JPH0651914B2 - Thin film etching equipment - Google Patents

Description

The present invention relates to a thin film etching apparatus, particularly on a Si wafer,
The present invention relates to a thin film etching apparatus capable of optimally maintaining the concentration of each component in an etchant when etching an aluminum thin film formed on a glass substrate, a ceramic substrate, or the like.

[Conventional technology]

Conventionally, when etching an aluminum thin film formed on a substrate made of glass or the like using an etchant containing nitric acid and phosphoric acid with water and an additive, the etchant is 50 ° C.
Used by heating in the vicinity. Therefore, the composition of the stored etchant changes due to the evaporation of water due to heating. Therefore, the change in the composition of the etchant is not necessarily proportional to the amount of each component consumed for etching the aluminum thin film, that is, the processing amount of the thin film.

Therefore, the work piece (in this case, an aluminum thin film)
In the method of renewing the etchant with a new composition every time a certain amount of is treated, defective etching of the aluminum thin film often occurs immediately before the renewal. In order to confirm the composition of the etchant, the etching apparatus was set off-line, and it took a long time to analyze the composition, which was not suitable for in-line composition control.

Generally, a method of managing the processing amount of the aluminum thin film and updating the etchant at every fixed processing is adopted. In this case, the etchant tends to be updated to the safe side. Therefore, the amount of the etchant used is larger than the theoretical value, and the number of steps for exchanging the etchant increases, resulting in high cost. Further, since the device is stopped at the time of replacement, the yield is poor and the quality is not favorable.

[Problems to be Solved by the Invention]

Therefore, the object of the present invention is to eliminate the above-mentioned problems, measure the concentration of nitric acid and the concentration of phosphoric acid, which are the etchant components of the aluminum thin film, in-line, set the etchant to a proper concentration, and It is to provide a thin film etching apparatus capable of reducing the number.

[Means for Solving the Problems]

In order to achieve such an object, the present invention provides a first measuring means for measuring the absorbance of an etchant in a thin film etching apparatus for etching a thin film of a workpiece using an etchant containing nitric acid, phosphoric acid and water. A second measuring means for measuring the specific gravity of the etchant; a first supplying means for supplying nitric acid to the etching solution storage tank; a second supplying means for supplying phosphoric acid to the etching solution storage tank; and an etching solution storage The concentration of nitric acid in the etchant was calculated based on the output results of the third supply means for supplying water to the tank and the first measurement means, and the calculated concentration of nitric acid and the second measurement means were used for measurement. Calculate the concentration of phosphoric acid based on specific gravity,
Based on the calculated nitric acid concentration and phosphoric acid concentration, the first
And a control means for controlling the second supply means and the third supply means.

[Action]

The principle of measuring the concentration of nitric acid and the concentration of phosphoric acid according to the present invention will be described. As shown in FIG. 1, nitric acid is not affected by these components in a solution containing phosphoric acid and acetic acid, and the absorbance of ultraviolet rays at a wavelength of around 200 nm is extremely large. The nitric acid concentration can be calculated by measuring the absorbance of ultraviolet rays at a wavelength using an absorptiometer. When the weight% of nitric acid is plotted on the horizontal axis and the absorbance of ultraviolet rays at a wavelength of 200 nm is plotted on the vertical axis, a straight line was obtained up to a weight% of nitric acid of about 5%, as shown in FIG. By using this as a calibration curve, the concentration of nitric acid can be calculated by measuring the absorbance.

The weight% of phosphoric acid is, when nitric acid and phosphoric acid are mixed,
The specific gravity of the mixed solution changes depending on each concentration. When the weight% of phosphoric acid is plotted on the horizontal axis and the specific gravity of the mixed solution is plotted on the vertical axis,
As shown in the figure. If the weight% of nitric acid is constant, the relationship between the weight% of phosphoric acid and the specific gravity is linear. Therefore,
If a calibration curve of the weight% of phosphoric acid and the specific gravity in the weight% of nitric acid in the usable range is prepared in advance, the weight% of phosphoric acid can be calculated by measuring the specific gravity of the mixed solution.

The difference between the concentrations of nitric acid and phosphoric acid calculated in this way and the reference concentrations of nitric acid and phosphoric acid preset according to the etching method are compared, and nitric acid, phosphoric acid and water are supplied according to the difference. Since the amount is controlled, it is possible to stably etch the aluminum thin film while keeping the concentration of each component contained in the etchant within a certain range.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 4 is a schematic diagram showing an embodiment of a thin film etching apparatus to which the present invention is applied.

FIG. 5 is a block diagram showing the basic configuration of the embodiment shown in FIG.

First, the operating method of the apparatus until the concentrations of nitric acid and phosphoric acid are calculated will be described based on FIGS. 4 and 5. The operation method of the entire device will be described later.

The etching liquid 2 containing water containing nitric acid and phosphoric acid as a main component is placed in the etching liquid storage tank 1, heated by a heater 3 and made into an etching liquid having a uniform concentration using a stirrer 4.
The pump 10 sends the etching solution 1 to the etching tank 11, the spray 12 sprays the etching solution 2 onto the aluminum thin film substrate 13 to be processed for etching, and the discharged liquid returns to the etching solution storage tank 1 through the pipe 14.

The control unit 17 performs the following operations according to the control procedure stored in the ROM 17B. The etching liquid 2 collected by the sample collection pump 5 is sent to the flow cell 7. An ultraviolet light source 8 such as a combination of a deuterium lamp and a monochromator irradiates the etching liquid in the flow cell with ultraviolet light having a wavelength of about 200 nm, and the ultraviolet light detector 9 determines the amount of transmitted light. This transmitted light amount data is sent to the control unit 17. On the other hand, the etching solution sent by the pump 10 is sent to the etching tank 11 and at the same time, sent to the hydrometer cell 16. The flow rate of the etching solution can be freely adjusted by the valve 15.
Specific gravity data of the etching solution obtained by the specific gravity cell 16 is sent to the control unit 17.

The CPU 17A calculates the absorbance from the amount of transmitted light, and then calculates the concentration of nitric acid based on the table of the RAM 17C that stores the data on the absorbance and the nitric acid concentration.

Next, based on the table of RAM17C that stores the data of specific gravity that changes according to the concentration of nitric acid and the concentration of phosphoric acid,
CPU17A calculates the concentration of phosphoric acid.

When the concentrations of nitric acid and phosphoric acid are calculated in this way, CPU17A
Compares the difference with the reference concentration stored in the control unit 17, operates the nitric acid supply pump 19, the phosphoric acid supply pump 21 and the solenoid valve 23 according to the difference amount, and instructs the operation time.

Here, the reference density is different from RAM17C or 17B
Can be stored in.

FIG. 6 is a flow chart showing an example of the processing procedure of the embodiment of the present invention. In steps S1 to S3, the etchant is sampled and the concentrations of nitric acid and phosphoric acid are calculated. The details of this processing procedure have already been described, and will be omitted here.

In step S4, the nitric acid concentration calculated in step S2 is compared with the reference nitric acid concentration of the etchant to determine whether or not the nitric acid concentration is insufficient. If it is determined that the concentration of nitric acid is insufficient, the process proceeds to step S5 to calculate the amount of insufficiency, and based on the result, the nitric acid supply tank 18 passes the nitric acid supply pump 19 to store a predetermined amount of nitric acid in the etching solution storage tank 1. Nitric acid is supplied over a predetermined period of time.

If the concentration of nitric acid is not insufficient in step S4, the process proceeds to step S6, the concentration of phosphoric acid calculated in step S3 is compared with the standard phosphoric acid concentration of the etchant, and the concentration of phosphoric acid is insufficient or excessive. Or the standard concentration is determined. If the concentration of phosphoric acid is excessive, the process proceeds to step S7, the solenoid valve 23 of the pure water pipe 22 is opened, and when a predetermined amount of pure water is supplied, the solenoid valve is closed. If the concentration of phosphoric acid is insufficient, the process proceeds to step S8, the insufficient amount of phosphoric acid is calculated, and based on the result, a predetermined amount of phosphoric acid is supplied from the phosphoric acid supply tank 20 to the etching solution storage tank 1 through the phosphoric acid pump 21.

If the supply rates of nitric acid, phosphoric acid and water by the nitric acid supply pump 19, the phosphoric acid supply pump 21 and the solenoid valve 23 are constant, the supply amount is controlled by controlling the operation time of them to keep the etchant at a predetermined concentration. be able to.

〔The invention's effect〕

As described above, according to the present invention, the etchant concentration can be controlled in-line, the nitric acid and phosphoric acid concentrations in the etching solution are stabilized, and the etching quality is ensured and the etching solution life is extended. Therefore, the number of stoppages of the apparatus due to the exchange of the etching liquid is drastically reduced, and a large cost reduction including the reduction of the amount of chemicals used can be achieved.

[Brief description of drawings]

Fig. 1 is a characteristic diagram showing the change of the absorbance of nitric acid with respect to the ultraviolet wavelength, Fig. 2 is a characteristic diagram showing the change of the relation between the absorbance of nitric acid and the concentration of nitric acid, and Fig. 3 is the phosphoric acid concentration according to the concentration of nitric acid. FIG. 4 is a characteristic diagram showing the relationship with the specific gravity of the etching solution, FIG. 4 is a schematic diagram of a thin film etching apparatus to which the present invention is applied, FIG. 5 is a block diagram of an embodiment of the present invention, and FIG. 6 is an embodiment of the present invention. 6 is a flowchart showing an example of the processing procedure of FIG. 1 ... Etching solution storage tank, 2 ... Etching solution, 3 ... Heater, 4 ... Stirrer, 5 ... Sampling pump, 6 ... Nitric acid absorbance measurement section, 7 ... Flow cell, 8 ... Ultraviolet light source , 9 ... UV detector, 10 ... Pump, 11 ... Etching tank, 12 ... Spray, 13 ... Aluminum thin film substrate, 14 ... Piping, 15 ... Valve, 16 ... Densitometer cell, 17 …… control part, 18 …… nitric acid supply tank, 19 …… nitric acid supply pump, 20 …… phosphoric acid supply tank, 21 …… phosphoric acid supply pump, 22 …… piping, 23 …… solenoid valve.

Front page continued (72) Inventor Hisako Mogi 3461 Nanashiki, Kamisato-cho, Kodama-gun, Saitama Canon Inc. (72) Inventor Keishi Dangami 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. In-house (72) Inventor Hitoshi Horie 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP 62-103383 (JP, A)

Claims (1)

[Claims] 1. A thin film etching apparatus for etching a thin film of a workpiece using an etchant containing nitric acid, phosphoric acid and water, wherein a first measuring means for measuring the absorbance of the etchant and a specific gravity of the etchant are measured. A second measuring unit for supplying nitric acid to the etching solution storage tank, a second supplying means for supplying phosphoric acid to the etching solution storage tank, and a second supply means for supplying water to the etching solution storage tank. No. 3 supply means, and the concentration of nitric acid in the etchant is calculated based on the output result of the first measuring means, and the calculated concentration of nitric acid and the second concentration are calculated.
The concentration of phosphoric acid is calculated on the basis of the specific gravity measured by the measuring means, and the first supply means, the second supply means, and the third supply means are calculated on the basis of the calculated nitric acid concentration and phosphoric acid concentration. A thin film etching apparatus comprising: a control unit that controls a supply unit.