JPS6326386A - Method for detecting end of etching - Google Patents

Abstract

PURPOSE:To carry out accurate and stable etching independently of exhaustion of an etching soln. when metallic layers on semiconductor substrates are etched, by measuring the concn. of a gas generated so as to detect the end of etching time. CONSTITUTION:A hydrogen detecting sensor 2 is fitted to the lid 5 of a treatment tank 1 filled with an aqueous phosphoric acid soln. 4 as an etching soln. In accordance with the progress of etching, gaseous hydrogen 8 is generated from semiconductor substrates 7 arranged in a holding jig 6 and a hydrogen atmosphere 9 is formed on the surface of the soln. 4. The sensor 2 detects the hydrogen 8 and a hydrogen detector 3 outputs an electric signal corresponding to the concn. of hydrogen. The progress of etching is quantitatively judged by the signal, and the time when a change in the concn. of hydrogen detected with the lapse of time becomes zero can be considered to be the end of etching. Thus, accurate and stable etching can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for detecting the end point of an etching process, and in particular to a method for efficiently detecting the end point of an etching process time for a metal layer deposited on a semiconductor substrate. For the purpose of providing.

[Conventional technology]

Conventionally, the electrodes and wiring parts of semiconductor devices are often formed by vapor-depositing aluminum, and this process involves forming a diffusion layer region in a predetermined amount on a semiconductor substrate, and then depositing an insulating film on top of the diffusion layer region. After opening a predetermined window, metal such as aluminum is vapor-deposited over the entire surface, a photosensitive resist is applied, and a mask with a predetermined circuit is used to expose and develop the unnecessary parts to remove the electrodes and wiring. parts are formed.

As the etching liquid in the above etching process,
Wet etching methods using phosphoric acid (HmPOa) based aqueous solutions are known. A feature of this wet etching method is that a large amount of semiconductor substrates can be processed at one time by etching the semiconductor substrates in units of jigs stored in the etching tank.

In this wet etching method, if the etching solution is fresh, etching can be performed satisfactorily within a preset etching time, but if a large number of semiconductor substrates are processed using the same etching solution, the etching solution will gradually become exhausted. It's getting worse.

[Problem that the invention seeks to solve]

In the conventional etching processing end point detection method described above, the etching speed decreases in proportion to the deterioration of the etching solution, so it is necessary to lengthen the etching processing time according to the degree of deterioration of the etching solution. It becomes extremely difficult to grasp the etching processing time conditions. Furthermore, when immersion etching is performed on semiconductor substrates continuously or intermittently, the area of the semiconductor substrate to be etched and the number of semiconductor substrates to be etched are not specified, so it is very difficult to control the degree of fatigue of the etching solution. Sometimes etching is not performed. In addition, the end point of the etching processing time is determined by humans, and human factors intervene therein.
This method not only requires skill in the work, but also has the drawback that individual differences arise between people.

The conventional method for detecting the end point of etching processing time described above is 1.
While humans grasp the end point visually and intuitively, the present invention focuses on the gas generated during the etching reaction process between the metal layer and acid, and quantitatively measures the progress of the etching reaction based on the gas concentration. It has original content such as detecting the end point of the etching processing time.

[Failure to solve the problem]

The etching process end point detection method of the present invention involves depositing a metal layer on a semiconductor substrate and then etching the metal layer into a predetermined shape by attaching a gas detection sensor to the etching solution filled in a maple treatment tank. , the end point of the etching process time is detected by measuring the gas concentration generated.

〔Example〕

Next, the present invention will be explained with reference to all the drawings.

FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention, FIG. 2 is a sectional view showing the cross section of the processing tank of the first embodiment,
FIG. 3 is a block diagram showing the configuration of a second embodiment of the present invention, and FIG. 4 is a chart showing the relationship between the etched area of aluminum and the concentration of generated hydrogen.

When a semiconductor substrate coated with aluminum AI is immersed in an aqueous solution of phosphoric acid H11PO4, which is an etching solution, and etching is allowed to progress, a reaction occurs: 2Al+2HsPO4→2A/PO4+3I(z), and hydrogen (3H2) is generated. Figure 4 is A
This figure shows the relationship between the etching area of l and the concentration of hydrogen generated.The present invention focuses on the fact that the amount of hydrogen generated is proportional to the amount of reaction of aluminum, that is, the amount of etching, and the amount of hydrogen generated (concentration) The aim is to understand the progress of etching.

This will be explained in detail below using examples.

In the first embodiment shown in FIGS. 1 and 2, hydrogen gas 8 is generated as etching progresses in a phosphoric acid aqueous solution 4 which is an etching solution, and a hydrogen atmosphere 9 is created above the etching solution surface.

The hydrogen detection sensor 2 detects this hydrogen, and the hydrogen detector 3 outputs an electrical signal corresponding to the hydrogen concentration, so it is possible to quantitatively understand the progress of etching, and when the detected concentration is saturated ( In other words, the point at which the time change in detected concentration becomes zero can be determined as the end point of etching.

The second embodiment is similar to the first embodiment as shown in Figure 3.
It is possible to install an alarm device such as a lamp, etc., and a control section 10 is added to audibly and visually grasp the end point of etching, and remote central monitoring is also possible through a telemeter or the like.

〔Effect of the invention〕

As explained above, in the present invention, the hydrogen detection sensor 2 is installed in the processing tank 1, and the end point of the etching processing time can be detected based on the detected concentration of hydrogen generated in the processing tank 1. Appropriate etching processing can be performed at any time regardless of the degree of fatigue, and since it is a quantitative judgment method such as detecting the end point of etching processing from the detected concentration of hydrogen, it is easier to judge than conventional human visual judgment. This makes it possible to perform extremely accurate and stable etching processing.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the first embodiment of the present invention, Fig. 2 is a sectional view showing the cross section of the processing tank of the first embodiment of the invention, and Fig. 3 is the second embodiment. FIG. 4 is a diagram showing the relationship between the etched area of aluminum and the concentration of hydrogen generated. 1... Processing tank, 2... Hydrogen detection sensor, 3... Hydrogen detector, 4... Phosphoric acid aqueous solution, 5... Lid, 6... Storage jig,
7... Semiconductor substrate, 8... Hydrogen gas,
9...Hydrogen atmosphere, 10...Control unit. $ / M 弗 2 Bacteria

Claims (1)

[Claims] A method for detecting the end point of an etching process, characterized in that the end point of an etching process time is detected by measuring the gas concentration generated when a metal layer is deposited on a semiconductor substrate and then etched into a predetermined shape. .