JP2005064359A - Film heater with accretion detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable electrically detecting deposits deposited on the surface of a film heater 1; to enable grasping the thickness of the deposits whenever necessary; and to exactly obtain maintenance information such as the necessity of prevention of the increase of the deposits or elimination of the deposits. <P>SOLUTION: The film heater 1 comprises the film shape of a heater element 3 consisting of a patterned conductor film that is laminated by insulating films 2, 7 with heat resistance and has flexibility. The heater includes electrostatic capacity electrodes 4a, 4b acquiring capacitance facing the surface direction of the film or the thickness direction thereof, and detects the deposits adhered to the surface of the film by the capacity acquired by the electrostatic capacity electrodes 4a, 4b. For example, the electrostatic capacity electrodes 4a, 4b are formed together with the heater element 3, and are laminated by the insulating films 2, 7. In this case, the electrostatic capacity electrodes 4a, 4b face the surface direction of the film heater 1 to acquire the capacity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the present invention, a capacitive electrode is included in a film heater attached to the inner surface of an exhaust gas pipe of a semiconductor film forming apparatus or the like, and deposits adhering to the surface of the film heater are acquired between the capacitive electrodes. The present invention relates to a film heater with an adhering matter detector having a function of detecting by a capacitance change.

  A CVD (Chemical Vapor Deposition) is often used for a semiconductor film forming apparatus. This is a technique in which a volatile metal halide, a metal organic compound, or the like is deposited on a wafer substrate by a gas phase chemical reaction. It is used to make thin films of nitrides, oxides, carbides, silicides, borides, refractory metals, metals, semiconductors and the like.

This CVD will be described in more detail. The inside of a chamber in which a substrate such as a Si wafer is installed is generally a reduced pressure atmosphere, and a carrier gas such as H ₂ , Ar, N ₂ , CO _2, etc. A source gas that is a film forming material such as a volatile halide is introduced, sprayed onto a substrate such as a Si wafer at a predetermined reaction temperature, and the source gas is reacted in a gas phase to form a nitride film or the like. Deposit and form a film.

  In this CVD apparatus, ammonium chloride is generated as a by-product, for example, a by-product in the case of forming a nitride film by the reaction of the source gas, and this is discharged from the chamber through the exhaust gas pipe. The relationship between the ammonium chloride temperature and the vapor pressure is shown in FIG. Since film formation in a CVD apparatus is often performed at several Torr, as can be seen from FIG. 8, when the temperature of the exhaust gas pipe falls below about 150 ° C., ammonium chloride solidifies on the inner wall surface of the exhaust gas pipe. ,accumulate. As a result, in the worst case, the exhaust gas piping is blocked.

  In order to prevent this, the CVD exhaust gas pipe attached to the CVD film forming apparatus is equipped with a heater installed in contact with the outer wall of the pipe, and preheats the inside of the pipe to about 150 ° C. with a margin, so that ammonium chloride, etc. Prevents the accumulation of. However, the exhaust gas piping is divided in consideration of maintenance, and the connection portion has a clamp structure. However, heat radiation is large at this clamp portion, and the temperature tends to be locally low. In some cases, the preheating heater of the exhaust gas pipe is cut and the temperature is lowered. In such a case, the exhaust gas pipe has a considerable allowance for the cross-sectional area of the flow path with respect to the flow rate of the exhaust gas discharged so that the exhaust gas pipe is not immediately clogged. The exhaust gas pipe with a large diameter of about 4B is used. If the exhaust gas pipe has a sufficient thickness, it is possible to replace the preheater or clean the pipe outside the operating hours.

  The preheater is wound around the exhaust gas pipe to prevent deposits from adhering to the chamber side where the substrate is installed. This is also because the by-product particles are back-flow and back-diffused to prevent contamination of the substrate surface such as Si wafer.

  As a structure of the preheating heater, generally, maintenance of the heater is considered, and a structure in which the heater is wound around the outer periphery of the pipe for preheating the exhaust gas pipe is general. However, warming the inner surface of the pipe from the outside of the pipe is inefficient due to the heat flow. From the original purpose of preheating the exhaust gas, it is only necessary to warm the exhaust gas. By doing so, it is desirable in that the waste of heating the exhaust gas pipe having a large heat capacity can be saved and the time from the start of preheating to the operation of the film forming apparatus can be shortened. For that purpose, a thin, light and small heat capacity film-like heater in close contact with the inside of the pipe is the most desirable heater.

  As a flexible film heater, for example, as described in Patent Document 1 (Japanese Patent Laid-Open No. 11-297458) below, a flexible heating element and a flexible electrical insulating layer covering the heating element are provided. A high-temperature heater that is flexible and has excellent heat resistance is known.

  However, even if such a film heater is in close contact with the inside of the pipe, there are clamp structures for maintaining the pipe and a port for attaching a pressure gauge, etc., resulting in a local temperature drop in the pipe, and a by-product It is inevitable that things accumulate. For example, because the film deposition system itself changes in temperature due to changes in pressure, temperature, flow rate, etc. during wafer insertion and removal and CVD processes, even preheated piping is affected by temperature fluctuations on the chamber side. The temperature dropped, and byproducts gradually accumulated on the inner surface of the pipe.

Until now, the state of clogging of piping due to by-products is compared with the results when there is no clogging, whether or not the time ratio of pressure drop at the time of pressure reduction in the film formation apparatus (chamber) has deteriorated, I guessed and judged. Alternatively, the relationship between the number of times the film forming process is performed and the deposition thickness or the degree of contamination on the wafer substrate is examined, the limit number and limit value are determined in advance, and clogging occurs when the limit number is exceeded. I was judging.
Japanese Patent Laid-Open No. 11-297458

  The present invention makes it possible to electrically detect deposits deposited on the surface of the film heater in the heating means inside the pipe using the film heater, and thereby to measure the thickness of the deposit on the surface of the film heater as needed. The purpose is to make it possible to grasp, and to appropriately and accurately obtain maintenance information such as the necessity of preventing the increase of the deposit or the necessity of removing the deposit.

  That is, in the present invention, in order to achieve the above object, in using the film heater 1 that can be directly bonded to the inner wall surface of the exhaust gas pipe or the like of the CVD apparatus or can self-adhere, Capacitance electrodes 4a and 4b that are opposed to each other and that can acquire capacitance are included, and deposits adhering to the surface of the film heater 1 and the thickness thereof are detected by capacitance change. For example, by-products accumulated on the surface of the film heater 1 stretched on the inner wall surface of the exhaust gas pipe can be detected, and the necessity of the maintenance time of the pipe for preventing the increase in the deposition thickness and removing the deposit can be grasped. Like that.

The film heater 1 according to the first aspect of the present invention used for such a purpose has a film shape in which a heater element 3 composed of a patterned conductor film is laminated with insulating films 2 and 7 having heat resistance. And having capacitance electrodes 4a and 4b that acquire capacitance by facing the surface direction or the thickness direction of the film, and deposits adhered to the surface of the film. This is detected by a change in capacitance acquired by the capacitance electrodes 4a and 4b.
The invention according to claim 2 of the present application is the film heater 1 of the invention according to claim 1, wherein the capacitance electrodes 4 a and 4 b are formed together with the heater element 3 and laminated with the insulating films 2 and 7. It is what.

  Furthermore, the invention according to claim 3 of the present application is the film heater 1 according to claim 1, wherein one capacitance electrode is formed on one surface of the insulating films 2 and 7, and the insulating film 2 , 7 and the heater element 3 laminated with the conductor film 8 as an earth electrode for acquiring electrostatic capacity.

  The invention according to claims 1 to 3 of the present application includes capacitance electrodes 4 a and 4 b that acquire capacitance in the surface direction or thickness direction of the film heater 1, and are attached to the surface of the film heater 1. Since an object is detected by a change in capacitance acquired by the capacitance electrodes 4a and 4b, whether or not deposits are attached to the surface of the film heater 1 can be detected and grasped at any time. That is, since the dielectric constant of the insulating films 2 and 7 and the space in the pipe on the surface thereof and the dielectric constant of the volume are usually different, the electrostatic capacitance is applied when no deposit is attached to the surface of the film heater 1 and when it is attached. The capacitance acquired by the capacitive electrodes 4a and 4b changes. Due to this change in electrostatic capacity, it is possible to electrically detect adhesion of deposits on the surface of the film heater 1 as needed, and to contribute to appropriate measures such as countermeasures against an increase in the deposition thickness or maintenance timing.

  In the invention according to claim 2 of the present application, since the capacitance electrodes 4a and 4b are opposed to the surface direction of the film heater 1, the capacitance can be acquired by the capacitance electrodes 4a and 4b. I can do it. Therefore, the capacitance change is caused by the by-product deposited on the surface of the film heater 1, and the deposition of the by-product can be reliably detected.

  Furthermore, in the invention according to claim 3 of the present application, the electrostatic capacity can be acquired by the conductor film 8 and the heater element 3 facing each other in the thickness direction of the film heater 1. Therefore, by attaching the film heater 1 in the pipe with the conductor film 8 side facing the inner wall surface of the pipe, and using the conductor film 8 with grounding, the capacitance in the central axis direction of the pipe is focused. It becomes possible to measure.

  In the film heater 1 that can be attached to the inner wall surface of the exhaust gas pipe of the CVD apparatus as described above, if the deposit attached to the surface can be detected and the thickness thereof can also be grasped, the maintenance time of the pipe is determined. I can do it. In particular, if the maintenance time can be estimated, the maintenance is ready and the maintenance becomes very easy. For that purpose, it is possible to detect that the deposit has adhered to the surface of the film heater, and to measure the thickness of the film heater attached to the inner wall surface of the exhaust gas pipe. Detection means is desirable.

  The preheating temperature of the exhaust gas pipe is about 80 ° C. to 300 ° C. depending on the type and pressure of the film forming material and needs to withstand this temperature. Examples of a flexible insulating material that can withstand this temperature include fluorine resin, polyimide resin, and silicon. Of these, fluororesins are hardly suitable for use as an insulating material for film heaters because they have almost no adhesive and are not heat-fusible. Silicone resin is weak in strength and has the disadvantage of tearing from small scratches, so it is still unsuitable for use as an insulating material for film heaters. For this reason, polyimide resin is optimal as an insulating material for the film heater.

By-products generated in the above-described CVD apparatus are often in the form of salt or oxide, and have a higher dielectric constant than polyimide resin. Therefore, if a metal film is laminated in the polyimide film and incorporated in the film heater as a by-product, when the by-product is deposited on the film heater, the accumulation of the by-product is detected from the difference in capacitance with the polyimide resin, And the thickness can be measured as an average value.
The present invention has been made from such a viewpoint. Hereinafter, examples of the present invention will be described in detail with specific examples with reference to the drawings.

FIG. 1A shows a film heater 1. FIG. 1B is an enlarged cross-sectional view taken along line AA in FIG.
That is, the heater element 3 made of a conductor film having a thickness of about 50 μm is formed on the insulating film 2 made of a heat-resistant resin such as polyimide resin and having a thickness of about 50 μm. In the illustrated example, the insulating film 2 is basically a quadrangle, and projecting pieces that become the terminal portions 11a and 11b protrude from one short side thereof. The heater element 3 is patterned so as to form a continuous strip of conductor on the insulating film 2, and terminal conductor portions 5 a and 5 b at both ends thereof are led out to the terminal portions 11 a and 11 b of the insulating film 2. Yes.

  On the insulating film 2, a pair of electrostatic capacitance electrodes 4a and 4b made of a patterned conductor film are also provided adjacent to each other, and terminal portions 6a and 6b which are end portions of these lead conductors The heater element 3 is led to the terminal portion 11 a of the insulating film 3 adjacent to the terminal conductor portions 5 a at both ends of the heater element 3.

Further, an insulation having a thickness of about 25 μm made of a heat-resistant resin such as polyimide resin is applied over the entire surface of the insulating film 2 so as to cover these heater elements 3, the capacitance electrodes 4a and 4b, and the lead portions thereof. A film 7 is formed.
Needless to say, the arrangement of the heater element 3 on the insulating film 2 and its terminal conductor portions 5a and 5b, and the capacitance electrodes 4a and 4b and the terminal portions 6a and 6b can be changed as needed. .

FIG. 2 shows an example of a structure in which the film heater 1 is attached in a pipe 12 such as an exhaust gas pipe. In this way, the film heater 1 is bent into a cylindrical shape and attached along the inner wall of the exhaust gas pipe 12.
As a means for fixing the film heater 1 to the pipe 12, means for attaching the film heater 1 to the inner wall of the pipe 12 with polyimide varnish or the like, for example, a film heater on a spring material such as SUS304, SUS630, SUS631 1 is formed to give elasticity to the film heater 1, and there is means for pressing and sticking to the inner wall surface of the pipe 12 due to its spring property.

  Adjacent pipes 12 are joined to each other by flanges 15 and 15 and sealed with gaskets 14 such as double O-rings, and the flanges 15 and 15 are fastened and fixed by clamp fittings 13 and 13. In the example of FIG. 2, a plurality of clamp fittings 13, 13... Are used and connected by a link arm 16, and one clamp fitting 13 ′ is fastened by a bolt 17 and the whole is fastened and fixed. When disassembling during maintenance, the bolts 17 are loosened, removed and disassembled. The terminal portions 11a and 11b of the film heater 1 are drawn out between the gaskets 14 provided between the flanges 15 and 15 and from the slits of the outer ring 18 outside thereof, and are connected to a power source and a measuring instrument.

FIG. 3 shows another example of the electrode structure of the film heater 1 of the present invention having a capacitance electrode. It is a principal part expanded sectional view of the part corresponding to the part shown in FIG.1 (b).
In FIG. 3A, one electrostatic capacitance electrode 4a is provided on the side of the insulating film 2 on which the conductive film 3 is provided, and a conductive film 8 is provided on the surface of the insulating film 2 as a ground electrode for shielding. This is an example of the other capacitance electrode. The electrostatic capacitance electrode 4a and the conductor film 8 are opposed to each other in the thickness direction of the film heater 1 with the insulating film 2 interposed therebetween, and the electrostatic capacity is the heater element 3 or one new electrode 4a and the conductor film 8 Measure between.
FIG. 3B shows an example in which the heater element 3 is used as one capacitance electrode without providing the capacitance electrode 4a in FIG. In this case, the capacitance is measured between the heater element 3 and the conductor film 8.

  FIG. 4 shows a partial cross section in a state where the above-described film heater 1 is attached in the pipe 12. FIG. 4A is an example in which a film heater having the electrode structure as shown in FIG. 1 is attached to the pipe 12, and FIG. 4B has an electrode structure as shown in FIG. 3B. This is an example in which a film heater is attached to a pipe 12.

  FIG. 5 is a diagram showing specific dimensions of an electrode structure in which a pair of capacitance acquisition electrodes 4a and 4b are provided side by side on the insulating film 2 as shown in FIG. As shown in FIG. 5, the thickness of the capacitance acquisition electrodes 4a and 4b made of SUS was 0.05 mm, the width thereof was 4 mm, and the total thickness of the insulating layers 2 and 7 was 0.2 mm. The dielectric constant of the polyimide resin forming the insulating layers 2 and 7 is 3.0, the dielectric constant of the deposited ammonium chloride layer 18 is 10.9, and the dielectric constant of the exhaust gas layer thereon is 1.0. .

  Under these conditions, when the intervals p between the capacitance acquisition electrodes 4a and 4b are p = 1 mm, p = 2 mm, and p = 4 mm, respectively, the deposition thickness of ammonium chloride deposited on the insulating film 7 of the film heater 1 is The capacitance between the capacitance acquisition electrodes 4a and 4b changes as shown in FIG. As is clear from FIG. 6, the change in the unit thickness of ammonium chloride in mm units has a change in capacitance between the capacitance acquisition electrodes 4a and 4b of several tens of PF, which is a change in capacitance that can be measured sufficiently.

There are the following four means for measuring the change in capacitance.
1. Amplitude modulation method: A circuit of LC resonance with a high frequency oscillator is made, and the voltage generated in the capacitance to be measured is observed with an amplifier.
2. Frequency modulation method: The oscillation frequency is measured by inserting the capacitance to be measured into the LC or LR oscillation circuit.
3. Phase modulation method: Capacitance to be measured is put in a bridge circuit to detect a voltage change accompanying phase conversion.
4. Charge / discharge decay method: Receives the capacitance and measures the capacitance with the decay time. It is averaged repeatedly in a short time to reduce the influence of noise.

  Of these, the three phase modulation methods are suitable for detecting subtle changes in capacitance, which is the simplest. An example of this measurement circuit is shown in FIG. The disadvantage of this method is that it is easily affected by fluctuations in power supply voltage, ambient temperature, and stray capacitance, but many stable power supplies have been marketed in recent years, and the temperature before and after the operation of the deposition system is stable. If the measurement is performed in such a state, a relatively inexpensive circuit is sufficient. In particular, since the temperature and humidity of the clean room are controlled, the temperature change of the measurement circuit is very small, and even a simple circuit design can be used.

They are the perspective view (a) partly notched which shows the structure of the film heater by this invention, and its AA line expanded sectional view (b). An example of a structure in which the film heater shown in FIG. 1 is attached in the pipe is shown, FIG. 2 (a) is a longitudinal side view thereof, and FIG. 2 (b) is a longitudinal front view thereof. It is principal part sectional drawing which shows the other example of the electrode structure of the film heater of this invention which has an electrostatic capacitance electrode. It is a partial cross section which shows the example of the state which attached the above-mentioned film heater in piping. It is an expanded sectional view which shows the specific dimension of the electrode structure which provided in parallel on the insulating film as shown in FIG. 1, and provided a pair of electrostatic capacitance acquisition electrode. Under the conditions shown in FIG. 5, when the gap p between the capacitance acquisition electrodes is p = 1 mm, p = 2 mm, and p = 4 mm, respectively, the deposition thickness of the ammonium chloride deposited on the insulating film of the film heater and the electrostatic It is a graph which shows the example of the change of the electrostatic capacitance between capacity | capacitance acquisition electrodes. It is a circuit diagram which shows the example of the measurement circuit of the electrostatic capacitance between the electrostatic capacitance acquisition electrodes of a film heater using a phase modulation method. It is a graph (vapor pressure diagram or sublimation curve) showing the relationship between the temperature of ammonium chloride and the vapor pressure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Film heater 2 Insulating film 3 Heater element 4a Capacitance electrode 4b Capacitance electrode 7 Insulating film 8 Conductor film as a ground electrode

Claims (3)

A heater element (3) made of a patterned conductor film is laminated with a heat-resistant insulating film (2), (7), has a film shape, and is a flexible film heater, Capacitance electrodes (4a) and (4b) that acquire capacitance by facing the surface direction or thickness direction of the film, and deposits adhering to the surface of the film are deposited on the capacitance electrodes (4a) and (4b). A film heater with an adhering matter detector, which is detected by a change in electrostatic capacity obtained in (1). Capacitance electrodes (4a), (4b) are laminated with an insulating film (2), (7) together with a heater element (3), The film with a deposit detector according to claim 1, heater. One capacitance electrode is formed on one surface of the insulating films (2) and (7), and electrostatically is formed between the heater element (3) laminated with the insulating films (2) and (7). The film heater with a deposit detector according to claim 1, comprising a conductor film (8) as an earth electrode for acquiring a capacity.

Images