JPH04306835A - Damage detector of quartz heater - Google Patents

Abstract

PURPOSE:To detect pinhole generated in a quartz heater for heating chemical solution wherein a quartz tube is immersed. CONSTITUTION:In a quartz heater 1 comprising a quartz tube 2, wherein a heating wire is inserted, to be immersed in a chemical solution in a processing vessel for heating the chemical solution, a vapor leading-out channel 6 is extended on one end of the quartz tube 2 while a temperature sensor 7 is provided on this vapor leading-out channel 6 so that a pin hole generated in this quartz tube 2 can be substantially detected by detecting that the temperature exceeds the specific set value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure detection device for a quartz heater such as a so-called throw-in heater used for heating cleaning liquid in a cleaning tank.

0002

[Prior art and issues to be solved] Semiconductor wafers
In the process, the wafer that has undergone the ion implantation process is then carried into a diffusion furnace and subjected to a diffusion process. In order to carry out this diffusion process in an appropriate state without metal contamination, the wafer before the diffusion process is usually subjected to a cleaning process called pre-diffusion cleaning.

[0003] For such pre-diffusion cleaning, a processing tank made of quartz is used, and the cleaning liquid is a mixture of aqueous ammonia, hydrogen peroxide, and an appropriate amount of pure water. Further, in order to increase cleaning efficiency, the processing liquid in the processing tank is heated to, for example, about 80°C. The heater for this type of heating is immersed in a cleaning solution to avoid metal contamination on the surface of the wafer being cleaned.
A heater with a special structure called a so-called quartz heater is used. Note that the reason why the processing tank is also made of quartz as described above is to avoid metal contamination of the cleaning liquid.

As shown in FIG. 3, the quartz heater 1 has the following features:
It has a configuration in which a heating wire 3 is inserted into the inside of a quartz tube 2 which is bent into a predetermined shape. The quartz tube 3 extends vertically at a corner of the processing tank, and has a vertical part whose upper end protrudes sufficiently above the surface of the cleaning liquid, and a vertical part which is bent horizontally from the lower end of this vertical part along the bottom surface of the processing tank. and a horizontal intermediate portion extending from the top to the right. When a voltage is applied between both ends of the heating wire inserted through the quartz tube as described above, the heating wire is heated, and the cleaning liquid in the processing tank is heated to a predetermined temperature by this heat. A predetermined number of wafers W before the diffusion process are immersed in the heated cleaning liquid as described above while being supported on the wafer carrier C for a certain period of time, and are subjected to the cleaning action of the cleaning liquid.

By the way, as mentioned above, the quartz tube 2 used in the quartz heater is made of pure quartz that does not contain any metal (such as lead) in order to avoid metal contamination of the cleaning solution or the wafer surface. Because of this, it is relatively weak in strength and is susceptible to corrosion by chemicals such as ammonia at high temperatures. The quartz tube 2, which is configured as a tube through which a heating wire is inserted and which directly receives heat generated by the heating wire as described above, is therefore susceptible to corrosion due to ammonia contained in the cleaning solution, and in fact corrodes over time. is observed. If this is left unattended, pinholes will eventually form in the quartz tube, and some of the cleaning fluid that will seep into the quartz tube through these pinholes will cause the cleaning water to be contaminated by the metal that makes up the heating wire. Become. Therefore, conventionally, the quartz tube in the above-mentioned quartz heater is
The only method that has been adopted is to prevent metal contamination of the cleaning fluid by replacing it with a new one at regular intervals.

However, before the regular replacement of the quartz tube as described above, if a pinhole occurs in the quartz tube due to a sudden failure or a change in usage conditions such as the current that should be conducted to the heating wire, the pinhole should be removed. Since there was no automatic detection method in the past, it was possible that all wafers that were cleaned between the time a pinhole appeared and the period before regular replacement would become contaminated with metal. If such a situation occurs, there is a possibility that quality problems of the semiconductor chips to be manufactured will occur one after another during the final inspection process, and improvements have been desired.

The present invention was devised under the above-mentioned circumstances, and automatically detects the occurrence of pinholes in the quartz heater and prevents a large number of metal-contaminated wafers. The objective is to be able to take appropriate measures in the pre-diffusion cleaning process, such as replacing the quartz heater, before this occurs.

[0008]

[Means for Solving the Problems] In order to solve the above problems, the present invention takes the following technical measures. That is, the present invention provides a quartz heater that is made by passing a heating wire through a quartz tube and is immersed in a chemical solution in a processing tank to heat the chemical solution in the processing tank, in which a steam outlet path is provided at one end of the quartz tube. It is characterized in that a temperature sensor is provided in this vapor outlet path, and the presence of chemical liquid vapor in the quartz tube is determined by the rise in temperature detected by the temperature sensor.

[0009]

[Operations and Effects of the Invention] If a pinhole is generated in the quartz tube while the chemical solution in the processing tank is being heated by the quartz heater having the above configuration, and the chemical solution enters the quartz tube through this pinhole, the chemical solution will infiltrate into the quartz tube. The chemical solution is evaporated by the heat generated by the heating wire, and the quartz tube is filled with the vapor, which is then introduced into a steam outlet extending from one end of the quartz tube. Since this steam has a high temperature, the temperature sensor installed in the steam outlet path detects the rise in temperature inside the steam outlet path, and as a result, it is possible to know the presence of chemical vapor in the steam outlet path or quartz tube. can.

[0010] Therefore, the information detected by the temperature sensor on the temperature inside the steam outlet path is used as an input for activating an alarm device, and by activating the alarm device, the operator is alerted to the abnormal pinhole in the quartz heater. It is possible to notify the user that this has occurred, or it is also possible to automatically stop the cleaning process equipment using the temperature detection information from the temperature sensor.

According to the present invention, as described above, with a simple configuration, an abnormality of the quartz heater that heats the chemical solution in the processing tank by being immersed in the chemical solution in the processing tank for cleaning etc., that is, the corrosive effect of the chemical solution can be detected. The occurrence of pinholes in the quartz tube due to
It can be made to know automatically.

Therefore, for example, in a wafer process, when a silicon wafer is cleaned before diffusion using cleaning water containing aqueous ammonia, even if a pinhole occurs in the quartz glass before the periodic replacement of the quartz heater. , by automatically knowing the occurrence of this pinhole,
Immediate actions such as automatically stopping the cleaning equipment or replacing the quartz heater can prevent metal contamination on the wafer.
This makes it possible to eliminate large amounts of metal contamination on silicon wafers, which often leads to quality problems with semiconductor products.

Furthermore, by repeating the above-described cleaning process for semiconductor wafers using the quartz heater of the present invention, it is possible to clarify the periodic replacement cycle of the quartz heater itself. By setting the period when the quartz heater should be replaced regularly, the quartz heater can be replaced efficiently. This means that
This leads to an improvement in the operating rate of a series of equipment for the wafer process, and also leads to uniformity in the quality of semiconductor devices manufactured by such a wafer process.

[0014]

[Description of Embodiments] Hereinafter, embodiments of the present invention will be specifically described with reference to FIGS. 1 and 2. Figures 1 and 2
As shown in FIG. 3, the main body portion of the quartz heater 1 of the present invention is similar to the conventional example shown in FIG. That is,
a pair of vertical end portions 2a, 2b rising in the vertical direction;
A heating wire 3 made of nichrome wire or the like is inserted into the inside of the quartz tube 2, which has an intermediate portion 2c extending in a circular shape in a horizontal plane so as to connect the lower ends of these end portions 2a and 2b. It constitutes the main body part of the heater. As shown in FIG. 2, the upper end of one of the pair of end portions 2a and 2b is basically sealed with a cap member 4, and the upper end of one end 2a is inserted through a hole made in the cap member 4 in an airtight manner. A lead wire 5a electrically connected to the end of the heating wire 3 is led out to the outside.

On the other hand, the pair of ends 2a, 2 of the quartz tube 2
The other end 2b is not sealed like the one end, but instead is connected to a flexible steam outlet pipe 6 made of a corrosion-resistant tube such as a Teflon tube. One opening of a T-shaped joint 7 made of corrosion-resistant Teflon or the like is connected to the tip of the steam outlet pipe 6. Then, a lead wire 5b connected to the heating wire 3 extending inside the other end 2b of the quartz tube to which the steam derivation pipe 6 is connected passes through the inside of the steam derivation pipe 6 and into the T-shaped joint 7. It is led out from the opening and connected to a heater power source (not shown) together with the other lead wire 5a. Note that the opening of the T-shaped joint 7 through which the lead wire 5b is led out is not hermetically sealed, but communicates the steam outlet pipe 6 with the outside.

From the remaining opening of the T-shaped joint 7,
The tip detection portion of the temperature sensor 8 is inserted into the steam T-joint 7 or the steam outlet pipe 6. As such a temperature sensor 8, for example, a resistance temperature sensor such as a platinum temperature sensor, a thermistor, a thermocouple, or the like can be used. Steam outlet pipe 6 detected by temperature sensor 8
The temperature inside is monitored by a monitor device 9,
When the detected temperature exceeds a predetermined set temperature, an alarm output is sent. This alarm output can be used, for example, to activate alarm means such as audio or display, or
Alternatively, by inputting it into a control device for the cleaning device, it can be used as control information for automatic shutdown.

Quartz heater 1 of the present invention having the above configuration
As explained in the conventional example section, in pre-diffusion cleaning in the wafer process, it is used to heat a cleaning solution consisting of a mixture of aqueous ammonia, hydrogen peroxide, and pure water by immersing it in a cleaning tank. Used as a heater.

The cleaning liquid is heated to, for example, 80° C. by the quartz heater 1, and a plurality of silicon wafers carried by a wafer carrier carried by an automatic transfer mechanism (not shown) are immersed in the cleaning liquid for a predetermined time. . As such cleaning operations are repeated, the quartz tube 2 is constantly in contact with ammonia contained in the cleaning liquid while being heated by the heat generated by the heating wire 3 inside, so the quartz tube 2 suffers surface corrosion due to the ammonia and gradually becomes thicker. As the thickness decreases, pinholes eventually appear in the thinnest parts.

When such a pinhole occurs, a small amount of the cleaning liquid enters the inside of the quartz tube 2, and the cleaning liquid that has entered the inside of the quartz tube 2 is evaporated by the heat of the heating wire 3. The cleaning liquid vapor thus generated in the quartz tube 2 enters the steam outlet tube 6 through the end 2b of the quartz tube, and is exhausted to the outside through the opening of the T-shaped joint 7.

Under normal conditions, the lead wire 5b, which does not generate heat, is inserted through the steam outlet pipe 6, so the internal temperature of the steam outlet pipe 6 does not rise much. However, when the cleaning liquid vapor generated inside the quartz tube as described above flows out of the steam outlet tube 6, the internal temperature of the steam outlet tube 6 increases due to the steam temperature. Such a temperature rise is detected by the temperature sensor 8, and when the detected temperature exceeds a predetermined set temperature, the monitor device 9 issues an alarm output.

Therefore, according to the quartz heater 1 of the present invention, even if a pinhole occurs in the quartz tube 2 constituting it, the pinhole will not be generated in the quartz tube 2 due to the pinhole as described above. By detecting the steam temperature, the occurrence of pinholes in the quartz tube 2 can be practically detected. As a result, when a pinhole occurs in the quartz tube 2 of the quartz heater, it is possible to replace the quartz tube 2 or stop the cleaning device itself.
Contamination of the cleaning liquid by the metal constituting the heating wire 3 through the pinhole, metal contamination of the wafer during cleaning, contamination of the diffusion furnace that processes the metal-contaminated wafer, and various other processes in the wafer process. This makes it possible to prevent metal contamination from spreading throughout the equipment.

[0022] Thereby, it is possible to minimize quality troubles in semiconductor devices manufactured through the wafer process, and it is also possible to improve the operating rate of the semiconductor device manufacturing line. Further, it is possible to provide an empirical rule for clearly knowing the regular replacement cycle of the quartz tube 2.

Of course, the scope of the present invention is not limited to the above-described embodiments. In the embodiment, a tube such as a Teflon tube is extended and connected to the end of the quartz tube 2 as the steam outlet path 6, but such an extension connection tube is omitted and the T-type joint 7 shown in the embodiment is used. It is also within the scope of the present invention to connect the member directly to the end of the quartz tube 2.

Further, in the embodiment, the lead wire 5b connected to one end of the heating wire is passed through the entire length of the steam outlet path 6, but it is not necessary to do so. Alternatively, the lead wire 5b may be led out from the end without passing through the steam lead-out path 6.

Furthermore, since the present invention relates to a device for detecting damage to a quartz heater, it does not matter what kind of chemical liquid is heated in which case using such a quartz heater. Therefore, the present invention is not only applicable to a heater for heating a cleaning solution in pre-diffusion cleaning in a semiconductor wafer process, but also for heating a chemical solution in fields other than semiconductor wafer processes. It can be applied to all quartz heaters used in

[Brief explanation of the drawing]

FIG. 1 is an overall side view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing main parts of the embodiment of FIG. 1;

FIG. 3 is an explanatory diagram of a conventional example.

[Explanation of symbols]

1 Quartz heater 2 Quartz tube 3 Heating wire 6 Steam outlet path (pipe) 8 Temperature sensor

Claims (1)

[Claims] Claim 1: A quartz heater which is made by passing a heating wire through a quartz tube and is immersed in a chemical solution in a processing tank to heat the chemical solution in the processing tank, wherein a steam outlet path is extended to one end of the quartz tube. A device for detecting damage to a quartz heater, characterized in that a temperature sensor is provided in the vapor outlet path, and the presence of chemical vapor in the quartz tube is detected by detecting an increase in temperature detected by the temperature sensor. .