JP2003273062A - Etching rate control monitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an etching rate control monitor which controls the progress of etching of Si and SiO2 in a chemical, such as hydrofluoric acid or ammonium fluoride in which Si and SiO2 are dissolved, by a measurement method which is independent of the component concentrations in the chemical. <P>SOLUTION: There are provided an electrode which always contacts to an AT cut quartz oscillator by utilizing the relation between the frequency and the thickness of the AT cut quartz oscillator, an etching rate control monitor which comprises a movable electrode that repeats touching/detouching from the surface of AT cut quartz oscillator in the pressure of a liquid caused by reciprocation of a monitor body, a mechanism which automatically reciprocates it, and an instrument that measures the frequency. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching rate control monitor for measuring the etching rate in a chemical solution that corrodes Si and SiO2 using an AT-cut quartz crystal diaphragm.

[0002]

2. Description of the Related Art Conventionally, various methods have been used to control the etching rate of Si and SiO2 in a chemical solution such as hydrofluoric acid or ammonium fluoride. Broadly classified are (1) a method of managing from the relationship between the concentration measurement of the chemical solution and the characteristic value of the article to be treated with the chemical solution, and (2) a method of managing the change in the characteristic value of the article to be treated with the chemical solution over time. .

The method (1) generally uses ultrasonic waves, laser, or neutralization titration method to detect the component concentration in the chemical solution, and etches the actual product at the measured component concentration, and changes in the characteristic value and etching. From time, a method of calculating the etching rate at the measured component concentration,
The method (2) is a method in which the concentration of the chemical solution is not measured, the actual product is etched, the change in the characteristic value of the product before and after etching is measured, and the etching rate is calculated from the amount of change in the characteristic value and the etching time. is there.

In any of the methods, the etching rate is controlled by changing the characteristic value of the product actually etched and the etching time, and by feeding back the etching rate obtained there, stable etching is achieved. I was trying to achieve the rate.

[0005]

However, the method for measuring the concentration of the chemical solution generally requires that the chemical concentration meter can measure only one or two kinds of components. Measurement errors due to adult organisms were likely to occur. Also, in the method of measuring the concentration and adjusting it to the specified concentration, it is difficult to completely match the component loss ratio due to the etching process with the component ratio of the chemical solution added to compensate for it, and the above measurement error. The current situation is that the correct drug solution is not always prepared due to the effect of erroneous concentration adjustment.

Further, the component concentrations before and after the etching process greatly change depending on the amounts of Si and SiO2 dissolved by the etching process, and also due to the influence of the working environment such as temperature, humidity, and the exhaust gas amount in the etching processing apparatus. However, the current situation is that the concentration of the components of the chemical solution changes from moment to moment. Further, in order to increase the etching rate, a method of heating a chemical solution is generally used, but in such a case, the influence of the working environment on the change in the component concentration becomes large, and for example, the loss of the component due to the evaporation of the chemical solution itself. However, it was difficult to manage factors such as evaporation loss of the amount of chemical liquid.

As a result, the etching solution component concentration before the etching work is measured, adjusted to a prescribed concentration, and the etching time is set by using the etching rate obtained from the conventional experience and results, and the etching treatment is performed. However, the characteristic value of the product after the etching work may be different from the desired value.

Further, in the method which does not measure the concentration of the chemical solution,
Even if the etching rate is fed back, the component ratio of the chemical solution is significantly different from the work contents up to that point, so when compared with the method of measuring the concentration, the desired characteristic value often differs greatly. . An object of the present invention is to provide an etching rate management monitor capable of sequentially confirming the progress of etching in order to solve the above-mentioned current problems.

[0009]

It is a widely known fact that there is a proportional relationship between the thickness of an AT-cut quartz crystal diaphragm and the frequency. The etching rate control monitor according to the present invention uses an AT-cut quartz crystal diaphragm as a monitor for measuring an etching rate, accommodates this, and attaches an electrode capable of measuring a frequency.

Further, the etching rate management monitor according to the present invention has, in its electrode structure, a fixed electrode which is always in contact with the etching rate management monitor and a pair of electrodes which are movable electrodes which can be contacted and non-contacted. Shall consist of

Further, in the etching rate control monitor according to the present invention, the shape of the movable electrode changes due to the pressure generated by rocking the etching rate in the chemical solution, and the contact with the monitor AT-cut quartz crystal diaphragm. Non-contact switching shall be performed. By measuring the frequency of the AT-cut quartz crystal diaphragm for monitoring when the movable electrode is in contact, the etching rate is managed from the change in frequency.

Furthermore, the etching rate management monitor according to the present invention is a measurement device such as an oscillator or a network analyzer capable of measuring the frequency of the AT-cut quartz crystal diaphragm for monitoring by attaching a reciprocating linear motion mechanism to the etching rate management monitor body. It is also possible to automatically measure the frequency of the AT-cut quartz diaphragm for monitoring by synchronizing with the instrument.

[0013]

1 is a schematic side view of an etching rate control monitor used in the present invention. The AT-cut crystal plate for monitoring contained in the etching rate control monitor has a round or rectangular outer shape, and the gold film 1 is formed on one surface by a film forming method such as vapor deposition or sputtering. There is. The other surface 2 is composed of a crystal plane of SiO2. FIG. 2 is a side view and a front view showing the structure of the first embodiment of the present invention. The main body back plate 7 and the main body front plate 8 are formed of, for example, vinyl chloride that is not corroded by hydrofluoric acid, ammonium fluoride or the like. The main body back plate 7 has a groove 10 for accommodating the AT-cut quartz crystal vibrating plate 5 for monitoring shown in FIG. 1 in a portion near one end face 13, and a groove for accommodating the fixed electrode 6 in the center thereof. 1
1 is formed. A frequency measurement cable path 3 is formed from the center of the groove 11 so that the inside of the back plate of the main body faces the other end surface 14. The main body front plate 8 can accommodate the movable electrode 9 at a position facing the groove 11 formed in the main body back plate 7, and has a sufficient depth so as not to hinder the flow of chemicals such as hydrofluoric acid and ammonium fluoride. A groove 12 is formed. Further, from the groove 12 as well as the main body back plate 7, the frequency measurement cable path 4 is formed.

FIG. 4 is a sectional view taken along the line AA in FIG.
The movable electrode 9 is processed into a dogleg shape, and when the flow of the chemical liquid is in the direction (a), the movable electrode 9 comes into contact with the surface of the AT-cut quartz crystal diaphragm 5 for monitoring in the shape 17 due to the pressure of the flow. When the flow of the chemical liquid is in the direction (b), the movable electrode 9
Has a structure separated from the surface of the AT-cut quartz crystal diaphragm 5 for monitor.

FIG. 5 is a front view of an etching rate management monitor showing a second embodiment of the present invention. The structure is almost the same as that of FIGS. 2 and 3, but when the etching rate control monitor is moved back and forth in the direction (a) and the direction (b), the surface 13 is formed so as not to restrict the flow of the chemical solution.
A window 17 is opened on the surface, and a window 18 is also opened on the surfaces 15 and 16. The movable electrode 9 is attached in a state of being rotated 90 degrees counterclockwise with respect to the position shown in FIG.

FIG. 6 is a perspective view showing a third embodiment of the present invention. The etching rate control monitor 25 shown in FIGS. 1, 2, 3 and 4 is connected to a mechanism 20 capable of reciprocating linear movement in the horizontal direction. Furthermore, this mechanism 20 is attached to a chemical bath 24 for performing an etching process. Also,
A frequency measuring cable 21 is provided from the etching rate management monitor 25, and a measuring device 22 capable of frequency measurement is provided.
(Eg oscillator or network analyzer). At this time, it is necessary to shorten the length of the frequency measurement cable as much as possible in order to reduce the influence on the measurement of the stray capacitance caused by the wiring of the electric wire. If you want to extend the length of this, outside the chemical tank that is not affected by erosion by hydrofluoric acid or ammonium fluoride,
For example, it is desirable to use a corrected electrical path such as a coaxial cable.

FIG. 7 is a perspective view showing a fourth embodiment of the present invention. The etching rate management monitor 26 has the structure shown in FIG. 5, and is connected to the reciprocating linear motion mechanism 20 to operate in the vertical direction. Further, as in the second embodiment shown in FIG. 5, the measuring device 22 and the chemical solution tank 24 are attached to each other.

In the third and fourth embodiments, by connecting the reciprocating / simulating mechanism 20 and the measuring instrument 22 via, for example, a sequencer, the moving direction of the etching rate management monitor main body is such that the movable electrode is a monitoring AT. When operating in the direction of contact with the cut crystal diaphragm, AT for monitor
When the frequency of the cut quartz crystal diaphragm is measured and the etching rate management monitor is operated in the direction in which the movable electrode is not in contact, it is possible to perform control such that etching is not performed but etching is performed.

Therefore, the AT-cut crystal diaphragm for monitoring of the above-mentioned mechanism is put into a chemical solution tank such as hydrofluoric acid and ammonium fluoride used in the actual working process, and the frequency is measured to change every moment. Regardless of the composition of the chemical solution going on, the change in frequency of the AT-cut quartz diaphragm for monitoring stored in the etching rate control monitor and the change in the characteristic value of the product to be actually etched are investigated in advance and the proportional relationship is established. By obtaining the above, it is possible to know the etching progress state of the product processed by the actual chemical solution.

Further, by connecting the above measuring device to a computer and recording the measurement time and frequency sequentially, it is possible to know the change in frequency over time, and to measure the concentration of the chemical solution as described in the section of the prior art. By combining with, more stable etching work becomes possible.

[0021]

As is apparent from the above description, the etching rate control monitor according to the present invention is an alternative to the etching rate in a chemical solution such as hydrofluoric acid and ammonium fluoride, which utilizes the frequency change of the AT-cut quartz diaphragm for monitoring. The characteristics can be obtained, and the control of the etching process in actual mass production can be accurately obtained.

[Brief description of drawings]

FIG. 1 is a side view of an etching rate management monitor of the present invention.

FIG. 2 is a side view of an etching rate management monitor according to the first embodiment of the present invention.

FIG. 3 is a front view of an etching rate management monitor according to the first embodiment of the present invention.

FIG. 4 is a sectional view taken along the line AA in FIG. 3 of the etching rate management monitor according to the first embodiment of the present invention.

FIG. 5 is a front view of an etching rate management monitor according to a second embodiment of the present invention.

FIG. 6 is a perspective view showing the structure and operation of the third embodiment of the present invention.

FIG. 7 is a perspective view showing the structure and operation of the fourth embodiment of the present invention.

[Explanation of symbols]

1 Gold film surface 2 SiO2 surface 3 Path for frequency measurement cable 4 Path for frequency measurement cable 5 Monitor AT-cut quartz diaphragm 6 Fixed electrode 7 Etching rate management monitor back plate 8 Etching rate management monitor front plate 9 Moving electrode 10 Monitor AT cut quartz diaphragm storage groove 11 fixed electrode storage groove 12 movable electrode storage and chemical liquid flow path groove 13 etching rate control monitor end face A 14 etching rate control monitor end face B 15 etching rate control monitor side face A 16 etching Rate management monitor side surface B 17 Movable electrode contacting the AT-cut quartz crystal diaphragm for monitoring due to chemical liquid inflow resistance 18 Etching rate management monitor side window 19 Etching rate management monitor end face window 20 Reciprocating linear motion mechanism 21 Frequency measurement cable 22 Measuring instrument 23 Moni AT-cut quartz crystal diaphragm 24 for chemicals 25 Chemical solution tank 25 Etching rate management monitor 26 according to the first embodiment of FIGS. 2 and 3 Etching rate management monitor according to the second embodiment of FIG. ) The direction in which the chemical solution flows

Claims (4)

[Claims] 1. A monitoring AT in a chemical solution that corrodes Si and SiO2 such as hydrofluoric acid or ammonium fluoride.
An etching rate control monitor characterized by etching a cut quartz diaphragm and measuring the frequency of the AT cut quartz diaphragm for monitoring in a chemical solution. 2. An etching rate control monitor for monitor A, wherein one of the electrodes in contact with the monitor AT-cut quartz crystal diaphragm is configured to be movable by the pressure of the flowing chemical solution.
2. The etching rate control monitor according to claim 1, wherein contacting and non-contacting of the electrode with the monitor AT-cut crystal diaphragm is switched by moving the T-cut crystal diaphragm back and forth in a chemical solution. . 3. The monitor AT-cut crystal diaphragm is etched when the movable electrode is not in contact with the monitor AT-cut crystal diaphragm, and the frequency of the monitor AT-cut crystal diaphragm is measured when the movable electrode is in contact. The etching rate management monitor according to claim 2, wherein the etching rate is controlled from the amount of change in frequency. 4. The etching rate control monitor main body is provided with a movable part capable of reciprocating linear motion, and the reciprocating linear motion of the etching rate control monitor and the frequency measurement of the AT-cut crystal diaphragm for monitoring are automatically performed. The etching rate management monitor according to claim 1, 2, or 3.