JPH062236Y2 - Curved heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a quartz tube heater for heating an etching solution used in an etching process of semiconductor manufacturing.

[Prior Art] One of the processes for manufacturing semiconductors such as IC and LSI is an etching process for removing the Si oxide film formed on a silicon wafer. In this step, only the thin Si oxide film formed in the acid treatment step of the previous step is removed, and the etching rate and etching time are set so as to minimize the corrosion of the Si oxide film which is originally necessary as a diffusion mask or a gate insulating film. Is carefully managed. A phosphoric acid solution is usually used as the etching solution, and is maintained at about 180 ° C. to obtain an appropriate etching rate. To heat the etching solution, a so-called throw-in type heater is used, in which the heating portion is immersed in the etching solution. In particular, a quartz tube heater in which a heating element is covered with a quartz tube that is relatively unlikely to be corroded by phosphoric acid is used. It is used. A conventional quartz tube heater is composed of a heating element such as a nichrome wire or a kanthal wire and a quartz tube that surrounds the heating element and insulates it from the etching solution. The coil has a winding diameter slightly smaller than the inner diameter of the quartz tube.

[Problems to be Solved by the Invention] In the conventional quartz tube heater configured as described above,
As shown in the figure, the coiled nichrome wire 3 is
The part of the quartz tube 2 that is in direct contact with the inner wall surface of the tube in a coiled shape and is in contact with it, and the portion of the quartz tube 2 that is in contact with the nichrome wire 3 is locally heated and is extremely hot (about 700 ° C )
Becomes The quartz tube is relatively hard to be corroded by phosphoric acid, but at a high temperature, the reaction rate of being corroded is high, and finally a pinhole is generated in this portion. When a pinhole occurs, the work of the etching process must be interrupted, which makes it difficult to control the etching time, and there is a high risk that the wafer will become unusable. In order to avoid this, the quartz tube heater is also replaced at regular intervals. In the case of continuous use, it has to be replaced in about one week, at most in about one month, and the conventional quartz tube heater has a drawback that the life is very short.

Therefore, the object of the present invention is to provide a quartz tube heater which is prevented from being locally heated and has a longer life than conventional ones.

[Means for Solving the Problems] In order to solve the above problems, a curved tube heater according to the present invention includes an elongated heating element and a curved tube that surrounds the heating element and insulates the heating element. The heating element is supported by the curved tube via a support piece arranged near the heating element.

Preferably, the heating element is supported by the curved tube via beads attached to the heating element at appropriate intervals.

Further, the heating element may be supported by the curved tube via a granular material filled in the curved tube.

Further, preferably, the curved tube is a quartz tube bent into a predetermined shape.

[Operation] In the curved tube heater according to the present invention configured as described above, the heating element is supported by the curved tube through the support piece arranged in the vicinity thereof, and the curved tube is locally supported only by a certain portion. Never supported by. The heat generated by the heating element is transmitted to the curved tube through the support piece. For this reason, it is avoided that a high temperature is locally generated by being locally transmitted to the curved pipe, and local promotion of erosion is suppressed. Therefore, the life of the bent tube heater can be extended.

When the heating element is supported by the curved tube via the beads attached to the heating element at appropriate intervals, the heat of the heating element is transferred to the wall of the curved tube through the beads, The temperature does not become so high even at the place where it is in contact with the beads. Further, when the heating element is supported by the curved tube through the granules filled in the curved tube, the heat of the heating element is not directly transmitted to the tube wall of the curved tube, but the granular body. Is distributed through. For this reason, it is possible to avoid the temperature of the curved tube heater from locally increasing.

[Embodiment] With reference to the drawings, a quartz tube heater as an embodiment of the curved tube heater according to the present invention will be described. A quartz tube heater 1 shown in FIG. 1 includes a quartz tube 2 that constitutes a curved tube and a nichrome wire 3 as a heating element, and the nichrome wire 3 is inserted into the quartz tube 2. The nichrome wire 3 may use other heat-generating materials such as Kanthal wire. The quartz tube 2 has a predetermined outer diameter,
This is a quartz glass tube formed by bending a tube having a wall thickness and a length into a predetermined shape, and in the example shown in FIG. 1, it is substantially U-shaped as a whole. In this embodiment, the quartz tube 2
Has a crank shape in which the U-shaped juxtaposed portions are raised at a right angle in the approximate center and are bent at a right angle again near the ends of the tube. Therefore, the quartz tube 2 is roughly , U-shaped portion 4, rising portions 5, 5 and end portions 6, 6.

A nichrome wire 3 having a predetermined wire diameter that is sufficiently smaller than the inner diameter of the quartz tube 2 is inserted into the quartz tube 2, and the nichrome wire 3 is U-shaped from one rising portion 5 of the quartz tube 2. It extends through the part 4 to the other rising part 5. As is apparent from the broken portion in FIG. 1, the both ends of the nichrome wire 3 are formed by the nickel crimp sleeve 7 at the rising portion 5 of the quartz tube 2.
Are connected to the nickel wires 8 and 8 respectively via
Here, in order to prevent heat generation, both ends of the nichrome wire are twisted so as to be doubled by an appropriate length. Each nickel wire 8 is further connected to a lead wire 10 at the end 6 of the quartz tube via a copper crimp sleeve 9, and therefore, from each end 6 of the quartz tube, a lead wire electrically connected to the nichrome wire 3 is formed. 10 are derived respectively.

Beads 11 are attached to the nichrome wire 3 at a predetermined interval over substantially the entire length excluding both ends.
The nichrome wire 3 has a coil shape having a winding diameter smaller than the inner diameter of the quartz tube 2 by a predetermined amount in a range substantially over the entire length of the U-shaped portion 4 of the quartz tube.

FIG. 2 is a cross-sectional view of the quartz tube heater 1 shown in FIG. 1, showing the details of the beads 11 attached to the coiled portion of the nichrome wire 3. Each bead 11
Is made of quartz glass and is attached to the nichrome wire 3 so as to surround the nichrome wire 3, that is, the nichrome wire 3 penetrates the beads 11. Beads 11
Are arranged at approximately equal intervals on the nichrome wire 3 wound in a coil shape, and in this case, they are arranged every quarter turn with respect to the winding of the coil, and in the range of the U-shaped portion 4, each bead 11 has nichrome. When mounted on the wire 3, the dimensions and the layout relationship are such that they contact the tube wall of the quartz tube 2, respectively. In this case, as shown in FIG. 2, the nichrome wire 3 is not in direct contact with the quartz tube 2 even in the portion where the beads 11 are not mounted. The size of each bead 11 and the interval between the beads are not limited to those shown in this embodiment, and any nichrome wire 3 may be used as long as it does not come into direct contact with the quartz tube 2.

The quartz tube heater 1 according to the present invention constructed as described above
Is used in a state in which at least the U-shaped portion 4 of the quartz tube 2 is immersed in the etching liquid for etching the wafer, and the end portion 6 is exposed on the liquid surface of the etching liquid. The power supply electrode is connected to the lead wire 10 extending from the end portion 6 and electric power is supplied, so that the nichrome wire 3 generates heat. In particular, the U-shaped portion 4 in which the nichrome wire 3 has a coil shape has a large amount of heat generation. On the other hand, in the rising portion 5 in which the nichrome wire 3 is connected to the nickel wire 8, the nichrome wire is doubled at its end, and therefore the amount of heat generated is relatively small. In the U-shaped portion 4 having a large amount of heat generation, the coiled nichrome wire 3 is supported by the quartz tube 2 at many points via the beads 11 as described above, and the tube of the quartz tube 2 is directly connected. No contact with walls. Therefore, the quartz tube heater 1 is not locally heated, and therefore the quartz tube is not locally heated to a high temperature.

FIG. 3 shows a second embodiment of the quartz tube heater 1 according to the present invention. The second embodiment, except for the following points,
The structure is almost the same as that of the first embodiment. In the second embodiment, instead of mounting the beads 11 on the nichrome wire 3, a sand granulated quartz particle 1 is placed in a quartz tube 2 in which the nichrome wire 3 is inserted.
2 is filled. The quartz granules 12 enter the gap between the inner peripheral wall reference surface of the quartz tube 2 and the coil-shaped nichrome wire 3 so that the nichrome wire 3 can be supported at many places.
It has an appropriate size. Further, in the case of this embodiment,
Since the quartz particles 12 have hygroscopicity, the quartz tube 2
Both ends of are sealed airtightly with the lead wire 10 being passed therethrough. In the quartz tube heater 1 configured as described above, unlike the first embodiment, the nichrome wire 3 does not necessarily exist at a portion where the nichrome wire 3 contacts the tube wall of the quartz tube 2. However, since the nichrome wire 3 in that portion is also in contact with a large number of quartz particles 12 in the vicinity thereof at the same time, the quartz tube 2 is not locally heated, and therefore, the quartz tube heater 1 is locally heated. It is possible to avoid extremely high temperatures.

Incidentally, the present invention is not limited to the above-mentioned embodiment,
Various modifications are possible within the scope of this invention. For example, the quartz beads and the quartz particles may be made of another suitable material having heat resistance.

[Advantage of the Invention] The quartz tube heater 1 according to the present invention configured as described above.
Then, the temperature is not locally high, and the risk of pinhole generation due to the local promotion of the erosion reaction is small. Therefore, the quartz tube heater according to the present invention has a longer life than the conventional quartz tube heater. Under the same usage conditions as the conventional one, the life of the quartz tube heater according to the present invention is about 6 months, which is dramatically longer than that of the conventional one.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of a quartz tube heater according to the present invention, which is partially shown in section.
The figure is a cross-sectional view taken along the line AA of FIG. 1, and FIG.
2 is a cross sectional view showing a second embodiment of the quartz tube heater corresponding to the figure, and FIG. 4 is a cross sectional view of the conventional quartz tube heater corresponding to FIG. 1 ... Quartz tube heater, 2 ... Quartz tube, 3 ... Nichrome wire, 10
… Lead wire, 11… beads.

Claims (1)

[Scope of utility model registration request] 1. A curved tube-shaped heater comprising a coil-shaped heating element and a curved tube which surrounds the heating element and insulates a liquid to be heated, wherein the heating element penetrates a plurality of beads. And a curved tube-shaped heater which is supported by the curved tube through the beads.