JP3731030B2 - Viewport with heater - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a viewport mounted on a semiconductor manufacturing apparatus, and more particularly to a viewport having a structure in which the viewport itself generates heat by a built-in heater.
[0002]
[Prior art]
In a plasma etching apparatus used for semiconductor manufacturing, a viewport is placed on a wall surface of a chamber in order to check and manage a processing process from the outside of the chamber. The viewport functions as a viewing window for visually confirming the inside of the chamber and an ultraviolet transmission window for detecting the end of the plasma etching process, but its function as an ultraviolet transmission window is particularly important. Termination detection is a technique that utilizes the fact that the plasma emission spectrum is determined by the composition of the object to be etched. By monitoring the plasma emission spectrum and detecting the change, the etching layer and its lower layer are detected. It is intended to determine the timing for stopping the etching by detecting the boundary. Specifically, ultraviolet rays that pass through the viewport and are emitted from the chamber are received by a measurement probe placed outside the viewport, analyzed by a spectroscope, and read for spectral changes. The etching state is controlled based on the information obtained from the above.
[0003]
Conventional viewports are made of a single quartz plate in consideration of transparency, strength, heat resistance, price, and the like.
[0004]
[Problems to be solved by the invention]
However, the conventional viewport satisfies the required performance in the short term, but has a drawback that the continuous use time is very short as described below.
[0005]
The reason why the continuous operation time of the apparatus is shortened will be described below. That is, reaction by-products generated during the etching process are deposited on the chamber wall surface and viewport surface having a low temperature. At this time, since reaction by-products deposited in the viewport generally absorb ultraviolet rays, the ultraviolet transmittance of the viewport is lowered, which hinders end detection. For this reason, it is necessary to stop the operation of the apparatus at regular intervals, and to replace and clean the viewport.
[0006]
In addition, although quartz is inexpensive, it has low resistance to plasma, particularly fluorine-based radicals. Therefore, the chamber inner surface side of the viewport exposed to radicals is eroded, and the surface is roughened in a short time. For this reason, the transmission of ultraviolet rays is hindered by irregular reflection, and as described above, replacement and cleaning are necessary. In order to solve this problem, some quartz plates are mechanically combined with sapphire. However, as in the case of quartz, deposition of reaction by-products is inevitable and the continuous operation of the apparatus is avoided. I couldn't.
[0007]
[Means for Solving the Problems]
The present invention has been devised in order to solve the above-described problems, and includes technical means described below.
[0008]
As shown in FIG. 1, the viewport of the present invention is composed of a substrate, a thin film heater layer, an adhesive, a protective cover, a feeding electrode , a quartz rod, and a terminal. First, a circuit pattern of a transparent conductive film is formed on a substrate as a thin film heater layer by vacuum deposition and etching. The substrate 1 may be any material that absorbs less in the wavelength range of ultraviolet and visible light, such as quartz and sapphire. However, since the atmospheric pressure is applied to the entire viewport, a thickness having a resistance equivalent to the area is required (7 ~ 15mm). For this reason, quartz is most suitable as the substrate material of the present invention in view of ultraviolet transmission performance and material cost. The side surfaces of the quartz rod are fixed by an adhesive, but there is no adhesive between the protective cover and they are only in close contact. This is to prevent ultraviolet rays from being absorbed by the adhesive.
[0009]
As the thin film heater layer formed on the substrate, a transparent conductive film such as tin oxide or ITO can be used, but a tin oxide transparent conductive film having excellent heat resistance is preferable. This thin film heater is formed on a substrate with a circuit pattern that is optimally designed for line width, total length, and film thickness in consideration of the heat capacity, heat radiation amount, holding temperature, etc. of the entire viewport.
[0010]
Further, the terminal portion for supplying electric power to the thin film heater is configured by a method as shown in FIG. 4 in order to prevent a disconnection accident during use.
That is, a through hole or a screw hole is provided in a portion where both ends of the power supply electrode to the thin film heater on the substrate are located, and a metal terminal such as brass, copper, or kovar is inserted or screwed therein. At this time, it is desirable to apply a silver paste or a conductive epoxy adhesive between the terminal, the substrate, and the thin film heater so that the mechanical and electrical connection is made stronger.
[0011]
Then, a sapphire thin plate for a protective cover is bonded to the thin film heater surface on the substrate with an adhesive. Adhesives such as epoxy, acrylic, or silicone can be used as the adhesive for bonding the protective cover, but epoxy optical adhesives are used in consideration of deterioration due to ultraviolet rays and heat resistance. It is preferable to do this. As the protective cover, sapphire, quartz or the like can be used, but it is preferable to use sapphire in order to protect against plasma attack inside the chamber. The protective cover made of sapphire preferably has a thickness of 0.5 mm to 1.5 mm in order to increase the heating efficiency of the conductive film heater and reduce the cost.
[0012]
[Example 1]
Hereinafter, embodiments according to the present invention will be described with reference to the accompanying drawings.
FIG. 2 is an exploded side sectional view of the viewport of the present embodiment. A 200 × 50 × 9 mm quartz plate was used as the substrate (1), and the 200 × 50 mm surface was mirror finished on both sides. On the board (1), there are two M3 taps (2) penetrating at two positions where the power supply electrode (5) and the terminal M3 bolt (7) are connected. Through-hole (3) was provided.
Then, a transparent conductive film of tin oxide was formed on one side of this substrate by vacuum deposition as a thin film heater layer (4).
[0013]
Further, as shown in FIG. 3, silver paste is applied to both ends of the thin film heater layer (4) to form a feeding electrode (5). Further, as shown in FIG. 4, the silver paste (6) is placed in the M3 tap hole (2). Then, M3 bolts (7) for terminals were screwed in. And this is baked at 180 ° C., and the thin film heater layer {circle over (4)}-feeding electrode {circle over (5)}-M3 bolt for terminal {7} is brought into electrical conduction, and finally the lead wire {12} over the M3 bolt {7} Was attached by soldering (11).
[0014]
As shown in FIG. 2, as the protective cover (8), a 200 × 50 × 1 mm sapphire plate was prepared, and this was used as an adhesive (9) with an optical epoxy adhesive (Epoxy Technology Co., Ltd .: 301-2). It was bonded to a quartz substrate (1). Then, a quartz rod (10) having a diameter of 10 mm and a length of 9 mm was inserted into a hole having a diameter of 10 mm on the side of the substrate (1) and bonded. At the time of bonding, only the inner surface of the hole of the substrate (1) and the side surface of the quartz rod (10) were bonded so that the adhesive did not adhere to the surface of the protective cover (8) located at the bottom of the hole. This is to improve the ultraviolet transmittance of the portion where the measurement probe is arranged as much as possible. That is, the wavelength used for termination detection in this example is about 250 nm, but as can be seen from the ultraviolet transmission characteristics of the tin oxide film shown in FIG. 5 and the ultraviolet transmission characteristics of the epoxy adhesive shown in FIG. This is because both the film and the epoxy adhesive become an obstacle to ultraviolet light transmission.
[0015]
The viewport thus manufactured and the quartz single-plate viewport were set in an actual apparatus of an etching apparatus, and a comparative test of continuous operation time was performed. The viewport of the present invention supplied power of 100 V × 15 W to the circuit pattern, and maintained the temperature of the viewport surface at 110 ° C. After 50 hours, the quartz single plate viewport was unable to operate due to the deposition of reaction byproducts. When the viewport of the present invention was used, the apparatus could be continuously operated for 1,500 hours. When the viewport after use was removed and confirmed, some accumulation of reaction by-products was observed, but the roughness of the inner surface due to radical attack was negligible.
[0016]
【The invention's effect】
According to the present invention, an excellent viewport can be provided as follows. That is, by providing a heat generation layer in the viewport body and generating heat in the viewport itself, the deposition rate of reaction byproducts could be significantly reduced. Moreover, by providing a protective cover made of sapphire on the surface of the viewport that comes into contact with radicals, it was possible to prevent radical attacks. As a result, the continuous operation time of the equipment can be greatly extended. Furthermore, the quartz rod and the protective cover were brought into close contact without using an adhesive, and the quartz rod was fixed only to the quartz substrate with the adhesive, so that ultraviolet rays could be guided without being attenuated.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a viewport in the present invention.
FIG. 2 is an enlarged view of a side section of a viewport in the present invention.
FIG. 3 is an external view of a thin film heater layer and a feeding electrode in the present invention.
FIG. 4 is a configuration diagram showing a method of joining a feeding electrode and a terminal in the present invention.
FIG. 5 is an ultraviolet transmission characteristic diagram of a tin oxide film according to the present invention.
FIG. 6 is an ultraviolet transmission characteristic diagram of the epoxy adhesive in the present invention.
[Explanation of symbols]
(1) Substrate, (2) M3 tap, (3) Through hole, (4) Thin film heater layer, (5) Feed electrode, (6) Silver paste, (7) M3 bolt for terminal, (8) Protective cover, (9) Adhesive, (10) Quartz rod, (11) Conductive paste, (12) Lead wire

Claims (3)

In a viewport in which a heater circuit made of a transparent conductive film is formed on one side of a quartz substrate, and a protective cover plate is pasted onto the quartz substrate with an adhesive, a path for guiding visible light and ultraviolet rays is formed with a quartz rod. viewport the quartz substrate and fixed with an adhesive, the protective cover plate and formed in the quartz path, characterized in that the is adhered without using an adhesive. The viewport according to claim 1, wherein the adhesive is an optical epoxy adhesive . The viewport according to claim 1, wherein the protective cover plate is made of sapphire having a thickness of 0.5 mm to 1.5 mm .

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