shows a mode that the residue on a support plate is melt | dissolved. It is a schematic diagram which shows a mode that the melt | dissolution of a residue is collect | recovered by a beaker and it heats with a heating means. It is sectional drawing which shows the modification of this invention. It is a figure which shows the result of an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Processing apparatus 11 Container 12 Heating part 13 Supporting plate 14 Cooling part 21 Silicon substrate 22 Decomposition liquid 23 Residue 24 Dissolution liquid 25 Dissolved substance 26 Beaker 27 Heating means 111 Container main body 111A Lower surface part 111B Side surface part 111B1 Side surface part 111B2 Side surface part 111B11 Groove 111B21 Notch 112 Lid 112A Protrusion 113 Hole 121 Heating unit body 131 Recess 141 Peltier element 142 Heat sink

Claims (2)

A processing apparatus for vaporizing a decomposition solution to decompose a silicon substrate to obtain impurities in the silicon substrate,
A container for storing the silicon substrate and storing a decomposition solution of the silicon substrate in a lower portion;
A heating unit that is disposed outside the container, heats the upper surface portion and the lower surface portion of the container, and vaporizes the decomposition liquid stored in the lower portion of the container;
A cooling part for cooling the side part of the container;
A plurality of substantially flat support plates disposed in the container and respectively supporting the plurality of silicon substrates;
Each of the support plates is inclined at a predetermined angle with respect to the level of the decomposition solution stored in the lower part of the container, and is arranged in parallel to each other, so that the silicon substrate or the impurities after decomposition of the silicon substrate are removed. A processing apparatus characterized by having a recess having a depth of 10 mm or more for accommodating a residue to be contained. The processing apparatus according to claim 1,
The temperature of the said heating part is 70 degreeC or more and 230 degrees C or less, The processing apparatus characterized by the above-mentioned.

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